Case Reports

Molecular signature of unilateral corneal ectasia after small incision lenticule extraction (SMILE) in a normal corneal tomography

Case Report Details

First Author: G.Sachdev INDIA

Co Author(s):    S. Ramamurthy                    

Abstract Details

Purpose:

To present the pathogenesis of unilateral corneal ectasia following SMILE in a normal preoperative tomography. Iatrogenic corneal ectasia is a dreaded complication following refractive surgery. Limited cases of ectasia following SMILE have been reported in normal preoperative tomography. We describe the tear cytokine profile and epithelial genetic markers in a case of unilateral ectasia post SMILE

Setting:

Refractive Services of The Eye Foundation, Coimbatore, India.

Report of Case:

A 26 year old male patient presented to our refractive services with pre operative refractive spherical equivalent of -7.25D in right eye and -6D in left eye. Pentacam tomography was within normal limits with overall D in the white zone. The calculated residual stromal bed was 326u and 342u respectively. Patient underwent uneventful SMILE procedure and has 20/20 uncorrected vision post operatively. At 3 years post op, the patient presented with diminished vision in the right eye with refractive error of -2.5D sphere with -4D cylinder *110 with CSDVA of 20/80. Left eye maintained unaided vision of 20/20. Corneal tomography showed frank ectasia in right eye and was within normal limits in the right eye. The right eye subsequently underwent Intra Corneal Ring Segments with cross linking and CSDVA improved to 20/40. At the time of the procedure samples of the tears and epithelium from both eyes were taken and subject to molecular analysis. Lysyl oxidase (LOX) is a natural collagen crosslinking enzyme produced in the corneal extracellular matrix. LOX levels were reduced in both eyes with greater reduction in the ectatic eye. Matrix metalloproteinase levels were also elevated in the ectatic eye. Various other inflammatory markers including interleukins were tested and did not show any evidence of increase compared to controls.

Conclusion/Take Home Message:

This was a rare case of unilateral ectasia post SMILE surgery with completely normal preoperative tomography and only aberration in molecular signature detected from epithelium and tear samples. Reduced LOX and collagen levels may result in stromal weakening, and predispose normal corneas to ectasia post refractive surgery. No aberrant tear inflammatory profile was seen unlike in post LASIK ectasia Molecular signature of corneal tissue highlights a new dimension to the pathogenesis of corneal ectasia. Determining tear and epithelial LOX status may be a useful preoperative tool to determine incidence of post refractive ectasia.

Financial Disclosure:

None