Article

Patient Selection for the Implantable Miniature Telescope

Treatment goes beyond surgery.

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The Implantable Miniature Telescope (IMT; VisionCare, Inc.) is a viable option for people who otherwise have limited vision due to end-stage age-related macular degeneration (AMD) (Figure 1). Selecting the appropriate candidate for this device, however, requires a multidisciplinary team with an integrative approach. Educating the prospective patient preoperatively on what to expect after implant could facilitate the transition to his or her new vision status and thus, itself, contribute to an improved quality of life. The following is a discussion of the current literature on AMD and the IMT device in tandem with our care team’s account of ensuring the implantable device is suitable for our patients.

Figure 1. Clinical image of the Implantable Miniature Telescope (VisionCare, Inc.).
IMAGE COURTESY REY T. PANGILINAN, MD, SOUTHERN CALIFORNIA PERMANENTE GROUP

AGE-RELATED MACULAR DEGENERATION AND AN AGING POPULATION

Age-related macular degeneration causes progressive and irreversible damage to the retina, resulting in loss of central vision. It is the third leading cause of irreversible visual impairment worldwide and the leading cause of blindness in industrialized countries.1-3 By 2050, the number of people aged 65 years and older in the United States is expected to be 82.7 million — more than double from 2005 levels. It is estimated from this that 17.8 million individuals will have early AMD and 3.8 million will have late AMD.4 As more patients with end-stage AMD become diagnosed, there will be a higher demand for ophthalmologists, optometrists, occupational therapists, and a well-established support system to care for an increasing population with visual impairments.

Although several treatment options exist for mild-to-moderate (early) neovascular AMD, such as anti-VEGF injections, laser treatments, and photodynamic therapy,5-10 end-stage AMD patients are left with little to no functional vision. There is still no pharmacologic or surgical treatment capable of reversing vision loss from disciform scar or geographic atrophy (GA),11,12 but there is an implantable device available for these patients, the IMT. The IMT is the first device to be approved as a therapy for patients with end-stage AMD. After positive results from a long-term, multicenter clinical trial including 217 patients, the FDA reduced the acceptable age for IMT candidates from 75 years to 65 years of age in 2014.13 The rest of this discussion on patient selection refers to the use of the IMT from VisionCare, Inc.

PATIENT ELIGIBILITY

VisionCare, Inc. developed a multistep treatment program called CentraSight to manage patients through diagnosis, surgical evaluation, and postoperative care, outlined throughout the rest of this paper.

DEVICE AND PROCEDURE DETAILS

In the surgical procedure described by Colby and Chang,14 the IMT, in combination with the cornea, produces 2.7x magnification of the retinal image, projecting it over an approximately 55° area of the central and peripheral retina, which translates to approximately a 20° field of view. It has an optimum focusing distance of 3 meters and a depth of focus between 1.5 meters and 10 meters. When implanted in one eye, the magnified view improves central vision while the fellow eye is used for navigation and depth perception. Once implanted, the IMT is used to enlarge objects in the central visual field and focus them onto healthy areas of the retina not affected by AMD, allowing individuals to recognize objects that they otherwise could not see. Despite the field of view being larger than an equivalent external telescopic device, the significant reduction in visual field means the IMT is not suitable for bilateral implantation, or for single-eyed patients.

CRITERIA FOR DEVICE IMPLANTATION

The IMT is approved for patients with a visual acuity (VA) between 20/160 and 20/800 resulting from bilateral central scotomas associated with end-stage AMD. Patients must also have findings of disciform scar or GA, cataract, and show an improvement of at least 5 letters with the aid of an external telescope in preoperative testing. Refraction of the target eye should fall within − 6 DS and + 4 DS (spherical equivalent). The IMT is currently indicated for phakic eyes; however, a multicenter trial currently underway in the United States is investigating the safety and effectiveness of implanting the IMT in pseudophakic patients (ClinicalTrials.gov identifier NCT03011554).15

EVALUATIONS FROM LOW-VISION SPECIALISTS

According to Amy Pedersen, OD, a low-vision specialist at Kaiser Permanente, Riverside Medical Center, eye selection is a key component in patient selection for the IMT. Dr. Pedersen shared the ability to ambulate using the nonimplanted eye is similar to modified monovision. Research has shown that appropriate eye selection is imperative to patient satisfaction and success.16 Current practice says the predicted VA of the implanted eye during simulation should be at least 2 logMAR lines better than that of the best-corrected VA in the fellow eye. In the absence of this difference, there may be no incentive to use the implant eye and the patient is very likely to continue to use their fellow eye for activities of daily living requiring detailed vision. If both eyes satisfy this criterion, ocular dominance with respect to mobility and aiming are assessed to select the eye for implantation.16

MANAGING PATIENT EXPECTATIONS

Qualifications for the device aside, our team has found that motivation, psychosocial status, and support network are key in determining success with the IMT. When we first meet a patient, we have an in-depth discussion about what they know about the device, their goals for use of the implant, and what outcome they can realistically expect. These expectations include the overall surgery experience, the significant amount of postsurgical training, and the final real-world experience. For example, if patients expect to get their driver’s license back and have normal vision as if they were 20 years old again, they will be quite frustrated with the outcome. Part of the selection process includes a simulator so the patient will have a sense of what vision they will have with the telescope system. Throughout this process the team should get a sense of the patient’s motivation and willingness to try something new. A patient who is seeking a quick fix and expects perfect vision from postoperative day 1, or is inflexible mentally, emotionally, and physically with the postsurgical training, will not be a good candidate.

In addition, we require that the patient’s family and caregivers be present during the evaluation. Family and caregivers need to understand that their commitment is essential to ensuring patients attend their many appointments pre- and postsurgery for training. It is also helpful to have an informed support base that understands what the patient is going through and what vision they will be experiencing so they can help. These devices are an investment in the qualified patient; therefore, we need to ensure everything is in place for maximal success well before the device is implanted.

Research has shown that about 10% to 30% of patients with AMD develop clinically significant depression, which is associated with greater levels of disability, medical costs, and mortality.17-19 According to Williams et al, AMD has not been well studied regarding its impact on daily life. Individuals with AMD experienced significant reductions in key aspects of daily life. Their ratings for quality of life (average Quality of Well-Being Scale score of .581) and emotional distress (average Profile of Mood States total score of 65.36) were significantly worse than those for a similarly aged community of adults and were comparable with those reported by people with chronic illnesses (eg, arthritis, chronic obstructive pulmonary disease, acquired immunodeficiency syndrome, and bone marrow transplants). Patients with AMD were also more likely than a national sample of elderly individuals to need help with daily activities. Visual acuity was related to ability to carry out daily activities (Instrumental Activities of Daily Living, r=.28, P=.008). Quality of life ratings were significantly related to the ability to carry out daily activities (r=-0.38, P=.001), self-rated general health status (r=-0.21, P=.05), and emotional distress (Profile of Mood States total score, r=-.25, P=.02).20 Given that the severity of quality of life impairment is often more severe than treating physicians realize,21 our team has found that discussing proper expectations for the IMT and clearly educating the patient on the device’s limitation and how it should improve what vision is left is imperative for a successful outcome.

POSTOPERATIVE MANAGEMENT

After surgery, the final, and potentially most crucial, treatment step is the rehabilitation process managed by the low-vision optometrist and an occupational therapist. This team approach includes several visits over 3 to 4 months by the optometrist and weekly or bimonthly training with the occupational therapist (OT) over the same time period. The optometrist helps patients with best correction for the implant and the fellow eye, managing binocular viewing strategies, possible glare management and other low-vision aspects. The OT educates patients on how to use their new visual status and assists them in reaching their preoperative therapy goals. Some of these goals have, in our care team’s experience, included activities such as reading, playing cards, watching television, and seeing loved ones’ faces better than before. Postsurgical rehabilitation requires a great deal of support from caregivers and/or family members to transport patients to their appointments and for overall compliance to the patients’ treatment plan.

In the case of progression and wet AMD, patients may wonder if treatment in the implanted eye is still feasible. One case study has shown a successful outcome from focal laser photocoagulation through the telescope.22 Also, intravitreal injections can be safely performed in an eye with a telescope using standard optical coherence tomography imaging and by taking into consideration the unique geometric dimensions of the telescope.23

CONCLUSION

Randomized, clinical trials studying the IMT’s impact on VA and quality of life remain limited.15 Therefore, criteria for patient selection remains primarily subjective. Further research on patients’ long-term experiences with the IMT device may lead to a more standardized approach in the patient selection process and may be an invaluable resource to patients transitioning to a new vision status. In our experience, for the patients who have carefully been selected as outlined above, it is clear the device can be a “life changer,” as it has been described by a few of our satisfied patients. RP

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