Biomedical subjects

A Eklund

Publications and source records attributed to A Eklund.

At least 19 recordsLinked to original sources

PubMed2007

CSF pressure assessed by lumbar puncture agrees with intracranial pressure.

The accuracy of estimating intracranial pressure in brain tissue (ICP(BT)) via lumbar space was investigated using preset pressure levels in the interval 0 to 600 mm H(2)O in patients with communicating hydrocephalus. Lumbar space ICP correlated excellently to ICP(BT), demonstrated by a measured mean difference of 10 mm H(2)O (0.75 mm Hg) and a regression coefficient of 0.98. The concurrence supports the lumbar puncture as an accurate technique to determine ICP in patients with communicating CSF systems.

Aged↗

PubMed2006

Altered apoptosis in bronchoalveolar lavage lymphocytes after allergen exposure of atopic asthmatic subjects.

The increased number of lymphocytes in airways during an asthmatic response is believed to be the result of increased recruitment of these cells. However, it is possible that a decreased apoptotic rate could also contribute to the increased number. The aim of the present study was to investigate whether allergen airway provocation influences the apoptotic phenotype of lung and peripheral blood lymphocytes (PBL) in subjects with atopic asthma. Bronchoalveolar lavage (BAL) lymphocytes and PBL from 12 asthmatic subjects previously challenged with allergen (n = 7) or saline (n = 5) were exposed to the apoptotic stimulus tributyltin (TBT) in vitro and assayed for apoptosis. Airway allergen provocation resulted in decreased sensitivity of BAL lymphocytes to TBT-induced apoptosis, with 42.2% (range 33.9-62.5%) apoptotic cells before challenge versus 23.5% (range 15.3-42.4%) after challenge, while PBL were unaffected. The increased apoptosis resistance correlated with higher numbers of Bcl-2-expressing lymphocytes. Interestingly, baseline caspase-3-like activity was significantly elevated in viable BAL lymphocytes compared with viable PBL, and was unaltered by allergen exposure. In conclusion, allergen inhalation renders bronchoalveolar lavage lymphocytes more resistant to apoptosis while peripheral blood lymphocytes were not influenced at all, indicating that the apoptotic phenotype of airway lymphocytes may play a role in asthmatic inflammation.

Adult↗

PubMed2006

Randomized clinical trial of Lichtenstein patch or Prolene Hernia System for inguinal hernia repair.

BACKGROUND: In this randomized prospective study the short- and long-term outcomes of patients undergoing inguinal hernia repair with either Lichtenstein mesh or the Prolene Hernia System (PHS) were evaluated. METHODS: Postoperative pain and time to return to work, driving and sporting hobbies were recorded after 300 inguinal hernia repairs done by one of the two methods. Long-term sequelae and complications were assessed at follow-up visits 1 week, 1 month and 1 year after the operation. RESULTS: The median duration of operation for unilateral primary hernia was 37 min for the Lichtenstein operation and 27 min for the PHS procedure (P < 0.001). Postoperative pain was similar after both operations. Median sick leave was 7 days in both groups. Time to driving a car was 4 versus 3 days, and time to return to sporting hobbies 13 versus 11 days, in the Lichtenstein and PHS groups, respectively. Apart from a residual femoral hernia after Lichtenstein repair, no recurrent inguinal hernias were detected. CONCLUSION: Both Lichtenstein and PHS methods resulted in rapid recovery and low recurrence rates. The PHS operation was significantly quicker.

Adult↗

PubMed2006

Short-term results of a randomized clinical trial comparing Lichtenstein open repair with totally extraperitoneal laparoscopic inguinal hernia repair.

BACKGROUND: Laparoscopic herniorrhaphy has emerged as a recognized operative method for inguinal hernia repair. This study compared the short-term results of two tension-free methods of repair: totally extraperitoneal (TEP) laparoscopic patch repair and the open Lichtenstein mesh technique. METHODS: A total of 1513 men from 11 hospitals who presented with a primary unilateral inguinal hernia were randomized to one of the two methods. Operating time, short-term complications, reoperations, postoperative pain, consumption of analgesics, sick leave and time to resumption of normal physical activities were recorded. RESULTS: Some 1371 of the 1513 men underwent surgery, 665 in the TEP group and 706 in the Lichtenstein group. The median duration of operation was 55 min for both procedures and 91.0 percent of the patients in both groups were discharged on the day of operation. Patients in the TEP group experienced less postoperative pain (P<0.001), consumed fewer analgesics (P<0.001), had a shorter period of sick leave (7 versus 12 days; P<0.001) and a shorter time to resumption of normal physical activity (20 versus 31 days; P<0.001). CONCLUSION: The TEP technique took no longer to perform, and was associated with less postoperative pain, a shorter period of sick leave and a faster recovery, compared with open Lichtenstein hernia repair.

Adult↗

PubMed2006

Changes in immune regulation in response to examination stress in atopic and healthy individuals.

BACKGROUND: Stress can aggravate the allergic inflammation, but determinants of disturbed immune regulation are largely unknown. OBJECTIVE: To determine systemic immunological, local inflammatory and functional airway responses to stress in healthy and atopic individuals. METHODS: Forty-one undergraduate students, 22 with allergy of whom 16 had asthma, and 19 healthy controls, were studied in a low-stress period and in association with a large exam. Subjects completed questionnaires on stress and health behaviours, underwent lung function tests, bronchial methacholine challenge, measurements of exhaled nitric oxide and urine cortisol. Blood cells were phenotyped, and cytokines from mononuclear blood cells were analysed. RESULTS: Perceived stress and anxiety increased in both groups during the exam period while cortisol increased only in the atopy group. Cytokine production decreased broadly in response to stress in both groups, which was paralleled by an increase in the proportion of regulatory T cells (CD4(+)CD45RO(+)CD25(bright)). Interestingly, atopic individuals, but not controls, reacted with a decreased T-helper type 1/T-helper type 2 (Th1/Th2) ratio and a decrease in natural killer (NK) cell numbers in response to stress. In control subjects only, exhaled nitric oxide decreased and forced expiratory volume in one second increased during stress. CONCLUSION: Atopic and non-atopic subjects shared some immune changes in response to stress, such as a dramatic decline in cytokines and an increase in the number of regulatory T cells in peripheral blood. However, other stress-induced immune changes were unique to atopic individuals, such as a skewed Th1/Th2 ratio and reduced NK cell numbers, indicating that some pathogenic mechanisms in atopics may be more strongly affected by stress than others.

Adult↗

PubMed2006

Reduced Th1 response in the lungs of HLA-DRB1*0301 patients with pulmonary sarcoidosis.

To investigate why human leukocyte-associated antigen-DRB1*0301 (HLA-DRB1*0301) positive Scandinavian patients have a better prognosis than HLA-DRB1*0301 negative patients, the present authors examined patterns of cytokine expression in bronchoalveolar lavage (BAL) cells and BAL fluid (BALF) from patients with pulmonary sarcoidosis and controls. Using real-time PCR, the mRNA expression of selected cytokines in BAL cells from newly diagnosed, untreated nonsmoking patients (n=25) and controls (n=11) was quantified. Cytokine protein levels in BALF from patients (n=34) and controls (n=11) were assessed using cytometric bead array. The patients were evaluated and stratified into two subgroups: HLA-DRB1*0301 positive (all with an acute onset) and HLA-DRB1*0301 negative (all with an insidious onset). When comparing patients and controls, BAL cells of the patients expressed significantly higher levels of interferon (IFN)-gamma and interleukin (IL)-10 mRNA. There were significantly decreased IFN-gamma and tumour necrosis factor (TNF)-alpha mRNA levels, and a tendency toward higher levels of transforming growth factor-beta1 mRNA in HLA-DRB1*0301 positive compared with HLA-DRB1*0301 negative patients. Protein levels of IL-1beta, IL-2, IL-6, IL-12p70 and TNF-alpha in BALF were significantly higher in patients. HLA-DRB1*0301 positive patients exhibited tendencies to lower levels of most cytokines in BALF. In conclusion, the present data show a reduced expression of T-helper cell type-1 cytokines in human leukocyte-associated antigen-DRB1*0301 positive patients, which may relate to their good prognosis.

Adult↗

PubMed2005

Phenotypic analysis of alveolar macrophages and lymphocytes following allergen inhalation by atopic subjects with mild asthma.

BACKGROUND: The airway inflammation associated with allergic asthma is initiated through a complex interaction of antigen-presenting cells (APC) and T lymphocytes resulting in the release of a cascade of cytokines regulating the progress of the allergic inflammatory response. In the present study the state of alveolar macrophage (AM) and T cell activation was investigated following induction of allergic airway inflammation in individuals with atopic asthma. METHODS: Eleven individuals with mild, atopic asthma received cumulated allergen inhalations. Before and one day after challenge, bronchoalveolar lavage (BAL) was performed, and peripheral blood samples obtained. Ten healthy individuals served as controls. The expression of cell surface markers by BAL fluid AMs and T cells, and by blood T cells, was investigated by flow cytometry. RESULTS: All patients developed early asthmatic reactions (EAR) with increased numbers of eosinophils and mast cells in BAL fluid following allergen challenge. After allergen challenge, patients had relatively fewer pulmonary CD4+ T cells expressing CD69 and HLA class II and also relatively fewer pulmonary CD8+ T cells expressing HLA class II, compared to before challenge. An increased quantitative expression of CD14 and CD86 was seen within the AM population following allergen challenge. CONCLUSION: The results indicate a recruitment of non-activated, immature macrophages and CD4+ T cells to the airways as well as an altered phenotype pattern within the AM population following induction of allergic airway inflammation by allergen inhalation challenge in asthma.

Adult↗

PubMed2005

Vasodilatory shock in severe acute pancreatitis without sepsis: is there any place for hydrocortisone treatment?

BACKGROUND: Hydrocortisone (HC) has been reported to rapidly improve hemodynamics and reduce the time to vasopressor cessation in septic shock, but none has focused on this effect in acute pancreatitis. We therefore performed a study to assess the effects of hydrocortisone on catecholamine-dependent shock among patients with severe acute pancreatitis. METHODS: A retrospective, case-controlled study among 10 patients with severe acute pancreatitis and HC treatment for catecholamine-dependent shock was performed. The control group comprised 11 conventionally treated patients with the same severity of pancreatitis and circulatory shock according to the norepinephrine support required. In focus were the first 48 h from the start of HC administration in the HC group and from the reference point in the control group, respectively. The reference point for the control group was the time point at which doses of norepinephrine exceeded 0.3 microg kg(-1) min(-1). RESULTS: Patients in the HC group were weaned off norepinephrine in a significantly shorter time (61 h in HC group vs. 141 h, P = 0.016). The HC group received significantly less norepinephrine (area under curve of norepinephrine dose, P = 0.041). The reduction in norepinephrine dose was comparable at 24 h, being -0.051 (-0.208-0.022) microg kg(-1) min(-1) in the HC group vs. -0.026 (-0.150-0.030) microg kg(-1) min(-1) in the controls (P = 0.307), and at 48 h with respective figures of -0.206 (-0.317 to -0.102) microg kg(-1) min(-1) and -0.103 (-0.178-0.029) microg kg(-1) min(-1) (P = 0.072), from the start of HC administration. CONCLUSION: According to our data it seems reasonable to formulate a hypothesis that low doses of HC shorten the time to vasopressor cessation and rapidly reduce the need for norepinephrine support in patients with shock associated with severe acute pancreatitis without sepsis.

Acute Disease↗

PubMed2005

Objective B wave analysis in 55 patients with non-communicating and communicating hydrocephalus.

BACKGROUND: B waves, slow and rhythmic oscillations in intracranial pressure (ICP), are claimed to be one of the best predictors of outcome after surgery for normal pressure hydrocephalus (NPH). OBJECT: To determine the relation between the percentage of B waves and outcome in patients with hydrocephalus, and also the diurnal variation of B waves. METHODS: ICP and patient behaviour were recorded overnight (17 to 26 hours) in 29 patients with non-communicating hydrocephalus and 26 with NPH. The B wave activity, measured with an amplitude threshold of 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, and 5.0 mm Hg, was estimated as the percentage of total monitoring time (% B waves) using a computer algorithm, and correlated with postoperative outcome, defined as changes in 12 standardised symptoms and signs. RESULTS: There was no linear correlation between improvement after surgery in the 55 patients and total % B waves, but a correlation was found between improvement and % B waves during sleep (r = 0.39, p = 0.04). The percentage of B waves was the same during sleep and wakefulness, and patients with NPH had the same proportion of B waves as the non-communicating patients. CONCLUSIONS: B waves are commonly observed in patients with both communicating and non-communicating hydrocephalus, but are only weakly related to the degree of postsurgical improvement.

Adult↗

PubMed2005

Brain energy metabolism and intracranial pressure in idiopathic adult hydrocephalus syndrome.

BACKGROUND: The symptoms in idiopathic adult hydrocephalus syndrome (IAHS) are consistent with pathology involving the periventricular white matter, presumably reflecting ischaemia and CSF hydrodynamic disturbance. OBJECTIVE: To investigate whether a change in intracranial pressure (ICP) can affect energy metabolism in deep white matter. METHODS: A microdialysis catheter, a brain tissue oxygen tension probe, and an ICP transducer were inserted into the periventricular white matter 0-7 mm from the right frontal horn in 10 patients with IAHS. ICP and intracerebral Ptio2 were recorded continuously during lumbar CSF constant pressure infusion test. ICP was raised to pressure levels of 35 and 45 mm Hg for 10 minutes each, after which CSF drainage was undertaken. Microdialysis samples were collected every three minutes and analysed for glucose, lactate, pyruvate, and glutamate. RESULTS: When raising the ICP, a reversible drop in the extracellular concentrations of glucose, lactate, and pyruvate was found. Comparing the values during baseline to values at the highest pressure level, the fall in glucose, lactate, and pyruvate was significant (p < 0.05, Wilcoxon sign rank). There was no change in glutamate or the lactate to pyruvate ratio during ICP elevation. Ptio2 did not decrease during ICP elevation, but was significantly increased following CSF drainage. CONCLUSIONS: Raising intracranial pressure induces an immediate and reversible change in energy metabolism in periventricular white matter, without any sign of ischaemia. Theoretically, frequent ICP peaks (B waves) over a long period could eventually cause persisting axonal disturbance and subsequently the symptoms noted in IAHS.

Aged↗

PubMed2005

Accumulation of eosinophils and T-lymphocytes in the lungs after exposure to pinewood dust.

Exposure to wood dust within the woodworking industry has been shown to cause a variety of respiratory disorders. The aim of this study was to investigate the cellular effects in bronchoalveolar lavage (BAL) fluid and peripheral blood from healthy individuals exposed to pinewood dust. Eleven healthy volunteers were exposed to pinewood dust for 1 h in a whole-body exposure chamber. BAL fluid and blood cells were differentially counted and the expression of activation, adhesion and subset markers on alveolar macrophages and T-lymphocytes was determined 2-6 weeks before and 20 h after the exposure. Following pinewood dust exposure, the total BAL fluid cell concentration increased from 81.4 (64.1-97.5) x 10(6) cells x L(-1) (median (interquartile range)) to 195.3 (154.6-341.2) x 10(6) cells x L(-1). The BAL fluid T-lymphocyte concentration increased from 3.8% (3.5-6.5%) to 7.6% (4.9-11.2%), and BAL fluid eosinophil concentration from 0.0% (0.0-0.2%) to 1.8% (0.6-3.5%). Inhalation of pinewood dust leads to the recruitment of inflammatory cells to the airways of healthy individuals. The increase in numbers of eosinophils, T-lymphocytes and mast cells, i.e. cells of crucial importance to airway inflammation, in the lungs may be related to the increased risk of developing respiratory disorders among woodworkers.

Adult↗

PubMed2005

Characterisation of natural killer cells and CD56+ T-cells in sarcoidosis patients.

The aim of the current study was to investigate the frequency, phenotype and functional activity of natural killer (NK) cells and CD56+ T-cells in the bronchoalveolar lavage fluid and peripheral blood of patients with pulmonary sarcoidosis when compared with healthy volunteers, using staining with a panel of monoclonal antibodies followed by flow cytometry. The results revealed that the majority of the lung NK cell subpopulation expressed CD56(bright). In contrast, there was a predominant CD56(dim) subset in the blood of both patients and healthy controls. Most lung NK cells expressed C-type lectin-like human leukocyte antigen (HLA)-E-specific inhibitory receptor (i.e. CD94/NKG2A), but only a few lung NK cells expressed killer cell immunoglobulin-like inhibitory receptors specific for HLA-A, -B or -C molecules. In addition, a significantly increased number of CD56+ T-cells were observed in the blood of patients when compared with controls. Upon in vitro stimulation, both lung NK and CD56+ T-cells produced considerable amounts of interferon-gamma and tumour necrosis factor-alpha. Thus, in the lungs of patients with pulmonary sarcoidosis, a distinct phenotype of natural killer cells with the capacity to produce cytokines and actively participate in the T-helper 1-like inflammatory response associated with sarcoidosis was identified.

Adult↗

PubMed2005

Bronchoalveolar lavage in COPD: fluid recovery correlates with the degree of emphysema.

Bronchoscopy with bronchoalveolar lavage (BAL) is an important research tool for assessing airway inflammation in a variety of inflammatory lung diseases. In chronic obstructive pulmonary disease (COPD), BAL recovery is often low, making analysis of the recovered fluid difficult to interpret. The present authors hypothesised that the degree of emphysema may predict BAL recovery. A total of 20 COPD patients (mean age 57 yrs, range 49-69) with a median (interquartile range) forced expiratory volume in one second (FEV1) of 51 (33-69)% predicted underwent BAL. Matched "healthy" smokers and nonsmokers served as controls. Emphysema index in COPD patients was calculated on computed tomography scan as the percentage of the right lung with pixels <-950 Hounsfield units. The carbon monoxide diffusing capacity of the lung (DL,CO) was determined by the single-breath method. COPD patients had lower BAL recovery than controls. COPD patients with an emphysema index <1 had higher BAL recovery than patients with an emphysema index >1. BAL recovery correlated negatively to emphysema index and positively to DL,CO. However, no correlation was found between recovery and FEV1. In conclusion, the extent of emphysema evaluated by computed tomography-scan index and carbon monoxide diffusing capacity of the lung may predict a low bronchoalveolar lavage recovery in chronic obstructive pulmonary disease patients. These parameters may, therefore, be useful when chronic obstructive pulmonary disease patients are selected for bronchoscopy with bronchoalveloar lavage. The present study underlines the importance of careful phenotyping of chronic obstructive pulmonary disease patients.

Aged↗

PubMed2004

Infusion technique can be used to distinguish between dysfunction of a hydrocephalus shunt system and a progressive dementia.

In a deteriorating shunted patient with hydrocephalus, an investigation of shunt function is often performed to distinguish a dysfunctioning shunt from an aggravated condition of the disease. The paper illustrates how a lumbar cerebrospinal fluid (CSF) infusion method can be used to evaluate post-operative deterioration in a shunted patient in order to give the physician valuable support in the shunt revision decision. A 77-year-old man with hydrocephalus was treated operatively by the insertion of a CSF shunt. Owing to shunt failure, the shunt was revised twice during a 5 year period. Using a computerised infusion technique method, with two needles placed in the lumbar subarachnoid space, the CSF dynamic system was determined pre- and post-operatively with the functioning as well as the dysfunctioning shunts. The data were verified with a bench-test of the extirpated CSF shunt. There was a significant difference in conductance G between CSF systems with an open shunt and CSF systems with no shunt or an occluded shunt (deltaG= 38 mm3 s(-1) kPa(-1), p = 0.014, n= 7, ANOVA). CSF dynamics investigations, with and without a shunt, can give valuable clinical support in the management of a deteriorating hydrocephalus patient. With further development of the lumbar infusion method moving towards easy-to-use equipment, there is potential for widespread clinical use.

Aged↗

PubMed2004

CSF outflow resistance as predictor of shunt function. A long-term study.

OBJECTIVES: Little is known about the long-term impact of a CSF shunt on the human CSF hydrodynamic system. In patients with communicating hydrocephalus, patency of the shunt system is not regularly assessed. In order to reveal postoperative changes in the CSF hydrodynamic system, we prospectively investigated the features of the system in shunted patients with idiopathic adult hydrocephalus syndrome (IAHS) over a 3-year period. MATERIAL AND METHODS: Thirty-two patients with IAHS were studied at baseline and at 3, 9, 18 and 36 months postoperatively. All patients were operated on with a Hakim standard valve system and a ventriculo-peritoneal approach. At each visit, the patients were investigated with computed tomography/magnetic resonance imaging, video recording of gait and a lumbar constant pressure infusion method. Six brand-new Hakim valves were investigated in a bench test, and these results were compared with the in vivo results. RESULTS: After shunt insertion, the CSF outflow resistance was significantly decreased (13.6 vs 3.8 mmHg/ml/min). The mean outflow resistance of the six in vitro tested valves corresponded to the postoperative values. The variation in resistance in the functioning shunts at different postoperative investigations was negligible. The mean intracranial pressure in the supine position was 13.8 mmHg at the baseline and 14.3, 14.5, 14.8 and 15.7 mmHg at the follow-up visits, respectively. Postoperatively, the CSF pressure after sitting for 10 min (i.e. 'siphoning effect') decreased significantly (mean decrease -5.3, -5.4, -4.7 and -5.3 mmHg at each visit, respectively). Shunt-related complications occurred in seven patients (underdrainage four, overdrainage three). Despite a functioning shunt, eight patients never improved and another nine patients first improved but later deteriorated. CONCLUSIONS: The CSF outflow resistance is much decreased postoperatively and does not alter over time in patients with functioning shunts. We consider CSF outflow resistance to be a reliable indicator of shunt function and of fundamental importance to distinguish a dysfunctioning shunt from an aggravation of the primary condition in patients with communicating hydrocephalus. The unaltered intracranial pressure together with the in vitro model results, suggests that the intra-abdominal pressure might be a major determinant of the postoperative intracranial pressure.

Aged↗

PubMed2004

Features of the Sinushunt and its influence on the cerebrospinal fluid system.

OBJECTIVES: A new cerebrospinal fluid (CSF) shunt system, Sinushunt, has recently been introduced. CSF is shunted from the ventricles to the transverse sinus. The Sinushunt is not a classical differential pressure shunt; instead, it opens as soon as there is a positive pressure over the shunt and the flow is dependent on the resistance of the system, which is high compared with traditional CSF shunts. The objective of this study was to characterise the features of the Sinushunt and to evaluate its influence on the CSF system. METHODS: Five brand new Sinushunts with distal catheters were tested. An automated, computerised experimental apparatus based on regulation of pressure, built into an incubator at 37 degrees C, was used. Opening pressure, resistance, and anti-reflux properties were determined. RESULTS: The mean (SD) opening pressure was highly dependent on the pressure in the sinus: P(open) = 1.3 (0.6) mm Hg with Psinus = 0.0 mm Hg, and Popen = 7.5 (0.6) mm Hg for Psinus = 6.5 mm Hg. The mean (SD) resistance of the shunts was 7.9 (0.3) mm Hg/ml/min and not clinically significantly affected by the sinus pressure. In one shunt there was reflux, and in another two shunts there was a very small, but similar, tendency. CONCLUSIONS: This study confirms that the resistance of the Sinushunt is comparable to the physiological values in humans. However, the optimal post-operative resistance for different hydrocephalus types is unknown, and randomised clinical trials are needed to confirm improved outcome and reduced complication rate for the Sinushunt compared with traditional low resistance ventriculoperitoneal shunts. A weakness of the anti-reflux system of the Sinushunt must be suspected and has to be further investigated.

Automation↗

PubMed2004

No serological evidence of Rickettsia helvetica infection in Scandinavian sarcoidosis patients.

Many agents have been suggested to elicit sarcoidosis, and, recently, an association was presented between this disease and the bacterium Rickettsia helvetica. The aim of this study was to investigate if serological support for such an association could be detected. Sera from 20 well-characterised sarcoidosis patients were investigated for anti-rickettsial immunoglobulin G antibodies with a micro-immunofluorescence technique. R. helvetica, R. conorii and R. typhi served as antigens. In conclusion, none of the investigated sera displayed detectable titres of anti-rickettsial immunoglobulin G antibodies. Thus, the current study does not support an association between rickettsia and sarcoidosis.

Adult↗

PubMed2003

Evaluation of applanation resonator sensors for intra-ocular pressure measurement: results from clinical and in vitro studies.

Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.

Adolescent↗