MERoV Study Results Preview
Short eyes, low myopia, and low spherical aberration show the formula for pseudoaccommodation following cataract surgery.
Published: Thursday, February 1, 2024
A combination of low myopic spherical equivalent, lower total eye spherical aberration, shorter preoperative axial length, and smaller pupil size increases the chance of achieving pseudoaccommodation with a monofocal intraocular lens (IOL), according to the findings of the ESCRS-funded Monofocal Extended Range of Vision (MERoV) study.
“Of the four factors we identified in our study, the only modifiable factor is the spherical aberration of the IOL, which can impact the total eye spherical aberration,” lead study author Mayank Nanavaty PhD told EuroTimes. “Therefore, if the patient has a shorter preoperative axial length and a smaller pupil size, then the surgeon can aim for a low myopic spherical equivalent and select an IOL with appropriate asphericity to reduce the total eye asphericity to almost zero.”
The prospective, non-blinded, non-randomised, single-eye cohort study sequentially recruited 412 patients, among whom 301 were available for follow-up at three to nine months. All underwent phacoemulsification and implantation of RayOne IOL (Rayner), a monofocal and aspherically neutral single-piece hydrophobic acrylic lens. The study’s inclusion criteria were uneventful cataract surgery with the postoperative potential for 20/40 (0.3 logMAR) uncorrected distance visual acuity (UCDVA) or better, no significant macular pathology, and willingness to participate in follow-up at three months.
The criteria for pseudoaccommodation were a UCDVA of 20/40 (0.3 logMAR) or better, measured with the ETDRS log-MAR chart at 4 m, and a near distance visual acuity (UCNVA) of J5 (0.3 logMAR) or better, measured using a Salzburg Reading Desk at 40 cm. All eyes underwent assessment of mesopic pupil size, keratometry, corneal topography, and wavefront aberrometry with the iTrace aberrometer (Tracey Technologies) and optical biometry with the IOLMaster (Zeiss) or, in those with very dense cataracts, A-scan ultrasound biometry (Accutome).
The study showed 29 patients (9.6%) achieved pseudoaccommodation, with a median UCDVA of 0.12 logMAR and a median UCNVA of 0.3 logMAR. Among those who did not, the median UCDVA was 0.14 logMAR, and median UCNVA was 0.5 logMAR.
Multivariate logistic regression modelling identified preoperative axial length, spherical equivalent, total eye spherical aberration, and mesopic pupil size as statistically significant factors influencing pseudoaccommodation. Comparing those with and without pseudoaccommodation, the respective median values were 23.4 mm and 23.7 mm for axial length, -0.39 D and 0.00 D for spherical equivalent, 0.018 mm and 0.022 μm for total eye spherical aberration, and 3.62 mm and 4.10 mm for mesopic pupil size. The study’s authors noted previous research has shown a correlation between smaller pupil size and reduced spherical aberration, leading to greater contrast sensitivity. Research has also shown that similar amounts of forward movement of an IOL in response to the eye’s natural accommodative reflex may lead to greater defocus in shorter eyes than in longer eyes.
The authors plan further research into accommodation involving different IOL types and may also investigate the effects of binocular summation and the influence of photopic pupil size and factors affecting reading comprehension.
The study has been accepted by the Journal for Cataract and Refractive Surgery and will be published in 2024.
Mayank Nanavaty MBBS, DO, FRCOphth, PhD is based at Sussex Eye Hospital, University Hospitals Sussex NHS Foundation Trust, Brighton, UK. email@example.com