New lenses for AMD
Many types of telescopic and non-telescopic implants are now available for eyes with macular disease
Patients with age-related macular degeneration (AMD) are now being treated with a range of intraocular lenses, but all have their specific limitations and potential complications, a recent review indicates.
“We really need further independent clinical studies with longer follow-up data prior to the routine use of these implants,” said lead author Andrzej Grzybowski MD, PhD, MBA, University of Warmia and Mazury, Olsztyn, and Foundation for Ophthalmology Development, Poznan, Poland, whose study appeared in Graefes Archives of Clinical and Experimental Ophthalmology.
Dr Grzybowski and colleagues reviewed the literature for prospective and retrospective studies of implantable devices in the treatment of various stages of AMD. They found seven types of IOLs recommended for AMD: an implantable miniature telescope called the IOL-VIP System, the Lipshitz macular implant, the sulcus-implanted Lipshitz macular implant, the LMI-SI, the Fresnel Prism Intraocular Lens, the iolAMD and the Scharioth Macula Lens.
He noted that telescope implants magnify the image projected on the retina and/or skew the image away from the central scotoma. The most common designs are based on the Galilean telescope, consisting of two lenses with high positive and negative power, respectively.
The implantable miniature telescope (IMT) enlarges patient’s central 20-24° field of view by up to three-fold. It is composed of a 4.4mm telescope with a PMMA base that sits in the capsular bag.
The IOL-VIP System consists of two IOLs, a high minus-power biconcave IOL in the capsular bag and a high plus-power biconvex IOL in the anterior chamber. The two PMMA lenses together provide a 1.3-fold magnification and shift the enlarged image towards the preferred retinal locus.
The iolAMD is another double-implant system, but in this case the high plus-power lens is implanted in the sulcus. The high plus-power IOL has a hyper-aspheric-optic that is slightly de-centred. The lenses provide a 1.2-fold magnification.
Meanwhile, the Lipshitz macular implant (LMI), and sulcus-implanted Lipshitz macular implant (LMI-SI, now marketed as the Orilens, OptoLight) is based on a reflecting telescope, and combines a primary concave mirror and a secondary convex mirror within a normal IOL configuration. In addition to providing a 2.5-fold magnification, the LSI implants also provide normal unmagnified peripheral vision.
There are also two lenses that operate on entirely different principles. These include the Fresnel Prism Intraocular Lens, which provides no magnification but instead displaces the retinal image to a healthy part of the retina.
And finally, there is the add-on bifocal Scharioth Macula Lens (A45 SML, Medicontur), designed to provide near vision to the pseudophakic AMD patients while preserving normal peripheral vision.
RESULTS GENERALLY GOOD
To date, the best researched is the IMT. In the two-year, prospective, 28-centre IMT-002 pivotal study, 90% of 217 patients achieved an improvement of two or more lines of ETDRS.
The most common complications for the IMT were corneal oedema iris damage/prolapse and capsular rupture. No complications were reported in the small series published regarding the IOL-VIP and the Scharioth macular lens. All patients with the LMI and LMI-SI had slight glare and a small proportion experienced difficulties with neuroadaptation. One patient who underwent monocular implantation of the iolAMD had diplopia.
Dr Grzybowski noted that the implants differ in terms of the incision size required. The IMT requires a 10.0mm incision. The LMI LMI-SI and the IOLVIP require a 7.0mm incision, whereas the hydrophobic acrylic IOL AMD and the Scharioth lens can be injected with a standard injector system through a 3.0mm incision.
He added that none of the lens-based telescopic implants are suitable for pseudophakic patients because they require implantation in the capsular bag. In contrast, the sulcus-implanted Scharioth lens and the LMI-SI can be implanted either at the same time as the conventional IOL or any time thereafter.
Another important consideration is the amount of training and neuroadaptation required. For example, the IOL-VIP requires two weeks of preoperative training and three months of postoperative training, and some authors report that patients require three-to-six months of training after IMT implantation.
“Much of the success will depend on the commitment and dedication of the patient towards these visual rehabilitation,” he added.
For more details please see A Grzybowski et al. Graefes Arch Clin Exp Ophthalmol 255 (9), 1687-1696. 2017 Jul 24.
Andrzej Grzybowski: email@example.com