This Taiwanese study proposed a time-varying statistical model for predicting the risk of regression toward myopia after laser in situ keratomileusis (LASIK).

Researchers analyzed 615 eyes of 311 patients derived from a retrospective cohort who underwent LASIK in 2003. They recorded refraction outcomes at one day, one week and one, three, six, nine and 12 months or longer after LASIK. They used a cross-validated design to split data into trained (308) and validated (307) data sets. These data sets were then used in an interval-censored model to predict the probability of regression toward myopia and to assess the predictors including demographic features and preoperative and postoperative variables.

Myopia regression was observed in 164 (26.7 percent) of 615 eyes during the follow-up period of 12 months or longer after LASIK. Significant predictors for myopia regression after LASIK included preoperative manifest spherical equivalent, mean preoperative central corneal curvature, size of optic zone, undercorrection and age. The risk of regression toward myopia after LASIK increased rapidly within one month, slowed down between one and six months and became steady after six months, regardless of risk group. The risk of myopia regression up to six months after LASIK was 21 percent in average-risk eyes (based on all eyes).

The authors of this study believe that this interval-censored model may be useful not only for predicting the probability of myopia regression after LASIK, but also for identifying the evolution of patients within low, moderate and high-risk groups.

This investigation by researchers at Stony Brook University School of Medicine, NY, and Johns Hopkins University evaluated risk factors for definite open-angle glaucoma (OAG), based on African-descent participants of the Barbados Eye Studies.

Eighty-one to 85 percent of patients participated over nine years of follow-up; investigators evaluated 3,222 persons at risk (age 40 to 84 years old) who did not have definite OAG at baseline. All had standardized study visits at baseline and after four and nine years, with structured interviews and blood pressure (BP) and other measurements. The ophthalmic protocol included automated perimetry, applanation tonometry, fundus photography and comprehensive ophthalmologic examinations for those referred. Central corneal thickness (CCT) was measured in a subset at the nine-year examination. Incidence was estimated by the product-limit approach; relative risk ratios (RRs) with 95 percent confidence intervals (CIs) were based on Cox regression models with discrete time.

Over nine years, 125 participants developed definite OAG (incidence, 4.4 percent; 95 percent CI, 3.7 to 5.2). Baseline factors influencing risk were age; family history of glaucoma; higher intraocular pressure; lower systolic BP and lower ocular systolic, diastolic and mean perfusion pressures. Thinner CCT was also associated with OAG incidence.

The authors maintain that this is the first report of risk factors for long-term OAG incidence, and they point out that it is also based on a sizable number of new cases. The findings suggest a multifactorial etiology of OAG and suggest that similar risk factors apply across populations. Results are relevant for understanding OAG causation and identifying groups at high risk.