Eye Have a Problem

I kind of hesitated to upload this, because it's a bit disturbing and a lot of people in the fandom have a low tolerance for gory stuff . . . although really it's just medical, not horror. Decided to play it safe and give it a warning. It doesn't bother me, but, well, I'm weird.

This started out because I noticed a lot of people using incorrect medical terminology when describing derped eyes, and while I'm one of those obnoxiously nerdy nitpickers I don't enjoy correcting people so I thought I'd make a little chart. Aaaaaand it got out of hand. As these things so often do.

Anyways, the first row covers strabismus. The first one depicts normal eyes, esotropia = one eye deviates inwards (crosseyed), exotropia = one eye deviates outwards (wall-eyed), hypotropia = one eyes deviates down, hypertropia = one eyes deviates up. You're usually not going to see two of these conditions one person (Derpy is usually exhibiting hypertropia).

The next row covers conditions that change the color of the eyes. Ocular albinism is a lack of pigment that only effects the eyes - there are different levels of severity, I've shown the eyes with no pigment at all. Heterochromia means "different colors". In complete heterochromia, one eye is a different color (usually due to partial albinism or a similar lack of pigment), in sectoral heterochromia the eye is mottled with two different colors (here, yellow and green). Aniridia is when the iris fails to develop, meaning the eye is all pupil and looks black. Anisocoria refers to uneven sizes of the pupils - by the way, David Bowie has anisocoria. People seem to think his eyes are two different colors, but that's not true. One eye was injured when he was a kid, and the iris is paralyzed so the pupil doesn't contract, and this gives it the appearance of being darker than the other one. Google a good close-up and you'll see both eyes are light blue.

Next row covers developmental anomalies. Microphthalmia means one eye is smaller than the other. In Anophthalmia the eye completely fails to develop. Unilateral means it affects one eye, bilateral means it affects both. The next two conditions are due to problems with signalling molecules in the developing embryo. Cyclopia is a rare and very severe form of holoprosencephaly in which the head fails to form properly. You've probably seen pictures online of cyclopic kittens and other animals - it's the most visible part of a birth defect that's incompatible with survival. Hypertelorism is the opposite defect, a very broad face, and in its most severe the developing body gets so confused two faces or even two heads form. This is a survivable condition. Polycoria means there is more than one pupil in the iris.

The last row show some common injuries or illness that affect appearance. Hyphema is also called an eight ball injury. The eye turns partially or completely black when blood fills up the front chamber. Cataracts cloud the lens, causing impaired vision. Interestingly, cataract surgery is one of the oldest surgeries known - it was performed by the ancient Greeks, Egyptians, Babylonians, Indians and Chinese. Ocoulomotor nerve palsy is damage that paralyzes the eye (unlike strabismus, where the eye can still move but just not co-ordinate with the other eye). I've depicted third nerve palsy. Conjunctivitis is an inflammation of outer surface of the eye and inner surface of the eyelids - we've probably all had it from pink eye or an allergic reaction. And last but not least is proptosis, or luxation of the eye. I've shown the eye displaced a bit more than usual.

And there you go . . . learn anything?