Spare the rods and spoil the retina: revisited

Abstract

Visual function improves with oxygen inhalation in people with diabetes even in the absence of visible retinopathy. Rods consume the most oxygen in the retina due to the high metabolic activity required to maintain the dark current. Therefore, Arden hypothesized that in diabetes where oxygen supply may also be affected due to the changes in retinal vasculature, prevention of dark adaptation may be a viable option to prevent or decrease the rate of progression of diabetic retinopathy. Animal experiments have proven that the absence of rods decreases the development of retinal neovascularisation. The same principle applies to panretinal photocoagulation, an established treatment for proliferative diabetic retinopathy. Recently, a few clinical studies have also shown that preventing dark adaptation by suppressing rods with 500-nm light source at night decreases the rate of progression of early diabetic retinopathy and maculopathy in the short-term. We await the results of a large two-year multi-centre trial (CLEOPATRA trial) to evaluate the long-term effects of decreasing dark adaptation by applying a 500-nm light source as a mask over eyes with non-central diabetic macular oedema.

Do photoreceptor cells cause the development of retinal vascular disease?

“…Several years ago, we reported that photoreceptor cells are the major site of that oxidative stress in the retina in diabetes [59], and experimental or genetic degeneration of those photoreceptors inhibited the diabetes-induced oxidative stress and upregulation of pro-inflammatory proteins. Consistent with the theories of Arden and colleagues [37,41,53], the presence or absence of light affects the retinal oxidative stress, resulting in the retinal oxidative stress caused by diabetes being worse in the dark [59]. Photoreceptors express NADPH oxidase [60] and contain most of the mitochondria found in the retina [61], and both of these can be sources of reactive oxygen species [59,62,63].…”

Reduced metabolic function and structural alterations in inherited retinal dystrophies: investigating the effect of peripapillary vessel oxygen saturation and vascular diameter on the retinal nerve fibre layer thickness

“…Interestingly, patients with RP and choroideremia rarely develop diabetic retinopathy (Arden ). As the rod activity is thought to be responsible for the presentation of diabetic retinopathy, in the absence of rods, the mitochondrial glycolysis would be reduced, and thus the production of oxygen‐free radicals (Sivaprasad & Arden ). It seems that retinal anoxia, which is a major pathogenetic factor in diabetic retinopathy, cannot develop in the presence of degenerative photoreceptors.…”

Contributions of the Melanopsin-Expressing Ganglion Cells, Cones, and Rods to the Pupillary Light Response in Obstructive Sleep Apnea

“…63 In the avascular outer retina, rod photoreceptors are among the most metabolically active cells of the central nervous system and during darkness, the metabolic process requires the highest oxygen consumption of any tissue of the body. 65 The oxygen consumption of rods and cones increases as light levels fall. 65,66 OSA-induced hypoxia leads to inflammatory responses, vascular dysregulation, endothelial dysfunction, and oxidative damage, and it is thought to be one of the most critical pathogenesis factors for ischemic retinal diseases, such as proliferative diabetic retinopathy, retinal vessel occlusion, and oxygen-induced retinopathy.…”

“…65 The oxygen consumption of rods and cones increases as light levels fall. 65,66 OSA-induced hypoxia leads to inflammatory responses, vascular dysregulation, endothelial dysfunction, and oxidative damage, and it is thought to be one of the most critical pathogenesis factors for ischemic retinal diseases, such as proliferative diabetic retinopathy, retinal vessel occlusion, and oxygen-induced retinopathy. 5,6,15 Here, correlations between the PLR and sleep parameters indicated that a reduced peak pupil response to blue flash luminance at À2 and À1 log cd/m 2 (rod condition) was associated with reduced TST and increased levels of the ODI, respectively.…”