Human Eyes and Vocabulary Quiz

Avenous means 'lacking veins' or 'without veins'. The prefix 'a-' means without, and 'venous' relates to veins. Option A is correct.

Aboral means 'opposite to' or 'away from the mouth' in biological contexts. The prefix 'ab-' means away from, and 'oral' refers to the mouth. Option D is correct.

Iridology (Option A) is the study of the iris of the eye. The term comes from 'iris' (the colored part of the eye) and '-logy' (study of). While Option A has a slight typo missing the 'y', it's clearly the intended answer.

Avifauna refers to the birds of a particular region, habitat, or geological period. The term combines 'avi' (bird) and 'fauna' (animal life). Fish, mammals, and insects have their own collective terms (ichthyo fauna, mammalian fauna, entomofauna respectively).

Aureity refers to properties or characteristics of gold. The word derives from 'aurum' (Latin for gold), which is also the source of the chemical symbol Au. It does not mean water-like, calmness, or general purity.

Diabetic retinopathy is indeed a leading cause of blindness in adults in the United States. High blood sugar levels damage blood vessels in the retina over time, leading to vision loss. This makes the statement true.

Shark corneas have been studied and used in experimental eye surgery due to their structural similarities to human corneas and their refractive properties. Shark corneas are thick and have unique adaptations that make them interesting for ophthalmological research.

The human eye can distinguish approximately 500 shades of gray, making option D correct. This is a well-established fact in human visual perception - the eye can detect subtle differences in luminance across this range.