Purpose:
The International Society for Geographical and Epidemiological Ophthalmology (ISGEO) has developed a definition of glaucoma based on the 97.5th and 99.5th population percentile of vertical cup disc ratio that can be used in epidemiologic studies. The ISGEO criterion is increasing used and correlates well with clinical glaucoma. In this study the ISGEO criterion are used to develop estimates of over and under diagnosis of glaucoma in the United States.
Methods:
Data from the 2005-2006 and 2007-2008 National Health and Nutrition Examination Survey (NHANES) were obtained from the National Center for Health Statistics and merged into a combined four year weighted population. As part of the NHANES medical examination fundus photographs (n=5575) and FDT visual fields (n=4547) were performed on a subsample of adults over the age of 40. Vertical cup disc ratio was measured from fundus photographs and the presence or absence of a visual field defect was determined from two visual field tests done in each eye. A modified ISGEO criterion using these results was applied and estimates of glaucoma prevalence in the United States developed. Prevalent ISGEO glaucoma (ISGEO+) was then compared to those self-reporting glaucoma or using topical medications prescribed for glaucoma (SRM+). All analyses were performed using SAS Survey 9.3 accounting for the complex sample design of NHANES.
Results:
During this period an estimated 2.4% (95%CI 1.7, 3.0) of the US population over 40 had glaucoma. Based on this prevalence rate 59.6% (95%CI 47.8, 71.4) of the US population with glaucoma is undiagnosed (SRM- & ISGEO+). In multivariate analysis comparing the undiagnosed to those jointly ISGEO+ & SRM+ only age < 65 was associated with under diagnosis (OR 8.4, 95%CI 3.8, 18.6 covariates, race, gender, SES, insurance status). Over 60% of the putative undiagnosed glaucoma was found in adults between the ages of 40-65. Over three-fourths of those who were SRM+ (75.3% 95%CI 67.0, 83.6) were ISGEO-. In multivariate analysis comparing the putatively over diagnosed to those jointly ISGEO- and SRM-, adults >65 (OR 4.0 95%CI 2.1, 7.3) and African Americans (OR 2.0, 95%CI 1.4, 3.1) had increased odds of over diagnosis.
Conclusions:
Glaucoma in the United States is highly under and over diagnosed. Younger adults appear likely to be under diagnosed, while older adults are more likely to be over diagnosed. Compared to whites African Americans were more likely to be over diagnosed.
Keywords: clinical (human) or epidemiologic studies: prevalence/incidence • clinical (human) or epidemiologic studies: health care delivery/economics/manpower • clinical (human) or epidemiologic studies: risk factor assessment