Small-aperture IOL offers advantages over other presbyopia lenses

Reviewed by Burkhard Dick, MD

A new small-aperture intraocular lens (IOL) extends patients’ depth of focus as well as multifocal IOLs with fewer dysphotopsias, researchers say. 

In a prospective, open-label trial, the IC-8 (AcuFocus) improved patients’ uncorrected distance visual acuity (UCDVA) to 20/23, their uncorrected intermediate visual acuity (UCIVA) to 20/24 and their near visual acuity to 20/30 in the implanted eyes.

“The IC-8 IOL is a great lens that is highly versatile,” said Burkhard Dick, MD, chairman, University Eye Hospital Bochum, Germany, and principal investigator of a prospective, open-label trial of the lens published in the July 2017 issue of the Journal of Cataract & Refractive Surgery. 

“The pinhole only allows central focused light to reach the retina and blocks peripheral defocused light that degrades image quality,” Dr. Dick added. “This results in a high quality, extended depth of focus without blurry transition zones.”

Hydrophobic acrylic PC IOL

The IC-8 is a one-piece hydrophobic acrylic posterior chamber IOL with an optic that contains an embedded mask with a 1.36-mm central aperture. The dimensions of the mask and aperture contained within the optic are based on that of the Kamra corneal inlay (AcuFocus), with a smaller diameter and flatter radius of curvature to account for its more posterior placement within the eye.

The lens has a CE Mark and is available in some European and Asia Pacific markets. The company plans to start a U.S. clinical trial in 2018.

The small-aperture lens will compete with multi-focal and trifocal IOLs. These lenses provide good functional vision, but with the drawbacks of reduced contrast, visual disturbances and noncontinuous range of vision.

To test the small-aperture lens, Dr. Dick and his colleagues implanted it in 1 eye of 114 patients, while implanting the fellow eyes with a variety of aspheric monofocal IOLs.

Study results

Study results

At 6 months, 105 patients were available for follow-up. Their mean age was 67.5 years and 57.1% were women. The mean UCDVA in the eyes implanted with small aperture lens improved from 0.57 logMAR to 0.06 logMAR. Mean UCIVA improved from 0.66 logMAR to 0.08 logMAR. Mean uncorrected near visual acuity (UCNVA) improved from 0.75 logMAR to 0.18 logMAR.

By comparison, the UCDVA in the eyes implanted with the monofocal lenses improved from 0.61 logMAR to 0.03 logMAR. UCIVA in these eyes improved from 0.64 logMAR to 0.30 logMAR and UCNVA acuity improved from 0.71 logMAR to 0.51 logMAR.

Binocular UCDVA at 6 months was -0.056 logMAR, uncorrected intermediate vision was 0.043 logMAR and near vision was 0.160 logMAR.

By blocking peripheral defocused light rays, the small-aperture lens not only provides depth of focus, it reduces dysphotopsias, particularly for patients with aberrated corneas like post-refractive or keratoconic patients, Dr. Dick said.

Tolerance to astigmatism

It also provides tolerance to corneal astigmatism up to 1.50 D and a functional range of vision even if the refractive target is missed by as much as 1.00 D MRSE, he said.

“Thus, it would be inaccurate to say that there are zero complaints of glare or halo, but the incidence and severity seem to be by far much less than other multifocal IOLs based on my personal experience,” said Dr. Dick.

In the study, patients rated their visual symptoms on a scale of 0 to 5, where 0 was no symptoms, 1 was very mild and 5 was very severe. They rated blurry vision a mean of 1.09, fluctuating vision 1.0, dry eye 1.4, glare 1.4, halo 1.1, double vision 0.2, and ghost images 0.1.

The researchers performed mesopic contrast sensitivity testing in a subgroup of 36 patients. The eyes with the monofocal IOL had better contrast sensitivity than the eyes with the small-aperture IOL at 1.5 cycles per degree (cpd), 3.0 cpd, 6.0 cpd, and 12.0 cpd.

Binocular contrast sensitivity without glare in eyes with the small-aperture IOL was similar to that in eyes with the monofocal IOL at all spatial frequencies.

Eyes with the monofocal IOL had better monocular mesopic contrast sensitivity with glare than eyes with the small-aperture IOL eyes at 1.5 cpd, 3.0 cpd, and 6.0 cpd. At 12.0 cpd, the difference in contrast sensitivity between eyes with the small-aperture IOL and eyes with a monocular IOL was not statistically significant.

The 114 enrolled patients experienced 14 ocular adverse events: 9 in eyes with the small-aperture IOL and 5 in eyes with the monofocal IOL. The only serious adverse event was 1 case of persistent macular edema in an eye with the small-aperture IOL, but researchers did not consider it to be related to the device.

Overall high astigmatism

Overall high satisfaction

Overall 88.5% of patients said they were satisfied, 5.5% were neutral, and 5.8% were dissatisfied.

The small-aperture IOL appears to offer some advantages over other IOLs designed to correct for presbyopia, said Dr. Dick. With multifocal lenses, the patient has to interpret in-focus images on top of out-of-focus images as the various optical zones focus light to different focal points, he explained.

“As a result, these lenses can achieve good vision at specific foci, however with the determent of visual symptoms,” Dr. Dick said. “The IC-8 IOL, with its small aperture, provides a continuous extended depth of focus that doesn’t overlay in-focus and out-of-focus images.”

The small-aperture IOL also provides a complete range of vision than bifocal lenses, he said. “Compared to trifocal IOLs, the near focal point with the IC-8 IOL may not be quite as close, however the quality of vision with the IC-8 IOL is better,” he added.

In addition to cataract patients who do not want reading glasses, the lens is used for patients who have undergone refractive surgery, in challenging eyes like iris trauma and keratoconic patients, and in complex cataract cases to decrease dysphotopsias, said Dr. Dick. “The lens can truly benefit a broad spectrum of patients.”

Dr. Dick cautioned that it is contraindicated in patients with untreated ocular surface disease, macular diseases, or proliferative retinal disease.

Before surgery, he points out to patients that the lens is used monocularly and is paired with a high-quality, monofocal IOL in the fellow eye.

“If patients cover one eye and then the other to compare the different lenses, they may notice some differences in dimness between eyes,” Dr. Dick says. “Patients should be encouraged to not compare eyes as this will delay their natural adaption.” 

Researchers are now evaluating the lens’ potential for bilateral implantation, he said.

Burkhard Dick, MD

E: burkhard.dick@kk-bochum.de

Dr. Dick is a member of the AcuFocus medical advisory board. The study was supported by Acufocus.