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Ophthalmology. 2000 Oct;107(10):1950-4.

Effect of stimulus size on static visual fields in patients with retinitis pigmentosa.

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  • 1Retina Foundation of the Southwest, Dallas, Texas, USA.

Abstract

PURPOSE:

To determine the effect of stimulus size on sensitivity of patients with retinitis pigmentosa (RP) as measured by automated static perimetry.

DESIGN:

Comparative case series.

PARTICIPANTS:

Thirty-nine patients with RP and a control group of 10 healthy volunteers.

METHODS:

Automated static perimetry (full threshold programs 24-2 or 30-2) was performed twice on one eye of each participant using stimulus sizes III (0.43 degrees diameter) and V (1.72 degrees diameter). Data from the same 50 test locations were used from each field.

MAIN OUTCOME MEASURES:

At each location, for each participant, the size effect was computed as the difference (in decibels) in sensitivities for sizes V and III, and the average sensitivity was computed as the mean of sensitivities for the two sizes.

RESULTS:

For both patient and control groups, the size effect was negatively correlated with average sensitivity (r(2) > 0.124; P: < 0.001). The mean size effect was significantly greater for the patient group than for the control group: 8.6 (+/- 3.6) dB versus 5. 4 (+/- 2.2) dB (t = 18.0; P: < 0.001). The percentage of abnormal locations (more than 8 dB below mean normal) tended to be lower for size V than for size III, with a mean of 67% for size V versus 95% for size III. The percentage of absolute defects was also lower for size V than for size III, with a mean of 35% for size V versus 54% for size III.

CONCLUSIONS:

In damaged regions of the visual fields of patients with RP, increase in stimulus size from III to V can produce abnormally large increases in perimetric sensitivity. Size III may be more useful than size V for detection of field abnormality, whereas size V may be more useful than size III for observing progression of advanced RP.

PMID:
11013205
[PubMed - indexed for MEDLINE]
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