Friday February 5 2016
Macular degeneration affects over 600,000 people in the UK
"Statins could be miracle cure for blindness," reports the Express, following a new study into dry age-related macular degeneration (AMD), one of the leading causes of blindness in adults.
AMD is a condition caused by damage to part of the back of the eye called the macula. It’s called "dry" or "wet", depending on whether fragile blood vessels have developed to try to repair the damage. There are treatments for wet AMD, but none for the much more common dry form.
After promising results in the case of a single 63-year-old man, the researchers gave a high-dose of daily statin (80mg atorvastatin) over a year to 23 adults over 50. Ten of the group experienced some vision improvement and a reduction in fatty deposits called drusen in their eyes, but vision in the remaining 13 patients continued to get worse.
The study had several limitations, but this is understandable, given the early stage of this research. Most notably:
- the study was very small
- treatment was non-randomised
- treatment was not concealed (blinding), so people knew what they were taking and why
- there was no control group, so the results weren't compared to people taking no medication or "dummy" medication (placebo)
- vision improvements reported by some participants might have been due to chance
The researchers also point out that dry AMD can vary a lot between people, so it's unlikely that statins would be effective for everyone with the condition.
Overall, there were signs that statins improved vision in dry AMD, but it didn't work for most people. It's not possible to know whether statins could be a "cure" for AMD without more research.
Where did the story come from?
The study was carried out by researchers from Harvard Medical School and the University of Crete, and was funded by Yeatts Family Foundation, the Mass Eye and Ear Neovascular AMD funds, the Loefflers Family Foundation, and the Research to Prevent Blindness Foundation.
The study was published in the peer-reviewed science journal EBioMedicine, and is free to read online.
Generally, the media over-inflated the results and didn't discuss the numerous and important limitations of this research.
Much of the coverage suggested statins may be the miracle cure for blindness in general. However, the study was specifically targeting a particular type of vision loss and potential blindness: dry AMD with large soft drusen deposits.
Other types of dry AMD exist, as well as wet AMD. The researchers themselves said that it is unlikely that statins will be effective across the broad range of dry AMD, as the condition is quite variable.
What kind of research was this?
This was an open-label, small prospective study looking at the effects of high-dose statins on progression of dry AMD.
Small studies like this are useful to test a hypothesis – in this case, that high-dose statins might help dry AMD – but they only represent an early phase in treatment development. These studies may throw up promising results that are subsequently disproven using bigger, better-designed studies.
While it's encouraging when these types of study show benefits, there are no guarantees the benefits will be confirmed when tested more rigorously.
What did the research involve?
The study recruited 26 patients over the age of 50 with a dry AMD diagnosis, with many large soft deposits of drusen causing disruption to cell layers of the back of the eye.
They were all given a high-dose (80mg) of a statin called atorvastatin every day for 12 months, and knew what they were taking and why.
Each had comprehensive eye exams at the start of the trial and every three months after to monitor changes, including the size and number of drusen deposits. Clarity of vision was measured every six months by reading letters at ever-decreasing sizes through corrective lenses, similar to the classic Snellen eye test sometimes done at opticians.
As dry AMD is a progressive disease, they were looking for signs the disease was being slowed, halted or reversed – any of these would be an improvement over current treatment options.
The study also reported the experimental case of a 63-year-old man with dry AMD who took progressively higher doses of atorvastatin than the target 80mg per day in response to deteriorating visual clarity.
What were the basic results?
Of the 26 participants, 23 made it to at least the end of the first 12 months: 10 from Europe, 13 from the US. Three exited the study early: one because of cramps, one because of muscle aches, and one because they felt the drug was inducing hair loss.
Daily high-dose atorvastatin for a year resulted in fewer drusen deposits in 10 of the 23 participants (43%), and near-complete disappearance in eight people.
Ten of those taking atorvastatin improved their visual clarity, by an average of 3.3 letters on a letter chart. This compared to an average loss of 2.3 letters over the same period for those in whom it didn't work. These differences however, were not statistically significant, meaning it may be a chance finding.
The case of the 63-year-old man was much more dramatic. After six months on 80mg daily atorvastatin, his visual clarity improved by 12 letters and the drusen deposits had completely disappeared, leaving him with 20/20 vision.
How did the researchers interpret the results?
The researchers concluded that: "High-dose statins may result in resolution of drusenoid pigment epithelial detachments (PEDs) [drusen deposits] and improvement in visual acuity [clarity of vision]" adding, "Confirmation from larger studies is warranted".
The difference between the dramatic improvement seen in the case study of the 63-year-old man and the comparatively modest, or lack of, effect seen in the 23 taking part in the trial shows the limitations of studying small numbers of people, and the current uncertainly about the effects of this treatment.
There is large variability in small groups, which doesn't tell us whether the treatment will help most people. The way to solve this is to study lots more people. This helps to smooth out the natural variability in people's responses to the same treatment and can highlight groups more or less likely to benefit. These groups can be studied further to figure out why the variation exists and potentially discover other ways to help more people benefit.
Other limitations include that this study was very small, treatment was not randomised, there was no treatment concealment (blinding), there was no control group, and the visual improvements reported between treatment responders and non-responders might have been due to chance.
The study also focused on people with dry AMD with a high number of large soft drusen deposits, which is a sub-group people with dry AMD. These are all limitations, but understandable ones given the very early stage of this research.
As AMD is so variable, the researchers point out that it's unlikely that statins would be effective for everyone with the condition.
The good news is that there were some signs statins improved vision in dry AMD. However, there was a lot of variation and only 43% of those in the trial experienced an improvement in their sight.
Larger studies are needed to look into statins as a possible treatment for AMD. It's not currently advisable to take statins for dry AMD, as there isn't enough evidence.