Systematic Assessment of Clinical Methods to Diagnose and Monitor Diabetic Retinal Neuropathy

Table 4

Number of studies with functional investigations demonstrating evidence of change in pre- or early diabetic retinopathy.

Functional tests	Compelling	Moderate	Weak	No evidence despite investigation
Colour vision	39	11	5	0
Visual acuity	14	5	0	4
Contrast sensitivity	35	8	3	1
Dark adaptation	5	1	0	0
Pupillometry	4	0	0	0
Luminance threshold	5	1	0	0
Scotopic threshold response	4	2	0	1
Nyctometry	0	1	1	1

The tests fulfil the functional assessment that imaging modalities lack and can lend some compelling weight to further retinal damage. However, there is far more variation in the strength of evidence for pre-retinopathic diabetic disease because the psychophysical margins of change at early stages are so small. Contrast sensitivity and colour vision tests have ample compelling and indicative evidence for inclusion into retinal neuropathic inquiry.