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Femtosecond laser assists implantation of miniature telescope
A surgeon describes cataract surgery coupled with placement of the Implantable Miniature Telescope for AMD.
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Age-related macular degeneration affects central vision and can result in significant visual acuity deterioration, thus negatively affecting a patient’s overall lifestyle, driving privileges and job and often leading to depression and increased dependence on caregivers, family members and friends. It has been estimated that about 1.8 million individuals in the U.S. are afflicted by advanced AMD. The yearly incidence of bilateral late AMD in the U.S. has been estimated to be in the range of 60,000 to 80,000. Geographic atrophy, disciform scar or both result in bilateral central scotomas that can progress to end-stage AMD that may be moderate or profound.
Unlike geographic atrophy, some treatment options for choroidal neovascularization include intravitreal anti-VEGF injections, laser photocoagulation and photodynamic therapy. In the absence of expanded, uniformly effective treatment options for bilateral end-stage AMD, the Implantable Miniature Telescope (IMT, VisionCare) for patients 65 years and older with stable, severe to profound vision impairment due to bilateral end-stage AMD-related central scotomas appears to be a welcome modality for a subset of AMD patients. The devise comprises a fixed-focus telescopic system that magnifies visual objects in the central visual field while reducing the peripheral field in the treated eye. Hence, it is only implanted in one eye, while the untreated opposite eye provides added peripheral vision.
Because corneal clarity is important for optimal vision with an IMT, any corneal decompensation associated with cataract surgery can be deleterious to the final visual outcome. This becomes even more important when dealing with a mature brunescent cataract.
In this column, Dr. Pham describes his technique and initial results in performing femtosecond laser-assisted cataract surgery and implantation of an IMT device. Continued long-term monitoring is an essential and integral part of evaluating the safety and overall efficacy of such a treatment modality.
Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor
The Implantable Miniature Telescope is a prosthetic device that is the only option currently available for restoring some vision in patients with end-stage AMD. But there are a number of challenges with implanting this relatively large device and helping patients to successfully adapt to their vision with it.
The most common complication of IMT surgery is corneal edema, with a number of patients in clinical trials going on to require a corneal transplant. Manipulation of the telescope, plus the high phaco energy required to emulsify the often quite advanced cataracts in these patients, can result in excessive endothelial cell loss and corneal decompensation.
I started to use the femtosecond laser on black cataract cases in July 2012 and became convinced that this approach might work in patients with untreatable end-stage AMD who have advanced cataracts.
I first tried it in a 65-year-old Vietnamese male patient who grew up in the Mekong Delta. He had bilateral focal geographic AMD and central atrophic scars of the macula affecting the fovea in both eyes. Over the previous decade, this patient had gone from being a highly compensated technology worker to losing his job, driver’s license and independence as his vision declined. By the time of surgery, he had brunescent cataracts and uncorrected acuity of 20/200 in both eyes. Best corrected near acuity was 20/80 at 1.6 m. This case, including extensive preoperative diagnostic findings, is described in detail in a recently published case report (Figure 1).
Pattern electroretinogram confirmed the widespread photoreceptor and inner retina damage. Microperimetry helped us localize the visual defects and target areas of functioning retina at which to point the telescope. Visual evoked potential measurement and the Centrasight external simulator (VisionCare) also allowed us to evaluate in advance how the patient might see with the telescope.
I used the Catalys femtosecond laser (Johnson & Johnson Vision) with a 14-mm diameter suction ring to pre-soften the nucleus. In the laser’s active mode, I manually expanded and moved the auto-planned capsulorrhexis to create a 7-mm custom capsulorrhexis that was designed specifically to hold the neck of the telescope and point it to the desired location of healthy retina as identified by microperimetry. I also created arcuate incisions with the Catalys laser to neutralize surgically induced astigmatism (SIA) from the large 13-mm incision required to implant the IMT. Absorbable interrupted sutures also helped to reduce SIA.
The telescope, which is intended to magnify images for central vision, was implanted in the left eye and a Softec HDO IOL (Lenstec), the largest IOL optic available, was implanted in the right eye to maximize peripheral vision with that eye.
On the first day after surgery, the cornea was clear; it has remained free of edema throughout the postop period, now out to 6 months (Figure 2). The patient was able to read 20/50 and ambulate unassisted in the first days after surgery. The telescope eye had 1.04 D of astigmatism at 36° on day 1, which had resolved to just 0.48 D at 180° by day 12.
I have since performed two more femto IMT cases and have a fourth scheduled.
It is of utmost importance that cataract surgeons refrain from performing cataract surgeries on patients with either unilateral or bilateral end-stage macular degeneration. These patients need thorough examinations performed by qualified retinal specialists to determine whether or not they are or will be good candidates for femtosecond laser-assisted implantation of the IMT. If they qualify for the procedure, cataract surgery should be deferred until which time the procedure is indicated. Removal of the cataract may not improve their vision, and such removal will preclude the implantation of the IMT. At the time of this publication, IOL exchange for the IMT is not yet approved by the FDA.
- References:
- Hudson HL, et al. Ophthalmology. 2006;doi:10.1016/j.ophtha.2006.07.010.
- Pham R, et al. Am J Ophthalmol Case Rep. 2017;doi:10.1016/j.ajoc.2017.05.006.
- For more information:
- Randal T. Pham, MD, MS, FACS, can be reached at 989 Story Road, Suite 8063, San Jose, CA 95122; email: randal.pham@alumni.ucsf.edu.
- Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at email: tjcornea@gmail.com.
Disclosures: Pham reports he is a paid consultant for VisionCare. John reports no relevant financial disclosures.