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Published on: October 21, 2022
Functional optical zone of the cornea.
Juan Tabernero1, Stephen D Klyce, Edwin J Sarver
1Laboratorio de Optica/Departmento Fisica, Universidad de Murcia, Murcia, Spain.
Investigative Ophthalmology & Visual Science
|February 28, 2007
Summary
New objective methods accurately measure the functional optical zone (FOZ) after laser eye surgery. These tools help optimize keratorefractive surgery to reduce night vision issues by ensuring adequate FOZ size.
Area of Science:
- Ophthalmology
- Corneal Surgery
- Optical Engineering
Background:
- Keratorefractive surgery can cause visual disturbances like glare and halos when the treated area is smaller than the pupil.
- Enlarging the surgical treatment zone improves optical outcomes but faces geometric limitations, potentially impacting night vision.
- The functional optical zone (FOZ) is defined as the treated area providing good optical performance.
Purpose of the Study:
- To develop and evaluate three objective methods for measuring the functional optical zone (FOZ) after keratorefractive surgery.
- To assess the impact of LASIK on the FOZ and its correlation with visual performance.
- To identify practical methods for characterizing corneal treatment profiles and improving surgical outcomes.
Main Methods:
- Corneal topography data from normal and LASIK-corrected eyes were analyzed.
- Three methods were used: uniform axial power (FOZ(A)), corneal wavefront RMS error (FOZ(R)), and radial modulation transfer function (FOZ(M)).
- Measurements were taken as a function of simulated pupil size to determine the FOZ.
Main Results:
- The mean FOZ was smaller in LASIK-corrected eyes (6.0-6.9 mm) compared to normal eyes (7.6-9.1 mm), with an average decrease of 1.8 mm.
- All three developed methods showed acceptable and statistically significant correlations after LASIK.
- The uniform axial power method (FOZ(A)) demonstrated ease of implementation and good correlation with other methods.
Conclusions:
- The developed objective methods are valuable for characterizing corneal treatment after refractive surgery.
- The uniform axial power method (FOZ(A)) is recommended for its practicality and correlation with other measures.
- Measuring FOZ aids in refining surgical algorithms to minimize night vision impairments by ensuring adequate mesopic pupil coverage.
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