Minimal Invasive Topography Guided Photorefractive Keratectomy With Custom Cross Linking (Mitcx)

The objective of this study is to evaluate the efficacy, safety, and predictability of a new surgical intervention known as Minimal Invasive Topography-Guided Photorefractive Keratectomy with Custom Cross Linking (MITCX) in progressive keratoconus patients with contact lens intolerance (CLI). MITCX is a modification of simultaneous topography guided PRK with collagen cross linking technique to try to minimize tissue consumption, enlarge the treatment zone, and customize the CXL by using the epithelium as a shield.

MITCX was performed in a patient with progressive keratoconus reporting CLI, night vision problems and poor best distance visual acuity (BDVA) at Ebsaar Eye Surgery Centre, Dubai, United Arab Emirates.

To plan MITCX, the epithelial map (Zeiss OCT Cirrus 5000), 8 scheimpflug images (Wavelight ocullyzer II) and T-Cat profile were used (EX 500 Wavelight excimer laser platform from Alcon). The astigmatism and sphere magnitude were modified to achieve a hyperopic portion of the treatment profile (ablating 10 to 15 microns) and a myopic portion (ablating 30 to 40 microns) of the stroma after subtracting the thickness of the epithelium (optical zone: 6.0-6.50mm). The remaining epithelial sheet provided a shield to the stroma and customized the effect of CXL by using accelerated CXL 9mw/cm² for 10 minutes (peschke PXL-PLATINUM 330).

Pre-surgery, the patient had -1.50/-1.75@40 and corrected distance visual acuity (CDVA) of 0.4 Log MAR. Post-surgery (5 years) the patient had CDVA of 0.0 Log MAR with -2.50/ -1.50 @ 100, symptoms improved and topometric indices decreased. A 12.5 dioptres of regularization in the sagittal curvature of the front surface of the cornea were achieved with tissue consumption of 28- and 28-microns in the center of the pupil and the thinnest point of the cornea, respectively.

This technique minimizes tissue consumption, induces customization of the CXL, achieving better regularization effect vs tissue consumption, providing better surgery outcomes as it allows the epithelium to protect the flat areas next to the cone from receiving undesired laser. It is minimal invasive and allows treating larger optical zones and thinner corneas using a holistic approach of the cornea by respecting the important role of the epithelium.