Wet AMD Treatments

An eye with late stage exudative AMD

Treatments for Exudative (Wet) Age Related Macular Degeneration (AMD) have advanced significantly in the last 10 to 15 years- before then, there were types of wet AMD which could not be treated. If the new blood vessels were underneath the fovea, the most specialised part of the retina at the centre of the macula – responsible for the sharpest of vision, treatment with lasers would damage the new blood vessels, but damage the fovea also, damaging central (straight ahead) vision. Lasers can still be used in some cases of Wet AMD, depending on the position of the new vessels.

The first major advance was PhotoDynamic Therapy PDT, which used a much lower powered laser to damage the vessels without damaging the overlying retina. This was made possible by using photo-sensitising pigments- injections of a drug called verteporfin (Visudyne) allowed the vessels to be targeted- they absorbed the laser energy which clotted the blood in the vessels, but the retina (which in that area doesn’t have blood vessels within it) remained undamaged. PDT was not suitable for every case of Wet AMD, and sometimes would require more than one session of treatment, but it was a possibility for previously untreatable eyes.

Intravitreal injections- injections directly into the vitreous jelly at the back of the eye, with a drug called ranibizumab (Lucentis). Lucentis is an AntiVegF- which works by blocking  Vascular Endothelial Growth Factor- a hormone released which causes new blood vessels to grow. While the ability to grow new blood vessels is useful in many situations- a bad skin burn for example, in the eye new vessels are a problem- in Wet AMD they are the problem. AntiVegF treatments work by inhibiting new vessel growth, and also makes them less leaky. This can lead to a stabilisation of vision and in some cases a slight improvement. Lucentis may also sometimes be useful to treat macular oedema (swelling) in Diabetic Macular Oedema, and oedema secondary to retinal vein occlusions. Treatment with AntiVegF seems to be effective and safe, but the treatment needs to be ongoing, and there is a possibility that over time the drug may lose its effect.

Recently another drug has been licenced for injections into the eye. Eylea (Afibercept) is another AntiVegF and is used in a similar way to Lucentis, and it may be slightly less expensive. It is recommended for treatment in a similar way, but the interval between injections could be longer with Eylea- depending on the individual’s results. This may be more due to licencing issues than it being a better drug- doctors have to use the drug in the manner that it is recommended, and the recommendations of the two drugs are slightly different.

Radiation treatment is looking to be another effective possible treatment for Wet AMD. There are two distinct treatment methods, which differ in the way they deliver the radiation to the tissue.

Brachytherapy (which literally mean close treatment) is sometime used to treat tumours by exposing them directly to a source of radiation- in some tumours they sometimes implant a radioactive “seed” which can deliver the radiation over a longer duration. In the eye, the radiation source is introduced and held very close above the neovascular membrane, which gives it a high dose of radiation over a short time. There may be difficulty in holding the source at the correct distance above the retina for the duration of the treatment, and the required vitrectomy (removal of some or all of the jelly within the eye) usually causes a secondary cataract. This cloudy lens could be removed at a later date if necessary. There are also possible risks to the surgeon performing the radiation therapy- most brachytherapy treatments now performed may require a surgeon to place the probes in the correct position, but once the equipment is in place, they can use a remote delivery system to avoid exposing themselves to the radiation- this seems not to be easy to achieve in the eye at this time.

The Iray machine, a low voltage xray machine which delivers xrays to the macular area through three beams which are shone into the eye through the lower sclera (white of the eye). An electronic control system ensures that the three beams cross (or focus) in the correct position to irradiate the new vessels and ensuring minimal exposure to the surrounding tissues.

One of the first studies from Mexico reported that over 12 months, patients treated by this method required less anti vegF injections than the control group. This could mean that treating AMD may be cheaper in the future, and hopefully therefore treatment may become more widely available.

The advantage of the Iray machine is that it is self controlling- it will cut the radiation if there is a loss of fixation, it does not require invasive surgery, and there is a reduced risk to the clinician performing the treatment. There is also a reduced risk of cataract development which is a common risk in the type of surgery required for the brachytherapy. If the Iray proves to be as effective as they think it will be, it may become the treatment of choice for radiotherapy.

All of these relatively new treatments give hope to people with Wet AMD, but paramount is early detection – routine eye exams are important but  if you notice any distortion in either eye, it should be investigated urgently.

 

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