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Irregular corneal surface and blurred vision after LASIK elsewhere

A 35 year old lady presented after having had bilateral LASIK in November 2008, followed by right LASIK enhancement 1 year later. Apparently vision in the right eye had been blurred ever since the first LASIK procedure. She had been seen following that at another centre, and was advised to wear a rigid gas permeable contact lens.

During her first surgery, she underwent LASIK for

Right: -3.48/-0.59×159 with a VISX Waveprint Treatment

Subsequently she had an enhancement in this eye for apparent regression of -1.25/-0.50×180, but still had blurred vision after that.

On examination her unaided vision was 6/9-1 in the right eye. CDVA was 6/7.5 parts with Plano/-0.75×5. Intact, healed LASIK flaps were noted in both eyes. No evidence of flap scarring or striae was seen. Corneal topography with the Wavelight Topolyzer showed a localized area of corneal steepening nasal to fixation with marked flattening of the temporal cornea. This was not accompanied by any posterior corneal changes as shown by Wavelight Oculyzer measurements. Furthermore, anterior segment / corneal OCT showed a localized increase in corneal thickness in the area of increased steepness. This suggested that the cornea was not ectatic, and that the problem was an irregular ablation from the initial laser treatment.

She underwent a transepithelial, corneal wavefront guided PRK treatment on 30th March 2012. As the epithelium healed, vision in her right eye improved to 6/4.8 unaided. Manifest refraction was +0.25 in the right eye with vision of 6/4.8 one year after treatment.

Corneal Topography before surgery, but after LASIK elsewhereFigure 1 A patient presented with poor vision after prior LASIK due to an irregular cornea.

Optical Coherence Tomography showing uneven ablation with irregular corneal thickeningFigure 2 OCT confirmed this was due to an uneven ablation with irregular corneal thickening rather than ectasia.

Corneal Topography after wavefront guided transepithelial PRKFigure 3 After corneal wavefront guided transepithelial PRK, she gained unaided vision of 6/4.5 with much improved corneal topography.

Comments:

It is uncertain what exactly happened to this lady but it appears that the initial ablation resulted in an irregular stromal bed surface. The possibilities include a laser/computer malfunction, or markedly irregular bed hydration at the time of ablation.

The options include wearing a rigid gas permeable contact lens, or topography guided laser enhancement which could be performed on the surface via PRK or via a relift of the flap and re-ablation of the stromal bed. In this case, we decided to proceed with a transepithelial PRK.

The advantage of this type of procedure (laser epithelial removal) versus conventional PRK after scraping off the epithelium, is that the existing epithelium acts as a 'masking agent'. While by no means a perfect masking agent, in this case a very good result was obtained with much better corneal smoothness and very good unaided vision post-operatively.

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