OPHTHALMOLOGY

Abnormalities of the ocular structures produce visual dysfunction, altered appearance, pain, or systemic symptoms. Many persons believe vision to be the most important and comprehensive of the senses. Decreased visual acuity can indicate a blinding eye disease that can be controlled with restoration of vision, a systemic disease that can endanger life if not detected and managed, a tumor or other disorder of the central nervous system that can threaten vision and life, or a simple refractive error, correction of which simplifies the patient’s life. Ocular symptoms bring the patient rapidly to the physician because the eyes are the focus of a patient’s perception, and alterations in these structures usually are not ignored.
The otolaryngologist–head and neck surgeon often joins the ophthalmologist in a team approach to care for a patient with congenital or acquired abnormalities of the orbit and adnexa and periorbital structures. Appreciation of the fundamental concepts of vision, ocular anatomy and physiology, and local and systemic disorders is essential to direct care or assist in caring for a patient with ophthalmic problems. Consultation with an ophthalmologist is mandatory for most disorders and can be quite helpful for most patients. This chapter highlights the most common disorders seen by otolaryngologist–head and neck surgeons and explains what often are considered to be complicated and sophisticated problems. Also discussed are the best imaging studies for the diagnosis of ophthalmologic and orbital disorders, trauma, and tumors.
THE EYE EXAMINATION
The three reasons for performing an ocular examination are as follows:

1.Presenting symptoms clearly related to ocular structures, such as pain in the eye and halos around lights

2.Presymptomatic screening to detect controllable eye disease, such as amblyopia and glaucoma

3.Evaluation or diagnosis of systemic disease mirrored in the eye, such as retinopathy in diabetes and tuberculous choroiditis with fever of undetermined origin
With these goals in mind, it is obvious that testing the function of the visual system and looking at the eyes should be part of any complete medical examination.
An eye examination begins with obtaining a history related to the symptoms. Relevant areas are chronology, eye history, family history, concurrent systemic diseases, present use of medications, and existence of allergies. Ocular symptoms usually can be classified into three groups—altered visual function, abnormal sensation, or altered appearance. Abnormalities in visual functioning generally reduce vision, cause superimposed visual phenomena, or produce diplopia. Abnormal sensation in or around the eye can take many forms—deep pain, which signifies intraocular or orbital inflammation; foreign-body pain related to trauma; superficial pain of mild conjunctivitis; vague discomfort known as asthenopia, or eyestrain, with prolonged, intensive use of the eyes; headache related to neurologic disease or tension; or photophobia or ocular pain with exposure to light, most commonly related to corneal abnormalities (1). Altered appearance usually refers to eyelid abnormalities, orbital deformities, motility disturbances, or redness of the eyeball.
Visual Acuity
An eye examination begins with determining the visual acuity of each eye with the other eye completely covered. Although measurements are obtained at distance and near, with and without refraction (glasses), the most important determination of general eye condition is the best-corrected-distance visual acuity, usually assessed with a Snellen chart. Examination of children often requires pictures or individual E charts. Each line on the chart is meant to be read by a person with normal sight at 20 feet (6 m). The largest letter should be seen at 200 feet (60 m) by a person with normal vision. If a patient can see that letter at a distance of 20 feet and is unable to see any of the smaller letters, vision is 20/200. If the line read by a person with normal sight can be seen at 20 feet, and the patient is 20 feet from the chart, the vision is 20/20. If the patient is unable to read the largest letter on the chart, the distance at which he or she can count fingers accurately is recorded. If the patient cannot count fingers, the distance at which hand movements are perceived is determined. If this is not possible, whether the patient can perceive light is documented. Table 10.1 compares visual acuity with visual ability or disability. Vision is not a true fraction. In other words, 20/40 vision does not mean 50% of normal vision but that the patient can see at 20 feet what a person with normal sight can see at 40 feet (12 m). If the patient can see the 20/20 line wearing glasses, his or her functional vision is probably just as good as that of someone who sees the line without glasses.
The ophthalmologist uses the process of refraction to determine the refractive error or the lenses needed for the eye. The need for refraction is determined with a pinhole test. The patient views a chart through a 1-mm pinhole, which reduces the blur of the image on the retina and appreciably increases visual acuity if it is decreased owing to a refractive problem. This test helps to rule out retinal or optic nerve dysfunction as a cause of decreased vision. Measurement of best corrected visual acuity is an important concept. Often patients say they are “blind” without their glasses. They should be informed that vision can be physiologically abnormal without pathologic consequence.
Peripheral vision, or side vision, can be evaluated with visual field testing. This test can be performed with various instruments, but it is commonly performed with the confrontation technique. The patient is asked to fix on the examiner’s nose with one eye and to cover the other eye. A test object or finger is brought in from the side until the patient reports it is being seen. The visual field is approximately 90 degrees on the same side but only 50 degrees on the opposite side of testing. Abnormalities of peripheral vision often are detected only through examination because patients report loss of central vision, but loss of peripheral vision is not easily detected. Performing this test for each eye is a good screening method for many neurologic diseases.
External Inspection and Pupil Examination
Inspection of the external eye structures includes the eyelids, eyelashes, lacrimal apparatus, cornea, conjunctiva and sclera, anterior chamber, and iris, as well as the general symmetry of the face and orbits. Much information can be obtained with this examination, which often reveals the diagnosis. Particular notice should be taken of abnormal alignment of the eyelids (ptosis or lid retraction), the position of the eyelids against the globe (entropion or ectropion), and abnormal direction of the eyelashes (trichiasis). Swelling in the medial canthal area can indicate abnormal lacrimal drainage. Proptosis always is an important finding (Fig. 10.1). The causative factor may indicate orbital or systemic disease. Specific abnormalities in the color and contour of the conjunctiva, cornea, and sclera are discussed later with red eye. Of particular importance is estimation of the depth of the anterior chamber in detecting an important form of glaucoma. This test can be performed with side-illumination with a penlight. If the anterior chamber is of normal depth, the entire surface of the iris is illuminated. If the anterior chamber is shallow, the iris on the opposite side of the pupil is in shadow.
Examination of the iris usually centers on assessing the pupillary response. When light is shone into the eye a normal pupil constricts and then redilates after the stimulus is removed. This is the direct light reflex. The fellow pupil constricts also, and this is known as the consensual light reflex. These reflexes should be brisk and approximately equal. Pupillary constriction also is part of the near-vision complex associated with the process of accommodation. If the pupil reacts to accommodation but not to light, it is the classic Argyll Robertson pupil, often associated with syphilis. Marcus Gunn pupil is an important physical sign in an evaluation for neurologic disease. It is elicited with the swinging flashlight test. Light is shone in one pupil for 2 or 3 seconds and then rapidly switched to the second eye. There should be prompt constriction if the pupil is normal. If there is optic nerve disease or injury, the pupil gradually dilates, indicating a decreased direct light reflex. This sign is positive early in the disease, when vision still is 20/30 or better. Abnormal pupillary reaction in any form generally indicates serious disease. For the physician, normal visual acuity and normal pupillary responses are comforting findings in evaluating eye problems.
Motility
Six muscles surrounding each eye are responsible for ocular motility. Several terms are used to describe various eye movements. The movement of one eye from one position to another is called duction. The simultaneous movement of both eyes from the primary, straight-ahead position to a secondary position (up, down, right, left) is called version. Vergence is the term applied to simultaneous rotation of both eyes inward (convergence) or outward (divergence). Evaluation of the extraocular muscle function is begun with general inspection to find any gross deviation of either eye (heterotropia). The patient is asked to look up, down, right, and left to reveal whether the deviation is the same in all fields of gaze (concomitant) or varies (nonconcomitant and usually neurologically significant) (Fig. 10.2). During these gaze movements, involuntary eye jerks, called nystagmus, also can be detected.
The flashlight used to evaluate pupillary reflexes also can be used to assess the corneal light reflex. The light should be symmetrically reflected in each pupil. If there is deviation, the degree of abnormality can be estimated by the asymmetry of the light reflex.
The cover test is used to evaluate motility. The patient is instructed to fix on an object. If both eyes appear straight (orthotropia), cover either one. If under cover the eye deviates, phoria, or latent deviation that becomes evident only when vision is interrupted, has been elicited. Usually the eye resumes fixation when uncovered. If one eye is obviously deviated, the straight-ahead eye is covered. If the deviated eye rapidly moves to resume fixation, it most likely has good visual potential. The deviation can be eso (inward), exo (outward), hyper (upward), or hypo (downward).
Intraocular Pressure
Measurement of intraocular pressure (IOP) should be a part of every general physical examination. The examiner can estimate IOP digitally by placing the tips of the index fingers on the patient’s closed eyelids. All but gross abnormalities remain undetected when this technique is used. Tonometry is estimation of IOP with an instrument. It can be performed with an indentation technique or an applanation technique. The former is used in the general screening process and performed with a Schiotz tonometer. With the patient in a recumbent position, a drop of topical anesthetic is instilled into each eye. The patient is instructed to look straight ahead with both eyes open. Assistance in holding the eyelids open, with pressure on the orbital bones only, may be needed. The plunger is gently placed on the center of the patient’s cornea, and the corresponding scale reading is recorded. The test should require only 1 to 2 seconds of contact with the cornea. Normal IOP usually is 15 ± 3 mm Hg, with an upper limit of 22 to 23 mm Hg.
Ophthalmoscopy
The final part of a general eye examination is ophthalmoscopy. It is used to evaluate the internal structures of the eye, primarily the retina, retinal blood vessels, and optic nerve. A direct ophthalmoscope is used for this examination and provides an upright ×15 magnified image. There is great limitation of the field of view and the information obtained if the examiner is viewing through a small pupil. A 3-mm pupil gives only a 4-degree field of view, but a 7-mm pupil allows a 30-degree field of view. Therefore, routine dilation of the pupils with 0.5% or 1% tropicamide or 2.5% phenylephrine is recommended with the following exceptions: known narrow-angle glaucoma, neurologic or neurosurgical observation, and some types of intraocular lens implants after cataract surgery. In rare instances, dilation of the pupil can precipitate an attack of acute angle-closure glaucoma that was previously unsuspected. This should not be considered a contraindication. Because this form of glaucoma is rare and can be managed effectively, the benefits of improved ophthalmoscopy through dilated pupils outweigh the risks.
The examiner holds the ophthalmoscope in the right hand and uses the right eye to examine the patient’s right eye. With the pupil dilated, reflected light from the ocular fundus produces a clear red reflex when viewed through the ophthalmoscope with a +6 lens at a distance of approximately 1 foot (0.3 m). Any alteration in the red reflex indicates abnormality in one of the optical structures of the eye and is always important. The patient’s eye is then approached as closely as possible as the power of the lens in the ophthalmoscope is reduced until the optic disk comes into focus. The nerve head should be evaluated for color, sharpness of margins, and appearance of the central depressed area known as the cup. Systematic examination of the retinal vessels and background then is performed. The macular region deserves special attention for patients with vision loss.
VISUAL ABNORMALITIES
Physiologically Decreased Vision
Refractive Error
A common cause of poor vision is refractive error or change in refractive error. Patients with myopia (nearsightedness) have an eye that is too long for its refractive system. This typically young patient reports not being able to see the blackboard and having to sit in the front of the schoolroom. Simple prescription of concave lenses usually restores visual acuity to normal. Persons with hyperopia, or farsightedness, have an eye that is too short and need simple convex lenses to bring near objects into focus. Aphakia is a special form of hyperopia in which the refractive power of the eye is too weak because of removal of the lens. Astigmatism is nonspheric curvature of the cornea and is extremely common with any refractive error.
Refractive visual surgery, also known as refractive or radial keratotomy, is becoming increasingly common among patients with myopia. Patients seeking elective reduction of physiologic myopia usually are treated with a protocol of therapy that involves performing radial incisions in the cornea to alter its curvature. Newer technology such as manufacture of finer, thinner blades, more accurate blade placement, and computed topography of the corneal surface, have helped to reduce complications and produce more consistent results, including a decreased trend toward a hyperopic drift with time (2). Some patients need additional incisions, called enhancements.
Presbyopia
Presbyopia is the term used to describe the clinical need for reading glasses or bifocals as the patient enters the fourth and fifth decade of life. The crystalline lens hardens with age and becomes less elastic, decreasing ability to accommodate or focus for near vision. This is a normal physiologic mechanism and should not be considered a sign of disease.
Pathologically Decreased Vision
Gradual Loss of Vision
In evaluating reduced vision in pathologic terms, best corrected visual acuity must be considered to eliminate the physiologic abnormalities. The three most common causes of gradual loss of vision are cataract, senile macular degeneration, and glaucoma.
Cataract formation, the loss of transparency of the crystalline lens, is common. Increased density of the lens fibers and changes in protein content occur almost without exception to some degree in every person with increasing age; however, many times the loss of transparency is so marked that visual function is seriously hampered. The term cataract usually is reserved for the latter situation. Cataract formation usually is evolutional, but it occasionally has a specific cause, such as galactosemia, galactokinase deficiency, diabetic ketoacidosis, or trauma. If one of these metabolic abnormalities can be corrected early in the course of cataract formation, the lens opacity can be reversed; however, often there is no known way to prevent or reverse lens changes due to cataract. Treatment is surgical removal of the cataract. The need for surgery usually depends on the patient’s visual requirements and desires. In rare instances, the cataract damages the eye because of high pressure from rapid swelling and may have to be removed for other than optical reasons.
The operation usually is performed by means of opening the anterior capsule and extracting the lens material. The posterior capsule is left intact (extracapsular technique or phacoemulsification). After a person is aphakic, the optical power of the lens must be replaced to provide focusing ability. The patient can be fitted with spectacles or contact lenses after the eye has healed or can have an intraocular lens implanted during the surgical procedure. It is comforting to inform patients that cataract surgery is one of the most successful operations performed.
A second common cause of gradual progressive decrease in vision among older persons is senile macular degeneration. The cause of this condition is unknown, but it may be related to a decrease in the blood supply to the macular area associated with hardening of the arteries in the back of the eye, which begins as a pigmentary disturbance in the macula and usually progresses slowly but steadily with increased scarring and often hemorrhage into the tissues. The disease is bilateral but usually asymmetric. There is no effective treatment, and normal use of the eyes, as for sewing and reading, does not accelerate the process. Patients should be assured that macular degeneration is not a blinding disease because the peripheral vision is not disturbed. Patients with this condition always are able to move around unaided, even though their useful reading vision may be markedly decreased. Unlike the two aforementioned visually disabling conditions, glaucoma characteristically produces a decrease in peripheral visual ability, but good reading vision is maintained until late in the disease.
Sudden Loss of Vision
Sudden loss of vision is a dramatic event and usually represents an identifiable pathologic process (3). Some processes can be controlled to allow restoration of vision, and others produce permanent loss of visual function. Vitreous hemorrhage unrelated to trauma can occur in advanced diabetes mellitus as a result of disease of the retinal blood vessels. The vitreous haze prevents complete examination of the retinal blood vessels, and the offending area often remains unidentified until the blood is reabsorbed. It can take months or years for the vitreous to clear in a relatively young person, producing marked disability.
Central retinal arterial occlusion causes total and permanent loss of vision and abolition of the direct pupillary reaction to light. At ophthalmoscopic examination, the fundus appears pale with development of a cherry red spot in the macula. The spot is caused by continued choroidal blood supply to the macula and the contrasting loss of circulation to the rest of the retina. The retinal arteries are narrow and may have fragmented blood columns (boxcar sign). The cause usually is an embolus from diseased carotid arteries, abnormal heart valves, or thrombosis from long-standing atherosclerosis. In rare instances, central retinal arterial occlusion is a vasospastic event associated with an inflammatory disease. Treatment aimed at relieving the obstruction through vasodilation, such as medication, ocular massage, and inhalation of 5% carbon dioxide and 95% oxygen, usually is unsuccessful. Attacks of amaurosis fugax and central or branch retinal artery occlusion have been shown to be related to internal carotid artery stenosis of more than 50% diameter reduction and occlusion (3). There appears to be an increase in ulcerated free plaque surfaces, which might lead to arterioarterial embolization. Duplex ultrasonography and continuous-wave Doppler ultrasonography can be used for noninvasive diagnosis; however, the magnetic resonance angiography is rapidly gaining favor as a sensitive screening test for carotid stenosis.
Central retinal venous occlusion is more common and less dramatic than arterial occlusion, and it has a markedly better prognosis. At ophthalmoscopic examination, the fundus has a dramatic appearance, as if the entire view has been splattered with blood, and the observed vessels appear engorged and tortuous. Much of the hemorrhage clears with time, vision returns, and late complications of retinal anoxia are managed by the ophthalmologist.
Retinal detachment occurs among approximately 1 in 1,000 persons. It is much more common among persons with high myopia (those with large eyes), after cataract surgery (1 of 100), and in association with trauma. The mode of visual loss varies. The patient commonly reports a shadow or curtain in front of the eye, ascending or descending, depending on the direction of the separation. There may be associated flashing lights and floaters as the retinal structure is disturbed. After the macula becomes detached, central vision is abruptly lost. At ophthalmoscopy, the detached retina is found to be pale and wrinkled and to project forward into the vitreous, often to the point at which it may not be focused with the attached area. Surgical reattachment of the retina is successful in 60% to 80% of cases, but return of vision depends on time and avoidance of late surgical complications.
Optic nerve compromise, whether in the form of ischemia or inflammation, is not as common as retinal detachment, but it is equally dramatic and important. A patient older than 55 years who has sudden loss of vision and perhaps has vague arthritic symptoms, low-grade fever, or temporal scalp tenderness, should have erythrocyte sedimentation rate measured. If the rate is elevated, the diagnosis is most likely temporal arteritis, and the fellow eye is at risk of parallel visual loss. Systemic glucocorticoid therapy should be initiated to prevent the onset of the inflammation in the other eye. For a younger person, if loss of vision is associated with edema of the optic disk, the diagnosis is probably optic neuritis (Fig. 10.3). The prognosis for return of vision is good, but the possibility that a demyelinating disorder such as multiple sclerosis is present must be considered.
Sometimes the report of sudden loss of vision is unfounded. This usually occurs when an older patient suddenly “discovers” a loss of sight that has existed for some time. Chance occlusion of the seeing eye reveals the visual loss, which is erroneously reported as being acute. The report of sudden loss of vision also is associated with hysteria or malingering and the desire for secondary gain.
Transient Loss of Vision
Transient loss of vision can be part of the aura of migraine or a consequence of chronic papilledema. Visual blackouts are common in vertebral-basilar insufficiency after at least 80% narrowing of this vascular system from atherosclerosis. These blackouts are ominous because repeated attacks often are not transient and can be permanent. Abnormalities in the carotid system can cause temporary, usually unilateral, loss of vision (amaurosis fugax). There may be associated cerebral symptoms and hemiparesis. Because 15% to 20% of these patients later have a stroke, they need a complete vascular evaluation.
Diplopia
Diplopia is another symptom of visual abnormality. Physiologic diplopia is a normal phenomenon in which objects not within the area of fixation are seen as double. This is easily seen when one looks at a near object with attention directed at a distant object, which then appears double. Usually this does not impinge on consciousness. Pathologic diplopia is a cardinal sign of weakness of one or more of the extraocular muscles and usually is caused by neurologic disease, trauma (Fig. 10.4), or diabetes mellitus. Diplopia also can occur with normal muscles if the globe is displaced, as in orbital disease or tumors that prevent proper alignment of visual stimuli. Monocular diplopia (that which does not go away when one eye is covered) is rare and usually due to splitting of light rays by an irregularity in the cornea, certain types of cataracts, or misaligned photoreceptors in the macula. More commonly, monocular diplopia is a neurotic or functional disorder.
RED EYE
The otolaryngologist–head and neck surgeon occasionally encounters a patient with a red eye, possibly in conjunction with another disease or after treatment. The condition causing the red eye often is a simple disorder, such as blepharitis or infectious conjunctivitis, that resolves spontaneously or is easily managed by the physician. In some instances, however, the condition causing the red eye is a more serious disorder, such as intraocular inflammation or acute glaucoma. A patient with one of these vision-threatening conditions needs the immediate attention of an ophthalmologist. The primary physician must be able to differentiate minor irritation and a serious eye disease. Red eye can be caused by infection, inflammation, or allergic reaction of the eyelid, adnexal structures, or intraocular tissues. Other important causes are acute glaucoma, trauma, and various systemic diseases.
Eyelid Abnormalities and Blepharitis
Many common disorders affect the eyelids. A sty (hordeolum) is an acute infection of one of the glands in the eyelid, similar to a boil or furuncle of other areas of the skin. The patient typically has a red eyelid with moderate tenderness and swelling in the involved area. There may be associated redness of the conjunctiva. These lesions usually are self-limiting and drain spontaneously, or the patient can be treated with warm compresses and topical antibiotics. A chronic lipogranulomatous structure known as a chalazion can be caused by an abnormality in the meibomian glands of the eyelid. If the patient requests treatment, this lesion usually necessitates surgical incision and drainage. Diffuse inflammation or infection of the eyelids is known as blepharitis. It characteristically has two forms. The first is a chronic staphylococcal infection of the glands surrounding the eyelashes. Abnormal oil secretions from these glands irritate the eye and cause redness and sometimes small whitish infiltrates in the cornea near the limbus. The other form is blepharitis associated with typical seborrhea of the scalp, eyelashes, and eyebrows. These conditions tend to cause swelling of the eyelids, a moderate amount of erythema of the lid margins, and mild to moderate conjunctival injection. The patient describes having irritated eyes with scaling or crusting of the eyelashes. Treatment is long term and is directed at eradicating the contaminated flora, controlling the scalp seborrhea, and cleaning the lids. Anatomic abnormalities of the eyelids, such as entropion with irritation due to misdirected eyelashes or ectropion, which causes poor tear function and corneal exposure, can be eliminated as the cause of redness by simple observation.
Conjunctivitis, Episcleritis, and Scleritis
Conjunctivitis is inflammation of the mucous membrane covering the globe and lining the inner part of the eyelids. Conjunctivitis usually is infectious or allergic. Viral conjunctivitis caused by the adenovirus group is the common pink eye for which children are sent home from school. Symptoms are mild, with only diffuse redness of the conjunctiva, minimal clear discharge, and perhaps a tender preauricular node or associated pharyngitis. The condition is generally self-limited, but it is highly contagious in its early stages. Bacterial conjunctivitis is commonly caused by strains of Staphylococcus, Diplococcus, or Haemophilus. The patient has mild symptoms of grittiness and photophobia. The most characteristic finding is that the lids stick together overnight because of a mucopurulent discharge. If acute, copious purulence is present, the offending agent may be Neisseria gonorrhoeae, and further systemic investigation should be performed. Routine culturing is not necessary because there usually is a prompt response to broad-spectrum topical antibiotics. If symptoms persist for more than 2 weeks, an alternative diagnosis should be entertained.
Allergic conjunctivitis can occur in response to topical medications, cosmetics, aerosols, or as part of the hay fever complex. The first exposure can be dramatic with severe itching and profuse watering associated with marked edema of the conjunctiva (chemosis), and the eyelids may be swollen shut, similar to the reaction of an insect sting. This condition can be unilateral or bilateral. It usually is managed with cold compresses and perhaps topical or systemic antihistamines after elimination of the offending agent, if possible.
Deep to the conjunctiva are the episcleral tissues and sclera. If the inflammation is not superficial, the patient reports deep pain, and the erythema appears dark red or purplish, episcleritis or scleritis should be considered. Episcleritis usually is an isolated patch of inflammation without sequelae. In contrast, more than 50% of cases of scleritis are associated with systemic disease, usually of a rheumatic nature. Recurrent inflammation of a pterygium can produce a discrete area of conjunctivitis.
Keratitis
Keratitis is inflammation of the cornea. Although often mild, this condition can be dangerous and threaten vision. Disruption of and infiltrates in the cornea always produce pain, photophobia, and decreased vision. The conjunctiva is injected, and iritis may be present. Keratitis caused by the herpes simplex virus is an important ocular condition. The infection typically forms a branching dendritic pattern on the cornea. If recognized before corneal scarring occurs, the infection can be controlled with any of several antiviral medications. Iridocyclitis can be caused by the herpes zoster virus, which affects the ciliary body and the skin of the tip of the nose along the nasociliary nerve. Bacterial, viral, or fungal corneal ulcers are serious conditions that necessitate intense therapy and cause prolonged morbidity. Ulcers caused by Pseudomonas organisms sometimes progress to perforation in 24 to 48 hours despite intense therapy. Because any disruption of the corneal epithelium can allow entrance of organisms, infection must be considered, particularly after trauma and in the treatment of debilitated patients with a poor tear film.
Iritis and Iridocyclitis
The iris and ciliary body anatomically constitute the anterior uveal tract. Uveitis is a general term that describes inflammation of the iris (iritis), ciliary body (cyclitis), or most commonly both (iridocyclitis). Acute iridocyclitis causes severe aching of the eye, intense photophobia, tearing, and in many instances, decreased vision. The redness usually is most evident around the limbus over the ciliary body (ciliary flush), unlike the diffuse redness of conjunctivitis. The pupil is constricted owing to direct irritation of the iris sphincter muscle, and the anterior chamber fluid is cloudy owing to the presence of inflammatory exudate and cells entering the aqueous. Severe secondary glaucoma can occur if clumps of this debris block the filtration angle. In most acute cases of iritis not associated with severe corneal disease or trauma, the cause is unknown but the condition may be associated with tuberculosis, sarcoidosis, ankylosing spondylitis, rheumatic diseases, gonorrhea, or Reiter syndrome.
The objective in managing iritis is suppressing inflammation and easing pain due to spasm in the ciliary body. This is achieved with topical glucocorticoids and a cycloplegic agent. Systemic analgesics often are needed. Herpes zoster can involve the iris and produce marked iridocyclitis. This appears to be more common with involvement of the external nasal nerve, a branch of the ethmoid nerve, which is related to the innervation of the iris. The herald sign of this disorder is a painful eye, usually red, which is associated with herpetic eruption along the ipsilateral lower half of the nose. This is considered an urgent ophthalmologic condition and should be managed by an ophthalmologist. Herpes zoster ophthalmicus is a frequent first manifestation of acquired immunodeficiency syndrome (AIDS) or human immunodeficiency virus infection (4,5). Acute retinal necrosis also may be present. Herpetic lesions of the face have the highest association with AIDS. An underlying immunodeficiency syndrome should be suspected and investigated when herpetic lesions involve the eye.
Miscellaneous Causes
Several other important pathologic processes must be considered in the differential diagnosis of red eye. If there is a history of trauma, a foreign body or abrasion must be considered. Patients with acute angle-closure glaucoma have severe pain, a cloudy cornea, a dilated and sluggish pupil, a marked decrease in vision, and an increase in IOP. Dacryocystitis (inflammation of the lacrimal sac) is characterized by painful swelling and erythema in the medial canthal area, which can cause systemic symptoms with fever and marked leukocytosis. Treatment consists of heat, antibiotics, and drainage, if needed. Orbital cellulitis is a serious condition and can be life threatening among children and persons with suppressed immune function (Fig. 10.5). If ocular motility is limited, attention must be given to monitoring pupillary reaction and observation for optic nerve compression as an ominous sign of visual loss. A red eye associated with sudden proptosis is a sign of serious orbital or cavernous sinus disease (Fig. 10.6). Table 10.2 and Table 10.3 summarize the signs and symptoms helpful in the differential diagnosis of red eye and the indications for referral (Table 10.2 and Table 10.3).
Guidelines for Treatment
Adult patients with bacterial conjunctivitis are treated with antibiotic drops rather than ointment except at bedtime. Children are treated with ointment. A 10% to 15% solution of sodium sulfacetamide given four times daily for 4 days is recommended unless the patient has a sulfa allergy. Patients with sulfa allergies can be treated with tobramycin, gentamicin sulfate, or another topical solution may be substituted. Neomycin compounds are to be avoided because of the high incidence of allergy and contact dermatitis. Cycloplegic eyedrops, such as atropine, homatropine, or cyclopentolate hydrochloride, are used to reduce ciliary spasm to decrease pain. If these agents are prescribed, the patient must be warned of the side effects of decreased near vision and pupillary dilation. Topical anesthetic drops should be used for diagnosis only. Prolonged use can slow corneal healing and cause severe allergic reactions. Because these agents eliminate corneal sensation, the protective blink reflex is retarded, opening the door to dehydration and injury.
Administration of topical glucocorticoids should be reserved for the ophthalmologist. If the condition is one best managed with glucocorticoids, the patient should be examined and treated by a specialist. Glucocorticoid eyedrops make the patient feel better, but in conditions such as herpes simplex, keratitis, or fungal corneal ulcers, symptoms may decrease while the cornea is melting away and threatened by perforation. Several weeks of use of glucocorticoids can cause cataracts and elevation in IOP, which leads to typical glaucomatous optic nerve damage and visual loss.
OCULAR TRAUMA
When a patient sustains ocular trauma, the most important task is to differentiate a serious, potentially blinding problem and less serious problems. The care rendered by the first physician to examine a patient with ocular trauma frequently determines the visual outcome. A few minutes can make the difference between saving or losing sight. For these reasons, all patients with ocular symptoms should be treated according to an organized plan.
History and Examination
As in all specialties of medicine, a patient’s symptoms and history provide clues about what the examination may reveal. A tearing or scratchy sensation usually is trivial, but a chemical burn or penetrating injury can be visually devastating. The physician should always be cautious. A trivial or outwardly minor injury can be accompanied by a small perforation of the globe or penetration of a minute foreign body into the eye. The likelihood of perforation should always be borne in mind during examinations, regardless of how minor the injury may appear. After the most careful examination, if there is the slightest doubt about the presence of perforation, prompt referral to an ophthalmologist is recommended.
A detailed history, as would be appropriate in outpatient care or in evaluating a chronic problem, is not indicated or necessary in an emergency. Some issues are important, however. How did the trauma happen? For example, did something blow into the eye while the patient was walking outside, or was the patient grinding steel and struck by part of the machinery? When did the trauma happen? The chronology of events is extremely important. Also essential is the history of the eye. When a patient has a decrease in visual acuity, it is important to know whether that eye has had poor vision in the past or this is an acute change. Old trauma must be differentiated from the effects of a new injury.
After a history is obtained, careful inspection of the structures involved should be undertaken with documentation of visual acuity. This is important from a medicolegal point of view, and it is helpful in ascertaining the extent of the injury and monitoring of treatment. If a patient does not have his or her glasses for the examination if they were broken in the trauma, use of the pinhole test is important in evaluating vision to obtain the best possible acuity.
Orbital Trauma
Trauma to the orbit can be superficial, resulting in only ecchymosis of the lid (black eye), or it can be extensive, involving the bony walls and intraocular structures. Plain radiographs of the orbits are of limited value after orbital trauma except for localizing embedded metallic foreign bodies. Computed tomography (CT), both axial and coronal, provides the best information about osseous components of trauma. Soft-tissue window algorithms can be used to assess hematoma formation, orbital fat prolapse, and other damage. Evidence of orbital emphysema on CT scans usually is a result of orbital continuity with fractured sinuses. Although the air usually resorbs spontaneously, increased IOP and retinal artery compression can occur (6). Evaluation of extraocular muscle function can show soft-tissue entrapment in an orbital floor fracture. Subcutaneous emphysema in the eyelids can indicate a medial wall fracture into the ethmoid air cells. Visual acuity should be documented. A decrease may indicate ocular damage. More than 30% of injuries to the bony orbit are associated with intraocular injury (7,8,9 and 10). If the injury is superficial or if the findings at radiography, motility studies, visual acuity testing, and globe inspection are normal, the patient can be reassured. Otherwise, a referral can be made for surgical care or further ocular examination.
Eyelid Laceration
Trauma to the eyelid can be routine or quite involved. A superficial laceration, parallel to the lid margin, is similar to a skin laceration in other parts of the body and can be repaired in the same manner. Foreign bodies, however, can be overlooked; therefore the wound should be explored and irrigated well before surgical closure. If the deeper structures are involved, the anatomic relations of the levator palpebral muscle, tarsal plates, and orbital septum must be known and the appropriate repairs performed. Lacerations that involve the lid margin or are medial to the punctum and involve the canalicular structures necessitate detailed surgical reconstruction. The primary repair is extremely important because secondary scar revision and attempts to reestablish the function of the eyelid and tear drainage apparatus are difficult. Faulty repair can produce a notch in the eyelid that interferes with its ability to spread the tear film. Irritation and constant tearing can be caused by loss of corneal epithelium and perhaps cause ulceration of the cornea. Involved lacerations therefore should be managed by a surgeon knowledgeable in the anatomic and physiologic characteristics of the eyelids.
Superficial Injuries of the Cornea and Conjunctiva
The cornea and conjunctiva, although important, are considered superficial eye structures, and injuries to them often can be managed by a primary care physician. Subconjunctival hemorrhage usually is without sequelae, behaving as a bruise elsewhere on the body. The patient should be reassured that the blood clears over a 10- to 20-day period. The hemorrhages can be caused by minor trauma or by coughing or sneezing. They also can occur spontaneously. There is little or no value in performing hematologic or blood coagulation studies for patients with spontaneous subconjunctival hemorrhages unless a history of frequent recurrence is given. In those cases, the possibility of blood dyscrasia should be considered. These patients have a bright red eye, normal vision, and no pain. If subconjunctival hemorrhage is a manifestation of severe trauma, however, the physician always must rule out more serious injuries to the deeper ocular structures.
Corneal or conjunctival foreign bodies first should be approached with irrigation. If this is not successful, they can be brushed with a cotton-tipped applicator or nudged out with a small pick or needle. One drop of topical anesthetic solution usually is all that is necessary to manipulate the object. If a foreign body is not seen, but the symptoms or history indicate the presence of one, fluorescein stain can be used to outline a corneal abrasion. A small strip of fluorescein paper is moistened with sterile water, and this strip is applied to the inferior cul-de-sac while the patient looks up or the superior cul-de-sac while the patient looks down. When a cobalt blue penlight or Wood lamp is used, fluorescence may outline the abrasion. If the patient wears soft contact lenses, use of fluorescein should be avoided, because the dye can permanently stain the lenses. The pain of corneal abrasion is sharp and stabbing. It is aggravated when the patient opens and closes his or her eyes and is associated with marked photophobia, unlike the deep ache of iritis and the superficial mild and intermittent discomfort of conjunctivitis.
If the abrasion is vertical over the cornea, the lid should be everted, and often a foreign body is found under the upper lid. For lid eversion, the patient looks down while a cotton-tipped applicator handle, pencil eraser, or finger is placed just beneath the orbital rim. The eyelashes are grasped with the other hand and pulled straight out from the globe, the lashes are pulled up and forward, and the eyelid flipped over with the applicator stick, pencil, or the base of the finger as a fulcrum. The everted lid is held against the orbital margin, and the underlying structures are examined. Approaching the patient with confidence makes this procedure simple.
Overwearing contact lenses or excess exposure to an ultraviolet sunlamp can cause severe punctate corneal damage with eyelid edema. Treatment usually is observation. Symptoms appear 6 to 12 hours after exposure or after the contact lenses are taken out. The patients experience marked light sensitivity and a feeling of sand or grit in the eyes. Superficial pain can be severe. There is marked spasm of the lids and associated tearing. Both eyes usually are involved.
Misplacement of contact lenses is a common emergency. The lens usually can be found with adequate evaluation in the deep folds of the conjunctival fornices. The patient should be reminded that if it is not found, the lens did not migrate posteriorly into the intracranial structures but rather dropped out.
Therapy for corneal abrasions, including treatment after removal of a foreign body, consists of antibiotic eyedrops. This is recommended if the injury was caused by contaminated material, such as a fingernail or branch. If there is a large abrasion and the eye is quite inflamed, a cycloplegic agent can be used to reduce the ciliary spasm and pain (Fig. 10.7). The eye often is patched for comfort and to speed healing. Glucocorticoids or glucocorticoids-antibiotic combinations should not be prescribed, and topical anesthetics should not be given for home use. Most small abrasions heal in 24 hours and larger ones in less than 1 week.
Blunt Trauma
A severe blow to the eye or orbit can miraculously spare the ocular structures, or it can be devastating. The most common physical finding in cases of blunt trauma is hyphema (blood in the anterior chamber). If an eye has suffered a blow hard enough to cause ciliary body bleeding, which is believed to be the origin of the blood, the anterior chamber angle structures can be disrupted and the filtration network damaged. The patient is immediately or months to years later at risk of development of increased IOP. Dislocated or subluxed cataractous lenses can be found. The vitreous can be detached and become hemorrhagic. Retinal holes or detachment also can occur. Scleral rupture can occur anteriorly or posteriorly, and the optic nerve can be contused or avulsed. Blunt trauma to the eye necessitates complete ophthalmologic examination and can necessitate lifelong care and follow-up evaluation.
Penetrating Injuries
After an eye has been penetrated, immediate and long-term treatment is administered by an ophthalmologist. Accurate diagnosis and referral without manipulation or further examination are essential in managing these injuries. If foreign bodies are partially extruding from the eye, the diagnosis is evident. The foreign body should be left intact and removed in the controlled environment of an operating room. A key to the diagnosis of penetrating trauma is a peaked or teardrop pupil. If the pupil is not round and is pulled to one side, the examiner should suspect a penetrating injury and treat the patient with extreme care. The combination of lid laceration and hyphema also suggests penetration. For transporting a patient with an open eyeball, an aluminum shield is taped or a cone made from x-ray film or a plastic drinking cup is placed over the involved eye to avoid pressure than can cause extrusion of intraocular contents. Tetanus prophylaxis is appropriate, as with any laceration.
Burns
An emergency that often comes to medical attention too late is chemical injury. Many substances are accidentally instilled in the eye, and most of these are of no consequence. Serious alkali or acid burns are emergencies. In the first few minutes, the solution must be diluted with any liquid available. It is not necessary to spend time attempting to neutralize the solution—immediate and profuse dilution is extremely important. Copious irrigation should be performed for 5 minutes, the eyelids should be held forcefully apart during irrigation. The patient can be held over a drinking fountain or under a faucet. Topical anesthetic usually is needed to remove particulate chemical matter from the eye. If lid spasm is severe, a selective facial nerve block may be needed to keep the eyelids open. After the diagnosis is made and initial treatment completed, an additional 20 minutes of continuous irrigation with balanced salt solution or Ringer solution, with a continuous intravenous drip, should be undertaken. Cycloplegic and antibiotic eyedrops usually are administered, and a sterile eye patch is gently applied. Thermal or flash burns of the eye and eyelid are managed with the same general measures as other skin burns. The ocular sequelae of chemical burns can cause total blindness. Damage to the eyelids from chemical or thermal burns usually causes severe cosmetic disfigurement, permanent tearing, exposure keratitis, and corneal ulceration or perforation.
PEDIATRIC OPHTHALMOLOGY
As the study of childhood disease entails a distinct category of otolaryngology, problems of the pediatric eye should be considered separately.
Congenital Abnormalities
The ocular structures often are affected in developmental abnormalities and congenital anomaly syndromes. These range from minor cosmetic deformities to complete lack of any visual components. Congenital glaucoma is characterized by a large eye and marked photophobia. Childhood cataracts often are of known cause, such as manifestation of congenital rubella or a consequence of an inborn error of metabolism. Any abnormality in the red reflex elicited through the ophthalmoscope during examination of a newborn should be cause for referral. The cat’s eye reflex, or white pupil, suggests many serious diseases, the most severe of which is malignant intraocular tumor of children—retinoblastoma.
Strabismus
Most of the practice of pediatric ophthalmology centers on the study of strabismus (failure of the two eyes to look at the same object) and amblyopia, an important preventable cause of vision loss. Strabismus is misalignment of the two eyes so that only one eye is directed at the specific object of regard. General ocular inspection may reveal gross deviation of one eye. The corneal light reflex allows an estimation of the amount of the deviation. The cover test can help detect almost every case of strabismus. A small amount of phoria is present among most patients with normal eyes and should not be cause for alarm.
All newborns should be examined for gross alignment of the eyes. Up to 3 to 4 months of age, children often have uncoordinated eye movements and can temporarily manifest actual strabismus. An ophthalmologist should be consulted if occasional deviations persist beyond this age. Infants with constant deviations should be referred at any age as soon as possible. The determination, by examination or history, that a deviation is intermittent is an important prognostic sign. Normal binocular vision can develop only if there is precise coordination of the two eyes. If the mental object of regard is seen by one eye and another object seen by its fellow, the brain suppresses the accessory image to avoid diplopia, thereby turning off the input from the deviating eye. If the eyes are straight at least part of the time (intermittent strabismus) or if the deviation alternates (first one eye assumes fixation and then the other), there is a chance for full development of visual potential.
Esotropia
Esodeviation is the most common type of strabismus, often manifesting itself soon after birth and frequently necessitating surgery to straighten the eyes. Esodeviation also can appear in the second or third year of life and can be associated with an attempt to focus the eyes owing to marked refractive error, which often is corrected with glasses.
Pseudostrabismus
Among children with large epicanthal folds, the appearance of esotropia can be quite marked, a condition called pseudostrabismus. When the folds flatten with age, the appearance changes, leading to the dangerous misconception that children outgrow strabismus.
Exotropia
Exodeviation is less common than esotropia. It usually occurs intermittently with fatigue, daydreaming, or when the child is in bright sunlight.
AMBLYOPIA
Amblyopia is defined as unilateral defective vision, uncorrectable by glasses, in an otherwise normal eye. It occurs among about 5% of the young adult U.S. population and is commonly known as lazy eye. Half of all patients with amblyopia have or have had associated strabismus. Refractive amblyopia occurs if there is a marked difference in refractive errors of the two eyes. Like suppression to avoid diplopia in strabismus, the brain turns off the blurred image because of the greater refractive error to obtain a clearer object of regard. Occlusion amblyopia occurs if opacities of the ocular media, such as ptosis, cataract, or a macular lesions, prevent adequate sensory input. Retinoblastoma often manifests as esotropia due to macular involvement. All patients with strabismus need complete dilated ocular examinations.
Detection
Amblyopia, if detected early, often is curable. Treatment rarely is successful after 9 years of age, and best results are obtained if the patient is treated before the age of 5 years. The key to this disease is prevention. Prompt investigation is mandatory if a child has obvious strabismus. Even if the eyes appear straight during a routine pediatric examination, the examiner should observe how the child watches a light, how he or she follows a moving object, and how the child reacts to having each eye covered alternately. If amblyopia exists, the patient probably will resent, vocally or through evasive movement, covering of the “good” eye. Even before a child can give verbal response to visual acuity testing, he or she should be able to maintain central and steady fixation with each eye. By 3 years of age, visual acuity should be measured with picture cards or single E charts. The examiner must be certain that only one eye at a time is participating in the test. Children always peek if the fellow eye is not properly occluded. Young children may not quite reach 20/20, but as long as both eyes are near that standard and equal, the physician and parents need not be disturbed. Amblyopia may be present if there is a two-line difference between the two eyes on a visual acuity chart or if vision is only 20/30 to 20/40. Although amblyopia is a relatively minor visual impairment, many adults with a history of lazy eye have vision of only 20/200 or even less.
Treatment
Therapy for amblyopia is based on the simple idea of forcing the child to use the affected eye. Proper spectacle correction is followed by patching the normally used eye. The duration of treatment is monitored by the ophthalmologist. After maximal amblyopic treatment, surgical correction of any residual strabismus is undertaken to prevent recurrence of the amblyopia and to improve cosmesis and minimize psychosocial problems. Early detection and prompt referral of patients with strabismus or amblyopia can be one of the most important contributions of a physician treating pediatric patients.
THE EYE IN SYSTEMIC DISEASE
Neurologic Disease
The ocular manifestations of systemic disease always play an important role in general medicine. Neurologic and neurosurgical diagnoses often are made from eye examinations, and the disease course is monitored with an ophthalmoscope because the eye is truly the window to the brain. Finding a fixed, dilated pupil or Marcus Gunn pupil is important. Swelling of the optic disk or true papilledema is an important ophthalmoscopic finding indicating increased intracranial pressure. A patient with papilledema has normal visual acuity, elevation of the disk with absence of the cup, blurred disk margins, venous engorgement, hyperemia of the disk, and usually hemorrhage and exudate around the disk. The presence or absence of venous pulsation is not a reliable sign. Inflammatory swelling of the optic disk (papillitis or optic neuritis), commonly a result of demyelinating disease, may appear ophthalmoscopically similar, but the patient reports markedly decreased vision due to direct nerve damage.
Optic atrophy, often described as aspirin disk, appears as a pale nerve head without normal capillaries on the surface. The presence of an atrophic nerve is sufficient to explain decreased visual acuity, but it represents only a physical finding and is not sufficient to confirm a diagnosis. The cause of optic atrophy must be established from the history or from further ophthalmoscopic or neurologic examination.
Thyroid Ophthalmopathy
Also known as Graves ophthalmopathy and thyroid orbitopathy, thyroid ophthalmopathy can raise both functional and cosmetic concerns. Although the cause of proptosis can be a primary or metastatic tumor, arteriovenous malformation, or carotid cavernous fistula, by far the most common cause of unilateral or bilateral proptosis is abnormal thyroid function. In classic Graves disease, the patient appears “bug-eyed” owing to exophthalmos and eyelid retraction (Fig. 10.8). Ocular motility may be reduced because of infiltration of the muscles and periorbital tissues with an abnormal mucopolysaccharide substance. If the cornea becomes desiccated from exposure or if orbital pressure increases to the point at which papilledema or optic atrophy occurs, the condition is considered malignant and often necessitates immediate medical and surgical therapy. Results of thyroid tests may not correlate with the progress or severity of the eye findings, but combined evaluation and follow-up care with an endocrinologist are encouraged.
Collagen Vascular Disease
The external layers of the eye have a high collagen content. Inflammatory diseases that affect this tissue, such as rheumatoid arthritis or systemic lupus erythematosus, often cause external ocular inflammation. Keratoconjunctivitis sicca is the dry eye component of Sjögren syndrome. Most of these diseases also have a vasculitic component, and retinal vascular sheathing and occlusions are common.
Systemic Infection and Metastatic Cancer
Systemic infection such as septicemia often establishes a metastatic focus in the eye, most commonly as choroiditis. Tuberculosis, syphilis, and histoplasmosis often are diagnosed in this manner. Orbital or elevated choroidal lesions often occur with metastatic carcinoma, especially metastasis from the lung and breast (Fig. 10.9).
Blood Dyscrasia
Blood dyscrasia, such as hyperviscosity syndromes, leukemia, or sickle cell disease, has characteristic retinal vascular patterns that may help confirm a diagnosis.
OCULAR SIDE EFFECTS OF MEDICATION
Referral to the Physicians’ Desk Reference quickly makes it apparent that to avoid ocular side effects, physicians should prescribe few or no systemic medications. The increased IOP and cataractogenic effects of glucocorticoids have been mentioned. Ethambutol, chloroquine, and the phenothiazines are commonly used drugs with direct toxic effects on various ocular tissues. Patients taking these and other such medications need baseline examinations and periodic ophthalmic evaluation.
DIABETES
Diabetes is associated with many eye changes, including transient changes in accommodation due to fluctuations in blood glucose level, cataract, and glaucoma. Retinopathy, however, makes diabetes the leading cause of blindness in the United States. Retinopathy is related to the duration and the control of the diabetes. Within 15 to 20 years of the onset of diabetes, persons with juvenile- and adult-onset diabetes may have a visual disability. Good metabolic control can delay the onset of retinopathy, but it cannot retard the progression.
Diabetic retinopathy can be classified as nonproliferative or proliferative. Nonproliferative or background retinopathy consists of venous abnormalities, exudate, microaneurysms, dot and blot hemorrhage, and associated retinal edema. These are the earliest changes characteristic of diabetes, and they begin in the posterior pole of the eye, which is easily viewed with a direct ophthalmoscope. Patients with background retinopathy are not treated and can be observed with routine annual or biannual examinations. Proliferative retinopathy is the development of new fragile blood vessels (neovascularization) in response to a hypoxic stimulus related to the disease. These vessels bleed into the retina and cause fibrosis and retraction of the retina into a detachment or bleed into the vitreous and cause sudden loss of vision and usually similar intravitreal fibrosis and traction on the retina. This end stage is called retinitis proliferans.
The only therapy for diabetic retinopathy is vitrectomy and intraocular membrane stripping. After the onset of retinopathy, the 5-year survival rate for the eyes approaches zero. To prevent blindness, therapy is directed at the beginning neovascularization. Laser photocoagulation, used to burn and destroy the hypoxic retina that is theoretically supplying the stimulus for neovascularization, is currently the most promising and most used mode of therapy.
HYPERTENSION AND ARTERIOSCLEROSIS
Hypertensive retinopathy and the retinal vascular changes of arteriosclerosis are characteristic. The term arteriosclerosis, not atherosclerosis, is associated with changes in the retina. The central retinal artery usually divides into superior and inferior branches before it is visible on the optic disk; therefore the vessels examined are arterioles. Diffuse narrowing of the retinal arterioles is the earliest sign of hypertension, which can be caused by the spasm of malignant hypertension of toxemia or renal disease, and is reversible. Hypertension becomes permanent, however, if the pressure remains elevated and is usually followed by segmental arterial narrowing, especially if the diastolic blood pressure is or has been greater than 120 mm Hg. Further damage to the vessel walls causes leakage of blood and plasma, forming superficial flame-shaped retinal hemorrhages, deeper dot and blot hemorrhages, hard and waxy exudates, and soft cotton wool exudates (retinal infarcts). As a response to increased intracranial pressure or to anoxia of the optic nerve, papilledema develops. The 5-year mortality among patients with papilledema related to hypertension is greater than 90%.
Retinal arteriosclerotic damage revolves around changes in vessel wall transparency and abnormality in the arteriovenous crossings. Thickening of the arteriole wall increases in the light reflex stripe viewed through an ophthalmoscope. The thickening progresses until the light reflex appears to occupy the entire width of the blood column (copper wire appearance) and on to the point at which no blood is visible at all, giving the characteristic white sclerotic silver wire appearance. At points of arteriovenous crossing, the vessels are in a common adventitial sheath. As the arteriolar walls thicken, compression of the venules becomes apparent first as tapering of the ends, progressing to banking with dilation of the venule distal to the crossing, and finally to vascular occlusion with complete interruption of blood flow.
Separate categorization of these companion diseases can be important, even though in the advanced stages, almost without exception, the changes occur together. Specific hypertensive changes can alert the physician to the severity of hypertension, which can be monitored with a sphygmomanometer. More important, the arteriosclerotic changes mark the chronicity of the disease and mirror the condition of the vessels of the kidneys, heart, and brain. Table 10.4 summarizes acute ophthalmic emergencies, including vascular disorders.
IMAGING IN OPHTHALMOLOGY
Magnetic resonance imaging (MRI) is the most sensitive modality for evaluation of most disorders of the central nervous system, including stroke, white matter lesions, and hemorrhage; however, subarachnoid hemorrhage and acute stroke are better visualized with CT. Computed tomography also is the best imaging method for evaluation of orbital trauma. Within the orbit, MRI clearly is most effective for imaging the soft tissues, optic nerve, and retrobulbar space (11,12). Magnetic resonance angiography (MRA) is an excellent screening tool for extracranial occlusive vascular disease, although it slightly exaggerates stenotic lesions. If the carotid artery is found to be totally blocked at MRA, the patient probably cannot undergo surgical treatment. If intracranial aneurysm is suspected, however, conventional angiography is the standard. Magnetic resonance imaging can be helpful in the diagnosis of craniopathy involving the orbit. For example, in third nerve palsy, MRI can help identify brainstem infarcts, hemorrhage, and arteriovenous malformation; lymphoma and trauma involving the subarachnoid space; and cavernous sinus lesions such as cancer, aneurysm, and Tolosa-Hunt syndrome