[Orbscan II-assisted intraocular lens power calculation after LASIK]

Area of Science:

• Ophthalmology
• Refractive Surgery
• Biomedical Optics

Background:

• Accurate intraocular lens (IOL) power calculation is essential for achieving desired refractive outcomes after cataract surgery.
• Laser in situ keratomileusis (LASIK) alters corneal power, complicating pre-operative IOL calculations.
• Existing methods for post-LASIK IOL power estimation require validation.

Purpose of the Study:

• To assess the accuracy of keratometric values from specific Orbscan II (Bausch & Lomb, Rochester, NY, USA) mean power map zones.
• To determine the optimal Orbscan II zone for calculating IOL power after LASIK using Holladay IOL Consultant software.
• To compare IOL power predictions using post-LASIK Orbscan II data versus pre-LASIK clinical history.

Main Methods:

• A prospective study involving 118 eyes undergoing LASIK was conducted.
• Orbscan II mean power maps at 1.5, 2.0, 2.5, and 3.0 mm zones were analyzed post-LASIK.
• The 2.5 mm zone's keratometric value was applied to Holladay II and HofferQ formulas for IOL power calculation in 62 eyes and compared to clinical history-based calculations.

Main Results:

• The 1.5 mm zone underestimated post-LASIK corneal power, while the 3.0 mm zone overestimated it.
• The 2.0 mm and 2.5 mm zones provided the closest approximation to pre-LASIK calculated corneal power.
• Using the 2.5 mm Orbscan II zone with Holladay II and HofferQ formulas resulted in refractive errors of (0.47 ± 0.75) D and (0.52 ± 0.83) D, respectively, compared to clinical history.

Conclusions:

• The 2.5 mm Orbscan II zone measurement, when combined with Holladay II or HofferQ formulas, accurately predicts IOL power for cataract surgery in post-LASIK eyes.
• This method offers a reliable approach for optimizing refractive outcomes in patients with prior LASIK undergoing cataract surgery.