Pre-operative factors influencing post-operative outcomes from MyoRing implantation in keratoconus.

BACKGROUND: To identify pre-operative factors that influence post-operative performance of a full-ring intra-corneal implant (MyoRing) for the management of keratoconus. METHOD: In a retrospective study, medical records of 70 keratoconus eyes of 70 consecutive surgical patients with a mean age of 28.54 ± 6.52 years, who underwent MyoRing implantation using the PocketMaker microkeratome (Dioptex GmbH), were included and analysed before implantation and for visual outcome. Variables assessed included age, gender, keratoconus shape, uncorrected distance visual acuity, corrected distance visual acuity, spherical equivalent and keratometry reading. After the last follow-up, the eyes were graded for MyoRing implantation performance into worst, moderate and best subgroups. RESULTS: The mean values of uncorrected distance visual acuity, corrected distance visual acuity, spherical equivalent, manifest sphere and cylinder improved significantly post-operatively (p < 0.05). A statistically significant difference was found in the mean spherical equivalent (p = 0.046) and uncorrected distance visual acuity (p = 0.001) between moderate and best subgroups. No statistically significant correlation was found between age, sex, keratoconus shape, keratometric values, corrected distance visual acuity and visual outcome. CONCLUSIONS: According to this new grading system for MyoRing implantation performance, pre-operative uncorrected distance visual acuity and spherical equivalent are considered as the most important indicators for surgical performance in MyoRing treatment of keratoconus.