Purpose-To investigate whether long-term intraocular pressure (IOP) fluctuations are a risk factor for conversion from ocular hypertension to glaucoma.
Design-Observational cohort study.Participants-The study included 252 eyes of 126 patients with ocular hypertension observed untreated as part of the Diagnostic Innovations in Glaucoma Study. At baseline, ocular hypertensive eyes had elevated IOP, normal visual fields (VFs) on standard automated perimetry, and normal optic discs as evaluated by stereophotograph assessment.Methods-Glaucoma conversion was defined as development of reproducible VF loss or optic disc damage. Analyses included all IOP measurements from the baseline visit to time of progression (for converters) and last follow-up (for nonconverters). Mean IOP and IOP fluctuation were calculated as the arithmetic mean and standard deviation (SD), respectively, of all available IOP measurements per eye.Main Outcome Measures-Univariable and multivariable Cox regression analyses were used to evaluate the association between IOP fluctuation and time to progression. Multivariable models adjusted for age, mean IOP, central corneal thickness, vertical cup-to-disc ratio, and pattern SD.Results-Forty eyes of 31 subjects developed glaucoma during follow-up. Mean IOPs during follow-up were 25.4±4.2 mmHg for the eyes that converted to glaucoma and 24.1±3.5 mmHg for the eyes that did not. Corresponding values for IOP fluctuation were 3.16±1.35 mmHg and 2.77±1.11 mmHg, respectively. Intraocular pressure fluctuation was not a risk factor for conversion to glaucoma both in univariable analysis (hazard ratio [HR], 1.30 per 1 mmHg higher; 95% confidence interval [CI], 0.76-1.96; P = 0.092) and in multivariable analysis (adjusted HR, 1.08 per 1 mmHg higher; 95% CI, 0.79-1.48; P = 0.620). Mean IOP during follow-up was a significant risk factor for progression both in univariable analysis (HR = 1.16 per 1 mmHg higher; 95% CI, 1.04-1.31; P = 0.010) and in multivariable analysis (adjusted HR, 1.20 per 1 mmHg higher; 95% CI, 1.06-1.36; P = 0.005).Conclusion-Long-term IOP fluctuations do not appear to be significantly associated with the risk of developing glaucoma in untreated ocular hypertensive subjects.Although elevated intraocular pressure (IOP) has been unquestionably demonstrated to be a risk factor for development and progression of glaucoma, 1-5 there has been controversy with regard to the IOP features that are the most relevant. Long-term (i.e., visit Both the AGIS and EMGT included only patients with definite glaucoma diagnosis at baseline. It is possible that the role of long-term IOP fluctuation as a risk factor for glaucoma development could be different than that for glaucoma progression. Two recent multicenter prospective randomized clinical trials reported on the predictive factors for conversion from ocular hypertension to glaucoma. In both the Ocular Hypertension Treatment Study 11 and the European Glaucoma Prevention Study, 12 higher IOP levels at the baseline visits were associated with a higher ...