Intraocular lens power calculation for eyes after refractive keratotomy

Area of Science:

• Ophthalmology
• Refractive Surgery
• Cataract Surgery

Background:

• Calculating intraocular lens (IOL) power in eyes with prior refractive keratotomy presents challenges.
• Standard keratometry often inaccurately measures central corneal power after refractive surgery.

Purpose of the Study:

• To propose and evaluate methods for accurate intraocular lens (IOL) power calculation in eyes with a history of refractive keratotomy.
• To improve the precision of preoperative measurements for cataract surgery in post-refractive surgery eyes.

Main Methods:

• Clinical history method: Subtracting refractive surgery-induced myopic shift from pre-surgery corneal power.
• Contact lens method: Determining corneal power by measuring refractive changes with a known-base curve contact lens.
• Videokeratography: Measuring central corneal power within a 3-mm zone for enhanced accuracy.

Main Results:

• Standard keratometers provide inaccurate corneal power measurements post-refractive keratotomy.
• Regression formulas are less effective than third-generation theoretic formulas for post-refractive surgery eyes with flatter corneas.

Conclusions:

• Utilize corneal power derived from clinical history, contact lens refraction, or videokeratography for IOL calculations.
• Employ third-generation theoretic formulas (Hoffer Q, Holladay, SRK/T) for precise IOL power determination in post-refractive surgery eyes.