Longitudinal ultrasound use associated with greater ocular surface fluid ingress

More transparent aqueous samples were seen after micro-coaxial phacoemulsification with torsional ultrasound, presenter says.

Ingress of ocular surface fluid into the anterior chamber occurred after micro-coaxial phacoemulsification with either torsional or longitudinal ultrasound, according to a study.

However, ingress was significantly greater after micro-coaxial phacoemulsification with longitudinal ultrasound than with torsional ultrasound, Vaishali Vasavada, MS, said at the European Society of Cataract and Refractive Surgeons meeting in Barcelona.

Dr. Vasavada and colleagues compared the amount of ocular surface ingress into the anterior chamber using trypan blue as a quantifying tracer agent. Eyes underwent micro-coaxial phacoemulsification with either torsional or longitudinal ultrasound.

“This gives us some kind of an indirect indication or hint of the different effects that these two technologies might have on the incision,” Dr. Vasavada said. “Further studies would be needed to validate these findings.”

In a previous randomized clinical trial, Dr. Vasavada and colleagues compared ocular surface ingress into the anterior chamber after phacoemulsification with a standard coaxial 2.8-mm incision or micro-coaxial 2.2-mm incision.

“In this study, we had found that there was, indeed, ingress of trypan at the end of surgery in all eyes,” Dr. Vasavada said. “However, when we compared the standard coaxial group with the micro-coaxial group, there was no statistically significant difference.”

In the more recent study, investigators aimed to compare micro-coaxial phacoemulsification with torsional ultrasound to micro-coaxial phacoemulsification with longitudinal energy, Dr. Vasavada said.

Investigators also set out to gauge results offered by the OZil torsional handpiece (Alcon).

“As we all understand very well, the OZil technology works on a side-to-side movement, but the longitudinal ultrasound moves on a forward-backward principle,” she said. “Logically, we thought that they might have some different effect in terms of the incision that we make.”

The OZil torsional handpiece offers cutting efficiency, thermal safety and reduced fluidics, according to an Alcon brochure.

Transparency of aqueous samples

The prospective, randomized, masked study included 80 eyes that underwent micro-coaxial phacoemulsification through a 2.2-mm single-plane incision. One group of 40 patients underwent phacoemulsification with torsional ultrasound. A second group of 40 patients underwent phacoemulsification with longitudinal ultrasound. All patients underwent removal of uncomplicated age-related cataracts.

Eyes with very dense cataracts and those with comorbidities such as shallow chamber, uveitis, glaucoma and myopia with axial length greater than 25 mm were excluded.

“Also, we made it a point to exclude all those eyes that had intraoperative complications, particularly incisional complications, such as wound-site thermal injury, incisional damage or the need to suture the incision,” Dr. Vasavada said.

One surgeon performed all cataract procedures on the Infiniti Vision System (Alcon).

“The surgical parameters were standardized as far as possible,” Dr. Vasavada said. “You will notice that the aspiration flow rate, the bottle height and the vacuum were standardized across groups as far as possible.”

After IOL implantation, all incisions, including the paracentesis, were hydrated. After removal of the speculum from the eye, 0.5 mL of 0.0125% sterile trypan blue was instilled on the ocular surface and held for 2 minutes. The ocular surface was rinsed thoroughly and 0.1 mL of aqueous was aspirated.

Investigators used a UV spectrophotometer to measure optical density, a visual indicator of the amount of trypan blue present in aqueous samples, Dr. Vasavada said.

Trypan blue was scanned at 190 nm to 900 nm; maximum optical density of the dye was 595 nm.

“Thereafter, a standard graph was created using different log dilutions of trypan blue,” Dr. Vasavada said. “This graph helped us to quantify the actual amount of trypan blue in each trypan sample.”

Study results showed that the torsional ultrasound group had a statistically significant higher log value, or lower ingress of trypan blue, than the longitudinal ultrasound group, Dr. Vasavada said.

“What this means here is that a higher log value indicates lesser ingress of trypan blue,” she said. “Or, put in simple terms, it means that with the OZil group, the aqueous samples were more optically transparent.” – by Matt Hasson

• Vaishali Vasavada, MS, can be reached at Iladevi Cataract and IOL Research Centre, Gurukul Road, Memnagar Ahmedabad 380 052, India; e-mail: icirc@abhayvasavada.com.