Purpose
Both cataract and glaucoma are common in the elderly population and often seen together but little is known about the association between the two. This study evaluates the incidence and risk factors of cataract among glaucoma patients and the association with glaucoma drugs.
Methods
The incidence of cataract among all types of glaucoma patients, and the association with glaucoma treatment was evaluated using the electronic medical databases of Maccabi Healthcare Services, a 2 million member health maintenance organization in Israel, serving 25% of the population with a nationwide distribution. Collected data included demographics, diagnosis according to the International Classification of Diseases, 9th revision, Clinical Modification diagnostic codes, medication use and persistence, procedures and intraocular pressure (IOP). Members with incident glaucoma diagnosed between 2003 and 2010 and controls with cataract in the same time period were included.
Results
The risk for cataract increased significantly with age among incident glaucoma patients (n= 4841) and controls (n=2,126,315). For each age group the likelihood of developing cataract was higher among glaucoma patients than in controls. The likelihood of developing cataract was significantly higher in all types of glaucoma and the highest risk was in exfoliation glaucoma [Relative Risk=4.6 (95% CI 4.31-4.96)]. Baseline IOP at time of glaucoma diagnosis was significantly (HR=1.3, p<0.0001) associated with increased risk for cataract, i.e. for every 10 mmHg increase in IOP the risk for cataract increased by 30%. The cumulative exposure rate for glaucoma drugs was significantly higher ( HR=1.49 (95% CI:[1.44,1.55]) among glaucoma patients who developed cataract as compared to those without cataract (ANOVA p<0.001). In the multivariate Cox model age, glaucoma type and IOP were found statistically significant yet the adjusted hazard ratio for the cumulative exposure rate was hardly modified HR=1.43 (95% CI:[1.36,1.50]) by the adjustment.<br />
Conclusions
This study revealed that all types of glaucoma are associated with increased risk of cataract. Increased age, elevated baseline IOP and type of glaucoma specifically exfoliation glaucoma were risk factors for developing cataract. Increased cumulative exposure to glaucoma drugs increased the risk for cataract among glaucoma patients