Diabetic retinopathy

Background theory

Retinopathy is a problem with the retina, the layer of the eye which contains the cells that detect light energy. It is a complication that arises from diabetes – which is even more concerning with the increasing incidence of diabetes linked to the obesity epidemic.

Some data cited by diabetes.co.uk indicates that:

"Obesity is believed to account for 80-85% of the risk of developing type 2 diabetes, while recent research suggests that obese people (having a body mass index - BMI - of 30 or greater) are up to 80 times more likely to develop type 2 diabetes than those with a BMI of less than 22"

(see diabetes.co.uk/diabetes-and-obesity.html)

The Fred Hollows Foundation (www.hollows.org/au/eye-health/diabetic-retinopathy) notes about diabetic retinopathy that:

It commonly occurs in both eyes,
Most often starts with no visual symptoms,
Then, in the early stages, called the non-proliferative stages, blood vessels in the retina start to leak fluid and blood into the eye as their walls weaken and bulge (but do not yet burst),
The retinal blood vessels may also become distorted and blocked in some parts of the retina, resulting in less delivery of nutrients and oxygen to the cells in those retinal areas,
This leakage may result in blurred vision though generally this non-proliferative stage is not too problematic.

However, the next stage, the proliferative stage when new blood vessels grow within the retina, can result in visual problems. These new vessels tend to be fragile and can rupture easily and bleed and the haemorrhages can lead to the formation of scar tissue, which can cause a catastrophic drop in vision.

As noted by Lil Deverell, an orientation and mobility specialist in Melbourne:

"Functional vision with DR basically depends on where in the field the haemorrhages happen. Patchy peripheral loss can be readily compensated for by head and eye scanning during O&M, so people can function for a while as if the scotomas aren't there (and might not realise they have field loss). If the bleeds happen in the macula then the functional result is not patches of scotoma as in your simulation, but partial or abrupt loss of acuity with implications for literacy and object recognition (blur or loss). Eccentric viewing might make a difference for a time if there is a defined patch of clearer field close to the fundus. However, this eccentric viewing facility will deteriorate as more/central bleeds happen over time."

We've tried to simulate the functional consequences of DR as best we can within this complexity of visual outcomes noted by Lil Deverell, preserving some functional vision initially to model the patchy peripheral loss and the fact that head and eye scanning (which we can't simulate here but can in a virtual reality model) can compensate.

Background theory

Retinopathy simulation