The paper reviews evidence that before any change in diabetics' fundi, changes occur to blood flow, ERG and visual functions. In the case of colour vision and contrast sensitivity, the changes are partially reversed by breathing oxygen, and therefore are the result of retinal hypoxia. There are also other evidences that hypoxia is a major factor in the development of diabetic retinopathy (DR). Therefore in diabetics with early retinopathy, but normal photopic vision, functional disturbance might appear in dark adaptation, since in such circumstances, (as shown by Linsenmeier and his colleagues) the already low retinal PO2 markedly decreases. This hypothesis has been tested and results consistent with the hypothesis (and with a number of older reports) have been obtained. The significance of this finding to early DR is discussed, and a mechanism suggested whereby prolonged periods of hypoxia during dark adaptation could generate changes in retinal capillaries. Such periods occur each night, and their elimination in diabetics could be therapeutic.

These findings suggest that accurate measurements of RG and YB colour thresholds can provide a sensitive measure of functional change in diseases of the retina with patterns of loss that differ significantly in AMD and diabetes.

Aim: To provide a simple test that detects the onset of age related maculopathy (ARM), and can be used to monitor its severity. Methods: Colour contrast sensitivity was measured using computer graphics techniques. Colour thresholds were measured along tritan and protan colour confusion axes in the presence of dynamic luminance noise. Thresholds were determined separately for two sizes of optotypes (6.5˚and 1.5˚). Natural pupils were used. Normal values for the test have been established. Results: In all patients with unilateral age related macular degeneration, the smaller optotype was invisible in that eye and in almost all, the larger optotype could not be seen. In the symptomless fellow eyes (with ARM) the larger optotype thresholds were raised. The degree of loss was larger for tritan. For the smaller optotype, protan thresholds were elevated in the majority of patients. Tritan losses were greater and disproportionate to the loss seen with the larger optotype. Every person including those with minimal fundal changes had tritan test results for 1.5 degree optotypes .2 SD above the normal mean. Tritan thresholds varied with the severity of the ARM. Conclusions: The test is sensitive, simple and quick to administer, and easy for patients. Therefore, it should be useful in detecting and monitoring elderly people with age related changes in their fundi before irreversible loss of vision has occurred. I t is common for ophthalmologists to see patients with age related maculopathy (ARM) only after considerable uniocular irreversible visual loss has occurred.1-5 A screening programme involving simpler tests that could be carried out by non-specialists 6 10 is needed to identify ''at risk'' patients who have no symptoms. Even if methods of treatment are not very efficacious, the condition is so common that screening would result in very considerable sight saving. 11 12Various methods have been proposed. The results from electro-oculograms (EOGs), non-photic EOGs, electroretinograms (ERGs), pattern electroretinograms (PERGs), and multifocal ERGs are controversial. [13][14][15][16][17][18][19][20][21][22][23] Psychophysically determined losses of rod sensitivity have been reported to occur before other symptoms. [24][25][26] [41][42][43][44] small losses occur in otherwise symptomless patients after a period as short as a year.41 This paper is the first report on the possibility of screening using (in a small series) a modified method of colour contrast sensitivity testing. Apart from technical modifications to software and hardware, we investigated the effect of using a flashed smaller optotype confined to the central macula. The sensitivity for detecting ARM was thereby improved and the results suggest how screening for ARM might be carried out in larger surveys. METHODS EquipmentColour contrast sensitivity was measured with a revised version of the equipment used in previous work. [32][33][34] In this test, isoluminant coloured optotypes are generated on a calibrated monitor, on a white background of ,20 cd.m 2 and ...

(1) clinical techniques used to isolate S-cone ERGs are appropriate; (2) there are at least two types of tritanope and in those we investigated, functional S-cones are probably displaced into the retinal periphery.

EtOH- and light-EOGs are affected differentially. In ARM, even with minor fundus changes, patients appear to have a general abnormality in the RPE. The alcohol response abnormality is correlated to the fundus appearance, but not with age. These results provide further evidence that EtOH acts by a pathway different from that governing the action of light. These results support histologic and other evidence that in ARM there is a functional barrier between the choroid and the RPE-retina.