Keratoconus is a progressive condition leading to abnormal bulging of the cornea with resultant increase in astigmatism and decreasing vision. Epithelium-off corneal collagen cross-linking is the only available method for arresting the progressive deterioration of keratoconus. Laser eye surgery by itself is not possible in people with keratoconus because laser surgery removes corneal tissue and thins the cornea, resulting in further weakening and potentially exacerbating the keratoconus. However, keratoconus is essentially a shape problem of the cornea and for some years Mr Angunawela has been using limited excimer laser surgery to remove the epithelium whilst reshaping the underlying bulge of the keratoconus at the time of collagen cross-linking. This typically gives patients better post-operative vision than cross-linking alone with both glasses and contact lenses . This laser treatment is called PTK (phototherapeutic keratectomy).
Recently published evidence in the journal Cornea shows significant improvement in overall vision with PTK laser surgery combined with corneal collagen crosslinking for keratoconus at 1 year after treatment. This evidence further supports this strategy over cross-linking alone (the full abstract of this article appears below). People considering cross-linking for keratoconus should discuss this option with their surgeon.
Mustafa Kapasi, Amanpreet Dhaliwal, George Mintsioulis, W Bruce Jackson, Kashif Baig
Cornea 2015 November 6
PURPOSE: To compare the long-term visual outcomes of patients with keratoconus treated with either phototherapeutic keratectomy (PTK) or mechanical epithelial removal before corneal collagen cross-linking (CXL) at 1, 3, 6, and 12 months postoperatively.
METHODS: CXL was performed by 1 of 3 surgeons (K.B., W.B.J., or G.M.). Seventeen eyes underwent mechanical epithelial removal before CXL and were consecutively selected after being matched with the 17 eyes in the PTK group for the variables of procedure date, average keratometry, and pachymetry. All cones were central. Manifest refraction spherical equivalent, sphere, cylinder, corrected distance visual acuity (CDVA), and pachymetry were measured and compared preoperatively and in follow-up.
RESULTS: The mean CDVA change in the PTK group at 12 months postoperatively was statistically different from the mean CDVA change in the mechanical group at 12 months postoperatively (P = 0.031). The PTK group had significantly better outcomes in visual acuity 12 months postoperatively than did the mechanical group (P > 0.05). The mean number of lines of improvement in the PTK and mechanical groups were 2.30 ± 0.96 and 0.00 ± 0.33 lines, respectively (P = 0.0036). The mean change between the preoperative and 12 months postoperative manifest refraction spherical equivalent for the PTK and mechanical groups were 0.78 ± 0.65 and 0.17 ± 0.65, respectively (P > 0.05).
CONCLUSIONS: PTK CXL resulted in better visual outcomes in comparison with mechanical epithelial removal CXL 1 year after treatment.