Abstract
Abstract: :
Purpose: To evaluate the possibility of reducing nasal artifact in the peripheral visual field by turning the head nasally. Methods: The central 30o and the peripheral 30–60o visual fields were obtained with and without a nasal head turn (in random order) with the Humphrey automated perimeter (programs 30–2 and 60–4 respectively) in one eye of 20 normal volunteers and 31 glaucoma patients. A nasal head turn was defined as a 30 degree rotation of the head resulting in abduction of the tested eye and movement of the nose away from the fixation point. Forty–three subjects were able to complete all four visual field protocols, and the remaining subject data were excluded. Glaucoma was diagnosed after a complete eye examination based on abnormalities in the visual field, the optic disc, or both. Estimates of the cup–to–disc ratio were recorded and all exams were performed by an observer masked to the visual field data. Results: The mean age was 38 years (SD 14) in normal subjects and 55 years (SD 10) in glaucoma subjects. The normal subjects were 45% male, and the glaucoma subjects were 29% male. The mean cup–to–disc ratio was 0.31 (SD 0.15) in normal subjects and 0.61 (SD 0.19) in glaucoma subjects. The change in the mean visual field threshold associated with a head turn was +0.1 in the periphery and –0.4 centrally in normal subjects, and was –0.9 in the periphery and –0.4 centrally in glaucoma subjects (all p > 0.1; Negative values indicate less sensitivity). However, for four points along the inferonasal border of the 60–4 peripheral visual field, there was higher sensitivity with the nasal head turn (p < 0.05). In univariate linear regression analysis of the mean threshold, the proportion of variance (r2) in the cup to disc ratio explained was 0.32 for the 60–4 field with the head turn, 0.31 for age, 0.30 for the routine 30–2 field, 0.26 for the 30–2 field with the head turn, and 0.25 for the routine 60–4 field (all p<0.001). In stepwise backwards multivariable linear regression to predict the cup–to–disc ratio (r2 = 0.44), the significant independent predictors were age (p=0.004) and mean threshold in the peripheral visual field with the head turn(p=0.003). Conclusions: For the central 30o Humphrey visual feld exam a nasal head turn is not helpful. However, for examintion of the 30–60o field, a nasal head turn may increase sensitivity. Because the technique reduces nasal artifact, it should be investigaed futher as a method of improving sensitivity and reproducibility of automated peripheral field exams.