Image courtesy of Maria Richman, O.D.
Excerpted from page 46 of the January/February 2023 edition of AOA Focus.
Age-related macular degeneration (AMD) is the No. 1 cause of visual impairment and legal blindness in people ages 65 and older. As many as 11 million people in the U.S. are affected by some type of macular degeneration, and this number will increase to 22 million by 2050. Nearly 2 million Americans have advanced forms of AMD with associated vision loss. Currently, treatments exist to try to slow the progression of AMD, and there are assistive external low vision devices that help people with reduced vision see better. The progressive deterioration of visual function from AMD has a significant impact on patients’ quality of life and can reduce their independence in performing activities of daily living. Although there is no cure for late-stage AMD, new technology and surgical procedures are exciting options.
A visual prosthetic device, known as an implantable miniature telescope (IMT), is one of the options to improve vision when used in an appropriate patient with late-stage AMD. The first-generation IMT device, invented by Dr. Isaac Lipshitz of Israel, was approved in 2010 and was implanted in more than 700 AMD patients. In previous clinical studies, 90% of IMT-implanted eyes achieved at least a 2-line gain in visual acuity at 12 months and sustained at 24 months. However, concerns about the size of the original IMT implant prompted the development of the Smaller-Incision New-Generation Implantable Miniature Telescope (SING IMT). This device was certified for use in Europe in 2020, and a clinical trial in the United States is currently underway to evaluate improvements in visual acuity and the safety of the SING IMT.
The 2.7X SING IMT’s wide-angle micro-optics magnifies objects in the environment, thereby minimizing the impact of the scotoma associated with AMD. The high-resolution image is projected onto healthy photoreceptors surrounding the macula, essentially restoring usable central vision. This Galilean telescope implant is designed to improve visual acuity and quality of life.
The concept for the functional use of the 2.7X SING IMT allows for detailed central vision while the fellow eye provides peripheral vision. Then, realistic goals could be to watch TV, recognize people and be less dependent on others. Administering the NEIVFQ-25 questionnaire identifies these areas. Unrealistic goals are immediate clear vision, driving or never needing to use low vision devices.
Eligibility criteria for the ongoing U.S. study include study participants to be age 65 or older, a visual acuity of 20/160 - 20/800 in each eye, stable bilateral central scotomas associated with late-stage AMD with foveal involving geographic atrophy or disciform scar, no active choroidal neovascularization within the last six months, adequate peripheral vision in the eye not receiving the implant, no previous cataract/refractive surgery in the study eye, no other retinal conditions (such as diabetic retinopathy, Stargardt, retinitis pigmentosa, etc.), self-motivated, cognitively aware enough to understand and provide consent and properly undergo visual training and rehabilitation of the device with home exercises, and have a support network. To determine eligibility, a referral to the interdisciplinary team, including a retinal doctor, a low vision doctor of optometry and a cataract surgeon, needs to occur.
A significant role of the low-vision doctor of optometry is to use an external telescope simulator (ETS) as a patient selection tool to simulate how well a patient’s vision might improve when using the IMT. The ETS should allow the patient a ≥ 1 lines (5 letter) ETDRS visual acuity gain, minimize the relative scotoma and allow the patient the experience of bi-ocular viewing, with one eye for detail and the other eye for peripheral vision awareness. This may be challenging initially, and post-IMT surgery rehabilitation will be needed to maximize this new use of central and peripheral vision, appreciating this relationship.
Once eligible, the surgical procedure is scheduled. This outpatient procedure includes cataract removal, then the IMT insertion. The corneal incision to do this requires 3 to 4 sutures post-incision, followed by a peripheral surgical iridectomy, all performed at that visit. Patients will receive post-op care and management from their surgeon or doctor of optometry, then work with low-vision doctors of optometry alone or in conjunction with low-vision occupational therapists to maximize their new vision.
Rehabilitation ranges from six to 10 sessions, and the overall study lasts 12-15 months.
As a low-vision doctor of optometry on this clinical team, I look forward to fellow doctors directing their patients to an investigation site. The plan is to share results from the study while working with the U.S. Food and Drug Administration to bring the IMT to patients suffering with vision loss from late-stage AMD.
Written by Maria Richman, O.D., a member of the AOA’s Vision Rehabilitation Committee
Disclaimer: The information contained in this article represents the opinion of the author and not the AOA. These are not clinical practice guidelines, nor has the evidence been peer-reviewed. There are additional aspects to this topic that may not be presented, or considered, based on the specifics of the case.
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