Cyclotorsional eye movements during a simulated PRK procedure

Area of Science:

• Ophthalmology
• Optometry
• Biomedical Engineering

Background:

• Accurate eye alignment is critical for corneal surface ablation procedures like photorefractive keratectomy (PRK).
• While horizontal and vertical eye movements are often monitored, the impact of cyclotorsional (rotational) movements is less understood.
• Dynamic cyclotorsions can significantly affect surgical outcomes if not accounted for.

Purpose of the Study:

• To measure dynamic cyclotorsional eye movements in emmetropic subjects during a simulated PRK procedure.
• To investigate the influence of visual stimulus clarity and body position (upright vs. supine) on cyclotorsion.

Main Methods:

• Ten emmetropic subjects underwent measurements of cyclotorsional eye movements using a 3D videoculographic system (SMI).
• Measurements were taken in both upright and supine positions with fixation on a target that was either clear or optically degraded.
• Data analysis involved comparing measurements between different conditions using Student's t-test.

Main Results:

• Cyclotorsional movements were significantly greater when subjects fixated on an optically degraded stimulus (P=0.04 upright, P=0.0002 supine).
• A significant difference in eye orientation was observed between upright and supine positions (P=0.03).
• Even after correcting for positional differences, cyclotorsional movements were significantly higher in the supine position (P=0.0043 clear, P=0.0008 degraded).

Conclusions:

• The study revealed a substantial range of cyclotorsional eye movements during simulated PRK.
• These findings indicate that 3D eye-tracking technology could potentially improve the precision of surface ablation.
• Enhanced tracking is particularly relevant for procedures involving high astigmatism or wavefront-guided treatments.