Optic Nerve Head Evaluation Without Pharmacological Mydriasis: How Reliable is it?

Abstract

Purpose: : To investigate the intra-observer and inter-observer agreement for optic nerve head (ONH) and peripapillary retinal nerve fiber layer (pRNFL) evaluation with and without pharmacological mydriasis.

Methods: : Glaucomatous patients/suspects and controls from a general outpatient clinic were prospectively enrolled. Each patient was examined before and after mydriasis by 3 glaucoma specialists in a standardized masked fashion. Undilated pupillary diameter was measured and characteristics of the ONH and pRNFL were analyzed before and after mydriasis. Intra-observer and inter-observer agreement for ONH and pRNFL evaluation were calculated. Using stereoscopic retinography as gold standard, it was also compared the ability of each examiner to identify glaucomatous signs of the ONH and pRNFL [laminar dot sign; disc haemorrhage; disc saucering; disc notching; peripapillary atrophy; Hoyt sign (pRNFL defect); violation of the ISNT rule].

Results: : A total of 60 eyes from 30 patients (mean age, 62.3 ±11.6 years) were included. Average undilated pupillary diameter was 3.5 ±0.7mm. Regarding intra-observer comparisons before and after mydriasis, greater mean values of vertical cup/disc ratio (VCDR) were found after mydriasis by the 3 examiners, reaching statistical significance for one of them (VCDR, 0.39 vs 0.44; p<0.01). While the inter-observer Kappa coefficient ranged from 0.64 to 0.72 before mydriasis, it ranged from 0.71 to 0.77 after mydriasis. Average values for within-subject standard deviation and coefficient of variation of VCDR measurements (inter-observer) were significantly reduced (less variability) following mydriasis (0.06 vs 0.05 and 0.28 vs 0.11, respectively; p≤0.03). Overall, the ability of examiners to indentify laminar dot signs and disc notchings increased significantly after mydriasis (p<0.01). Finally, undilated pupillary diameter did not correlate with the coefficient of variation of VCDR measurements (p=0.16).

Conclusions: : Undilated evaluation of the ONH may lead to underestimation of the VCDR even when performed by a glaucoma specialist. Pharmacological mydriasis not only allows the identification of a greater proportion of glaucomatous signs, but also reduces measurements variability between different examiners. This study suggests that glaucomatous patients/suspects should preferentially be examined under pharmacological mydriasis.

Keywords: optic disc • nerve fiber layer • detection