J Korean Ophthalmol Soc JKOS Journal of the Korean Ophthalmological Society 0378-6471 2092-9374 The Korean Ophthalmological Society 10.3341/jkos.2012.53.12.1756 Original Article The Clinical Results of Intacs® Ring Implantation by Manual Tunnel Creation in Patients with Keratoconus Kim Eun Joo MD Koo Sung Hyun MD Lee Gwang Ja MD Lee Kyoo Won MD Park Young Jeung MD Cheil Eye Hospital, Daegu, Korea. Address reprint requests to Young Jeung Park, MD. Cheil Eye Hospital, #1 Ayang-ro, Dong-gu, Daegu 701-820, Korea. Tel: 82-53-959-1751, Fax: 82-53-959-1758, eyepark9@dreamwiz.com 12 2012 17 12 2012 53 12 1756 1765 26 03 2012 13 11 2012 Copyright © 2012 The Korean Ophthalmological Society 2012 Purpose

To report the clinical results after the implantation of intrastromal corneal ring segments (Intacs®) by manual tunnel creation for the correction of keratoconus.

 Methods

This retrospective case series was comprised of 10 eyes of 8 consecutive keratoconic patients. Visual acuity, refractive outcome, keratometric values, anterior chamber depth, central corneal thickness, and endothelial cell density were evaluated before and at 1 month, 3 months, and 6 months postoperatively. In addition, the implanted ring segment depth was measured by anterior segment optical coherence tomography at postoperative 6 months. Any postoperative complications were also recorded.

 Results

Visual acuity was improved in 9 out of 10 eyes. Spherical equivalent and keratometric values were decreased in all eyes. There was no significant difference in central corneal thickness, but endothelial cell density and anterior chamber depth were slightly decreased. The depth of ring segments was almost constant at superior, middle, and inferior. There was a single case of descented implanted ring segments and 6 cases of stromal infiltration around ring segments, but visual acuity was unaffected. In addition, 1 case showed implanted ring exposure, thus the superior ring segment was removed at postoperative 4 months.

 Conclusions

Intrastromal corneal ring segment implantation (Intacs®) by manual tunnel creation appears to be effective in improving the visual acuity and stabilizing corneal refractive power in keratoconic patients.

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Changes of the best corrected visual acuity (BCVA) after intacs implantation. In 9 out of 10 eyes (90%), the BCVA was improved at postoperative 6 months. A gain of 4 or more lines was seen in 6 eyes (60%).

Preoperative (left) and postoperative (right) mean keratometric maps of corneal topography 6 months after intacs implantation in case 1, 4, 5. The changes of maximal K are from 57.0 D to 50.0 D in case 1, 49.2 D to 44.6 D in case 4, 49.5 D to 46.4 D in case 5. There is the significant reduction in the K values.

Spectral-domain optical coherence tomography cross-section showing the intrastromal corneal ring segment depth at superior (top), middle (middle) and inferior (bottom) portion in case 2. The depth is almost constant.

Inferior descent of the implanted ring segments (arrow) occurred at postoperative 2 months in Case 1 but the visual acuity was not affected (A). The lamellar channel deposit in the inner surface of the ring segment (arrow) was observed in 6 cases, however did not influence visual outcomes in all of the cases (B).

In case 6, corneal melting was observed at postoperative 4 weeks at the site of knot removal followed by superior implanted ring segment exposure at postoperative 6 weeks (A). We removed the exposed superior ring segment at postoperative 4 months (B). Corneal epithelial defect healed 1 month after removal (C).

Nomogram for intacs ring size selection (Addition Technology, Inc, California, USA)

Characteristics of preoperative patients who underwent Intacs ring implantation

UCVA = uncorreted visual acuity; BCVA = best corrected visual acuity; SE = spherical equivalent; ACD = anterior chamber depth; CCT = central corneal thickness; A-K = Amsler-Krumeich keratoconus classification.

Preoperative and postoperative visual, refractive, and keratometric parameters

UCVA = uncorrected visual acuity; BCVA = best corrected visual acuity; Sim K's Astig. = simulated keratometric value's astigmatism.

*Wilcoxon signed rank test (preoperative-postoperative 6 months).

Preoperative and postoperative anterior chamber depth, endothelial cell density, and central corneal thickness in patients with intacs implantation

Values are presented as mean ± SD.

ACD = anterior chamber depth; CD = endothelial cell density; CCT = central corneal thickness.

*Wilcoxon signed rank test (preoperative-postoperative 6 months).

The mean intrastromal corneal ring segments depth (superior/middle/inferior) measured by Spectral-domain optical coherence tomography

Values are presented as mean ± SD.

*The depth was measured after removal of the exposed ring segment.