Corneal thickness

 Hemlata Gupta MD

Using a refractive stromal lenticule offers a safe, effective and viable means of enhancing corneal thickness during corneal crosslinking (CXL) in patients with kerectasia and thin corneas, according to Hemlata Gupta MD.

“While longer follow-up is needed to ascertain progression of disease and possible scar formation, our study showed that myopic lenticule-assisted CXL seems to be a safe and effective technique to perform CXL in thin and ultra-thin corneas that would not otherwise be amenable to CXL,” she told delegates attending the XXXIII Congress of the ESCRS in Barcelona, Spain.

Dr Gupta, Centre for Sight, New Delhi, India, noted that while CXL is the only treatment modality currently available which halts disease progression in keratoconus, the standard Dresden protocol requires a corneal thickness of at least 400 microns after epithelial removal to safely crosslink the cornea.

“The problem is that many patients with advanced progressive ectasia often have thinner corneas, a situation which is not helped by the fact that referral of the disease is usually late in developing countries like India,” she said.

She explained that ReLEx (refractive lenticule extraction) and SMILE (small incision lenticule extraction) is a femtosecond laser technique which involves creation of a refractive lenticule with femtosecond laser (VisuMax, Carl Zeiss Meditec) and its removal through a small incision. Using this technique, a stromal lenticule is placed and spread over the host cornea following epithelial debridement, so the thickest area of the lenticule corresponds to the thinnest area of the cone. The remaining collagen crosslinking procedure is then carried out in a routine manner.

Dr Gupta’s study included seven patients affected by progressive kerectasia with thinnest pachymetry values ranging from 360 microns to 397 microns. The epithelium was debrided and a stromal lenticule 6.0mm in diameter and thickness of 110 to 120 microns was placed so that the centre of the lenticule corresponded to the apex of the cone. All patients underwent complete ophthalmological examination, including endothelial cell density measurements and Pentacam before CXL and at one, six and 12 months thereafter.

No intraoperative or postoperative complications were noted and best corrected visual acuity with contact lens fitting of 6/9 or more was achieved in all cases. Corneal stability was demonstrated on topography at 12 months follow-up and specular microscopy revealed no significant endothelial cell loss.

“This technique increases the corneal thickness in the most physiological way and seems to a safe, effective and viable alternative to enhance corneal thickness during CXL for these patients,”
she concluded.

Hemlata Gupta:
hemlatagupta@rediffmail.com