Higher incidence of new strabismus in paediatric patients following tube shunt surgery

Dr Maria A. Guzman Aparicio and Dr Teresa C. Chen, from Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, United States, found that paediatric 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.

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

Their study included patients treated between September 1998 and September 2021. One surgeon performed all surgeries at 1 centre. Paediatric 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 paediatric 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 pre-existing strabismus indicated that 13% of paediatric 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 paediatric patients vs. 0% of adult patients.

In paediatric 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 paediatric patient, being a paediatric patient with more than 1 tube placed, and having pre-existing strabismus.

Dr Guzman Aparicio commented, “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.”

Dr Chen emphasized, “Best surgical technique and implant choice may minimize the chance of postoperative strabismus.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.”