Increasing age and elevated IOP are common risk factors for glaucoma development and progression, but these two measures have historically been analyzed independent of each other. Looking into the potential association between the two, a recent study in Investigative Ophthalmology & Visual Science found that age appears to play a significant role in the relationship between IOP and glaucomatous loss as it pertains to RNFL thickness change over time. The research team also reported that older patients may be more susceptible to disease progression than those who are younger with the same IOP levels.
The study offered the following example of how disease progression may differ based on age: a 40-year-old average glaucoma patient with a mean IOP of 12mm Hg had an expected rate of RNFL thickness change of -0.43µm per year, which was similar to that of an 80-year-old patient with similar clinical characteristics (-0.49µm per year). However, with an IOP of 24mm Hg, the 40-year-old patient would have a rate of RNFL loss of -0.78µm per year, but the 80-year-old would progress at a rate of -1.34µm per year, or 72% faster. These gap would continue to widen over time if IOP were to consistently rise, the investigators explained.
The retrospective cohort study enrolled glaucoma suspects and patients. The study included 85,475 IOP measurements and 60,026 SD-OCT tests performed on 14,739 eyes. Subjects were followed from four to 10 years.
The average rate of change in RNFL thickness was -0.70µm per year. The researchers noted a significant interaction between age and the rate of RNFL loss with a constant IOP, with older eyes having significantly faster rates compared with younger eyes with the same IOP. Additionally, the study reported the effect of IOP on rates of change was greater in the inferior and superior regions of the optic disc.
These findings corroborate previous research that found aging may increase the vulnerability of the optic nerve to IOP-related damage, and also suggest that older patients may require more IOP control to prevent disease progression, the study authors concluded in their paper.
Jammal AA, Berchuck SI, Thompson AC, et al. The effect of age on increasing susceptibility to retinal nerve fiber layer loss in glaucoma. Invest Ophthalmol Vis Sci. 2020;61(13):8.