More LASIK surgeons prefer wavefront-guided laser treatments
June 19, 2008
What's the best way to find out the latest trends in refractive surgery? Ask the doctors themselves.
At the 2008 Symposium and Congress of the American Society of Cataract and Refractive Surgery (ASCRS) held April 4-9 in Chicago, Richard Duffey, MD presented the results of the annual ASCRS refractive surgery survey that he co-authors. Surveys were mailed to nearly 4,800 ASCRS refractive surgeons and 628 responses were received, for a response rate of approximately 13%.
Among other findings, the survey shows a significantly higher percentage of refractive surgeons are recommending wavefront-guided laser treatments for the majority of their LASIK patients.
Wavefront-guided laser treatments, also called wavefront-assisted or custom ablations, are more precise than standard laser treatments. Instead of being determined by an eyeglasses prescription (like standard LASIK treatments), wavefront-guided ablations are much more detailed and are based on computerized measurements of thousands of data points on the cornea. These wavefront measurements create a detailed map of the refracting power of the eye.
Because of this higher degree of precision, wavefront-guided ablations can reduce optical imperfections called higher-order aberrations that standard laser treatments cannot address, and thereby may produce better visual outcomes after LASIK surgery.
Survey results: Wavefront-guided ablations preferred
Dr. Duffey reported that 52% of the refractive surgeons responding to this year's survey say they use wavefront-guided ablations for 76% to 100% of their patients. Last year, only 25% of the surgeons responding to the survey indicated they use the advanced ablations this frequently.
The change suggests there is growing acceptance among LASIK surgeons that wavefront-guided ablations provide better visual outcomes than conventional laser vision correction procedures.
Survey results: Other findings
The survey points out other trends as well.
In regard to ectasia – an infrequent but serious LASIK complication – there appears to be good news. The incidence of ectasia does not appear to be increasing and may actually be decreasing. In this year's survey, 17% of surgeons responding reported they have seen at least one patient with ectasia in their career – down from 30% the previous year.
Dr. Duffey suggests this decrease may be due to new surgeons being more selective when recommending laser vision correction and adopting more conservative clinical guidelines when evaluating corneal shape and thickness prior to surgery.
It's presumed that ectasia is caused by too much reduction of corneal thickness during surgery in eyes that may be predisposed to developing the problem. All other factors being equal, it appears that thicker corneas have less risk of ectasia after LASIK than thinner corneas.
A key factor appears to be the thickness of the cornea under the flap created in LASIK surgery – the part of the cornea referred to as the residual bed. Prior to surgery, the LASIK surgeon calculates the expected residual bed thickness after surgery. This calculation is based on the overall thickness of the cornea prior to surgery, the desired thickness of the corneal flap, and the amount of tissue that must be removed to correct the patient's refractive error.
Traditionally, most LASIK surgeons have tried to maintain a minimum corneal bed thickness of at least 250 microns after LASIK.
According to Dr. Duffy, this criterion of a "safe" residual bed thickness may be changing. In this year's survey, 17% of responding surgeons say they prefer using a calculated minimum residual bed thickness of at least 300 microns – up from 12% the previous year. And the percentage of surgeons who say they use the traditional calculated minimum residual bed thickness of 250 microns decreased to 57% – down from 61% the previous year.
Thinner LASIK flaps
To leave a thicker residual corneal bed after LASIK, an emerging trend among LASIK surgeons is the decision to create thinner corneal flaps.
Traditionally, corneal flaps created during LASIK have been 120 to 160 microns thick. (The average total corneal thickness of the human cornea is approximately 550 microns.)
According to this year's survey, the majority of responding surgeons (56%) now prefer making flaps that are 120 to 130 microns thick. And the percentage who prefer very thin flaps (100 microns or less) has increased to 20% – up from 10% two years ago.
Many surgeons have been patients themselves
Dr. Duffey notes that 30% of surgeons responding to this year's survey have had LASIK, PRK or some other type of refractive surgery performed on their own eyes – a percentage four times greater than that for the general population.
The willingness of so many eye surgeons to undergo LASIK and other laser vision correction procedures demonstrates their belief in the safety and effectiveness of the technology, says Dr. Duffey.