Vision and Ophthalmology Optics and Refraction 2

Question 1

A patient has +2.00 sphere, -1.00 cylinder, axis 90. What is the power at the 180-degree meridian?

Accepted Answer

+1.00 D

Answer

The cylinder power acts at 180° (perpendicular to axis 90), so the power at 180° is the sphere (+2.00) plus the cylinder (-1.00) = +1.00 D.

Question 2

Which instrument measures the refractive error of the eye by detecting the direction of the reflected light reflex?

Accepted Answer

Retinoscope

Answer

Retinoscopy uses a streak or spot retinoscope to observe the reflex from the patient's fundus, allowing objective determination of refractive error.

Question 3

The principal of 'against motion' in retinoscopy indicates which refractive error?

Accepted Answer

Myopia greater than the working distance

Answer

Against motion (reflex moves opposite to the retinoscope movement) indicates myopia that exceeds the working distance lens equivalent.

Question 4

The corneal power (in diopters) is primarily due to which interface?

Accepted Answer

Air-tear film interface

Answer

The air-tear film (air-cornea) interface provides approximately 48 D of the eye's total ~60 D of refractive power due to the large difference in refractive indices.

Question 5

Which refractive condition is present when the eye is too short (axial) or the cornea too flat?

Accepted Answer

Hyperopia

Answer

Hyperopia occurs when the eye is too short axially or the corneal/lenticular power is too weak, causing parallel rays to focus behind the retina.

Vision and Ophthalmology Practice Test

Vision and Ophthalmology Practice Test

Vision and Ophthalmology Optics and Refraction 2