OP - The Optics of Retinoscopy - Week 8

Question 1

What is the purpose of retinoscopy?

Answer 1

Objectively determine the refractive state of the eye.

Question 2

When is retinoscopy used?

Answer 2

As a starting point, and refined with subjective refraction.

Question 3

When may retinoscopy be the only tool? Name 4.

Answer 3

• Stroke patients
• Intellectually impaired
• Young children
• Low vision patients

Question 4

Describe how a retinoscope works.

Answer 4

Clinician views small patch of light reflected off retina,

through small hole in a mirror.

Question 5

How is the refractive error of an eye determined using retinoscopy?

Answer 5

By placing trial lenses in front of patient’s eye, until patient’s retina is focused on sight hole in mirror.

Question 6

Where is the point of focus in a myopic eye vs a hyperopic eye?

Answer 6

Myopic - in front of the retinoscope.
Hyperopic - behind the retinoscope.
(From the clinician’s perspective)

Question 7

Describe the formula for speed of the reflex, and describe how neutralisation can be achieved.

Answer 7

Equation is
(W - X) / (W + K)
W is working distance (D)
X is the vergence
K is the refractive error
As K equals -W, speed is infinite