In the minus lens method, which statement is true regarding working-distance correction?

• A. It does not require any correction
• B. It requires adding +2.50D for the working distance
• C. It requires adding +3.50D for the working distance
• D. It requires subtracting 2.50D for the working distance

Answer: (B)

Working-distance correction in the minus lens method is about compensating for the fact that the test distance is closer than infinity. You add the reciprocal of the working distance to the measured refraction so the result reflects what the eye would need at infinity. For a standard working distance of 40 cm, that correction is +2.50 diopters, so you add +2.50 D to obtain the distance-corrected result. If a different working distance were used, you’d add 1 divided by that distance in meters. The other options don’t fit because they either omit this correction or use the wrong magnitude or sign.