Normal Tension Glaucoma Predicted By Microvasculature Dropout

Baseline microvasculature dropout (MvD) and lower laminar deep vessel density (VD) predict a higher risk of conversion to normal tension glaucoma (NTG) among NTG suspects, according to research published in the American Journal of Ophthalmology. 

Researchers enrolled 307 patients (eyes, 307; mean age, 53.18±15.26 years; 63.5% women) who were NTG suspects in the multicenter prospective cohort study. All participants had an intraocular pressure (IOP) within normal limits, a suspicious optic disc without retinal nerve fiber layer (RNFL) defects, and a normal visual field (VF). The study objective was to investigate the role of vessel parameters in identifying NTG suspects at risk of NTG development.

Researchers measured laminal VD in the intradisc region using optical coherence tomography-angiography (OCT-A). The NTG suspects progressed to full NTG status upon identifying a new localized RNFL defect in the superotemporal or the inferotemporal region or a glaucomatous VF defect.

In total, 23.8% of patients converted to NTG during a mean follow-up period of 59.84±12.44 months. The MvD rate in patients who converted to NTG status during follow-up was 50.7% compared with 6.4% in patients who did not progress to NTG status (P <.001).

Both macular deep VD and laminar deep VD values were significantly lower among patients who progressed to NTG status (P =.006 and P =.004, respectively), and MvD and decreased laminar deep VD were correlated with NTG conversion.

“These findings suggest that analyzing the [optic nerve head] using OCT-A could reveal mechanistic differences related to NTG development,” according to the researchers. “Additionally, OCT-A can be used to identify NTG suspects more susceptible to NTG development due to the presence of MvD and the status of the deep laminar VD.”

Study limitations include the exclusion of eyes with suspicious glaucomatous findings and strict criteria for defining NTG conversion.