A myope has a far point at 50 cm in front of the eye. Assuming the spectacle plane is at the far point (no vertex distance correction needed), what is the refractive error of this eye?

• A -0.50 DS
• B -2.00 DS ✓
• C -1.50 DS
• D -3.00 DS

Explanation

The far point of a myopic eye is the point conjugate to the retina when accommodation is relaxed. Refractive error in diopters is the reciprocal of the far point distance in meters: power = -1 / 0.5 = -2.00 D. The negative sign indicates myopia. A common error is forgetting to convert 50 cm to 0.5 m or omitting the negative sign.

Reference: Clinical Optics

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Written and medically reviewed by the StethoPrep medical team.