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A comparison of Goldmann III, V and spatially equated test stimuli in visual field testing: the importance of complete and partial spatial summation
- Source :
- Ophthalmic & Physiological Optics
- Publication Year :
- 2017
- Publisher :
- John Wiley and Sons Inc., 2017.
-
Abstract
- Purpose Goldmann size V (GV) test stimuli are less variable with a greater dynamic range and have been proposed for measuring contrast sensitivity instead of size III (GIII). Since GIII and GV operate within partial summation, we hypothesise that actual GV (aGV) thresholds could predict GIII (pGIII) thresholds, facilitating comparisons between actual GIII (aGIII) thresholds with pGIII thresholds derived from smaller GV variances. We test the suitability of GV for detecting visual field (VF) loss in patients with early glaucoma, and examine eccentricity‐dependent effects of number and depth of defects. We also hypothesise that stimuli operating within complete spatial summation (‘spatially equated stimuli’) would detect more and deeper defects. Methods Sixty normal subjects and 20 glaucoma patients underwent VF testing on the Humphrey Field Analyzer using GI‐V sized stimuli on the 30‐2 test grid in full threshold mode. Point‐wise partial summation slope values were generated from GI‐V thresholds, and we subsequently derived pGIII thresholds using aGV. Difference plots between actual GIII (aGIII) and pGIII thresholds were used to compare the amount of discordance. In glaucoma patients, the number of ‘events’ (points below the 95% lower limit of normal), defect depth and global indices were compared between stimuli. Results 90.5% of pGIII and aGIII points were within ±3 dB of each other in normal subjects. In the glaucoma cohort, there was less concordance (63.2% within ±3 dB), decreasing with increasing eccentricity. GIII found more defects compared to GV‐derived thresholds, but only at outermost test locations. Greater defect depth was found using aGIII compared to aGV and pGIII, which increased with eccentricity. Global indices revealed more severe loss when using GIII compared to GV. Spatially equated stimuli detected the greatest number of ‘events’ and largest defect depth. Conclusions Whilst GV may be used to reliably predict GIII values in normal subjects, there was less concordance in glaucoma patients. Similarities in ‘event’ detection and defect depth in the central VF were consistent with the fact that GIII and GV operate within partial summation in this region. Eccentricity‐dependent effects in ‘events’ and defect depth were congruent with changes in spatial summation across the VF and the increase in critical area with disease. The spatially equated test stimuli showed the greatest number of defective locations and larger sensitivity loss.
- Subjects :
- 0301 basic medicine
Adult
Male
medicine.medical_specialty
media_common.quotation_subject
partial summation
Glaucoma
Humphrey Visual Field Analyzer
spatial summation
Audiology
Summation
Contrast Sensitivity
03 medical and health sciences
0302 clinical medicine
perimetry
medicine
Contrast (vision)
Humans
In patient
Eccentricity (behavior)
Arithmetic
media_common
Mathematics
Early glaucoma
Original Articles
Middle Aged
medicine.disease
Sensory Systems
Visual field
Ophthalmology
030104 developmental biology
Sensory Thresholds
030221 ophthalmology & optometry
Visual field testing
Visual Field Tests
Original Article
Female
Ricco's area
Visual Fields
Optometry
Subjects
Details
- Language :
- English
- ISSN :
- 14751313 and 02755408
- Volume :
- 37
- Issue :
- 2
- Database :
- OpenAIRE
- Journal :
- Ophthalmic & Physiological Optics
- Accession number :
- edsair.doi.dedup.....b249389dc8825bd2e7d11b7284475d61