Intracorneal Ring Segments Implantation Outcomes Using Two Different Manufacturers' Nomograms for Keratoconus Surgery

Abstract

PURPOSE: To compare the outcomes of intracorneal ring segments (ICRS) implantation in keratoconic eyes with a similar tomographic pattern, using two different manufacturers' nomograms for surgical planning. METHODS: ICRS were implanted alternately in patients with the same tomographic pattern of keratoconus divided into two groups according to the surgical planning proposed by the ICRS manufacturers (Keraring, Mediphacos, Belo Horizonte, Brazil, and Ferrara Ring, AJL Ophthalmics, Vitoria, Spain). Visual, refractive, keratometric, corneal aberrometry, and optical quality changes were evaluated during a 6-month follow-up. Corneal and manifest refractive astigmatic changes were also analyzed using the double-angle polar plot and the Alpins vectorial method through the following components: target induced astigmatism, surgically induced astigmatism, difference vector, correction index, angle of error, index of success, flattening effect, and torque. RESULTS: After ICRS implantation, both groups showed significant improvement ( P < .05) in visual and keratometric data. Corneal aberrometric changes and optical quality improvement were also statistically significant in both groups, except for trefoil ( P > .05 in all intervals). The Alpins method analysis showed a better performance in the Keraring group, but with no statistically significant difference between groups ( P > .05). Comparison between groups showed a statistically significant difference only in tomographic astigmatism in double-angle polar plot analysis ( P = .03), with more significant improvement in the Keraring group. CONCLUSIONS: Both manufacturers' nomograms resulted in statistically significant improvement in most of the parameters analyzed, with greater correction of corneal tomographic astigmatism in the group operated on according to the spherical equivalent/tomographic astigmatism nomogram. [ J Refract Surg. 2019;35(10):673–683.]

Intrastromal corneal ring segments followed by PRK for postkeratoplasty high astigmatism: prospective study

“…In 2 studies regarding ICRS for keratoconus, these values were higher for CI and lower for IOS, indicating better outcomes than in postkeratoplasty eyes. 42,43 Nevertheless, our results improved after PRK, with mean CI significantly rising to 0.77 and 0.81, whereas the mean IOS decreased to 0.48 and 0.36 for corneal and refractive astigmatism, respectively.…”

The number of intracorneal ring segments in asymmetric and central cones

“…3 Change in corneal tomography pattern with single ring implantation in a patient with asymmetric cone although the nomogram recommended double ring implantation Fig. 4 Change in corneal tomography pattern with double ring implantation in a patient with central cone and improves CDVA [12]. Recent evidence suggests that normalization of the corneal asphericity [4] has a role in visual improvement.…”

A novel Q‐value‐based nomogram for single intracorneal ring segment implantation versus standard manufacturer's nomogram combined with accelerated cross‐linking for treatment of keratoconus: a randomized controlled trial

“…Recently, Rocha et al ( 2019 ) compared the Keraring and Ferrara ring nomograms, and concluded that the Keraring nomogram yielded better improvements in the topographic cylinder. However, our QN performed better in reducing the topographic cylinder than the SN, although the postoperative differences between both nomograms were not statistically significant (p = 0.29).…”

“…Intracorneal ring segment (ICRS) implantation flattens the central corneal curvature, thus reducing the refractive error and keratometry values, as well as improving visual outcomes (Kymionis et al 2014 ; Tian et al 2018 ; Iqbal et al 2019c ). Keraring segments (Mediphacos Inc., Belo Horizonte, Brazil), Ferrara ring segments (AJL Ophthalmic S.A., Vitoria‐Gasteiz, Spain) and INTACS ring segments (Addition Technology, Inc., Lombard, IL, USA) are widely used to correct refractive status in keratoconus patients, regularizing the anterior corneal surface to decrease both myopic and astigmatic components (Saleem 2015 ; Heikal et al 2017 ; Guyot et al 2019 ; Rocha et al 2019 ; Zaky et al 2020 ). The introduction of femtosecond laser surgery increased the popularity of ICRS implantation among cornea surgeons, as the procedure is simple, safe and accurate (Ibrahim et al 2016 ; Al‐Tuwairqi et al 2017 ; Park et al 2019 ).…”