A new microwave applicator for laparoscopic and robotic liver resection.

PURPOSE: Bleeding from parenchyma transection during a robotic hepatic surgery remains the most critical point affecting postoperative recovery and long-term survival. Various robotic devices with different types of energies have been proposed; however, each of these lack in steerability, efficacy, or accuracy. The aim of this work is to evaluate the feasibility and performance of a new steerable microwave resection device intended for minimizing intraoperative blood loss during laparoscopic and robotic liver resections. METHODS: The new device operating at 2.45 GHz was designed to accommodate the engineering constraints derived from its use for robotic surgery or laparoscopy, in which a steerable head is required and the internal cooling of forced gas or water is undesirable. The device design, analysis, and optimization were addressed using the most advanced commercial electromagnetic and thermal solvers to achieve the best results. To experimentally validate the results of the numerical analysis, many ablations were performed on a freshly explanted bovine liver by using a single device prototype with three levels of energy supplied to the tissue. During the ablation procedures, the time, temperature, and shape of the thermal lesion were recorded using thermocouples and an infra-red thermos camera. SUMMARY: Ex vivo tests showed good agreement with the numerical simulations, demonstrating the validity of the simplifications adopted to deal with the complex phenomena involved in the extreme hyperthermia of a living tissue. The high performance, thermal reliability, and robustness of the developed device were also demonstrated along with the possibility of reducing operation time and blood loss.

Investigating the ocular temperature rise during femtosecond laser lens fragmentation: an in vitro study.

PURPOSE: To investigate the trend of temperature variation during lens fragmentation simulated by a femtosecond laser on an in vitro eye model. METHODS: In our experimental study, a convex cylinder of gelatinous material, usually employed in femtosecond laser calibration, was used to simulate both an anterior segment and a crystalline lens during fragmentation performed with the Victus femtosecond laser (Technolas Perfect Vision GmbH, Germany; Bausch + Lomb Incorporated, USA). Two radiated energies (7000 nJ and 9000 nJ) and three cutting patterns (crosses, circles and cross + circle) were applied. Trends of temperature variation as a function of time were obtained using a T-type thermocouple. RESULTS: The maximum value of temperature rise during lens fragmentation ranged from 3.53 to 5.13 °C; the rise was directly proportional to the intensity of the radiated energy (7000 nJ or 9000 nJ) and the cutting pattern performed. This behavior was experimentally represented by an asymmetric function with a characteristic bell curve shape, whereas it was mathematically described by a transport diffusive model. CONCLUSIONS: Since the temperature rise at the fragmentation volume base resulted to be around 5 °C in our in vitro study, lens fragmentation performed using the Victus femtosecond laser might be considered safe form a thermal point of view.

A new autocentering hinged external fixator of the elbow: a device that stabilizes the elbow axis without use of the articular pin.

BACKGROUND: Hinged external fixation of the elbow is an important tool for the orthopedic surgeon. It enables early postoperative mobilization that may result in better outcomes. All models require correct alignment with the elbow axis of rotation. There is a long learning curve to this procedure, it may be time-consuming, and it can be associated with a high dose of x-ray exposure. An axial pin can interfere with bone-ligament suture anchors and bone reconstruction plates. MATERIALS AND METHODS: A new external fixator has been designed and mechanically tested. The hinge has a special gear able to freely align itself with the center of elbow rotation during passive flexion-extension movements. It has been clinically tested on 7 patients affected by traumatic and post-traumatic elbow disorders. The maintenance of the correct position has been tested clinically with computed tomography scans and radiographs. RESULTS: All patients had correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation. No cases of misalignment, loss of fixation, pin loosening, or instability were found. CONCLUSION: A new self-centering hinged external fixator correctly aligns itself with the axis of elbow rotation. It does not interfere with ligamentous reconstruction anchors, distal plates, or screw fixation. The surgical technique is easy to learn and relatively quick. It can also be positioned without performing an arthrotomy to maintain reduction of simple dislocations of the elbow.

Investigations on the viscoelastic behaviour of a human healthy heel pad: in vivo compression tests and numerical analysis.

The aim of this study was to investigate the viscoelastic behaviour of the human heel pad by comparing the stress-relaxation curves obtained from a compression device used on an in vivo heel pad with those obtained from a three-dimensional computer-based subject-specific heel pad model subjected to external compression. The three-dimensional model was based on the anatomy revealed by magnetic resonance imaging of a 31-year-old healthy female. The calcaneal fat pad tissue was described with a viscohyperelastic model, while a fibre-reinforced hyperelastic model was formulated for the skin. All numerical analyses were performed to interpret the mechanical response of heel tissues, with loading conditions and displacement rate in agreement with experimental tests. The heel tissues showed a non-linear, viscoelastic behaviour described by characteristic hysteretic curves, stress-relaxation and viscous recovery phenomena. The reliability of the investigations was validated by the interpretation of the mechanical response of heel tissues under the application of three pistons with diameter of 15, 20 and 40 mm, at the same displacement rate of about 1.7 mm/s. The maximum and minimum relative errors were found to be less than 0.95 and 0.064, respectively.

Reversible supraventricular tachycardia and left bundle branch block in a marathon runner with exertional heat stroke in the Po Valley.

We report the case of a 52-year-old marathon runner admitted to our emergency department for exertional heat stroke (EHS). The electrocardiogram (ECG) showed a supraventricular tachycardia, probably an atrial flutter with 2:1 block, conducted with left bundle branch block. After 10 minutes of aggressive fluid management and rapid external cooling, the ECG returned to normal. As the high-sensitivity cardiac troponin I was elevated, coronary angiography and an electrophysiological study were performed, revealing normal coronary arteries and excluding inducible arrhythmias. As reported in the current literature, our findings confirm that the electrocardiographic changes and elevation of cardiac markers in EHS do not reflect cardiac ischemia, but rather a myocardial injury due to the pathophysiological response to dehydration and hyperthermia, which markedly impaired stroke volume and cardiac output. EHS is a life-threatening condition with a complex pathophysiology caused by thermoregulatory failure. Diagnosis is not always straightforward, but early recognition and timely management (the "golden hour") with rapid cooling and intravenous fluids are crucial to prevent irreversible and fatal organ damage. EHS is defined by a rectal temperature > 40.5 °C with symptoms or signs of neurological dysfunction, such as confusion, drowsiness, or seizures, which can rapidly worsen with delirium, coma, and cardiac arrest. With this case report, we want to remind emergency physicians that early diagnosis and appropriate management of EHS can avoid death and inappropriate treatment. (www.actabiomedica.it).

Infrared thermographic investigation on the ocular surface temperature of normal subjects.

OBJECTIVE: It is understood that the ability to measure ocular temperature accurately will increase understanding of ocular physiology and should be a support in decision-making in classical diagnostic procedures. The use of ocular thermography offers great opportunities for monitoring the temperature of the anterior eye and analyzing the effects of certain pathologies on ocular surface temperature (OST). The aim of the present work is to measure the OST of 220 healthy normal subjects, stratified according to gender and age, in order to obtain a normal temperature distribution to be used as reference values when comparing healthy versus pathological conditions. APPROACH: The OST is measured from five regions, located over the whole area of the anterior eye, which correspond to particular anatomic structures, through a semi-automated procedure to post-process the infrared images. The relationship between OST and independent variables (forehead skin temperature, age, gender, level of physical activity, cardiovascular risk factors including sedentary lifestyle and smoking, laboratory temperature, and laboratory humidity) was investigated through linear regression models. MAIN RESULTS: The OSTs measured from the five different ocular regions are statistically different (p -value < 0.001), even when dividing our subjects into males and females, with the nasal cantus being the hottest region and the central cornea the coolest; when considering also the effect of age, stratifying our subjects into young, middle-aged and elderly, the OST decreases when age increases significantly. Statistical analysis based on linear regression models pointed out that age, forehead skin temperature, and lab temperature are the main factors to be taken into account when exploring the OST. SIGNIFICANCE: As OST evaluation can be important in detecting different ocular pathologies, having precise details of the variation in temperature across the ocular surface and therefore a more detailed map of the OST adjusted according to subject characteristics and environment conditions could enhance early diagnosis and thus course of treatments.

Biomechanical analysis on total knee replacement patients during gait: Medial pivot or posterior stabilized design?

BACKGROUND: Total Knee Replacement surgery restores joint function in patients with advanced osteoarthritis. There are several prostheses available based on different mechanisms, which guarantee knee stability during Activities of Daily Living. The aim of this study is to compare ball-in-socket (or Medial Pivot) and post-cam mechanisms to detect possible differences in terms of biomechanical parameters between these two prosthesis designs and to evaluate which design is closer to physiological biomechanics. METHODS: A kinematics, kinetics and electromyography lower limb analyses were performed during gait on sixty subjects: twenty with Medial Pivot prosthesis, twenty with posterior stabilized prosthesis and twenty healthy subjects to obtain a physiologic reference. FINDINGS: Total Knee Replacement gait pattern for both patient groups were characterized by reduced walking speed, reduced stride length and increased stance time respect to control group. Comparison between Medial Pivot and Posterior Stabilized groups showed a reduction of knee flexion and flexor moment in patients with ball-in-socket mechanism. A prolonged muscular activity of rectus femoris was observed in Medial Pivot patients compared to Posterior Stabilized and control groups. INTERPRETATION: "Stiff knee pattern" mechanism was showed for both patient groups but more enhanced in Medial Pivot patients. Even though the Posterior Stabilized design introduces the non-physiological paradoxical motion and the Medial Pivot design seems to better reproduce the physiological condylar movement as gait analysis parameters, including kinematics, kinetics and electromyographic parameters were closer to control group and, in turn, to physiological gait for the Posterior Stabilized than Medial Pivot group parameters.

Design and realization of a normothermic perfusion system for laboratory tests on pig liver.

Ex vivo testing is a fundamental step in the development of new medical devices; indeed without it, it is impossible to proceed with in vivo tests. At the University of Florence, a robotic tool for microwave thermal ablation is under development. Up to now, the thermoablation tests for the validation of the tool were carried out on non-perfused ex vivo livers, providing results that inevitably differ from those obtainable with an in vivo liver. The aim is to design, and consequently create, a compact and transportable system which allows to perfuse a swine liver with physiological solution and heparin. This device should also allow the organ to be transported from the explantation place to the laboratory, keeping it under normothermal condition. The perfusor was designed to simulate the physiological flow within the liver in the most realistic way possible. The design, construction, and optimization of the perfusor have been addressed using the physiological values of hepatic flow and pressure identified in the literature, neglecting in the first instance any load losses. Therefore, open circuit tests were conducted, validated through perfusion tests on freshly explanted pig liver; during these tests, the surface temperature of the organ was recorded using an infrared camera, and the fluid temperature was verified using an immersion probe. The perfusion test showed a good alignment with the open circuit tests, demonstrating the validity of the simplifications adopted to treat the complex vascular structure of the liver.

Response of serum proteome in patients undergoing infrarenal aortic aneurysm repair.

BACKGROUND: Postoperative organ dysfunction in conventional surgery for abdominal aortic aneurysm (AAA) is associated with a complex inflammatory reaction, with activation of coagulation and fibrinolysis. A prospective,observational study was performed to define the complex plasma proteomic changes after AAA repair and to identify factor(s) that may affect myocardial function in uncomplicated procedures. METHODS: Ten patients undergoing infrarenal AAA repair were investigated. Eight subjects subjected to major abdominal surgery served as controls. Hemodynamic changes were continuously monitored by using the pressure recording analytical method technique. The time course of plasma proteins was investigated after induction of anesthesia and at different times after surgery (6 h, 12 h, 24 h, 36 h) by using two-dimensional difference gel electrophoresis, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and Western blot. The effects of plasma on the functional properties of isolated rat ventricular myocytes were also investigated. RESULTS: In AAA patients alone, 18 spots were found to change more than two-fold in expression level, spot identification revealing an increased thrombin generation 6 h after surgery. At the same time cardiac cycle efficiency significantly reduced versus baseline (-0.5 +/- 0.9 vs. 0.18 +/- 0.3 in AAA patients, P < 0.01; 0.4 +/- 0.1 vs. 0.2 +/- 0.3 in control surgery, not significant; P < 0.01 group x time interaction at ANOVA). Plasma obtained 6 h after AAA surgery dose-dependently inhibited contractile function of control rat myocytes (percent shortening fell by 51% with 10% of AAA plasma and was abolished with 20% of AAA plasma, P < 0.001 for both). The inhibitory response was abolished by thrombin antagonism. CONCLUSIONS: These findings show for the first time the possible role of thrombin generation within the complex activation of inflammatory response in causing hemodynamic instability in the early postoperative period after AAA surgery.

Ocular surface temperature in diabetic retinopathy: a pilot study by infrared thermography.

PURPOSE: To compare ocular surface temperature (OST) measures in patients with nonproliferative diabetic retinopathy (NPDR) and healthy controls. METHODS: A total of 51 consecutive patients with different severity degrees of NPDR and 53 age- and gender-matched healthy volunteers were recruited. OST was evaluated by infrared thermography in five conjunctival (points 1, 2, 4, 5) and corneal (point 3) points. RESULTS: In diabetic eyes, OST values were lower than in controls at all the studied points (p<0.001 at points 1, 2, 3, 4, and p=0.003 at point 5). CONCLUSIONS: Ocular surface temperature measurements, by estimating ocular blood flow, may be helpful in the management of patients with diabetic retinopathy.

A novel image processing procedure for thermographic image analysis.

The imaging procedure shown in this paper has been developed for processing thermographic images, measuring the ocular surface temperature (OST) and visualizing the ocular thermal maps in a fast, reliable, and reproducible way. The strength of this new method is that the measured OSTs do not depend on the ocular geometry; hence, it is possible to compare the ocular profiles belonging to the same subject (right and left eye) as well as to different populations. In this paper, the developed procedure is applied on two subjects' eyes: a healthy case and another affected by an ocular malignant lesion. However, the method has already been tested on a bigger group of subjects for clinical purpose. For demonstrating the potentiality of this method, both intra- and inter-examiner repeatability were investigated in terms of coefficients of repeatability (COR). All OST indices showed repeatability with small intra-examiner (%COR 0.06-0.80) and inter-examiner variability (%COR 0.03-0.94). Measured OSTs and thermal maps clearly showed the clinical condition of the eyes investigated. The subject with no ocular pathology had no significant difference (P value = 0.25) between the OSTs of the right and left eye. On the contrary, the eye affected by a malignant lesion was significantly warmer (P value < 0.0001) than the contralateral, where the lesion was located. This new procedure demonstrated its reliability; it is featured by simplicity, immediacy, modularity, and genericity. The latter point is extremely precious as thermography has been used, in the last decades, in different clinical applications. Graphical abstract Ocular thermography and normalization process.

Unassisted quiet standing and walking after crutch usage in patients with total hip replacements: Does crutch length matter?

BACKGROUND: Crutch use is prescribed early in the rehabilitation process following total hip replacement (THR) surgery to improve safety and promote return to active living. RESEARCH QUESTION: Purpose of this study was to understand mid-term effects of crutch length setup on quiet standing and walking two months post-op when crutch use was no longer required. METHODS: Thirty patients were evaluated 2 months post-surgery when they had been walking without crutch for a month. The patients had previously been assigned randomly to elbow flexed (EF) or elbow extended (EE) crutch set-ups and evaluated 3 days post-surgery. Quiet standing stability was assessed with participants standing in a comfortable position with each foot on separated force platforms, facing forward for 10 s. In addition, participants walked on the laboratory path, instrumented with motion tracking system and force platforms. For the quiet standing trial, centre of pressure measure, acromial height and lower limbs load bearing symmetry were evaluated. For the walking trial, spatiotemporal and ground reaction force (GRF) parameters were evaluated together with side symmetry indices. RESULTS: Results showed no significant differences in any standing trial variables between groups. For walking, GRF parameters and symmetry indices were similar for both groups. However, increased base of support width, reduced self-selected walking speed and stride length were found for the EF group. SIGNIFICANCE: This study showed that crutch set-up influenced gait after patients started to walk unassisted. Patients that previously used crutch adjusted according to the EE setup, demonstrated a more efficient gait with higher self-selected speed and longer and narrower stride. Clinicians may use these results for a proper crutch height adjustment, which improves walking and, in turn, functional recovery in post THR patients.

The influence of the crutch setup on stability and weight-bearing parameters in post total hip replacement surgery patients during quiet standing.

PURPOSE: The purpose of this study is to evaluate the influence of the crutch setup on standing, in post total hip replacement (THR) surgery patients. MATERIALS AND METHODS: Thirty patients after THR were randomly assigned to walking with the elbow flexed (EF) or elbow straight (ES) crutch setup. Subjects were asked to stand on a force platform in a comfortable position with the crutch positioned on the unaffected side, facing forward for 10 seconds. Centre of pressure total path and maximal excursion were evaluated in both medio-lateral and anterior-posterior planes. Difference in the asymmetry of left/right acromial height, measured with and without the crutch, was calculated (ACdiff). Percentage of body weight borne by the crutch (Fcr), symmetry (SIload) between operated and healthy limbs loading during the trial, together with shoulder forces and moments were measured. RESULTS: No significant differences between the two groups (p > .05) were found for stability parameters. ACdiff, Fcr and shoulder load increased significantly (p < .05) in EF group compared to ES group. In addition leg loading symmetry was significantly reduced in the EF group. CONCLUSIONS: The present study showed that the ES setup reduced the force borne by the crutch, the load on the shoulder joint and it minimized postural and loading asymmetries when compared to EF setup. Conversely, postural stability was not influenced by the crutch setup. Implications for Rehabilitation Static posture and weight-bearing parameters are influenced by crutch setup during quiet standing. Crutch setup does not influence postural stability. Adjusting the crutch according to the elbow straight setup reduces the force borne by the crutch and the asymmetry in lower limbs loading. Forces and moments at the shoulder joint were reduced for the elbow straight setup group.

Does crutch length influence gait parameters after total hip replacement surgery?

After total hip replacement surgery, crutches are often prescribed to enable patients to walk independently. Purpose of this study was to evaluate possible crutch length influence on gait performance and symmetry, including spatiotemporal and kinetics parameters. Thirty patients were randomly assigned to elbow flexed (EF) or elbow extended (EE) crutch setup. Subjects were asked to walk on the laboratory path, instrumented with motion tracking system and force platforms. Spatiotemporal gait parameters and ground reaction force (GRF) parameters for both limbs and crutch support were evaluated. In addition, limb symmetry was evaluated for both gait and force parameters using the symmetry index. Variability was quantified for base of support width, stride time and length as the coefficient of variation. Results showed that cadence and walking speed were not significantly different, but stride length significantly decreased and base of support width increased for the EF group when compared to the EE group. Operated limb GRF parameters were significantly decreased for the EF group, while crutch force parameters decreased for the EE group. Furthermore, the EF group showed greater stride length variability and asymmetry of force and spatiotemporal parameters than EE group did. The results of the present study showed that EF and EE setups did not assist patients equally during walking, with EE setup allowing more load bearing on the operated side, reducing load on the crutch and asymmetries in gait parameters when compared to the EF setup. This may help clinicians in rationalizing crutch setup for patients after total hip replacement surgery.

Experimental measurement of forces during percutaneous dilatational tracheostomy.

The measurement of mechanical effects associated with the dilatation phase of a percutaneous dilatational tracheostomy is of primary importance to identify the causes of major complications associated with this procedure, such as tracheal cartilage subluxation or fracture and bleeding. Such information can be very useful also for the design of better instruments and procedures. The aim of this study was to present a methodology to evaluate mechanical effects of the dilatation phase of a percutaneous dilatational tracheostomy on the tracheal rings and adjacent anatomical structures. Forces and moments were measured through a dilator instrumented with strain gauges. Two surgeons, with different levels of expertise, performed the percutaneous dilatational tracheostomy on a lifelike reproduction of an adult head, specifically designed for training professionals. The modified dilator was effective in measuring forces involved in the percutaneous dilatational tracheostomy without affecting the ability of the operator to perform the procedure. The main contribution to the insertion of the dilator was given by the axial force, defined as the force acting on the handle, compressing it (mean and peak force: 48.8 and 88.2 N for Surgeon 1, 31.3 and 82.8 N for Surgeon 2, respectively). The proposed method was effective in measuring differences between procedures performed by surgeons with different amounts of experience in terms of duration, forces applied and repeatability. In addition, it may have applications for use as a feedback for incorrect positioning or excessively variable pressure during the training of surgeons for the execution of percutaneous dilatational tracheostomy.

Shoulder joint loadings in post total hip replacement surgery patients during assisted walking: The influence of the crutch setup.

A crutch is prescribed to permit the patient to walk safely and independently immediately after total hip replacement (THR) surgery. Purpose of this study is to evaluate the influence of the crutch setup on upper limbs biomechanics, including shoulder joint kinematics and kinetics parameters that will be evaluated to detect possible differences related to the crutch length. Thirty patients were randomly assigned to elbow flexed (EF) or elbow extended (EE) forearm crutch setup. Subjects were asked to walk on the laboratory path, instrumented with motion tracking system and force platforms. Spatiotemporal gait parameters, crutch ground reaction force (GRF) and crutch displacement (measured as the relative distance between the crutch position on the floor and the shoulder joint center), were evaluated. A three-dimensional (3D) biomechanical model was implemented to determine shoulder joint kinematics and kinetics during crutch walking. Results showed that the stride length significantly decreased, and base of support width increased for the EF group when compared to the EE group. Crutch forces and distance to the body significantly decreased in the EE group. Furthermore, shoulder joint moments in all planes of motion, vertical and lateral forces were significantly reduced in the EE group. The present study showed that crutch setup influenced performance and upper limb loading during walking, with EE setup allowing a more stable walking and reducing stress on the shoulder joint when compared to the EF setup. Results may help therapists in rationalizing crutch length adjustments for patients after THR surgery.

Evaluation of ocular surface temperature and retrobulbar haemodynamics by infrared thermography and colour Doppler imaging in patients with glaucoma.

BACKGROUND: Ocular surface temperature (OST) could berelated to retrobulbar haemodynamics in patients with glaucoma. AIMS: To compare OST measurements in patients with glaucoma and healthy controls, and to investigate the correlation between OST, intraocular pressure (IOP) and retrobulbar haemodynamics in patients with glaucoma. METHODS: 32 patients with primary open-angle glaucoma (POAG) and 40 controls were included in the study. The parameters considered both in patients with POAG and in controls were IOP and OST values measured by infrared ocular thermography. Colour Doppler imaging was used to determine haemodynamic parameters in ophthalmic artery (OA), central retinal artery (CRA) and short posterior ciliary arteries (SPCAs) in patients with POAG. RESULTS: OST values were significantly lower in patients with POAG than in controls (p<0.001). OST was negatively related with resistivity index of OA (p<0.001), CRA (p = 0.001) and SPCAs (p<0.001), and positively related with end-diastolic velocity of OA (p = 0.02) and SPCAs (p = 0.05). CONCLUSION: This study suggested that OST could be a marker of impaired retrobulbar haemodynamics in patients with glaucoma.

Thermography used for analysis and comparison of different cataract surgery procedures based on phacoemulsification.

Thermography has been employed to analyze and compare three cataract surgery procedures performed in vivo with phacoemulsification, namely, the Sovereign phacoemulsification system with a traditional technique, the Sovereign WhiteStar phacoemulsification system with a traditional technique and the Sovereign WhiteStar phacoemulsification system with a bimanual technique. During the entire surgical procedure, the temperature of the ocular surface was monitored. The temperature values in the area where the phaco probe was inserted in the eye were measured, and the quantities of heat transmitted to the eye in the different procedures were assessed through suitable indices. In this study the highest temperature measured for each procedure during the surgical operation was 44.9 degrees C for the Sovereign phacoemulsification system with a traditional technique, 41 degrees C for the Sovereign WhiteStar phacoemulsification system with a traditional technique and 39.5 degrees C for the Sovereign WhiteStar phacoemulsification system with a bimanual technique, which is also the surgical procedure having the lowest thermal impact on the eye, i.e., the one in which the temperature peaks are lowest in amplitude and the least amount of heat is transmitted to the eye. Thermography, used in this study as a temperature monitoring instrument, has allowed analysis to be effected through a useful and advantageous methodology, totally non-invasive as regards both surgeon and patient, and has been applied in vivo without requiring any change in the surgical procedure.

Investigation into the elastic properties of ex vivo porcine corneas subjected to inflation test after cross-linking treatment.

BACKGROUND: The aim of this work was to evaluate the effect of cross-linking (CXL) on ex vivo porcine corneal elastic properties, using an inflation procedure. METHODS: Twelve corneas were subjected to standard CXL (370 nm, 3 mW/cm2, 30 minutes), while 12 were used as controls. Corneal thickness was measured by Visante optical coherence tomography, before and immediately after treatment, and before inflation test. Both intraocular pressure and radial apical cornea displacement were measured during inflation. Stress-strain curves were obtained by applying the linear shell theory. The elastic modulus was evaluated by calculating the slope of the stress-strain curves. RESULTS: Results showed a statistically significant increase in elastic modulus (p<0.0001), with a mean of 3,868 ± 502 kPa for cross-linked corneas and 2,727 ± 238 kPa for untreated corneas, when subjected to high pressure (40-60 kPa). CXL significantly increased porcine cornea stiffness by about 42%. Findings did not show any significant difference within the physiological range of pressure (2-4 kPa). CONCLUSIONS: The inflation test has been proven to be a valuable tool for the investigation of corneal biomechanics, maintaining both integrity and geometry of corneal tissue.

In vivo thermographic analysis of the corneal surface in keratoconic patients undergoing riboflavin-UV-A accelerated cross-linking.

PURPOSE: To assess corneal thermal profile during combined riboflavin and accelerated UV corneal collagen cross-linking (A-CXL) using in vivo surface thermographic analysis. METHODS: In this open-label, nonrandomized, prospective pilot study, 28 eyes of 28 patients were included. The study was conduced at the Department of Surgery and Translational Medicine, University of Florence, Italy, in collaboration with the Ophthalmic Operative Unit of Siena University, Italy. All patients underwent high-fluence A-CXL in pulsed light and continuous light UV-A exposure at 30 and 18 mW/cm. Patients were divided into 4 groups: 7 for continuous light A-CXL, 7 for pulsed light A-CXL at 30 mW/cm with 7.2 J energy, 7 for continuous light A-CXL, and 7 for pulsed light A-CXL at 18 mW/cm with 5.4 J energy. Corneal surface temperature measurements were recorded using an infrared FLIR thermocamera (FLIR 320A; FLIR Systems). Corneal temperature values were detected in the surface area exposed to UV-A light irradiation, selecting it in the acquired thermographic image. The maximum temperature value detected in the area studied was recorded and considered for comparative analysis. RESULTS: Infrared thermocamera measurements of the corneal surface during A-CXL treatments showed an average temperature of 31.5°C during the entire procedure in all groups and UV-A powers (30 mW/cm at 7.2 J/cm and 18 mW/cm at 5.4 J/cm) and light exposure modality remained under the threshold of collagen thermal injury. CONCLUSIONS: Accelerated corneal collagen cross-linking did not cause thermal rise over the threshold of thermal injury to the corneal surface, demonstrating a safe thermal profile both at 30 mW/cm with 7.2 J and 18 mW/cm with 5.4 J energy dose.