Comparison of two grading methods to evaluate focal narrowing of retinal arterioles in glaucoma

Focal arteriolar narrowing has been reported to be more common in glaucoma eyes compared to normal eyes. The current study was performed to compare two methods for standardized assessment of focal arteriolar narrowing.

Stereoscopic optic disc photographs (from one randomly selected eye per subject) of 48 normal subjects, 20 ocular hypertensive patients (OHT), and 29 glaucoma patients, were reviewed independently in a masked fashion by two graders. Focal arteriolar narrowing within one disc diameter from the rim edge was evaluated based on two different grading methods: (1) narrowing present if the arteriole was wider distal to the narrowing, and (2) narrowing present if the arteriole was wider both distal and proximal to the narrowing.

Focal arteriolar narrowing was observed with grading method 1 in 37.5% (18/48), 35.0% (7/20), and 65.5% (19/29) of normals, OHT, and glaucoma patients, respectively. It was observed with grading method 2 in 18.8% (9/48), 0% (0/22), and 48.3% (14/29) of normals, OHT, and glaucoma patients, respectively. With both grading methods, focal arteriolar narrowing was significantly more frequent in glaucoma versus normal eyes (chi-square test: grading method 1 P=0.03, and grading method 2 P=0.0001). The number of eyes with focal arteriolar narrowing was significantly more frequent with method 1 than with method 2 across all photographs and all subgroups (chi-square test: P=0.0001). The overall agreement between the two graders was kappa 0.77+/-0.06 for grading method 1, and 0.43+/-0.11 for grading method 2.

The prevalence of focal arteriolar narrowing is highly dependent upon the grading method. A uniform grading method of focal arterial narrowing is needed to achieve comparable and reproducible results among studies.