Peripheral Retina Lecture Notes



Peripheral Retina Lecture

You must have a good understanding of the anatomical location of the peripheral retina structures and their relationship to one another. The peripheral retina is defined as the zone from the equator to the ora serrata and is approximately three to four disc diameters (3DD-4DD) in width.

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ANATOMICAL STRUCTURES OF THE RIGHT EYES PERIPHERAL RETINA

The vortex veins and ampullae will serve as very good landmarks for an examiner. These vortex ampullae and veins represent the equator of the eye. They are very important when one wants to describe retinal defects and their relationship to the rest of the retina. Vortex veins and ampullae are usually very easily seen in fair complexioned, light hair and blue eyed individuals. However, they might blend in with the rest of the retinal pigment background making them more difficult to delineate. There is always some pigment migration, in these cases, toward and around the vortex ampullae and in these cases the pigment migration is the only clue to the vortex ampullae location.

The long ciliary nerves are your two horizontal landmarks located at three and nine o'clock. They have a broad base located at the ora and taper to a somewhat rounded apex approximately at the equator. The short ciliary nerves are most visible in the superior and inferior peripheral retina and usually located very near one of the vortex veins and ampullae. They may run all the way to the ora or only be seen as a very short whitish to yellow colored structure that definitely stands out from the rest of the retina

The ora serrata is the point where the choroid and retina end. The ora will vary in color from black, brown to a felt soft gray. It is not uncommon to find the retina near it to have a slightly off colored orange gray appearance known as chorioretinal degeneration. This can be broken down in to mild, moderate, and severe degeneration. Regardless how one classifies the degeneration there is little to worry about and is considered to be benign with no predisposition to retinal holes or tears

The pars plana, when first seen, is very confusing because in many patients it looks very much like the rest of the retina in color. It is usually noticed while looking at the ora serrata and the degeneration near the ora. Suddenly one finds themselves trying to determine what they have just discovered. One moment the pigmented ora is seen then what appears to be normal colored retina jumps into view. It must be pointed out that you will not see this structure in every patient unless the pupil is dilated maximally.

It is essential that everyone realizes the primary reason for performing a dilated examination of the peripheral retina is to detect potential retinal detachments (RD). There are of course other findings a dilated retinal examination can reveal, but RD are the primary reason. Retinal detachments constitute a separation of the sensory retina from the underlying retinal pigment epithelium, (RPE) due to the accumulation of liquefied vitreous fluid in that potential space. Most RD are the result of one or more retinal holes that allow passage of fluid between the sensory retina and the RPE. The RD may be quite flat or become large and bullous protruding into the vitreous cavity and undulate with eye movements. The bullous detachment is an active detachment with sloping visual field margins. Detachments may occur anywhere in the retina where a hole or tear is located. Superior detachments are potentially more serious than inferior ones because of gravity. They may rapidly extend inferior to detach the macula with loss of central vision which may be permanent, even if surgery is successful in restoring the retina to its proper position. Older or small incomplete RD will leave a pigmented line along their borders. These flat peripheral RD if suspect must be sclerally indented to differentially them from a flat retinoschisis. Dr. James Hunter refers to these pigmented (demarcation) lines as danger lines. If not correctly diagnosed an the patient later develops a RD the doctor is in danger of being sued.

Symptoms associated with a RD may be minimal to no symptoms at all. Frequently the patient complains of light flashes, dark floating specks, and a curtain-like defect in their field of vision. Patients with these complaints must be seen promptly. Most retinal detachments are associated with retinal holes and the holes, in turn, are the result of vitreous traction. Vitreous traction may cause a classic horseshoe tear or retinal break making the patient more predisposed to developing a retinal detachment.

BENIGN PERIPHERAL RETINA FINDINGS

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1.) It is common to fine cystoidal degeneration near the ora serrata. It is found in most all adult eyes and increases with age. Though considered to be benign by itself it is involved with some other conditions that are not so benign. These will be discussed later (retinoschisis ).

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2.) Pavingstone or Cobblestone degeneration is found in about 27% of the population. It is considered by some not to be a degeneration but a retinal defect that has been present since birth. Though the retina appears atrophied the condition is more like that of a coloboma or failure of that part of the retina to develop. It is most often found in the inferior-temporal part of the retina between the ora and the equator. Dr. Alexander, however, classifies this as a degeneration seen in patients over the age of 20 years.

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3.) Reticular pigmentary degeneration is a common finding in the peripheral fundi of older patients. When these areas are indented one usually finds an area of honeycomb degeneration present deeper in the retina.

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4.) Equatorial drusens are another common finding that is very interesting and are usually only note worthy. They are usually of the soft fluffy type and as long as they do not involve the macula foveal area they seldom cause vision problems. What are drusens? The RPE functions in several ways. It forms an outer blood-retina barrier, works in the transport of metabolites between the choriocapillaris and the retina, functions to eliminate damaged and discarded photoreceptor outer segments and works to prevent the development of choroidal neovascular nets. When the RPE cells are not functioning properly they produce an extracellular material such as collagen an basement membrane material, which is deposited onto Bruch's membrane. The resulting deposits are called drusens which are composed of mucopolysaccharides and lipids. One might think of drusens as kind of garbage dump resulting from a not too healthy RPE. Drusens of some form are found in over 70% of patients over 50 years and do not negatively affect all eyes.

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5.) Choroidal or pigmentary degeneration, are one and the same and is located at or near the ora. Another peripheral retinal condition that is only note worthy.

RHEGMATOGENOUS PERIPHERAL CONDITIONS

1.) Lattice degeneration, (Non-pigmented & pigmented lattice) holes within this degeneration are the result of extreme thinning of the retinal tissue.

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Pigmented lattice like degeneration aligned with a peripheral vessel.

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• A.) Retinal erosion (non-pigmented)

• B.) Snail track (non-pigmented) with holes and tears

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2.) Retinoschisis - bullous & flat

• A.) Acquired or Reticular schisis

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• B.) Congenital or Typical Schisis

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3.) White Without Pressure

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4.) Vitreoretinal Adhesions (Retinal Tag)

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5.) Snowflake Vitreoretinal Degeneration once was thought to be a benign finding. However, recent findings classify it as an inherited condition which may be related to retinitis pigmentosa. The retinal layers involved included the inner retinal layers. The condition progresses through four stages and may develop retinal breaks, retinal detachments, or neovascularization of the peripheral retina may occur.

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Rhegmatogenous means to tear or break. In these cases it is related to retinal areas of degeneration that may develop tears, breaks or holes leading to retinal detachments. The reason dilation and peripheral retinal examinations are so very important is detecting conditions that may lead to retinal detachments or patients who have retinal detachments. It is somewhat surprising that about 50% of all patients with retinal detachments are totally asymptomatic.

Detachments not secondary to a retinal holes tears or breaks are called nonrhegmatogenous detachments and are caused by primary choroidal tumors, inflammation, or metastatic lesions. The tumors that commonly produce these "secondary" detachments are choroidal melanomas or metastatic carcinomas from the breast, lung, and prostate which migrate to the choroidal vascular system.

LATTICE DEGENERATION: The clinical appearance is that of circumferentially oriented, sausage-shaped areas. Located at or between the equator and the ora serrata, of increased atrophic thinning retina and increased retinal pigment epithelium (RPE) pigmentation. The vitreous over lying this area is liquefied and the vitreous membrane is firmly attached. Radial white (lattice) lines represent sclerosed retinal vessels and along with these may be overlaying vitreoretinal (glitter). The majority of the lesion has a grayish white appearance. Holes which occur within lattice areas are either the result of continued thinning of the retinal tissue or secondary to vitreoretinal adhesions which are associated with the lesion. Tears occur as a result of vitreoretinal adhesions and traction at the borders of the primary lesions. Tears and holes have a deeper reddish color than the surrounding lesion or retina which helps make a differential diagnosis.

Other atrophic equatorial retinal changes are "retinal erosion" and "snail tracks" which are grayish in color and most likely variations of lattice degeneration. They do lack the pigmentation, but have many of the other characteristics of lattice degeneration. A very good term for these areas of atrophy is "lattice like" degeneration".

RETINOSCHISIS: There is a congenital "flat"("typical" according to Dr. Alexander, probably to differentiate it from Congenital Hereditary Retinoschisis) retinoschisis which is the splitting of the nerve fiber layer at the outer plexiform layer. Dr. Alexander believes the "flat" schisis represents an advanced form of cystoid degeneration. Then there is the acquired "bullous" ("reticular" according to Dr. Alexander) form of retinoschisis. The acquired form if not the most common is certainly the most eye-catching looking like a water blister protruding inwardly toward the inside of the eye. Some believe it is actually a complication occurring secondary to peripheral cystoid retinal degeneration. Clinically, degenerative acquired retinoschisis appears as a ballooning "bullous" retinal elevation with smooth sharp borders. The cavity of "bullous" schisis is thought to be filled with hyaluronic acid a mucopolysaccharide. Hyaluronic acid is typically very viscous, a component of the vitreous, which would explain the taut appearance of the schisis. The condition is the result of splitting of the inner limiting membrane and the outer nuclear layer of the retina. The neuroepithelium remains intact, but the inner layer becomes stretched and thinned because of the vitreous traction. Vitreoretinal "glitter" which is sometimes referred to as "snowflakes" and sclerosed whitish colored retinal vessels are found on its inner surface. These vessels give it a reticular appearance and are common findings on the inner layer. Retinal holes or breaks may occur in either the inner or outer layers; holes in just the inner layer are basically note worthy, while holes in the outer layer are of greater concern, e.g., retinal detachments are more likely. Superior bullous retinoschisis with inner and outer layer breaks or a schisis that is already posterior to the equator should be referred for a second opinion. Because of the splitting of the retina the field defects are absolute and have steep borders. Bullous retinoschisis do not undulate (wave) with eye movements like a retinal detachment. Holes in the inner layer are not treated because they are simply openings into the cystic cavity, but outer layer holes may require treatment, since they could facilitate the formation of a retinal detachment. Cases with holes in both layers should be referred for consultation and possible treatment.

VITREORETINAL ADHESION (RETINAL TAG): These are areas of atypical retinal tissue to which the vitreous membrane has become firmly attached. The condition may be either congenital or acquired, in that the atypical retinal tissue may have been present from birth or resulted from a small area of inflammation or trauma. With vitreous age changes, the vitreous body liquefies and shrinks, causing a strong physical tugging on this area of retina. Two things may happen, either a small plug of retina will pull free releasing the physical tension or the retina will tear. If a plug of retina pulls free releasing the tension the likelihood of a retinal detachment is very small. However, if the retina tears the odds of a retinal detachment then or in the future are greatly increased. These areas should be monitored every 2 months, then 4 months and every 6 months, however, tears should either be referred or monitored more closely. Photographs of these areas are a great aid in monitoring patients.

Patient education in all rhegmatogenous cases is a must . It is extremely important and should always be recorded in the patients record that the patient has been educated regarding symptoms associated with RD. Also, record when you want to see them again then followed this up with a recall card. Patients should be told to return anytime they experience any visual changes; increased number of floaters, spots, flashes of light, veil like curtain affecting peripheral vision or any change of concern.

In the event of any of these symptoms and negative dilated fundus examination findings you must always check for "Shafer's Sign". The presence of pigment granules in Berger's space or anterior vitreous indicates there is a retinal break or detachment. Pigment granules may be present if the patient has had previous ocular surgery, but you cannot allow that to influence the need to go back and take another look.

Dr. James E. Hunter conducted a peripheral retina study on 1000 patients. All patients were dilated and B.I.O. examinations performed. The break down of the 1000 patients is as follows:

Caucasians = 692

African Americans = 308

1.) Lattice degeneration (all types)

• Present in 3.5% of the Caucasians

• Present in 7.0% of the African Americans

2.) Retinoschisis (all types)

• Present in 0.5% of the Caucasians

• Present in 1.0% of the African Americans

3.) White without pressure

• Present in 2.5% of the Caucasians

• Present in 23% of the African Americans

In all conditions African Americans had a higher incidence, even though there were more than twice the number of Caucasians in the study. The condition of white without pressure might be understandable for it is much easier seen in a darkly pigmented retinas. However, it is still hard to accept that African Americans would have such a significantly higher incidence of white without pressure than Caucasians.

You should be familiar with the following slides and the description information plus the Manual Handout on peripheral retina.

1.) Histoplasmosis - Presumed Ocular Histoplasmosis Syndrome (POHS) has a triad of retinal involvement ( a.) peripheral atrophic retinal spots-punched out lesions (b.) peripapillary choroidal atrophy (c.) exudative maculopathy secondary to choroidal neovascular membranes. the condition is fungal related an associated with birds. The condition is a (hypersensitivity reaction) with the organisms reaching the choroidal circulation during a systemic involvement. Active histoplasmosis does not produce the massive proliferation of cells within the vitreous body like toxoplasmosis. See color plates 79 through 82 in Dr. Alexander's book. (Monitor closely, Amsler Grid)

2.) Choroidal nevus (Benign Choroidal Melanoma)- usually a flat, grayish-green lesion which varies in size. Overlying drusens and increase in size tendency with age. Red-free, green filter, is used to differentiate choroidal from retinal. Up to 2DD in size document and follow. 2DD to 5DD be suspicious with special testing and careful follow-up care. Over 5DD assume malignancy until proven otherwise. See color plate 98 in Dr. Alexander's book. (Note those 2 1/2 to 5 disc diameters or larger should be monitored more closely; more likely to develop into malignant tumors).

3.) Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE), also know as a Halo nevus, is a benign condition. However, there is a relative scotoma which corresponds to the area of hypertrophy when tested with threshold fields. With increase in age the scotoma becomes more absolute because of atrophy of the underlying chorioretina and overlying sensory retinal degeneration. See color plates 95 & 96 and pages 376-377 in Dr. Alexander's book.

4.) Horseshoe tears - are a direct result of vitreoretinal adhesions. This break coupled with the liquefied vitreous greatly increases the risk for a rhegmatogenous retina detachment. See color plate 109 in Dr. Alexander's book. It is not a horseshoe tear, but is a tear secondary to vitreoretinal traction. Page 404 has a black and white photograph of a horseshoe tear. (These tears should be referred).

5.) Toxoplasmosis - is an intracellular protozoan parasite an can be either congenital or acquired in nature. It is one of the more likely causes of posterior uveitis in the United States. The most common route of congenital or maternal toxoplasmosis is exposure of the mother to cat feces, as the cat is the natural host for the parasite. The protozoa enters the eye via the circulatory system, then locates within the nerve fiber layer. The ocular inflammation caused by the parasite and hypersensitivity reaction is likened to "headlights in the fog" because the inflammation and lesion has a white central area seen through a very hazy vitreous filled with cells and debris. See color plates 83 & 84 plus pages 316 & 317 in Dr. Alexander's book.

6.) Branch Retina Vein Occlusion (BRVO) - has been reported to be the second most prevalent retinal vascular diseases seen in eyecare practice. Occurs most frequently at arteriovenous crossings and is the result of a thickened artery pressing on a thin-walled vein. The clinical picture can vary depending on the site of the occlusion. The superior temporal veins are affected most often because there are more arteriovenous crossings in the superior temporal retina then elsewhere. The clinical picture is that of dilated tortuous veins, dot-blot and flame shape hemorrhages from the site of obstruction out to the retinal periphery in the sector of the retina drained by the affected vein. See color plates 34, 38, and 39 in Dr. Alexander's book.

7.) Metastactic tumors- One cannot determine if a choroidal tumor is metastatic just by the color, however, they are typically yellowish-white with deposits of lipofucin. They are usually different in color from the malignant choroidal melanoma. The prognosis is relatively poor in malignant choroidal melanomas and metastatic tumors. Regardless of the final outcome, all suspect uveal melanomas deserve a consultation with a retinal oncologist for this is a vision and life threating condition. See color plates 99 and 100 in Dr. Alexander's book. (If that's what you think you have, refer).

8.) Disciform macular degeneration (Wet "Exudative"- Age Related Macular Degeneration (ARM)- has long been associated with drusens even though the neovascular growth occurs away from the visible drusens, within the RPE and Bruch's membrane. The presence of soft fluffy drusens, really choroidal infiltrates or RPE detachments, should increase the doctor's suspicion. Choroidal neovascularization occurs as the result of disruption in the RPE and Bruch's barrier. The new vessels from the choriocapillaris grow up through the disruption in Bruch's. The neovascularization may (1) leak, creating an RPE detachment or sensory detachment, (2) hemorrhage or (3) form a disciform scar. All hard exudates (Coat's response) in the macula area in the absence of retinal vascular disease should alert you to the possibility of choroidal neovascular nets. Patients with suspected choroidal neovascular membranes or other signs of wet ARM should have fluorescein angiography performed within three days. It has been shown that expertly placed laser photocoagulation applied in a timely manner reduces the risk of severe vision loss in patients with wet ARM. See color plates 64 through 71 in Dr. Alexander's book.

9.) Drusens of the optic disc (Buried Drusen Of the Optic Nerve Head)- can create a diagnostic dilemma and does not represent a benign, nonprogressive condition. They can make the differential diagnosis of papilledema very difficult. Nerve head drusens are congenital and have no correlation to retinal drusens. They are calcium-like deposits which are confined anterior to the lamina cribrosa. The calcific deposits can compromise the nerve fibers and vascular supply, leading to visual field defects and peripapillary hemorrhages. Intervention therapy is currently not available to prevent the associated nerve fiber loss or hemorrhages. See color plates 11 and 12 in Dr. Alexander's book.

10.) Coats' disease is a exudative retinopathy resulting from telangiectasias of the retinal vessels. Telangiectasia is a Greek term meaning "dilation of capillaries and sometimes of terminal arteries producing an angioma of macular appearance." Coats' disease usually occurs unilaterally in the first to second decades of life. Its seen approximately four times more often in males than females, yet despite the fact that the telagiectasias are congenital, the condition usually is not discovered until the first or second decades. Over time the congenital abnormal vessels become altered leading to leakage, degeneration and development of hard exudates.

Unless the condition is caught early it usually leads to parafoveal and perifoveal exudates, retinal hemorrhages, neovascularization and loss of vision. Dr. Alexander describes the following characteristics: 1.) Occurs unilaterally in 90 percent of patients 2.) Most often in males under age 20 years 3.) No genetic association 4.) No systemic disease association 5.) Irregular dilatation of retinal vessels with a wide variation in clinical presentation 6.) May progress to intraretinal and subretinal exudate accumulation with a poor visual prognosis. Dr. Alexander's suggested management in suspected patients is fluorescein angiography to determine if the lesions that are threatening vision are treatable by photocoagulation. The earlier the disease is detected and appropriate treatment administered, the better the prognosis.

11.) Central Areolar Choroidal Dystrophy (CACD) has been described as having autosomal dominate and autosomal recessive inheritance patterns and some are sporadic cases. The earliest fundus changes are bilateral RPE mottling in and around the macula. There is progressive atrophy of the RPE and choriocapillaris within a sharply outlined zone around the fovea. Clinically the appearance is one of atrophy of the choriocapillaris loss of the RPE and atrophy of the sensory retina.

The main symptom of this condition is reduced vision from age 30 to 40 with a slow progression to 20/200 or worse with aging. Loss of color vision and central scotomas are related to the degree of impairment. Peripheral vision remains intact and there is no complaint of night blindness.

12.) Macular holes have a somewhat confusing etiology. It is generally considered that any condition that precipitates cystoid macular edema may result in the development of a macular hole. The presence of a posterior vitreous detachment (PVD) may lead to tugging at the macula causing the formation of a macular hole has been suggested.

Macular holes are clinically still divided into two categories , full thickness and lemellar holes. The classic full thickness hole is usually 1/4 to 1/3 disc diameters in size. It has a reddish color surround by a grayish edematous appearing cuff of retinal tissue and there are yellowish deposits in the base of the hole. The full thickness hole will cause significant reduction in visual acuity and a central scotoma. Lamellar holes do not have the characteristic reddish color of a full thickness hole. The patient with a lamellar hole will present with slightly reduced vision and metamorphopsia. For suspected macular holes that appear questionable or uncertain in nature or do not lend themselves to a clear diagnostic observation, consider the Watzke-Allen test. A vertical beam of light is presented to the fovea, slit lamp beam with a fundus lens or a direct ophthalmoscope. Ask the patient if the line is uniform or broken in the center-patients with macular compromise report a broken line. Those with a pseudohole might report the line as complete, but centrally distorted. See color plates 77 & 78 in Dr. Alexander's book.

13.) Papilledema is defined as optic nerve head edema secondary to increased intracranial pressure. The main cause of optic nerve head swelling is blockage of the axoplasma transport and the blockage occurs at the lamina cribrosa. The optic nerve head can swell to the extent where it is extended forward into the vitreous as well as laterally. This lateral swelling causes the retina to buckle inward at the temporal aspect of the optic nerve head. The buckling is know as Paton's folds and results in a enlarged blind spot. The acute rise of intracranial pressure results in papilledema, sometimes called a choked disc, flame shape hemorrhages, engorged veins, and cotton-wool soft exudates. There are most certainly varying degrees of papilledema depending on the what is causing the rise in intracranial pressure and what stage in this compromise the clinician sees the patient.

Symptoms will vary depending the degree of optic nerve head swelling and the how long the condition has been present. Headaches might start out like any common headache but as the condition reaches the chronic stage they may be severe enough to cause vomiting. In the chronic stage transient loss of or blurring of vision may occur lasting 5 to 30 seconds. I must say it sure seems longer than 30 seconds. There are no signs of optic nerve conduction defects such as the Marcus Gunn pupil (afferent pupillary defect) APD or color desaturation until optic atrophy occurs. Papilledema should be considered a life treating condition and any patient with suspect optic nerve head edema should be referred to a neurologist who must run either a CAT scan or MRI or both.

OTHER SLIDES WHICH WERE PRESENTED

14.) Retinitis pigmentosa

15.) Advanced Glaucoma

16.) Drusens of the macula

17.) Melanocytoma

18.) Medullated nerve fibers

19.) Bear tracks

20.) Bergmeister's papilla

21.) Staphyloma

22.) Coloboma of nerve head

23.) Branch artery occlusion

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