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Retinal Conditions

Assessment of Retinal Conditions

If a retinal abnormality or condition is suspected, a comprehensive work-up by an orthoptist and ophthalmologist will be undertaken. This will include an assessment of the patient’s vision and pupils, followed by the administration of drops to dilate the pupils so the ophthalmologist can examine the retina at the back of the eye. Occasionally scans or photos of the back of the eye may be taken.

Epiretinal Membrane

An epiretinal membrane (often also referred to as Macular Pucker) is a thin sheet of cellular tissue that grows on the surface of the retina over the macula (our area of fine central vision). Often the membrane can contract, causing the retina to wrinkle, bulge or possibly swell (macular oedema). Symptoms of an epiretinal membrane can vary significantly depending on severity and include reduced central vision, distorted vision and double vision.

Normal OCT scan of macula

OCT scan of macula showing an epiretinal membrane pulling on the retina

 

 

 

 

 

 

In some cases there is no clear cause of an epiretinal membrane, but most commonly they are associated with posterior vitreous detachment, a predominantly age-related process in which the vitreous (clear gel-like liquid) in the back of the eye pulls away from the retina, causing irritation and scar tissue formation on the surface of the retina. Formation of epiretinal membranes can also be associated with retinal blood vessel abnormalities caused by diabetes, vein occlusions or inflammation and post laser, cryotherapy or surgical treatment for retinal detachment or tears.

The treatment for epiretinal membranes is dependent on the severity of symptoms and, in mild cases, observation only may be required. In cases causing significant visual loss or distortion, an epiretinal membrane peel is the only treatment option. This involves a vitrectomy (removal of the vitreous gel in the back of the eye) and physical peel of the membrane material to relieve the tension on the retina. Following the peel, a fluid similar to the natural vitreous is used to replace the removed vitreous.

Retinal Vein Occlusion

The retina contains an extensive network of veins that carry blood away from the eye to the heart and lungs for oxygenation and uptake of nutrients. A retinal vein occlusion is a blockage of one of these veins in the retina. This can cause a build up of pressure in the vein and result in bleeding (haemorrhages), inflammation (fluid build-up) and potentially a lack of blood supply (ischaemia) to part of the retina. Risk factors for a retinal vein occlusion include ageing, systemic conditions such as hypertension, diabetes, high cholesterol, inflammatory disorders, obesity and glaucoma.

The most common symptom of a retinal vein occlusion is blurred or distorted vision, particularly if leaking blood and build-up of fluid spreads to the macula (our area for fine central vision). Symptoms are often dependent on the type, severity and location of the retinal vein occlusion. There are 2 types of retinal vein occlusion:

Normal Retina

Branch Retinal Vein Occlusion

Central Retinal Vein Occlusion

 

 

 

 

 

Branch Retinal Vein Occlusion– occurs when there is an occlusion in one of the small veins that branch off the central retinal vein. This results in bleeding and ischaemia and subsequent damage localised to the area of the retina where the occlusion occurred. A branch retinal vein occlusion may result in reduced vision in an area of someone’s peripheral visual field (side vision) corresponding to the location of the occlusion in the retina. If severe and bleeding and swelling spread to the macula, it can cause sudden or gradual central vision loss .¬†

Central Retinal Vein Occlusion– occurs when there is an occlusion of the main retinal vein draining blood from the eye. This often causes significant visual loss as the blood flow throughout the entire retina is compromised. A central retinal vein occlusion often results in sudden, severe vision loss and can be either painless or painful, in the case of a rise in eye pressure.

Other common symptoms may include seeing spots that float across your vision due to leaking of blood into the vitreous (clear gel-like liquid) in the of back of the eye.

Treatment of a retinal vein occlusion is case dependent and the Ophthalmologist will decide whether lifestyle changes, such as diet and exercise, systemic treatment such as anti-hypertensive medication or injections into the eye of anti-VEGF (reduce bleeding) or steroid (reduce inflammation) medications are necessary.

Macular Hole

The macula is the area on the retina responsible for fine central vision. As the name suggests, a macular hole is an abnormal opening in this area of the retina and is most often caused by a posterior vitreous detachment, a predominantly age-related process in which the vitreous (clear gel-like liquid) in the back of the eye pulls away from the retina. In most cases, the vitreous pulls away from the retina without any consequences but occasionally it attaches very tightly to the macula and, as it pulls away, it creates a small tear in the macula that gradually enlarges to form a hole. Other possible causes include trauma to the eye, macular oedema (swelling), retinal detachment and high myopia (near sightedness).

Normal OCT scan of macula

OCT scan of macular hole

 

 

 

 

 

Symptoms of a macular hole in the initial stages include blurred or distorted central vision. This progresses to a blind spot in central vision if the hole becomes more significant, resulting in difficulty seeing fine detail.

An Ophthalmologist may recommend observation of the macular hole, as minor cases can heal themselves with no treatment. However, in most cases, to improve vision a vitrectomy (removal of the vitreous gel in the back of the eye) is required to prevent further tugging on the macula. The vitreous is replaced with a bubble of air and gas and the patient must remain in a face down position for a few days following surgery to allow the bubble to press against the macula, acting as a bandage to hold the macular hole in place and allow it to heal. The gas eventually dissolves naturally and is replaced by natural vitreous fluid.

Posterior Vitreous Detachment (PVD)

The vitreous humour (commonly referred to solely as the vitreous) is a clear jelly-like fluid that fills the back of the eye between the lens and the retina. It comprises 99% water and the remaining is a mixture of sugars, salts, proteins and collagen. The main roles of the vitreous humour are to help the eye retain it’s spherical shape and applying a certain amount of pressure on the retina at the back of the eye to help hold it in place. The vitreous itself is not attached to the retina but there are many small fibres that extend between the vitreous and retina.

Naturally, as we age, minor changes start to occur in the vitreous. It begins to shrink and liquefy and some of the collagen fibres and proteins become slightly clumpy or stringy and opaque in colour. These can often be seen floating around in an individual’s vision and are particularly noticeable in well-lit areas and environments with white backgrounds, such as office walls. Due to this appearance, these are literally called “floaters”.

The shrinking of the vitreous also commonly results in the tugging of the fibres that adhere to the retina. A posterior vitreous detachment occurs when a section of these fibres pull away from the retina entirely. The likelihood of a PVD increases with age and, in most cases, will cause no vision problems, apart from an increase in floaters or initially seeing flashing lights or sparkles in an individual’s vision as the vitreous pulls away from the retina. Other conditions that increase the likelihood and severity of a PVD include myopia (short-sightedness), uveitis (inflammation inside the eye) and trauma to the eye.

In the majority of cases of PVD, no treatment is required and vision is unaffected. There is a small chance that a retinal tear or detachment can occur as a result of a posterior vitreous detachment if the retinal fibres are strongly attached to the vitreous as it pulls away from the retina. It is therefore wise to see an Ophthalmologist promptly if symptoms of increased floaters or flashing lights are experienced.

 

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Posted on

July 18, 2018