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Intracorneal ring segment may reduce astigmatism after penetrating keratoplasty
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An intracorneal implant corrected residual astigmatism in eyes that had undergone penetrating keratoplasty, a study found.
“The postoperative astigmatism associated with penetrating keratoplasty is a common condition in clinical practice,” the study authors said. “The reason for this could be related to factors inherent to the receptor, such as previous corneal trauma or keratoconus. … When optical methods fail to achieve satisfactory visual rehabilitation, surgical treatment may be necessary.”
The retrospective analysis included 59 eyes of 54 patients with a mean age of 36.01 years who underwent PK and subsequent implantation of a Ferrara ring (Ferrara Ophthalmics) to correct residual corneal astigmatism.
LogMAR corrected distance visual acuity, keratometry values, spherical equivalent, spherical refractive error, corneal topographic astigmatism, minimum keratometry and maximum keratometry were evaluated during a mean follow-up period of 14 months.
Study results showed that mean corrected distance visual acuity improved from 0.45 preoperatively to 0.30. No patients lost visual acuity; 28 patients gained at least two lines of corrected distance visual acuity.
Mean spherical equivalent improved from –6.34 D preoperatively to –2.66 D postoperatively. Mean spherical refractive error decreased from –7.10 D to –3.46 D.
Mean corneal topographic astigmatism decreased from 3.37 D to 1.69 D.
The mean maximum keratometry value diminished from 48.90 D to 44.17 D; the mean minimum keratometry value decreased from 44.90 D to 42.46 D.
Improvements in corrected distance visual acuity, spherical equivalent and refractive error were statistically significant (P < .0001), the authors said.
Perspective
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David R. Hardten, MD
Coscarelli and co-authors describe a novel use of Ferrara rings to reduce myopia and astigmatism after penetrating keratoplasty. They achieved on average 1.7 D of astigmatic reduction and almost 4 D of corneal flattening using the segments. Unfortunately, 5% of the eyes had dehiscence of the graft-host junction with the dissection, although they used mechanical dissection, and for the most part, femtosecond laser is now available to create the channels for intracorneal rings. Ferrara rings are likely uniquely suited for use after keratoplasty, as they are placed at a 5-mm optical zone. Intacs (Addition Technology), have an outer diameter that would likely be too close to the graft-host junction to be useful in this setting. Unfortunately, Ferrara rings are not approved in the U.S. It will be interesting to see if the authors have better results with femtosecond laser channel creation in the future. This paper adds an innovative new method to handle the frustrating problem of post-keratoplasty astigmatism and anisometropia.
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J Cataract Refract Surg. 2012;38(6):1006-1013.
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