Technology combined with rehabilitation can improve quality of life for patients
Mr Felipe Dhawahir-Scala
Consultant Ophthalmologist and Vitreoretinal Surgeon Director of the Acute Ophthalmic Services Manchester Royal Eye Hospital.
The CentraSightTM Treatment Programme aims to restore some useful central vision in patients with bilateral end stage age-related macular degeneration who have significant bilateral visual impairment (visual acuity between 6/24 and 6/240 in each eye) by implanting the Implantable Miniature TelescopeTM (IMT) in one eye.
This miniature telescope provides 2.7x magnification and a field of view of 20°. It works on the principal of a Galilean telescope and contains no electronics. It is implanted into the better-seeing eye after removal of the lens, taking up the position of the lens. The implant enlarges the image and projects it onto healthier areas of the retina outside of the macula (see figure below). Patients must undergo around 6 rehabilitation sessions post operatively to learn to adapt to the new visual status this creates: using the implanted eye for detailed tasks such as watching TV, recognising faces or reading and the non- implanted eye for navigation and depth perception. Participation in the rehabilitation process is vital to achieve full benefit from the programme. In suitable patients, the CentraSight programme has been shown to improve visual acuity and quality of life (Hudson, Lane et al. 2006, Hudson, Stulting et al. 2008).
Diagrammatic representation of effect of IMT
Patients are screened to assess their suitability for the programme. An external telescope simulator is used to simulate the magnification and field of view produced by the implant and the experience of having a magnified view in 1 eye and a non-magnified view in the other. This establishes whether a patient will experience an improvement in visual acuity with implantation and demonstrates the tradeoff between a 30° reduction in the field of view on the side of implant (i.e. if implant in the right eye, the reduction is on the right side) whilst improving the visual acuity in the implant eye. Not only must patients appreciate a subjective improvement with the simulator, they must also accept this tradeoff; therefore the CentraSight Programme may not be a solution for all patients with AMD.
The safety and effectiveness of the CentraSight Programme has been studied in a prospective, multicentre clinical trial (Hudson, Lane et al. 2006, Hudson, Stulting et al. 2008). 206 patients who have not had previous cataract surgery were implanted and followed up for 2 years. Data from a 5 year extension study has now also been published (Boyer, Freud et al. 2015).
A mean gain of 3 lines of ETDRS visual acuity was present both 1 and 2 years after implantation. At 5 years mean improvement was 2.5 lines.
Improved visual acuity was associated with a clinically significant improvement in quality of life assessed by the National Eye Institute Visual Function Questionnaire. These benefits are expected to translate into significant improvements in mental health; (Hudson, Lane et al. 2006); significantly fewer falls than would be expected in a similar aged population (Hudson, Stulting et al. 2008) and patients being better able to care for themselves and others, and to perform activities of daily living (Stevenson, Hart et al. 2004, Hudson, Stulting et al. 2008).
This year Mr Felipe Dhawahir- Scala implanted the first NHS funded patient at Manchester Royal Eye Hospital. It is hoped that the CentraSight Programme will be more widely available on the NHS in the future.
A further study is planned to examine the safety and effectiveness of the CentraSight programme in patients who previously had cataract surgery. This will take place over 3 sites in the USA, recruiting 50 patients initially, with an extension to 75 if results are favourable. It’s hoped this will open up this technology to patients with end stage dry AMD and previous cataract surgery.