A patient with bilateral aphakia corrected by unilateral spectacle lens reports a sense of image magnification and spatial distortion. The image size difference between the two eyes that typically becomes symptomatic is approximately:
- A 1 percent
- B 3 percent ✓
- C 10 percent
- D 25 percent
Correct answer: B. 3 percent
Explanation
The normal binocular system tolerates an interocular image size difference of about 3 percent; beyond this aniseikonia produces symptoms such as asthenopia, diplopia and spatial distortion. A unilateral aphakic spectacle produces roughly 25 to 30 percent magnification, which is grossly intolerable, so contact lens correction reducing the difference to about 7 percent is preferred. One percent is within physiological tolerance and ten percent is far above the symptomatic threshold.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.