Modulation transfer function and higher order aberrations with and without corneo scleral lens in an eye with keratoconus

The purpose is to describe image quality metrics such as modulation transfer function (MTF) and Strehl ratio and higher order aberration (HOA) with corneo scleral lens (CSL) in keratoconus. A 25-year-old male visited the outpatient department with a complaint of diminution of distance vision in the right eye. His best-corrected visual acuity was 6/60 and 6/6 partial in the right and left eyes, respectively. Slit-lamp examination revealed right eye keratoconus and left eye was Forme fruste keratoconus. There was a history of corneal collagen cross-linking with riboflavin in the right eye. The patient was dispensed with corneo-scleral contact lens and the left eye was managed with spectacle. Corneal HOA, MTF, and Strehl ratio were measured without and with CSL using iTrace aberrometer. A significant reduction in corneal HOA and improvement in image quality metrics were noted with CSL.