Abstract
Purpose :
To compare conventional outflow changes following ab interno trabeculectomy (AIT) and trabecular microbypass (TMB) implantation using differential canalograms. We recently devised a method to directly observe and quantify segmental outflow. We hypothesized that outflow patterns achieved by these minimally invasive surgeries would change in distinctive patterns.
Methods :
The anterior chambers of freshly enucleated porcine eyes were gravity perfused for 15 minutes each at 15 mmHg with clear Dulbecco's Modified Eagle's Media (DMEM) followed by fluorescein and then Texas red. Optimal dye concentrations were chosen to maximize detectable fluorescence while minimizing chromophore quenching. Eight eyes served to establish the fluorescent tracer reperfusion technique before quantification of outflow changes were achieved by AIT (trabectome, Neomedix, Tustin, CA) in 17 eyes and TMB (iStent, Glaukos, Laguna Hills, CA) in 16 eyes. A stereo dissecting microscope equipped for fluorescent imaging captured time lapse images every 20 seconds of the chromophore flow patterns. Half-maximum quadrant fluorescence intensities were analyzed using ImageJ software.
Results :
Time lapse analysis in the controls revealed a mean increase of 56±8% fluorescence units for FU compared to TR. Significant differences (p<0.05) were observed in the inferonasal (IN), superonasal (SN), and superotemporal (ST) quadrants. Canalogram filling patterns indicated filling of 6 clock hours after AIT and a more focal and less predictable access after TMB. A normalization coefficient (c=1.56) was used to correct TR fluorescence values to match the intensity of FU at identical time points in each time lapse pair. TMB implantation demonstrated fluorescent intensity increases of 13±5%, 14±8%, 9±3%, and 24±9% in the IN, SN, ST, and IT quadrants, respectively (p>0.05). AIT resulted in a 100±50% (p=0.002), 75±28% (p=0.002), 19±8%, and 40±21% increase in these quadrants. Comparison of these two outflow enhancing modalities showed that the AIT eyes had fluorescent intensity increases of 71±36% (p=0.01), 65±30% (p=0.004), 22±10%, and 22±12% in the four respective quadrants when compared to TMB implantation.
Conclusions :
AIT provides more extensive access to the outflow pathway and a larger enhancement of outflow facility compared to TMB.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.