Diurnal variations of keratometry and refraction after ICRS

Within a European evaluation, we participated in the study of ICRS on low m yopia. During the period of observation, subjective refraction variations i n the day were underlined. This phenomenon remains to be specified. Material and method : Thirteen eyes were included in the study, 3 were expl anted because of under-correction. The minimum follow-up is one year for al l eyes. The same observer measured refraction and keratometry in all eyes o n the same day at 9:00 am, 1:00 p.m. and 7:00 p.m., with the same automatic autokeratorefractometer. To validate the analysis method, these patients w ere compared with a group of emmetropic control eyes never operated on and with a group of eyes operated on with a PRK for similar myopia. All measure ments were done under the same conditions. Results: After one year, a tendency to evening myopisation was noticed in I CRS eyes and confirmed by the objective keratometry study showing variation s closely correlated with the myopia observed. These phenomena were not obs erved in the two other groups. Discussion: The examination technique was validated by the absence of varia tion observed on normal eyes. The tendency to diurnal myopisation is rather constant on the whole population studied with a more or less important deg ree from patient to patient. These observations never reported in the liter ature, deserve to be confirmed on other sites. Conclusion : In this study ICRS allowed to correct low myopia with a satisf actory predictability up to -3.50 D. However, the appearance of an evening myopisation recalls that observed after radial keratotomy. Complementary st udies are necessary to explain the intimate mechanism of this phenomenon.