Malik Y. Kahook

To ascertain differences in intraocular pressure (IOP) measurement and their repeatability between dynamic contour tonometry (DCT) and Goldmann/Perkins applanation tonometry (GAT) at two different atmospheric pressures. Forty-one eyes of 41 healthy consenting subjects were enrolled for this observational, cross-sectional study. Pachymetry and IOP measurements with DCT and GAT for both eyes of each subject at Acapulco (0 m from sea level) and at Mexico City (2,234 m from sea level) were done by the same observer. The IOP was compared between tonometers at each of the altitudes, and also for repeatability of each tonometer at different altitudes. Pearson’s correlation coefficient and Bland-Altman plots were used to assess reliability of measurements and their differences at the two altitudes. The mean age of patients was 41.7 (28-66 years); 22 were females. Mean IOP with DCT was 16.1 ± 2.2 mm Hg at sea level and 15.9 ± 2.1 mm Hg at 2,234 m above sea level, not a significant difference. Mean GAT IOP at the two altitudes was 13.1 ± 1.8 and 11.5 ± 1.7 mm Hg respectively, a statistically sig -nificant difference. In contrast, central corneal thickness (CCT) was not significantly changed (548.3 to 549.4 μm, p = 0.496). Repeatability of single-observer measurements with GAT remains clinically acceptable, but not at different altitudes. The DCT seems to more consistently measure a similar IOP at different altitudes in the same subjects. The two tonometers may not be used interchangeably in the serial follow-up of patients at any of the altitudes. How to cite this article: Albis-Donado O, Bhartiya S, Gil-Reyes M, Casale-Vargas G, Arreguin-Rebollar N, Kahook MY. Citius, Altius, Fortius: Agreement between Perkins and Dynamic Contour Tonometry (Pascal) and the Impact of Altitude. J Curr Glaucoma Pract 2018;12(1):40-44.

Endophthalmitis after EX-PRESS implantation may be complicated by corneal infiltrate formation and persistent infection. Clinicians should monitor for these complications in the management of infection after EX-PRESS implantation and consider early device removal to achieve resolution.

We have developed an in situ-gelling polymer system comprised of drug-loaded micelles encapsulated within a reverse thermal gel (RTG) as an injectable ocular drug delivery system. The RTG chemistry employs a novel poly(N-isopropylacrylamide) (PNIPAAm) polymer—designed to permit complete physiological clearance of the system during degradation—coupled to a poly(serinol hexamethylene urea) (PSHU) backbone, which was designed to mimic natural materials. Inclusion of drug-loaded micelles significantly improved release kinetics of the poorly-soluble corticosteroid triamcinolone acetonide; the combined system is projected to sustain release for approximately one year based on in vitro testing. Both the RTG and micelles were well tolerated after intravitreal injection in rats.

Micro-invasive glaucoma surgery with the Glaukos iStent^® or iStent inject^® (Glaukos Corporation, Laguna Hills, CA, USA) is intended to create a bypass through the trabecular meshwork to Schlemm's canal to improve aqueous outflow through the natural physiologic pathway. While the iStent devices have been evaluated in ex vivo anterior segment models, they have not previously been evaluated in whole eye perfusion models nor characterized by computational fluid dynamics. Intraocular pressure (IOP) reduction with the iStent was evaluated in an ex vivo whole human eye perfusion model. Numerical modeling, including computational fluid dynamics, was used to evaluate the flow through the stents over physiologically relevant boundary conditions. In the ex vivo model, a single iStent reduced IOP by 6.0 mmHg from baseline, and addition of a second iStent further lowered IOP by 2.9 mmHg, for a total IOP reduction of 8.9 mmHg. Computational modeling showed that simulated flow through the iStent or iStent inject is smooth and laminar at physiological flow rates. Each stent was computed to have a negligible flow resistance consistent with an expected significant decrease in IOP. The present perfusion results agree with prior clinical and laboratory studies to show that both iStent and iStent inject therapies are potentially titratable, providing clinicians with the opportunity to achieve lower target IOPs by implanting additional stents.

Oxidative stress plays a key role in the pathophysiology of glaucoma. This study was designed to assess ethyl pyruvate (EP) as a novel antioxidative agent in cultured human trabecular meshwork (hTM) cells. Primary hTM cells were cultured on collagen matrices. Tolerance to EP was assessed at various concentrations using fluorescent vital dyes (live/dead) and metabolic (1-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. After the candidate doses were identified, cells received either preincubation with EP before hydrogen peroxide stressing or pre- and coincubation with EP before and during stressing. Live/dead and metabolic activity assays were used to quantify oxidative damage. Cultured hTM cells were well tolerant of EP concentrations at or below 10 mM while higher doses showed significant levels of cytotoxicity. In the peroxide stress assays, samples that received pre- and cotreatment with all concentrations of EP showed significantly increased cell survival and maintenance of metabolic activity. However, samples that received only pretreatment did not show a significant increase in survival rates and lost nearly all metabolic activity after peroxide-induced stressing. This work suggests that EP is a potent antioxidant that is well tolerated by hTM cells; however, EP’s potential as a therapeutic agent for glaucoma is limited by its inability to enhance endogenous antioxidant capacity. A continuous drug delivery system may be needed to realize the full therapeutic potential of EP for treatment of glaucoma.

The development of anti-vascular endothelial growth factor (VEGF) molecules has expanded the range of available treatment options for many ocular diseases, including neovascular glaucoma (NVG). A number of studies have explored the use of anti-VEGF agents as stand-alone or adjunctive treatment for NVG. Although no large, prospective, randomized trials have been performed to date, the growing body of knowledge suggests that anti-VEGF agents are effective at reversing iris and angle neovascularization and lowering intraocular pressure in patients with NVG. Response to a single injection is typically temporary; therefore, laser or incisional surgery is still necessary in most cases. Future research is needed to determine the optimal agent, dose, route of administration, and timing of treatment either as monotherapy or coupled with other medical and/or surgical interventions.