Refractive Index Engineering for Human Corneal Tissue by Femtosecond Laser Two-Photon Cross-Linking

Area of Science:

• Biomedical Optics
• Ophthalmology
• Materials Science

Background:

• Current refractive surgeries for myopia involve stromal tissue removal, posing risks of complications.
• Non-ablative, non-incisional methods are sought for safer vision correction.
• Previous research on laser-induced refractive index changes focused on hydrogels and animal tissues using complex methods.

Purpose of the Study:

• To investigate femtosecond laser-induced refractive index changes in human corneal tissue.
• To demonstrate two-photon collagen cross-linking (two-photon CXL) for refractive index modification.
• To quantify refractive index changes using direct interferometry.

Main Methods:

• Systematic investigation of femtosecond laser-induced refractive index changes in human corneal tissue.
• Utilizing two-photon excitation of riboflavin to induce collagen cross-linking.
• Employing direct interferometry for precise quantification of refractive index alterations.

Main Results:

• Successfully demonstrated two-photon CXL in human corneal tissue.
• Quantified maximum refractive index changes of 3.80 × 10^-3 in collagen hydrogel and 5.14 × 10^-3 in corneal tissue.
• Established a method for localized refractive index engineering.

Conclusions:

• Femtosecond laser-induced two-photon CXL is a viable method for altering corneal refractive index.
• This technique holds significant promise for developing non-ablative and non-incisional refractive surgery.
• Further research could lead to safer and more effective myopia correction strategies.