C. DeBoer

Port geometry and its influence on vitrectomy.

Purpose: To determine the influence of port geometry on water and vitreous flow rates and test novel vitreous cutter tips in specific surgical situations. Methods: Custom 20-gauge and 25-gauge vitreous cutter tips with different sized ports were evaluated through porcine vitreous and water flow rates. Five cutter tips were designed and fabricated for specific surgical functionalities. Tips were compared with a normal control tip and evaluated by water and porcine vitreous flow rates, vacuum level required to cut porcine retina, time required to cut and aspirate a porcine lens, and surgical evaluation in enucleated porcine eyes. Results: Both vitreous and water flow asymptotically approached a maximum flow as the port diameter increased. Some tips removed water faster than the normal control tip, but none removed vitreous or lens faster. Several tips required higher vacuum levels to cut retina than the normal tip. Conclusions: Increasing the port diameter of a vitreous cutter to increase flow becomes less effective as the port becomes larger. Furthermore, modifying the port geometry of a vitreous cutter affects its surgical interactions with tissue. In the future, combinational instruments or surgery specific instruments may allow the surgeon to use an optimal port for a specific surgical task.

Biomimetic Accommodating Intraocular Lens Using a Valved Deformable Liquid Balloon

Objective: Presbyopia is a common age-related condition that prevents people from focusing on near objects. The etiology of presbyopia continues to be debated, but the end effect of all postulated mechanisms is the lack of deformation of the human lens. Using our understanding of the biomechanical properties of the natural human lens, we created a unique accommodating intraocular lens. Although this lens can be used for lenticular disease such as myopia and hyperoperopia, this study addresses the needs of cataract patients with presbyopia. Methods: The lens was implanted into presbyopic human cadaver eyes. Focal length of the lens was measured with simulated muscle contraction. Lens dimensions were measured using artificial tissue and a finite-element analysis (FEA) to simulate accommodation. Lens power was measured at various fill volumes. Accelerated soak testing for an equivalent of 7.4 years was performed and lens weight and optical transmittance were measured. Results: Previously presbyopic human eyes were able to accommodate between 2.0 and 7.4 diopters after lens implantation. FEA and lens measurements demonstrated a change in curvature of the anterior and posterior portions of the lens during accommodation. After accelerated aging, lens weight remained unchanged and optical transmission was 96%. Lens power increased with fill volume. Conclusion: A deformable liquid lens reversed presbyopia, can be individualized by optically adjusting for each patient, is stable for long periods of time, and is compatible with minimally invasive surgical techniques. Significance: A deformable liquid-filled lens can significantly improve accommodation over the presbyopic natural lens.