The macula is the central region in the retina. This area is responsible for sharp vision, which is necessary for being able to recognise objects and for reading. The side of the retina is only needed for seeing movement and rough outlines.
The damage occurs as a result of the process of ageing. This ageing process can sometimes speed up suddenly due to the ingrowth of new blood vessels from the underlying choroid.
A distinction is made between dry and wet macular degeneration:
1. Dry Age-related Macular Degeneration (AMD)
Dry or atrophic macular degeneration is the most common form, accounting for 85-90% of all cases. This disorder of the retina is characterised by the formation of small yellow deposits called drusen beneath the retina in the macular region. This results in ‘thinning and dehydration’ of the macula.
Dry macular degeneration evolves more slowly than the wet type.
The extent of the central loss of vision depends on the localisation and extent of this atrophy of the retina. The patient experiences blurred vision, blind spots, and straight lines can appear wavy. Side vision or peripheral vision is rarely affected.
Dry macular degeneration is currently untreatable. Low Vision aids and support can help patients live with the loss of sight resulting from LMD.
Some cases of dry degeneration evolve in time into the wet type.
2) Wet Age-related Macular Degeneration (AMD)
Wet macular degeneration occurs in about 10-15% of cases. This disorder of the retina is characterised by the presence of choroidal neovascularisation (CNV). This means that new blood vessels form in the macula. These blood vessels can bleed or leakage and swelling can occur.
Wet macular degeneration can bring about a serious and rapid decline in eyesight. The patient experiences blurred vision, blind spots, and straight lines can appear wavy. This is caused by blood or fluid under the retina.
Side vision or peripheral vision is rarely affected. The retina at the side remains good, so the patient will NEVER go completely blind.
Age-related wear and tear is the main reason for the damage to the macula. In people older than 55 it causes a serious loss of vision. The ingrowth of new blood vessels from the underlying choroid can sometimes cause the deterioration to accelerate suddenly. The retina at the side remains good so that the patient will NEVER go completely blind.
The first symptoms of AMD are usually impaired ability to read and distortion of straight lines. Dark spots can also appear in the central field of vision or colours can appear bleached.
These symptoms are best checked on an Amsler grid: a grid with horizontal and vertical straight lines and a central fixation point. If the patient sees black spots or bent lines on this grid, the ophthalmologist will recommend a retinal examination as soon as possible.
A fluo-angiography is carried out to trace the new blood vessel growth. This is done by injecting a special dye (fluorescein)into a vein in the arm, after which photos of the retina are taken. Using indocyanine green, images are made of the choroid (located just under the retina).
A cross-section of the retina can also be made using OCT (Optical Coherence Tomography). Light rays are used in this completely painless procedure.
Intravitreal injections for anti-VEGF
The formation of the new blood vessels on the retina can be temporarily treated with a new drug that has only been used in eyes since 2005: anti-VEGF (anti-vascular endothelial growth factor).
The drug stops the growth of the blood vessels and stabilises and/or improves sight.
Anti-VEGF (ranibizumab (Lucentis®) or pegabtanib (Macugen®)) is currently administered via an intravitreal injection (i.e. an injection into the eye).
For the first three months, an injection is given monthly. Then photos are taken of the eye again. If the blood vessels have completely gone, a monthly check-up is arranged. A new injection is needed if blood vessel regrowth occurs.b The intravitreal injection is carried out with local anaesthetic eye drops. The pupil is dilated with a drop of Tropicol and Phenylephrine, fifteen minutes before the procedure.
The eye is then thoroughly disinfected to reduce to a minimum the risk of infection. An eyelid retractor is applied to the eye, so that the patient cannot blink. With a very fine needle, 0.05 ml Lucentis® or Macugen® is injected into the eye. This lasts about 30 seconds. The injection is usually painless. The patient may sometimes feel a slight pressure on the eye. The doctor will massage the eye a little to relieve the pressure in the eye.
After the procedure, the eye pressure and retina are checked. In very rare cases the retina can become detached during the procedure.
For a week after the procedure, the patient must use antibiotic G. Tobradex eye drops 4x/day in the eye, to prevent infection and inflammation. The first check-up is planned for 1 week after the operation. This is usually for the purposes of checking eye pressure and to see whether any infection has occurred.
The effect of anti-VEGF is usually only evident after about one month. In some cases it may even take three months before any noticeable effect occurs. (it takes a while before all the bleeds, blood vessels and leaks have dried up). In a recent study with a three month follow-up, improvement was observed in 40% of the patients treated. There was a deterioration in 5% of the patients. Vision remained stable in 55% of the patients. If no treatment is given, the natural evolution is a deterioration in sight in practically all cases.
Possible risks for the eye are: infection, bleeding, retinal detachment, and increase in eye pressure,... Possible risks for the body are usually of a thromboembolic nature (thrombosis, stroke,... ). However, studies show that the risk of these general side effects is very small in the case of injections into the eye.
Lucentis® has been reimbursed since 1 November 2007. The reimbursement (in category B) is valid under certain conditions if this is used in patients with subfoveal choroidal neovascularization secondary to (wet) age-related macular degeneration.
Photodynamic therapy (PDT) is a technique used in the case of classical abnormal blood vessels which are situated under the fovea. Visudyne® (verteporfin) is injected via an infusion. The drug circulates in the blood stream and binds with molecules called lipoproteins. These lipoproteins gather in cells which then quickly divide; this includes the new choroidal blood vessels. The drug is then activated in the abnormal blood vessels with a precisely calculated dose of light at a specific wavelength. The activated drug converts normal oxygen in the tissue into high-energy oxygen. This high-energy oxygen disrupts the normal action of the cell, causing the cells to die. This action only occurs if the drug can be combined with light. As the light is beamed directly at the abnormal tissue in which the drug is stored, the damage to the surrounding tissue is kept to a minimum.
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