International Ophthalmology Study Sheds Light on Myopia Biometry Ahead of Refractive Surgery

Key Takeaways

• The axial length–to–corneal radius (AL/CR) ratio demonstrated a linear relationship with spherical equivalent, supporting its value as a reliable biometric index in refractive assessment.

• Each 1-mm increase in axial length was associated with nearly a 2-diopter increase in myopia, reinforcing the central role of ocular elongation in disease severity.

• Comprehensive biometric evaluation—including corneal curvature and AL/CR ratio—may improve refractive surgery assessment and patient counseling across varying degrees of myopia.

A major international research article published in International Ophthalmology has provided new insights into the relationship between corneal shape, axial length, and the severity of myopia in patients before undergoing corneal refractive surgery. The study, titled “Corneal power, axial length–to–corneal radius ratio, and myopia status prior to corneal refractive surgery: a cross-study analysis,” analyzed biometric data from more than 1,200 myopic individuals.

The researchers included 1,208 patients with a median age of 22 and a median preoperative spherical equivalent (SE) of −4.88 diopters, reflecting a broad spectrum of myopia severity. Subjects were categorized into low, moderate, and severe myopia groups based on their SE measurements. A range of ocular biometrics was assessed, including corneal curvature, axial length (AL), anterior corneal astigmatism, central corneal thickness, and the axial-length-to-corneal-radius (AL/CR) ratio—a metric increasingly recognized for its relevance in refractive error evaluation.

Key Findings

• Corneal curvature metrics varied with myopia severity: those with severe myopia tended to have steeper corneal curvature along the steep axis compared with patients with lower degrees of myopia.

• AL/CR ratio emerged as a reliable index for evaluating refractive status, with a linear association observed between increasing AL/CR and decreasing SE. Each 0.1 unit increase in the AL/CR ratio corresponded with approximately a 1.48 diopter decrease in SE, highlighting its potential utility in clinical assessment.

• Axial length remained critically important, showing that each 1-mm increase in AL was associated with nearly a 2-diopter decrease in SE, underscoring the fundamental role of eye elongation in myopia progression.

• Gender differences were noted, with female patients exhibiting slightly shorter axial lengths, though the AL/CR ratio did not differ significantly between sexes in moderate and severe myopia, suggesting its robustness across groups.

Originally published online on Eyewire+.