Tube Shunt Implants Maintain IOP, But Many Patients Require Additional Surgery

Tube shunt implants can maintain IOP control for at least 10 years, according to an analysis published in American Journal of Ophthalmology. However, more than half of eyes in the study met failure criteria, 39% had substantial vision loss, and 34% underwent additional surgery, the investigators report. The retrospective investigation features one of the longest follow-up periods to date.

“Prior studies suggest that based on average age at time of surgery and expected longevity, most patients may live 10 years or more following glaucoma surgery,” the researchers explain, adding that most similar studies into tube shunt implants have presented 5-year data.

The research evaluated records of 85 eyes of 78 patients (54% White; 59% women; mean age, 60.6±13.1 years) who received tube shunt implants. Patients were followed for an average of 11.9±1.7 years and were evaluated for glaucomatous changes.

Researchers report the mean intraocular pressure (IOP) for patients who received tube shunt implants decreased from a preoperative value of 29.2±10.4 mm Hg to 12.6±5.8 mm Hg at 10 years. The mean number of medications fell from 3.1±1.2 to 2.2±1.4 in the same period. For participants with available visual field data, mean deviation (MD) did not worsen significantly, from mean -13.9±7.5 dB preoperatively to -17.0±7.0 dB by last visit (P =.0605). 

Best corrected visual acuity (BCVA) declined from 0.8±0.7 logMAR before surgery to 1.4±1.0 at latest appointment (P <.001). By 10 years, VA decreased by 5 lines or more for 39% of eyes, yet increased by 5 lines or more in 8%.

A comparison group of 89 eyes receiving implants, but followed at the tertiary center for less 10 years, were selected and matched to study participants by age, sex, race, and year of transplantation. Reasons for shorter post-surgery management included 58% lost to follow-up, 36% visiting an outside physician, and a small percentage who worsened to no light perception or who underwent enucleation. In the 26 eyes followed by outside physicians, data showed long-term IOP control comparable to study patients, however with fewer glaucoma implant revisions. 

“Despite surgical success in lowering pressure many patients go on to suffer additional vision loss from glaucoma and other pathology,” according to the study authors. The researchers add that 52.9% of participant eyes experienced visual acuity worsening by 2 lines or more 10 years after receiving tube shunt implants.

Limitations of the investigation included possible survivor bias, and selection bias — referrals to tertiary centers typically present more advanced disease or surgical complications.