Corneal Filler Injection for Correction of Refractive Error in-vivo

• Applicant: Dr. Lara Buhl
• Subject Area: Ophthalmology
• Term: from 2023 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520479593

Refractive error is the incapacity to accurately focus light onto the retina, creating a blurred image. The most common refractive error types are farsightedness (hyperopia), nearsightedness (myopia), astigmatism, and presbyopia. Possible treatment options are glasses, contact lenses, or laser refractive surgery. Current laser refractive surgery changes the cornea's refractive power by ablating corneal tissue. It is considered safe and effective for myopia correction. However, for hyperopia and presbyopia correction, the refractive results are less predictable and regress over time. Therefore, we propose to correct hyperopia and presbyopia by injecting viscous, transparent filler material into a femtosecond-laser-created corneal pocket to steepen the corneal curvature. We demonstrated that filler injection into an intracorneal pocket could increase the cornea’s spherical refractive power, thereby correcting hyperopia or presbyopia ex-vivo. Whole rabbit eyes and corneoscleral discs were utilized for the procedure. 3D-Optical coherence tomography (OCT) was performed to quantify the refractive change. For hyperopia correction, a 7 mm pocket was created in the anterior stroma using a femtosecond laser system and filler injected. Thus, we observed a linear correlation between the filler volume and refractive power change. Presbyopia correction was achieved by cutting a small 2-3 mm pocket close to the posterior curvature and injecting filler material, creating bifocality with a central zone for near vision within the cornea. In addition, we showed that corneal filler injection could be used to treat overcorrection after laser refractive surgery, such as Small Incision Lenticule Extraction (SMILE) procedure. Thus, a partial increase in corneal refractive power can be induced upon filler injection into the SMILE interface. To further translate the corneal filler concept into a novel clinical application, the following aspects need to be addressed: 1) High levels of hyperopia are associated with greater astigmatism. Therefore, simultaneous correction of axial hyperopia and regular astigmatism is critical to ensure optimal refractive results. We plan to assess the metrics of combined spherical and astigmatic correction by injecting filler into intracorneal pockets of different ovalities using ex-vivo rabbit eyes. 2) The in-vivo biocompatibility and stability of the filler material used are essential for the success of this approach. A novel modified filler material was recently developed that meets the optical requirements. Now, we plan systematic animal studies using New Zealand rabbits to evaluate the in-vivo tolerability of the filler material over a three-month period. Different pocket sizes and depths will be used as they impact the cornea’s biomechanical properties differently. Throughout the study, OCT and slit lamp examinations of filler compatibility and stability will be performed, as well as postmortem corneal immunohistochemistry.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Reginald Birngruber, Ph.D.