Big Advantages to Small-Aperture IOLs

A small-aperture intraocular lens (IOL) implanted in the non-dominant eye offers about 2.00 D additional depth of focus over a monofocal lens with image quality superior to other extended depth of focus and multifocal lenses, reported Elizabeth Yeu MD. Small-aperture lenses can also mask up to 1.50 D of corneal astigmatism and substantially improve vision in some patients with irregular corneas.

Dr Yeu reported on a prospective non-randomised open-label trial comparing 343 patients implanted with a monofocal lens targeting plano in the dominant eye and a small-aperture IC-8 lens (Bausch + Lomb) targeting -0.75 D in the non-dominant eye with 110 implanted with monofocals targeting plano in both eyes. At 12 months, mean monocular visual acuity was 20/32 at about -2.00 D defocus and 20/40 at -2.50 D in the IC-8 eyes compared with 20/40 at about -1.00 D in the monofocal eyes.

Binocularly, the two groups had comparable distance vision while the small-aperture group had superior intermediate and near vision, she said. Binocular contrast sensitivity was comparable with and without glare. Small-aperture patients also rated their severity of visual symptoms as very low or comparable to monofocal patients, with only about 3.0–3.6% of small-aperture patients reporting severe glare, halos, or starbursts.¹

Irregular corneas

Dr Yeu noted that implantation in the non-dominant eye is the label indication for the IC-8. However, small-aperture lenses can be used to treat some aberrated corneas due to irregular astigmatism, previous refractive surgery, or even keratoconus. “Where it really shines is in these irregular corneas.”

Research by Nicole Fram MD and others shows an improvement of about seven lines of uncorrected distance vision in patients with irregular astigmatism when implanted with a small-aperture lens. In some cases, it can mitigate corneal astigmatism and higher-order aberrations by blocking peripheral aberrations, improving vision quality.² Patients with worse uncorrected vision from aberrated corneas—from keratoconus or previous RK, for example—often experience a surprising level of satisfaction, Dr Yeu added.

Dilation beyond 6.5 mm can help minimise dimness and aid in Nd:YAG posterior capsulotomy, Dr Yeu said. If dimming is not an issue on the first eye, the IC-8 can be implanted bilaterally off-label for irregular cornea patients.

However, “not all irregular corneas can benefit from seeing through a small aperture,” Dr Yeu said. Preoperative tests can help. Raytracing can simulate small aperture performance over a 1.0–2.0 mm pupil, which can help determine if the lens will be useful. Range of vision of a small-aperture lens can be tested preoperatively with pilocarpine.

Patients with previous hyperopic LASIK may complain of vision quality issues, though those with previous myopic LASIK or prior monovision adaptation with contact lenses are generally happy. Glare may be worse when more than -1.25 D is targeted, so the goal should stay between -0.75 to -1.25 D, she concluded.

Dr Yeu made her comments at AAO 2024 in Chicago, US.

Elizabeth Yeu MD is an ophthalmologist in private practice and assistant professor at the Eastern Virginia Medical School in Norfolk, Virginia, US, and past president of the ASCRS. eyeulin@gmail.com

1. Vukich J, et al. JCRS, 50(11): 1165–1172, November 2024.

2. Fram N, “Clinical Outcomes of a Small Aperture IOL for Complex Corneas,” presented at ASCRS annual meeting 2024.