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Can accelerated cross-linking halt keratoconic progression in ‘ultra-thin’ corneas?

Poster Details

First Author: H.Usmani UK

Co Author(s):    M. Friedman   D. Thompson   I. Rahman        

Abstract Details



Purpose:

To report the outcomes of a series of patients undergoing customised accelerated crosslinking using the Avedro System.

Setting:

Face and Eye Clinic, Manchester, United Kingdom

Methods:

Retrospective audit data was used to analyse a small subgroup of keratoconic eyes with corneal thickness below 400 microns undergoing accelerated crosslinking. All patients underwent pre crosslinking contact lens trial to ensure visual acuity of 6/12 or better could be achieved. All patients underwent epi-off crosslinking, with customised riboflavin soak time and UV dosage between 3.6-5.4 J/cm2. The amount of soak time was dependent on the amount of corneal thinning and varied between 10 minutes for a 323 micron cornea to as little as 5 minutes for a 271 micron cornea. All patients were examined using slit lamp biomicroscopy to ensure riboflavin diffusion throughout the cornea. Similarly, the thinner cornea underwent reduced UV exposure of 3.6J/cm2compare to the thicker corneas exposed to 5.4J/cm2. A standard 9mm alcohol assisted epithelium debridement was carried out under topical anaesthetic. No intraoperative pachymetry readings were taken. Patients were reviewed at day 3, 1,3,6 and 12 months, and contact lens fitting recommenced at 3 months.

Results:

Five eyes of 4 patients were identified who had undergone ultrathin corneal crosslinking. The mean age of the group was 21.6 (range: 19-25) years. The mean follow up period was 12.4 (range: 7-18 months). The preoperative BCVA was 6/12 or better in all patients. The mean apical thinning was 311microns (range: 339-271) prior to epithelium removal. Riboflavin soak time varied from 4 -10 minutes and UV exposure between 2-3 minutes at 30mW/cm2. Following cross linking 2 patients improved by 1 line of Snellen acuity or more. All patients achieved BCVA of 6/9 or better at last follow up. Similarly, the Kmax for all patients stabilised after 7 months to the pre-crosslinking level, with 1 eye showing 9 dioptres of flattening (reduction of Kmax from 98.2D to 86.5D) and another eye showing 5 dioptres of flattening (reduction of kmax from 69.1D to 64.7D). This stabilisation maintained for the mean follow up period. All patients were documented to have had improvement of contact lens comfort subjectively. No cases of corneal decompensation or other complications were noted.

Conclusions:

Collagen crosslinking has become standard treatment to prevent progression of keratoconus. However, caution is still used when dealing with those patients with ultrathin corneas, and potentially those in most need for stabilisation. This is often attributed to the fear of inducing corneal decompensation. However, although a small series, we have shown that customised riboflavin soak times and tailored UV exposure with the Avedro accelerated crosslinker, we are able to safely halt progression and prevent the need for corneal transplantation.

Financial Disclosure:

... is employed by a for-profit company with an interest in the subject of the presentation

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