The study was done to investigate clinical characteristics and risk factors for glaucoma conversion of the contralateral eye in unilateral normal-tension glaucoma (NTG) patients.

A retrospective observational cohort study was conducted on a total of 76 subjects who had been diagnosed with unilateral NTG at the baseline and followed up for more than 5 years.

During the mean follow-up period of 7.3±2.4 years, 26.6% subjects were confirmed to have developed glaucoma in the non-glaucomatous contralateral eye. The 5-year rate of glaucoma conversion in contralateral eyes was 19.7%. The maximum width of β-zone parapapillary atrophy (MWβPPA)-disc diameter (DD) ratio at the baseline and the presence rate of disc haemorrhage during follow-up period were significantly greater in the contralateral eyes of the conversion group than in those of the non-conversion group (p=0.011, <0.001, respectively). A multivariate Cox-proportional hazard model revealed intraocular pressure (IOP) over 17 mm Hg (HR 5.05, p=0.031), CCT under 491 μm (HR 4.25, p=0.025) and MWβPPA-DD ratio over 0.32 (HR 6.25, p=0.003) in contralateral eye at the baseline as the independent risk factors for glaucoma conversion.

The study concluded that among unilateral NTG patients, those with low CCT and high MWβPPA-DD ratio as well as high IOP in the contralateral eye are more likely to develop glaucoma in that eye during long-term follow-up.