Refractive interventions are widespread techniques for vision correction such as myopia or astigmatism. The cornea of the patient is reshaped by surgical intervention like incisions and laser ablation of stromal tissue. The amount of tissue to remove is traditionally estimated based on experimental nomograms or geometrical approaches. Unfortunately, the change of corneal power is frequently over- or under-estimated.
We proposed an opto-mechanical simulation framework to quantify the optical outcome induced by alteration of the corneal biomechanics. This numerical framework was used to perform personalized simulations of different surgical procedures such as corneal ring implantation and arcuate keratotomy. For example, arcuate keratotomy is a surgical technique used to correct astigmatism following cataract interventions. Our numerical simulation framework could estimate the outcome of different planning options before the surgery. Based on this numerical approach, we were also able to propose optimization algorithms to automatically determine the surgical parameters optimal for each specific patient. The patient-specific optimization of the surgery proved to better control the outcome of the intervention, leads to more reliable postoperative astigmatism, and limits the risks of overcorrection.
Assessment of Intracorneal Ring Segments
Myopia is a visual impairement that will affect half of the population by 2050, with an estimated economic burden estimated at $202 billion / year. Low and mid myopia can be corrected using laser refractive surgeries. Unfortunately, the required amount of correction for high myopia is far too large for safe laser procedures. Clinically, plastic rings inserted inside the cornea represent an alternative for highly myopic patients. The rings are implanted in the middle of the cornea, and mechanically correct corneal curvature. However, it is challenging for the clinicians to select the appropriate implant for each patient, and to determine the implantation parameters to achieve the desired optical correction.
We proposed a virtual test bench to evaluate the impact of a continuous plastic ring; the Myoring. Using a cohort of 2,000 virtual eyes based on population data, we were able to evaluate about 25,000 Myoring surgeries. Simulations showed a great agreement with clinical data (±1 D error in refractive error). The study showed that the diameter of the ring is the predominant factor, while its thickness plays a fine-tuning secondary role. Numerical tools proved useful and have the potential to complement current planning tools.
Cristaline Lens Wobbling
Post saccadic lens oscillations can be measured with Purkinje images and recorded with a high-speed camera. At the end of saccadic eye movement, the lens will immediately begin to oscillate due to the inertial forces and viscoelastic behavior of intra-occular structures. We aim at replicating the experimentally observed lens wobbling using a dynamic finite element model of the complete eyeball. We hypothesize that personalized simulations of this dynamic response have the potential to provide mechanical markers able to describe the condition of the patient, based on a simple and non-invasive clinical evaluation.