Asymmetric keratoconus correction may improve visual acuity, refractive outcomes
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A progressive thickness intrastromal corneal ring segment may help improve visual acuity and refractive outcomes in patients with asymmetric keratoconus, according to a retrospective, observational, single-center clinical study.
One hundred four eyes of 82 patients were included in the study; 75 eyes were implanted with one Keraring AS (Mediphacos), and 29 eyes were implanted with two. The Keraring AS is not available in the United States.
The implantation procedure involved marking the horizontal axis with the patient sitting upright to control possible cyclotorsion and femtosecond laser creation of the intrastromal tunnel. The ICRS was placed in the tunnel with the thinnest end oriented nearest the incision and the center of the implant aligned on the flattest meridian.
At 3 months, mean uncorrected visual acuity was statistically significantly improved in all eyes, from 0.8 logMAR preoperatively to 0.44 logMAR in eyes with one asymmetric ICRS and from 0.89 logMAR to 0.53 logMAR in eyes with two ring segments (both P < .001). Mean best corrected visual acuity statistically significantly improved only in eyes implanted with one ring segment, from 0.3 logMAR to 0.18 logMAR (P < .001), whereas in eyes with two ring segments, mean BCVA improved from 0.34 logMAR to 0.29 logMAR.
Refractive measurements of manifest refraction spherical equivalent (MRSE) and cylinder were statistically significantly improved (P < .001) for one and two asymmetric ICRSs, respectively: MRSE –3.24 D to –1.94 D and –5.42 D to –1.83 D; cylinder –3.86 D to –2.00 D and –5.15 D to –2.03 D. Sphere statistically significantly improved in eyes with two asymmetric ICRSs, from –2.85 D to –0.82 D (P < .001). In eyes with one asymmetric ICRS, sphere improved from –1.31 D to –0.94 D (P = .034).
No complications were observed.
“The Keraring AS is an apparently safe and effective treatment for specific keratoconus phenotypes and keratectasia. The procedure is minimally invasive and reversible and yields good visual, refractive and keratometric outcomes,” the authors wrote. – by Erin T. Welsh
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Jack S. Parker, MD, PhD
In recent years, there has been an explosion of new technologies and techniques for the treatment of keratoconus of all severities, from mild to the very extreme. One old therapy that has benefited from a recent series of innovations is the intracorneal ring segment, and here, Prisant and colleagues describe their experience with implanting an ICRS of a new design, specifically, with segments that taper in thickness along their course to achieve a variable spacing effect, more tailed to the peculiar anatomy of the keratoconic cornea. These more refined, almost personalized, surgical interventions may very well be the future of keratoconic treatments, especially as our ability to image (and understand) the mechanical deficiencies of the keratoconic cornea improve. With regard to the ICRS, certainly these are safer interventions for the vast majority of patients and more appropriate than full-thickness corneal transplants, and we should be grateful for Prisant and collaborators for emphasizing the usefulness of this this general strategy and for investigating improvements and modifications to the technique, which will make this intervention even more popular and effective.
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