[Diurnal variations of refraction and keratometry after intracorneal rings]

Within a European evaluation, we participated in the study of ICRS on low myopia. During the period of observation, subjective refraction variations in the day were underlined. This phenomenon remains to be specified.

Thirteen eyes were included in the study, 3 were explanted because of under-correction. The minimum follow-up is one year for all eyes. The same observer measured refraction and keratometry in all eyes on 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 were 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 measurements were done under the same conditions.

After one year, a tendency to evening myopisation was noticed in ICRS eyes and confirmed by the objective keratometry study showing variations closely correlated with the myopia observed. These phenomena were not observed in the two other groups.

The examination technique was validated by the absence of variation observed on normal eyes. The tendency to diurnal myopisation is rather constant on the whole population studied with a more or less important degree from patient to patient. These observations never reported in the literature, deserve to be confirmed on other sites.

In this study ICRS allowed to correct low myopia with a satisfactory predictability up to -3.50 D. However, the appearance of an evening myopisation recalls that observed after radial keratotomy. Complementary studies are necessary to explain the intimate mechanism of this phenomenon.