Elsevier

Ophthalmology

Volume 107, Issue 12, December 2000, Pages 2144-2151
Ophthalmology

Confocal microscopy after implantation of intrastromal corneal ring segments

Presented in part at the Summer World Refractive Surgery Symposium of the International Society of Refractive Surgery (ISRS), Miami, Florida, July 1999.
https://doi.org/10.1016/S0161-6420(00)00387-0Get rights and content

Abstract

Objective

Confocal in vivo real-time microscopy was used to study the corneal morphologic features in eyes after Intrastromal Corneal Ring Segments (ICRS; now called KeraVision INTACS, KeraVision, Inc., Fremont, CA) implantation.

Design

Noncomparative, interventional case series.

Participants

The authors performed confocal real-time microscopy on a total of 21 eyes from 11 patients. Seventeen eyes from 10 patients (five female, five male; mean age 32.3 years; range 22–42 years) underwent uncomplicated ICRS surgery to correct myopia and were examined after surgery (average 8.6 months; range 2–15 months). Three patients had the ICRS implanted into only one eye, and those eyes were compared with the untreated fellow eyes. One eye of another patient was examined 1 and 6 months after ICRS removal.

Intervention

Flying slit-confocal microscopy was performed with water immersion objectives in the corneal center and near the nasal or temporal ICRS. Corneal optical sections were recorded in real time without further digital processing and were reviewed frame by frame.

Main outcome measures

Video frames selected from all corneal layers were evaluated qualitatively and quantitatively.

Results

In the central cornea, we found normal morphologic features at all layers. In peripheral sections, epithelial cells with highly reflective nuclei in the basal cell layer were observed in six of 17 eyes (35%) implanted with ICRS. We found an intact corneal nerve plexus and undisturbed corneal endothelium immediately underneath the ICRS. Around the ICRS, moderate fibrosis was seen. In one eye, linear structures in bamboo-like orientation were detected after ICRS removal in the last keratocyte layer underneath the collapsed tunnel.

Conclusions

Whereas the central corneal zone appears unchanged, the corneal stroma adjacent to the ICRS displays a slight, but distinct, activation of wound healing. Epithelial cells with highly reflective nuclei in this region may be an indicator for an increased biologic stress caused by the device.

Section snippets

Patients and methods

A total of 21 eyes of 11 patients were examined by confocal microscopy (Table 1). In 17 eyes of 10 patients (five male, five female; mean age 32.6 years; range 22–42 years) ICRS were implanted. The untreated fellow eyes of three patients with unilateral implantation served as controls. The mean elapsed time after ICRS implantation was 8.6 months, ranging from 2 to 15 months. The following ICRS thicknesses had been selected, depending on the patients preoperative myopia: 0.30 mm (2×), 0.35 mm

Baseline characteristics

Mean preoperative manifest refraction of the 17 eyes with ICRS was −3.47 sph +0.18 cyl 95° (Power Vector Analysis29), mean spherical equivalent of manifest refraction preoperative was −3.38 D, ranging from −2.0 to −4.75 D. The mean induced refractive change at the time of examination was 2.62 sph +0.4 cyl 83°. Preoperative UCVA was between 20/800 and 20/125. At the time of investigation, all eyes reached a UCVA of 20/32 or better, and 59% (10/17) saw 20/20 or better without correction. Best

Discussion

Because the cornea contributes most to the overall refractive power of the ocular optical system, almost all of the surgical procedures aim to correct low refractive errors by altering the anterior curvature of the cornea. Intrastromal Corneal Ring Segments, or INTACS, recently approved by the Food and Drug Administration, offer some distinct advantages when compared with other refractive procedures such as radial keratotomy, PRK, or LASIK: no surgical alteration at the central visual axis is

Acknowledgements

The authors thank Ao. Univ.-Prof. Mag. Dr. Alois Lametschwandtner from the Institute of Zoology, University of Salzburg, Austria for providing the scanning electron microscopy images of the explanted Intrastromal Corneal Ring Segments.

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    The authors have no financial interest in the products mentioned in this article.

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