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J Cataract Refract Surg. 2006 Nov;32(11):1860-5.

Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes.

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  • 1Doheny Eye Institute and Department of Ophthalmology, University of Southern California, Los Angeles, California, USA.



To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system.


Doheny Eye Institute, University of Southern California, Los Angeles, California, USA.


A prospective observational case series comprised 4 eyes of 4 patients receiving Intacs intrastromal corneal ring segments (Addition Technology, Inc.) for keratoconus. Optical coherence tomography (OCT) was performed between 7 days and 43 days after implantation.


The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements (r(2) = 0.68). The fractional implantation depth was correlated with several surgical variables using a stepwise multivariate regression model, and 2 statistically significant correlations were found. The position of the distal portions of the ring segments was shallower than that of the portion closer to the insertion site (P = .003). Segments placed in the inferior cornea (P = .008) experienced more distal shallowing. Shallower depth was associated with greater fractional anterior stromal compression (P = .04).


Shallower placement of intrastromal corneal ring segments may result in more complications, such as epithelial-stromal breakdown and extrusion, because of the greater anterior stromal tensile strain. The distal and inferior portions of intrastromal corneal ring segments tended to be placed at a shallower depth. Optical coherence tomography provided precise measurement of ring segment depth and may help identify implants that pose a greater risk for depth-related complications.

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