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Optic Disc Pit!



Congenital defects arising from failure of fetal fissure closure in embryogenesis

Mostly unilateral. 10-15% bilateral

No gender predilection


PATHOPHYSIOLOGY:

-Occur due to incomplete closure of the optic fissure resulting in a micro-communication between the subarachnoid space and the pit.

-Communication of optic pits and Cerebral Spinal Fluid (CSF) is controversial and Beta-2 Transferrin levels (found in CSF) of submacular fluid associated with optic pits has been variable.

-Histologically, there is herniation of a dysplastic retina into the subarachnoid space through a defect in the lamina cribrosa at the pit.



SYMPTOMS:


-Usually asymptomatic.

-Found on routine examination incidentally.

-Patients may complain of metamorphopsia, micropsia, blurred or decreased vision, or a blind spot if the optic pit is associated with a serous detachment.


SIGNS:

-Usually found inferotemporally within the nerve, ⅓ are central.

-Appear as a round or oval depression that differs in colour from the surrounding disc (grey, yellow or black).

-Colour variation depends on the amount and location of glial tissue in the pit.

-Size can vary from 0.1-0.7 disc diameters and depth from 0.3-0.5 diopters.

-Associated macular edema, serous macular detachment; schisis or pigmentary changes in the macula.

-Shallow serous macular detachments can be seen in upto ¾ eyes with inferotemporal pits

-Source of the retinal fluid in optic disc pit maculopathy is controversial; the reports in literature describe it to be vitreous, cerebrospinal fluid, and even in some cases fluid from blood vessels in the pit.


INVESTIGATIONS:

-OCT: to determine if trace amounts of subretinal fluid is seen, can show schisis-like separation between inner and outer retina.

-Visual fields – Enlarged blind spot, arcuate scotomas .

-Amsler grid can be used to monitor the onset of macular involvement of an optic pit with serous detachment.


MANAGEMENT:

-No medical therapy indicated unless it is associated with optic disc maculopathy


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