Purpose:
Automated perimetry is widely used in the diagnosis and monitoring of glaucoma. When SITA standard perimetry is combined with a second asynchronous visual detection task at fixation, additional areas of field loss are manifest in glaucoma, but there is little additional depression of the field observed in healthy subjects. We have now investigated the impact of performing an auditory detection task on SITA fields.
Methods:
One eye of 10 patients with glaucoma (mean age 71±7yrs), 10 healthy age–matched controls (71±9yrs) and 10 young controls (22±3yrs) was assessed using SITA Standard 30–2 on an HFA Series VII (model 740i). Standard visual fields (SF) were compared with the fields recorded when subjects, in addition to performing the field task, also responded to auditory stimuli (100msec bursts of white noise delivered over headphones) using a second hand–held button (modified field, MF). We compared SFs and auditory MFs by examining standard parameters returned by the perimeter (mean deviation, MD; pattern standard deviation, PSD) and threshold field values. We also recorded the response times to auditory stimuli with and without concurrent field performance.
Results:
We calculated the difference in MD between standard and modified fields (SF–MF; see Fig). While close to 0dB for both control groups it was 0.68±0.81dB for the glaucoma group. A one–way ANOVA demonstrated no significant difference between the groups. The same basic pattern was observed for PSD and threshold field values. The effect of the field task on auditory task performance was the same across the groups.
Conclusions:
These results are in contrast to the effect of a visual task where for young and old healthy groups the mean MD difference was 0.71±0.79dB and 0.80±0.70dB respectively and the difference for the glaucoma group 3.00±2.44dB (F2,42 = 12.26; p<0.001). They suggest that the effects of secondary detection tasks are modality specific and that central compensation for glaucomatous damage may be due to central visual processing resources rather than more general mechanisms such as attentional processing.
Keywords: visual fields • perimetry