Optic Disc Drusen Prevalence Substantial in Patients With Normal Tension Glaucoma

The prevalence of optic disc drusen (ODD) in patients with normal tension glaucoma (NTG) is higher than in the general population, and a low cup/disc ratio correlates with the presence of ODD, according to research published in Acta Ophthalmologica.

Researchers conducted a prospective cross-sectional study to evaluate the prevalence of ODD and optic nerve head (ONH) morphology in patients diagnosed with NTG.

The study included 195 eyes of 98 patients with NTG (62% women and 38% men; mean age 71.5±8.5 years). Both eyes of patients underwent dense enhanced depth imaging optical coherence tomography volume scans of the ONH to examine the presence of ODD. The researchers used radial ONH scans to evaluate parameters such as scleral canal diameter, cup/disc ratio, and cup depth.

The researchers found ODD in 6.1% of patients (in 3.6% of eyes), compared with 1.8% to 2.0% previously reported in the general population. The eyes with ODD had lower cup/disc ratios than eyes without ODD (0.44 vs 0.81; P =.040) and less prominent cup depths (236.6 vs 437.8 μm; P =.041). They reported no significant difference in scleral canal diameter between eyes without and those with ODD (1602 vs 1492 μm; P =.057).

“Interestingly, we found that the occurrence of ODD was associated with a smaller cup/disc ratio,” according to the researchers. “Therefore, we recommend that patients diagnosed with NTG and a cup/disc ratio <0.5 are further examined using [enhanced depth imaging optical coherence tomography] of the ONH to prevent possible misdiagnosis.”

Limitations of the study included the relatively small sample size and potential lack of participation by participants with severe NTG due to loss of vision, comorbidities and practical limitations.