Role of Anterior Segment Optical Coherence Tomography in Evaluation of the Actual Depth versus the Planned Depth of Implanted Intrastromal Corneal Ring Segments in Treatment of Keratoconus

Abstract Background Keratoconus is a non-inflammatory, progressive and usually bilateral corneal disease characterized by progressive corneal stromal thinning and abnormal corneal steepening causing visual deterioration. ICRS implantation is a safe and reversible procedure that can be used in treatment of keratoconus. The correct position and depth of the ICRS after implantation are crucial to avoid post-operative complications and to improve visual outcomes. Objective To compare the actual depth of implanted ICRS with the planned depth using AS-OCT one week, one month and three months post-operatively for better predicting of the visual and refractive outcomes as well as to aid in prevention and early detection of post-operative complications in keratoconic patients undergoing ICRS implantation. Patients and Methods A prospective observational uncontrolled case-series study that was done on 10 eyes of 10 patients aiming to compare the actual depth of implanted ICRS (Kerarings) with the planned depth using AS-OCT which took place in Ain Shams University Specialized Hospital and Eye Subspecialty Hospital, Cairo, Egypt. Results All implanted ICRSs in all treated eyes showed shallower depth of implantation when compared to the planned depth in the follow up periods. Results have shown that the average measured depth of the ring segments in relation to the corneal thickness was found to be 65.7 % ± 1.7% (range= 63.1% – 68.1%) after 1 week, 67.6% ± 2.2% (range= 63.6% – 70.5%) after 1 month and 66.8% ± 2.2% (range= 63.8% – 70.6%) after 3 months. When comparing the actual depth of implantation to the thinnest pachymetry measured preoperatively, results have shown that the actual depth was found to be 64.6% ± 2.3% (range= 61.1% – 69.1%) after 1 week, 67.0% ± 4.3% (range= 60.8% – 74.9%) after 1 month and 65.3% ± 3.3% (range= 60.2% – 71.1%) after 3 months instead of the planned 80%. Conclusion ICRS are implanted at a shallower depth than intended. Stromal compression might have played a role in corneal stromal thinning above the implant and thus causing a false shallower depth of implantation. This can be further studied by implementing a confocal microscopy on larger sample sizes to be able to document actual anterior stromal collagen lamellae compression.