Abstract
Purpose: :
To investigate 4 variants of multifocal pupillographic perimetry in glaucoma to further explore the effects of balancing the stimulus luminances across the visual field to match the sensitivity of the pupillary field.
Methods: :
Following a smaller scale experiment (Kolic et al. ARVO 2009 submitted) we tested 40 normal and 39 glaucoma subjects to further explore the effects of luminance balancing. All eyes were examined with HFA achromatic, SWAP and Matrix 24-2 perimetry and Stratus OCT. Visual fields were classified by HFA mean defects: moderate: 6 to 12 dB, severe: >12 dB. Glaucoma subjects had a moderate or severe visual field in at least one eye. All subjects gave informed written consent. Multifocal stimuli having 44 test regions/eye, extending to 30 deg eccentricity, were presented concurrently to both eyes using a prototype of the TrueField Analyser. Recording duration was 4 minutes, divided into 8 segments of 30 s. Pupil diameter was monitored under infrared illumination. The 4 stimulus protocols examined differed in terms of mean presentation intervals (MPI) of 1 or 4 s per region, and balancing strategy. The balancing strategies assumed stimulus/response functions of the form R=Sz where z was 0.5 or 0.66. The peak test luminances were 150, 290 or 340 cd/m2. The backgrounds were 10 cd/m2. Almost all subjects were tested twice with the 4 stimulus variants. Diagnostic performance was assessed by areas under ROC curves (AUCs) for the N-worst response amplitudes.
Results: :
For all visual field severities the best AUCs were produced by a stimulus having MPI=4 s, luminance 150 cd/m2 and z=0.5. For severe fields the mean of the 20 regional amplitudes that most deviated from the normative data gave an AUC of 0.978 ± 0.012 (mean ± SE), and for combined moderate and severe fields 0.862 ± 0.038.
Conclusions: :
Careful balancing of the stimuli to cater to differences in field sensitivity, minimized the effects of response saturation, as characterised by the exponent z, and improved the diagnostic efficiency of pupillographic multifocal perimetry. The pupillographic method eliminates several problems associated with conventional subjective perimetry.
Keywords: perimetry • visual fields • pupil