Vaajanan and colleagues report on the incidence of visual impairment from glaucoma using a Finnish registry. The registry is based on submitted data from treating doctors, and categorizes visual impairment as mild, moderate, or severe as well as near total or total blindness. Categorization is based on central visual acuity except for severe visual impairment and blindness which include constricted visual fields as part of the diagnosis. While the registry is based on World Health Organization definitions, how one interprets the visual field criteria is to some degree subjective (what exactly is ≥ 5 degrees and < 10 degrees from central fixation), and what is the "main cause" of visual impairment? The definitions have not changed over the last 40 years. Since Finland has a national health system that provides medication coverage, "treated" glaucoma patients were defined as those receiving glaucoma medications.
The incidence of any visual impairment among treated glaucoma patients (using the definition of receiving medications paid for by insurance) was relatively stable at around 2.5 per 100,000 until the last decade when it increased to nearly 3.5, largely due to an increasing number of individuals in the 85+ age range with visual impairment and glaucoma. The mean age of onset of visual impairment increased from about 74 in men and 76 in women to about 78 in men and 82 in women in the most recent decade. Using life expectancy estimates, the authors report that despite longer life expectancy, the average duration of visual impairment in persons with glaucoma is shorter owing to later age of diagnosis of visual impairment. This can in part be explained by better identification of early disease leading to better outcomes as well as improved treatments preventing substantial vision loss.
These data provide support for the benefit of our current treatment paradigms in delaying visual impairment from glaucoma
These data provide support for the benefit of our current treatment paradigms in delaying visual impairment from glaucoma. That said, one must ask, how reliable are the registry data? Defining glaucomatous visual impairment by visual acuity is problematic as central vision is rarely involved until very late in glaucoma. Defining visual field visual impairment is also tricky. Many with "treated" glaucoma may not be on medication if they have had surgery or laser treatment to control IOP. Also, as populations age many other diseases may contribute to vision loss, most notably macular degeneration in this Nordic population, and visual impairment may not have been from glaucoma in some registered cases. Studies to validate the registry would be welcome.
In summary, visual impairment from glaucoma, when treated, is relatively uncommon in this Finnish registry, and efforts to identify glaucoma and treat it appropriately appear to have reduced the duration of living with visual impairment from glaucoma despite longer life expectancy.