Replacing Theories with Evidence Around the Axes of the Eye in Intraocular Lens Selection: A Review for the Clinician

The prevailing narrative in scientific literature has long overemphasized the role of ocular axes in intraocular lens (IOL) implantation, perpetuating misconceptions that have led to unnecessary exclusions of patients. Historical assumptions, coupled with inconsistent terminology and statistical inaccuracies, have muddled clinical decision-making. This review delves into these misconceptions, offering a critical reassessment of their relevance. Drawing from a non-systematic search across PubMed, the IOLEvidence App Database, and additional sources through snowballing, the review includes diverse studies exploring the relationship between ocular axes (angles, chords, kappa, alpha, lens, …) and IOL implantation. The findings reveal widespread confusion in terminology, particularly the interchangeable use of terms like 'angles' and 'chords', and highlight device-specific variability in parameters such as Chord-mu, Chord-alpha, and Chord-lens. Despite these inconsistencies, no robust evidence supports using these measures as grounds for excluding patients from IOL procedures. Interestingly, postoperative IOL centration (Chord-iol) emerged as a more critical factor for visual outcomes than preoperative ocular axes. The evidence suggests that values for Chord-mu, Chord-alpha, and Chord-lens should prompt further evaluation of atypical cases but are not reliable exclusion criteria. Moreover, a shift in focus toward aligning the IOL slightly temporal to the vertex normal appears to optimize visual acuity and minimize photic phenomena, challenging the established paradigm of knowledge about IOL centration.