Dr Ben Wild
Overview |
The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision.
A sagittal view of a healthy eye (left) and a coronal view of its retina (right).
Age-related macular degeneration (AMD) is an irreversible, progressively degenerative condition characterized by a loss of central vision. It is the most common cause of blindness in the developed world and occurs bilaterally (in both eyes), although usually affects one eye more than the other.
There are two main types of AMD:
1. Dry AMD represents 90% of cases, typically progresses slowly (over years), and is caused by calcification of retinal waste products which then leads to the decay of the retina. It can progress to wet AMD.
2. Wet AMD occurs in 10% of cases, typically progresses quickly (over months), and is caused by the growth of fragile, leaky, blood vessel networks that disrupt the macula.
Dry AMD (left) showing several yellow drusen and one area of geographic atrophy and wet AMD (right) showing drusen and bleeding.
Signs and Symptoms |
Signs
Drusen (calcified waste products in the macula), vascular tissue (fragile blood vessels), scar tissue, bleeding, geographic atrophy (patches of decayed retina).
Symptoms
Decreased vision and contrast sensitivity, central blind spots or dark spots in vision, metamorphopsia (straight lines look warped).
Causes and Risk Factors |
Causes
The decay of photoreceptors (light sensing cells of the retina) in the macula.
Risk Factors
Confirmed: old age, Caucasian background, genetics, smoking, high blood pressure, and high fat diets.
Possible: sun exposure, blue irises, female, cataract surgery.
Prevention and Treatment |
Prevention
Confirmed: foods high in lutein, zeaxanthin, meso-zeaxanthin, and beta-carotene, avoid smoking/2nd hand smoking, avoid vascular conditions such as high blood pressure, diabetes, etc., with a healthy and balanced lifestyle.
Possible: lutein/zeaxanthin supplements, sunglasses, omega 3s, 20mg/day of saffron.
Treatments
Dry AMD
· 15mg of lutein and 2mg of zeaxanthin per day may slow progression of early stages.
· AREDS/AREDS 2 supplements twice a day for moderate to advanced stages.
· Laser photocoagulation for advanced stages.
· Up and coming: Lampalizumab injections, subretinal stem cell injections.
Wet AMD:
· Anti-VEGF injections.
· Photodynamic therapy.
Advanced AMD
· Low vision therapy including quality of life products.
· Optical correction with telescopes and magnifiers.
· Electronic aids such as voice activated products, computers, etc.
Prognosis |
No cures exist for AMD, however, with early diagnosis and treatment, vision can be stabilized for years before possibly declining to a legally blind state. Once diagnosed, self monitoring with an AMSLER grid at home can quickly alert the patient to noticeable progression of their AMD and can allow for more timely follow ups with eye care professionals and treatments.
Amsler Grid |
The above is an AMSLER Grid as described in the Treatments section above. It is recommended to screen each eye once a day and only takes a few seconds. Try hanging this on your fridge (see below for a link to a printable PDF).
How to use the AMSLER grid
1. While wearing the glasses you use to read, hold the grid about 35cm or 6 inches from your face with good lighting.
2. Cover one eye.
3. Look at the central dot with your uncovered eye.
4. While focusing on this dot try to identify if the lines in your central or peripheral vision are blurry, wavy, or missing or if there are stable dark spots.
5. Repeat with the other eye.
6. If you notice any areas on the grid that appear darker, lighter, wavy, blank or blurry, contact your eye doctor right away
Below is an example of possible defects on the AMSLER grid.
Click below for a printable copy of the Amsler grid.