Quantification of Focal Outflow Enhancement Using Differential Canalograms.

Area of Science:

• Ophthalmology
• Glaucoma Research
• Surgical Innovation

Background:

• Glaucoma is a leading cause of blindness characterized by elevated intraocular pressure.
• Ab interno trabeculectomy (AIT) is a surgical technique aimed at improving aqueous humor outflow.
• Accurate quantification of outflow changes post-AIT is crucial for evaluating its efficacy.

Purpose of the Study:

• To quantify regional changes in conventional aqueous humor outflow following ab interno trabeculectomy (AIT).
• To establish and validate a novel method for measuring outflow alterations after AIT.

Main Methods:

• Plasma-mediated AIT was performed on enucleated pig eyes.
• A custom R package (eye-canalogram) was developed for automated outflow quantification using fluorescent tracer reperfusion.
• Two-dye reperfusion canalograms and histology were used to assess trabecular meshwork (TM) ablation and Schlemm's canal patency.

Main Results:

• Histology confirmed TM ablation and unroofing of Schlemm's canal segments.
• Differential canalograms revealed significant outflow increases: 17±5-fold inferonasally and 14±3-fold superonasally.
• Outflow also increased in other quadrants (2±1-fold superotemporally, 3±3-fold inferotemporally), with accelerated nasal filling and perilimbal flow.

Conclusions:

• A quantitative, differential canalography technique was successfully developed.
• This method enables precise measurement of supraphysiological outflow enhancement achieved by AIT.
• The findings demonstrate AIT's potential to substantially increase aqueous humor outflow in a clinically relevant model.