In Nott's retinoscopy, neutrality is seen at 50 cm with the target 40 cm from the patient. What is the resulting lead/lag of accommodation?

• A. +0.50D lag
• B. +10.00D lag
• C. -0.50D lead
• D. -10.00D lead

Answer: (A)

In Nott's retinoscopy, you judge how much the eye is accommodating by comparing the near demand of the target with the actual accommodation the eye is using at the retinoscopy plane. Neutrality is achieved when the eye’s accommodation matches the optical demand at the working distance of the retinoscope.

Here, the near target is at 40 cm, so the accommodative demand is 1 / 0.40 = +2.50 diopters. Neutrality is seen with the retinoscope at a working distance of 50 cm, so the eye is actually accommodating 1 / 0.50 = +2.00 diopters. The eye is under-accommodating by 0.50 D relative to the near demand, giving a lag of +0.50 diopters.

So, the accommodative lag is +0.50 D.