In the Reduced Eye model, what is the index of refraction inside the eye?

• A. 1.333
• B. 1.0
• C. 1.5
• D. 1.2

Answer: (A)

In the Reduced Eye model, the interior of the eye is treated as a single medium with a refractive index that matches the ocular fluids, about 1.333. This value represents the combined refractive effects of the aqueous and vitreous humors, which are largely water-based with dissolved substances giving a slight elevation above 1.0. Using this internal index (roughly 1.333) allows the model to simplify the eye to one internal medium in contact with an external medium of air (index ~1.0), making it easier to calculate focal properties from a single refracting boundary. If you used a much different internal index, like 1.0 or 1.5, the predicted refractions would not align with how light actually bends at the eye’s interfaces. The option around 1.2 is also not representative of the typical ocular fluids. Therefore, 1.333 best matches the internal ocular media.