Corneal Hysteresis and Corneal Resistance Factor in Keratoectasia: Findings Using the Reichert Ocular Response Analyzer

2008 ◽  
Vol 222 (5) ◽  
pp. 334-337 ◽  
Author(s):  
Caitriona Kirwan ◽  
Donal O’Malley ◽  
Michael O’Keefe
Keyword(s):  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Ocular Response Analyzer ◽  
Corneal Resistance Factor

scholarly journals Conventional Versus Accelerated Collagen Cross-Linking for Keratoconus: A Comparison of Visual, Refractive, Topographic and Biomechanical Outcomes

2017 ◽  
Vol 11 (1) ◽  
pp. 262-272 ◽  
Author(s):  
Jyh Haur Woo ◽  
Jayant Venkatramani Iyer ◽  
Li Lim ◽  
M Htoon Hla ◽  
Jodhbir S Mehta ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Endothelial Cell ◽  
Cell Loss ◽  
Corneal Topography ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Cross Linking ◽  
Corneal Resistance Factor ◽  
Accelerated Crosslinking

Objective: The aim was to compare the visual, refractive, topographic and biomechanical outcomes in patients with progressive keratoconus treated with either conventional or accelerated crosslinking at one year follow up. Methods: It is a prospective, non-randomised interventional study of 76 patients who underwent conventional (CXL; 3mW/cm2 for 30 minutes) or accelerated cross linking (KXL; 30mW/cm2 for 4 minutes) for progressive keratoconus. Baseline and postoperative visual acuity, manifest refraction, corneal topography, pachymetry, endothelial cell density and biomechanical parameters of corneal hysteresis and corneal resistance factor were evaluated and compared. Results: The 2 groups were comparable in terms of uncorrected and best corrected visual acuity and spherical equivalent. Both groups showed no significant increase in K1, K2 and Kmean from baseline at 12 months. There was also no difference between the CXL and KXL group for postoperative corneal topography as well as central and minimal pachymetry up to 12 months. There was a significant increase in both corneal hysteresis (0.62mm Hg, P=0.04) and corneal resistance factor (0.91mm Hg, P=0.003) in the KXL group at 12 months but not in the CXL group. There was no significant endothelial cell loss throughout follow up in both the groups. Conclusion: We have established comparability of the 2 protocols in stabilizing the progression of keratoconus. Our findings also suggested an added biomechanical advantage of accelerated crosslinking at 1 year follow up.

Relationship between Corneal Biomechanical Properties and Optic Nerve Head Changes after Deep Sclerectomy

2017 ◽  
Vol 27 (5) ◽  
pp. 535-541 ◽  
Author(s):  
Laura Díez-Álvarez ◽  
Francisco J. Muñoz-Negrete ◽  
Pilar Casas-Llera ◽  
Noelia Oblanca ◽  
Victoria de Juan ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Optic Nerve Head ◽  
Open Angle Glaucoma ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Enhanced Depth Imaging ◽  
Deep Sclerectomy ◽  
Corneal Resistance Factor ◽  
Corneal Biomechanical Properties

Purpose To evaluate corneal biomechanical properties and optic nerve head (ONH) changes following deep sclerectomy (DS) and the relation to each other. Methods Forty-nine eyes with primary open-angle glaucoma that underwent DS were studied. Corneal biomechanical properties were assessed using the Ocular Response Analyzer and the ONH was evaluated by Spectralis optical coherence tomography with enhanced depth imaging technology before surgery and 3 months postoperatively. Changes in corneal hysteresis (CH), corneal resistance factor (CRF), optic nerve cupping, prelaminar tissue thickness, and lamina cribrosa depth and thickness were registered. A correlation matrix and multiple linear regression models were used to determine predictors of ONH changes. Results At 3 months after surgery, mean corneal compensated intraocular pressure (IOPcc) significantly decreased by 27.9% (p<00.001) and mean Goldmann-correlated IOP (IOPg) decreased by 30.52% (p<00.001). Mean CH increased and CRF decreased by 18.4% and 10.1%, respectively (p<00.001). There was a significant reversal of ONH cupping mainly due to a prelaminar tissue thickening (p<00.001). Significant associations were found between ONH cupping reversal and prelaminar tissue thickening with preoperative IOPcc (p = 0.046), IOPg (p = 0.02), and CRF (p = 0.002) and with changes in IOP, CH, and CRF (p<00.001, p = 0.004, p = 0.018, respectively) after surgery. Conclusions Corneal hysteresis increased and CRF decreased significantly 3 months after DS. Corneal resistance factor was the single largest preoperative factor influencing cupping reversal changes. Despite the influence of preoperative variables, postoperative IOP reduction was the only independent factor influencing changes observed in the ONH after surgery.

scholarly journals Corneal Biomechanical Changes in Third Trimester of Pregnancy

Medicina ◽  
2021 ◽  
Vol 57 (6) ◽  
pp. 600
Author(s):  
Inna Adriana Bujor ◽  
Raluca Claudia Iancu ◽  
Sînziana Luminiţa Istrate ◽  
Emil Ungureanu ◽  
George Iancu
Keyword(s):  
Intraocular Pressure ◽  
Sex Hormones ◽  
Statistical Significance ◽  
Retinal Pigment ◽  
Resistance Factor ◽  
Corneal Biomechanics ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Third Trimester ◽  
The Third

Background and Objectives: There is a clear evidence that pregnancy is associated with high production of sex hormones. During the first, second and third trimester of pregnancy, blood hormones levels increase gradually. Cells with affinity for sex hormones have been identified in different ocular tissues, such as: lid, lacrimal gland, meibomian gland, bulbar and palpebral conjunctivae, cornea, iris, ciliary body, lens, retina (retinal pigment epithelium) and choroid. This is why pregnancy is associated with changes at ocular level, involving anterior and posterior segments. Several clinical trials have been made trying to highlight changes in corneal biomechanics during pregnancy. By conducting this review, we want to evaluate both the changes in parameters that define corneal biomechanics and intraocular pressure values in pregnant. Materials and Methods: Following a systematic search in the literature related mainly to changes in corneal biomechanics during pregnancy, focusing on the paper published in the last decade, we included in a meta-analysis the cumulative results of three prospective comparative studies. Results: Important changes in corneal biomechanics (corneal hysteresis and corneal resistance factor) parameters were observed in women in the third trimester of pregnancy, but these variations were not statistically significant. Also, a decrease in intraocular pressure was mentioned in these women, but only the corneal compensation intraocular pressure showed a decrease with statistical significance. Conclusions: A decrease in corneal compensatory intraocular pressure was observed in pregnant women in the third trimester of pregnancy, but without other statistically significant changes resulting from the analysis of the other three parameters (corneal hysteresis, corneal resistance factor and Goldmann-correlated intraocular pressure).

scholarly journals Biomechanical Properties in Different Types of Thin Corneas in Menoufia Population

2020 ◽  
Author(s):  
Adel Galal Zaky ◽  
Amin Faisal Ellakwa ◽  
Ahmed Ibrahim Basiony
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Study Groups ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Significant Difference ◽  
Different Types ◽  
The Mean

Abstract Background:To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in normal thin (NT) healthy corneas with central corneal thickness (CCT) 470-500 µm with matched thickness in keratoconus suspect (KCS) and keratoconus (KC) and eyes.Methods: A total of 103 eyes in three groups were included prospectively: NT, KCS and KC groups based on clinical examination and pentacam findings. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the ocular response analyzer (ORA). CCT ,CH and CRF were compared between the three groups and statistically analyzed by variance tests.Results:The three groups consisted of 44 NT, 26 KCS, and 33 KC. The mean CH measured was 8.689 ± 1.775, 9.051 ± 1.1190 and 8.129 ± 0.8539 mmHg in NT, KCS and KC eyes, respectively. The mean CRF was 8.441 ± 1.663, 8.337 ± 1.114 and 7.2422 ± 1.3110 mmHg in NT, KCS and KC eyes, respectively. Within range of central corneal thickness (470 – 500 µm), only mean CRF was statistically significantly different between the NT and KC (P < 0.05); there was no statistically significant difference between NT and KCS, nor the mean CH between each group (P > 0.05).Conclusions: CRF only can be helpful in differentiating KC from NT eyes; KCS could not be predicted with either corneal biomechanical metrics. No benefit from CH in differentiating between the three study groups.

Corneal Hysteresis, Corneal Resistance Factor, and Intraocular Pressure Measurements in Eyes Implanted With a Small Aperture Corneal Inlay

2014 ◽  
Vol 30 (12) ◽  
pp. 831-836 ◽  
Author(s):  
Alper Agca ◽  
Ahmet Demirok ◽  
Haci Ugur Çelik ◽  
Corina van de Pol ◽  
Kadir Ilker Çankaya ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Pressure Measurements ◽  
Corneal Resistance Factor ◽  
Small Aperture ◽  
Corneal Inlay

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

2021 ◽  
Author(s):  
Sonia Razafimino ◽  
Elias Flockerzi ◽  
Elena Zemova ◽  
Christian Munteanu ◽  
Berthold Seitz
Keyword(s):  
Thyroid Dysfunction ◽  
Resistance Factor ◽  
Ocular Response Analyzer ◽  
Longitudinal Analyses ◽  
Longitudinal Assessment ◽  
Corneal Resistance Factor ◽  
Cross Sectional ◽  
Gender And Age ◽  
Biomechanical Parameters ◽  
Corneal Tomography

Abstract Background and Purpose The etiology of keratoconus (KC) is probably multifactorial but remains essentially unknown. Previous scientific observations have suggested that hypothyroidism might play a role in the development and progression of KC. The purpose of this study was to analyze the tomographic and biomechanical parameters in KC patients with or without hypothyroidism. Methods Twenty-eight patients with KC and hypothyroidism (HT group) and fifty-six KC patients without thyroid dysfunction (WHT group) with matching gender and age were analyzed. Mean age was 40.3 years (range 14 – 57) in the HT group and 40.3 years (range 14 – 57) in the WHT group. Routine ophthalmic examinations consisted of corneal tomography and biomechanical parameters. We extracted the following KC parameters from the Pentacam (Pentacam HR, Oculus, Wetzlar, Germany): Keratoconus Index (KI), maximum keratometry (Kmax), astigmatism, and thinnest pachymetry (TP). From the ocular response analyzer (ORA, Reichert Ophthalmic Instruments, Depew, NY, USA), we extracted corneal hysteresis (CH), corneal resistance factor (CRF), and KC match index (KMI). Results The comparison of the tomographic and biomechanical values from cross-sectional and longitudinal analyses showed no significant differences between the HT and WHT groups. Conclusion The severity of KC based on tomographical and biomechanical parameters does not seem to depend on the presence of hypothyroidism.

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