This article is more than 5 years old. Information may no longer be current.
Improving efficiency and outcomes in phaco surgery
The improved fluidics profile associated with torsional phacoemulsification is a significant marker of improved surgical efficiency.
With traditional longitudinal ultrasound, cutting efficiency is improved if stroke length and duration are increased. Increased stroke length and duration, however, simultaneously increase the potential for added repulsion, chatter, turbulence, balanced salt solution usage and, therefore, possibly decreased surgical efficiency.
Improved efficiency, though, may be key to improving phaco efficacy. One measure of efficiency is reducing energy dissipated during phaco, which may mean reduced potential for damage to intraocular structures.
A study in 2001 by Cameron and colleagues showed that the presence of hydroxyl free radicals increased proportionally to the time of phaco surgery.1 The longer the surgeon stayed in the eye, and so long as aerobic solutions were used for infusion, the greater the risk of harmful hydroxyl radicals, according to the study.
Efficiency and efficacy
Phaco surgery should never be about completing the surgery as quickly as possible without regard to safety or outcomes, according to Robert P. Lehmann, MD, a clinical associate professor of ophthalmology at Baylor College of Medicine, Houston.
There is a delicate balance to be struck between duration of phaco surgery, the time the cutting tip is actually in the eye and ensuring a safe and efficacious surgery for the patient.
Dr. Lehmann, also of the Lehmann Eye Center in Nacogdoches, Texas, is a surgeon in private practice for 30 years and admits he is always willing to increase the procedural time of surgery in the interest of increased safety. Yet, he considers duration of surgery and measurements of tip-in-eye time to be important markers of both efficiency and efficacy.
When the surgeon has an opportunity to remove a cataract more efficiently without a drop-off in safety, it is beneficial to the patient, according to Dr. Lehmann.
“When surgeons move from traditional to torsional phaco, they will find they are doing surgeries more efficiently and with less tip-in-eye time,” Dr. Lehmann said. “However, they will not be doing so by compromising safety.”
Dr. Lehmann believes the OZil torsional handpiece is more advantageous for surgeons to use in both routine and complex cases. It is safer surgery, he said, because of the improved thermal safety profile and more constant contact with lens tissue that correlates with more efficient cutting because material stays at the torsional tip.
|
Dr. Lehmann, with the assistance of his daughter, Anna Lehmann, conducted a prospective, non-randomized evaluation of cataract surgeries to demonstrate the efficiency of surgery with this new technology in conjunction with the Infiniti Vision System (Alcon Laboratories, Inc., Fort Worth, Texas).2
He performed 81 phaco surgeries using torsional ultrasound and 73 with traditional, longitudinal ultrasound. Dr. Lehmann recorded total operative time and the time the tip was in the eye for emulsification. Infusion usage and day 1 postoperative appearance and unaided visual acuity were recorded and compared as further indicators of effectiveness.
In longitudinal phaco surgeries, Dr. Lehmann used a 1.1-mm flared Kelman tip, but a 0.9-mm Kelman tapered tip (both from Alcon Laboratories, Inc.) with torsional phaco. Because the inner diameters of the two phaco tips are different, the tapered tip is used with somewhat less vacuum.
Dr. Lehmann was also able to slightly lower the aspiration flow rate because of the lack of repulsion afforded by torsional movement. These changes resulted in more efficient surgeries while reducing overall balanced salt solution usage by 20%, Dr. Lehmann said during the presentation of his study at the American Society of Cataract and Refractive Surgery meeting.
Operating time was also shorter with torsional ultrasound. Torsional procedures were about 30 seconds shorter on average, and the total time that the tip was in the eye was 22% greater with standard longitudinal phaco. (Figure 1)
The design of Dr. Lehmann’s study is worth noting because more difficult cases – patients with pseudoexfoliation, floppy iris syndrome, those who dilated poorly, patients with glaucoma and very brunescent nuclei, with or without weak zonules – were selected for torsional procedures.
Although he originally intended to divide equally the number of patients receiving torsional or longitudinal phaco based on cataract density, Dr. Lehmann felt obligated to use torsional phaco for these more difficult cases when he observed them to be more easily managed with torsional phaco.
The smaller diameter torsional tip required “a little bit more work sculpting because it debulks less nuclear material within each grooving movement when compared to the larger 1.1 flared tip,” Dr. Lehmann said, “but, once the nucleus has been divided, the efficiency of side-to-side torsional movement, because of the resulting lack of repulsion or repelling forces, is just readily apparent.
“That lack of repulsion and the lowering of overall fluid usage is important, and I think that helps to explain a bit greater corneal clarity overall and unaided visual acuity among the torsional group,” Dr. Lehmann said.
“I am able to stay more at the level of or below the level of the iris plane in the central zone of safety, and the tissue is not repelled to the extent that it is with standard longitudinal phaco. There is less fluid flow through the eye and just increased efficiency,” he said.
Although the visual acuity results were not statistically different, Dr. Lehmann indicated he prefers the options afforded by the torsional technology. “I think there is enhanced tissue removal and enhanced safety. Corneal clarity postoperatively does seem better with torsional, especially in very dense or difficult cases,” said Dr. Lehmann.
| Comparison of surgical efficiency Figure 1. Overall surgical procedure time and in eye phaco time were reduced in Dr. Lehmann's study.2 |
Torsional for changing surgical environments
In the final statistical analysis, Dr. Lehmann compared results from traditionally more difficult cases performed with torsional ultrasound against cases considered standard in which patients were operated on with traditional, longitudinal ultrasound.
Nearly half the patients in the torsional group were “more difficult cases,” so there was not a comparison between equal groups, he said. There was subjective evidence to demonstrate that corneal clarity and postoperative visual acuity were improved with torsional ultrasound, according to Dr. Lehmann. More importantly, torsional phaco proved surgically efficient with an improved thermal safety profile.
Dr. Lehmann was not the only physician at the ASCRS meeting who presented data showing the statistical superiority of torsional phaco. Sonia H. Yoo, MD, associate professor of clinical ophthalmology at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, presented data showing that torsional phaco offers significant vision improvement postoperatively and requires far less balanced salt solution during surgery than traditional longitudinal phaco.3
|
Dr. Yoo reviewed 25 cataract extraction surgeries over a 4-month period, from November 2005 through February 2006. She used a 0.9-mm Kelman tapered phaco tip for most of the surgeries and entered through a single 2.6-mm clear corneal wound. Using torsional ultrasound, Dr. Yoo operated on a “full gamut of nuclear densities, with the vast majority being 2+ nuclear sclerotic cataracts.” Preoperative and postoperative vision, IOP, inflammation, endothelial cell counts and adverse events were noted. Intraoperative cataract grade, time of surgery, adverse events and balanced salt solution levels were recorded.
Total operation time averaged 17 minutes in the torsional study, Dr. Yoo said. An elderly patient with vitreous prolapse and a dense 4+ sclerotic cataract required the use of both traditional and torsional ultrasound, which prolonged operating room time to 45 minutes. The density of the nucleus along with the use of a 1.1-mm tip may have been factors that contributed to the vitreous prolapse, Dr. Yoo said.
On average, Dr. Yoo used 268 mL of balance salt solution per surgery, including the one difficult case that required about 500 mL. The one complicated case notwithstanding, the average amount was still “significantly less than what we use with conventional ultrasound,” said Dr. Yoo.
More than two thirds of patients achieved 20/30 vision, and 100% achieved 20/40 uncorrected visual acuity 30 days after torsional phaco surgery. By contrast, 83.3% achieved 20/20 vision, and 100% achieved 20/25 best-corrected visual acuity after torsional phaco. (Figure 2) Endothelial cell count loss was minimal in the study, Dr. Yoo said. The average endothelial cell count preoperatively was 2,790 cells/mm2, and at 1 month, decreased on average by 117, she said.
| Postoperative visual acuity Figure 2. Visual outcomes improved after torsional phaco.3 |
The effect of one difficult case may have skewed the results, Dr. Yoo said; however, it might exemplify why the results of the case series may more accurately reflect typical phaco surgeries: cataract surgery will not always be perfect – yet with improving technology, surgeons are capable of achieving good results, even in difficult cases, with a low incidence of adverse effects.
“Torsional ultrasound is a safe and effective method for cataract removal. Vision and cell counts are excellent when measured to other phaco modalities,” Dr. Yoo said.
References
- Cameron MD, Poyer JF, Aust SD. Identification of free radicals produced during phacoemulsification. J Cataract Refract Surg. 2001;27:463-470.
- Lehmann R. Outcomes and efficiency using torsional phacoemulsification versus traditional ultrasound. Presented at: Annual Meeting of the American Society of Cataract and Refractive Surgery; March 17-22, 2006; San Francisco.
- Yoo S. Conventional ultrasound versus torsional phacoemulsification. Presented at: Annual Meeting of the American Society of Cataract and Refractive Surgery; March 17-22, 2006; San Francisco.