eye

Eyes: Windows to the soul…. And your body!

Eye exams can determine much more than your visual acuity and prescription for glasses. Many systemic conditions can manifest in the eyes before other obvious signs and symptoms develop. Regular eye exams (every 2 years unless otherwise specified by your practitioner) are important for every age group.

During an eye exam, the back of the eye is examined in detail. By looking through the pupil to the back surface inside the eye at the retina, we can view retinal arteries and veins, the macula, which is responsible for a central vision, and also the optic nerve, which is a direct connection from the eye through to the brain. In fact, the eye is the only part of the body where we can have a direct view of living vasculature and brain tissue uninterrupted & noninvasively. In other words, the eye can literally act as a window to the rest of the body.

Abnormalities in retinal vasculature for example can often reveal associated systemic vascular conditions such as diabetes, systemic hypertension or carotid disease/stroke. Another example is optic nerve swelling or inflammation, which can suggest conditions as serious as intracranial hypertension or MS. As a follow up from one of our recent articles, today we will be focusing on one of the most common systemic conditions that can manifest in the eye, diabetes.

As mentioned in our previous article by Dr S.H, diabetes is one of the leading causes of blindness & vision impairment in developed countries. It is therefore particularly important for diabetic patients to have regular eye exams. Studies show that up to 50% of Australians with diabetes do not have regular eye tests.

Most Medical practitioners now work closely with Optometrists & Ophthalmologists part of diabetes care plans for diabetic patients. The National Health & Medical Research Council (NHMRC) recommends annual eye exams for patients with higher risk of developing diabetic retinopathy and at least every second year for those less at risk. Risk is often determined by the duration of diabetes, how well blood sugar levels are controlled and whether there are already signs of pre-existing diabetic retinopathy. Diabetic retinopathy is a sight threatening complication that can cause irreversible blindness if undetected & not treated in time.

So what is diabetic retinopathy? It is defined as the microvascular anomalies that develop in the retina secondary to blood sugar fluctuations. This leads to leakage of blood and fluid from the retinal blood vessels at the back of the eye. The more advanced form of the disease is proliferative diabetic retinopathy, where new blood vessels begin to grow in the retina. The problem with these new blood vessels is that unlike normal retinal vasculature, they are leaky! The chance of irreversible vision loss is therefore very high. The unfortunate fact is however, at the early stages of diabetic retinopathy, there are no obvious symptoms until the changes are severe (and often too late to treat).

Another less known ocular manifestation of diabetes is fluctuation in vision and spectacle refraction. Blood sugar fluctuations due to diabetes can cause temporary swelling of the lens that controls focusing inside the eye. Diabetic patients are also known to be 2-5 times more likely to develop cataracts and at a much earlier age group than the rest of the ageing population (Klein et al).

The Visual Impairment Project conducted in Victoria in 2000 showed that on average almost a third (29.1%) of Australians with diabetes have diabetic retinopathy. Furthermore, as reported by Cheung et al, more than 60% of type 2 & almost all type 1 diabetics of at least 20 years duration will have some sort of diabetic retinopathy. In other words, everyone with diabetes is at risk of developing diabetic retinopathy. The good news is that 98% of vision impairment due to diabetes can be prevented with early detection and treatment (Ting et al). This can be achieved by firstly working with your medical practitioners to adequately control blood sugar levels & also by having regular eye exams so that ocular complications are detected early.

References:
Photo: K. Viswanath. J. Comm. Eye Health 2003;16(46) 22

Klein BE, Klein R, Moss SE. Incidence of cataract surgery in the Wisconsin Epidemiologic Study of Diabetic Retinopathy. Am J Ophthalmol. 1995;119:295–300. [PubMed]

Resnikoff S et al. Global data on visual impairment in the year 2002. Bulletin of the World Health Organization, 2004, 82:844.

Ting D et al, Diabetic Retinopathy. Screening and Management by Australian GPs, Aust Fam Physic, 2011;Vol 40(4):233-8

McKay, R., C.A. McCarty, and H.R. Taylor, Diabetic retinopathy in Victoria, Australia: the Visual Impairment Project. Br J Ophthalmol, 2000. 84(8): p. 865-70.

Cheung N, Mitchell P, and Wong TY, Diabetic retinopathy. Lancet., 2010. 376: p. 124-136.

By: Dr YB