EyeWorld Asia-Pacific March 2019 Issue

53 March 2019 EWAP REFRACTIVE The effect of a lens placed inside the eye, however, has a different refractive effect that is more complicated to gauge. “When you have an implantable lens inside the eye, by contrast, it is like a myopic glass being shifted inside the eye near the focal point. You still have to consider the interface, therefore, typically patients who do well with glasses preoperatively are the ones who will do well with the implantable lens postoperatively,” he said. Refractive correction with phakic IOLs should be limited to cases with good glasses-corrected refraction, stable ectasia, and also to those who have repeatable and verifiable subjective refraction. Dr. Prakash personally prefers to have a perceivable, subjective improvement in excess of BSCVA (with glasses) 20/40 or UDVA to BSCVA with at least three lines of improvement. “Preoperatively, do not try to treat the autorefraction. We are trying to treat the subjective refraction in these patients,” he said. “A repeatable subjective refraction is the best guide. Also, keep the targeted postoperative refraction slightly myopic, as a hyperopic end result is usually poorly tolerated. Always inform the patient that reduced spectacle dependence is the target, not spectacle independence.” The IOL implantation is fairly straightforward, the only variation being a slightly larger incision at the limbus, he explained. The alignment marks are crucial. “We use slit lamp based markings, as they mimic the position in refraction,” he said. “Don’t overfill the chamber with viscoelastic and therefore avoid too much irrigation post-implantation. Postoperatively, be aware that a good guide for visual outcomes is the 1-month and 3-month refraction. Do not shy away from giving a temporary glasses correction if necessary. Redial only in cases of significant residual astigmatism; a small amount of astigmatism is not a problem. The stepwise planning for posterior chamber phakic IOL implantation in keratoconus needs patience and should include corneas that are stable and have subjective improvement with glasses. There should be no systemic or ocular contraindications to posterior chamber phakic IOLs,” he said. EWAP References 1. Antonios R, et al. Safety and visual outcome of Visian toric ICL implantation after corneal collagen crosslinking in keratoconus: up to 2 years of follow-up. J Ophthalmol. 2015:514834. 2. Dirani A, et al. Visian toric ICL implantation after intracorneal ring segments implantation and corneal collagen crosslinking in keratoconus. Eur J Ophthalmol. 2014;24:338–44. 3. Prakash G, et al. Evaluation of the robustness of current quantitative criteria for keratoconus progression and corneal crosslinking. J Refract Surg. 2016;32:465–72. Editors’ note: Dr. Prakash has no financial interests related to his comments. Contact information Prakash: drgauravprakash@gmail.com OCT image with ICL in situ in a keratoconic eye. Source (all): Gaurav Prakash, MD 9LHZV IURP $VLD 3DFLÀF Kimiya SHIMIZU, MD Sanno Eye Center 8-10-16 Akasaka, Minato-ku, Tokyo, 107-0052 Japan kimiyas@iuhw.ac.jp K eratoconic eyes have both high myopia and astigmatism, with irregular astigmatism also developing as the condition progresses, worsening visual function. Conventionally, wearing hard contact lenses (HCL) provides the best refractive correction, but some patients are unable to ZHDU +&/ GXH WR WKH LUUHJXODU VKDSH RI WKH FRUQHD DQG LW LV RIWHQ GLIÀFXOW WR achieve refractive correction in these patients. Keratorefractive surgery is contraindicated in patients with weak cornea in keratoconus, leaving phakic intraocular lenses (p-IOL) as the only option for refractive surgery. There have been numerous reports on the good clinical outcomes of the toric Implantable Collamer Lens (toric ICL, STAAR surgical, Monrovia, California) for keratoconus, and this option has good compatibility with keratoconic eyes for a number of reasons. First, the posterior corneal surface astigmatism reduces the total corneal astigmatism. Generally, anterior corneal surface astigmatism in keratoconic eyes is strong with-the-rule (WTR) astigmatism, but almost all posterior corneal surface astigmatisms are against-the-rule (ATR) astigmatism; hence, the total corneal astigmatism is offset by the anterior and posterior surfaces, which tends to reduce the amount of astigmatism. Therefore, as stated by Dr. Prakash, it is important to measure an accurate subjective refraction value to calculate the correct ICL diopter. Second, the original myopia in these cases is high, which means the cornea projects even further forward resulting in a deep anterior chamber; thus, surgery can be performed safely and easily. Third, this procedure is reversible. So, even if the keratoconus becomes more pronounced and the refraction changes, the lens can be exchanged. I have implanted toric ICLs into many keratoconic eyes till date, achieving a very high degree of satisfaction, as this procedure not only improves unaided vision but also eliminates eye discomfort. As Dr. Prakash says, selection of patients indicated for this procedure is important, but the surgical outcome should be favorable in patients with non-progressive condition and good corrected eyesight with glasses. The inclusion criteria for this surgical technique for treating keratoconus in Japan are as follows: a corrected distance visual acuity (CDVA) of 20/25 RU EHWWHU D FOHDU FHQWUDO FRUQHD DQ DQWHULRU FKDPEHU GHSWK • PP DJH • \HDUV DQG VWDEOH NHUDWRPHWU\ DQG UHIUDFWLRQ QR LQFUHDVH LQ FRUQHDO maximum keratometry [K2] greater than 1.0 D and no increase in cylinder greater than 0.5 D) for at least 1 year. 1 Combining this procedure with corneal crosslinking (CXL) is also considered effective for young patients whose condition may become progressive in the future. Reference 1. Kamiya K, et al. Three-year follow-up of posterior chamber toric phakic intraocular lens implantation for the correction of high myopic astigmatism in eyes with keratoconus. Br J Ophthalmol )HE (GLWRUV· QRWH 'U 6KLPL]X LV D FRQVXOWDQW IRU 67$$5 6XUJLFDO