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Corneal Physician

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Employing the IC-8 in This Cataract Patient

Why was this IOL implanted in this 71-year-old patient, and how did he make out?

By: KAROLINNE MAIA ROCHA, MD, PHD, Marcela Feltrin De Barros, MD
Corneal Physician April 1, 2024 Vol 28, Issue April 2024 Page(s): 12-13

A 71-year-old male presented for a cataract evaluation of his left eye (OS). The patient had a history of radial keratotomy (RK), performed 30 years previous to the visit, as well as penetrating keratoplasty with Ahmed valve OD for corneal ectasia 8 years previous to the visit. On presentation, his best-corrected visual acuity was 20/60 OD and 20/50 OS with scleral contact lenses.

Slit lamp exam revealed a clear graft OD and 9 RK cuts with 6 arcuate keratotomy and +2 nuclear sclerosis OS. Corneal topography showed an irregular astigmatism and Scheimpflug tomography with aberrometry showing significant higher-order aberrations (HOAs), the left eye greater than the right eye (Figures 1 and 2). The patient elected to proceed with cataract surgery with an IC-8 Apthera IOL (Bausch + Lomb) (Figure 3). IOL calculation for the -0.75 target was planned.

Figure 1: Corneal topography showing irregular astigmatism.

Figure 2: Zernike analysis with significant HOAs.

Why the IC-8 Apthera IOL?
This is a one-piece acrylic UV-blocking extended-depth-of-focus hydrophobic posterior chamber IOL that has a 6 mm internal optical size and is 12.5 mm long. It contains a 1.36 mm central aperture surrounded by a non-diffractive 3.23 mm diameter opaque mask, called FilterRing. Additionally, the IOL’s power range is 10.0 D to 30.0 D. The IC-8 was chosen for this patient for two reasons:

1. HOA reduction. Patients who have irregular corneal astigmatism, like the one described above, experience HOAs that are responsible for difficulties with night vision, glare, halos, starburst patterns, or diplopia, and cannot be corrected by conventional IOLs. Additionally, total ocular aberrations are known to become worse as pupil diameter increases.

The small aperture of the IC-8 mimics a smaller pupil size and, therefore, reduces the impact of HOAs on visual acuity.1,2 Specifically, the pinhole effect of the IOL diminishes the effective pupil size, prompting a disruption of peripheral rays, while allowing central-focused light to reach the retina. This can improve visual acuity and quality. (Because its pinhole effect creates a significant contrast reduction, its use should be discouraged in patients who have any macular pathology, such as age-related macular degeneration, macular hole, edema, advanced glaucoma, or significant diabetic retinopathy.3)

Prior studies confirmed the reduction of HOAs with small aperture optics, resulting in improved optical performance.4,5 Moreover, the relationship between pupil size and depth of focus is well established, as Ogle et al found an inverse relationship between pupil size and the depth of focus. Small pupil size effectively enhances depth of focus.6,7 With the IC-8, patients can achieve roughly 2.5 D of continuous depth of field.

As a brief, yet important aside, despite the presence of the opaque mask, examination of the posterior segment is possible, although in non-mydriatic conditions. As the mask extends to 3.23 mm in total, the clear peripheral IOL doesn’t preclude visualization of the peripheral retina during fundus examination. Specifically, posterior segment investigations, including non-mydriatic fundus photography, OCT, and automated perimetry, could be performed in eyes that have small aperture IOLs.8

2. Toleration of residual refractive error. IOL power calculation is always a challenge in patients, like the patient described above, who have irregular astigmatism.9 The small aperture of the IC-8 can provide good uncorrected distance, intermediate, and near vision, while being more tolerant to sphero-cylindrical residual refractive errors, due to its extended depth of focus. In addition, induced astigmatic defocus up to 1.50 D may be reasonably compensated for with the IC-8 IOL.10 Consequently, improved tolerance to blur from residual-induced astigmatism can be achieved.

Figure 3: Intraoperative image of IC-8 IOL implanted in the capsular bag.

That Patient Today
At 3 months postoperatively, the patient’s uncorrected-distance visual acuity was 20/30, and his uncorrected-near visual acuity was 20/12. Refractive outcomes in IC-8 patients should be assessed subjectively, as autorefractors and retinoscopy are unreliable here. The IOL was centered, and postoperative manifest refraction was -1.25 DS. Currently, the recommended method for manifest refraction is “mid-point refraction,” which involves performing normal manifest refraction and then establishing the maximum plus lenses to blur and the maximum minus lenses to blur, and then calculating the mid-point.11 The patient said he was very happy with the results after achieving contact lens independence with a good quality of vision and
also improvement of his depth of focus. CP

Marcela Feltrin De Barros, MD

Marcela Feltrin De Barros, MD is a cornea, cataract, and refractive surgery postdoctoral research fellow at Storm Eye Institute, Charleston, South Carolina.  She has nothing to disclose.

KAROLINNE MAIA ROCHA, MD, PHD

KAROLINNE MAIA ROCHA, MD, PHD is the director of the Cornea & Refractive surgery division at the Medical University of South Carolina. Professor of Ophthalmology and Cornea & Refractive Surgery fellowship director at Storm Eye Institute, Medical University of South Carolina.

 

References

1. Franco F, Branchetti M, Vicchio L, et al. Implantation of a small aperture intraocular lens in eyes with irregular corneas and higher order aberrations. J Ophthalmic Vis Res. 2022;17(3):317-323. doi: 10.18502/jovr.v17i3.11568.

2. Langer J, Shajari M, Kreutzer T, Priglinger S, Mayer WJ, Mackert MJ. Predictability of refractive outcome of a small-aperture intraocular lens in eyes with irregular corneal astigmatism. J Refract Surg. 2021;37(5):312-317. doi: 10.3928/1081597X-20210222-03.

3. Dick HB, Piovella M, Vukich J, Vilupuru S, Lin L; Clinical Investigators. Prospective multicenter trial of a small-aperture intraocular lens in cataract surgery. J Cataract Refract Surg. 2017;43(7):956-968. doi: 10.1016/j.jcrs.2017.04.038.

4. Yuan Y, Shao Y, Tao A, et al. Ocular anterior segment biometry and high-order wavefront aberrations during accommodation. Invest Ophthalmol Vis Sci. 2013;54(10):7028-7037. doi: 10.1167/iovs.13-11893.

5. Muñoz G, Rohrweck S, Sakla HF, Altroudi W. Pinhole iris-fixated intraocular lens for dysphotopsia and photophobia. J Cataract Refract Surg. 2015;41(3):487-491. doi: 10.1016/j.jcrs.2015.02.001.

6. Ogle KN, Schwartz JT. Depth of focus of the human eye. J Opt Soc Am. 1959;49(3):273-280. doi: 10.1364/josa.49.000273.

7. Sánchez-González JM, Sánchez-González MC, De-Hita-Cantalejo C, Ballesteros-Sánchez A. Small aperture IC-8 extended-depth-of-focus intraocular lens in cataract surgery: a systematic review. J Clin Med. 2022;11(16):4654. doi: 10.3390/jcm11164654.

8. Srinivasan S, Khoo LW, Koshy Z. Posterior segment visualization in eyes with small-aperture intraocular lens. J Refract Surg. 2019;35(8):538–542. doi: 10.3928/1081597X-20190710-01.

9. Wang L, Spektor T, de Souza RG, Koch DD. Evaluation of total keratometry and its accuracy for intraocular lens power calculation in eyes after corneal refractive surgery. J Cataract Refract Surg. 2019;45(10):1416-1421. doi: 10.1016/j.jcrs.2019.05.020.

10. Ang RE. Small-aperture intraocular lens tolerance to induced astigmatism. Clin Ophthalmol. 2018;12:1659-1664. doi: 10.2147/OPTH.S172557.

11. Hooshmand J, Allen P, Huynh T, et al. Small aperture IC-8 intraocular lens in cataract patients: achieving extended depth of focus through small aperture optics. Eye (Lond). 2019;33(7):1096-1103. doi: 10.1038/s41433-019-0363-9.

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