Human Vitreous Collagen Fragments Dimension As a Function of Vitrectomy Cut Rate

Purpose: To study the dimensions and distribution of human vitreous collagen type II fragments collected after vitrectomy performed at varying cut rates and to evaluate if increasing the cut rate produces smaller collagen fragments, thus reducing retinal traction and/or viscosity. Methods: Fluid was collected during core vitrectomies performed for macular surgery at cut rates from 1000 to 16,000 cuts per minute (CPM) and immediately refrigerated. Protein fractions were separated by molecular weight (MW; >100 kDa, 50-100 kDa, 50-30 kDa, 30-10 kDa, and <10 kDa) through centrifugal filters. The Human Collagen II ELISA Kit colorimetric assay was then used to measure the COL2A1 in unfiltered and filtered samples. Results: Vitreous samples collected after vitrectomy performed at 16,000 CPM contained a higher concentration of protein with MW over 100 kDa than at any other cutting frequency (P < 0.01). No significant differences were found in fractions collected with a MW between 50 and 100 kDa. Collagen type II fragments over 100 kDa were significantly more represented than smaller fragments at each cut rate. The proportion of smaller (50-100 kDa) collagen fragments compared with those over 100 kDa was higher at 2000 CPM than at higher cut rates. Conclusions: Vitreous samples collected at different cut rates do not contain a significantly different proportion of collagen type II fragments of the tested MW. The extreme variability of vitreous flow through the cutter port may explain the uncertain predictability of collagen fragment MWs. Translational relevance: Increasing the cut rate does not produce vitreous fragments of proportionally smaller dimension. It is necessary to achieve an invariant instantaneous flow through the cutter port in order to decrease retinal traction during vitrectomy

Central corneal thickness and glaucoma treatment: An Italian multicenter cross-sectional study

Purpose: Supposedly, prostaglandin analogs (PGA) could reduce the central corneal thickness (CCT), while topical carbonic anhydrase inhibitors (TCAI) could increase CCT. The aim of the study was to evaluate clinically significant CCT effects in patients treated with PGA or TCAI. Methods: At least 50 glaucomatous patients were saved on the Italian Glaucoma Register from 16 different glaucoma centers. About 816 glaucomatous patients were found in the register; of these, 316 were recruited in this study because they were treated with PGA or TCAI. The diagnosis of glaucoma was based on visual field examination, optic nerve head analysis, intraocular pressure (IOP) measurements, and gonioscopy. Two age-matched subgroups were created: one treated with PGA and the other with TCAI. CCT, ophthalmoscopic cup/disc ratio (CDR), mean deviation (MD), pattern standard deviation (PSD), and IOP were considered for both eyes of each patient. Student t-test was used to compare the 2 subgroups. Results: The mean age of the PGA group was 66.35±12.17 years, while 65.17±12.52 years was for the TCAI group. No significant difference was found for CCT (543.75±35 μm and 544±35 μm, respectively), CDR (0.55±0.2 and 0.53±0.2, respectively), MD (-4.5±4.9 dB and -5.4±6.4 dB, respectively), PSD (4.6±3.4 and 4.6±4.9, respectively), and IOP (15.9±3.3 mmHg and 15.7±2.9 mmHg, respectively) between the 2 subgroups. A significant (P<0.001) correlation was found between CCT and CDR and between CCT and IOP. Conclusion: No significant difference in CCT was found between patients treated with PGA and TCAI, suggesting that these topical medications did not statistically and clinically change the CCT. © Copyright 2013, Mary Ann Liebert, Inc

Ocular perfusion pressure control during pars plana vitrectomy: testing a novel device

Purpose: To study the efficacy of a novel device intended to control infusion pressure based on mean ocular perfusion pressure (MOPP) during pars plana vitrectomy (PPV). Methods: An arm blood pressure cuff connected to a vitrectomy machine calculated mean arterial pressure (MAP), while a pressure sensor close to the infusion trocar measured intraocular pressure (IOP). MOPP was calculated in real time in 36 consecutive patients undergoing PPV, who were divided into two groups. The device lowered IOP every time that calculated MOPP fell below 30 mmHg in the Control ON group (18 patients), while no action was taken in the Control OFF group (18 patients). Results: Baseline IOP and blood pressure were similar between groups. The Control ON group had significantly lower average intraoperative IOP (30.5 ± 2.1 vs. 35.9 ± 6.9 mmHg; p = 0.002) and higher MOPP (56.4 ± 5.9 vs. 49.7 ± 6.1 mmHg) than the Control OFF group. The Control ON group also spent less time at MOPP < 10 mmHg and < 30 mmHg: 0 vs. 3.40 ± 2.38 min (p < 0.001) and 9.91 ± 7.15 vs. 16.13 ± 8.12 min (p = 0.02), respectively. Conclusions: The MOPP control device effectively maintained lower IOP and higher MOPP throughout surgery. It also helped avoid dangerous IOP peaks and MOPP dips, allowing patients to spend less time at MOPP of < 10 and < 30 mmHg

Does the Bursa Pre-Macularis protect the fovea from shear stress? A possible mechanical role

Purpose of present study is to evaluate whether the Pre-Macular Bursa (PMB) modifies Wall Shear Stress (WSS) at the retinal surface during saccadic movements. We created a mathematical model consisting of 25,000 grid cells and simulated a horizontal saccade spanning 50° in 0.17s, both in absence and in presence of the PMB. Wall Shear Stress SS was computed throughout the retinal surface and the posterior pole was divided into 3 Zones comprising 400 nodes each: Zone 1 (radius 3.5 mm; 0°–17°) corresponding to the PMB area; Zone 2 (concentric annular area 5 mm in radius; 22°) and Zone 3 (concentric annular area 5.5 mm; 28°). The PMB reduced WSS significantly at the macula and increased it in the immediate surroundings. Average WSS in Zone 1 was 1.53 ± 1.01 (max 4.23 Pa) with PMB Vs 6.94 ± 9.23 (max 35.83 Pa) without. Zone 2 WSS was 9.39 ± 10.33 (max 48.36 Pa) with PMB Vs 6.95 ± 9.40 (max 38.60 Pa) without Zone 3 WSS was 8.41 ± 10.03 (max 43.16 Pa) with PMB Vs 6.88 ± 9.42 (max 39.43 Pa) without (p < 0.001 in all cases). The PMB significantly reduces WSS over the retinal surface underlying the bursa region; conversely, WSS slightly increases it in the immediate neighboring areas

Tutto quello che avreste voluto sapere sul glaucoma e non avete mai osato chiedere

215 risposte evidence based alle domande sul glaucoma raccolte da specialisti del territorio nazional

Ocular surface changes in glaucomatous patients treated with and without preservatives beta-blockers

Purpose: To determine whether there were ocular surface changes in glaucomatous patients treated with preservatives beta-blockers who switched to preservative-free beta-blockers. Methods: This was a prospective, longitudinal, open-labeled study. One hundred thirty-two patients with primary open angle glaucoma treated with a preserved beta-blocker were enrolled. All the patients underwent perimetric and gonioscopic examination, complete ophthalmologic examination, intraocular pressure (IOP) measurements, evaluation of ocular surface, Schirmer's test, blood pressure and heart rate at baseline and 1-3 months after changing the medical treatment to a preservative-free timolol 0.1% (Timogel 0.1; Thea). At baseline, after 1 month and at the end of the study (3 months), all patients underwent a questionnaire on the visual quality and symptoms and on the quality of life (QoL). Data were analyzed by t-test when the distribution of the data was normal, by Mann-Whitney when the distribution was not normal. Results: No significant difference was found for IOP before switching from preserved beta-blockers to preservative-free ones. No significant difference was found in blood pressure and heart rate. However, a statistically significant difference was found for abnormal fluorescein staining of the cornea and conjunctiva, eyelid erythema, conjunctival hyperemia, and follicular hyperplasia. A significant difference was found for break-up time (from 9.38±4.7 s at baseline to 10.64±4.7 s after 3 months) and Schirmer's test (from 12.9±5.96 mm at baseline to 14.2±5.87 mm after 3 months). The questionnaire showed that the patient improved the dryness and foreign body sensation. Conclusion: In glaucomatous patients, preservative-free 0.1 timolol treatment improved their QoL. Similar dry eye signs or symptoms improved after 3 months of treatment reducing dryness, hyperemia, follicular hyperplasia, and foreign body sensation. © 2014 Mary Ann Liebert, Inc