In vivo dynamic light scattering measurements in the cornea of the human eye prior to and after excimer laser refractive surgery

Purpose. Dynamic light scattering (DLS) can be used as a non-invasive optical probe for in vivo molecular diagnostics in the human eye. The purpose of this pilot study is to demonstrate the detectability of changes in the molecular structure of the human cornea after excimer laser photorefractive keratectomy (PRK) or phototherapeutic keratectomy (PTK). Material and Methods. 10 patients underwent excimer laser treatment, either for the correction of myopia (PRK) or for therapeutic reasons (PTK). DLS measurements of the corneal stroma were performed prior to and after (immediately, 1 day, 5, 10 days, 1 month, 3 months) treatment. Measurements were perfomed at different topographical locations both inside and outside the treated areas of the corneal stroma. Results. The autocorrelation function obtained from the DLS signal exhibits two peaks corresponding to the fast and slow components of the stroma. After excimer laser treatment the location as well as the amplitude of these peaks were significantly altered. These alterations did not correlate to the ablation depth during treatment nor to the pre-operative refractive error. Only minor corneal haze was observed which showed no statistically significant correlation with alterations of the peaks. No formation of corneal scars was observed in any patient. Conclusions. DLS seems to be a suitable tool for observation of the wound healing processes in the cornea after treatment by excimer laser. Due to the limited number of cases, statistically significant results are not yet available. Ongoing investigations involving a larger number of cases may reveal the power of DLS for diagnosis of abnormal healing processes.