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June 2003
IN THIS ISSUE

Corneal pachymetry proves key to glaucoma diagnosis

Probing physiology behind accommodative lens implants
Intralase cuts enhancement rates by 30% after LASIK
‘Quality of vision’ in sharp focus as four Main Symposia frame XXI ESCRS Congress
Allegretto laser works well for both hyperopia
and myopia correction, says FDA trial data
Innovative impulse device enables tongue to ‘see’ by processing sensory data to the brain
Increased precision of eye tracking module vital for customised ablations of large corneal areas
New adaptive optics system reduces higher order aberrations and previews custom ablation outcomes
High-resolution WASCA system shows good refractive outcomes for customised ablation
Results of prevalence studies casts link between ocular pressure and glaucoma in new light
New phakic IOL ‘gives good refractive outcome and is very well tolerated’, says specialist
Myopes are more likely to develop vitreoretinal complications than hyperopes after lens exchange
Preoperative myopia proves a good outcome predictor for LASIK surgery
Broad beam laser with Gaussian delivery obviates need for eye tracker in LASEK procedures
Modified approach needed for IOL power readings in post-RK eyes to cut risk of hyperopic outcome
Block excision therapy of choice for epithelial in-growth
CLAPIKS offers novel pharmacological approach for treatment the hyperopia after LASIK surgey
Study shows LASIK could provide long-term savings to patients despite initial costs
Theories take shape to unravel mystery of presbyopia development in the human eye
Retinal detachment risk in high myopes unaltered by excimer laser vision correction procedure
Ocular surgery patients advised to avoid risk of infection by staying away from swimming pools
Personalised iris prosthesis comes a shade closer to the ideal coloured iris solution
FEATURES
From The Editor
Guest Editorial
Reflections on Refractive Surgery
Bio-Ophthalmology
In Your Good Books
Bio-ophthalmology
Digital Opthalmologist
Regulatory Matters


High-resolution WASCA system shows good refractive outcomes for customised ablation

Dermot McGrath in Rome

THE latest version of Carl Zeiss Meditec’s wavefront aberration-supported corneal ablation system (WASCA) offers surgeons a valuable tool in the measurement and treatment of highly aberrated corneas, according to Dan Reinstein MD.

The higher resolution of the WASCA system, incorporating the latest CRS-Master software, allows more accurate wavefront measurements and consequently better refractive outcomes for customised ablation for patients with higher order aberrations, he told a session of 7th ESCRS Winter Surgery Refractive Meeting.

Dr Reinstein treated 15 eyes in 13 patients in a prospective study. All patients presented with serious post-LASIK or PRK optical disturbances such as chronic night vision problems, multiple or ghost image difficulties or, in one case, focusing strain disorder.

He first measured infrared scotopic pupil size. He then performed WASCA aberrometry to determine the ocular wavefront calculated for the scotopic pupil size. Patients underwent treatment with the MEL 70 excimer flying spot laser. Some patients were re-treated at three months by the same protocol if undercorrected

Dr Reinstein reported that of the 12 eyes which had BCVA of either 20/15 or 20/20 before surgery, none of them had a worse BCVA as a result of the re-treatment. Three eyes which were 20/25 BCVA before surgery improved to 20/15. Many of the treated eyes had shown an improvement for UCVA, which wasn’t surprising given the known effect of higher order aberrations on uncorrected visual acuity, he noted
Subjectively, 80% of the eyes achieved at least a 70% improvement. The procedure seemed to produce better results for multiple image problems.

"If we rank the patients by the type of complaint, it is clear that in terms of night vision disorders we had a very mixed success rate, but in terms of removing multiple images or ghost images, it seems to have been effective," Dr Reinstein said.
In relation to the wavefront data, he said the subjective metrics of success were generally noted to have been higher than would have been indicated by comparison on preoperative and postoperative wavefront data.

Nevertheless, he said that the treatment resulted in a statistically significant reduction in trefoil, which was encouraging. Less positive, however, was the result for quadrafoil, which found a statistically significant increase postoperatively. The outcome for spherical aberrations also fell somewhat short of expectations, Dr Reinstein said.
"We were disappointed that we didn’t get better results for the treatment of the wavefront aberration term Z4.0. This is the term we were hoping we could actually correct. There are millions of eyes out there with increased Z4.0 and we’d love to be able to treat that, but unfortunately we did not achieve a statistically significant change," he said.

The treatments were safe, with no eyes losing lines of acuity. Three eyes which experienced a reduction in BCVA subsequently recovered. The move to small spot lasers, better registration and better tracking should improve the ability to correct spherical aberration, providing even better refractive outcomes, he added.

"The CRS-Master is a work in progress and is not yet released on the market. The aim of this software is to provide surgeons for the first time with one software platform that will integrate patient clinical data with the type of data we would like to be able to use to treat patients. In other words, we now have dynamic access to both the wavefront and the surface shape data we need for accurate diagnosis and treatment," he said.

He explained that when all of this information was taken together rather than separately, it made it possible to optimise the ablation profile desired for a particular patient. Giving surgeons this level of control, as a final factor in the equation, should make it possible, with certain safety and tissue limitations, to fit compromises into the treatment which may be required for specific eyes.

Dan Z Reinstein MD
Reinstein Institute, London, UK
Email: dzr@ReinsteinInstitute.com

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