AAO LIVE: Study compares increased incidence of new strabismus after tube shunt surgery in pediatric, adult patients

The American Academy of Ophthalmology's 2022 annual meeting is being held at McCormick Place in Chicago. (Images courtesy of McCormick Place)

During a presentation at the American Academy of Ophthalmology’s 2022 annual meeting in Chicago, Maria A. Guzman Aparicio, MD, and Teresa C. Chen, MD, from Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, detailed their research that found that pediatric patients have a significantly higher incidence of new-onset strabismus after tube shunt surgery for glaucoma compared with adults. 

According to past literature, adults who undergo Ahmed (New World Medical) and Baerveldt (Abbott Medical Optics) tube shunt surgeries have postoperative strabismus 2% to 12.7% of the time after 1 to 5 years. In children, the percentages range from 3% to 4.2% with Ahmed valve surgery after 16 to 24 months of follow-up.

Maria A. Guzman Aparicio, MD

In their current study with longer follow-up periods, Guzman Aparicio and Chen sought to compare the frequency of strabismus after tube shunt surgery in the adult versus pediatric populations and to identify risk factors for strabismus after tube shunt surgery.

The study included patients treated between September 1998 and September 2021. One surgeon performed all surgeries at 1 center. Pediatric patients were defined as those under 18 years of age and adults as those 18 years and older. 

Patients were excluded if they had less than 6 months of follow-up or if they had concomitant major ocular surgery.

A total of 202 patients (223 eyes) were included, of whom 169 were adults (183 eyes) and 33 were children (40 eyes). The adults were a mean age of 63.6 years, and the children were 5.2 years. A total of 237 procedures were performed, 45 in children and 192 in adults. Average follow-up was 6.1 ± 4.8 years (range, 0.6 months to 20.1 years).

Among the 237 procedures, 4% of eyes underwent 2 or 3 tube shunt procedures. Ten percent of the eyes in the pediatric population, and 2.7% of the adult population were in this group. 

Incidence of new-onset strabismus after tube shunt surgery

The determination of new-onset strabismus among a combined total of 172 adults and children without preexisting strabismus indicated that 13% of pediatric patients had new-onset strabismus after a tube shunt procedure. This is in contrast to 0% of adults with new-onset strabismus after tube shunt surgery (at 6 months or at last follow-up).

The primary take-home messages from this analysis were as follows:

- New-onset strabismus developed in 13% of pediatric patients vs. 0% of adult patients.

- In pediatric and adult patients who had pre-existing strabismus, 100% continued to have strabismus after tube shunt surgery.

Risk factors for strabismus after tube shunt surgery were being a pediatric patient, being a pediatric patient with more than 1 tube placed, and having pre-existing strabismus.

“Before doing tube shunt surgery in children, it is important to educate parents of the possibility of new-onset postoperative strabismus in up to 13% of patients,” Guzman Aparicio said.

“Best surgical technique and implant choice may minimize the chance of postoperative strabismus,” Chen concluded. “We hypothesize that our low rates of postoperative strabismus in adults may be due to putting glaucoma implants over instead of under the muscles and using Baerveldt 250 models over the 350 model.”