Real-time pachymetry during photorefractive keratectomy using optical low-coherence reflectometry.

Area of Science:

• Ophthalmology
• Biomedical Optics
• Surgical Technology

Background:

• Accurate intraoperative measurement of central corneal thickness is crucial for refractive surgery.
• Photorefractive keratectomy (PRK) involves laser ablation of corneal tissue, requiring precise depth control.
• Noncontact methods are desirable for intraoperative corneal assessment to minimize contamination and trauma.

Purpose of the Study:

• To evaluate optical low-coherence reflectometry (OLCR) as a noncontact method for measuring central corneal thickness during photorefractive keratectomy.
• To assess the feasibility of real-time OLCR measurements throughout the PRK procedure.
• To determine the accuracy of OLCR in calculating actual laser ablation depths, considering intraoperative corneal thinning.

Main Methods:

• Optical low-coherence reflectometry (OLCR) was employed for noncontact measurement of central corneal thickness.
• Continuous on-line measurements were taken intraoperatively: before surgery, after epithelium removal, during laser ablation, and post-ablation.
• Corneal thinning due to evaporation was quantified using OLCR to establish a baseline rate (-0.14 microm/s).

Main Results:

• OLCR successfully performed continuous, on-line measurements of central corneal thickness during PRK.
• A baseline corneal thinning rate of -0.14 microm/s was determined for the initial 5 minutes post-epithelium removal.
• Calculated ablation depths using OLCR showed a maximum difference of +/-10 microm compared to planned ablations (34-92 microm).

Conclusions:

• Optical low-coherence reflectometry is a viable noncontact tool for intraoperative central corneal thickness monitoring during PRK.
• Accounting for evaporative thinning improves the accuracy of measured laser ablation depths.
• OLCR offers potential for enhanced precision and safety in refractive surgical procedures.