FUNCTIONAL VISUAL RANGE OF PATIENTS IMPLANTED WITH ASPHERICAL MONOFOCAL INTRAOCULAR LENSES

Subjective evaluation of the visual outcomes of patients implanted with monofocal intraocular lenses (IOL) free of aberrations (enVista®, Bausch + Lomb Surgical), with emphasis on the defocus curve.

Spherical aberration is a high-order aberration with significant impact in the quality of vision, but it can help expand the depth of focus of the eye. The cornea has a positive spherical aberration, while the lens has a variable spherical aberration during life (negative during childhood, null around 40 years old, and positive later). Therefore, when the lens is removed, the eye remains with a positive spherical aberration which can be helpful in the extension of the depth of focus if an IOL that preserves this spherical aberration is implanted. This can be achieved with an aspherical IOL free of aberrations.

Prospective study with 58 eyes of 29 patients submitted to cataract surgery in 2021, implanted with the IOL enVista®. Inclusion criteria were no other ocular diseases, a potential visual acuity (VA) of at least 20/40 in the postoperative and less than 1D of preoperative corneal astigmatism. We collected data regarding their age, gender, preoperative VA, IOL selection, remaining postoperative spherical equivalent expected, real remaining postoperative spherical equivalent, postoperative best-corrected monocular VA, postoperative best-corrected binocular VA and the binocular defocus curve for each patient, from +1.5D to -4D.

From the 31 patients evaluated, 2 were excluded from the study (one due to posterior capsule opacification and the other due to an epiretinal membrane). The population had a mean age of 71 years old (ranging from 60 to 85 years old) and 66% of the patients were female. Preoperative best-corrected visual acuity was 0.34 logMAR. An average of 15 months had passed since the second eye surgery and the mean IOL power was 22D. The mean expected spherical equivalent was -0.3D and the real postoperative spherical equivalent was -0.1D. The binocular defocus curve showed a good visual acuity in the distances between infinity and 1 meter (0.19 logMAR or better) and a functional visual acuity up to 66 cm (0.39 logMAR or better). In the remaining intermediate vision, the visual acuity suffered a significant decline being 0.54 logMAR at 50 cm.

In this study we observed that patients had a good intermediate vision between 1 and 2 meters. Considering enVista® is a monofocal IOL, this slightly improved intermediate vision in binocular conditions (in order to simulate patients’ daily routines) can be attributed to the preservation of the natural positive spherical aberration of the eye with the implantation of this aspherical IOL.