What value is subtracted from the sphere power in the Mohindra calculation?

• A. 0.50 D
• B. 1.25 D
• C. 2.00 D
• D. 0.25 D

Answer: (B)

Mohindra calculations subtract a fixed 1.25 diopters from the sphere power obtained during retinoscopy at a 50 cm working distance to estimate the cycloplegic refractive error in infants without using dilating drops. This constant comes from empirical calibration to account for the partial accommodation and the dark-room, near-refraction conditions of the technique, bringing the result closer to what the refraction would be under cycloplegia. The other values don’t fit this method: 0.50 D is too small a correction, 2.00 D reflects the simple working-distance correction for 50 cm in standard retinoscopy (not what Mohindra uses), and 0.25 D is also not the correct fixed adjustment.