Effect of Subconjunctival Microshunt Implantation on Intraocular Pressure Variation in Patients with Glaucoma
Authors: James J. Armstrong, Matthew B. Schlenker, Iqbal Ike Ahmed. University of Toronto.
Author Disclosure Block: J.J. Armstrong: None. M.B. Schlenker: Santen Pharmaceutical Co.; Alcon ; Allergan; Johnson & Johnson Vision; Labtician Thea; Light Matter Interaction Inc. I.I. Ahmed: Aequus (C); Aerie Pharmaceuticals ; Akorn; Alcon; Allergan; Aquea Health, Inc; ArcScan; Bausch Health; Beaver Visitec; Beyeonics; Carl Zeiss Meditec , Centricity Vision, Inc; CorNeat Vision; Costum Surgical; ELT Sight; ElutiMed; Equinox ; eyeFlow, Inc; Genentech; Glaukos; Gore; Iantrek; InjectSense; Iridex; iStar; Ivantis; Johnson & Johnson Vision; LayerBio ; Leica Microsystems ; Long Bridge Medical, Inc; MicroOptx; MST Surgical; Mundipharma ;, New World Medical ; Ocular Instruments ; Ocular Therapeutix; Oculo; Omega Ophthalmics ; PolyActiva (; Radiance Therapeutics, Inc ; Ripple Therapeutics ; Sanoculis , Santen ; Shifamed, LLC ; Sight Sciences ; Smartlens, Inc ; Stroma ; Thea Pharma ; ViaLase; Vizzario .
Purpose: IOP fluctuates diurnally and single measurements in clinic are known to be rather poor at identifying individuals with occult IOP spikes. Although mean IOP is the most widely recognized risk factor for glaucoma progression, recent expert opinion considers this method of monitoring problematic. Means do not capture differences in intensity of IOP-lowering therapy, nor provide information regarding changes to outflow capacity. Previous studies demonstrate that peak IOP and IOP fluctuation may be a better predictor of glaucoma progression. The magnitude of IOP peaks and fluctuation are predictive of visual field progression risk. The purpose of this study was to assess IOP peak and fluctuation using home tonometry and the water drinking test (WDT) before and after subconjunctival microshunt implantation.
Study Design: Prospectivecohort.
Methods: Patients scheduled for subconjunctival microshunt implantation were recruited and underwent 7-days of iCare home tonometry with a WDT one month before surgery, and again 6-months postoperatively (±1-month). Home tonometry measurements were requested 6-7 per day. The WDT began with a baseline Goldmann applanation tonometry (GAT) reading immediately before patients were asked to drink 10mL/kg of water. Additional GAT measurements were taken every 15min for 1- hour after fluid consumption. Maximum, minimum, and mean IOP were compared between baseline and post-operative measurements for both home tonometry and WDT. IOP fluctuation was calculated as the standard deviation of the measured IOPs during each of the home tonometry periods or WDTs. Results: A total of 20 patients were enrolled. Baseline median (IQR) age was 64 (54-71), mean deviation was -10.85 (-22.33 to -13.32), IOP was 23.5 (19-31) and medication classes were 3.5 (3-4). Water drinking test revealed significant reductions in peak IOP (-15 [6-23]mmHg; p<0.001), median[IQR] IOP (-13.8 [12-14] mmHg; p<0.001), and IOP fluctuation (-1.6 [1.2-2.1] mmHg; p<0.001). Home tonometry found a post-operative median (IQR) IOP of 9.1 (6.9-13.4) mmHg, with a significant reduction in peak IOP (-15.5 [9-23] mmHg; p<0.01), median [IQR] IOP (-9.2 [7-14] mmHg; p<0.001), and IOP fluctuation (-1.6 [1.4-2.9] mmHg; p<0.01) compared to baseline.
Conclusions: Glaucoma filtration surgery with microshunt implantation significantly reduces mean IOP, the difference between patient’s highest and lowest IOP, and IOP fluctuation. This study’s findings indicate that subconjunctival microshunts improve patient IOP profiles, suggesting an increase in outflow capacity and a reduction in visual field progression risk.