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Letter

Paradoxical central corneal steepening after collagen crosslinking in a case with intrastromal corneal ring segments

Abad, Juan Carlos MD

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Journal of Cataract & Refractive Surgery: October 2012 - Volume 38 - Issue 10 - p 1879-1880
doi: 10.1016/j.jcrs.2012.07.013
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We read with interest the article by Kiliç et al.1 about enhancing epithelium-off corneal collagen crosslinking (CXL) by injecting riboflavin into the intrastromal corneal ring segment (ICRS) channels when performing the 2 procedures simultaneously.

We would like to share one unusual experience that might relate to this type of practice. A 16-year-old man with a strong family history of keratoconus presented to our hospital with nonorthogonal with-the-rule astigmatism compatible with early keratoconus in both eyes. The preoperative data were uncorrected distance visual acuity (UDVA) of 20/50 in both eyes, and the refraction was +1.50 −3.50 × 13 = 20/30 and +1.50 −3.50 × 160 = 20/25. In October 2008, shortened arc (120 degrees) ICRS (7.0 Intacs, Addition Technology) were implanted in the left eye followed by a similar procedure in November of the same year in the right eye. The UDVA improved to 20/25 in both eyes, and the refraction became +0.25 −1.00 × 15 = 20/20 in the right eye and +1.00 −2.00 × 153 = 20/20 in the left eye. In March 2009, epithelium-off bilateral CXL with 0.1% riboflavin and 20% dextran was performed using a 3 mW/cm2 ultraviolet-A (UVA) device (Costruzione Strumenti Oftalmici) and a 8.0 mm spot for 30 minutes.

Two days later, the patient presented with loss of vision in the left eye. A white superficial haze that extended from the internal border of the nasal to the temporal ICRS was found. The epithelium closed uneventfully in both eyes, but no refractions could be obtained in the left eye during the first month. After 1 month, the UDVA was 20/25 in the right eye and 20/80 in the left eyere and the corrected distance visual acuity was +0.25 −2.50 × 14 = 20/20 and −3.50 −2.25 × 165 = 20/40, respectively. A circumferential haze was noted in the left eye; it had contraction marks that radiated from the ring segments (Figure 1) forming the equivalent of a dome of a cathedral (Figure 2, 1-year topography differential map), paradoxically increasing the central corneal curvature. The haze gradually decreased, and 2 years after the surgery the UDVA was 20/20 in the right eye and 20/40 in the left eye and the refraction was +0.75 −2.50 = 20/20 and −1.00 −6.00 × 17 = 20/30, respectively, with 1+ haze in the left eye.

F1-47
Figure 1:
Circumferential superficial contraction lines run from the inner part of the ICRS.
F2-47
Figure 2:
Bottom left: Curvature topography of the left eye after ICRS implantation but before the CXL procedure. Top left: Curvature topography of the left eye 1 year after the CXL procedure. Right: Difference map showing marked central corneal steepening in the area inside the ring segments.

The reason for this paradoxical response in the left eye of a bilateral case remains unclear, but one hypothesis is that the additional riboflavin that went into the ICRS channels enhanced the UVA-induced CXL to such an extent that it acted as a contraction ring steepening the central part of the cornea.A We are currently suturing the ring channels when performing simultaneous ICRS implantation and CXL to prevent the uneven distribution of riboflavin across the corneal stroma. The collagen fibers are arranged circumferentially in the corneal periphery,2,3 and any CXL preferentially involving this part of the cornea may lead to central steepening. In our case, these limbal fibers were isolated somewhat from the central cornea by the ICRS. Although this is an unusual case, it illustrates that asymmetric corneal contraction could lead to unwanted focal corneal effects.

REFERENCES

1. Kılıç A, Kamburoglu G, Akıncı A. Riboflavin injection into the corneal channel for combined collagen crosslinking and intrastromal corneal ring segment implantation. J Cataract Refract Surg. 2012;38:878-883.
2. Meek KM, Newton RH. Organization of collagen fibrils in the corneal stroma in relation to mechanical properties and surgical practice. J Refract Surg. 1999;15:695-699.
3. Meek KM, Boote C. The organization of collagen in the corneal stroma. Exp Eye Res. 2004;78:503-512.

OTHER CITED MATERIAL

A. Spoerl E, personal communication, August 2, 2010
© 2012 by Lippincott Williams & Wilkins, Inc.