Home About us Contact
|
Home About us Contact | ||
|
|
||
Response Analyzer (response + analyzer)
Kinds of Response Analyzer Selected Abstracts4333: How does scleral buckling affect the anterior segment of the eye?ACTA OPHTHALMOLOGICA, Issue 2010FJ ASCASO Purpose To describe the modifications produced in the anterior segment of the eye after placing an encircling scleral buckling (SB) in terms of corneal morphology, biomechanics and intraocular pressure. Methods A prospective study of 15 eyes with rhegmatogenous retinal detachment who underwent pars plana vitrectomy combined with a scleral buckle (PPV/SB), and 12 eyes with vitreous hemorrhage treated with PPV alone. We measured preoperatively and 1-month after surgery the corneal biomechanical properties using the Ocular Response Analyzer (ORA), including corneal hysteresis (CH), corneal resistance factor (CRF), intraocular pressure (IOPg), and corneal compensated IOP (IOPcc). Moreover, we defined the corneal morphology by 4 parameters provided by the topographer Orbscan IIz: mean corneal power (dioptres), standard deviation, thinnest point (µm), and anterior chamber depth (ACD) (mm). Results Mean CH values were significantly diminished following PPV/SB (p=0.003). We found no significant changes in CRF. IOPg and IOPcc mean values were significantly increased only in the PPV/SB group (p=0.019 and p=0.010, respectively) but not in PPV group (p=0.715 and p=0.273, respectively). In PPV/SB group, IOPcc mean values were significantly higher than IOPg before (p=0.001) and after surgery (p=0.003), but not in the other group. None of the morphological parameters were modified after surgery in any of the two study groups (p>0.05) Conclusion Anterior segment morphology was not modified after placing a SB. Corneal biomechanical properties showed a reduction in CH, probably due to a vascular constriction and reduction of the eye compliance. PPV might be considered a less invasive approach for the repair of noncomplex retinal detachments than PPV/SB. [source] 2354: The range of waveform score of Ocular Response AnalyzerTM (ORA) in healthy subjects: interim analysisACTA OPHTHALMOLOGICA, Issue 2010M VANTOMME Purpose To assess the range of waveform score in IOP measurements with ocular response analyzer (ORA, Reichert) in healthy subjects. Methods Prospective study including both eyes of healthy subjects with no ocular pathology or previous refractive surgery. The IOP measurements with ORA from both eyes were performed. The inclusion criteria of the measurements were solely based on good waveforms by an experienced clinician. The waveform score of three measurements were included for statistical analysis. Other parameters including age, central corneal thickness (CCT) and axis length were also analysed to evaluate possible correlations. Spearman correlation coefficient was used to assess the correlation. Results To date, both eyes of 42 healthy subjects are included (Mean age: 46.6 ± 14.3 yrs, Axial length: 23.7 ± 1.1, CCT: 554 ± 34 µm). The mean waveform scores from the first IOP measurement were 4.2±2.3 and for the 2de and 3th respectively 4.2±1.9 and 4.2±2.1 (not significantly different). The mean waveform score of 252 signals (both eyes and 3 measurements) was 4.2±2.1 and ranged from 0.3 to 9.6. Considering the best signal value per patient, the mean of all best signal values was 5.5±2.0 and it ranged from 1.9 to 9.5. The lowest 10% of all the best signal value was<3. Conclusion The waveform score is a new parameter indicating the reliability of each measurement signal. The best signal value indicates the best measurements of each session (Not the mean of the measurements). To date, our results show that the lower 10% percentile is <3. This could suggest that all the measurements with waveform score lower than 3 should be discarded. [source] Corneal hysteresis measured with the Ocular Response Analyzer® in normal and glaucomatous eyesACTA OPHTHALMOLOGICA, Issue 1 2010Olivia Abitbol Abstract. Purpose:, To identify differences in corneal hysteresis (CH) and central corneal thickness (CCT) between healthy and glaucomatous patients. Methods:, Retrospective observational study. One hundred and thirty-three eyes of 75 healthy and 58 glaucomatous patients were included. CH was measured in each patient using Ocular Response Analyzer. CCT was determined by ultrasonic pachymetry. For each patient, one eye was randomly selected. We used a Student t -test to search for significant differences between the different groups (p<0.05). Results:, In healthy and glaucomatous eyes, mean CH values were 10.46 ± 1.6 and 8.77 ± 1.4 mm Hg, respectively. Mean CCT values were 560.2 ± 36.3 and 535.3 ± 42.7 ,m, respectively. CH and CCT were significantly lower in glaucomatous eyes than in normal eyes, (p<0.05). Discussion:, In our series, CH was lower in glaucomatous than in normal eyes. The relationship between glaucoma, IOP, and ocular structures may not be confined to the consideration of CCT. A low CH value could be responsible for under-estimation of IOP. CH could also be a risk factor for glaucoma, independent of IOP. Further studies are needed to support these hypotheses. Conclusion:, In our investigation, CCT and CH were significantly lower in glaucomatous eyes than in healthy eyes. [source] Ocular rigidity and ocular response analyzerACTA OPHTHALMOLOGICA, Issue 2009E IOMDINA Purpose To study ocular rigidity and sclera crosslinking level at diferent stages of primary open angle glaucoma (POAG). Methods Biomechanical parameters of the eye especially corneal hysteresis (CH, mm Hg) were measured in 238 patients (311 eyes) aged 40-84 (median age 67.4 yrs) at various stages of compensated primary open-angle glaucoma using Reichert Ocular Response Analyzer (ORA). Besides, scleral samples obtained during sinus trabeculectomy combined with sclera trephination in the inferio-exterior quadrant of 28 patients (28 eyes) with various stages of POAG were studied using differential scanning calorimetry (Mettler TA 4000 with DSC20 cell). Results Average value (median) of CH gradually decreased from 10.1 mm Hg in the initial glaucoma stage (I) to 9.1 mm Hg in the developed (II) and 8.6 mm Hg in the advanced (III) glaucoma stage. The decrease of this clinical parameter is caused by structural and biochemical damage of the corneoscleral coat. In stage I, endothermic scleral collagen transition occurred at the median thermal peak Tm=60.3 grad.C, while in stages II and III the median peaks of scleral collagen melting emerge at higher temperatures: Tm=62.0 grad.C and Tm=64.5 grad.C, respectively (p<0,05). This testifies to a significant increase of scleral cross-linking and ocular rigidity during glaucoma development. Conclusion Biomechanical and biochemical disorders of glaucomatous sclera may cause clinical changes of ocular rigidity of eyes with POAG. This may be an important link of POAG pathogenesis requiring special therapy. [source] Biomechanical properties of the cornea measured by the Ocular Response Analyzer and their association with intraocular pressure and the central corneal curvatureCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 6 2009Sandra Franco PhD Background:, The aim of this study was to investigate the biomechanical properties of the cornea and their association with intraocular pressure (IOP), central corneal thickness (CCT) and the central corneal radius of curvature (Rc). Methods:, Eighty-three eyes were divided into two groups. The biomechanical properties of the cornea were measured in 63 normal eyes and in 20 post-laser in situ keratomileusis (LASIK) eyes. The IOP, corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the Ocular Response Analyzer (ORA). The Rc and CCT were measured using the corneal topographer Medmont E-300 and the Tomey SP-100 Handy ultrasonic pachymeter. Other parameters measured by the ORA, such as TimeIn and TimeOut, were also studied. Results:, A mean corneal hysteresis of 10.8 mmHg and CRF of 10.6 mmHg were recorded for the normal eyes. There was no significant association with central curvature. All parameters measured by the ORA showed a significant correlation with the CCT, except for the corneal-compensated intraocular pressure (IOPcc). Both IOPs measured by the ORA had the same values for the mean CH and CRF. For the post-LASIK eyes, the CH and CRF were lower than in the normal non-operated eyes. The TimeIn and the TimeOut also presented lower values for the post-LASIK eyes, suggesting that additional data can be obtained with the ORA measurements. Conclusions:, The results of this study indicate that there is no correlation between the parameters measured with the Ocular Response Analyzer and central corneal radius of curvature. Some of the biomechanical properties of the cornea studied were found to differ in the normal eyes compared to the post-LASIK eyes. [source] 2354: The range of waveform score of Ocular Response AnalyzerTM (ORA) in healthy subjects: interim analysisACTA OPHTHALMOLOGICA, Issue 2010M VANTOMME Purpose To assess the range of waveform score in IOP measurements with ocular response analyzer (ORA, Reichert) in healthy subjects. Methods Prospective study including both eyes of healthy subjects with no ocular pathology or previous refractive surgery. The IOP measurements with ORA from both eyes were performed. The inclusion criteria of the measurements were solely based on good waveforms by an experienced clinician. The waveform score of three measurements were included for statistical analysis. Other parameters including age, central corneal thickness (CCT) and axis length were also analysed to evaluate possible correlations. Spearman correlation coefficient was used to assess the correlation. Results To date, both eyes of 42 healthy subjects are included (Mean age: 46.6 ± 14.3 yrs, Axial length: 23.7 ± 1.1, CCT: 554 ± 34 µm). The mean waveform scores from the first IOP measurement were 4.2±2.3 and for the 2de and 3th respectively 4.2±1.9 and 4.2±2.1 (not significantly different). The mean waveform score of 252 signals (both eyes and 3 measurements) was 4.2±2.1 and ranged from 0.3 to 9.6. Considering the best signal value per patient, the mean of all best signal values was 5.5±2.0 and it ranged from 1.9 to 9.5. The lowest 10% of all the best signal value was<3. Conclusion The waveform score is a new parameter indicating the reliability of each measurement signal. The best signal value indicates the best measurements of each session (Not the mean of the measurements). To date, our results show that the lower 10% percentile is <3. This could suggest that all the measurements with waveform score lower than 3 should be discarded. [source] Why do we need a biomechanical approach to the ocular rigidity concept?ACTA OPHTHALMOLOGICA, Issue 2009KE KOTLIAR Ocular rigidity in ophthalmology is generally assumed to be a measurable surrogate parameter related to the biomechanical properties of the whole globe. Clinical tonometry and tonography, as well as recently developed methods to assess the ocular pulse amplitude and pulsatile ocular blood flow and measurements with the ocular response analyzer are based on the concept of ocular rigidity. Clinical concepts of ocular rigidity describe a resulting effect without considerations of possible diverse morphology and material properties of the different ocular tissues. It is commonly accepted that ocular rigidity is related to the elasticity of the sclera. Many formulations are however dependent on the internal volume of the globe, intraocular pressure, corneal biomechanics and thickness of the corneoscleral shell. Sometimes this is extended to biomechanical properties of the ocular vasculature and perfusion pressure. Therefore ocular rigidity is expressed in various units and has different physical meanings but the same name is used which is confusing. Ocular biomechanics introduces parameters of elasticity and viscoelasticity of the sclera, cornea and other tissues which consider the morphology of the different tissues describing their mechanical properties such as: Young's modules of the sclera and Poisson's ratios of the cornea. When applying these rigorous statements and methods of biomechanical modeling a unified concept for ocular rigidity can be developed in order to link the limited clinical concepts, to improve them and to better understand the results of clinical measurements. [source] Ocular rigidity and ocular response analyzerACTA OPHTHALMOLOGICA, Issue 2009E IOMDINA Purpose To study ocular rigidity and sclera crosslinking level at diferent stages of primary open angle glaucoma (POAG). Methods Biomechanical parameters of the eye especially corneal hysteresis (CH, mm Hg) were measured in 238 patients (311 eyes) aged 40-84 (median age 67.4 yrs) at various stages of compensated primary open-angle glaucoma using Reichert Ocular Response Analyzer (ORA). Besides, scleral samples obtained during sinus trabeculectomy combined with sclera trephination in the inferio-exterior quadrant of 28 patients (28 eyes) with various stages of POAG were studied using differential scanning calorimetry (Mettler TA 4000 with DSC20 cell). Results Average value (median) of CH gradually decreased from 10.1 mm Hg in the initial glaucoma stage (I) to 9.1 mm Hg in the developed (II) and 8.6 mm Hg in the advanced (III) glaucoma stage. The decrease of this clinical parameter is caused by structural and biochemical damage of the corneoscleral coat. In stage I, endothermic scleral collagen transition occurred at the median thermal peak Tm=60.3 grad.C, while in stages II and III the median peaks of scleral collagen melting emerge at higher temperatures: Tm=62.0 grad.C and Tm=64.5 grad.C, respectively (p<0,05). This testifies to a significant increase of scleral cross-linking and ocular rigidity during glaucoma development. Conclusion Biomechanical and biochemical disorders of glaucomatous sclera may cause clinical changes of ocular rigidity of eyes with POAG. This may be an important link of POAG pathogenesis requiring special therapy. [source] | ||||||||||