Validation of confocal microscopy through focusing for corneal sublayer pachymetry

Area of Science:

• Ophthalmology
• Biomedical Optics
• Corneal Imaging

Background:

• Accurate corneal thickness measurement is crucial for diagnosing and managing various ocular conditions.
• Existing pachymetry methods may have limitations in precision and ability to visualize corneal sublayers.
• Confocal microscopy offers potential for high-resolution imaging of corneal structures.

Purpose of the Study:

• To assess the accuracy and precision of confocal microscopy through focusing (CMTF) for determining corneal sublayer thickness (pachymetry).
• To evaluate the reliability of CMTF in vivo and identify factors influencing measurement accuracy.

Main Methods:

• CMTF was performed using a tandem scanning confocal microscope with a nonapplanating objective.
• Accuracy was validated with custom PMMA contact lenses of known thickness and curvature.
• In vivo studies in rabbits assessed immersion fluid stabilization and effects of prolonged examination.

Main Results:

• CMTF measurements consistently fell within +/-1.0 microm of certified values for calibration lenses.
• In vivo CMTF identified and corrected for z-axis motion due to immersion fluid stabilization and eye movements.
• Prolonged examination caused minor, measurable swelling in the corneal stroma and epithelium.

Conclusions:

• Confocal microscopy through focusing (CMTF) is a highly accurate and precise method for corneal sublayer pachymetry.
• CMTF concurrently visualizes cellular morphology, enhancing diagnostic potential.
• Optimizing CMTF involves allowing stabilization time and employing repeated scans to account for motion artifacts.