Corneal Biomechanical Properties In Patients Research Articles

The Impact of Intraocular Pressure Changes on Corneal Biomechanics in Primary Open-angle Glaucoma

PurposeTo investigate the relationship between intraocular pressure (IOP) changes and corneal biomechanical properties, determine the quantitative relationship between IOP changes and corneal biomechanical properties in patients with glaucoma and observe the differences among different types of glaucoma when the effects of high-level IOP were excluded. DesignProspective clinical cohort study. MethodsSetting: Institutional. Patients: Treatment-naive patients with primary open-angle glaucoma or ocular hypertension (OHT) were included. Observation Procedures: IOP was measured using a Goldmann applanation tonometer. Corneal biomechanics were evaluated using a corneal indentation device and corneal visualization Scheimpflug technology. Medication therapy was used for IOP reduction. Repeated measurements were taken at the baseline visit and each week thereafter within a month. Paired t tests were used to compare IOP and corneal biomechanical metrics before and after IOP-lowering therapy. One-way analysis of variance was employed to investigate potential differences across groups, with a Bonferroni post hoc correction administered for multiple intergroup comparisons. Main Outcome Measures: Corneal biomechanical parameters following IOP changes. ResultsEighty-one participants (mean age, 41.63 ± 17.33 years) were included in this study. The cohort comprised 20 patients with normal-tension glaucoma (NTG), 47 with high-tension glaucoma (HTG), and 14 with OHT. The baseline corneal stiffness (88.58±18.30 N/m) and corneal modulus (0.71±0.16 MPa) were greater than the post-IOP reduction values (67.15±9.24 N/m and 0.54±0.08 MPa, respectively; P<0.001). The relationships between changes in IOP and changes in corneal biomechanical parameters were Δ corneal stiffness=2.06*ΔIOP+6.47 (P<0.001) and Δ corneal modulus=0.017*ΔIOP+0.051 (P<0.001). After IOP reduction, the mean corneal stiffness at the 4th week in the NTG group was significantly lower (60.97±6.36 N/m) than that in the HTG (67.25±9.01 N/m) and OHT (75.62±6.52 N/m, P < 0.001) groups. Additionally, the stiffness of HTG patients was lower than that of OHT patients (P = 0.003). ConclusionsChanges in IOP have an impact on corneal biomechanical parameters. Decreases in corneal stiffness and modulus were observed after IOP reduction. When the effect of high-level IOP was excluded, corneal biomechanics varied according to the type of glaucoma. The HTG corneas were softer than the OHT corneas, and the NTG corneas were even softer.

Corneal Biomechanical Properties to Predict Prognosis of Abnormal Tomographic Corneas: A Prospective Cohort Study

To analyze the corneal biomechanical properties in patients with abnormal corneal tomography (ACT) and predict their stability using the biomechanical stability index (BSI). Prospective cohort study. Setting: Multicenter study. This study included 385 eyes of 278 patients with stable ACT (n = 70), subclinical keratoconus (SKC, n = 65), keratoconus (n = 65), normal controls (NL, n = 142). Forty-three eyes with first-visit ACT were included in a separate cohort (follow-up ACT group). Tomographical and biomechanical parameters (Pentacam and Corvis ST) were recorded. Nonparametric tests were used for comparison. Logistic regression was employed to introduce BSI to separate stable ACT and SKC accurately. An independent dataset of 43 first-visit ACT eyes was followed up for 1 year to validate BSI's accuracy and positive and negative predictive values (PPV, NPV). The tomographical and biomechanical parameters in patients with Stable ACT remained stable over the follow-up period (12.73 ± 2.57 months, P > .05). Stable ACT had 12/14 biomechanical parameters different (P < .05) from SKC but not different from NL (P > .05). With a cut-off value of 0.585, BSI demonstrated the strongest ability to distinguish between stable ACT and SKC (area under the receiver operating characteristic curve = 0.991), with 93.85% sensitivity and 97.14% specificity. During the 1-year follow-up of 43 eyes (follow-up ACT group), 30 remained stable. The accuracy, PPV, and NPV of the BSI were 95.35%, 100%, and 93.75%, respectively. Biomechanical properties of patients with stable abnormal tomography corneas were stronger than SKC and close to normal corneas, which may explain the reason for tomographic stability. The BSI may be useful for predicting disease progression in patients with ACT and the possible management of corneal cross-linking at the first visit.

The role of corneal biomechanical properties assessment in laser vision correction – the introduction

The role of corneal biomechanical properties in patients referred to laser vision correction (LVC) is currently being raised. Understanding of corneal biomechanics may support the proper selection of refractive surgery candidates, improve the refractive outcomes and safety of refractive procedures. The Ocular Response Analyzer (ORA) and Corvis ST are commonly used devices to assess corneal biomechanical parameters in LVC. The vertical corneal incisions have a greater impact on corneal biomechanics weakening than horizontal incisions. Maintaining the high biomechanical strength of the cornea following LVC can decrease the potential risk of postoperative ectasia.

Corneal Biomechanics in Non-infectious Uveitis Measured by Corvis ST: A Pilot Study

ABSTRACT Purpose To assess differences between corneal biomechanical properties in patients with non-infectious uveitis and healthy subjects using CorVis. Methods 77 patients with non-infectious uveitis and 47 control subjects were recruited. Biomechanical parameters were measured: deformation amplitude (DA), A-1 length and A-2 length (L1, L2), A-1 velocity and A-2 velocity (V1, V2), peak distance (PD) and HC radius (highest concavity radius). AUC ROC and correlation between clinical variables and biomechanical properties were determined. Results Lower HC Radius and IOPb and higher DA and V1 was found in uveitis group. Statistical differences between cases using systemic medications and those with topical treatment were found in L1. Differences were showed between those cases with active and inactive uveitis in PD, DA, V2 and L2. The biomechanical parameter with the best discriminatory capacity of uveitis disease was HC Radius. Conclusion Differences in corneal biomechanical properties between non-infectious uveitis and healthy eyes were found.

Fuchs heterokromik iridosiklit hastalarında kornea biyomekaniği ve kornea değerlendirilmesi

Amaç: Bu çalışmanın amacı Fuchs heterokromik iridosiklit (FHİ) tanılı gözler ile sağlıklı diğer gözlerin kornealarının ve kornea biyomekanik özelliklerinin karşılaştırılmasıdır. Gereç ve Yöntem: Fuchs heterokromik iridosiklit tanılı 14 göz (Grup 1) ve sağlıklı diğer gözler (Grup 2) çalışmaya dâhil edildi. Tüm hastalara detaylı bir oftalmolojik bakıyı takiben Ocular Response Analyzer korneal biyomekanik özellikler ve speküler mikroskobi ile santral korneal kalınlık (SKK), korneal endotelyal hücre dansitesi (KEHD) değerlendirildi. Bulgular: En iyi düzeltilmiş görme keskinliği ve intraoküler basınç istatistiksel olarak benzerdi (p değerleri sırasıyla 0,077 ve 0,557). Korneal biyomekanik parametreleri olan korneal histerezis, korneal resiztans faktör, IOPcc ve IOPg değerleri her iki grupta istatistiksel olarak benzerdi (p değerleri sırasıyla; 0,521, 0,817, 0,980 ve 0,980 idi). Ortalama santral korneal kalınlık Grup 1’de 555,57±42,95 (467-626) mikron ve Grup 2’de 556,5±37,04 (480-623) mikron olarak saptandı (p=0,959). Ortalama korneal endotel hücre dansitesi Grup 1’de 2313±420,22 (1271-2717) ve Grup 2’de 2404,42±326,75 (1566-2834) hücre/mm2 saptandı (p=0,626). Sonuç: Sağlıklı gözler ile Fuchs Heterokromik İridosiklit tanılı gözler karşılaştırıldığında kornea biyomekanik parametreleri ve korneal endotel hücre dansitesi arasında anlamlı fark saptanmamıştır. Bu sonuçlar literatürdeki birçok çalışma ile çelişmekte olup daha geniş vaka serileri ile yeni çalışmalara ihtiyaç vardır.

Alteration of corneal biomechanical properties in patients with dry eye disease.

PurposeTo evaluate the association between symptoms and signs of dry eye diseases (DED) with corneal biomechanical parameters.MethodsThis cross-sectional study enrolled 81 participants without history of ocular hypertension, glaucoma, keratoconus, corneal edema, contact lens use, diabetes, and ocular surgery. All participants were evaluated for symptoms and signs of DED using OSDI questionnaire, tear film break-up time (TBUT), conjunctival and corneal staining (NEI grading) and Schirmer test. Corneal biomechanical parameters were obtained using Corvis ST. Mixed-effects linear regression analysis was used to determine the association between symptoms and signs of DED with corneal biomechanical parameters. Difference in corneal biomechanical parameter between participants with low (Schirmer value ≤10 mm; LT group) and normal (Schirmer value >10mm; NT group) tear production was analyzed using ANCOVA test.ResultsThe median OSDI scores, TBUT, conjunctival and corneal staining scores as well as Schirmer test were 13±16.5 (range; 0–77), 5.3±4.2 seconds (range; 1.3–11), 0±1 (range; 0–4), 0±2 (ranges; 0–9) and 16±14 mm (range; 0–45) respectively. Regression analysis adjusted with participants’ refraction, intraocular pressure, and central corneal thickness showed that OSDI had a negative association with highest concavity radius (P = 0.02). The association between DED signs and corneal biomechanical parameters were found between conjunctival staining scores with second applanation velocity (A2V, P = 0.04), corneal staining scores with second applanation length (A2L, P = 0.01), Schirmer test with first applanation time (A1T, P = 0.04) and first applanation velocity (P = 0.01). In subgroup analysis, there was no difference in corneal biomechanical parameters between participants with low and normal tear production (P>0.05). The associations were found between OSDI with time to highest concavity (P<0.01) and highest displacement of corneal apex (HC-DA, P = 0.04), conjunctival staining scores with A2L (P = 0.01) and A2V (P<0.01) in LT group, and Schirmer test with A1T (P = 0.02) and HC-DA (P = 0.03), corneal staining scores with A2L (P<0.01) in NT group.ConclusionsAccording to in vivo observation with Corvis ST, patients with DED showed more compliant corneas. The increase in dry eye severity was associated with the worsening of corneal biomechanics in both patients with low and normal tear production.

Corneal biomechanics in connective tissue disorders

Purpose: The purpose of this study is to determine the corneal biomechanical properties in patients with connective tissue disorders (CTDs) and compare them with age-matched healthy control. Materials and Methods: In this cross-sectional study, 62 patients (study group) with CTDs and 44 healthy patients (control) were analyzed by Ocular Response Analyzer (Reichert Inc., Depew, N. Y., USA) and Corneal Pachymetry (SP-2000, Tomey, Nagoya, Japan). The right eye of all patients was assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPc), and Goldmann-correlated intraocular pressure (IOPg), and central corneal thickness (CCT). Results: Mean CH (9.54 ± 1.66 mm Hg [study group] and 10.62 ± 1.21 mm Hg [control]; P = 0.013) and mean CRF (9.95 ± 1.47 mm Hg [study group] and 10.76 ± 1.25 mm Hg [control]; P = 0.040) were significantly different between groups. Mean IOPc, IOPg, and CCT were not significantly different between groups. In the subgroup analysis of study cases (oral steroid versus nonsteroid therapy) of CTDs, CRF which was significantly lower in steroid (9.25 mm Hg) compared nonsteroid therapy (10.20 mm Hg) (P = 0.045), whereas, other parameters such as CCT, CH, IOPc, and IOPg were comparable between the two groups (P ≥ 0.05). Conclusion: CH is altered in CTDs which may be an independent risk factor for glaucoma and might underestimate intraocular pressure so CH is an important consideration in patients with CTDs.s

Study of corneal biomechanical properties in patients with childhood glaucoma.

To study of corneal biomechanical properties and intraocular pressure (IOP) measured with Corvis Scheimpflug Technology (ST) in patients with childhood glaucoma (CG). Cross-sectional study in which 89 eyes were included 56 of them with CG. Only one eye per patient was included. The following variables were obtained from the clinical history and the ophthalmological examination: age, sex, IOP, number of surgeries, and the cup/disc ratio (CDR). The following parameters were recorded using Corvis ST: corrected by biomechanics IOP (bIOP), not corrected IOP (nctIOP), central corneal thickness (CCT), maximum concavity [radius, peak distance (PD) and deformation amplitude], applanation 1 and 2 (length and velocity). The mean age was 23±14.55 and 33±19.5 years old for the control group and CG group, respectively. Totally 36 were males and 53 were females. In the CG group, 7 patients were controlled only with medical treatment. Sixteen had at least one previous goniotomy, 19 had at least one trabeculectomy, and 11 had an Ahmed implant. A significant and positive intraclass correlation coefficient was found between Goldman IOP and the IOP measured by Corvis in both groups. No differences were found between the IOP measured with Corvis and Goldman using a student t-test. Regarding biomechanical parameters, there were differences in the applanation length 2 (A-L2), in the applanation velocity 2 (A-V2) and in the PD. By sex, only the applanation length 1 (A-L1) was found to be different in control group. A positive and significant Pearson correlation was found between CDR and the A-L1. Corneal biomechanical properties have shown differences between CG and healthy subjects and also between men and women.

Corneal biomechanical properties in patients with kidney transplant.

PURPOSE:The purpose of the study was to evaluate the corneal biomechanical properties in patients post kidney transplant and to compare them with healthy age-matched control.MATERIALS AND METHODS:In this cross-sectional study, 68 patients with kidney transplant (study group) and 68 healthy individuals (control group) were analyzed with ocular response analyzer measurements. Only the right eye of each participant was assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg).RESULTS:The mean CH in the study group was 9.70 ± 1.62 mmHg which was significantly lower than the control group with the mean CH of 10.60 ± 1.49 mmHg (P = 0.001). The mean IOPcc was 18.17 ± 4.00 mmHg and 16.00 ± 3.94 mmHg in the study and control groups, respectively (P = 0.002). CRF and IOPg were not significantly different between groups.CONCLUSION:CH and IOPccare altered in kidney transplant patients.

Measurement of In Vivo Biomechanical Changes Attributable to Epithelial Removal in Keratoconus Using a Noncontact Tonometer.

To compare the biomechanical properties of the cornea after epithelial removal in eyes with keratoconus undergoing corneal cross-linking. Prospective interventional case series at a university hospital tertiary referral center. Corneal biomechanical properties were measured in patients with keratoconus undergoing corneal cross-linking, immediately before and after epithelial debridement by using a dynamic ultrahigh-speed Scheimpflug camera equipped with a noncontact tonometer. The study comprised 45 eyes of 45 patients with a mean age of 19.6 ± 4.9 years (range 14-34). The cornea was found to be 23.7 ± 15.7 μm thinner after epithelial removal (P < 0.01). Corneal stiffness was reduced after epithelial removal as demonstrated by a significant decrease of parameters such as stiffness parameter A1 (12.31, P < 0.01), stiffness parameter-highest concavity (2.25, P < 0.01), A1 length (0.13 mm, P = 0.04), highest concavity radius of curvature (0.26 mm, P = 0.01), highest concavity time (0.22 ms, P = 0.04) and an increase in A1 velocity (-0.01 m/s, P = 0.01), A1 deformation amplitude (-0.03 mm, P ≤ 0.01), A1 deflection length (-0.32 mm, P < 0.01), A2 deformation amplitude (-0.03 mm, P = 0.01), and A2 deflection length (-1.00 mm, P < 0.01). There were no significant differences in biomechanical intraocular pressure (0.15 mm Hg, P = 0.78), deformation amplitude (0.03, P = 0.54), maximum inverse radius (-0.01 mm, P = 0.57), and whole eye movement length (-0.02 mm, P = 0.12). Dynamic ultrahigh-speed Scheimpflug camera equipped with a noncontact tonometer offers an alternative method for in vivo measurements of the epithelial layer's contribution to corneal biomechanical properties. Our results suggest that corneal epithelium may play a more significant role in corneal biomechanical properties in patients with keratoconus than previously described.

Corneal Biomechanical Properties in Childhood Obesity.

To investigate corneal biomechanical properties in patients with childhood obesity. The study included 47 patients with childhood obesity (study group) and 39 healthy patients (control group). Corneal hysteresis, corneal resistance factor, corneal compensated intraocular pressure (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Ocular Response Analyzer (Reichert, Ophthalmic Instruments, Buffalo, NY) in each eye. Central corneal thickness (CCT), anterior chamber angle (ACA), anterior chamber volume (ACV), and anterior chamber depth (ACD) measurements were obtained by the Pentacam rotating Scheimpflug camera (Oculus Optikgeräte GmBh, Wetzlar, Germany). The mean corneal hysteresis was 10.56 ± 1.52 mm Hg in the study group and 11.16 ± 1.92 mm Hg in the control group (P = .022). The mean IOP was 14.9 ± 2.0 mm Hg in the study group and 14.1 ± 1.3 mm Hg in the control group (P = .003). Corneal hysteresis showed a significant, positive correlation with corneal resistance factor (P < .001, r = 0.851), IOPg (P = .044, r = 0.213), CCT (P < .001, r = 0.477), and IOP (P = .005, r = 0.295). Corneal hysteresis showed a significant, negative correlation with IOPcc (P = .001, r = -0.355), ACA (P = .005, r = -0.294), ACV (P = .019, r = -0.246), and ACD (P = .046, r = -0.211). Patients with childhood obesity have lower corneal hysteresis and higher IOPcc measurements when compared with healthy patients. Corneal tissue changes may occur in early life in childhood obesity, which could lead to ocular disease in the future. [J Pediatr Ophthalmol Strabismus. 2020;57(2):103-107.].

Influence of corneal biomechanical properties on IOP indices in patients with keratoconus

Purpose: Evaluation of corneal biomechanical prop¬erties and their influence on IOP indices in patients with keratoconus. Material and methods. The study included 194 eyes with keratoconus (113 patients aged from 23 to 36 years old). Corneal refraction in central zone varied from 48.25 to 56.75 D, values of corneal thickness ranged from 279 to 558 μm. Patients were divided into 4 groups according to Amsler classification: I stage – 40 eyes; II stage – 78 eyes; III stage – 54 eyes and IV stage – 22 eyes. Standard ophthal¬mological examination was carried out including pneumo¬tonometry. IOP indices and values of biomechanical prop¬erties were evaluated by dynamic bidirectional pneumatic applanation and pneumatic impression. Results. Study of corneal biomechanical properties in patients with keratoconus showed a decrease of such biomechanical indices as corneal hysteresis (CH) on aver¬age to 8.42±1.12 mm Hg, corneal resistance factor (CRF) – to 7.45±0.96 mm Hg, coefficient of elasticity (CE) – 5.35± 0.87 mm Hg. Values of these indices strongly depended on the stage of keratoconus. In the whole sample, the aver¬age corneal compensated IOP (IOPcc) amounted to 15.08± 2.43 mm Hg, Goldman IOP (IOPg) was 11.61±2.37 mm Hg and pneumatic tonometry IOP (IOPp) was 10.13±2.94 mm Hg. IOPcc indices didn’t have any statistically significant differ¬ence in dependence on the stage of keratoconus (р&gt;0.473), while in process of disease progression IOPg and IOPp indi¬ces showed statistically significant decrease of mean values. Conclusion. Progression of keratoconus led to a de¬crease in corneal biomechanical properties which deter¬mine reduction of such indices as IOPg and IOPp in contrast to IOPcc.

Changes in Corneal Biomechanical Properties After Descemet Membrane Endothelial Keratoplasty.

To evaluate the course of corneal biomechanical properties (corneal hysteresis and corneal resistance factor) after Descemet membrane endothelial keratoplasty (DMEK) in patients with Fuchs endothelial dystrophy (FECD). In this prospective study, we consecutively included 49 patients with FECD with an indication for DMEK. Central corneal thickness, measured using the Oculus Pentacam, and corneal hysteresis (CH) and corneal resistance factor (CRF), both measured using the Reichert Ocular Response Analyzer, were examined preoperatively, 3 months, and 6 months after DMEK. CH was significantly increased 6 months postoperatively (8.66 ± 2.50 mm Hg) compared with preoperative baseline (7.43 ± 1.56 mm Hg). Preoperative CRF (7.89 ± 1.68 mm Hg) increased significantly 6 months after DMEK (8.49 ± 1.71 mm Hg). Preoperative central corneal thickness showed a significant decrease from 629 ± 58 μm to 550 ± 40 μm after 3 months and 535 ± 40 μm after 6 months postoperatively. DMEK affects both measured corneal biomechanical properties in patients with FECD: CH and CRF. This has to be taken into account for the accuracy of intraocular pressure measurements.

Comparison of corneal biomechanical properties of patients with dry eye secondary to Sjögren's syndrome and healthy subjects

The goal of this study is to determine whether any difference in corneal biomechanical properties exists between Sjögren's syndrome dry eye patients and healthy subjects. Thirty-one patients diagnosed with Sjögren's syndrome and associated dry eye manifestations and 44 healthy individuals were included in the study. Ultrasonic pachymetry (UP) was used to measure central corneal thickness (CCT). Corneal biomechanical parameters were obtained using ocular response analyzer (ORA). The main parameters assessed were corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg) and corneal compensated IOP (IOPcc). A Student's t-test for independent groups was performed to compare the mean of these variables between both groups. Mean CH values in Sjögren's syndrome and healthy subject eyes were 10.1mmHg and 11.18mmHg respectively, representing a statistically significant difference (P=0.003). No other variable measured differed between cases and controls (P>0.05). Mean CRF values were 9.51mmHg and 10.37mmHg respectively, and mean CCT measured by UP in cases and controls was 527.41μm and 552.51μm respectively. Sjögren's syndrome can influence corneal biomechanical properties, specifically CH. ORA measurements should be considered of interest in the evaluation of Sjögren syndrome subjects.

Corneal biomechanical properties in patients with Hashimoto's thyroiditis.

Hashimoto's thyroiditis (HT) is an autoimmune endocrine disorder that results from a dysregulation of the immune system leading to an immune attack on the thyroid gland. It has potential effects on different organs and tissues. The aim of the study was to investigate the effect of HT on corneal biomechanical properties using the ocular response analyzer (ORA). A total of 48 patients with HT and 49 healthy subjects were enrolled in the study. The mean age of the patients and healthy subjects was 42.33 ±11.96 and 40.20 ±12.60 years, respectively (p = 0.39). All of the subjects underwent a full ophthalmological examination, including visual acuity, corneal pachymetry with topography, biomicroscopy, and funduscopy. Corneal biomechanical properties, including corneal hysteresis (CH) and corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg) and corneal compensated IOP (IOPcc) were measured with the ORA. Central corneal thickness (CCT) in the patient group and the control group were not significantly different (p = 0.65). Corneal hysteresis of the HT patients was significantly lower than that of the control group (p = 0.005). There were no statistically significant differences in CRF between the 2 groups (p = 0.53). Goldmann-correlated IOP and IOPcc were higher in the HT patients, but only IOPcc showed a statistically significant difference (p = 0.001). In conclusion, our data shows that HT affects corneal biomechanical properties by decreasing CH. Thus, IOPcc measured with the ORA should be taken into account when determining accurate IOP values in patients with HT.

Akromegali Hastalarında Korneal Biyomekanik Özellikler

Amaç: Akromegali tanısıyla izlenen hastalarda korneanın biyomekanik özelliklerinin oküler cevap analizörü (OCA) ile belirlenmesi ve sağlıklı kontrol grubu ile karşılaştırılmasıdır. Gereç ve Yöntemler: Çalışmaya 32 akromegali hastası ile yaş ve cinsiyeti eşleştirilmiş 30 kontrol vakası dâhil edildi. Korneal histerez (KH), korneal rezistans faktör (KRF), Goldmann korele göz içi basıncı (GİBg) ve korneal kompanze edilmiş göz içi basıncı (GİBkk) değerleri OCA ile ölçüldü. Santral kornea kalınlıkları (SKK) ultrasonik pakimetre ile belirlendi ve gruplar arası farklar karşılaştırıldı. Bulgular: Akromegalik gözler ile sağlıklı gözlerde bakılan OCA değerleri sırasıyla; KH için 10,35±1,65 mmHg ve 9,17±1,51 mmHg, KRF için 10,35±2,01 mmHg ve 9,04±1,58 mmHg, SKK için 546,81±34,7 ve 521,9±37,1 idi. Akromegali hasta grubunda, sağlıklı bireylere göre ortalama KH, KRF ve SKK değerleri daha yüksek bulundu. Ortalama GİBg ve GİGkk değerleri açısından hasta ve kontrol grubu arasında istatistiksel olarak anlamlı farklılık yoktu. Sonuç: Akromegali hastalığı multisistemik tutulum ile seyrederken, korneada da biyomekanik değişikliklere neden olmaktadır. Korneal elastikiyet ve dirençte meydana gelen değişiklikler ile KH, KRF ve SKK değerlerinde anlamlı değişim gözlemlenmiştir.

Corneal Biomechanical Properties After Penetrating Keratoplasty or Deep Anterior Lamellar Keratoplasty Using the Ocular Response Analyzer: A Meta-Analysis.

To evaluate the corneal biomechanical properties of patients who have undergone penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) using the ocular response analyzer. Stata 13.0 SE was used for this meta-analysis. Studies in the literature that focused on corneal hysteresis (CH) or corneal resistance factor (CRF) after PK or DALK were retrieved by searching PubMed, Embase, Ovid, and Cochrane databases. We present the results as weighted mean difference (WMD) with a corresponding 95% confidence interval (CI). Eight studies with a total of 750 eyes were included in the post-PK versus control group, and 4 studies with a total of 218 eyes were included in the post-DALK versus control group. The pooled results showed that CH and CRF were significantly reduced (P < 0.00001) for patients who have undergone PK (WMD = -1.16, 95% CI: -1.73 to -0.60 and WMD = -1.00, 95% CI: -1.61 to -0.40). No significant differences were found in both CH and CRF for patients who have undergone DALK (WMD = -0.27, 95% CI: -0.64 to -0.09 and WMD = -0.15, 95% CI: -0.53 to 0.23). This meta-analysis suggested that both CH and CRF had better recovery after corneal transplantation with DALK than PK.

The impact of chronic use of prostaglandin analogues on the biomechanical properties of the cornea in patients with primary open-angle glaucoma

AimsTo determine the influence of prostaglandin analogues (PGAs) on corneal biomechanical properties in patients undergoing chronic treatment for primary open-angle glaucoma (POAG).MethodsProspective, interventional case–control study. 70 eyes from 35 patients...

The corneal biomechanical properties of patients with Graves' orbitopathy

This study aims to compare the corneal biomechanical properties of patients with Graves'orbitopathy (GO) with normal people and analysis the correlated factors. Retrospective case series study. 34 eyes of 20 patients (6 eyes are unilateral) diagnosed with inactive Graves' orbitopathy and 25 eyes of 14 patients (3 eyes are unilateral) diagnosed with active Graves' orbitopathy were recruited as study group. 30 eyes of 28 healthy volunteers with age and sex-matched were enrolled as control group in the affiliated eye hospital of Wenzhou medical university from December 2013 to June 2014. Central corneal thickness (CCT) measured with A ultrasound, corneal hysteresis (CH) measured with Ocular Response Analyser (ORA), corneal resistance factor (CRF), Goldman-corrected IOP value (IOPg) and Cornea-Compensated Intraocular Pressure(IOPcc) were collected. An ANONA and Kruskal-Wallis Test was used to compare the indexes mentioned above. The mean age of inactive group was (47.3±12.8)y (23 eyes were female, 11 eyes were male), the mean age of active group was (51.9±9.6)y (16 eyes were female, 9 eyes were male) , the mean age of normal group was (47.2±10.4)y (19 eyes were female, 9 eyes were male). CH of inactive group was (9.68±1.45) mmHg, (1 mmHg=0.133 kPa), CH of active group was (9.82±1.53) mmHg, lower than the CH of (10.67±1.68) mmHg in control group, which was statistically significant different (t1=-2.51,P1=0.014,t2=-2.01,P2=0.048). IOPcc of inactive group was (17.91±3.67) mmHg, IOPcc of active group was (17.88±5.44) mmHg, which were higher than the IOPcc of (13.90±3.39) mmHg in the control group, which was statistically significant different (t1=3.76,P1=0.001;t2= 3.461,P2=0.001). There were no significant difference between study and control group in CRF, that was in inactive group (10.19±1.73)mmHg, active group (10.36±1.01)mmHg, normal group (10.08±1.40)mmHg respectively (t1=0.31,P=0.761;t2=0.69,P2=0.491). CCT of inactive group was (531.41±37.60) μm, CCT of active group is (533.52±18.88) μm, which had no statistical significant difference from the CCT of (546.25±28.84) μm in control group (t1=-1.91,P=0.059;t2=-1.52,P2=0.132). Corneal hysteresis was negatively correlated with exophthalmos, IOPg, IOPcc (Pearson=-0.279,-0.385,-0.663,P<0.05), and positively correlated with corneal central thickness and corneal resistance factor (Pearson=0.246,0.583,P<0.05) in TAO group. Cornea hysteresis of TAO patients decreased, combined with lower ability of cornea to recover to the primary conditions when upon pressure. CH was negatively correlated with IOPg and IOPcc.(Chin J Ophthalmol, 2016, 52: 263-267).

Corneal biomechanical properties in floppy eyelid syndrome.

To determine corneal biomechanical properties in patients with floppy eyelid syndrome (FES) and to compare them with eyes of controls. This case-control study included 208 eyes (72 eyes with FES and 136 without FES) of 107 patients (37 patients with FES and 70 without FES). Patients underwent a complete clinical eye examination that included corneal biomechanical evaluation carried out with the Reichert Ocular Response Analyzer. Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) were evaluated. Mean CH was significantly lower in patients with FES than in those without FES (9.51 ± 1.56 vs. 11.66 ± 9.11; P < 0.001). These results remained statistically significant after adjusting for age and apnea-hypoapnea index (AHI) (P = 0.028). Mean CRF was 10.02 ± 2.08 in the group of patients with FES and 11.21 ± 5.36 in the group of patients without FES (P = 0.001). Mean IOPcc was 17.7 ± 4.8 in patients with FES and 16.3 ± 4.4 in those without FES (P = 0.036). After adjusting for age and AHI, these differences in CRF and IOPcc were not statistically significant (P = 0.26 and P = 0.87, respectively). No statistically significant difference was found between patients with and without FES for Goldmann-correlated intraocular pressure or CCT. Patients with FES had statistically lower CH values. Our findings suggest that corneal biomechanical properties could be changed in patients with FES, reflecting additional structural changes in FES.