City Research Online

Abstract

The screening efficiency of tests of visual acuity, colour vision, contrast sensitivity and central visual field in screening for Diabetic retinopathy (DR) was assessed (STUDY 1). ROC curve analysis and Bayesian test predictive values revealed the Composite Pseudoisochromatic Plate (Comp PIC) test of colour vision comprising 8 red—green Ishihara plates and 7 tritan plates, to be the most efficient test of all tests evaluated. For the screening of DR the test was 0.51 sensitive and 0.83 specific; whilst when used for screening of DR and/or other ocular complications the figures were 0.64 and 0.83, respectively. The performance of the other tests, when evaluated on their own, was unsatisfactory. When evaluated as a test battery the 3-test battery comprising the Comp PIC, Vistech VCTS 6000 and Amsler grid gave poorer results for the screening of DR alone (sensitivity=0.41 & specificity=0.83) when compared to the results obtained for the screening of DR and/or complications (sensitivity=0.72 & specificity=0.71).

In STUDY 2, tests of colour vision, contrast sensitivity and visual field were assessed for their ability to grade the severity of visual dysfunction in patients with 3 clinically- defined grades of DR. Two tests were identified as being most appropriate for the purpose: the same Composite plates described earlier and the Standard Pseudoisochromatic Plates Part 2; the former was able to distinguish "significant DR" from mild DR while the latter was able to distinguish "referrable DR" (i.e. proliferative DR needing laser treatment) from mild and moderate DR. These two tests were also least affected by age and VA of the patients.

Two studies were carried out to investigate the effects of laser panretinal photocoagulation treatment for DR on the following visual functions: Visual acuity, colour vision, contrast sensitivity and visual field. In STUDY 3 the comparative effects on visual function of three treatment modalities for proliferative DR (Argon 488/514nm; DYE-577nm; DYE-595nm) were investigated. Transient central field deterioration was noted for all three treatment modalities; this corresponded to the areas lasered. A mild and transient effect on colour vision was observed with the Argon 488/514nm which manifested as an increase in the blue-yellow partial scores on the Farnsworth-Munsell 1 1 100-Hue test. Overall there were not any clinically significant differences in the effects on the visual functions amongst the 3 treatment modalities tested. In STUDY 4, a visual function assessment was made on patients with extensive Argon laser panretinal photocoagulation (range 4,100 to 10,402). Patients were found to have a higher prevalence of tritan colour vision defects and some inner (zones 10 degrees inwards) visual fields losses when compared to a group with untreated pro1iferative DR. Relationships between visual function deficits and the amount/intensity of treatment were found to be unexpected; this included negative relationships for colour vision & contrast sensitivity defects.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > RZ Other systems of medicine
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses Doctoral Theses

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