Less Invasive Glaucoma Surgery Can Be Effective in Short Term

Study of SLOT ab interno in 12 FAP patients suggests it might be first approach

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

Share this article:

Share article via email
An illustration of a person's eye seen through a telescope.

A surgical procedure called suture trabeculotomy (SLOT) ab interno successfully treated glaucoma in nearly half of the eyes of familial amyloid polyneuropathy (FAP) patients treated in a Japanese study, although its effectiveness declined over several years.

Eight patients required additional surgery to help treat their glaucoma, a condition marked by fluid buildup in the eye, leading to increased pressure that can ultimately cause damage and blindness.

This surgical approach may not be a long-term solution for glaucoma in these people, but could be used as a first-line defense, especially for “young or hesitant patients” who are not ready to undergo more significant surgery, according to its researchers.

Recommended Reading
An illustration of a woman's brain, shown in profile.

CNS Affected at Early Stages in FAP Patients With Val30Met Mutation

Secondary glaucoma can be a difficult-to-treat FAP complication

The study, “Suture trabeculotomy ab interno for secondary glaucoma in Japanese patients withVal30Met hereditary transthyretin amyloidosis,” was published in the journal Scientific Reports.

A type of hereditary transthyretin amyloidosis, or ATTRv amyloidosis, FAP is marked by the accumulation of an abnormal form of the transthyretin protein in various organs and nerve cells.

Mutations in the TTR gene cause FAP, with the most common being Val30Met. This mutation is most prevalent in Portugal, Sweden, and Japan.

Patients can experience transthyretin buildup in the aqueous humor, the jellylike substance in the eyes, and a range of ocular symptoms like glaucoma.

The widespread use of liver transplants and emergence of new FAP treatments in recent years significantly lowered the production of transthyretin fibrils, among other benefits.

Yet, tissues in the eyes are particularly resistant to treatment and continue to produce the abnormal protein, making ocular symptoms like glaucoma difficult to address, the researchers noted.

“This continuous production of ATTRv may explain the difficulty in reducing the [intraocular pressure] and why the course of glaucoma in these patients is accelerated,” they wrote.

SLOT ab interno is less invasive than similar surgical approaches, aiming to treat glaucoma and lower intraocular pressure by directing the flow of fluid out of the eyes. It is considered safe and is rarely associated with serious side effects.

Researchers assessed the outcomes of patients with the Val30Met mutation and glaucoma secondary to the disease, who underwent a SLOT ab interno procedure between May 2015 and January 2020.

Their analysis covered 18 eyes of 12 people, including seven women, with a mean age of 48.3 at the time of surgery. All had a liver transplant at a mean age of 33.5, and they were followed for a mean of 3.5 years after the SLOT ab interno procedure.

The surgery’s success rate — marked by a sufficient drop in intraocular pressure — was 83% after one year, 63% after two years, and 22% after three and four years.

“Our results suggest that SLOT ab interno … may not have a sufficiently long-term effect on secondary glaucoma resulting from ATTRv amyloidosis,” the researchers wrote.

Ten eyes in eight patients were considered surgical failures, meaning their intraocular pressure failed to drop sufficiently. They required additional procedures to address their glaucoma.

Clinical factors, such as age, sex, disease length, and prior eye surgery did not influence the likelihood of surgical success.

Both the mean intraocular pressure and number of anti-glaucoma medications used were significantly reduced at all measured timepoints over two years of follow-up after surgery. Visual acuity did not change significantly.

All patients experienced a backflow of blood into the eye during surgery, and blood pooled in the eye’s chamber after surgery in seven eyes. This complication was resolved without treatment in all cases.

Researchers noted the lack of “sufficiently long-term effect” with this surgery for glaucoma secondary to FAP may be due to residual production of transthyretin fibrils.

“Our insufficient results suggested that continuous amyloid deposition … may result in [intraocular pressure] increases even after SLOT ab interno,” they wrote.

While the approach may compromise somewhat on efficacy compared with other surgical procedures for glaucoma, its relatively quick, safe, and less invasive nature suggest SLOT ab interno could be a first approach before advancing to more invasive surgeries, the researchers concluded.

Still, “further studies with larger cohorts and longer follow-up” are needed, they added.