What is AMD?
Age-related macular degeneration (AMD) is a condition that occurs commonly in people over 60 years of age and is one of the most common causes of poor vision in elderly Europeans.
Lining the inside of the eyes is the retina this is a photosensitive layer comparable to a photographic film. A tiny 5mm diameter part of the retina, called the macula, is responsible for sharp visual acuity and colour vision.
Several degenerative processes may affect the macula. In the case of age-related macular degeneration, increasing age is the main causative factor.
The degeneration involves the weakening of certain supportive layers in the macula and the accumulation of metabolic waste products. These yellowish-white deposits resemble calcification and are often referred to as such.
The most common complication is the development of new, abnormal blood vessels which are fragile and easily leak and bleed (so-called neovascular membranes).
What are the symptoms?
The early symptoms of macular degeneration are deterioration of visual acuity and distortion of images. AT WORST complete loss of central vision may occur, with the patient seeing a dark spot central to the visual field.
Darkness and light and forms may still be well-differentiated and a measure of colour vision may be retained. Both eyes are usually affected, one eye typically more advanced than the other. Unfortunately, reading, sewing and other tasks requiring sharp visual acuity become impossible.
On the other hand, macular degeneration per se never causes total blindness and patients often function well and independently within familiar surroundings. Unfortunately driving a motor vehicle is mostly not possible.
What treatment is available?
Therapeutic options available to treat this condition are very limited. Neither spectacles nor surgery or medication can stop the degeneration.
Neovascular membranes may under certain circumstances be treated with laser. Surgical removal of these membranes is being done in selected cases with limited success.
Generally, vision is monitored with an Amsler chart and sudden significant changes in visual acuity and/or distortion on the Amsler chart call for evaluation and possible treatment by an eye specialist. Spectacles and so-called low vision aids (including various magnifiers) are also of some value.
Lastly, it is important to note that age is virtually the only causative factor and no amount of reading, sewing or other activities add to this.
Once this condition has been diagnosed, it is equally important to note that there is no limitation to the use of your eyes and you should confidently engage in any activity your eye allows.
Diabetes and the Eye : Diabetic Retinopathy
Diabetes mellitus (Type 2 Diabetes) affects the eye through premature cataract formation, fluctuating refraction (spectacle requirements) and so-called retinopathy.
Retinopathy implies malfunction of the nerve and sensory layer of the eye due to damaged small blood vessels and manifests in three basic forms:
- Early background changes seldom affect vision and are relatively innocuous.
- Maculopathy impairs vision.
- Proliferative retinopathy, the complications of which may have catastrophic visual consequences.
Optimal control of diabetes through diet, oral medication or insulin injection is very important and may delay, but not necessarily prevent the onset of retinopathy.
Systemic hypertension (high blood pressure) should be well controlled, as should high blood cholesterol levels.
A complete ophthalmic evaluation shortly after the initial diagnosis of diabetes is advised. Depending on the findings at this stage, regular follow-up visits will be scheduled to monitor progression. Since treatment may be required in the presence of absolutely normal vision, these follow up examinations are most important.
Once vision-threatening retinopathy is noted, different forms of laser treatment are employed to improve vision or prevent further complications.
Some of these complications (e.g. vitreous haemorrhage, membrane formation or retinal detachment) may require surgical treatment.
The keys to preservation of vision are:
- Early baseline evaluation.
- Regular follow-up examination (as scheduled or promptly when new symptoms appear) to monitor any progression.
- Optimal control of diabetes.
What are macular holes?
A macular hole is a small break in the macula, located in the centre of the eye’s light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail.
A macular hole can cause blurred and distorted central vision.
What causes macular holes?
As we age, the vitreous ‘gel’ inside the eye naturally shrinks and pulls away from the retina. Occasionally, the vitreous gel can pull on the retina and create a macular hole. In some cases, the fluid that fills the gap left by the vitreous gel may seep through the hole onto the macula, causing blurring and distortion.
Who is at Risk?
Macular holes are related to ageing and usually occur in people over age 60.
What are the treatment options?
An operation called a vitrectomy is used to carefully remove the vitreous ‘gel’ from the affected eye, and replace it with a gas that helps the macula heal.
What is a retina?The retina is the nerve layer covering the inner surface of the posterior segment of the eye. The retina is vitally important for vision, it contains millions of light receptors that capture light rays from our environment. It consists of multiple layers that need to function adequately in order to see.The retina lies on the retinal pigment epithelium (RPE) that anchor it to the choroidal layer. The RPE also remove metabolic waste products from the retina. The deeper layers of the retina are supplied with blood from the choroidal layer through the RPE layer.The posterior segment of the eye is filled with a jelly-like substance called the vitreous. This jelly supports the retina from the inside and is firmly attached to the retinal surface.As we age the vitreous starts to liquefy, resulting in traction on the retina and in some cases retinal detachment.If the retina is detached from the RPE layer, it cannot function as it has reduced blood supply. The retina lifts off the RPE and starts to contract and scar, eventually leading to permanent visual loss.
Types of retinal detachment
Retinal detachments can broadly be classified into Rhegmatogenous, Tractional, Combined and Exudative.
This is the most common and most sight-threatening type of detachment. They can progress rapidly and lead to severe visual loss if not managed urgently. Patients usually complain of seeing flashes of light as well as floaters that look like a swarm of bees (blood cells seen by the patient inside their own eye). The classical visual loss is described as a curtain dropping over the visual field.
These detachments are caused by a fibrovascular membrane on the surface of the retina. As the membrane matures and contracts, the retina starts to lift in that region. Tractional detachments are more stable than Rhegmatogenous detachments. They take longer to progress. The most common cause of Tractional detachments is Diabetes. In a lot of cases, early Tractional detachments can be monitored as they can remain stable over a period of time. Eventually, surgery is indicated.
Combined retinal detachments:
These detachments start off as Tractional and progress to Rhegmatogenous if a small hole is formed by the traction. Surgery is urgently indicated in these cases.
This type of detachment is caused by the subretinal exudation of fluid. Causes can range from infective, inflammatory to malignancy. They are managed medically, as the cause needs to be addressed. They settle once the cause is treated.
The eye is entered using 3 small ports, placed 3,5mm behind the cornea. Through these ports, the vitreous jelly is removed as well as any membranes causing traction to the retina. The retina is attached using a combination of laser and a tamponading agent. The tamponading agent is chosen depending on the type and characteristics of the detachment. Either silicone oil or gas is used. The ports are then removed.
D-ACE is used for young patients with inferior Rhegmatogenous detachments. A small incision is made on the surface of the eye, allowing the subretinal fluid to be drained. At the same time, filtered air is injected into the eye, flattening the retina. Once the retina is flat, a cryotherapy probe is applied to the outer surface of the eye, bonding the retina to the underlying layers. Cryotherapy causes inflammation that acts as a glue to stick the retina down. A silicone explant is then sutured to the outer surface of the eye to oppose the retina to the RPE layer. This explant remains there permanently and is covered with the conjunctiva. It cannot be seen from the outside.