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Ring segment adjustment or exchange leads to improved outcomes
Intracorneal ring segment adjustment or exchange can improve visual acuity and refraction in keratoconus eyes if satisfactory results are not achieved after primary implantation, according to a study.
A retrospective series of 26 eyes of 26 patients in whom no improvement of vision was achieved after implantation with two symmetrical Intacs (Addition Technology) were divided into two groups. The first group included eight eyes that underwent exchange with one Ferrara (Mediphacos) with a different arc length, mostly shorter. In the second group, 15 eyes underwent explantation of one segment and three eyes had the two segments exchanged with Intacs of a different arc length.
In all eyes, uncorrected and corrected distance visual acuity, refractive and topographic astigmatism, and higher-order aberrations improved with no complications.
According to the authors, this improvement was obtained because, rather than considering just the grade of ectasia, the type, position, depth and arc length of the segments were selected in the secondary procedures according to the phenotype of keratoconus, ie, the location of the ectasia and the relationship between the flattest topographic axis and the coma axis. A more accurate analysis of the ectasia morphology might be the key to obtain better visual and refractive results with intracorneal ring segments, they said.
“The results demonstrate that [intracorneal ring segment] surgery is reversible and adjustable in cases of patients with no improvement of visual or refractive parameters and has no intraoperative or postoperative complications,” the authors said. – by Michela Cimberle
Disclosures: The authors report no relevant financial disclosures.
Perspective
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When intracorneal rings are implanted and not efficient enough, removal and exchange remain a safe and effective option. Most of the time the exchange is from Intacs (Addition Technology) 6 mm or 7 mm to Ferrara or Keraring (both Mediphacos) 5 mm, and it is even possible with a manual, laser-free approach. Exchange from one ring to another with the same diameter is also feasible and beneficial if necessary. This study indeed confirms the good level of adjustability and reversibility of ICRSs for keratoconus.
ICRS exchange is, and must remain, a rare situation. Most of the time it comes as a consequence of an erroneous ring choice or inappropriate implantation. Nevertheless, ring exchange is still possible before considering laser enhancement or lamellar graft. Some recommendations could be underlined: Intacs (7 mm and 6 mm) should be proposed in peripheral patterns and not in paracentral or central patterns to avoid insufficient effect. A 5-mm ring usually offers more versatile choices to address different cases in central and paracentral keratoconus patterns; progressive asymmetrical rings are now available. Femtosecond laser implantation is more reliable for centration on the pupil as compared with mechanical channel dissection, which might lead to ineffective results due to inaccurate depth and channel positioning. Also, “on the table” adjustments, with the help of a keratoscope, under fixation target, speculum off, could be recommended to optimize ring positioning into the channels.
It would be interesting for the authors of this study to compare their results with those of additional topography-guided/CXL treatment on unsuccessful rings as an alternative to ring exchange, in cases with sufficient remaining tissue at the thinnest point (> 450 µm) and over the rings (> 200 µm). Another interesting comparison could be made with the results of deep lamellar keratoplasties after ring failure.