Corneal Invasion by Filtering Bleb A Distinct Disease Entity

Corneal invasion by filtering bleb (CIFB) is a distinct disease entity and may be caused by adhesion of the posterior boundary and forward displacement of the internal opening of the filtering bleb, according to research published in BMC Ophthalmology. Removal of the adhesion of the posterior boundary of the filtering bleb can halt its progression, the report shows.

In this single-center study, researchers described the clinicopathological characteristics and possible etiology of CIFB after filtering surgery in a group of 22 patients (mean age, 56.3±8.8 years; 54% men and 48% women) who developed corneal invasion by filtering bleb after undergoing filtration surgery for glaucoma between March 2005 and March 2022. 

Patients had an average follow-up duration of 29.64±18.67 months. Follow-up examinations included slit-lamp examination, optical coherence tomography, ultrasound biomicroscopy, and histopathological examination. 

Glaucoma stage at the time of filtering surgery was moderate in 32% and advanced in 68% of patients. The corneal invasion by filtering bleb  was considered mild in 50%, moderate in 32%, and severe in 18% of patients. The mean time interval between filtering surgery and onset of CIFB was 22.41±23.99 months.

The researchers found the filtering blebs were closely connected with the cornea, invading the corneal stroma, and had locally adhered posterior boundaries. They observed forward displacement of the internal opening of the filtering bleb in 4 of 7 patients who underwent surgical treatment. 

Although researchers have yet to elucidate the mechanism of bleb invasion into the cornea, the consensus seems to believe that it is closely related to the surgical incision and the use of antiproliferative drugs such as mitomycin C, according to the report.

“In general, we believe that CIFB is a distinct disease entity that differs from [overhanging filtering bleb] in terms of clinical manifestations, etiology, histopathology, and optimal treatment method,”  according to the researchers. “The progression of CIFB can be alleviated by removing the adhesion at the posterior boundary of the filtering bleb.”