Which higher-order aberration is characteristically increased and accounts for much of the degraded retinal image quality in keratoconus?

• A Spherical aberration
• B Vertical coma ✓
• C Trefoil
• D Secondary astigmatism of the fourth order only

Explanation

The decentered inferior cone of keratoconus produces a marked increase in vertical coma, which correlates with both the severity of ectasia and the loss of contrast sensitivity. Spherical aberration rises modestly after myopic excimer ablation rather than in keratoconus. This aberration signature is why wavefront-guided treatments designed for keratoconus target coma, and why rigid lenses, by neutralising the anterior surface, dramatically reduce measured coma.

Reference: Yanoff and Duker Ophthalmology, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.