Diurnal variations in keratometry and refraction with intracorneal ring segments

Purpose: To study refraction variations during the day in eyes with intrast romal corneal ring segments (ICRS) to correct low myopia. Setting: Monticelli Clinic, Marseille, France Methods: Thirteen eyes with ICRS were included in the study; the ICRS was e xplanted from 3 eyes because of undercorrection. The minimum follow-up in a ll eyes was 1 year. The same observer measured refraction and keratometry a t 9:00 AM, 1:00 PM, and 7:00 PM With the same autokeratorefractometer. To v alidate the analysis method, these eyes were compared with a group of emmet ropic control eyes that had not had surgery and with a group of eyes that h ad photorefractive keratectomy for a similar degree of myopia. All measurem ents were done under the same conditions. Results: After 1 year, the ICRS eyes showed a tendency toward an evening my opic shift. This was confirmed by the objective keratometry study, which sh owed variations closely correlated with the myopia observed. These phenomen a were not observed in the other groups. Conclusion: The ICRS had satisfactory predictability in eyes with up to 3.5 0 diopters of myopia. However, the evening myopic shift appeared similar to that observed after radial keratotomy.