Feb 10, 2020
Age-Related Vision Loss: Diseases and Emerging Treatments
Dr. Deepa Yoganathan is an assistant professor in the Department of Ophthalmology and Vision Science at the University of Toronto and the co-president of the Toronto Ophthalmological Society. She is one of only 120 retinal specialists in Canada and is an award-winning educator. Dr. Yoganathan recently joined as a volunteer member of Fighting Blindness Canada’s Board of Directors and is committed to helping us develop educational resources about vision loss. At Vision Quest in Toronto on May 29, 2019, Dr. Yoganathan answered the top 10+ most commonly asked questions asked by her patients.
1. What is the macula?
Today’s discussions will focus on the retina, specifically a small area called the macula. When light enters the eye it passes through the cornea and lens, goes through the vitreous and lands on the retina. The retina processes the light and sends signals to the brain to interpret what we “see”.
The macula is the centre 5 mm of the retina and is responsible for determining colour and detail vision. Our visual acuity is based on the integrity of the macula. If you have a disease or there is damage to the macula this cannot be corrected with lenses or glasses. The macula sits between the arcades – the large veins and arteries that come off the optic nerve in the centre of the retina. The fovea is the centre of the macula.
The retina is very thin but is made up of ten layers of different cell types. The choroid is the layer that sits below the surface and it has the most blood vessels per square inch than anywhere else in the body. The blood supply is very important to the retina, and when it malfunctions there is an impact on vision.
Eye specialists use many imaging techniques to gather clues to what’s happening inside the eye. One of the most common tests to see the retina is called optical coherence tomography (OCT). This image shows all layers of the retina and gives us details up to two microns. This picture is a fast and non-invasive way to investigate what is happening inside the eye.
There are two types of age-related macular degeneration (AMD): dry and wet. Dry AMD is more common and less severe. It happens when the macula becomes thinner and is less able to support the photoreceptor cells in the retina. It is characterized by deposits of protein behind the macula called drusen. The wet form is more severe, but there are treatments available. Wet AMD is characterized by abnormal blood vessel growth in the choroid layer of the retina. These abnormal vessels break, bleed and leak, damaging the macula and causing loss of vision.
2. Will I go blind?
This is a difficult question and one of the most common questions asked. There is no easy answer because it depends on the patient’s diagnosis and many other factors including genetics, anatomy, circulation and lifestyle factors. What happened to a friend’s eye or even a patient’s other eye does not indicate what will happen to the patient. Everyone is different, and the disease course and outcome are unpredictable. However, the doctor can use many types of technology to better understand a patient’s specific eye – including OCT, OCT angiography, fluorescein angiography, wide field imaging, autofluorescence, electroretinograms and more. Patients sometimes get frustrated with having so many tests but they allow the doctor to gather as much information as possible about the patient’s specific eye and condition.
We are also fortunate that now there are life changing treatments for wet AMD. The injectable drugs Lucentis and Eylea have revolutionized the way doctors can treat AMD. These treatments became available in 2006 and are about 90% effective at improving or stabilizing vision in AMD patients. Before the year 2000 no treatments were available and everyone who had wet AMD went blind.
However, there is a burden associated with these treatments. These drugs need to be injected into the eye every month. This means that patients and their families must travel, often far distances, to the eye clinic monthly. Fortunately, longer lasting drugs are on the horizon and should be available within the next few years. These slow-release drugs will only have to be injected once every three months.
3. If I do go blind, can I just get an eye transplant or a bionic eye?
Unfortunately, its not that straightforward. Currently, there are three kinds of transplants that can be done on the eye.
- Cornea transplants – this is very common and uses donor tissue to replace the part of the eye that is responsible for focusing incoming light
- A retinal chip (Argus 2 for RP) – this procedure is specific to people who have an eye condition called retinitis pigmentosa (RP)
- Retina translocation – this is a highly experimental procedure for patients who have large macular holes. In this surgery, the doctor removes a piece or retina from outside of the macula and then slides it into the macular hole. This procedure is reserved for only extreme cases.
4. If you do surgery, do you have to take my eyeball out?
5. When you say surgery, do you mean laser?
No. A surgeon will have to cut into the eye, but they are small incisions that will not leave a lot of scarring. Lasers may be incorporated into the surgery but are not the way a doctor will access the eye. It is important to note that other than clinical trials, there are currently no surgical treatments of AMD. A doctor may have to operate on an AMD patient for another reason however, such as a retinal detachment.
Retinal surgery is called a vitrectomy. The surgeon will make three small incisions and insert three ports into the eye. They will insert a light, a cutter and a line to infuse saline into the eye. The doctor will first remove the vitreous – the clear gel that fills the eye – with the cutter. The vitreous will be replaced by a saline solution. In time, the body will replace this fluid with more vitreous.
If the patient has a retinal detachment the surgeon will then remove any scar tissue, suction out the fluid from behind the retina and then laser the hole to reattach the retina. Even though this treatment is not directly for AMD, many patients have reported that their macular degeneration slows down after a vitrectomy. We don’t yet know why this is – it could be because more oxygen is getting into the retina or because there is less traction on the retina because of the removal of the vitreous.
6. Does the treatment injection suck out the blood or fluid?
Treatments for wet AMD involve injections into the eye, but they do not remove anything from inside the eye. When the needle enters the eye, it is carefully kept in the middle of the vitreous where it releases the drug; it does not touch the retina. The injected drug dissolves into the retinal tissue to help close the blood vessels and stop them from leaking blood and fluid.
7. How many injections will I need? Will I need injections for life?
This is another question without a clear answer because every patient is different, and the outcome is unpredictable. Typically, the doctor will start with three months of injections and then evaluate. The number of injections that a patient will ultimately receive are based on how the retina responds to treatment. The doctor will want to give the best treatment with the least amount of risk. Multiple injections, even during the maintenance phase (no vision gain), will give a patient the best long-term vision. When the retina is healthy it helps to maintain vision in the future.
8. What type is better? Dry or wet AMD?
Wet AMD used to be thought of as the “bad kind” because there were no treatment options available and it would cause blindness. However, most people who have wet also have dry – these conditions can occur at the same time. Even with successful injections, wet AMD may be inactive but the dry may progress because there is currently no treatment for dry AMD.
There are different types of dry AMD. Dry AMD is typically characterized by age-related protein deposits in the back of the eye called drusen. These patients can have 20/20 vision and may not even realize there is a problem. The doctor will watch these patients closely to make sure they don’t develop wet AMD. Another type of dry AMD is called geographic atrophy. In this condition there is a large spot on the macula where the tissue has died. This spot can get larger over time, or it can remain stable. The doctor will use many different imaging techniques to determine the type of dry AMD and what part of the macula is affected.
The current treatments for dry AMD are focused on monitoring and prevention. Doctors will encourage their patients to do the Amsler grid test weekly and report any changes in their vision to them immediately. There are also many formulations of vitamins that may be helpful. Another new technology that is currently only available in the US is called the Forsee Home. The patient can do the Amsler test right on the device and it will send any new distortions in your vision directly to the doctor’s office, alerting them that there has been a change.
Future treatments of dry AMD have been the focus of many research studies, but there are no commercially available treatments yet. There are some clinical trials including:
- Brimonidine DDS Phase 3 – an injectable drug being tested by Allergan in Canada
- Cell based therapy using umbilical cord blood cells (Palucorcel)
- Complement factor (APL-2)
- Gene therapy in which cells are injected under the retina, causing a retinal detachment
- Prima implant – a very small chip that connects to a camera for treatment of geographic atrophy
9. Which vitamins should I take?
This is a controversial question because there are many types of vitamins available. Two studies called AREDS 1 & 2 investigated which vitamins were best for AMD. Key findings from these studies included:
- Carotenoids (antioxidants like lutein and xeanthanine) are essential for eye health
- Omega-3 fats are good for dry eyes, but not necessarily AMD
- The best dosage of zinc was inconclusive. Some people had negative reactions from a high dose
10. Should I have genetic testing done?
This is another controversial question. Everyone should be eating a diet rich in fish and leafy green and orange vegetables anyway! However, there are some studies indicating that depending on a person’s genes, some vitamins may have negative effects on health and may even worsen macular degeneration. We need long term prospective studies examining these links.
Age-related macular degeneration is only one form of vision loss that can occur as we age. Diabetic Retinopathy and Glaucoma are other common forms of age-related vision loss.
11. I have diabetes, but I see fine. Why do you have to inject/laser me?
There are two main types of diabetic retinopathy: diabetic macular edema and proliferative diabetic retinopathy. A patient with diabetic macular edema may be able to see fine, but their OCT images can show fluid and blood leaking into the retina. The patient may still be seeing 20/20 because of the area in the eye affected, or because it has been a very slow progression and they may not notice the change. This is why an OCT image is so important; it helps patients to understand why they need treatment even when no vision loss is reported.
In proliferative diabetic retinopathy the circulation of the retina is so poor that abnormal blood vessels start to grow. These new vessels are struggling to rebuild the eye but unfortunately, they steal oxygen from all other parts of the retina. These abnormal vessels are fragile, and they break; the leaking fluid and blood act to block vision. If the macula is not affected by this process the patient might not have impaired vision. However, it is important that these issues are identified and treated before they start to affect the macula.
In general the best ways to manage diabetes in the retina is to control blood sugar, blood pressure, cholesterol and weight, quitting smoking and exercising.
12. What is Glaucoma? Do I have Glaucoma?
Glaucoma is optic nerve damage that is most commonly caused by high pressure within the eye but can also occur with normal pressure. This is different from blood pressure, it is a measure of the pressure inside the eye. Glaucoma cannot typically be diagnosed in one visit to the eye doctor. The patient will need multiple tests to diagnose including visual field exams, OCTs of the nerve and intraocular pressure readings taken at multiple visits.
In summary, the best way to protect your vision is to be an active participant in your health care. Be sure to report any changes in your vision to your eye doctor and visit them regularly. Also, it is important to be wary of any “treatments” that seem too good to be true. There are no approved stem cell therapies for vision loss at this time, but many clinics, in the US especially, have been reported to provide unapproved treatments that can cause people to go blind.
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