RETINA

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RETINA
Retinitis Pigmentosa
An inherited disorder of pigment epithelium and receptor cells (recessive, dominant or x-linked inheritance)
Clinical Findings
- Night blindness, constricted visual fields                                                RP
- Often good central vision, but constricted fields
- Retinal pigmentation – bone spicule
- Optic atrophy and retinal artery attenuation
- Electroretinogram is abnormal from an early age- before there is any other evidence of abnormality erg information

Management
No therapy is available at present
But research is evaluating a variety of Genetic therapies which offer promise for the future

Associated disorders
- Refsum’s Syndrome – R.P., deafness, elevated blood phytamic acid
- Bardet Biedl Syndrome – R.P., & obesity metal retardation, hypogonadism,
- Ushers syndrome – R.P. & deafness

Macular Dystrophies
Stargardt's Macular Dystrophy – decreased vision, pigmentary macular change (“beaten- bronze” appearance) with or without yellow fleck deposits. Recessively inherited.
Diagnosis Confirmed with Pattern ERG

Vitelliform Macular Dystrophy
– an “egg yolk appearance” at the macula. Dominantly inherited.
Diagnosis Confirmed Normal ERG but abnormal EOG

Retinopathy Of Prematurity
Infants born prematurely have an incompletely vascularized retina. The exposure of this immature retina to high oxygen concentrations may result in abnormal vascular development.

In the acute phase an arterio-venous mesenchymal shunt is present in the peripheral retina at the junction of the vascularized and non-vascularised zones. This may be visible ophthalmoscopically as an elevated ridge.

If the condition progresses intravitreal fibrovascular proliferation may occur progressing even to an exudative retinal detachment.
Ophthalmic Review:  Infants at risk require ophthalmic examination . Those at risk are – less than 1000 gms at birth, severely ill babies, especially babies who required supplemental oxygen.
Treatment: with laser or cryopexy can control these changes in most infants.

Chronic changes secondary to contracture of this fibrovascular tissue may result in retinal folds, dragging of the optic disc, and even traction retinal detachment. This retinal detachment and fibrous tissue can be seen as a white retrolental opacity – retrolental fibroplasia.

Supplemental oxygen levels should be restricted to a that level which is adequate to maintain cerebral and other vital functions.  Arterial oxygen levels must be monitored.  But even with the greatest care retrolental fibroplasia still occurs. Improved paediatric care has resulted in changing the goalposts. In 1980 babies of 2000gm or less required review. Today children of birthweight greater than 1000gm rarely are found to be significantly affected.