Abstract
Purpose::
An accommodative intraocular lens ("AIOL") with shifting cubic optical elements is currently in development. Such lens can replace the natural lens of the human eye, for e.g. treatment of cataracts, and is expected to restore overall vision and may restore accommodation of the eye as well. The biomechanical aspects of a prototype were studied in (a) - artificial silicone capsular bags and (b) - animals. The AIOL is manufactured from a hydrophilic acrylate by precision lathing and provides, in vitro, 4 diopters of accommodation by a shift of 0.75mm of the optical elements.
Methods::
Artificial silicone capsular bags. - The AIOLs were implanted in artificial capsular bags which were mounted in a stretching device to simulate accommodation. Shift of the optical elements and the gap between the elements as well as tilt of the AIOL during the accommodative process were measured by HF ultrasound.Animal trials. - The AIOL were implanted in five rabbit eyes unilateral by conventional cataract surgery with forceps. Ultrasound biomicroscopy, examination by slit-lamp and photodocumentation of dilated eyes were carried out to evaluate the overall positioning of the AIOL, the condition of the capsular bag and the degree of capsular opacification during the 1st, 3rd, 6th and 10th month post-op.
Results::
Artificial silicone capsular bags. - The AIOL remained well aligned and the optics remained parallel and equidistant during repeated simulated accommodation. No tilt or other misalignment was observed.Animal trials. - No complications occurred during the implantations, with one eye developing slight corneal opacity due to surgical trauma. All AIOLs are well positioned in the capsular bag with only minimal tilting in two eyes at 10 months post-op. Two eyes show slight peripheral capsular opacification but the optics remained clear and one eye shows slight peripheral cell migration into the gap between the optics which optics also remained clear.
Conclusions::
The AIOL performs well in simulated accommodation and seems biocompatible with the eye with a very low rate of secondary cataract formation. Although the rabbit eye is a well proven model for the human eye in many biological aspects the rabbit eye does not accommodate. We have therefore not yet been able to validate the AIOL’s accommodation in vivo. Accommodation will be a main topic of future clinical trials.
Keywords: presbyopia • cataract • intraocular lens