Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes
Accepted 7 May 2006.
Purpose
To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system.
Setting
Doheny Eye Institute, University of Southern California, Los Angeles, California, USA.
Methods
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.
Results
The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements (r2 = 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).
Conclusions
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.
From the Doheny Eye Institute and Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
Corresponding author: David Huang, MD, PhD, Doheny Eye Institute, 1450 San Pablo Street, DEI 5702, Los Angeles, California 90033, USA.
Drs. Huang and Tang receive grant support from Carl Zeiss Meditec, Inc. Dr. Huang receives patent royalties related to optical coherence tomography technology. No other author has a financial or proprietary interest in any material or method mentioned.
Supported by grants from Carl Zeiss Meditec, Inc., NIH (P30 EY03040 and R24 EY13015-01), and Research to Prevent Blindness, Inc.
ABSTRACT