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Retinitis[edit]

Retinitis is the inflammation of the retina, the thin tissue lining at the back of the eye.[1] The retina contains photoreceptors, rod, and cone cells, which are responsible for converting light into neural signals for visual recognition.[2] Retinitis may cause the degeneration of the photoreceptor cells, subsequently leading to vision impairment.[1] There are different types of retinitis such as retinitis pigmentosa (RP), cytomegalovirus (CMV) retinitis, and chorioretinitis (CR).[1] Retinitis can be caused by a variety of factors such as genetics, viral infections, and a weakened immune system.[1] Diagnosis of retinitis involves a thorough examination by an ophthalmologist.[3]

Types[edit]

Types of retinitis include retinitis pigmentosa, cytomegalovirus retinitis, and chorioretinitis.[1]

Retinitis pigmentosa is an inherited disorder leading to the progressive degeneration of the photoreceptors in the retina, typically in both eyes.[3] The inheritance of RP is considered autosomal dominant, autosomal recessive, and X-linked.[4] RP is caused by mutations in numerous genes that encode proteins that are required by photoreceptors in the retina.[4] These mutations can inhibit the production of proteins, produce abnormal malfunctioning proteins, or produce toxic proteins, all three situations cause damage to photoreceptors.[4]

Cytomegalovirus retinitis is caused by cytomegalovirus, a herpes virus.[5] Contraction of CMV does not usually cause any visible signs or symptoms of infection.[5] Once contracted, the virus is in the body permanently and stays in a temporary inactive form.[5] When CMV is activated, it spreads to the eye through the bloodstream and causes inflammation of the retina.[1][5] CMV retinitis is more common in individuals with a weakened immune system, which can arise from the following:[1][5]

Chorioretinitis affects the retina and the choroid, the vascular layer of the eye.[1][2] Chorioretinitis is typically caused by congenital, bacterial or protozoal infections such as congenital toxoplasma or cytomegalovirus.[1] If there is permanent damage to the choroid, this may block blood supply to the retina and will lead to vision loss.[1]

Symptoms[edit]

Retinitis pigmentosa:[3]

Cytomegalovirus retinitis:[5]

Chorioretinitis:[6]

Treatment[edit]

There is no known cure for retinitis pigmentosa.[3] However, prospective treatments such as vitamin A palmitate, docosahexaenoic acid, and Lutein supplements are being evaluated for their safety and effectiveness.[7]

CMV retinitis is treated through strengthening the immune system with highly active antiretroviral therapy (HAART).[5] This provides long-term management of CMV by recovering the immune function. Short-term solutions include antiviral medications such as ganciclovir, valganciclovir, or foscarnet that can be administered for a period of time as determined by a clinician.[5] Although there are various treatment options, vision loss due to CMV retinitis cannot be regained.[5]

Chorioretinitis can be treated by certain antimicrobials.[6] Depending on the cause of the chorioretinitis, antivirals, antibiotics, antifungals, anthelmintics, or antituberculous drugs can be utilized to prevent further loss of vision.[6]

Diagnosis[edit]

Diagnosis involves examinations by an ophthalmologist, an eye doctor. A visual field test, visual acuity test, and electroretinography (ERG) are used to monitor and evaluate photoreceptor function.[3][5][6]

A visual acuity test uses the standard eye chart to measure how well a person can see at various distances. Patients with retinitis typically have worse visual acuity due to vision loss.[8]

A visual field test is used to determine a patient’s central vision.[9] In the test, a patient watches a dot of light move within a designated space and uses a button to indicate when they cannot see the dot anymore. A map of their vision is constructed using the results from the test.[9] Retinitis typically results in progressive visual field loss and a visual field test can be used to locate the defects in the visual field associated with the damage to the retina.[3]

Electroretinography uses electrical signals to measure photoreceptor function.[10] A contact lens with electrodes attached is used to measure electrical activity in the retina.[10] Light is flashed into the patient’s eye and the electrodes measure the electrical activity of the rod and cone cell response.[10] A decline in electrical signal indicates photoreceptor function loss.[10]

Laboratory testing is used to diagnose the different types of retinitis. More specifically, retinitis pigmentosa is diagnosed using genetic testing as it is an inherited disease.[3] CMV retinitis is diagnosed with blood or urine tests which test for substances specific to CMV.[11] For chorioretinitis, there are a variety of tests that may be applied to confirm diagnosis such as a fundus fluorescein angiography, indocyanine green angiography, ultrasonography, or optical coherence tomography.[12]

See also[edit]

References[edit]

  1. ^ a b c d e f g h i j Yanoff, Myron; Duker, Jay (2014). Ophthalmology. Philadelphia: Elsevier Health Sciences. ISBN 9781455739844.
  2. ^ a b William, Krause (2005). Krause's essential human histology for medical students. New York: Universal Publishers.
  3. ^ a b c d e f g "Retinitis pigmentosa". American Academy of Ophthalmology. Retrieved November 20, 2016.
  4. ^ a b c Rivolta, Carlo; Sharon, Dror; DeAngelis, Margaret M.; Dryja, Thaddeus P. (2002-05-15). "Retinitis pigmentosa and allied diseases: numerous diseases, genes, and inheritance patterns". Human Molecular Genetics. 11 (10): 1219–1227. ISSN 0964-6906. PMID 12015282.
  5. ^ a b c d e f g h i j "Cytomegalovirus Retinitis". American Academy of Ophthalmology. Retrieved November 20, 2016.
  6. ^ a b c d "Chorioretinitis". Mount Sinai. Retrieved November 20, 2016.
  7. ^ "Retinitis Pigmentosa". Canadian National Institute for the Blind. Retrieved 2016-11-21.
  8. ^ "Visual acuity test". medlineplus.gov. Retrieved 2016-11-21.
  9. ^ a b Sheppard, John. "Visual Field Test". Medicinenet. Retrieved November 20, 2016.
  10. ^ a b c d "Electroretinogram". american Academy of Ophthalmology. Retrieved 2016-11-21.
  11. ^ "CMV retinitis". medlineplus.gov. Retrieved 2016-11-21.
  12. ^ Sudharshan, S; Ganesh, Sudha K; Biswas, Jyotrimay (2010-01-01). "Current approach in the diagnosis and management of posterior uveitis". Indian Journal of Ophthalmology. 58 (1): 29–43. doi:10.4103/0301-4738.58470. ISSN 0301-4738. PMC 2841371. PMID 20029144.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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