Corneal Hysteresis In Patients Research Articles

Diurnal Variation of Corneal Hysteresis in Patients With Untreated Primary Open Angle Glaucoma and Normal Individuals.

Corneal hysteresis in both patients with untreated open angle glaucoma and normal individuals demonstrated significant diurnal variation independent of confounding factors and was higher in the nighttime than in the daytime. To investigate diurnal variations in corneal hysteresis (CH) in patients with untreated primary open angle glaucoma (POAG) and normal individuals by using an ocular response analyzer. This prospective study included 72 eyes of 53 patients with untreated POAG and 53 eyes of 47 normal individuals. Intraocular pressure (IOP) and CH were measured using Goldmann applanation tonometry (GAT) and ocular response analyzer, respectively, every 3 hours from 9:00 to 24:00. Mixed-effects models were used to determine factors associated with CH values and CH amplitude (maximum values minus minimum values) and to examine the diurnal variations in GAT IOP and CH in each group. Significant differences between time points were defined as significant variations. The diurnal average GAT IOP and CH in patients with POAG were significantly higher and lower than those in normal individuals ( P =0.001, 0.002). In the multivariate analysis, the larger central corneal thickness was associated with larger CH values in POAG and normal eyes (both P <0.001). A larger amplitude of GAT IOP was significantly associated with a larger CH amplitude in POAG and normal eyes ( P =0.010, 0.013). CH, in both groups, showed similar significant diurnal variation and was higher in the nighttime than in the daytime, even after adjusting for confounding factors, while IOP showed an antiphase pattern. CH in both untreated POAG patients and normal participants demonstrated similar diurnal variations, that is, higher at night, independent of confounding factors. These findings suggest that viscoelastic properties of the cornea may fluctuate diurnally independent of IOP.

The Effects of Anti-glaucoma Eyedrops on Corneal Hysteresis in Patients with Open-angle Glaucoma and Glaucoma-suspect

Purpose: We explored the effects of topical anti-glaucoma medications on the corneal biochemical properties of patients with open-angle glaucoma (OAG) and glaucoma suspect (GS patients).Methods: We retrospectively reviewed data on 115 OAG and 98 GS patients (225 and 128 eyes respectively). Corneal hysteresis (CH) was measured using an ocular response analyzer. Factors influencing CH were determined using a generalized estimation equation.Results: The mean CH was lower in OAG than GS patients (p &lt; 0.001). A lower cornea-compensated intraocular pressure, concomitant use of a beta-adrenergic blocker and an alpha2-adrenergic agonist, a higher visual field mean deviation, and a larger central corneal thickness were associated with a higher CH in the OAG group.Conclusions: Concomitant use of a topical beta-adrenergic blocker and an alpha2-adrenergic agonist was associated with a higher CH.

The association between oxidative stress and corneal hysteresis in patients with glaucoma

Systemic antioxidative status has been implicated in glaucoma pathogenesis. Additionally, corneal hysteresis (CH) may contribute to glaucoma progression. Here, we evaluated the relationship between biological antioxidant potential (BAP) and CH. This study included 103 patients with open-angle glaucoma (OAG). We used a free radical analyzer to measure BAP, and an ocular response analyzer to measure CH and corneal resistance factor (CRF). We evaluated the relationship between systemic oxidative stress and other clinical parameters with Spearman’s rank correlation test and a multi-regression analysis. BAP was not correlated to either CH or CRF in the male or female OAG patients. BAP was correlated to both CH and CRF in the female OAG patients older than 57 years (r = 0.51, P = 0.003; r = 0.49, P = 0.004), but uncorrelated in the female OAG patients younger than 57 years. Multiple regression analysis revealed that BAP independently contributed to CH (P = 0.025) and CRF (P = 0.015) in the older female OAG patients. Systemic oxidative stress may significantly affect the viscoelasticity of the cornea in older female OAG patients. Future studies are needed to confirm that low systemic antioxidative status and low corneal hysteresis contribute to glaucoma pathogenesis.

This issue of ACTA, printed and electronic

The cover illustration is a schematic drawing showing surgical technique for retinal vein cannulation and tissue plasminogen injection. This is reported by van Overdam et al. in this issue of Acta. Chan et al. in China review conflicting reports on the efficacy of corneal collagen cross-linking in infectious keratitis. Klefter et al. in Denmark measure increased retinal oxygen extraction in hyperglycaemia in patients with diabetes. van den Akken-van Marle et al. in Leiden recommend a risk factor guided screening programme for retinopathy of prematurity. Lin et al. in Taiwan correlate diabetic polyneuropathy and retinopathy in a nationwide study. vRezar et al. in Vienna report long-term benefits from anti-VEGF treatment for macular oedema in BRVO. Early treatment gives better visual outcome. Hautamäki et al. in Helsinki suggest that interleukin-8 may play a role in neovascularization in AMD. Fauser et al. in Köln measured elevated local inflammatory cytokines in neovascular AMD eyes. van Overdam et al. in Rotterdam show a surgical technique for retinal vein cannulation and tissue plasminogen injection in CRVO. Peters et al. in Sweden associate visual field index under 50% and/or mean defect worse than 18 dB with poor quality of life. Matlach et al. in Germany find trabeculectomy to reduce IOP more than canaloplasty, but with more complications. Rönnback et al. in Copenhagen and Singapore find genotype–phenotype heterogeneity in autosomal dominant optic atrophy. Mathew et al. in Houston and Uppsala find lamellar splitting in histological examination of keratoconus. Ekström and Taube in Uppsala suggest that pseudoexfoliation is a risk factor for cataract formation. Aclimandos et al. in UK, Belgium, France and Switzerland inform us about EBO's subspeciality examinations. Pérez-Cambrodí et al. in Spain and Poland review cataract aspiration with hollow needle in antiquity. The following articles are published in the electronic issue of ACTA and are accessible on www.actaophtalmologica.com, where you can also access the printed articles. Anitua et al. in Spain and USA examine the use of blood derived formulations used for the treatment of ocular surface disorders. Aptel et al. in France find great variation in progression visual field damage in POAG. Pillunat et al. in Germany stress nocturnal blood pressure dips in patients with glaucoma and relate this to daytime blood pressure measurements. Hussnain et al. in USA found more decline in corneal hysteresis in patients with glaucoma, but diabetes had no impact. Sheu et al. in Taiwan examined the effect of anti-VEGF drugs on retinal pigment epithelial cells and found variable effects on mitochondrial bioenergetics. Murakami et al. in Japan found reduced blood flow in macula to be associated with visual deterioration. Achiron et al. in Israel quantify metamorphopsia in DME and other macular diseases. Petrovic et al. in Slovenia and Czeck Republic relate a gene for reactive oxygen species modulation to the progression of diabetic retinopathy. García et al. in Spain and USA confirm the role of complement factor H gene in AMD and found variable effects of different haplotypes. Vagge et al. in Italy used near-infrared reflectance to image choroidal lesions in neurofibromatosis. Stemplewitz et al. in Germany found reduce macular volume and retinal nerve fibre thickness in patients with Parkinson's disease. Hoskin et al. in Australia emphasize the risk of fishing accidents and the need for eye protection. Vestergaard et al. in Odense find penetrating eye injuries to be most common in young men. Kuiper et al. in Utrecht discuss aqueous humour versus vitreal measurements of interleukins in diagnosis of ocular lymphoma. Tachibana et al. in Japan find improvement in horizontal but not vertical metamorphopsia following epiretinal membrane peeling. Suh et al. in Korea connect a connective tissue growth factor gene with pseudoexfoliation. Tode et al. in Germany use anti-interleukin-6 treatment for necrotizing scleritis. Örnek et al. in Turkey report transient thinning of choroid with bevacizumab injections for DME. Fonollosa et al. in Spain used a kinase inhibitor, vemurafenib to treat macular oedema in uveitis. Schäffer et al. in Austria relate anterior vitreous attachment and pseudophakic retinal detachments. I wish you a Merry Christmas, happy holidays and a prosperous New Year!

Influence of visual load on the functional, hydrodynamic and biomechanical indicators of eye in children with different types of optical correction of myopia

Questions of preference one or another type of optical correction of myopia in terms of stabilization of progression of the disease in children remain the subject of discussions and require further research.The aim of research - to examine the effect of visual load on parameters of ophthalmotone, biomechanical parameters and accommodative function of the eye in children with various types of optical correction of myopia.Materials and methods. We examined 40 children with myopia from 0.75 to 4.5 dpt, aged 7-14 years. I monitoring group - 23 children (46 eyes) passed course of orthokeratology more than 4-6 months. II monitoring group - 17 children (34 eyes) used glasses for correction. Control group - 15 children (30 eyes) was with emmetropia without ophthalmic pathology. Before and after 30-minute visual load at the computer reserves of relative accommodation were determined, with the use of the Ocular Response Analyzer, corneal-compensated intraocular pressure and corneal hysteresis.Results. Initial level of corneal-compensated intraocular pressure and corneal hysteresis in patients with myopia of both groups did not differ, however, in relation to emmetropic eye (a control group) it was statistically significantly higher (p = 0.0003). Corneal hysteresis index was also significantly different in patients with myopia than in children with emmetropia (p &lt;0.01). The lowest values of the relative accommodation were revealed in patients of II monitoring group - 1,95 ± 0,06 dpt (p &lt;0.01) and almost the same in patients of I monitoring group and in patients with emmetropia (3,45 ± 0,07 dpt and 3,52 ± 0,08 dpt, respectively, p&gt; 0.05).After 30-minute visual load indicators of corneal-compensated intraocular pressure and pressure by Goldman in patients of I monitoring group and control group have increased insignificantly and amounted 15,8 ± 0,4 mm Hg; 16,5 ± 0,5 mmHg and 13,3 ± 0,3 mmHg; 15,3 ± 0,8 mmHg respectively. In children of II monitoring group, with glasses correction in response to visual load corneal-compensated intraocular pressure, and the pressure by Goldman to 17,3 ± 0,47 mmHg and 17,9 ± 0,45 mmHg (p &lt;0.01) increased. The response of corneoscleral capsule of eyeball on visual load at a short distance was also different in patients. Thus, in patients of I monitoring group corneal hysteresis difference was not reliable and averaged 12,8 ± 0,2 (p&gt; 0.05). In children with emmetropic refraction corneal hysteresis value was also not significantly changed - 13,7 ± 0,3 (p&gt; 0.05). Significant reduction of corneal hysteresis occurs in the control group I to 11,4 ± 0,26 mmHg (p = 0.02).The stock of relative accommodation after visual load in patients of I monitoring group did not change significantly and amounted 3,25 ± 0,06 dpt (p&gt; 0.05), as well as in the control group - 3,49 ± 0,07 dpt (p&gt; 0.05). In patients of II monitoring group the stock of relative accommodation authentically decreased to 0,92 ± 0,06 dpt (p &lt;0.05).Conclusion. In patients using orthokeratology lenses, after visual load a significant increase of corneal-compensated intraocular pressure lowering of corneal hysteresis and the stock of relative accommodation is only observed in 27% of cases, unlike children using glasses for correction, which in 88.2% cases observed deviation of these parameters by 1.2 times of the original data.

Comment on ‘Corneal hysteresis in patients with dry eye’

Sir, We read with interest Firat and Doganay's1 recent report on effects of dry eye on corneal biomechanics. We propose the authors missed the opportunity to review an interesting hypothesis because of inadequate study design and methodology. Whereas the report aimed to determine effects of dry eye, the disease classification and study enrolment criteria were poorly defined. We would like to bring to the authors attention the International Dry Eye Workshop report (2006) that provides a standardized classification for diagnosis and grading severity of dry eye.2 Including patients with significant ocular surface disorders may have allowed accurate conclusions. The absence of significant difference in corneal thickness probably reflects milder disease in the study group.3 Goldman applanation tonometry (GAT) is based on assumptions of the tear film and known to be affected by the central corneal thickness. The Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) is a non contact tonometer that measures the biphasic corneal response to generate a cornea compensated intraocular pressure (IOPcc). The more interventional contact GAT measurements were surprisingly recorded earlier in the sequence of measurements. Data for analysis and comparison of IOP between the two instruments or even the Goldmann-correlated IOP measurement, IOPG (average of the biphasic pressure readings generated by the ORA) vs IOPCC, are not provided. The results are duplicated in text and bar chart format, as opposed to use of a scatter plot with range of measurements and do not contribute to the discussion. The authors' hypothesis on effect of dry eye in IOP measurements (traditional and newer cornea compensated values) and corneal biomechanics can have important clinical implications. However, the lack of definition and severity grading of dry eye makes it difficult to draw accurate conclusions.

Corneal hysteresis in patients with dry eye

To measure corneal hysteresis and intraocular pressure (IOP) in patients with dry eye and to compare with normal subjects. This cross-sectional study consists of 70 eyes of 40 patients with dry eye (group 1) and 75 eyes of 40 normal subjects (group 2). Eyes were diagnosed as dry eye or normal according to the clinical symptoms, biomicroscopical evaluation, and Schirmer test. Corneal hysteresis (CH), corneal resistance factor (CRF), and cornea-compensated intraocular pressure (IOPcc) were measured by the Ocular Response Analyser (ORA). Mean CH values were 10.56±0.25 mm Hg and 10.34±0.26 mm Hg, mean CRF values were 10.75±0.28 mm Hg and 10.70±0.28 mm Hg, mean CCT values were 542±3.20 μm and 543±3.89 μm in group 1 and group 2, respectively. There was no statistically significant difference between the groups for these three parameters. IOPcc values measured with ORA were 15.73±0.36 mm Hg in group 1 and 16.60±0.33 mm Hg in group 2, and there was no statistically significant difference between the two groups. Corneal biomechanical parameters such as CH and CRF are not influenced in dry eye. Also statistical difference was not found between the two groups according to CCT and IOPcc values.

Are Ocular Response Analyzer useful to measure corneal hysteresis in patients with intracorneal rings?

Abstract Purpose Corneal hysteresis is a viscoelastic property characterized by the difference in behavior under loading and unloading. The aim of the study was to determine corneal hysteresis in different eyes: healthy eyes, keratoconic eyes and keratoconic eyes after intracorneal ring implants. Methods This study comprised 95 eyes of 59 patients. The study population was divided into 3 groups. We analyze 30 healthy human eyes, 35 keratoconic eyes (Amsler grade II‐III) and 30 keratoconic eyes after intracorneal rings implantation. Corneal biomechanical properties of these eyes were measured with the Ocular Response Analyser (ORA‐Reichert) according to two parameters: corneal hysteresis (CH) and corneal resistance factor (CRF. The unpaired T student test was used for statistical analysis. Results Mean CH and CRF in normal eyes (10.78 ± 1.6 (SD) mm Hg, 11.91 mm Hg ± 1.2) was clearly superior than in keratoconus group (8.01 ± 1.5 mm Hg, 7.32 ±1.8 mm Hg). However the difference of these parameters between keratoconus group without intracorneal rings and after corneal ring implantation (7.27mm Hg, 6.32 mm Hg) was not statistically significant (p ≤ 0.01). Mean follow‐up period was of one year. Conclusion Corneal hysteresis and CRF values were significantly lower in keratoconic eyes than in normal eyes. But there is no marked differences if we compare these two biomechanical parameters in keratoconic corneas, before and after corneal ring implants. Improvements in the software accuracy of the ORA devices are needed to characterize corneal biomechanics.

Corneal hysteresis in patients with corneal pathologies

Abstract Purpose: To investigate the corneal hysteresis (CH), the corneal resistance factor (CRF) and the corneal compensated intraocular pressure (IOPcc) of subjects with normal corneas and with corneal pathologies with the Ocular Response Analyzer (ORA). Methods: IOP was measured using Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT) and ORA in 102 subjects with normal corneas and in patients with keratoconus (KC, n=32), Fuchs endothelial corneal dystrophy (FD, n=34) and penetrating keratoplasty (KP, n=50). Additionally central corneal thickness (CCT) and CH were quantified. Results: CH and CRF were significantly reduced in all groups with corneal pathologies in comparison to the normal group (CH: 7.7 (KC), 8.9 (KP), 7.3 (FD) versus 10.3 (N), CRF: 6.4 (KC), 9.3 (KP), 8.2 (FD) versus 10.8 (N) mmHg). High significant differences were also observed in mean IOP between the control group and the groups with corneal pathologies. There was a significant correlation between CH and CCT for normal corneas and corneas with KC and KP. Conclusions: CH and CRF are significantly decreased in patients with KC, FD and KP compared to subjects with normal corneas. Patients with corneal pathologies showed a substantial variability of mean IOP‐values evaluated by using different methods of IOP‐measurement in comparison to subjects with normal corneas suggesting that corneal properties strongly influence the validity of IOP‐measurements.