Retinitis Pigmentosa
Asmaa Riad El-Sayed Ahmed;
Abstract
Retinitis pigmentosa refers to a heterogeneous group of inherited retinal diseases that cause degeneration of rod and cone photoreceptors, it affects 1in 3,500 to 1 in 4,000 people in the United States and Europe.
RP can be inherited in autosomal dominant pattern which has the best prognosis, mutation in the RHO gene is the most common cause, it tends to appear at around 30 years of age.
Autosomal recessive pattern in which the prognosis is more worse, mutation in the USH2A is the most common cause, it tends to show first signs between 30 and 40 years.
X-Linked pattern which has the worst prognosis, mutation in the RPGR and RP2 genes are the most common causes, vision is affected severely and can result in very poor vision by the age of 40.
The photoreceptors undergo apoptosis which result in reduced outer nuclear thickness of the retina, the pigment deposits (bony spicules) result from RPE degeneration and RPE migration into the neural retina in response to photoreceptors cell death.
Night blindness is the first symptom the patient notice which occurs between childhood and the age of 30, then loss of the peripheral visual field, in late stages RP patients have a restricted visual field, by the age of 50 patients suffer from affection of the central vision.
By fundus examination there is pigmentary deposits resembling bony spicules initially found in the peripheral retina, attenuation of retinal vessels, waxy pallor optic disc and various degrees of retinal atrophy.
Antenatal diagnosis can be performed in families in which the responsible gene has been identified.
ERG shows dramatic diminution in a- and b-wave amplitudes, m ERG detects focal changes in retinal function , as RP progress the response densities measured in the macula and pericentral retina are greatly reduced , EOG is typically reduced in RP.
Visual field assessment shows patchy loss of the peripheral vision up to ring shape scotoma and eventually tunnel vision, fluorescein angiography shows peripheral retinal vascular leakage, OCT shows different degrees of defect of the IS/OS junction and the presence of hyper reflective foci in the inner nuclear layer, outer nuclear layer and subretinal space.
Genetic testing is of potential value in clinical diagnosis such as sagner sequencing, microarray technology, arrayed primer extension, high resolution melting analysis.
Low visual aids may be very helpful for patients, they include:
1) Portable illumination devices such as image intensifiers and wide-angle mobility lamp.
2) Near vision magnification devices such as handheld magnifiers, stand magnifiers and spectacle lenses which are used for near tasks.
3) Distance vision magnification devices such as handheld telescope, spectacle mounted telescope and behind the lens telescope which are used for distant tasks.
4) Electronic magnification such as microcomputer screen, closed-circuit television and low vision enhancement system.
Vitamin A is recommended for RP patients who should take Vit.A 15,000IU/day, omega-3 may be helpful in treatment, lutein supplementation 12 mg/d slowed loss of mid peripheral visual field among adults with RP taking vit.A and acetazolamide 250mg bid may be helpful in RP patients with cystoid macular oedema.
Visual rehabilitation using microelectronic visual implant in which it stimulates electrically the retina, they include cortical prosthesis, optic nerve prosthesisand retinal prosthesis which are categorized as epiretinal, subretinal and extraocular.
Gene therapy represents the most promising therapeutic option, researchers typically deliver new genes to cells using modified virus vectors, as viruses have evolved as preferred vectors to deliver genetic materials to cells. Adeno-associatd virus is the best virus vector to be used.
RP can be inherited in autosomal dominant pattern which has the best prognosis, mutation in the RHO gene is the most common cause, it tends to appear at around 30 years of age.
Autosomal recessive pattern in which the prognosis is more worse, mutation in the USH2A is the most common cause, it tends to show first signs between 30 and 40 years.
X-Linked pattern which has the worst prognosis, mutation in the RPGR and RP2 genes are the most common causes, vision is affected severely and can result in very poor vision by the age of 40.
The photoreceptors undergo apoptosis which result in reduced outer nuclear thickness of the retina, the pigment deposits (bony spicules) result from RPE degeneration and RPE migration into the neural retina in response to photoreceptors cell death.
Night blindness is the first symptom the patient notice which occurs between childhood and the age of 30, then loss of the peripheral visual field, in late stages RP patients have a restricted visual field, by the age of 50 patients suffer from affection of the central vision.
By fundus examination there is pigmentary deposits resembling bony spicules initially found in the peripheral retina, attenuation of retinal vessels, waxy pallor optic disc and various degrees of retinal atrophy.
Antenatal diagnosis can be performed in families in which the responsible gene has been identified.
ERG shows dramatic diminution in a- and b-wave amplitudes, m ERG detects focal changes in retinal function , as RP progress the response densities measured in the macula and pericentral retina are greatly reduced , EOG is typically reduced in RP.
Visual field assessment shows patchy loss of the peripheral vision up to ring shape scotoma and eventually tunnel vision, fluorescein angiography shows peripheral retinal vascular leakage, OCT shows different degrees of defect of the IS/OS junction and the presence of hyper reflective foci in the inner nuclear layer, outer nuclear layer and subretinal space.
Genetic testing is of potential value in clinical diagnosis such as sagner sequencing, microarray technology, arrayed primer extension, high resolution melting analysis.
Low visual aids may be very helpful for patients, they include:
1) Portable illumination devices such as image intensifiers and wide-angle mobility lamp.
2) Near vision magnification devices such as handheld magnifiers, stand magnifiers and spectacle lenses which are used for near tasks.
3) Distance vision magnification devices such as handheld telescope, spectacle mounted telescope and behind the lens telescope which are used for distant tasks.
4) Electronic magnification such as microcomputer screen, closed-circuit television and low vision enhancement system.
Vitamin A is recommended for RP patients who should take Vit.A 15,000IU/day, omega-3 may be helpful in treatment, lutein supplementation 12 mg/d slowed loss of mid peripheral visual field among adults with RP taking vit.A and acetazolamide 250mg bid may be helpful in RP patients with cystoid macular oedema.
Visual rehabilitation using microelectronic visual implant in which it stimulates electrically the retina, they include cortical prosthesis, optic nerve prosthesisand retinal prosthesis which are categorized as epiretinal, subretinal and extraocular.
Gene therapy represents the most promising therapeutic option, researchers typically deliver new genes to cells using modified virus vectors, as viruses have evolved as preferred vectors to deliver genetic materials to cells. Adeno-associatd virus is the best virus vector to be used.
Other data
| Title | Retinitis Pigmentosa | Other Titles | التهاب الشبكية الصباغى | Authors | Asmaa Riad El-Sayed Ahmed | Issue Date | 2015 |
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