The evolution of refractive surgery

SAN DIEGO--In efforts to better understand the differences in refractive surgery and in an attempt to standardize the procedure on a worldwide basis, a survey was conducted by Kerry Solomon, MD, et al, and presented here at the American Society of Cataract and Refractive Surgery. The comprehensive investigation highlights demographics, practice patterns, surgical techniques, equipment used, preoperative, perioperative and postoperative procedures and complication rates. The survey was sent to the entire worldwide membership of the ASCRS (n=8196) in February 2001.

The response rate represents a global sampling. Based on Dr. Leaming’s response rate of his survey of 27% to 29% over the past five years, the 2001 survey had a response rate of 22% for North America, including Canada, Mexico and the United States. Looking at only the United States in this survey, the response rate more closely approximates that of Dr. Leaming's report (see "Practice styles and preferences of U.S. ASCRS members").

Have you had refractive surgery?

Of all the refractive surgeons that responded to the survey, 19% have had refractive surgery performed on themselves. According to the surveyors, this represents a higher percentage than the incidence of refractive surgery in the general population, perhaps demonstrating the confidence that today’s eye surgeons have with current techniques. The only continent in which no eye surgeon reported having the surgery was Australia/New Zealand. Thirty percent of African eye surgeons that responded to the survey have had refractive surgery performed on themselves; 20% for Europe; and less than 20% for North and South American eye surgeons.

For those respondents that didn’t have surgery, the major reason was because they exhibit no significant refractive error. Fewer than 20% of respondents either had concerns about side effects, or they didn’t know which eye surgeon should perform the procedure. Others claimed to be waiting for a better and safer procedure, or the costs of the procedure were too expensive or the respondents didn’t have the time to have the procedure.

Procedure volume

Fifty-seven percent of the eye surgeons who are waiting for a better procedure to be performed on themselves perform less than 5 refractive procedures per week. Twenty-nine percent perform 5 to 10; 11% perform 11 to 20 procedures per week. Only 3% perform more than 30 procedures per week. According to the investigators of the data, this figure demonstrates that those surgeons who are conservative with their eye care tend to be conservative with their refractive procedural volume. However, 11% would be classified as moderate volume and 3% would be considered high volume surgeons. This is lower than the percent of moderate and high volume surgeons.

For the other surgeons, 43% perform fewer than 5 procedures per week, 25% perform 5 to 10; 13% perform 11 to 20 procedures; 13% perform more than 30 and 6% perform 21 to 30 procedures per week. Surgeons that have had a refractive procedure performed on them tended to do more refractive procedures per week when compared with those doctors who have not had the procedure.

The most used laser for refractive procedures is from Visx, according to the survey. However, this number is biased, according to surveyors, due to the increased numbers of North American members of ASCRS. Almost 80% of North American respondents use a Visx laser. Forty-eight percent use the Hansatome from Bausch & Lomb. This number is also biased for the same aforementioned reason.

Comanagement compliance

As far as complying with the AAO/ASCRS comanagement guidelines, 45% of respondents claim they are following them. Thirty percent reportedly are not and 25% still do not know what the comanagement guidelines are.

According to survey results, refractive surgeons tend to comanage fewer than 25% of their patients regardless whether they follow the comanagement guidelines (89% of surgeons who follow the guidelines vs. 80% who do not). The surgeons who comanage more than 25% of their patients, however, are two to three times more likely not to follow comanagment guidelines, according to the survey. Interestingly, 1% of surgeons who follow the guidelines and 3% who do not follow the guidelines comanage 100% of their patients.

Price for LASIK

In terms of the different prices charged for LASIK, 40% of the North American respondents charge $1,500 to $1,999 per eye. Less than 30% of European refractive surgeons charge this amount. Less than 10% of South American surgeons charge this amount. There is some difference in prices around the world. This is due, in part, to differences in currencies and to a lower total number in responses from non-North American continents. Sixty percent of respondents believe prices will remain the same and plan to keep them the same for the next 6 months.

Practice patterns

While practice patterns for each continent appear alike in many aspects, there are a few variances, such as gloves are worn by all respondents from Australia/New Zealand and by the majority of the respondents from Europe and North America. Gloves are less commonly worn in South America, Asia and Africa, according to survey results. Surgical gowns are generally worn in all continents except in North America.

In terms of practice patterns in North America related to price, the survey found that surgeons that charge the highest price for LASIK less commonly use surgical gloves, scrub hat, or surgical scrubs.

Practice patterns among all other pricing levels appear to be similar with the exception of the increased use of sterile drapes for surgeons charging less than $500.

Surgical technique

According to survey results, both 8.5mm and 9.5mm rings are common for myopia. The larger 9.5mm ring size for myopia may be more frequently used due to the larger treatment zones offered by newer scanning lasers. For hyperopia, a 9.5mm ring is frequently preferred. Most or 51.5% of respondents plan for a central k reading of 45D to 47D.

The most common residual bed for LASIK for both primary and enhancement procedures is 250 to 274 microns of residual corneal tissue, according to the outcome of the survey. Five percent of surgeons are willing to go deeper than 250 microns for their planned primary procedure. Twice that many are willing to go deeper than 250 microns of residual corneal tissue for their planned enhancement procedures.

In terms of pupil size, 90% treat 8mm pupils or less, while 10% of surgeons would treat pupils larger than 8 mm.

Most surgeons are comfortable treating a potential patient with a pupil size of 1.5 mm or smaller compared to the ablative optical zone size. Several surgeons are comfortable treating pupil sizes of 2mm or larger than the optical zone size to be used. According to the surveyors, this difference may be due to the use of lasers that treat with wider blend zones or due to treating patients with lower degrees of myopia.

Bilateral surgery is performed more in Africa, Asia and North America versus areas such as Australia/New Zealand, Europe and South America.

Monovision accounts for less than 25% of patients treated worldwide. Monovision seems to be less common in Asia, Australia/New Zealand and Europe.

In terms of the corneal flap, drying times vary between less than one minute and up to 5 minutes. Most of the surgeons who responded to the survey first check flaps soon after the procedure rather than on the first postoperative day.

It is more common in Australia/New Zealand and Europe to change the blades between eyes. Most surgeons in Asia and North America change the blades between patients. It is more common in South America to change the blades after several patients have been treated.

Fluoroquinolones are the antibiotic of choice. The use of aminoglycosides and other antibiotics are more frequently used outside of North America. The use of anti-inflammatory agents appears alike between North America and other continents. However, strong steroids seem to be more frequently used after surgery in North America. Mild steroids and preserved non-steroidal agents appear to be more regularly used in other continents postoperatively. NSAIDs, preserved and nonpreserved, appear to be used more commonly perioperatively in North America whereas preserved NSAIDs are more commonly used postoperatively elsewhere.

Most refractive surgeons have not performed wavefront ablations, however, most suppose wavefront will increase the quality of vision. It is currently unclear if surgeons would be willing to convert back to PRK if wavefront PRK was found to be superior to wavefront LASIK.

Complications

The most frequently reported complication after LASIK is dry eyes, occurring 50% of the time or more often, after surgery. This was followed by glare, then striae. The distribution of complications appears similar for high volume surgeons compared to the total response of all refractive surgeons.

According to the survey results, surgeons believe there are many factors related to dry eyes, including previous dry eyes, final corneal curvature, depth of ablation, lid margin disease, hinge location, size of flap used and optical zone size. The most common factor reported was previous history of dry eyes, something that the majority of refractive surgeons are not measuring preoperatively. Most surgeons suppose that lid margin disease is also commonly related to dry eye.

Previous history of dry eye is the most common factor reported worldwide. Lid margin disease is the next most common reported factor worldwide. Surgeons in South America also believe final corneal curvature and other factors are associated more frequently.

Lid margin disease is the most commonly identified reported factor related to DLK worldwide. Microkeratome debris/oils, the autoclave, cleaning soaps for instruments and other factors including epithelial defects are also commonly reported. DLK appears to be multi-factorial, according to the survey.

Lens types

In Europe and South America, anterior chamber phakic IOLs are implanted more frequently than posterior chamber phakic IOLs. In North America, the numbers and styles in lenses are related to clinical studies. In looking at anterior chamber lenses only, foldable anterior chamber IOLs appear more common than fixed rigid anterior chamber IOLs, perhaps due to small incision size, the surveyors concluded. The iris-claw anterior chamber IOL is also common. In looking at posterior chamber phakic IOLs, the collamer lens is more commonly implanted versus the silicone lens.

Myopia is more frequently corrected with phakic IOLs as compared with hyperopia. Toric phakic IOLs are most common in Europe versus Africa, Asia and Australia/New Zealand.

Astigmatism

LASIK and astigmatic keratotomy are performed most to treat astigmatism. Toric IOLs are popular in Europe followed by North America.

The most common minimum anterior chamber depth is 3.2mm or less. However, some surgeons prefer a deeper anterior chamber.

Cell counts

Most prefer a minimum of 2000 to 2499 cells as the minimum endothelial cell count before anterior chamber phakic IOL implantation. This minimum is similar for posterior phakic IOLs. However, several surgeons do not measure endothelial cell counts prior to surgery.

Most prefer a minimum of 2000 to 2499 cells as the minimum endothelial cell count before anterior chamber phakic IOL implantation. Several surgeons do not measure endothelial cell counts prior to posterior chamber phakic IOL implantation.