Dorairaj, Syril K.

Abstract In this study, we quantified differences in iris stiffness between female and male subjects in healthy and postlaser peripheral iridotomy (post-LPI) groups using an image-based inverse modeling approach. We analyzed anterior segment optical coherence tomography (AS-OCT) images from 25 participants across four groups. Finite element models were created using **solidworks, **abaqus, and a custom C program, modeling the iris as a neo-Hookean material. We found that post-LPI females had significantly higher normalized elastic modulus (E′=3.81±1.74) than healthy females (E′=0.92±0.31,p=0.004), while no significant difference was observed in males. Post-LPI females also showed significantly higher stiffness than post-LPI males (p=0.003). Here, p denotes the probability value, with p<0.05 considered statistically significant. Our findings suggest that sex-based differences in iris biomechanics may contribute to the higher susceptibility of females to primary angle-closure disease. Despite the small sample size, this preliminary study highlights the need for larger, sex-stratified investigations into glaucoma pathophysiology.

Precis: This study is the first to report micropulse transscleral cyclophotocoagulation (MP-TSCPC) use in only good vision patients. MP-TSCPC significantly reduced intraocular pressure (IOP) and glaucoma medication use without any significant reduction in visual acuity at every postoperative follow-up point. Purpose: To evaluate outcomes of MP-TSCPC in eyes with baseline best-corrected visual acuity (BCVA) of ≥20/60. Methods: A retrospective review of patients who underwent MP-TSCPC at Mayo Clinic and Ross Eye Institute from July 2016 to August 2017 with BCVA of ≥20/60, and a minimum of 3 months follow-up. Results: A total of 61 eyes of 46 patients (68.80±17.12 y) underwent MP-TSCPC with a mean follow-up of 10.2±3.1 months. Mean IOP and mean number of glaucoma medications used were significantly reduced from baseline at every follow-up time point ( P <0.0001). At month 12, mean IOP was reduced 40.2% from baseline with 85.4% of the patients having an IOP reduction of ≥20%, and mean glaucoma medication use reduced by 0.82±0.53 with 79.6% of the patients having a reduction of ≥1 medication. There was no significant reduction in BCVA from baseline at any follow-up point ( P >0.05), except for 10 eyes with a vision loss of ≥2 lines and 5 out of 10 eyes had cataract progression. The probability of complete success (IOP range, 6 to 21 mm Hg or ≥20% IOP reduction; BCVA loss ≤2 lines, no reoperation for glaucoma) was 74.14%, 83.61%, 84.21%, and 75.0% at months 1, 3, 6, 12, respectively. The probability of qualified success (above criteria for IOP, no reoperation and BCVA loss >2 lines) was 81.03%, 91.80%, 94.74%, and 93.75% at months 1, 3, 6, 12, respectively. Conclusions: MP-TSCPC should be considered earlier in the management of glaucoma and can possibly be offered as an alternative to incisional glaucoma surgeries.

Purpose: The purpose of the study is to describe short-term efficacy and safety of goniotomy with trabecular meshwork excision using the Kahook Dual Blade (KDB, New World Medical Inc., Rancho Cucamonga, CA) in patients with severe or refractory glaucoma. Method: Retrospective multicentric case series of 53 eyes with severe or refractory glaucoma as defined by ICD-10 conducted in the United States, Mexico, and Switzerland. Primary efficacy outcome was a ≥20% decrease in intraocular pressure (IOP) from baseline at 6 months. Secondary efficacy outcome measures were probability of achieving an IOP≤14 or 18 mm Hg at 6 months and the mean IOP change from baseline at 6 months. Medication use required to obtain target IOP at last follow up and adverse effects were analyzed. Results: The proportion of eyes achieving an IOP reduction of >20% from preoperative baseline at 6 months was 57.7% (n=30). The mean IOP decreased from 18.4±6.1 mm Hg at baseline to 13.9±3.5 mm Hg at month 6 (23.9% reduction; P<0.001). At 6 months, 63.5% and 92.3% achieved an IOP≤14 and ≤18 mm Hg, respectively, and the mean number of glaucoma medications was reduced by 1.2±1.3 (36.6%) compared with baseline (P<0.001). The most common adverse event was hyphema (n=29, 34.9%) with spontaneous resolution in all cases. No severe complications were reported. One case presented with uncontrolled IOP and required glaucoma drainage device surgery at 1 month. Conclusions: Goniotomy with trabecular meshwork excision using the KDB could be an alternative surgery for severe or refractory glaucoma, significantly reducing IOP and medication use at 6 months, with a low rate of complications.

Quantifying the mechanical properties of the iris is important, as it provides insight into the pathophysiology of glaucoma. Recent ex vivo studies have shown that the mechanical properties of the iris are different in glaucomatous eyes as compared to normal ones. Notwithstanding the importance of the ex vivo studies, such measurements are severely limited for diagnosis and preclude development of treatment strategies. With the advent of detailed imaging modalities, it is possible to determine the in vivo mechanical properties using inverse finite element (FE) modeling. An inverse modeling approach requires an appropriate objective function for reliable estimation of parameters. In the case of the iris, numerous measurements such as iris chord length (CL) and iris concavity (CV) are made routinely in clinical practice. In this study, we have evaluated five different objective functions chosen based on the iris biometrics (in the presence and absence of clinical measurement errors) to determine the appropriate criterion for inverse modeling. Our results showed that in the absence of experimental measurement error, a combination of iris CL and CV can be used as the objective function. However, with the addition of measurement errors, the objective functions that employ a large number of local displacement values provide more reliable outcomes.