Myopia may be a risk factor for glaucoma progression and specifically in patients with primary open-angle glaucoma, a research team from India suggests.

Their study, published in Optometry and Vision Science, also found both retinal nerve fiber layer (RNFL) and visual field progression rates were faster in myopic glaucomatous eyes that had an axial length of 26.5mm or greater. Still, the researchers note that the small difference that supports high myopia as a risk factor for progression does not indicate the clinical importance or significance of axial length.

The prospective, observational cohort study analyzed 245 eyes of 135 glaucoma patients who were followed for about six years. All subjects had RNFL imaging and standard automated perimetry done on both eyes during the same visit every four months for at least 60 months.

The researchers found the rate of change for average RNFL thickness and visual field index was -0.29μm/y and -0.30%/y, respectively, after adjusting for age, axial length, intraocular pressure, baseline RNFL thickness, signal strength and correlation between fellow eyes.

Additionally, axial length, as a continuous variable, was not associated with the rates of change of average RNFL thickness and visual field index. However, high myopic eyes with axial lengths of 26.5mm or more had an average rate of change in RNFL thickness of 0.16μm/y compared with eyes with shorter axial lengths. Similarly, myopic eyes with an axial length of 26.5mm or more were associated with a 0.21%/y faster rate of visual field index reduction.

Myopic eyes with primary open-angle glaucoma may benefit from regular measurements, and axial length should be included in clinical decision-making, the researchers noted.