IOL Power Calculation in Short and Long Eyes

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optics

Background:

• Accurate intraocular lens (IOL) power calculation is crucial for achieving optimal refractive outcomes after cataract surgery.
• Axial length is a key biometric parameter influencing IOL power prediction accuracy.
• Previous studies have evaluated various IOL calculation formulas with varying results across different eye lengths.

Purpose of the Study:

• To identify the most accurate intraocular lens power prediction formulas for eyes with short axial lengths (<22 mm).
• To identify the most accurate intraocular lens power prediction formulas for eyes with long axial lengths (>26 mm).
• To provide evidence-based recommendations for formula selection in routine ophthalmic practice.

Main Methods:

• Systematic review and meta-analysis of studies published over the last 50 years.
• Inclusion of studies reporting outcomes of intraocular lens power calculation formulas.
• Stratification of analysis based on ocular axial length (short eyes and long eyes).

Main Results:

• For short eyes (<22 mm), the Haigis, Hoffer Q, and Holladay 2 formulas demonstrated the highest accuracy in intraocular lens power prediction.
• For long eyes (>26 mm), the Barrett Universal II, Haigis (with optimized constants), Olsen, and SRK/T formulas provided the most accurate outcomes.
• Formula performance varied significantly depending on the axial length category.

Conclusions:

• The selection of the appropriate intraocular lens calculation formula is critical and should be guided by the patient's axial length.
• Haigis formula shows consistent performance across different axial lengths, especially with optimized constants for long eyes.
• Ophthalmologists should consider these findings to optimize refractive outcomes in cataract surgery.