Researchers have found that nearly one-quarter of untreated patients with normal tension glaucoma and myopia experienced glaucoma progression within 5 years, despite relatively low intraocular pressure (IOP) and no prior signs of worsening disease.
Researchers at Seoul National University Bundang Hospital, led by Dong Kyun Han, MD, retrospectively analyzed 111 eyes from patients with myopic normal tension glaucoma (NTG) who hadn't received IOP-lowering treatment for at least 1 year as a result of either physician assessment of low risk or patient preference, according to their study published in the Journal of Glaucoma. Patients were followed for an average of 48.7 ± 26 months and underwent regular optical coherence tomography (OCT) and visual field (VF) testing to monitor glaucoma progression.
Progression was observed in 25 eyes (22.5%), which were classified as the progression (P[+]) group. The remaining 86 eyes (P[–]) showed no signs of progression.
Using multivariable Cox regression, the researchers identified significant predictors of progression:
- Family history of glaucoma: Hazard ratio (HR) = 2.59–3.31 (depending on model), P < .05
- Higher mean IOP: HR = 1.5 per mmHg increase, P = .005
- Higher maximum IOP: HR = 1.21 per mmHg increase, P = .039.
None of the patients with a mean IOP below 11 mmHg progressed. A Davies test identified an IOP breakpoint at 14.2 mmHg; above this level, the rate of retinal nerve fiber layer (RNFL) thinning increased significantly with IOP.
The patients in the P(+) group had a mean RNFL thinning of −1.7 ± 1.5 μm/year, whereas those in the P(–) group had a mean RNFL thinning of −0.4 ± 0.7 μm/year (P < .001). Sectoral thinning in the patients in the P(+) group was greater in the temporal, temporal-superior, nasal-inferior, and temporal-inferior sectors.
Following initiation of IOP-lowering therapy in the P(+) group, mean IOP dropped from 13.3 ± 1.4 to 12.1 ± 1.8 mmHg (P < .001), and RNFL thinning slowed (−1.2 ± 1.2 μm/year vs −1.7 ± 1.5 μm/year), but this change was not statistically significant overall. A significant reduction in thinning was also observed in the temporal-superior sector (P = .038).
No significant changes in VF mean deviation (MD) were observed in either group over the follow-up period:
- Baseline VF MD = −2.56 dB (P[+]) vs −2.18 dB (P[–])
- Final VF MD = −2.16 dB (P[+]) vs −2.48 dB (P[–]).
“Patients reporting a family history of glaucoma were more likely to be in the P(+) group or to exhibit a faster rate of RNFL thinning,” the study authors reported. “This finding is consistent with a previous study, which also found that myopic NTG suspects who progressed to NTG had a higher frequency of family history of glaucoma.” The researchers wrote that further studies with advanced tools such as risk factor assessments based on polygenic risk scores are needed.
They also noted that while axial elongation during myopia progression can increase shearing forces and scleral tension, this force decreases as axial elongation stops with aging. They found that axial length wasn't a significant factor for progressive damage. Rather, increased IOP or fluctuations in IOP were contributing factors.
The retrospective design, small sample size, and homogeneous (Korean) study population may have limited generalizability. A larger, prospective study is needed to validate these findings.
“A significant number of patients with NTG with myopia showed progressive damage even when the disease had been stable for a year without treatment. [...] Earlier initiation of treatment should be considered in myopic NTG eyes at a higher risk of progression, even when the disease seems to be stable,” the study authors concluded.