25-gauge vitrectomy shows more comfort, technical problems in study

There was less conjunctival injection and postop pain compared with 20-gauge vitrectomy, but tool flexibility and size posed difficulties.

ByJared Schultz

Vitrectomy with a 25-gauge system improves patient comfort more than a 20-gauge system, but there are difficulties with retinal manipulation and illumination, according to a study.

Susanne Binder, MD, and colleagues at the Ludwig Boltzmann Institute for Retinology and Biomicroscopic Laser Surgery in Vienna, Austria compared 20-gauge vitrectomy with 25-gauge to gain a clearer picture of the pros and cons of the two systems than previous studies have offered.

“Although single advantages and disadvantages have been reported in case series, precise evaluation in a prospective randomized clinical trial is missing,” they wrote in the British Journal of Ophthalmology.

Points of comparison

The study was a randomized, prospective, controlled clinical trial that included 60 patients with preretinal membrane, posterior uveitis, uncomplicated vitreous hemorrhage, synchisis scintillans, macular edema or macular hole.

The study did not include cases that required silicone oil tamponade or that had previous vitrectomy or operations of the retina.

The patients were split into two groups of 30 and randomly assigned to either the 20-gauge or the 25-gauge system to remove at least 80% of the vitreous, according to the study.

Patients were examined the day before surgery, at 1, 2 and 3 days postoperative and at 1 and 3 months postop, the authors said.

Researchers collected data on patient age, gender and duration of surgery, which was divided into duration of wound opening, vitrectomy, retinal manipulation and wound closure.

They also evaluated subjective postop pain, conjunctival injection, IOP, visual acuity, retinal situation, as well as intra- and postop complications, surgeons’ judgments of tools and technical difficulties, according to the study.

In order to measure the duration of the surgeries, the researchers used a stopwatch from the beginning of the first conjunctival cut and evaluated the time needed for conjunctival and scleral preparation, vitrectomy, withdrawal of the cannulas, and closing and suturing of sclerotomies and conjunctiva.

“The time advantage gained by the use of the sutureless technique could imaginably be lost by the need for a longer vitrectomy time or longer retinal manipulation time in order to remove the same amount of vitreous through the smaller caliber of the instrument or difficulties of grasping with finer forceps,” the study authors said.

Improved patient comfort

Wound opening and wound closing were significantly shorter in duration with the 25-gauge system than the 20-gauge system, according to the results (P < .001). Opening time was 306 seconds with 20-gauge and 173 seconds with 25-gauge. Closing time was 357 seconds with 20-gauge and 112 seconds with 25-gauge.

The duration of the vitrectomy itself was significantly longer in the 25-gauge system than in the 20-gauge system, 774 seconds vs. 490 seconds (P < .001), but the total length of surgery did not differ significantly between the two groups, the authors said.

Both groups experienced significant improvement from baseline in visual distance and reading acuity 3 months after surgery, according to the study.

Mean baseline IOPs were 14 mm Hg in both groups. During the first 2 postop days, IOP in the 25-gauge group dropped to less than 10 mm Hg in nine patients compared with two patients in the 20-gauge group, but none were less than 6 mm Hg, the results showed.

The maximum difference in IOP from baseline during the first 2 postop days was significantly smaller in the 25-gauge group compared with the 20-gauge group, but by the third day the difference was no longer significant.

Conjunctival injection and subjective postop pain was significantly lower (P < .001) in the 25-gauge group compared with the 20-gauge group, the results showed.

“The important factor turned out to be a clearly higher patient comfort with the 25-gauge system,” the authors said.

Technical difficulties

In the 25-gauge surgery, the surgeon shifted the conjunctiva sideward in order to insert the trocars through the conjunctiva and the sclera. After vitrectomy, the surgeon removed the trocars and covered the sclerotomies with the conjunctiva, according to the study.

In the 20-gauge surgery, the surgeon opened the conjunctiva in a nasal triangle and a temporal quadrangle 1 mm from the limbus before performing the scleral incisions. After vitrectomy, the surgeon used 7-0 Vicryl sutures to close the sclerotomies and conjunctiva.

Both systems had comparable cutting rates of 1,200 to 1,500 cuts per minute, but because of its smaller diameter, the 25-gauge required a higher suction rate of 400 mL to 500 mL per minute compared with 150 mL to 200 mL per minute in the 20-gauge, according to the study.

Consequently, 11 out of 30 patients in the 25-gauge group experienced at least one technical difficulty during surgery, the authors said.

Some of the difficulties included the vitreous cutter and endo-instruments were unable to dissect tight vitreous or epiretinal membranes; the light source could not provide enough illumination; the trocars became blocked and were replaced; and the suction was not strong enough to remove intraocular blood.

Flexibility of the 25-gauge instruments also posed some problems, as the surgeons were not able to adequately peel the epiretinal membrane or rotate the globe in three cases, the authors said.

“Although the learning curve for the 25-[gauge] sutureless vitrectomy must be considered, higher flexibility and lesser mechanical stability can lead to a limitation for surgical indications and increased costs when an additional 20-gauge vitreous surgery system has to be provided.

“Further study as well as technical development will be needed to improve the principle of sutureless transconjunctival pars plana vitrectomy and to minimize the intraoperative handicaps as well as potential postoperative risks,” they said.

For more information:

Susanne Binder, MD, the corresponding author of this study, can be reached at Department of Ophthalmology, Ludwig Boltzmann Institute for Retinology and Biomicroscopic Laser Surgery, Rudolph Foundation Clinic, Juchgasse 25, 1030 Vienna, Austria; +43-1-71165-4607; fax: +43-1-71165-4609; e-mail: susanne.binder@wienkav.at. She has no financial interest in any of the subjects mentioned in this article.

Reference:

Kellner L, Wimpissinger B, et al. 25 gauge versus 20 gauge system for pars plana vitrectomy: a prospective randomized clinical trial. Br J Ophthalmol. 2007 Jan 3; [Epub ahead of print].

Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.