The College of Optometrists

hi there!

i was wondering if anyone would be able to help me....i understand the ocular impact diabetes has on the eye-microvascular leakage,occlusions/flames/dot/blot etc....but i really dont understand why this happens. why is there a loss of pericytes in diabetes??! hence how does the blood sugar level lead to all these complications?! -i should just accept that it happens right..? BUT I CANT!!! help!

Diabetes causes elevated sorbitol levels in the blood. This is because of an energy pathway that is used when sugar levels in the blood are very high (hyperglycaemic). This pathway converts glucose into sorbitol. Chronically high sorbitol levels cause cataracts.

As part of the pathway, an enzyme called aldose reductase is used and this is very concentrated in the retinal capiliaries. This seems to cause the pericytes in the capiliary walls to loose their nuclei. This inturn causes capiliary wall thickening, and parts of the capiliary to non-function. This causes local hypoxia and this hypoxic event causes cappiliary mal-formations called microaneurisms.

Any retinal hypoxia will cause production of vaso-proliferative factors which will cause neovascularisation. The local hypoxia will also cause the other ritinal changes such as exudates and haemorhages.

So diabetic changes due to the rise (among other things) of sorbitol causes retinal capiliary changes and damage. and new vessels to form. hope it helps = steve

much appreciated!...it does help! thanks :)

Hi again,

there is a bit more - as the causes of histological changes are probably multi factorial. Other factors that may cause basement thickening of the capiliaries may well be the changed hydro dynamics of the blood due to hyperglycaemia. Some causes of cell death and tissue damage may be due to other compounds produced in hyperglycaemic conditions. All these compounds and the aldose reductase change the environment for the capilaries causing thickening, pericyte loss and leakages. Pericytes themselves act like the blue print of the capilary and with their loss - there are abberant formations like microaneurisms and also leakages of plasma and blood. From knowing this, researchers have found compounds that inhibit these changes.

all the best - steve I am thinking of doing a vocabulary like the nystagmus one just completed -do you think it would be of use?

any vocabulary is useful vocabulay!id certainly read it :) thank you once again