Changes in visual function under mesopic and photopic conditions after intrastromal corneal ring segment implantation for different stages of keratoconus.

Purpose: To analyze and compare the changes in visual function under mesopic and photopic conditions in different stages of keratoconus before and after Keraring intrastromal corneal ring segment (ICRS) implantation.

Setting: Clinico San Carlos Hospital and Faculty of Optics and Optometry, Complutense University, Madrid, Spain.

Design: Case series.

Methods: Keratoconic eyes were evaluated under mesopic (0.1 to 0.2 candelas [cd]/m(2)) and photopic (85 cd/m(2)) conditions. LogMAR high-contrast corrected distance visual acuity (CDVA) and low-contrast CDVA were assessed using the Bailey-Lovie test and logarithmic contrast sensitivity, using the Pelli-Robson test.

Results: The study evaluated 12 eyes with stage I keratoconus, 21 eyes with stage 2, and 14 eyes with stage 3. The mean change in photopic high-contrast CDVA was 0.16 logMAR ± 0.20 (SD) (P<.00001). Photopic low-contrast CDVA increased by a mean of 0.14 ± 0.26 logMAR (P=.0005), photopic contrast sensitivity by a mean of 0.09 ± 0.22 logMAR (P=.005), and mesopic high-contrast CDVA by a mean of 0.10 ± 0.26 logMAR (P=.03). There were no significant differences between stages. Surgery did not affect the mean changes in mesopic low-contrast CDVA or mesopic contrast sensitivity for any stage.

Conclusions: Implantation of ICRS in keratoconic eyes increased photopic high-contrast CDVA, low-contrast CDVA, and contrast sensitivity. Under low luminance, the mean changes in high-contrast CDVA, low-contrast CDVA, and contrast sensitivity did not worsen after ICRS implantation performed 5.0 mm from the visual axis, despite the rings being partially superimposed on the mydriatic pupil.