Phacoemulsification And Iol Insertion Outcomes In Nanophthalmic Eyes

Cataract surgery in short eyes is recognised to have greater complication rates and poorer and more unpredictable refractive outcomes. Although varying definitions exist, nanophthalmos is classically defined by an axial length (AL) <21mm and represents an eye ≥2 standard deviations shorter than the population mean. This study aims to evaluate the surgical and refractive outcomes of phacoemulsification and IOL insertion in nanophthalmic patients.

This data is derived from all patients undergoing phacoemulsification and IOL insertion at a Scottish centre from 2017 to 2023. This was a single-centre, multi-surgeon study, with cases performed by both consultant and trainee ophthalmologists.

Biometry data was exported for all patients, and cross referenced with surgical outcome data from an electronic patient record. Variables measured included standard biometric variables (AL, Anterior chamber depth (ACD) central corneal thickness, keratometry, lens thickness and white-to-white. Post-biometry variables included selected lens, target refraction, best corrected visual acuity (BCVA) and post-operative spherical equivalent (SE). SE error was calculated by the difference between surgeon target SE and actual SE. Using “R Studio” (Boston, MA), descriptive statistical analysis of these variables was performed, and associations explored with Spearman’s Rank test and multiple regression analysis.

157 eyes of 101 patients had an AL of <21mm, ranging from 18.75 to 20.98. 20 eyes were <20mm. Lenses inserted ranged from 18 to 36 dioptres.

The mean (±SD) BCVA at 6 weeks was 0.24 ±0.30. Mean post operative SE was -0.20 ±1.25 and mean post operative SE error was -0.178D ±1.10. Mean BCVA for the <20mm cohort was 0.19 ±0.21, SE -0.98 ±1.03 and SE error -0.90 ±1.14. There is a significant correlation between AL and SE error (r = -0.243, p <0.01), with decreasing AL associated with a greater SE error magnitude. Shorter eyes were associated with a more myopic refractive surprise, with multiple regression demonstrating significant relationship (p<0.001). 3.2% had a complication, the most frequent being wound burn and iris prolapse.

This data represents a large study of refractive outcomes in nanophthalmic eyes from a single centre. Despite the known complexity, BCVA outcomes remain good, as does the mean post-operative SE error.  Although higher than for routine phacoemulsification, complication rates remain acceptable. However, as shown by the large standard deviations, refractive outcomes were unpredictable, especially in more extreme axial lengths, with decreasing axial length associated with poorer refractive outcomes, and a more myopic SE error. We would recommend surgeons be mindful of this and adjust their refractive target when choosing a lens and refractive outcome for significantly short eyes.