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.