Purchase this article with an account.
M. W. Dul, W. H. Swanson, E. Lin, T. Lau; Diffuse Loss of Sensitivity in the Central 10 Degrees of Patients With Glaucoma: An Early Functional Finding or an Artifact of Starting Point Bias?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5510.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
In glaucoma, diffuse loss of sensitivity can be measured using the 30-2 test pattern (Henson et al, IOVS, 1999, 40:3147). We confirmed this using the 10-2 test pattern, SITA Standard algorithm (Humphrey Field Analyzer IIi, HFA; CZ Meditec, Dublin, CA) (Lin et al, AVRO, 2009). This algorithm uses patient responses and reaction time to determine the starting point thresholds which may differ between a control group and patients with existing visual field loss. To address this potential source of bias, we tested the same subjects using a Contrast Sensitivity Perimetry (CSP) protocol implemented on a monitor-based testing station with a fixed starting point and alternative algorithm (Hot et al, IOVS, 2008, 49: 3049).
We tested 32 eyes of 32 subjects, 16 POAG patients with pattern visual loss within 10 degrees of fixation and 16 controls. Each POAG eye was matched with an age-similar control eye. All subjects were experienced with perimetry, had clear media, visual acuity of 20/25 or better, and had no concomitant conditions known to affect the visual field or macular function. Locations with total deviation probability values of <5% were identified in each POAG eye, and corresponding locations were eliminated from subsequent analysis for that POAG/control pair of eyes, in order to compensate for the effects of pattern loss on the most sensitive locations. For each POAG/control pair, the ten most sensitive remaining locations for the 10-2 and CSP were sequenced by sensitivity, ten (control - POAG) threshold differences were calculated, and the average and SD of the ten differences were determined.
For 10-2, the overall average of the sensitivity difference at the ten most sensitive locations was 1.4 +/- 1.0 dB (Z > 3, p < 0.005). The SD of the ten difference values ranged from 0.2 to 0.7 dB (ave = 0.5 dB). 13 pairs were significantly greater than zero. For CSP, the average of the sensitivity difference was 1.2 +/- 1.4 Db (Z > 3, p < 0.005). The SD of the ten difference values ranged from 0.5 to 1.2 dB (ave = 0.75 dB). 11 pairs were significantly > 0. 10 pairs had both CSP and HFA significantly > 0 and no pairs were less than zero.
Glaucoma patients with pattern visual field loss within 10 degrees of fixation also exhibit diffuse loss of sensitivity. We have confirmed the findings of Henson and extended them to the central 10 degrees using two forms of macular perimetry. As the algorithm and analysis of these two devices vary, this finding is not attributable to a starting point or machine bias.
This PDF is available to Subscribers Only