Abstract
Purpose::
This study was a preliminary investigation of a means of concurrently assessing the visual fields of both eyes by recording the responses of both pupils to dichoptically presented multifocal stimuli, to investigate the sensitivity and specificity of this as a method for objective perimetry for glaucoma.
Methods::
Dichoptic stimulation was provided via a pair of stereoscopically arranged LCD displays. The subject thus saw a single cyclopean stimulus. Each display presented a circular dart-board-like array of 24 stimulus regions extending to 30 deg eccentricity. Each region in each eye received stimulus presentations at a mean rate of 1/s. Four stimulus presentation conditions were tested: each stimulus region containing either a single or a 2x2 array of patches, being presented either steady for 133ms or flickered half-on half-off at 15 Hz for 266ms. For each of the 4 tests the recording duration was 4 minutes, divided into 8 segments. The 20 normal subjects were given a thorough eye exam including HFA achromatic 24-2 fields (SITA) and fundus photography assessed by a single skilled observer. The 26 patients had stable HFA fields. All subjects gave written consent in accordance with the Helsinki Declaration and ANU Human Ethics Protocol 238/04.
Results::
Both pupils were recorded with 24 regions mapped in each eye, giving a total of 96 responses measures/subject from each 4 minute record. The regressive analysis method meant that about 10% of each record could be lost due to blinks etc. without affecting accuracy, e.g.[1,2]. The median peak contraction amplitudes expressed as z-scores for the 4 conditions were 4.1, 3.3, 3.2 and 2.3. The best diagnostic performance was obtained by taking the mean of the 10 worst deviations from the normal profile across the visual field regions, providing a joint sensitivity and specificity of 85% for the flickered single patch condition.
Conclusions::
The pupillographic multifocal method provided diagnostic accuracy that was comparable to standard perimetry although the raw test time was equivalent to 2 min per eye. Measuring the visual fields of the two eyes simultaneously has statistical advantages for comparing the two eyes. Unlike perimetry the method provides both sensitivity and temporal dynamics for each visual field region. Other experiments also presented at this meeting further confirm these results.1 James, AC et al. (2005) Visual Neurosci 22, 45-542 James, AC (2003) Invest. Ophthalmol. Vis. Sci. 44, 879-90
Keywords: visual fields • pupillary reflex