The accommodation of the crystalline lens allows for sharp vision in the close and distant range. Conditions such as cataracts can make it necessary to replace the natural tissue with an artificial intraocular lens (IOL), which lacks the ability to accommodate. The alternatives that are currently under investigation include accommodating IOLs or refilling the lens bag with hydrogels. Here, we investigate the possibility to remove and refill only the central part (nucleus) of a cataract lens, thereby preserving its ability to accommodate. This approach avoids damage to the lens cortex to prevent stiffening of the capsular bag—a significant drawback of complete lens refilling. The nucleus of the lenses of porcine eyes was fragmented via fs-laser treatment and removed by phacoemulsification. The lens’s mechanical properties, ray tracing properties and curvature were investigated with an in-house developed measurement setup, including a lens stretching device for simulation of accommodation. This yielded quantifiable data on the transparency, accommodation capabilities and focus shift of treated versus untreated lenses. While native transparency could not yet be achieved, refilled eyes exhibited the same focal shift as non-refilled, indicating functional accommodation. Measurements of the curvature revealed stronger flattening of refilled eyes. Apart from the study of partial lens refill, the stretcher device and respective protocols presented here possess great potential in IOL development, presbyopia research or characterization of model lenses.
Surgery with fs-laser in the posterior part of the eye could be useful for separation of tractional epiretinal membrane and vitreous floaters treatment. However, focus degradation occurs near the retina due to induced aberrations by cornea and lens. To overcome this issue, adaptive optics with wavefront sensor and wavefront modulator can be utilized. We demonstrate an alternative concept for image guided femto second laser (fs-laser) surgery in the posterior eye with wavefront sensorless adaptive optics (WFSLAO). Our laboratory setup consists of an 800 nm fs-laser and a superluminescent diode (SLD) with 897.2 nm central wavelength. The SLD is used for optical coherence tomography (OCT) whereby the light for the OCT sample arm and the fs-laser share the same optical path which contains a deformable mirror, scanner and focusing optics. Energy calibrated photodiodes are used to measure the threshold energy for a laser induced optical breakdown inside a water filled chamber that acts as simple eye model. OCT image based metrics were used to determine a set of Zernike polynomials that describe a near optimal deformable mirror state. Such a mirror state improved OCT resolution and at the same time lowered the required fs-laser energy for a laser induced optical breakdown inside the eye model substantially.
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