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AIM: To assess the differences in corneal biomechanical parameters and their correlation with other ocular biometric parameters in myopic patients using a corneal visualisation scheimpflug technology(Corvis ST).METHODS: A total of 132 myopic patients who received treatment in the department of refractive surgery of Eyegood Ophthalmic Hospital from May to December 2021 were selected, and the data of right eye were taken. The subjects were classified into low and moderate myopia(-0.50 to -6.00D), high myopia(>-6.00D to <-8.00D), and super high myopia(≥-8.00D)according to the spherical equivalent(SE). The basic parameters of corneal biomechanical deformation measured with Corvis ST included the amount of corneal displacement at highest degree of concavity(DA), radius of curvature at highest concavity(HCR), and distance between the two peaks of the cornea at highest concavity(PD); stiffness parameters at applanation 1(SP-A1), integrated radius(IR), deformation amplitude ratio(DA ratio), Ambrosio relational thickness horizontal(ARTh), Corvis biomechanical index(CBI). Other ocular biometric parameters measured included SE, intraocular pressure(IOP), axial length(AL), central corneal thickness(CCT), white-to-white(WTW)and retinal nerve fiber layer(RNFL)thickness. The differences in corneal biomechanical parameters were compared among the three groups of myopic patients, and the correlation between corneal biomechanical parameters and other ocular biometric parameters and age was further analyzed.RESULTS: The SP-A1 in the low and moderate, high, and super high myopia groups were 106.8±16.2, 115.6±21.9, and 106.9±11.5, respectively. The SP-A1 in the high myopia group was higher than that in the low and moderate and severe myopia groups(all P<0.05). All corneal biomechanics were significantly correlated with CCT(P<0.01); all corneal biomechanics were correlated with IOP except ARTh(P<0.05); AL was significantly and positively correlated with PD(r=0.270, P=0.002), weakly and positively correlated with HCR(r=0.177, P=0.043), and weakly and negatively correlated with IR(r=-0.183, P=0.036); WTW was positively correlated with PD, DA and DA ratio(r=0.363, P<0.001; r=0.252, P=0.003; r=0.200, P=0.02); there was no correlation between corneal biomechanical parameters and age, SE, and RNFL.CONCLUSION: Corneal stiffness was higher in high myopia patients than in patients with low to moderate and super high myopia. IOP and CCT were both important factors affecting corneal biomechanics. Some of the biomechanical parameters also have certain correlation with AL and WTW. As the growth of axial length, the PD of corneal deformation and HCR were larger, and IR was smaller, but HCR and IR had little significance; the longer the WTW, the greater the corneal deformation amplitude. In clinical practice, attention should be paid to the corneal biomechanical parameters in patients with super high myopia.
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Laser corneal refractive surgery is an effective way for the correction of myopia, and its long-term stability is a common concern of surgeons and patients. However, refractive regression is still one of the most common postoperative long-term complications, which has a great impact on postoperative refractive state and visual quality. Refractive regression may be related to many factors, such as the remodeling of corneal epithelium and stroma, and the imbalance between corneal biomechanics and intraocular pressure. Although enhancement surgery could be a useful way to correct refractive regression, there is a risk of corneal ectasia and other complications. Some intraocular pressure lowering medications can be used to rebuild the balance of intraocular pressure and corneal biomechanics, and to prevent postoperative refractive regression by affecting the thickness of corneal epithelium. To a certain extent, the type, the timing and the way of intraocular pressure lowering medications application may have an impact on the prevention and treatment effect of refractive regression.
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AIM: To investigate the efficacy of epithelial-off accelerated corneal cross-linking(CXL)in the treatment of advanced keratoconus.METHODS: A retrospective study was performed on data collected from 32 patients(43 eyes)with advanced keratoconus who underwent epithelial-off accelerated CXL at Ningxia Eye Hospital from April 2020 to December 2021. Slit-lamp, intraocular pressure, uncorrected visual acuity(UCVA), corrected visual acuity, specular microscope, Pentacam and Corvis ST were tested before and at 1, 3 and 6mo after surgery. Preoperative and postoperative corneal condition, UCVA, best corrected visual acuity(BCVA)and the values of corneal endothelial, maximum keratometry(Kmax), thinnest corneal thickness(TCT), anterior and posterior surfaces of the cornea K1, K2, biomechanically corrected intraocular pressure(bIOP), applanation time 1(A1T), applanation length 1(A1L), applanation velocity 1(A1V), applanation time 2(A2T), applanation length 2(A2L), applanation velocity 2(A2V), highest concavity deformation amplitude(HCDA), radius at highest curvature(HCR), highest concavity peak distance(HCPD)and stiffness parameter at first applanation(SP-A1)were recorded.RESULTS: There were differences between UCVA(LogMAR; 1.06±0.49, 0.78±0.39)and BCVA(LogMAR; 0.48±0.34, 0.38±0.29)before and at 6mo after surgery(P<0.05), but there were no differences in corneal endothelial cells(2917.39±288.38 vs. 2959.19±336.27 cells/mm2, P=0.477). There were differences among Kmax, TCT, anterior surface K1 and K2 and posterior surface K1 before and after surgery(P<0.05), and all increased at 1mo after surgery then returned to preoperative level at 3mo after surgery, while there was no difference in the posterior K2. Furthermore, there were statistical significance in A1T, HCPD and SP-A1 before and after surgery(P<0.05), while there were no statistical significance in A1L, A1V,A2T, A2L, A2V, HCDA, HCR and bIOP(P>0.05).CONCLUSION: Epithelial-off accelerated CXL can prevent the progression of keratoconus within half year after surgery, and it has certain safety.
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AIM: To explore the differences of corneal biomechanical parameters, serum Leptin and extracellular superoxide dismutase(ecSOD)levels in patients with non-proliferative diabetic retinopathy(NPDR)or proliferative diabetic retinopathy(PDR).METHODS: This article is a prospective study. A total of 118 patients with type 2 diabetes mellitus(T2DM)and diabetic retinopathy(DR)who were admitted to our hospital from May 2020 to May 2022 were selected, and they were divided into NPDR group(n=57)and PDR group(n=61)according to the degree of lesion. Another 54 patients with T2DM but no retinopathy and 52 healthy individuals were set as NDR group and control group. Then the differences in the corneal biomechanics measured with [central corneal thickness(CCT), intraocular pressure(IOP), spherical equivalent(SE), the first applanation time(A1T), the first applanation length(A1L), deformation amplitude(DA)] and serum Leptin and ecSOD levels were analyzed, and multivariate Logistic regression analysis was conducted to analyze the high-risk factors affecting the occurrence of PDR.RESULTS: The CCT, IOP and A1T in PDR and NPDR groups were higher than those in control and NDR groups, and DA was lower than those in control and NDR groups(all P&#x003C;0.05), and the CCT, IOP and A1T in the PDR group were higher than those in the NPDR group(all P&#x003C;0.05). The levels of serum Leptin and ecSOD in PDR group, NPDR group and NDR group were higher than those in the control group(all P&#x003C;0.05). The course of DM, CCT, IOP, A1T, and serum Leptin and ecSOD levels between NPDR group and PDR group were statistically significant(all P&#x003C;0.05). Multivariate Logistic regression analysis denoted that DM course, CCT, IOP, A1T, Leptin, and ecSOD are risk factors that affect the occurrence of PDR, while DA is a protective factor that affects the occurrence of PDR(all P&#x003C;0.05). CONCLUSION: CCT, IOP and levels of serum Leptin and ecSOD in PDR patients were significantly increased compared to those in the NPDR patients, while DA was significantly reduced. Furthermore, CCT, IOP, A1T and levels of serum Leptin and ecSOD were risk factors affecting the occurrence of PDR, while DA was a protective factor affecting the occurrence of the PDR.
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AIM:To evaluate the changes in corneal biomechanics of patients with moderate refractive error after receiving small-incision lenticule extraction(SMILE)and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)using the corneal visualization Scheimpflug technology(Corvis ST).METHODS:Prospective cohort study. A total of 65 moderate myopia patients(65 eyes)who were scheduled to undergo refractive surgery at the Ophthalmic Refractive Surgery Center of the Ningxia Eye Hospital from November 2020 to November 2021 were included in the study, and there were 30 eyes in the SMILE group and 35 eyes in the FS-LASIK group. The changes in corneal biomechanical parameters, including integrated radius(IR), inverse concave radius(ICR), deformation amplitude ratio 2mm(DAR2), stiffness parameter at first applanation(SP-A1), ambrosio relational thickness(ARTh)and the central curvature radius at highest concavity(HC-Radius)were observed by Corvis ST between both groups preoperatively and 1 and 3mo postoperatively.RESULTS: There were no statistical significance in biomechanical parameters between two groups of patients 1 and 3mo postoperatively(P&#x003E;0.05). IR, ICR and DAR2 of each groups of patients 1 and 3mo postoperatively were significantly increased than those preoperatively, and SP-A1, ARTh and HC-Radius were significantly decreased than those preoperatively(all P&#x003C;0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P&#x003E;0.05). In addition, a positive correlation was found between central corneal thickness(CCT)and ARTh and SP-A1 of the two groups of patients at 3mo postoperatively(FS-LASIK group: r=0.727, 0.819, SMLIE group: r=0.683, 0.434, all P&#x003C;0.05), while a negative correlation was found between CCT and IR and ICR at 3mo postoperatively.(FS-LASIK group: r=-0.697, -0.622, SMLIE group: r=-0.447, -0.491, all P&#x003C;0.05).CONCLUSION:For patients with moderate myopia, both SMILE and FS-LASIK can reduce corneal biomechanical stability. Both surgeries showed no significant differences in the effect on biomechanical, and the biomechanical has been stabilized at 1mo postoperatively. A correlation was found between postoperative CCT and ARTh, SP-A1, IR and ICR.
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Purpose: We aimed to assess the impact of drinking water (500 and 1000 mL) on corneal biomechanics and determine the level of association between changes in intraocular pressure and variations in the different biomechanical properties of the cornea. Methods: A total of 39 healthy young adults ingested either 1000 mL (n = 21) or 500 mL (n = 18) of tap water in 5 min. The CorVis ST system was used to assess corneal biomechanics at baseline and at 15, 30, and 45 min after water ingestion. Results: Water drinking induced statistically significant changes in the deformation amplitude (P < 0.001, ?� = 0.166), highest concavity time (P = 0.012, ?� = 0.093), peak distance (P < 0.001, ?� = 0.171), time and velocity of the first applanation (P < 0.001, ?� = 0.288 and P = 0.016, ?� = 0.087, respectively), and time and velocity of the second applanation (P = 0.030, ?� = 0.074 and P = 0.001, ?� = 0.132, respectively), being independent of the amount of water ingested (P > 0.05 in all cases). There were significant associations between changes in intraocular pressure and some parameters of corneal biomechanics. Conclusion: Small variations in whole?body hydration status alter different biomechanical properties of the cornea, with these changes being associated with intraocular pressure levels. These findings indicate that whole?body hydration status can be considered for the diagnosis and management of different ocular conditions.
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@#AIM: To investigate the effects of long-term orthokeratology lens wearing on corneal morphology, corneal biomechanics and objective visual quality.METHODS: A retrospective study was conducted to collect 33 myopic patients(60 eyes), including 19 males(35 eyes)and 14 females(25 eyes), mean age 11.80±1.51 years old, with an average equivalent spherical lens of -3.25±0.69D, who had been wearing orthokeratology lens for 2a from October 2019 to December 2020 in our hospital. Relevant data were collected before wearing and 2a after wearing. The radius of curvature(ARC and PRC), the thickness of the thinnest cornea(THP)and the index of comprehensive deviation analysis of corneal dilation(BADD)were measured by Pentacam anterior segment analysis system. Corvis ST biomechanical analyzer measured non-contact biomechanical corrected intraocular pressure(blOP), maximum deformation amplitude(DA), maximum reverse radius(HCR), ratio of deformation amplitude between apex and 1mm(DR), hardness parameters(SPA1), and corneal biomechanical parameters(CBI). The biomechanical index(TBI)of CT scan was obtained by the combined diagnosis system of Pentacam and Corvis ST. OQAS-II objective visual quality analysis system measured modulation transfer function cutoff frequency(MTF cutoff), Stryl ratio(SR), objective scattering coefficient(OSI)and OV value(OV100%, OV20% and OV9%). The above parameters were compared before and continuously wearing orthokeratoscope for 2a. RESULTS: After 2a of wearing orthokeratology, ARC increased, THP decreased, and BADD increased(<i>t</i>=-9.38, 2.85, -13.08; all <i>P</i><0.05), while there was no significant difference between PRC and before wearing(<i>t</i>=1.49, <i>P</i>>0.05). DA increased and HCR decreased compared with before wearing orthokeratology lens(<i>t</i>=-2.37, 2.28; all <i>P</i><0.05), but bIOP, DR, SPA1, CBI and TBI showed no difference(<i>t</i>=1.36, -1.87, 1.27, -0.95, -1.49; all <i>P</i>>0.05). SR was higher than before, OV20% and OV9% were lower than before(<i>t</i>=-5.31, 8.37, 2.34; all <i>P</i><0.05), MTF cutoff, OSI and OV100% had no difference compared with before(<i>t</i>=-1.57, -1.35, 1.11; all <i>P</i>>0.05).CONCLUSION: Long-term wearing of orthokeratology lens changed the morphology of the anterior corneal surface, but had no significant effect on the corneal biomechanics, and the objective visual quality of patients was improved during the day, but decreased at night.
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@#Diagnosis of early keratoconus(KC)contributes to identifying potential patients before typical clinical symptoms. It also contributes to timely intervention of the progress of disease and improvement of long-term prognosis. Hence, it is crucial to prevent iatrogenic corneal ectasia and reduce the burden of keratoplasty. There are diverse kinds of early KC diagnosis techniques, including corneal topography, corneal aberrations, epithelial and corneal thickness measurement, corneal confocal microscopy, corneal biomechanics, and genetic examination. Since it is often difficult to ensure sufficient sensitivity and specificity with single technique, multiple techniques are beneficial to evaluate the cornea comprehensively, which may become the development tendency of early KC diagnosis in the future.
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Objective:To observe the changes in the biomechanical properties of the cornea of diabetic retinopathy (DR), and analyze its relationship with the degree of DR.Methods:A retrospective study. From September 2020 to February 2021, 83 patients with type 2 diabetes (T2DM) combined with DR treated in the Department of Ophthalmology, The First Affiliated Hospital of Zhengzhou University, 83 eyes (DR group), 30 patients with T2DM without DR recruited from the outpatient clinic 30 eyes (NDR group) and 30 eyes of non-diabetes patients (NDM group) were included in the study. All left eyes were chose as the study eye. Among the 83 eyes in the DR group, 39 eyes were non-proliferative DR (NPDR) and 44 eyes were proliferative DR (PDR). Based on this, they were divided into NPDR group and PDR group. There was no statistically significant difference in age ( t=1.10) and sex ratio ( χ2=0.46) among patients in the DR group, NDR group, and NDM group ( P>0.05); body mass index ( t=3.74), glycosylated hemoglobin ( t=35.02) and the length of the eye axis ( t=5.51), the difference was statistically significant ( P<0.05). The eye response analyzer (ORA) was used to measure the corneal hysteresis (CH), corneal resistance factor (CRF), Goldman related intraocular pressure (IOPg), and corneal compensatory intraocular pressure (IOPcc). The corneal topography was used to measure the central corneal thickness (CCT) of the examined eye. The differences of CCT, IOPcc, IOPg, CH, CRF among multiple groups were compared by one-way analysis of variance. Multiple linear regression was used to analyze the relationship between CH, CRF and related influencing factors in DR patients. Results:There were statistically significant differences in CCT, IOPcc, IOPg, CH, and CRF among the eyes of the DR group, NDR group, and NDM group ( F=3.71, 5.60, 9.72, 9.02, 21.97; P<0.05). Pairwise comparisons were between groups, CH, CRF: the difference between the DR group and the NDM group and the NDR group was statistically significant ( P<0.05); CCT: the difference between the DR group and the NDM group was statistically significant ( P<0.05), and The difference in the NDR group was not statistically significant ( P>0.05). CCT, CH, CRF: the difference between the NDR group and the NDM group was not statistically significant ( P>0.05). The results of multiple linear regression analysis showed that CCT and IOPcc in DR patients were independent influencing factors of CH [CCT: β=0.01, 95% confidence interval ( CI) 0.01-0.03, P=0.013; IOPcc: β=-0.15, 95% CI -0.25--0.05, P=0.005]; Age, CCT, IOPcc were independent influencing factors of CRF [Age: β=-0.06, 95% CI -0.09--0.03, P<0.001; CCT: β=0.01, 95% CI 0.00-0.02, P=0.049; IOPcc: β=0.16, 95% CI 0.07-0.25, P=0.001]. The comparison of CCT, CH, CRF, adjusted CH, and adjusted CRF of the eyes in the NDR group, NPDR group, and PDR group were statistically significant ( F=3.76, 5.36, 12.61, 6.59, 10.41; P<0.05). Pairwise comparison between groups, CH, CRF, adjusted CH, adjusted CRF: the difference between the NPDR group, the PDR group and the NDR group was statistically significant ( P<0.05), and the difference between the PDR group and the NPDR group was not statistically significant ( P>0.05); CCT: The difference between NPDR group and NDR group, PDR group and NPDR group was not statistically significant ( P>0.05), and the difference between PDR group and NDR group was statistically significant ( P<0.05). Conclusion:The CH and CRF of eyes with T2DM and DR are elevated; CCT and IOPcc are independent influencing factors of CH, and age, CCT and IOPcc are independent influencing factors of CRF.
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AIM:To investigate the correlation between corneal biomechanical parameters measured by the corneal visualization Scheimpflug Technology(Corvis ST)and corneal high-order aberrations(HOAs)in children with mild to moderate myopia.METHODS:A cross-sectional study. A total of 255 pediatric patients with myopia enrolled from April to July 2021 in Tianjin Medical University Eye Hospital were continuously collected, and all the right eyes were taken for analysis. Corneal biomechanical parameters were obtained from Corvis ST. Pentacam three-dimensional anterior segment analyzer was used to measure total corneal higher-order aberrations(RMSh), third order aberrations(RMS3)and fourth order aberrations(RMS4).RESULTS:RMS3 was positively correlated with the second applanation time(A2T)(r=0.175, P=0.009)and negatively correlated with the axis length(AL)(r=-0.155, P=0.014). RMS4 was negatively correlated with the highest concavity radius(HCR)(r=-0.165, P=0.009). RMSh was negatively correlated with HCR and AL(r=-0.152, P=0.037; r=-0.175, P=0.005).CONCLUSION:There is a correlation between corneal biomechanical parameters and HOAs in children with myopia. Cornea with higher stiffness and stronger deformation resistance has smaller RMS3, RMS4 and RMSh.
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@#AIM: To investigate the characteristics of corneal stiffness parameters at the first applanation(SP-A1)in keratoconus patients among different age groups and severity classification groups. <p>METHODS: A cross-sectional study. Three hundred and forty-five eyes of 247 consecutive keratoconus patients diagnosed in Henan Eye Hospital were enrolled during September 2018 to December 2020. The mean age was(24.51±6.38)years. According to age, the subjects were divided into ≤20 years group, 21-30 years group and ≥31 years group. The severity of keratoconus was divided into AK1, AK2, AK3 and AK4 by Amsler krumeich(AK)classification method. The visual acuity, corneal flat curvature(K1), corneal steep curvature(K2), average corneal curvature(Km)and the thinnest corneal thickness(TCT)were measured. The SP-A1, intraocular pressure(IOP), deformation amplitude max(DA Max), velocity at the first applanation(A1V), time at the first applanation(A1T), time at the second applanation(A2T), velocity at the second applanation(A2V), biomechanical corrected IOP(bIOP), and Radius were measured by Corneal Visualization Scheimpflug Technology(Corvis ST). The correlation between SP-A1 and other parameters were analyzed by Spearman rank correlation, and one-way ANOVA was used to analyze the difference of SP-A1 among different age groups or disease severity groups. <p>RESULTS: No statistically differences of gender, visual acuity, IOP, K1, K2, Km, TCT and disease severity classification were found among different age groups(<i>P</i>>0.05). The SP-A1 was positively related to age(<i>r</i><sub>s</sub>=0.137, <i>P</i>=0.011). The SP-A1 of keratoconus patients in the ≥31 years group was significantly higher than that in the ≤20 years group and 21-30 years group(<i>P</i><0.05). SP-A1 was negatively correlated with K1, K2 and Km in patients in the ≤20 years group and 21-30 years group, while SP-A1 was negatively correlated with K2 in patients in the ≥31 years group(<i>P</i><0.05). In addition, SP-A1 was negatively correlated with DA Max, A1V and A2T, and positively correlated with TCT, IOP, bIOP, A1T, A2V and Radius. With the increase of disease severity, the SP-A1 values gradually decreased in patients in the ≤20 years group and 21-30 years group(<i>P</i><0.05). The values of SP-A1 between AK1 and AK4, AK2 and AK3, AK2 and AK4 were statistically different(<i>P</i>=0.008, 0.035, 0.001). <p>CONCLUSION: The value of SP-A1 in keratoconus was positively correlated with age. In patients less than 30 years old, the SP-A1 decreased with the increase of disease severity.
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@#AIM: To analyze the effectiveness of transepithelial-corneal collagen cross-linking for 1a after the treatment of progressive keratoconus and discuss its clinical significance. <p>METHODS:A total of 45 cases(48 eyes)of progressive keratoconus who underwent accelerated transepithelial-corneal collagen cross-linking in our hospital from Jan. 2017 to Dec. 2018 were collected. After 1a of postoperative follow-up, the changes of visual acuity, corneal thinnest point thickness, corneal endothelial cell count, corneal cross-linking line depth, Km of anterior corneal curvature and corneal biomechanical parameters before and after surgery were analyzed.<p>RESULTS:Compared with preoperative, the uncorrected visual acuity(UCVA)was improved obviously postoperative in this group patients(<i>P</i><0.05), but the best-corrected visual acuity(BCVA), corneal thinnest point thickness and corneal endothelial cell counts were no significant change(<i>P</i>>0.05). At 6mo and 1a postoperative, Km of anterior corneal curvature(48.54±2.57, 48.77±2.29D)are decreased significantly, the first flatten width of corneal biomechanical parameters(1.52±0.21, 1.57±0.22mm)were significantly lower(<i>P</i><0.05). The absolute value of the second flattening velocity(0.82±0.09, 0.82±0.18m/s)was significantly increased(all <i>P</i><0.05).<p>CONCLUSION:Accelerated transepithelial-corneal collagen cross-linking surgery for progressive keratoconus can significantly improve the UCVA and corneal biomechanics postoperative, but the BCVA was not significantly improved.
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@#AIM: To investigate the corneal biomechanical parameters alteration after phacoemulsitication with 2.4mm corneal incision within 1mo by Corvist ST.<p>METHODS: A self control study was performed. Twenty-eight age related cataract patients(56 eyes), who were in accordance with the inclusion criteria, received phacoemulsification with 2.4mm corneal incision from March to September in 2019. Corneal biomechanical parameters were measured preoperatively and postoperatively on 3d, 6d and 30d by Corvis ST.<p>RESULTS: The first applanation length(A1L), the second applanation time(A2T)and corneal thickness(CCT)were significantly different between preoperation and postoperation(<i>F</i>=10.534, 11.655, 14.734; all <i>P</i><0.05). The value of A1L on 3d postoperative was significantly increased than that on the day before operation, 6d and 30d postoperative, while the A2T value was significantly reduced(<i>P</i><0.05). But there was no different in A2L and A2T between preoperation and 6d postoperative(<i>P</i>>0.05). The value of central corneal thickness(CCT)was significantly increased on 3d and 6d postoperative compared with the preoperative parameter(<i>P</i><0.05). The value of CCT got the maximum value on the 3d after surgery, and recovered to the preoperative level on the 30d after surgery. <p>CONCLUSION: Phacoemulsitication with 2.4mm corneal incision change the corneal biomechanical preoperties. The corneal biomechanical parameters are basically recovered in the 30d postoperative.
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@#AIM: To explore the correlation between corneal biomechanics and corneal densitometry.<p>METHODS: Prospective study. Patients who examined before corneal refractive surgery in the Second People's Hospital of Yunnan Province from March 2019 to June 2019 were selected as research objects. Pentacam HR system was used to evaluate corneal densitometry. The corneal was divided into three areas around the corneal apex with diameters of 0-2mm, >2-6mm, >6-10mm,and the corneal thickness was divided into anterior, middle and posterior layers. The thinnest point thickness of cornea in Pentacam HR was selected to be included in the study. Corvis ST was used to measure the biomechanical parameters, including the first applanation length(AP1L)and applanation velocity(AP1V),the second applanation length(AP2L)and applanation velocity(AP2V),the highest concavity peak distance(PD),highest concavity radius(HCR)and deformation amplitude(DA). Pentacam & Corvis ST comprehensive diagnostic platform software was used to comprehensively analyze the examination results and obtain comprehensive corneal biomechanical parameters(CBI), as well as other independent parameters including stiffness parameters(SP), integrated radius(IR), Ambrosio relational thickness-horizontal(ARTh)and deformation amplitude ratio(DAR). Variance analysis was used for the difference of corneal densitometry in each region, the correlation between corneal biomechanical parameters and corneal densitometry was analyzed by Pearson or Spearman.<p>RESULTS: The difference of optical density between different diameter ranges and different layers was statistically significant(<i>F</i>=35.101, <i>P</i><0.01; <i>F</i>=1002.897, <i>P</i><0.01), CBI was correlated with AP2L,AP2V,PD,DA,SP,IR,ARTh and DAR in the independent biomechanical parameters(<i>r</i>s= -0.502, <i>P</i><0.01; <i>r</i>s=-0.457, <i>P</i>=0.001; <i>r</i>s=0.428, <i>P</i>=0.002; <i>r</i>s=0.539, <i>P</i><0.01; <i>r</i>s=-0.687, <i>P</i><0.01; <i>r</i>s=0.716, <i>P</i><0.01; <i>r</i>s=-0.728, <i>P</i><0.01; <i>r</i>s=0.750, <i>P</i><0.01). CBI was positively correlated with optical density within the range of 0-2mm(<i>r</i>=0.343, <i>P</i>=0.015). The corneal densitometry within a range of 0-2mm is correlated with AP2L, IR, ARTH and DAR in independent biomechanical parameters(<i>r</i>s=-0.298, <i>P</i>=0.035; <i>r</i>s=0.368, <i>P</i>=0.009; <i>r</i>s=-0.419,<i> P</i>=0.002; <i>r</i>s=0.493, <i>P</i><0.01).<p>CONCLUSION: There is a correlation between corneal biomechanics and corneal densitometry in the central region of cornea, which has a more significant correlation with the biomechanics.
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Objective To study the sensitivity and specificity of parameter Corvis biomechanical index (CBI)— a new biomechanical index of Corvis ST in the diagnosis of keratoconus and evaluate the role of CBI in the diagnosis of keratoconus and the change of biomechanic.Methods A diagnostic trial study was adopted,and 66 eyes from 49 keratoconic patients (keratoconus group) and 91 right eyes from 91 myopic patients (control group) from April in 2018 to August in 2018 in Henan Eye Hospital were enrolled.Pentacam and Corvis ST examinations were performed by the same operator after the basic eye examinations.Using the evaluation of diagnostic test,consistency test,and receiver operating characteristic (ROC) curve analysis,gain the outcome of the sensitivity,specificity,consistency,Youden index,and area under the ROC curve of the parameter CBI.This study protocol was approved by Ethic Committee of Henan Eye Hospital and followed the Declaration of Helsinki.Written informed consent was obtained from each patient prior to any medical examination.Results Sixty eyes were diagnosed as keratoconus by the parameter CBI of Corvis ST.Evaluation of diagnosis test:the sensitivity was 97.0％,and the specificity was 97.8％;consistency check:Kappa =0.948,P＜0.05.ROC curve analysis:the sensitivity was 98.5％,the specificity was 96.8％,Youden index was 96.3％,P＜0.000 1 and AUC was 0.996.Conclusions CBI can separate healthy eyes from keratoconic eyes with highly sensitivity and specificity,which was highly consistency with results of Rabinowitz keratoconus diagnostic criteria.CBI could be used as a new biomechanical indicator for the diagnosis of keratoconus.
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Objective To investigate the changes of corneal biomechanics of intrastromal correction (INTRACOR) femtosecond technique to treat presbyopia.Methods A prospective,clinical self-control clinical trial was designed.Twenty-four presbyopic patients with emmetropia or mild hyperopia were enrolled in this study.The INTRACOR procedure was performed using the Technolas femtosecond laser in the nondominant eye.Uncorrected distance visual acuity (UCDVA),uncorrected near visual acuity (UCNVA) and spherical equivalent (SE) were recorded in preoperation and postoperative 12 months,and the quality of life of postoperative patients was evaluated.The corneal deformation parameters including highest concavity deformation amplitude (HC-DA),highest concavity peak distance (HC-PD),highest concavity radius (HC-R),non-contact intraocular pressure and the central corneal thickness (CCT) were measured using the Corvis ST visualization biomechanical analyzer in preoperation and postoperative 1 month,3,6 and 12 months,respectively.This study followed the Declaration of Helsinki.Written informed consent was obtained from each subject prior to entering study cohort.This study protocol was approved by Ethic Committee of Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine (No.SDZYYDXYKYYLL2011.06).Results Compared with preoperation,UCNVA of all 24 (100％) eyes was improved at 12 months postoperatively with minimal or no change in UCDVA.The mean spherical equivalent was (+0.35± 0.29)D and (-0.37 ± 0.29)D before and 12 months after operation,with a significant difference beteeen them (t=-7.39,P＜0.01).No significant differences were seen in the intraocular pressure,CCT and HC-PD values between preoperation and postoperative 1 month,3,6,12 months (F =1.273,1.347,2.434;all at P ＞ 0.05).Compared with preoperation,the postoperative 1 month,3,6,12 months HC-R values were significantly declined,HC-DA values were significantly increased,with significant differences between them (all at P＜0.05),and no significant differences were found in HC-R and HC-DA between the postoperative adjacent time points (all at P＞0.05).Corneal aspherical index (Q Value) was-0.28±t0.10 at 12 months postoperatively,which was increased compared with the preoperation,and the maximum value added value (diff-K) of the central corneal curvature was (2.55±0.81)D.Conclusions INTRACOR treatment of presbyopia can effectively improve near vision,increase postoperative corneal biomechanical maximum HC-R and HC-DA,negatively increase the corneal central curvature increased aspheric index,which suggests that corneal biomechanics of central cornea is weakened after intrastromal femtosecond presbyopic treatment,and the hyperprolate mutifocal corneal shape is formed under normal intraocular pressure.
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Measuring corneal biomechanical properties is still challenging. There are several clinical applications for biomechanical measurements, including the detection of mild or early forms of ectatic corneal diseases. This article reviews clinical applications for biomechanical measurements provided by the Corvis ST dynamic non contact tonometer
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Objective This study was to evaluate the long-term clinical efficiency of allogeneic corneal intrastromal lenticule inlay for correction of moderate and high hyperopia.Methods A prospective self-controlled case series study was adopted.Twenty-nine hyperopic patients (53 eyes) were performed with allogeneic corneal intrastromal lenticule inlays.The range of preoperative spherical equivalent was +3.75 to + 10 D,with the mean value of (+6.84±2.95)D.All the cases were followed up for 1 year.Uncorrected and best corrected visual acuity and refraction were compared between before and after operation.Corneal topography and optical coherence topography were used to examine corneal topography.Ocular response analyzer was used to evaluate the shifts of corneal hysteresis.This study followed the Helsinki declaration,and the research process was approved by the Ethic Committee of Beijing Tongren Hospital,and informed consent was signed by each donor and receptor.Results Compared with the before surgery,the uncorrected distance visual acuity (UDVA) and uncorrected near visual acuity (UNVA) were obviously improved and the spherical equivalent (SE) was obviously decresed in 3 months,6 months and 1 year after surgery,with significant differences between them (all at P＜0.05),but no significant differences were found between each postoperative time points (all at P＞0.05).One year after surgery,14 eyes (26.4％) gained one line of best corrected distance visual acuity (BCDVA),and 12 eyes (22.6％) gained two lines of BCDVA.Only 2 patients (5.66％) lost lines due to opaque lenticules,and no eye lost lines after changing the opaque lenticules.There was no obvious hyperopic fallback phenomenon.Compared with the before surgery,the average corneal curvature value (Avek) was obviously improved,the surface regularity index (SRI),surface asymmetry index (SAI) and central corneal thickness (CCT) were obviously increased in 3 months,6 months and 1 year after surgery,with significant differences between them (all at P＜0.05),but no significant differences were found between each postoperative time points (all at P ＞ 0.05).The cornea optical coherence tomography (OCT) examination showed that,after the operation,the corneal stromal implant was in place and clear.One year after surgery,the dividing line of corneal graft was still clearly visible.No significant changes of corneal hysteresis (CH) and corneal resistance factor (CRF) were seen among different time points before and after surgeries (F =1.443,P =0.216;F =1.744,P =0.128).Conclusions Allogeneic corneal small incision intrastromal lenticule inlays can be used to correct moderate and high hyperopic eye with good safety,effectiveness and predictability.It provides a new choice for hyperopic patients.
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Objective To explore the corneal biomechanical characteristics change in cataractous eyes before and after phacoemulsification using corneal visualization Scheimpflug technology (Corvis ST) and evaluate the influence of 3 mm clear corneal incision on corneal biomechanics.Methods A self-control study was performed.Thirty-six eyes of 36 patients who received phacoemulsification were enrolled in Tianjin Eye Hospital from March to May 2015.The first/second applanation time,the first/second applanation length,the first/second applanation velocity,the highest concavity time,the highest concavity radius,peak distance (PD),deformation amplitude (DA),intraocular pressure,corrected intraocular pressure and central corneal thickness(CCT) were measured in preoperation,postoperative 1 week and postoperative 1 month.This study protocal was approved by Ethic Committee of Tianjin Eye Hospital,and written informed consent was obtained from each patient prior to any medical examination.Results The first/second applanation length,intraocular pressure,corrected intraocular pressure,PD,DA and CCT were significantly different among preoperation,postoperative 1 week and postoperative 1 month (F =3.42,5.24,4.21,3.82,3.91,4.03,3.62;all at P＜0.05).Compared with the preoperative parameters,the first applanation length value was increased,and the second applanation length was reduced;the intraocular pressure and corrected intraocular pressure were elevated,and PD and DA values were increased,and the CCT was thicked in 1 week postoperative,with significant differences between the two time points (all at P＜0.05).Compared with the postoperative 1 week,the first applanation length value was reduced,and the second applanation length value was increased;the intraocular pressure and corrected intraocular pressure were lowed,and PD and DA values were smaller,and the CCT was thinner in postoperative 1 month,showing significant differences between the two time points (all at P ＜ 0.05).The first applanation length,the second applanation length,the intraocular pressure,corrected intraocular pressure,PD,DA and CCT in postoperative 1 month returned to the preoperative levels (all at P ＞ 0.05).Conclusions Corneal biomechanical properties occur change in the early stage after phacoemulsification and return to normal in postoperative 1 month.
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Objective To compare the corneal biomechanical properties between keratoconic eyes and normal eyes by using corneal visualization Scheimpflug technology (Corvis ST),and to evaluate the diagnostic value of corneal biomechanical parameters based on Corvis ST in keratoconus.Methods A prospective cases-control study was performed.Twenty-four keratoconic eyes from 17 patients and 40 normal eyes (right eye) from 40 participants were enrolled from October to December in Peking University First Hospital.Anterior segment parameters and refractive diopters were obtained with Topography (TMS-4) and mydriatic refraction.Biomechanical parameters were assessed with Corvis ST.Independent sample t-test and Wilcoxon rank sum test were used to compare the parameters of the two groups.The receiver operating characteristic (ROC) curves were plotted to distinguish keratoconus from the normal cornea.Diagnostic efficacies of all parameters were analyzed and some parameters were used as independent variables to establish a Logistic regression model.Results Maximum deformation amplitude of highest concavity (HCDA),maximum corneal velocity during the second applanation (Vout) and distance between both non-deformed peaks (PD) in the keratoconus group were higher than those in the normal control group,and first applanation time (A1T),cord length of first applanation (ALL),cord length of second applanation (A2L),radius value of central concave curvature at highest concavity (HCR) were lower than those in the normal control group,with significant differences between the two groups (all at P＜0.05).Maximum corneal velocity during the first applanation (Vin),second applanation time (A2T) and time taken to reach highest concavity (HCT) were insignificantly different between the two groups (all at P＞0.05).Many parameters had diagnostic values in keratoconus assessed by ROC analysis.HCR was the most efficient parameter showed by ROC evaluation (area under the curve was 0.927,sensitivity was 95.8％,specificity was 82.5％).The Logistic model were established with two independent variables,HCR (OR=0.205) and central corneal thickness (CCT) (OR=0.970).The forecast model of keratoconus diagnosis was established as follows:Logistic (P) =23.47-1.59×HCR-0.30×CCT.Diagnostic sensitivity and specificity were enhanced by using this model,the sensitivity was 95.8％,and the specificity was 95.0％.Conclnsions It is useful to evaluate the corneal biomechanical properties with Corvis ST.HCR is an efficient auxiliary testing index of diagnosis or screening of keratoconus.