CXL plus PRK for keratoconus

[caption id="attachment_14408" align="alignleft" width="1024"] Mean anterior K1 flat (blue line) and K2 steep (purple line) and maximum keratometry (black line) as measured by the Scheimpflug device (Oculyzer II, WavLight AG, Erlangen, Germany) preoperatively up to 10 years postoperatively.
All units in keratometric dioptres (D)[/caption] The Athens Protocol for treating progressive keratoconus with partial topography-guided photorefractive keratectomy (PRK) and corneal cross-linking (CXL) appears to provide a safe and stable regularisation of corneal topography, said Anastasios John Kanellopoulos MD, New York University School of Medicine, New York, USA. At the 23rd ESCRS Winter Meeting in Athens Greece, Dr Kanellopoulos presented an observational case series of 144 eyes treated for progressive keratoconus with the Athens Protocol procedure. The study showed that mean uncorrected distance visual acuity, (UDVA) improved from 0.19 preoperatively to 0.53 at one-year postoperative follow-up, remaining stable at 10 years at 0.55. In addition, corrected distance visual acuity (CDVA) increased from 0.59 preoperatively to 0.8 at one year, remaining stable at 10 years at 0.81. Dr Kanellopoulos noted that 144 eyes showed no further keratoconic progression, although corneal topography showed progression in three eyes and was associated with persistent eye rubbing against medical advice and five eyes had a hyperopic shift during the 10-year follow-up. In terms of keratometry, mean K2 decreased from 50.57D preoperatively to 45.87D at one year postoperative (p<0.01), further flattening slightly but significantly more to 44.0D at 10 years (p<0.01). In addition, mean Kmax decreased from 53.43D to 46.17D (p<0.01), and also further decreased slightly but statistically significantly to 44.75D at 10 years (p<0.01). In addition, mean minimal corneal thickness decreased from 468.74 microns preoperatively to 391 microns at one year. However, by 10 years this had increased to 395.42 microns, most likely as a result of epithelial remodeling. TOPOGRAPHICALLY GUIDED ABLATION A CLOSER FIT TO CORNEAL OPTICS The Athens Protocol involves first performing a partial topographically-guided transepithelial photorefractive keratectomy (PRK), followed by a phototherapeutic keratectomy at a depth of maximum 50 microns, the application of mitomycin-C 0.02% for 30 seconds and then finally higher fluence corneal cross-linking at 6mW/cm² for 15 minutes. Clinical refraction can vary considerably from the eye’s topographic refraction, because many keratoconic patients learn to use their irregular topography to achieve a kind of pseudo-accommodative effect, Dr Kanellopoulos said. Dr Kanellopoulos emphasised that although some UDVA is commonly restored by the Athens protocol, the purpose of the procedure is to improve the corneal irregularity and thereby make the eye more amenable to correction with spectacles or contact lenses (CDVA). He noted that the progressive flattening seen in some eyes may be due to earlier techniques that used dextran riboflavin solutions rather than the hydroxypropyl methylcellulose (HPMC) formulations that are currently available. He added that he has recently adopted a new Athens protocol that incorporates customised CXL and reduces the ablation depth to 30 microns. Anastasios John Kanellopoulos: ajk@laservision.gr

Tags: corneal cross-linking (CXL), keratoconus, photorefractive keratectomy (PRK)