For low vision specialists and those who consult them
Implanted miniature telescopes: science fiction here today?
December 3, 2009Posted by on
A telescope for people with macular disease which can be implanted in the eye, which isn’t visible to others and leaves you with both hands free, sounds great to most people. It even sounds a bit like science fiction – a world away from most low vision devices which are hand-held magnifiers which have been used for centuries. Surely everyone with macular disease should have the implantable miniature telescope (IMT) implanted as routine?
I am a little more reserved. Whilst it’s true that visual acuity improves when the telescope is implanted, by three lines on average, this comes at the expense of a restricted visual field and reduced light getting through to the retina. We know that people with macular disease find cataract surgery useful even when there’s not a visual acuity increase (reference) – presumably because they appreciate the extra light which reaches the retina in this case. It seems odd to implant a device which significantly reduces the amount of light getting through the eye’s optics, even if that does give a small improvement in visual acuity.
It is important to note that in all of the studies to date, the improvements reported have been measured after a very intensive rehabilitation programme which includes eccentric viewing training and careful instruction in the use of these telescopes. To date no studies have been published which show the improvement in visual acuity without the implanted telescope, but with such close contact with a rehab worker. As the device is only in early stages of clinical trials, it isn’t appropriate to yet have a randomised controlled trial (RCT) of the IMT, but I eagerly await the results of a well conducted RCT on this subject.
Finally, it is not completely risk free as a procedure: two of the subjects in the safety trial (1%) required a corneal transplant following the implant. There also the risks of retinal detachment and infection from any surgical procedure on the eye.
I have no doubt that some people who have the IMT or other intraocular telescopes implanted find them useful and have a good outcome. I also concede that I am fairly conservative when it comes to new treatments and tend to remain sceptical for longer than some of my colleagues do.
Now for the disclaimer: I have no commercial interest in the IMT or its competitors. The IMT may well be the best option for you: this blog post is purely my own (naturally sceptical) opinion. If you are considering this procedure your ophthalmologist and optometrist are by far the best people to seek advice from.