Intraocular lens power calculation after decentered photorefractive keratectomy

Area of Science:

• Ophthalmology
• Refractive Surgery
• Cataract Surgery

Background:

• Photorefractive keratectomy (PRK) is a common procedure for correcting myopia.
• Cataract development can occur independently of prior refractive surgery.
• Accurate intraocular lens (IOL) power calculation is crucial for successful cataract surgery outcomes.

Observation:

• A 59-year-old patient with a history of high unilateral myopia treated with PRK developed a progressive nuclear cataract.
• Standard methods for IOL power calculation (automated keratometry, computerized videokeratography) were unsuccessful due to a decentered PRK ablation zone.
• This resulted in artificially steep keratometric readings and significant postoperative hyperopia.

Findings:

• The decentered ablation zone after PRK led to inaccurate keratometric measurements.
• Inaccurate measurements resulted in incorrect IOL power selection, causing significant postoperative hyperopia.
• An IOL exchange was required to correct the refractive error.

Implications:

• Automated keratometry and videokeratography may be unreliable for IOL calculation in post-PRK eyes with decentered ablation zones.
• A modified approach, such as subtracting the PRK-induced refractive change from preoperative keratometry, may yield more accurate IOL power calculations.
• This case highlights the importance of considering prior refractive surgery when planning cataract surgery and emphasizes the need for alternative IOL calculation methods.