METHODS: Scanning electron microscopy was performed on P50 and P200 devices. Bench-top flow studies were performed to find the resistances of the devices. Devices were also incorporated into a perfused, ex vivo porcine sclera model to test and compare their control of pressure, with and without overlying scleral flaps, and with trabeculectomies.
RESULTS: The luminal dimensions of the P200 device were 206.4±3.3 and 204.5±0.9 μm at the subconjunctival space and anterior chamber ends, respectively. Those of the P50 device were 205.0±5.8 and 206.9±3.7 μm, respectively. There were no significant differences between the P200 and P50 devices (all P>0.05). The resistances of the P200 and P50 devices were 0.010±0.001 and 0.054±0.002 mm Hg/μL/min, respectively (P<0.05). Equilibrium pressures with overlying scleral flaps were 17.81±3.30 mm Hg for the P50, 17.31±4.24 mm Hg for the P200, and 16.28±6.67 mm Hg for trabeculectomies (P=0.850).
CONCLUSIONS: The luminal diameters of both devices are externally similar. The effective luminal diameter of the P50 is much larger than 50 μm. Both devices have low resistance values, making them unlikely to prevent hypotony on their own. They lead to similar equilibrium pressures as the trabeculectomy procedure when inserted under the scleral flap.
METHODS: The model exploits the principle of dynamic and geometric similarity, so while dimensions were up to 30× greater than actual, the flow had similar properties. Scleral flaps were represented by transparent 0.8- and 1.6-mm-thick silicone sheets on an acrylic plate. Dyed 98% glycerin, representing the aqueous humor was pumped between the sheet and plate, and the equilibrium pressure measured with a pressure transducer. Image analysis based on the principle of dye dilution was performed using MATLAB software.
RESULTS: The pressure drop across the flap was larger with thinner flaps, due to reduced rigidity and resistance. Doubling the surface area of flaps and reducing the number of sutures from 5 to 3 or 2 also resulted in larger pressure drops. Flow direction was affected mainly by suture number and position, it was less toward the sutures and more toward the nearest free edge of the flap. Posterior flow of aqueous humor was promoted by placing sutures along the sides while leaving the posterior edge free.
CONCLUSION: We demonstrate a new physical model which shows how changes in scleral flap thickness and shape, and suture number and position affect pressure and flow in a trabeculectomy.
METHODS: In this cross-sectional study, 30 severe glaucoma patients, 30 mild glaucoma patients and 30 age-matched controls were recruited. All subjects underwent standard automated perimetry, RNFL analysis and 3 T MRI examinations. Glaucoma patients were classified according to the Hodapp-Anderson-Parish classification. Pearson's correlation coefficient was used to correlate ON volume with RNFL, and receiver operating curve (ROC) analysis was performed to determine the sensitivity and specificity of ON volume in detecting glaucoma severity.
RESULTS: Optic nerve volume was significantly lower in both the left and right eyes of the severe glaucoma group (168.70 ± 46.28 mm(3); 167.40 ± 45.36 mm(3)) than in the mild glaucoma group (264.03 ± 78.53 mm(3); 264.76 ± 78.88 mm(3)) and the control group (297.80 ± 71.45 mm(3); 296.56 ± 71.02 mm(3)). Moderate correlation was observed between: RNFL thickness and ON volume (r = 0.51, p <0.001), and in mean deviation of visual field and optic nerve volume (r = 0.60, p
PURPOSE: The purpose of this study was to investigate the clinical characteristics, including 24-hour ocular perfusion pressure and risk of progression in patients with baseline central VF defect, as compared with those with peripheral VF defect in NTG.
DESIGN: This was a prospective, longitudinal study.
METHODS: A total of 65 NTG patients who completed 5 years of follow-up were included in this study. All the enrolled patients underwent baseline 24-hour intraocular pressure and blood pressure monitoring via 2-hourly measurements in their habitual position and had ≥5 reliable VF tests during the 5-year follow-up. Patients were assigned to two groups on the basis of VF defect locations at baseline, the central 10 degrees, and the peripheral 10- to 24-degree area. Modified Anderson criteria were used to assess global VF progression over 5 years. Kaplan-Meier analyses were used to compare the elapsed time of confirmed VF progression in the two groups. Hazard ratios for the association between clinical risk factors and VF progression were obtained by using Cox proportional hazards models.
RESULTS: There were no significant differences between the patients with baseline central and peripheral VF defects in terms of demography, clinical, ocular and systemic hemodynamic factors. Eyes with baseline defects involving the central fields progressed faster (difference: βcentral=-0.78 dB/y, 95% confidence interval=-0.22 to -1.33, P=0.007) and have 3.56 times higher hazard of progressing (95% confidence interval=1.17-10.82, P=0.025) than those with only peripheral defects.
CONCLUSION: NTG patients with baseline central VF involvement are at increased risk of progression compared with those with peripheral VF defect.
DESIGN: Prospective, longitudinal study.
METHODS: Sixty-five NTG patients who were followed up for 5 years are included in this study. All the enrolled patients underwent baseline 24-h IOP and BP monitoring via 2-hourly measurements in their habitual position and were followed up for over 5 years with reliable VF tests. Modified Anderson criteria were used to assess VF progression. Univariable and multivariable analyses using Cox's proportional hazards model were used to identify the systemic and clinical risk factors that predict progression. Kaplan-Meier survival analyses were used to compare the time elapsed to confirmed VF progression in the presence or absence of each potential risk factor.
RESULTS: At 5-year follow-up, 35.4% of the enrolled patients demonstrated visual field progression. There were statistically significant differences in the mean diastolic blood pressure (p 43.7 mmHg (log rank = 0.018).
CONCLUSION: Diastolic parameters of BP and OPP were significantly lower in the NTG patients who progressed after 5 years. Low nocturnal DOPP is an independent predictor of glaucomatous visual field progression in NTG patients.