Introduction
Unilateral pigmentary retinopathy is a rare genetic disorder causing degenerative changes in the photo-sensitive cells of the retina in the eye. Pigmentary retinopathy can be unilateral or bilateral; among them, unilateral is rare and difficult to diagnose. Difficulty in reading and focusing on an object and loss of night vision are some of the shown symptoms. Detailed genetic history of the patient is necessary to diagnose unilateral pigmentary.
What Is Unilateral Pigmented Retinopathy (UPR)?
It is used to describe a group of inherited degenerative disorders of the retina in one eye. It causes progressive damage to the photoreceptors of the retina. Atrophy and cell death of photoreceptors and the adjacent layers of the retina. Rods and cones are the primary photoreceptor cells affected.
What Is the Prevalence of Unilateral Pigmentary Retinopathy?
Unilateral pigmented retinopathy affects only one eye. Pigmentary retinopathy can affect both eyes. Rare genetic disorder with a prevalence of one in 4000 people, with less than 100 cases reported.
What Is the Cause of Unilateral Pigmentary Retinopathy?
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A genetic disorder caused by multiple gene defects. It can be inherited as autosomal dominant, autosomal recessive, or X- linked recessive disorder.
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Other causes include:
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Infections like congenital rubella, toxoplasmosis, syphilis, and Lyme disease.
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Autoimmunity-associated retinopathy, cancer-associated retinopathy.
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Trauma from a foreign body and blunt trauma can cause retinal detachment.
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Drug toxicity from Chloroquine, Hydroxychloroquine, Phenothiazine, and Thioridazine.
What Is the Physiological Process Associated With the Unilateral Pigmentary Retinopathy?
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The pigmentary changes cannot predict the type of retinopathy. The changes that lead to unilateral pigmentary retinopathy are intra-retinal pigment deposition, depigmentation of the retinal pigment epithelium, irreversible damage to the retinal ganglion cells, and vessel attenuation.
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The changes occur depending on the stage of the disease.
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The photoreceptor cell death by apoptosis leads to bone spicule formation.
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Retinal pigment epithelial cells are mislocalized and partially seal the contacting vessels. The degenerative changes in the outer cornea and the formation of the extracellular matrix deposits are other physiological changes associated.
What Are the Symptoms of Pigmentary Retinopathy?
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Night blindness - Difficulty seeing in poor lighting or dark.
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Decreased ability to see the central side or peripheral vision.
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Difficulty in reading printed papers.
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Glare.
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Difficulty in figuring out detailed images.
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Only one eye is affected; the other eye is functionally normal.
How Is Pigmentary Retinopathy Diagnosed?
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Clinical Methods - Clinical examination of the eye includes various tests to evaluate vision and to check for any diseases.
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Fundus Autofluorescence Test - Provides proper visualization of the fundus and changes associated with retinopathy. It shows mottling of retinal pigment epithelium, formation of bony spicules, punched-out atrophic lesions, and waxy pallor on the optical disc.
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Physical Examination - It includes visual acuity assessment and examination of the fundus or inside surface of the eye.
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Visual Field Examination - The loss of peripheral vision is commonly associated with pigmentary retinopathy.
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Perimetric Examination - It is the systematic measurement of visual field function. This test is done to identify certain patterns of vision loss.
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Electroretinographic (EVG) Diagnosis - This measures the electric response of light-sensitive cells, rods, and cones of the eye. EVG is done to determine inherited or acquired diseases of the eye.
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To diagnose unilateral pigmentary retinopathy, the patient needs to be monitored for a long period by doing the perimetric, clinical, and EVG diagnostic tests. Also, unilateral or bilateral pigmentary retinopathy is verified through these tests.
Diagnostic Criteria of Francois’s and Verriest for Unilateral Pigmentary Retinopathy:
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Functional changes and fundoscopic appearance typical for primary pigmentary degeneration must be present in the affected eye.
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Symptoms of retinal degeneration must be absent in the fellow eye with a normal ERG (Electroretinography).
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An inflammatory, infectious vascular cause in the affected eye must be excluded.
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The observation period must be long enough, over five years, to rule out the possibility of asymmetric inherited pigmented retinopathy.
Diagnosis of Unilateral Pigmentary Retinopathy Associated With Ocular Toxoplasmosis:
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Ocular toxoplasmosis is an eye infection caused by a parasite. This disease condition causes inflammation of the eye. Individuals presenting with ocular toxoplasmosis and unilateral pigmentary retinopathy show retinal dystrophy and pigmentary changes. The associated changes are night blindness, loss of visual field, and changes in electroretinography.
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These clinical findings make the condition similar to retinitis pigmentosa (RP). This striking similarity between retinitis pigmentosa and pigmentary retinopathy makes the diagnosis difficult.
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Retinitis pigmentosa is an inherited genetic disorder. It affects photoreceptors cells of the retina. In some clinical cases, ocular toxoplasmosis can lead to pigmentary retinopathy and mimics unilateral pigmentary retinopathy.
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To diagnose and confirm the clinical condition, careful analysis of the patient's medical history is done. Along with that, fundus examination, ocular imaging, laboratory tests, and genetic tests are carried out.
What Are the Treatment Options for Unilateral Pigmentary Retinopathy?
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Pigmentary retinopathy, being a genetic and inherited condition, does not have any proven method for treatment.
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Supportive treatment is the standard care provided.
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Antioxidants, vitamins, and nutritional supplement therapies can be done to improve the health of the eye and vision.
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Low visual aids are used to help people with poor vision. The various low visual aids are
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Electric video magnifiers.
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Standing and hand-held magnifiers.
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Strong magnifying reading glasses.
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Loupes.
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Small telescopes.
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Cystoid macular edema (CME) is an associated syndrome with UPR. CME occurs due to blockage of the blood vessels in the retina, causing a retinal thickening. This can result in permanent vision loss. Medical treatment includes the use of steroid or non-steroid eye drops. Other drugs are given to reduce swelling. Laser therapy can be done to repair the damaged blood vessels.
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Treatment of cataracts associated with UPR. Cataract causes clouded lenses and impaired vision. Cataracts are best treated with surgery. During surgery, the clouded lens is replaced with a clear artificial lens to improve vision.
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Medical follow-up is important to assess the progression of the disease. In unilateral cases, the unaffected healthy eye should be monitored.
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Annual ocular examinations have to be carried out.
Conclusion
Unilateral pigmentary retinopathy is a rare genetic disorder causing the degeneration of photo-sensitive cells of the retina. True unilateral pigmentary retinopathy is difficult to find. Many retinopathy cases associated with secondary causes are also reported. A clear personal and familial history will help in the diagnosis of unilateral pigmentary retinopathy. Over time genetic mutations occur in the gene causing unilateral pigmentary retinopathy. The genetic mutation can show different clinical manifestations in different individuals with the same genetic condition.
