Front Surface Eccentricity Can Improve Vision, HOAs in Keratoconus

Front surface eccentricity in scleral lenses is an important consideration for improving vision, contrast sensitivity, and higher order aberrations (HOAs) in patients with keratoconus, according to research published in Eye & Contact Lens. 

Researchers included 15 patients (mean age, 26.20 years; 11 men) with varying degrees of keratoconus severity (mild, n=2; moderate, n=4; severe, n=9) in an investigation performed at a tertiary care center. The team performed corrected distance visual acuity, contrast sensitivity, and higher order aberration measurements at baseline and after 30 minutes of lens wear with scleral lenses of 3 different front surface eccentricities (FSE0=0, FSE1=0.30, FSE2=0.60). Each participant underwent random assignment to 1 of the lens eccentricities and crossed over to the other eccentricities following a washout period. 

All 3 scleral lens front surface eccentricities improved corrected distance visual acuity, the report shows. Visual acuity improved from 0.30 logarithm of the minimum angle of resolution (logMAR) to 0.10, 0.05, and 0.05 among participants while wearing the FSE0, FSE1, and FSE2 lenses, respectively (P =.01). 

Contrast sensitivity also improved from baseline while wearing all 3 scleral lens front surface eccentricities, the report shows. The FSE0, FSE1, and FSE2 lenses improved the baseline contrast sensitivity value of 1.19 to 1.54, 1.59, and 1.60, respectively. 

HOAs also improved from baseline, with each front surface eccentricity reducing root mean square (RMS) coma, RMS spherical aberration, RMS secondary astigmatism, and RMS trefoil (P <.001 for all HOA types). The FSE1 and FSE2 front surface eccentricities demonstrated a better ability to reduce HOAs compared with the FSE0 lenses, according to the report. 

“Clinicians’ understanding of the impact of eccentricities and their utilization may provide better optical quality to keratoconus patients,” according to the study authors. 

Study limitations include a small sample size, a short study duration, the use of only 1 brand of contact lenses, and failure to include individuals with ocular pathologies other than keratoconus.