Predicting undetected glaucoma according to age and IOP: a prediction model developed from a primarily European-derived population.

ABSTRACT

PURPOSE: To model prediction of undetected glaucoma in a predominantly white population, based on intraocular pressure (IOP) and subject age. METHODS: In 1992-1997, a population screening for glaucoma was performed at Malmö University Hospital where individuals between 55-79 years of age (n = 46 614) living in Malmö, were invited to a free eye health examination. Recently examined patients were not invited (n = 4117). IOP and age were recorded for all screened subjects. Subjects who screened positive were further examined to establish or reject a glaucoma diagnosis. We performed multiple regression analysis of the combined effect of age and IOP on the likelihood of undetected glaucoma. RESULTS: In all, 32 918 subjects attended the screening (77.5% of invited), 22 218 women and 11 700 men, while 9579 refrained from participation. Glaucoma was diagnosed in 406 subjects. The proportion of subjects with glaucoma increased exponentially with increasing IOP and older age. Still, the majority of subjects with glaucoma (57%) had ≤IOP 21 mmHg. The predicted rate of undetected glaucoma was low, <5%, for subjects with IOP <25 mmHg, but rose rapidly with higher IOP, reaching 81% in the group with IOP >35 mmHg and age 75-79 years. The model fit well to the data (R2  = 0.97). CONCLUSION: We created a model estimating the combined effect of IOP and age on the likelihood of undetected glaucoma. The model may facilitate case-finding in European-derived populations. Despite the important impact of IOP on the risk of glaucoma, a large proportion of subjects with undetected glaucoma had IOP ≤ 21 mmHg.