Eye Conditions Related To Diabetes
Diabetes is the primary cause of blindness in adults ages 20 to 74. It affects the eyes in a number of ways. The changes in blood sugar levels caused by diabetes affects the lens inside the eye, especially when blood sugar levels are poorly controlled.
These changes result in blurring of vision, which changes from day to day depending on the blood sugar levels. Diabetes also causes the lens to become cloudy. This condition is known as cataract and it happens because the high sugar levels found in the fluid around the lens causes the lens to swell with more water than usual.
This results in blurring of vision as the lens becomes opaque. This however, can be treated. The treatment for cataract is surgery. During cataract surgery, the cloudy lens is removed or cleaned out and replaced by a clear manmade lens.
Most cataract surgeries are done with a technique called phacoemulsification, also called “small cut (incision) cataract surgery.” The cut (incision) can be smaller because the harder centre section of the lens is liquefied and then vacuumed out. Under local anesthesia, a surgeon performing phacoemulsification makes a small opening on the side of the cornea. A device that sends out ultrasound vibrations is inserted into the eye and breaks the lens into small pieces. The fragments are then removed by suction through the small cut in the eye.
The most serious eye condition related to diabetes is Diabetic Retinopathy. This occurs when blood vessels of the retina (inner part of the eye) become blocked, leak or grow incorrectly. There are different types of diabetic retinopathy, and it can be worse for some people than for others, depending on the severity of changes to the blood vessels.
The different types of retinopathy are non-proliferative diabetic retinopathy, proliferative diabetic retinopathy and maculopathy. Non- proliferative diabetic retinopathy is less severe and does not usually affect vision. This develops when small blood vessels in the retina become blocked, causing them to swell. These swellings are known as microaneurysms.
Microaneurysms may leak blood forming hemorrhages or leak fluid forming exudates. These changes do not cause sight problems immediately, but the eyes will need to be monitored carefully to ensure that the retinopathy does not worsen.
Retinal blood vessels enable oxygen to reach the retina so that it functions properly. If non-proliferative diabetic retinopathy worsens, many of the retinal blood vessels become damaged or blocked. When these changes affect a large area of the retina, blood supply to the retina is reduced and this is called ischemia. The body tries to fix this by growing new blood vessels on the retinal surface or into the vitreous gel. Unfortunately, these new vessels are weak and they bleed easily, which results in hemorrhages over the retinal surface or into the vitreous gel. These types of hemorrhages can reduce or totally obscure vision.
The blood may be reabsorbed into the body over time and vision may improve. But there is a chance that these haemorrhages will keep happening and the blood may not be completely re-absorbed. This can lead to permanent loss of sight.
Large hemorrhages can lead to scar tissue formation and this can pull on and distort the retina as it shrinks. This type of advanced diabetic eye disease may result in the retina becoming detached, bringing with it a risk of serious sight loss.
Diabetic maculopathy occurs when the retinopathy affects the macula (the most sensitive and important point of the retina). This causes the central vision, which is required for seeing fine detail and colours, to be blurred. This will make things like reading, writing and seeing details difficult.
So, how do we reduce the risk of developing retinopathy or help stop it from getting worse?
- Good control of the blood sugar levels.
- Tight control of the blood pressure and cholesterol levels.
- Keep fit and maintain a healthy weight.
- Give up smoking, as this damages the nerves, kidneys and the heart. Smoking also increases blood pressure and blood sugar levels.
- To get regular eye screening.
The most effective measure to prevent sight loss due to diabetic retinopathy is regular retinal screening. Early detection and treatment will prevent sight loss.
Most of the eye problems caused by diabetes can be treated, but it is vital that these problems are picked up as soon as possible, as any treatment given is most effective when given early. A detailed retinal screening should be performed every year. During this visit, dilating drops (eye drops to widen the pupil) is instilled to allow a good view of the retina.
Screening helps to prevent blindness in the majority of people at risk.
How can diabetic retinopathy be treated?
If the sight is at risk from retinopathy and it has been picked up early enough, laser treatment will be given. Laser can be given in two ways:
Localised laser treatment
This is given when only a small part of the retina is affected by retinopathy. The laser seals the blood vessels and this stops the vessels from bleeding, as well as helps reduce the swelling. The treatment normally takes a few minutes and helps small areas of retinopathy and maculopathy.
Pan-retinal laser treatment
When new blood vessels begin to grow, a bigger area of retina needs to be treated by laser. Treating a larger part of the retina stops it from producing the growth factors that make new blood vessels develop. When the treatment is successful, the new blood vessels become smaller and disappear over a few months.
The laser treatment is performed at an outpatient clinic, hence there is no need for hospital stay. The pupils will be dilated, following which an anesthetic drop will be applied to the eye. A small contact lens is put on the surface of the eye to keep it open. The laser treatment is then performed. Localised laser treatment does not usually cause discomfort because it does not take long and only treats a small area of the retina.
Pan-retinal treatment can be slightly uncomfortable and will take longer time. The number of sessions given will vary from patient to patient depending on the severity of the disease. The effects of pan-retinal laser would include deterioration of peripheral vision, reduction in color perception and night vision.
It is important to remember that laser treatment aims to prevent the vision from worsening and not improve the vision. However, if laser treatment is not carried out, vision will worsen.
Diabetic macular edema
Diabetic macular edema is usually treated with localised laser unless it affects the centre of the macula (called the fovea). If the edema (swelling) involves the fovea, the eye has to be treated with anti- vascular endothelial growth factor (anti-VEGF) injection.
Anti-VEGF drugs stop new blood vessels from growing and help to improve vision by reducing the macular edema. The anti-VEGF drug is injected through the white of the eye into the vitreous gel inside the eye. There may be a need for more than one injection over a number of months to get the best effect.
Surgery is indicated when bleeding occurs into the vitreous gel. Sometimes, this blood is re-absorbed by the body and vision improves on its own over a few months without the need for any surgery. However, if this does not happen, vitrectomy surgery is necessary.
In vitrectomy surgery, the cloudy vitreous gel is removed and is replaced with a clear liquid, which usually helps to improve vision immediately.Vitrectomy is also carried out if scarring on the retina causes a retinal detachment. Surgery to reattach the retina is always needed to help prevent serious sight loss.
Diabetes-related eye conditions should be recognised and treated early to prevent visual loss. Hence, besides good control of the blood sugar levels, regular diabetic eye screening is important. Most sight threatening diabetic problems can be managed if treatment is carried out early enough.