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NORMAL EYE WITH SUDDEN DECREASED VISIONRegan Januardy MarliauI11109020Optic NeuritisOptic neuritis (ON) is a demyelinating inflammation of the optic nerve that typically first occurs in young adulthood. Many cases ofONare associated withmultiple sclerosis(MS) or neuromyelitis optica (NMO), but ON can occur in isolation.

Optic neuritis, or primary inflammation of the optic nerve, is referred to as papillitis when the optic disc is swollen and retrobulbar neuritis when the disc appears normal. The most common form of optic neuritis is acute demyelinating optic neuritis.

Loss of vision is the cardinal symptom of optic neuritis and is particularly useful in differentiating papillitis from papilledema, with which it may be confused on ophthalmoscopic examination.Retrobulbar neuritis is an optic neuritis that occurs far enough behind the optic disk that the disk remains normal during the acute episode. Papillitis is disk swelling caused by inflammation at the nerve head (intraocular optic nerve) 2

EtiologyThe most common etiology ismultiple sclerosis. Up to 50% of patients with MS will develop an episode of optic neuritis, and 20-30% of the time optic neuritis is the presentingsign of MSMost cases of ON are associated with MS, even though ON can occur in isolation. In MS-associated and isolated, monosymptomatic ON, the cause is presumed to be an autoimmune reaction that results in a demyelinating inflammation of the nerve.HistoryThe patients history may reveal the following signs and symptoms of optic neuritis:Preceding viral illnessRapidly developing impairment of vision in 1 eye or, less commonly, both eyes: During an acute attackDyschromatopsia (change in color perception) in the affected eye: Occasionally may be more prominent than the decreased vision[25]Retro-orbital or ocular pain: In association with the vision changes and usually exacerbated by eye movement; the pain may precede vision lossUhthoff phenomenon, in which vision loss is exacerbated by heat or exercisePulfrich phenomenon, in which objects moving in a straight line appear to have a curved trajectory: Presumably caused by asymmetrical conduction between the optic nervesUhthoff's phenomenon(also known asUhthoff's syndrome,Uhthoff's sign, andUhthoff's Symptom) is the worsening ofneurologicsymptomsinmultiple sclerosis(MS) and other neurological, demyelinating conditions when the body gets overheated fromhot weather,exercise,fever, orsaunasandhot tubs. It is possibly due to the effect of increased temperatureonnerve conduction.With an increased body temperature,nerve impulsesare either blocked or slowed down in a damaged nerve but once the body temperature is normalized, signs and symptoms may disappear or improve.

ThePulfrich effectis apsychophysicalperceptwhereinlateralmotion of an object in the field of view is interpreted by thevisual cortexas having a depth component, due to a relative difference in signal timings between the two eyes. The widely accepted explanation of the apparent depth is that a reduction in retinal illumination (relative to the fellow eye) yields a corresponding delay in signal transmission, imparting instantaneous spatial disparity in moving objects. This seems to occur because visual system latencies are generally shorter (i.e., the visual system responds more quickly) for bright targets as compared to dim targets. This motion with depth is the visual system's solution to a moving target when a difference in retinal illuminance, and hence a difference in signal latencies, exists between the two eyes.5Ocular ManifestationsVisual loss is generally subacute, developing over 27 days. Color vision and contrast sensitivity are correspondingly impaired. Visual loss is usually monocular, although occasionally both eyes are affected simultaneously, particularly in children.In over 90% of cases, there is pain in the region of the eye, and about 50% of patients report that the pain is exacerbated by eye movement.Almost any field defect is possible, but with manual perimetry, a central scotoma is most commonly found. It is usually circular, varying widely in size and density.

The optic disc appears normal in approximately two thirds of adults with acute demyelinating optic neuritis (retrobulbar optic neuritis), while disc swelling is present in about one third of adult cases (papillitis).Funduscopic features of optic disc swelling include elevation of the optic nerve head, disk hyperemia, blurring of the disc margins, and edema of the nerve fiber layer.[31] Although the clinical features are similar in both forms, optic disc hemorrhages were uncommon

PapilitisOptic papillitisis a specific type ofoptic neuritis. Inflammation of the optic nerve head (papilla)is called "papillitis" or "intraocular optic neuritis"

Papilledema refers to swelling of the optic optic disc from increased intracranial pressure.Both optic disc are affectedThe visual acuity and the pupillary reflexes are usually normalSome patients with acute papilledema complain of momentary blurring or transient obscurations of visionAlthough chronic papilledema may lead to loss of vision, most patients with acute papilledema sufferonly minor alterations in vision8Retrobulbar optic neuritisA monocular loss of vision that has developed over hours to days and that is often accompanied by pain on movement of the eye who shows no abnormalities in eye examination probably caused by retrobulbar optic neuritisIn retrobulbar optic neuritis, the inflammation and demyelination occur behind the globe of the eye. The optic disc appears normal with no signs of swelling or pallor.

DiagnosisThe diagnosis of acute demyelinating optic neuritis is based on an appropriate history (typical versus atypical course) and clinical signs, and symptom. Diagnostic tests, including magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, and serological studies, usually are performed for the following reasons:To determine if the cause is noninflammatory (such as a compressive lesion), or a nonidiopathic inflammatory or infectious process in cases that are not typical for acute demyelinating optic neuritis.To determine the prognosis or risk for subsequent development of MS in monosymptomatic cases for which the history and clinical signs are typical.Papillitis needs to be differentiated from papilledema (optic disc swelling due to raised intracranial pressure) (Figure 149). In papilledema, which usually causes bilateral optic disk changes, there is often greater elevation of the optic nerve head, normal corrected visual acuity, normal pupillary response to light, and an intact visual field except for an enlarged blind spot. If there has been acute papilledema with vascular decompensation (ie, hemorrhages and cotton-wool spots) or chronic papilledema with secondary ischemia of the optic nerve, visual field defects can include nerve fiber bundle defects and nasal quadrantanopias. Differentiation between papilledema and papillitis is particularly difficult when papilledema is asymmetric and/or associated with visual loss or papillitis is bilateral and/or associated with minimal visual impairment. Diagnosis may depend on results of MRI and lumbar puncture, as well as subsequent clinical course.

10TreatmentSteroid therapyeither intravenously, orally, or by retrobulbar injectionprobably accelerates recovery of vision but does not influence the ultimate visual outcomeIV steroids do little to affect the ultimate visual acuity in patients with ON, but they do speed the rate of recovery.Oral prednisolone alone did not improve rapidity of visual recovery and increased the risk of recurrent optic neuritis in either eye.

PrognosisWithout treatment, vision characteristically begins to improve 23 weeks after onset and sometimes recovers within a few days. A poor visual outcome is also associated with longer lesions in the optic nerve, especially if there is involvement of the nerve within the optic canal.In general, there is close correlation between recovery of visual acuity, contrast sensitivity, and color vision.

intravenously (methylprednisolone, 1 g/d for 3 days with or without a subsequent tapering course of oral prednisolone), orally (methylprednisolone, 500 mg/d to 2 g/d for 35 days with or without subsequent oral prednisolone, or prednisolone, 1 mg/kg/d tapered over 1021 days11Vitreous HemorrhageVitreous hemorrhage is the extravasation of blood into one of the several potential spaces formed within and around the vitreous body. This condition may result directly from retinal tears or neovascularization of the retina, or it may be related to bleeding from pre-existing blood vessels in these structures.

Hemorrhage into the vitreous cavity can result in sudden painless loss of vision. The extent of visual loss will depend on the degree of hemorrhageA large hemorrhage will cause total visual lossA small hemorrhage will present as oaters and normal or only slightly reduced visual acuity

PathophysiologyThe vitreous is avascular and inelastic. Pathological mechanisms of vitreous hemorrhage include hemorrhage from diseased retina, traumatic insult, and/or spread of hemorrhage into the retina and vitreous from any other intraocular sources.The most common causes include proliferative diabetic retinopathy, vitreous detachment with or without retinal breaks, and trauma. Less common causes include vascular occlusive disease, retinal arterial macroaneurysm, hemoglobinopathies, age-related macular degeneration, intraocular tumors, and others.Mechanism of hemorrhageAbnormal vessels.Abnormal retinal blood vessels are typically the result of neovascularization due to ischemia in diseases such as diabetic retinopathy. As the retina experiences inadequate oxygen supply, vascular endothelial growth factor (VEGF) and other chemotactic factors induce neovascularization. These newly formed vessels lack endothelial tight junctions, which predispose them to spontaneous bleeding.

Rupture of normal vessels.Normal vessels can rupture when sufficient mechanical force overcomes the structural integrity of the vessel. During a posterior vitreous detachment, vitreous traction on the retinal vasculature may compromise a blood vessel. This may happen with or without a retinal tear or detachment. Blunt or perforating trauma can injure intact vessels directly and is the leading cause of vitreous hemorrhage in people younger than 40.

Posterior vitreous detachment can result in vitreous haemorrhage if,as the vitreous separates from the retina,it pulls and ruptures a small blood vessel

15Blood from an adjacent source.Pathology adjacent to the vitreous can also cause vitreous hemorrhage. Hemorrhage from retinal macroaneurysms, tumors and choroidal neovascularization can all extend through the internal limiting membrane into the vitreous.Age-related macula degeneration (AMD)haemorrhage may occur into the vitreous from the abnormally weak vessels forming a subretinal neovascular membrane

Sign and symptomsThe symptoms of vitreous hemorrhage are varied but usually include painless unilateral floaters and/or visual loss.Early or mild hemorrhage may be described as floaters, cobwebs, haze, shadows or a red hue. More significant hemorrhage limits visual acuity and visual fields or can cause scotomas. Patients often say vision is worse in the morning as blood has settled to the back of the eye, covering the macula.Patients should be questioned regarding a history of trauma, ocular surgery, diabetes, sickle cell anemia, leukemia, carotid artery disease and high myopia.Complete examination consists of indirect ophthalmoscopy with scleral depression, gonioscopy to evaluate neovascularization of the angle, IOP and B-scan ultrasonography if complete view of the posterior pole is obscured by blood. Dilated examination of the contralateral eye can help provide clues to the etiology of the vitreous hemorrhage, such as proliferative diabetic retinopathy.TreatmentThe presence of a retinal detachment may be determined using ultrasonography if an adequate view of the posterior segment is not possible. Treatment is directed at the underlying cause, such as laser photo-coagulation for proliferative diabetic retinopathy or for retinal breaks. Occasionally, hemorrhage does not resolve spontaneously and vitrectomy surgery is necessary and beneficial.Vitrectomy is performed urgently when a retinal detachment or break is identified.Once the retina can be visualized, treatment is aimed at the underlying etiology as soon as possible. If neovascularization from proliferative retinopathy is the cause, laser panretinal photocoagulation is performed, if possible through the residual hemorrhage, to cause regression of neovascularization. A krypton laser may aid photocoagulation as it passes through hemorrhage better than argon lasers. An indirect laser system may also allow energy delivery to the retina around a vitreous hemorrhage. Alternatively, in the interim, intravitreal anti-VEGF agents may induce regression of the neovascularization until laser photocoagulation is possible.

retinal breaks are closed by laser photocoagulation or cryotherapy (unlike cryotherapy, laser photocoagulation can close the compromised vessel in addition to the retinal tear); detached retinas are reattached with surgery; and proliferative retinal vascular diseases are treated with laser photocoagulation or cryotherapy (when there is no view of the retina).18Retinal Artery OcclusionRetinal arterial obstructions are divided anatomically into central and branch, depending on the precise site of obstruction. A central retinal artery obstruction occurs when the blockage is within the optic nerve substance itself and therefore the site of obstruction is generally not visible on ophthalmoscopy. Central retinal artery occlusion causes painless catastrophic visual loss occurring over a period of seconds; antecedent transient visual loss (amaurosis fugax) may be reported. Visual acuity ranges between counting fingers and light perception in 90% of eyes at initial examinationA branch retinal artery obstruction occurs when the site of blockage is distal to the lamina cribrosa of the optic nerve.Branch retinal artery is usually embolic in origin and results in visual field loss. Visual acuity is only reduced if there is foveal involvement.

Central Retinal Artery OcclusionPathogenesisThe majority of central retinal artery obstructions are caused by thrombus formation at or just proximal to the lamina cribrosa.Atherosclerosis is implicated as the inciting event in most cases, although congenital anomalies of the central retinal artery, systemic coagulopathies, or low-flow states from more proximal arterial disease may also be present and render certain individuals more susceptible.Inflammation in the form of vasculitis (e.g., varicella infection), optic neuritis, or even orbital disease (e.g., mucormycosis) may cause central retinal artery obstruction. Local trauma that results in direct damage to the optic nerve or blood vessels may lead to central retinal artery obstruction. Arterial spasm or dissection rarely produces retinal arterial obstruction. In addition, systemic coagulopathies may be associated with both central and branch retinal artery obstructions.

Ocular manifestationThe hallmark symptom of acute central retinal artery obstruction is abrupt, painless loss of vision.Within the first few minutes to hours after the obstruction, the fundus may appear relatively normal. Eventually, the decreased blood flow results in ischemic whitening of the retina in the territory of the obstructed arteryA cherry-red spot of the macula is typical and arises in this area because the nerve fiber layer is thin.

Fig. 6-16-1 The left eye of a healthy 37-year-old man. The patient had a 3-hour history of visual loss and a visual acuity of 20/60 (6/18). (A) Retinal whitening is very subtle and the retinal vessels appear normal. (B) Fluorescein angiography reveals abnormal arterial filling with a leading edge of dye that confirms central retinal artery obstruction. (C) The same eye 24hours later. Despite intravenous urokinase, visual acuity dropped to hand movements, and intense retinal whitening with a cherry-red spot is present. Note the interruption in the blood column of the retinal arteries.

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DiagnosisDiagnosis of central retinal artery obstruction is straightforward when diffuse ischemic retinal whitening is present in the setting of abrupt, painless visual loss. Fluorescein angiography may help if the diagnosis is in doubt.

TreatmentNo proved treatment exists for central retinal artery obstruction, but treatment strategies center around the following goals:Increase retinal oxygenationIncrease retinal arterial blood flowReverse arterial obstructionPrevent hypoxic retinal damageBranch Retinal Artery OcclusionPathogenesisBranch retinal artery obstruction is a rare event, even less common than central retinal artery obstruction overall.Over two thirds of branch retinal artery obstructions are secondary to emboli to the retinal circulation. In most cases, the emboli are clearly visible in the arterial tree. Emboli to the retinal circulation may originate at any point in the proximal circulation from the heart to the ophthalmic artery. Risk factors reflect the vasculopathic mechanisms that produce disease within the cardiovascular system. These include predisposing family history, hypertension, elevated lipid levels, cigarette smoking, and diabetes mellitus.Three main types of retinal emboli have been identified:Cholesterol (Hollenhorst plaque)Platelet-fibrinCalcificCholesterol emboli typically emanate from atheromatous plaques of the ipsilateral carotid artery system. They are yellow-orange in color, refractile, and globular or rectangular in shape. They may be small and can on occasion be seen intravascularly without blockage of blood flow. Platelet-fibrin emboli are long, smooth, white-colored, intra-arterial plugs that may be mobile or break up over time. Usually, they are associated with carotid or cardiac thromboses. Calcific emboli are solid, white, nonrefractile plugs associated with calcification of heart valves or the aorta.

Ocular manifestationAbrupt, painless loss of vision in the visual field corresponding to the territory of the obstructed artery is the typical history of presentation.Retinal whitening that corresponds to the areas of ischemia is the most notable finding. The whitening stops at adjacent retinal veins, as these vessels mark the extent of the territory of the retinal arteries

Color fundus photo of right eye with inferior branch retinal artery occlusion from a platelet-fibrin embolus. Retinal whitening surrounding the occluded artery is noted.Red-free photograph (before injection of fluorescein) of right eye with inferior branch retinal artery occlusion. The red-free photograph greatly accentuates the retinal whitening surrounding the occluded artery.Fluorescein angiogram of right eye with inferior branch retinal artery occlusion. Delayed filling of the artery (arrow heads) by the fluorescein is noted.

27DiagnosisAncillary testing is not usually necessary to make the diagnosis. Fluorescein angiography reveals an abrupt diminution in dye at the site of the obstruction and distally. Visual field testing can confirm the extent of visual loss and may pick up contralateral field loss from previous emboli or other associated conditions.

TreatmentWarfarin prevents the blood from clotting. This medication is often used in patients with atrial fibrillation to decrease their risk of stroke.To prevent stroke, most patients with branch retinal artery obstruction (BRAO) are placed on some form of antiplatelet therapy, such as aspirin, clopidogrel , dipyridamole , and ticlopidine.No proved treatment exists for branch retinal artery obstruction. Because the visual prognosis is much better for branch retinal artery obstruction than for central retinal artery obstruction, invasive therapeutic maneuvers of dubious utility are not typically performed. On occasion, ocular massage or paracentesis is successful in dislodging an embolus. Laser photocoagulation has been employed to melt an embolus, without improvement in the vision.[38]One report suggests that hyperbaric oxygen therapy may improve the visual loss associated with multiple branch retinal artery obstruction in Susacs syndrome.[39]In the rare patient who has branch retinal artery obstruction accompanied by a systemic clotting disorder, systemic anticoagulation may prevent further events.

28Retinal Vein OcclusionVenous obstructive disease of the retina is a common retinal vascular disorder, second only to diabetic retinopathy in incidence. It typically affects patients 50 years of age or older. Retinal vein obstructions are classified according to whether the central retinal vein (Central retinal vein obstruction (CRVO)) or one of its branches is obstructed (branch retinal vein obstruction (BRVO)). Central Retinal Vein OcclusionCRVO is also a retinal vascular disease but involves occlusion of the main central retinal vein. Vascular, hematologic, and cardiac disease may predispose individuals to develop CRVO which leads to leakage of blood and fluid into the retina. In many cases the resultant poor circulation (ischemia) can lead to abnormal blood vessel formation in the iris (rubeosis) with painful increases in eye pressure (neovascular glaucoma).CRVO can be divided further into ischemic and nonischemic-varieties. This distinction among types of CRVO, although somewhat arbitrary, is important because up to two thirds of patients who have the ischemic variety develop iris neovascularization and neovascular glaucoma.

Ocular Manifestation

Alternative names include partial, incomplete, imminent, threatened, incipient, or impending vein obstruction, as well as venous stasis retinopathy.[11] Of all patients with CRVO, 7580% can be classified as having the milder form. Patients manifest mild to moderate decreased visual acuity, although this can vary from normal to as poor as finger counting only. Intermittent blurring or transient visual obscuration also may be a complaint, and may precede the onset of the occlusion. Pain is rare.Pupillary testing rarely reveals an afferent defect, which, if present, is only slight. Ophthalmoscopy reveals a variable number of dot and flame retinal hemorrhages, present in all four quadrants ( Fig. 6-17-1 ). Optic nerve head swelling is common, and engorgement and tortuosity of the retinal veins are characteristic. Cotton-wool spots, if present, are few in number and located posteriorly. When vision is decreased, this is usually the result of macular hemorrhage or edema, which may be in the form of cystoid macular edema, diffuse macular thickening, or both.

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Ischemic CRVOs are referred to as severe, complete, or total vein obstruction, and hemorrhagic retinopathy;[11] they account for 2025% of all CRVOs. Acute, markedly decreased visual acuity is the usual initial complaint. Vision usually ranges from 20/200 (6/60) to hand-motion acuity. A prominent afferent pupillary defect is typical. Pain at the time of evaluation may occur if neovascular glaucoma has developed.The ophthalmoscopic picture of an ischemic CRVO may be confused with other entities, but rarely. It is characterized by extensive retinal hemorrhages in all four quadrants, most notably centered in the posterior pole ( Fig. 6-17-2 ). Hemorrhages can be so extensive that the retinal and choroidal details are obscured. Bleeding may break through the internal limiting membrane, which results in vitreous hemorrhage. The optic disc usually is edematous, and the retinal veins are markedly engorged and tortuous. Cotton-wool spots are usually present and may be numerous. Macular edema is often severe but may be obscured by hemorrhage. Massive lipid exudation in the macular region can occur, especially in patients who have elevated triglyceride levels. Exudative retinal detachment may develop and is associated with a poor visual prognosis. Secondary, non-neovascular angle-closure glaucoma may occur.

32DiagnosisThe diagnosis of an ischemic CRVO is based on the characteristic fundus findings.Fluorescein angiography is the most useful ancillary test for the evaluation of the two most serious, debilitating and, unfortunately, common complications of CRVO-anterior segment neovascularization and macular edema.

TreatmentNo known treatment reverses the pathology seen in CRVO. Aspirin; systemic anticoagulation with coumarin, heparin, and alteplase; local anticoagulation with intravitreal alteplase; corticosteroids; anti-inflammatory agents; isovolemic hemodilution; plasmapheresis; and optic nerve sheath decompression all have been advocated but without definitive proof of efficacyLaser photocoagulation is the known treatment of choice in the treatment of various complications associated with retinal vascular diseases (eg, diabetic retinopathy, branch retinal vein occlusion).33Branch Retinal Vein OcclusionBranch retinal vein obstruction (BRVO) is a common retinal vascular disorder of the elderly. Visual loss from a branch retinal vein occlusion usually is caused by macular edema, macular ischemia, or vitreous hemorrhage. In some patients, laser treatment can help stabilize or even improve vision.It is postulated that a rigid, arteriosclerotic artery compresses the retinal vein, which results in turbulent blood flow and endothelial damage, followed by thrombosis and obstruction of the vein. Most BRVOs occur superotemporally, probably because this is where the highest concentration of arteriovenous crossings lies.Ocular manifestationsPatients with branch retinal vein occlusion usually complain of sudden onset of blurred vision or a visual field defect. Retinal hemorrhages confined to the distribution of a retinal vein are characteristic for BRVO. As a result of the distribution, the hemorrhages usually assume a triangular configuration with the apex at the site of blockage. Mild obstructions are associated with a relatively small amount of hemorrhage. Complete obstructions result in extensive intraretinal hemorrhages, cotton-wool spot formation, and widespread capillary nonperfusion. If the macular region is involved, macular edema, ischemia, or hemorrhage occurs, which causes decreased visual acuity.Branch retinal vein obstruction. Fundus view of extensive retinal hemorrhages in segmental distribution of a superotemporal retinal vein. Dilated, tortuous veins, cotton-wool spots, and macular edema also can be seen

DiagnosisThe diagnosis of an acute BRVO is made by finding retinal hemorrhages in the distribution of an obstructed retinal vein.Fluorescein angiography is a helpful adjunct for both establishment of the diagnosis and guidance for the treatment of BRVO.

TreatmentMedical treatment of branch retinal vein occlusion (BRVO) is not effective. In the past, anticoagulants, fibrinolytic agents, clofibrate capsules (Atromid-S), and carbogen inhalation have been used but without success.Because visual acuity and macular edema may improve spontaneously, patients were not treated with laser for at least 3 months after the development of the vein obstruction, to allow for spontaneous improvement. Also, treatment was delayed if the intraretinal hemorrhage was too dense to allow either photocoagulation or adequate evaluation with fluorescein angiography.37