Refraction and Retinoscopy Flashcards

During retinoscopy, if the examiner works at 67 cm, what working distance lens should be subtracted from the gross retinoscopy finding?

Answer: +1.50 D

At 67 cm working distance, the vergence of light from that distance equals +1.50 D, which must be subtracted from the gross finding.

A patient's manifest refraction is −3.00 +1.50 ×090. What is the spherical equivalent?

Answer: −2.25 D

Spherical equivalent = sphere + (cylinder/2) = −3.00 + (1.50/2) = −3.00 + 0.75 = −2.25 D.

Which retinoscopy reflex motion indicates that the eye is corrected and the far point coincides with the examiner's peephole?

Answer: Neutralization (no motion)

Neutralization occurs when no movement of the reflex is seen, meaning the far point is at the examiner's working distance.

In plus-cylinder notation, a refraction of −2.00 −1.00 ×180 converted to minus-cylinder form is:

Answer: −3.00 +1.00 ×090

Transpose by adding cylinder to sphere (−2.00 + (−1.00) = −3.00), change cylinder sign (+1.00), and rotate axis 90° (090).

A patient with high myopia shows a bright, fast retinoscopy reflex. This indicates the reflex is:

Answer: Against motion, requiring minus lenses

High myopes have their far point in front of the examiner, producing an against motion reflex that is neutralized with minus lenses.

What does the term 'fogging' accomplish during subjective refraction?

Answer: It relaxes accommodation by initially over-plusing the patient

Fogging uses excess plus power to blur the patient's vision, relaxing accommodation so the starting point avoids over-minus.

When performing retinoscopy on a patient with high astigmatism, a 'scissors' reflex is sometimes seen. What is the best approach?

Answer: Use a cylindrical lens to neutralize each principal meridian separately

Scissors motion indicates irregular astigmatism or high regular astigmatism; neutralize each meridian independently with cylinder correction.