Sunee Chansangpetch

Optical coherence tomography angiography in glaucoma care

ABSTRACT Purpose: To provide the reader with information on the principal techniques of optical coherence tomography angiography (OCTA); the current literature on OCTA reproducibility; its applications to glaucoma detection and monitoring of progression; and the role of OCTA in the assessment of the vascular component in glaucoma pathogenesis.Methods: A literature review of the pertinent publications for the OCTA in relation to the development, techniques, and its use in glaucoma was carried out.Results: Rapid improvements in optical coherence tomography (OCT) technology have allowed for enhancement of both image resolution and scanning speed, and the development of vascular assessment modality. OCTA is the non-invasive in vivo imaging of the vasculature located within the retina and optic nerve head area. The principle of OCTA is to use the variations in OCT signals caused by moving particles as the contrast mechanism for imaging of flow. Several algorithms which aim to maximize the contrast signal and minimize the noise have been developed including the phase-based techniques, intensity-based techniques (e.g., split-spectrum amplitude decorrelation angiography (SSADA)), and complex-based techniques (e.g., optical microangiography (OMAG)). With its reliable technique, high image resolution, and current availability, OCTA has been widely used in the assessment of posterior segment diseases including glaucoma in which ocular perfusion dysfunction has been proposed as a pathophysiological mechanism.Conclusion: OCTA may enhance our knowledge of glaucoma pathogenesis and offer an improvement in our ability to detect glaucomatous change.

Anterior Segment Imaging for Angle Closure

PURPOSEnTo summarize the role of anterior segment imaging (AS-imaging) in angle closure diagnosis and management, and the possible advantages over the current standard of gonioscopy.nnnDESIGNnLiterature review and perspective.nnnMETHODSnReview of the pertinent publications with interpretation and perspective in relation to the use of AS-imaging in angle closure assessment focusing on anterior segment optical coherence tomography and ultrasound biomicroscopy.nnnRESULTSnSeveral limitations have been encountered with the reference standard of gonioscopy for angle assessment. AS-imaging has been shown to have performance in angle closure detection compared to gonioscopy. Also, imaging has greater reproducibility and serves as better documentation for long-term follow-up than conventional gonioscopy. The qualitative and quantitative information obtained from AS-imaging enables better understanding of the underlying mechanisms of angle closure and provides useful parameters for risk assessment and possible prediction of the response to laser and surgical intervention. The latest technologies-including 3-dimensional imaging-have allowed for the assessment of the angle that simulates the gonioscopic view. These advantages suggest that AS-imaging has a potential to be a reference standard for the diagnosis and monitoring of angle closure disease in the future.nnnCONCLUSIONSnAlthough gonioscopy remains the primary method of angle assessment, AS-imaging has an increasing role in angle closure screening and management. The test should be integrated into clinical practice as an adjunctive tool for angle assessment. It is arguable that AS-imaging should be considered first-line screening for patients at risk for angle closure.

Agreement of Anterior Segment Parameters Obtained From Swept-Source Fourier-Domain and Time-Domain Anterior Segment Optical Coherence Tomography

Purpose To assess the interdevice agreement between swept-source Fourier-domain and time-domain anterior segment optical coherence tomography (AS-OCT). Methods Fifty-three eyes from 41 subjects underwent CASIA2 and Visante OCT imaging. One hundred eighty–degree axis images were measured with the built-in two-dimensional analysis software for the swept-source Fourier-domain AS-OCT (CASIA2) and a customized program for the time-domain AS-OCT (Visante OCT). In both devices, we examined the angle opening distance (AOD), trabecular iris space area (TISA), angle recess area (ARA), anterior chamber depth (ACD), anterior chamber width (ACW), and lens vault (LV). Bland-Altman plots and intraclass correlation (ICC) were performed. Orthogonal linear regression assessed any proportional bias. Results ICC showed strong correlation for LV (0.925) and ACD (0.992) and moderate agreement for ACW (0.801). ICC suggested good agreement for all angle parameters (0.771–0.878) except temporal AOD500 (0.743) and ARA750 (nasal 0.481; temporal 0.481). There was a proportional bias in nasal ARA750 (slope 2.44, 95% confidence interval [CI]: 1.95–3.18), temporal ARA750 (slope 2.57, 95% CI: 2.04–3.40), and nasal TISA500 (slope 1.30, 95% CI: 1.12–1.54). Bland-Altman plots demonstrated in all measured parameters a minimal mean difference between the two devices (−0.089 to 0.063); however, evidence of constant bias was found in nasal AOD250, nasal AOD500, nasal AOD750, nasal ARA750, temporal AOD500, temporal AOD750, temporal ARA750, and ACD. Among the parameters with constant biases, CASIA2 tends to give the larger numbers. Conclusions Both devices had generally good agreement. However, there were proportional and constant biases in most angle parameters. Thus, it is not recommended that values be used interchangeably.

Consensus recommendations for trabecular meshwork cell isolation, characterization and culture

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.

Use of Nd:YAG laser to recanalize occluded Cypass Micro-Stent in the early post-operative period

Purpose To report the first case of Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser use to recanalize a CyPass occluded with a clot in the early postoperative follow-up. Observations A 66 year-old woman with primary open angle glaucoma and cataract received combined cataract surgery plus CyPass in the right eye. Surgery was uneventful, however, there was a small amount of hyphema related to bleeding around the site of Cypass insertion. Intraocular pressure (IOP) was between 6 and 7u202fmmHg in the first week on no glaucoma medications. At the second postoperative week, IOP jumped to 30u202fmmHg and a clot was observed obstructing the CyPass lumen. We disrupted the clot with a single shot from a Nd:YAG laser. Twenty minutes after the laser, the IOP was 8u202fmmHg. CyPass was recanalized without complications. IOP was 11u202fmmHg at 1 month postoperatively with timolol 0.5% twice a day. Conclusions and importance It is important to perform gonioscopy to evaluate for CyPass obstruction in cases of IOP spike. Nd:YAG laser may be a useful approach to recanalize the CyPass in the early postoperative follow-up.

Efficacy of Cataract Surgery With Trabecular Microbypass Stent Implantation in Combined-Mechanism Angle Closure Glaucoma Patients

PURPOSEnTo evaluate the effectiveness of trabecular microbypass stent (iStent) implantation in combined mechanism glaucoma (CMG).nnnDESIGNnRetrospective cohort study.nnnMETHODSnWe reviewed the medical charts of patients with the following scenarios: (1) primary open-angle glaucoma (POAG) undergoing phacoemulsification (PE), (2) POAG undergoing PE with iStent (POAG-PE/iStent), (3) CMG undergoing PE (CMG-PE), and (4) CMG undergoing PE with iStent (CMG-PE/iStent). CMG was defined as narrow-angle glaucoma patients whose angle had opened after iridotomy. Linear mixed-effects models were performed to determine the effect of iStent on postoperative 1-year success rate (intraocular pressure [IOP] ≤ 18 without medication), IOP, and number of medications.nnnRESULTSnData from 301 eyes were available. The number of eyes (subjects) was 61 (45) in the POAG-PE, 60 (50) in POAG-PE/iStent, 93 (76) in CMG-PE, and 87 (70) in CMG-PE/iStent group. Success criteria were achieved in 13.1% for POAG-PE, 33.3% for POAG-PE/iStent (POAG-PE vs POAG-PE/iStent B 3.01; P < .001), 37.6% for CMG-PE, and 43.7% for CMG-PE/iStent (CMG-PE vs CMG-PE/iStent B 2.25; P < .001). There was no difference in the IOP between POAG-PE and POAG-PE/iStent, and between CMG-PE and CMG-PE/iStent. The iStent significantly reduced number of medications in the POAG (Bxa0-0.70; Pxa0<xa0.001) and CMG group (Bxa0-0.52; P < .001). Comparing the effect of iStent on POAG and CMG, the analysis showed similar iStent efficacy in terms of the success rate, IOP, and number of medications (P > .05).nnnCONCLUSIONSnCombined PE/iStent significantly increased success rate and reduced number of medications in CMG patients compared to PE alone. The effects of iStent were comparable between POAG and CMG groups.

Comparison of Anterior Segment Optical Coherence Tomography Parameters Among Vietnamese, Chinese, and Whites

PURPOSEnTo evaluate the difference in anterior segment optical coherence tomography (AS-OCT) parameters among ethnic Vietnamese, Chinese, and whites.nnnDESIGNnCross-sectional study.nnnMETHODSnWe prospectively recruited phakic nonglaucomatous participants (based on intraocular pressure <xa021xa0mm Hg, normal optic nerve head and retinal nerve fiber, and cup-to-disc ratio < 0.6) of 3 ethnic groups-Vietnamese, Chinese, and white. AS-OCT parameters including angle (angle opening distance, trabecular-iris space area, and angle recess area), iris (iris thickness, iris area, and iris curvature [Icurv]), and anterior chamber parameters (anterior chamber depth, width [ACW], area, and lens vault [LV]) were obtained. A linear regression model with adjustment for age, sex, axial length, and pupillary diameter was used for analysis. Subgroup analysis was performed in closed- and open-angle subgroups, which were defined in eyes with gonioscopically visible posterior trabecular meshwork for less than 2 quadrants (closed) and equal to or more than 2 quadrants (open).nnnRESULTSnData were obtained from 126 Vietnamese, 124 Chinese, and 112 white participants. Mean (standard deviation) age of participants was 60.2 (11.8) years. Among overall subjects, Vietnamese had significantly smaller values in all angle and anterior chamber parameters than Chinese and white subjects (all P ≤ .001) except LV. Vietnamese had significantly higher Icurv than Chinese (Bxa0-0.065, P < .001) and white subjects (Bxa0-0.073, P < .001). In the open-angle subgroup, Vietnamese had significantly smaller angle and anterior chamber dimensions (P ≤ .001) and thicker iris (P < .001) than whites, whereas there was no significant difference in all parameters compared to Chinese except for smaller ACW in Vietnamese (P < .001). In the closed-angle subgroup, Vietnamese possessed smaller angle, smaller anterior chamber dimensions, and higher Icurv than Chinese and white subjects (P < .001). Vietnamese had significantly greater LV compared to Chinese (Bxa0-204.8, Pxa0= .001).nnnCONCLUSIONnVietnamese subjects had more of the anatomic characteristics associated with risk for angle closure, including small anterior chamber dimension, high iris curvature, and high lens vault, compared to the other 2 ethnicities.

Impact of Myopia on Corneal Biomechanics in Glaucoma and Nonglaucoma Patients

Purpose We evaluated the impact of myopia on corneal biomechanical properties in primary open-angle glaucoma (POAG) and nonglaucoma patients, and the effect of modification of glaucoma on myopic eyes. Methods This cross-sectional study included 66 POAG eyes (33 myopia, 33 nonmyopia) and 66 normal eyes (33 myopia, 33 nonmyopia). Seven corneal biomechanical parameters were measured by ultra-high-speed Scheimpflug imaging, including corneal deformation amplitude (CDA), inward/outward corneal applanation length (ICA, OCA), inward/outward corneal velocity (ICV, OCV), radius, and peak distance (PD). Results Mean age (SD) of the 65 male (49%) and 67 female (51%) patients was 59 (9.82) years. Myopia was associated with significantly higher CDA (adjusted effect = 0.104, P = 0.001) and lower OCV (adjusted effect = −0.105, P < 0.001) in the POAG group. Within the nonglaucoma group, myopic eyes had a significantly lower OCV (adjusted effect = −0.086, P < 0.001) and higher CDA (adjusted effect = 0.079, P = 0.001). All parameters except PD suggested that glaucoma modified the effect of myopia on corneal biomechanics. Percentage differences in the adjusted myopic effect between POAG and nonglaucoma patients was 31.65, 27.27, 31.65, 50.00, 22.09, and 60.49 for CDA, ICA, OCA, ICV, OCV, and radius, respectively. Conclusions Myopia had a significant impact on corneal biomechanical properties in the POAG and nonglaucoma groups. The differences in corneal biomechanical parameters suggest that myopia is correlated with significantly lower ocular rigidity. POAG may enhance the effects of myopia on most of these parameters.