Replacing intracorneal ring segments boosts visual outcomes in keratoconic eyes

Significant reductions in spherical and cylindrical refraction correlate with improved uncorrected vision.

Explantation of intracorneal ring segments and subsequent implantation of new segments markedly improved visual and refractive outcomes in eyes with keratoconus, a study showed.

Replacement of intracorneal ring segments (ICRS) also improved corneal keratometric and aberrometric outcomes, regardless of indication for explantation, the study authors said.

“A significant visual and refractive improvement can be achieved with the implantation of a new intracorneal ring segment combination after a previous unsuccessful implantation in keratoconus,” study authors Jorge L. Alió, MD, PhD, and David P. Piñero, MD, told Ocular Surgery News in an interview.

They said their study may have been the first to assess changes in corneal aberrometry resulting from ICRS explantation and implantation of new segment combinations.

The study was published in the Journal of Cataract and Refractive Surgery.

Indications and methods

The retrospective study included 21 eyes of 21 patients, with a mean age of 35.95 years. All eyes had an initial diagnosis of keratoconus and underwent ICRS implantation.

“We only included in our study patients with previous unsuccessful ICRS implants in which the segment had to be explanted,” Drs. Alió and Piñero said. “A new segment implantation in all these cases was planned with the aim of achieving a satisfactory visual outcome. Therefore, we defined a very specific inclusion criterion.”

Change after reimplantation in a case of ring segment extrusion. Images: Alió JL, Piñero DP

Change after reimplantation in a case of explantation due to a poor visual outcome.

Indications for explantation of initial ring segments were segment extrusion (seven eyes), poor visual outcomes (11 eyes), corneal neovascularization (two eyes) and severe visual disruption (one eye).

“Several factors caused the previous ICRS implantation to be unsuccessful: ring segment extrusion, corneal channel neovascularization, night vision disturbances with those ICRS requiring a diameter of implantation around 5 mm, and a very poor visual outcome, with and without spherocylindrical correction,” Drs. Alió and Piñero said.

No progressive corneal steepening, aberrometric increase or corneal thinning was identified after initial implantation in cases involving poor visual outcomes, corneal neovascularization and night vision disruption.

The median interval between initial ring segment implantation and explantation was 6 months (range: 1 month to 84 months).

Nine eyes received the same implant in both surgical procedures; six of those nine eyes received the Keraring (Mediphacos) and three received the Intacs ICRS (Addition Technology). Seven eyes initially received the Intacs ICRS and the Keraring in the subsequent procedure. Five eyes received the Keraring initially and the Intacs ICRS in the second surgery, the authors reported.

All eyes underwent complete ophthalmic examinations preoperatively, 1 month after initial ICRS implantation, before ICRS explantation, and 1 month and 6 months after implantation of a new ICRS.

No intraoperative complications were recorded. Faint channel haze occurred in some eyes but did not affect vision and appeared to diminish with time, the authors said.

Outcomes, observations

Study results showed statistically significant improvements in uncorrected distance visual acuity (P = .03) and manifest refraction (P = .04) 1 month after implantation of new ring segments, Drs. Alió and Piñero said.

Reduction of corneal sphere and cylinder correlated with marked improvement in uncorrected visual acuity, they said.

“In our cases series, a statistically significant reduction was found in spherical and cylindrical refraction after reimplantation,” Drs. Alió and Piñero said. “This refractive improvement was concordant with the significant improvement in uncorrected visual acuity also observed. Part of this improvement is due to the more efficacious control of corneal irregularity achieved with the new implant.”

Data showed a statistically significant difference in keratometry (P = .01) and a statistically significant improvement in corneal aberrometry (P = .03) from before surgery to 6 months after the second surgery, the authors reported.

The study showed no statistically significant differences in any visual, refractive, keratometric or aberrometric outcomes between eyes that underwent explantation for segment extrusion and those that had explantation because of poor visual outcomes, Drs. Alió and Piñero said.

“Similar visual, refractive and aberrometric evolution was observed in cases with ICRS explantation due to ring segment extrusion and due to poor visual outcomes,” they said.

Future study will focus on the role of corneal biomechanics in the performance of intracorneal ring segments, Drs. Alió and Piñero said.

“We think that the viscoplasticity of the cornea is the factor allowing the surgeon to remodel the cornea with a new ring segment combination instead of a previous unsuccessful implant,” they said. – by Matt Hasson

Reference:

• Alió JL, Piñero D, Sögütlü E, Kubaloglu A. Implantation of new intracorneal ring segments after segment explantation for unsuccessful outcomes in eyes with keratoconus. J Cataract Refract Surg. 2010;36(8):1303-1310.

• Jorge L. Alió, MD, PhD, and David P. Piñero, MD, can be reached at Instituto Oftalmológico de Alicante (Vissum), Avda. Denia (Edificio Vissum) s/n, 03016 Alicante, Spain; 34-902-333-344; fax: 34-965-160-468; e-mail: jlalio@vissum.com; dpinero@vissum.com.

I always enjoy reading publications by Dr. Alió and his group. In this study, there are several important take-home messages.

First, corneal rings can be safely removed and reimplanted with different sizes, thicknesses and combinations to improve the cornea.

Second, we need better metrics to describe what patients with keratoconus actually see in order to better measure vision distortions and quality of vision. For example, in this study there were largely trends of improvement (ie, not statistically significant), but the trends and significant changes in mean keratometry and root-mean-square and coma after exchange indicated improved vision. Commonly we’ll see patients be thrilled with improvement in their vision distortions, such as car tail lights being significantly constricted after Intacs (Addition Technology) or reduction of double vision and glare, but best corrected visual acuity may have changed merely one or two lines on the high-contrast acuity chart.

There is a disconnect between current vision metrics and patients’ experiences. More work is needed in this area to develop more sensitive measures of these types of distortions that go beyond measuring contrast sensitivity and aberrometry. Congratulations again to Dr. Alió and his superb research team.

– Brian S. Boxer Wachler, MD
Boxer Wachler Vision Institute, Los Angeles