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J Refract Surg. 2003 Nov-Dec;19(6):645-53.

Ferrara intrastromal corneal ring segments for severe keratoconus.

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  • 1Department of Ophthalmology, Federal University of São Paulo, Paulista School of Medicine, São Paulo, Brazil.



Intrastromal Ferrara ring segments were inserted in eyes with severe keratoconus to evaluate safety and efficacy of this procedure.


Intrastromal Ferrara ring segments were placed in 36 eyes of 35 patients with severe keratoconus, who were evaluated after 12 months of follow-up. All patients had highly disabling visual acuity, contact lens intolerance, and a previous indication for penetrating keratoplasty. Statistical analysis included preoperative and postoperative uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, anterior chamber depth, keratometry, and pachymetry.


No patient had a loss of visual acuity. Uncorrected visual acuity improved in 28 eyes (77.78%) and best spectacle-corrected visual acuity improved in 29 eyes (80.56%). Spherical equivalent refraction decreased from -7.29 +/- 3.12 D to -4.80 +/- 3.04 D at 12 months after Ferrara intrastromal ring segment implantation. Corneal topography and ultrasound biomicroscopy showed corneal flattening, demonstrated by thinning of the central cornea and a reduction in anterior chamber depth. Segment decentration occurred in one eye (2.7%), asymmetric positioning of the segments in two eyes (5%), inadequate depth in two eyes (5%), migration of the segments in two eyes (5%), segment extrusion in five eyes (13.8%), conjunctivitis in one eye (2.7%), bacterial keratitis in one eye (2.7%), and hydrops in one eye (2.7%).


With these early results, Ferrara intrastromal ring segments appear to be an alternative for the treatment of severe keratoconus.

[PubMed - indexed for MEDLINE]
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