Aspheric Optical Zones: The Effective Optical Zone with the SCHWIND AMARIS

Area of Science:

• Ophthalmology
• Refractive Surgery
• Corneal Surgery

Background:

• Laser epithelial keratomileusis (LASEK)/epi-LASEK is a surgical procedure for correcting refractive errors.
• Understanding the effective optical zone (EOZ) is crucial for achieving optimal visual outcomes.
• Myopic astigmatism correction requires precise ablation parameters.

Purpose of the Study:

• To evaluate the effective optical zone (EOZ) in eyes undergoing LASEK/epi-LASEK for myopic astigmatism.
• To compare the achieved EOZ with the planned optical zone (POZ).
• To analyze factors influencing the difference between EOZ and POZ.

Main Methods:

• Retrospective evaluation of 20 LASEK/epi-LASEK treatments for myopic astigmatism.
• Corneal wavefront analysis using Keratron Scout pre- and post-operatively.
• Calculation of EOZ based on changes in higher-order wavefront aberrations (ΔRMSho, ΔSphAb, RMS[ΔHOAb]).

Main Results:

• At 6 months, spherical equivalent (SE) was -0.05±0.43 D, with 90% of eyes within ±0.50 D.
• EOZ(ΔRMSho) and EOZ(ΔSphAb) were comparable to the planned optical zone (POZ).
• EOZ(RMS[ΔHOAb]) was significantly smaller than the POZ, especially for smaller POZ or larger SE corrections.

Conclusions:

• EOZ based on higher-order aberrations generally matches POZ, but is smaller when considering the RMS of the change in aberrations.
• Larger POZ (>6.75 mm) tend to yield EOZ at least as large as POZ.
• A nomogram is recommended for POZ <6.75 mm to optimize EOZ in LASEK/epi-LASEK procedures.