Intolerable Nighttime Dysphotopsias After Intra-Corneal Ring Segment Implantation.

To describe the managment of dysphotopsias after implantation of intra-stromal corneal ring segment (ICRS) in a patient with large mesopic pupil of 7.9 mm

Case Report

34 years old male patient previously diagnosed with keratoconus in both eyes, presented with extensive halos and glare in both eyes, more in the left side. Cross-linking and ICRS were performed 8 years ago. Since then, he has been complaining of inability to drive at night. CDVA in the left eye was 0.9 (-1.50D -2.0D X45). Pentacam, OPD and itrace were done and showed two ICRS implanted at 5 mm optic zone. Mesopic pupil was of 7.9 mm in diameter which explaned the patient's complaint. After a thorough discussion with the patient, decision was made to remove both rings in a two-step approach. After removal of the first ring on March 2021, the symptoms improved and CDVA was 0.9 (-2.50D -0.75D X165). After a long follow up period of 18 months, the patient  was still unable to drive at night and insisted on removal on the second ring. The second ICRS was explanted on Decembre 2022. Q value increased from -0.9 to -1.6 with CDVA of 0.3. Two months later, visual rehabilitation started by topo-guided PRK and sumtaneous crosslinking to minimize corneal HOAs. One month post-operatively, CDVA was 0.8 (-6.0D -2.0D X160) and the patient could drive clearly with no halos or glare. Glasses could not precribed because of lare anisomotropia. The patient was happy with soft contact lenses and is scheduled for phakic IOL implantaion.

Decision of implantation of ICRS should be weighted against the potenital induced nighttime halos and glare. Mesopic pupil measurment is of utmost importance before taking the decision.