Purpose: Age-related macular degeneration (AMD) severely reduces central vision and is often associated with cataracts. Improved quality of vision in affected patients may be achieved by the implantation of a pair of intraocular lenses in a Galilean-telescopic configuration. A common drawback with this approach is the large refractive error that results from inconsistencies in the positioning of the two lenses and the large incision required to implant them. In this context, the purpose of this study was to develop a new intraocular telescope with an optimized optical design more tolerant to a variety of surgical outcomes.
Methods: Ray-tracing techniques were used to design a Galilean telescope within a realistic eye model such that a positive lens is placed in the ciliary sulcus and a second, negative lens in the capsular bag. To facilitate surgical implantation, a high refractive index, soft hydrophobic material was used for the lenses. The aim was to produce a tilt of 3 degrees and a magnification of around 1.2. The prismatic effect was achieved by the relative decentration of the two lenses and additional optical refinements were incorporated to minimize associated astigmatism and coma. The distance between the two lenses after implantation is a critical factor in determining the quality of the retinal image.
Results: We were able to generate an optimized optical design that reduces off-axis aberrations and produces quality retinal images for a range of relative positions of the two lenses in the telescope. We were able to increase the tolerance in lens positioning by at least six-fold. Whilst the design sacrifices some image quality at best focus to achieve this, it produces images with sufficient quality for the purposes of enhanced extrafoveal viewing. Since the lenses may also be implanted through a small incision, induced corneal astigmatism is also minimized.
Conclusions: A new optical design has been devised for an intraocular mini-telescope to be implanted in patients with macular disorders. The system confers both optical and surgical advantages that make it suitable for extension to a wider patient base.