medicine

[clachries]

a partial loss of vision or isolated blind spot within the normal visual field

[forgetfultel]

Scotoma

[connundro]

"Amblyopia",is the medical term for a partial loss of vision-isolated blind spots can result from "cataracts".

[biley]

Scotoma is perhaps the more likely answer.

amblyopia, noun impaired sight without any apparent damage to the eye.

scotoma, noun an area of abnormal or absent vision within the visual field, a blind spot due to disease of the retina or optic nerve:
plural scoto'mata or scoto'mas.

Chambers dictionary.