Along with glaucoma, diabetic retinopathy and cataracts, age-related macular degeneration (AMD) is one of the world’s most common causes of blindness. According to the American Academy of Ophthalmology (AAO), five factors strongly influence the likelihood that a person will develop AMD: obesity, hypertension, a personal history of smoking, family history of the disease, and, most importantly, being over 60 years old. Statistics from the BrightFocus Foundation show that approximately 11 million Americans live with some degree of AMD. In the United States, there are more people affected by AMD than by glaucoma and cataracts combined.
AMD refers to a condition in which the eye’s macula deteriorates, destroying central vision and acuity over time. The macula is located in the center of the retina, a thin tissue layer lining the inside of the back of the eyeball. The retina receives light captured by the lens and translates it into neural signals, which the optic nerve sends to the brain to enable visual perception. The macula is crucial for central vision and for discerning colors and fine details.
AMD occurs in two forms: dry and wet. The difference between the conditions isn’t in their effects, but in their causes. Up to 90 percent of people with AMD have dry macular degeneration, which is characterized by the formation of drusen (small white or yellow deposits of lipids) on the area of the retina directly beneath the macula. The drusen cause the deterioration of the macula over time, leading to AMD.
Wet AMD is much rarer. It represents just 10-to-15 percent of AMD cases, but accounts for about 90 percent of cases of severe vision loss from AMD. Wet AMD tends to occur with suddenness and may cause a person’s vision to quickly and severely decline. This form of the disease is caused by the growth of abnormal blood vessels near the macula. These blood vessels often leak, bleed and break inside the eye, all of which harms the macula.
When untreated, patients with AMD experience gradual, irreversible vision loss that can eventually lead to total blindness. Fortunately, scientists are looking at new ways to treat AMD to prevent blindness and possibly even restore vision lost to the disease.
New developments in AMD treatment
There have been several interesting developments in the field of AMD treatment in the last year. In early 2019, a research team from the University of Liverpool published a study that provided an in-depth understanding of the genetic factors associated with the development of AMD.
Published in the journal Clinical Epigenetics, the study revealed a previously unknown connection between AMD and a set of genes. For the medical research community, the identification of these genes may be key to the development of new forms of treatment — a step that is significantly needed, especially in the case of dry AMD. While there are treatment options to halt the less-common wet AMD, the much more prevalent dry AMD still lacks effective treatment options.
In addition to the identification of these genes, in 2018, researchers in the UK conducted promising work in the use of stem cell therapy to restore vision lost to wet AMD. Nature Biotechnology published the results of a Phase 1 clinical study led by the London Project to Cure Blindness. During the study, which included two patients with advanced AMD, surgeons implanted a unique “patch” over each patient’s damaged macula. The patch was made of embryonic stem cells specially designed to differentiate into the eye’s retinal pigment epithelium (RPE) cells.
The two patients had lost their central vision to the point that they could barely see a book in front of them, let alone read. Without treatment, both patients would have been blind within weeks. Over the course of the year-long study, however, the patients’ vision improved. They experienced a visual acuity gain of 29 and 21 letters, respectively. Pete Coffey, DPhil, professor at University College London and one of the authors of the study, told the Guardian newspaper he believes the treatment could be available to the UK’s NHS surgeons within five years.
Other researchers are focused on eye drops as an alternative treatment for AMD. Currently, AMD patients are treated almost exclusively through monthly injections of drugs directly into the eye, which can only be administered by a licensed medical professional. Researchers from the University of Birmingham are working to develop cell-penetrating, peptide-based eye drops. These eye drops would provide patients with an effective AMD treatment method that is far less invasive, stressful, and time-consuming.