Alessandro Rossi

The ocular surface in medically controlled glaucoma: An in vivo confocal study

PURPOSEnTo study clinical and in vivo laser scanning confocal microscopy (LSCM) ocular surface findings in stable, medically controlled primary open-angle glaucoma (MCPOAG) patients.nnnMETHODSnWe recruited 100 consecutive patients with MCPOAG and 50 healthy controls. Patients had to have been treated with the same medical regimen without variation for the 18 months before enrollment and were excluded if there was a history of dry eye prior to glaucoma diagnosis. Each participant underwent ocular surface clinical and LSCM examination.nnnRESULTSnIn MCPOAG patients, subbasal nerve length and tortuosity and dendritic cell density were increased compared to controls (P < 0.01), but there were no clinical abnormalities. Patients treated with preserved drugs (n = 80) had reduced tear film breakup time (P < 0.05, ANOVA), and those preserved with benzalkonium chloride (n = 72) had reduced Schirmer test values (P < 0.001). Patients (n = 50) treated with two or more drugs had increased lissamine green conjunctival staining (P < 0.001, LSD post hoc test). Patients (n = 29) treated with three or more eye drops daily had decreased Schirmer test values. Laser scanning confocal microscopy showed subbasal changes related to preservatives, type and number of drugs, and number of eye drops.nnnCONCLUSIONSnIn stable MCPOAG patients without dry eye history, the ocular surface changes due to antiglaucoma medications are mostly subclinical. Active ingredients, preservatives, number of concomitant drugs, and number of eye drops instilled per day are all elements that can induce ocular surface changes. The clinical relevance of these changes remains to be determined.

Ocular perfusion pressure during pars plana vitrectomy: a pilot study.

PURPOSEnUnexplained visual field loss after pars plana vitrectomy (PPV) has been reported in up to 14% of all uncomplicated cases with signs varying from visual field defect and disc pallor, to optic atrophy, loss of vision, and phthisis bulbi. Among the postulated pathogenic mechanism is ocular hypoperfusion due to insufficient blood pressure (NBP) and/or elevated IOP, or to their mismatch. The purpose of this study is to assess if, to what extent, and for how long the intraoperative simultaneous variation of IOP and NBP causes mean ocular perfusion pressure (MOPP) to drop below values considered safe, during PPV.nnnMETHODSnAn IOP sensor placed in the infusion cannula recorded 6 readings per second, while arm systolic and diastolic NBP were taken every 5 minutes throughout surgery and deemed stable in between readings. Supine MOPP was calculated as (115/130) mean arterial pressure--IOP. Surgical monitor video overlay displayed all data in real time and saved them for analysis.nnnRESULTSnAverage IOP significantly increased during surgery, while NBP decreased, compared to baseline. As a result, intraoperative MOPP decreased an average 37.1% compared to baseline (range, 13.8%-58.6%; P < 0.05). Of 18 patients, 16 (88.8%) had a significant intraoperative MOPP decrease; 15/18 (83.3%) spent more than 20%, and 5/18 (27.7%) more than 50% of the entire surgery below 30 mm Hg MOPP. Surgical maneuvers, such as phacoemulsification, silicone oil removal, and fluid injection, were associated with significant MOPP decrease, while peeling and vitrectomy were not.nnnCONCLUSIONSnThe MOPP may decrease significantly in course of PPV, acutely and for longer time. Surgical maneuvers, including silicone oil removal and combined phacoemulsification, pose a higher risk for MOPP reduction. Discretion should be exercised while administering deep sedation, since it may further lower MOPP through undue blood pressure reduction.

Hydraulic Resistance of Vitreous Cutters: The Impact of Blade Design and Cut Rate

Purpose To measure the hydraulic resistance (HR) of vitreous cutters equipped with a Regular guillotine Blade (RB) or double edge blade (DEB) at cut rates comprised between 0 and 12,000 cuts per minute (CPM) and compare it with vitreous fragment size. This was an in vitro experimental study; in vivo HR measure and vitreous sampling. Methods HR, defined as aspiration pressure/flow rate, was measured in balanced salt solution (BSS; Alcon, Fort Worth, TX) (in vitro) and during pars plana vitrectomy of 20 consecutive patients aged 18 to 65, undergoing macular surgery. HR was recorded at increasing cut rates (500–6000 CPM for the RB and 500–12,000 CPM for the DEB; 5 mL/min flow). Vitreous samples were withdrawn and analyzed with Western and collagen type II and IX immunostaining to evaluate protein size. The main outcome measures were hydraulic resistance (mm Hg/ml/min [±SD]) and optic density for Western blot and immunostaining. Results RB and DEB showed identical HR in BSS between 0 and 3000 CPM. Above 3000 CPM, RB HR steadily increased, and was significantly higher than DEB HR. Vitreous HR was also similar for the two blades between 0 and 1500 CPM. Above 1500 CPM, RB offered a significantly higher resistance. Western blot and immunostaining of vitreous samples did not yield a significant difference in size, regardless of blade type and cut rate. Conclusions DEB is more efficient, offering a lower HR than RB over 1500 CPM in human vitreous. There is no viscosity reduction as a function of cut-rate between 1500 and 12,000 CPM, as HR does not vary. Translational Relevance Future vitreous cutters will benefit of a DEB; optimal cut rate needs to be defined, and the simple increase of cut rate does not provide benefits after a certain limit to be assessed.

Instantaneous Flow Rate of Vitreous Cutter Probes

PURPOSEnWe report on instantaneous volumetric flow rate of vitreous cutters measured by means of particle image velocimetry (PIV).nnnMETHODSnIn an in vitro experimental study, vitreous cutters mounting a regular blade (RB) or modified Twedge blade (TB) engineered for higher flow were connected to a console machine equipped with a double peristaltic and Venturi pump, and immersed in balanced salt solution (BSS). Instantaneous flow was measured on aspiration tubing sections proximal to the cutter hand piece. Measures settings were as follows: (1) regular functioning at 3000 and 6000 cuts per minute (cpm) with 300 mm Hg aspiration with both pumps, (2) aspiration tubing clamped proximal to pump cassette, and (3) aspiration tubing clamped proximal to hand piece, and (4) flow fluctuation as a function of cut rate also was calculated. For main outcome measures, instantaneous volumetric flow rate in mL/min and flow fluctuation measured as the standard deviation of flow rate were measured.nnnRESULTSnRegular functioning shows sinusoidal flow oscillating at cut rate frequency, with amplitude between ±50 mL/min at 3000 cpm and ±35 mL/min at 6000 cpm. The TB always determined a bimodal wave and neither blade nor pump type influenced the sinusoidal pattern of flow. Clamping aspiration tubing zeroes flow, but does not influence fluctuation frequency or amplitude. Clamping at the hand piece determined a significantly higher oscillation. Oscillation amplitude retain a typical resonance pattern with significant changes in function of cut rate and resonance occurs at approximately 4000 cpm.nnnCONCLUSIONSnCutter blade action determines instantaneous flow rate fluctuation that interferes significantly with cutter suction and hampers a steady suction through cutter port. In a surgical scenario, this translates into a higher risk of inadvertent retinal entrapment and lower predictability of cutter behavior, especially at frequency approaching resonance.

Histological evaluation of the peri-implant tissues of three human-retrieved Straumann implants

The most frequently-used histological parameters to define dental implant osseointegration include bone-to-implant contact and quantitative and qualitative assessments of the surrounding tissue (rate of mineralized/non-mineralized tissue and proportion of lamellar and woven bone compared to soft tissue or bone marrow). The aim of this paper was to present the histological features of the bone tissue surrounding three well-functioning Straumann SLA and SLActive implants placed in two patients after 12 and 60u2003months of loading. The percentage of osseointegration ranged from 66.4% and 71.9% for SLA surfaces, to 88.3% for the SLActive implant. Such results confirm that osseointegration occurs with high rates of bone-to-implant contact in humans, and that implants can be similarly clinically successful, although they show different bone-to-implant contact values.

Fibrous Dysplasia of the Mandibular Arc,Implant-Prosthetic Rehabilitation after Resectionand Reconstruction with Iliac Autogenous BoneGraft: A Case Report

The reconstruction of maxillo-mandibular defects following resection for tumors with autogenous bone grafts has been demonstrated to be a reliable technique with good long-term results. Implants placed in the reconstructed areas were demonstrated to integrate normally, with success and survival rates comparable to those obtained with implants placed in native bone. The authors present an explicative case of this type of surgical and prosthetic rehabilitation.

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

PurposeTo study the efficacy of a novel device intended to control infusion pressure based on mean ocular perfusion pressure (MOPP) during pars plana vitrectomy (PPV).MethodsAn 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 30xa0mmHg in the Control ON group (18 patients), while no action was taken in the Control OFF group (18 patients).ResultsBaseline IOP and blood pressure were similar between groups. The Control ON group had significantly lower average intraoperative IOP (30.5xa0±xa02.1 vs. 35.9xa0±xa06.9xa0mmHg; pxa0=xa00.002) and higher MOPP (56.4xa0±xa05.9 vs. 49.7xa0±xa06.1xa0mmHg) than the Control OFF group. The Control ON group also spent less time at MOPP <xa010xa0mmHg and <xa030xa0mmHg: 0 vs. 3.40xa0±xa02.38xa0min (pxa0<xa00.001) and 9.91xa0±xa07.15 vs. 16.13xa0±xa08.12xa0min (pxa0=xa00.02), respectively.ConclusionsThe 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 <xa010 and <xa030xa0mmHg.

AXIAL ROTATION VITRECTOMY: Back to the Future? the Fluidics of a Prototype Vitreous Cutter Probe.

Purpose: To characterize the fluidics of axial rotating vitreous cutter probe (RT) compared with the standard guillotine (regular blade), when tested in Balanced Salt Solution (Alcon Laboratories, Forth Worth, TX). Methods: RT and regular blade (RB) cutter probes connected to the same vitrectomy console used a peristaltic pump. The authors measured instantaneous flow through aspiration tubing proximal to the handpiece, fluid velocity, and acceleration at the port by means of particle image velocimetry. Results: Average flow at aspiration tubing of RT and RB did not vary significantly. Regular blade probes produced higher instantaneous flow fluctuation than RT at any considered cut rate (RB 1,600 6.4 ± 5.3 mL/minute; RB 3,000 11.8 ± 6.3 mL/minute; RT 1,600 0.9 ± 0.7 mL/minute, and RT 3,000 1.8 ± 0.8 mL/minute, respectively. P < 0.001 in all cases). Regular blade also yield significantly higher fluid velocity at cutter port compared with RT (RB 1,600 85.8 ± 70.1 mm/second; RB 3,000 81.6 ± 66.4 mm/second; RT 1,600 71.9 ± 40.3 mm/second; and RT 3,000 32.9 ± 20.8 mm/second. P < 0.001 in all cases). Fluid acceleration at the cutter port was higher when the RB was used (RB 1,600 26.85 ± 30.18 mm/second2; RB 3,000 33.76 ± 34.09 mm/second2; RT 1,600 24.01 ± 21.94 mm/second2; and RT 3,000 16.62 ± 17.87 mm/second2. P < 0.001 in all cases). Conclusion: RT blade design causes less instantaneous flow fluctuation within the aspiration tubing, and also lower fluid velocity and lower acceleration at the cutter port. Fluidics suggests a safer cutting action and a reduced risk of retinal incarceration.