Issue: March 2012
January 31, 2012
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Corneal collagen cross-linking may yield insufficient astigmatic correction


Eur J Ophthalmol. 2011. doi:10.5301/ejo.5000063.

Issue: March 2012
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Biomechanical changes induced by corneal collagen cross-linking in keratoconic corneas correlated with insignificant astigmatic correction, according to a study.

"Cross-linking is able to induce a corneal astigmatic change, but it is variable, not predictable, and insufficient to provide an effective astigmatic correction," the study authors said.

The retrospective study included 16 eyes of 12 patients with mild to moderate keratoconus that underwent corneal cross-linking with riboflavin and ultraviolet radiation. Mean patient age was 32.58 years.

All 16 eyes had previously undergone implantation of intracorneal ring segments. Cross-linking was indicated in all cases because of ectatic progression.

Investigators evaluated visual outcomes, refraction, keratometry, corneal aberrometry and corneal biomechanical changes up to 24 months postoperatively. The Alpins method of vector analysis was used to evaluate magnitude of error, angle of error, flattening effect and torque, and the amount of astigmatic change resulting from surgery.

Study results showed statistically insignificant changes in refraction, central keratometry and corneal higher-order aberrations.

Differences between targeted and surgically induced astigmatism were significant at 3 months (P < .01) and 6 months (P = .01).

"Therefore, the corneal astigmatism was not completely corrected after [cross-linking]," the authors said. "In an ideal complete correction, [surgically induced astigmatism] and [targeted induced astigmatism] would be identical."

Further study with a larger patient sample is warranted, they said.