Short term changes in corneal stress-strain index and other corneal biomechanical parameters post-laser in situ keratomileusis

Purpose:To report the short-term changes in a corneal stress-strain index (SSI) and other corneal biomechanical parameters post-laser in situ keratomileusis (LASIK) surgery.Methods:A retrospective study was conducted at a tertiary eye care center wherein patients who had undergone LASIK (microkeratome blade and femtosecond bladeless LASIK) between July and December 2019 were enrolled. Patients of age group 20–40 years, best-corrected visual acuity of 20/20, intraocular pressure (IOP) <22 mmHg, pre-LASIK pachymetry >500 microns, and corneal astigmatism ≤3.00 D were included. Subjects with a prior history of refractive surgery, any other ocular or systemic disease, poor-quality scans, intraoperative complications, and missing data were excluded. Corneal biomechanical properties including SSI were analyzed using Corvis ST and compared using the Paired T-test for each group separately at pre-LASIK, and 1-month post-operatively.Results:Overall, 202 eyes were reviewed, and 79 eyes fulfilled the inclusion criteria. Forty-three and 36 eyes had undergone Microkeratome Blade LASIK (Group I) and Femto LASIK (Group II), respectively. Overall, 29 and 26 corneal biomechanical parameters out of 33 changed significantly post-Microkeratome Blade LASIK and Femto LASIK, respectively. Statistically significant changes were noted in all the parameters at A1, maximum and Vinciguerra screening parameters (P < 0.001), however, no changes were noted in SSI in both the groups when compared with the pre-surgery data.Conclusion:Though the reduction in SSI was not statistically significant, other biomechanical parameters showed significant biomechanical changes pre- and post-LASIK surgeries in both the groups. However, a long-term study with a larger sample size would be required to understand the changes and stability in SSI post-refractive surgery.     

Corneal biomechanical properties after LASIK,ReLEx flex,and ReLEx smile by Scheimpflug-based dynamic tonometry

Purpose

To evaluate corneal biomechanical properties after LASIK, ReLEx flex, and the flap-free procedure ReLEx smile by Scheimpflug-based dynamic tonometry (Corvis ST) and non-contact differential tonometry (Ocular Response Analyzer, ORA).

Methods

Patients treated for high myopia (?10.5 to ?5.5 diopters, spherical equivalent refraction) more than one year previously at Aarhus University Hospital were included. Treatments comprised LASIK (35 eyes), ReLEx flex (31 eyes), and ReLEx smile (29 eyes). A control group included 31 healthy eyes. Cornea-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured with ORA. Corneal applanation and deformation were registered with Corvis ST during an air-pulse.

Results

Multiple linear regression analysis showed that CH and CRF were significantly lower after all keratorefractive procedures compared to healthy controls (p?<?0.05). No significant differences were observed in CH or CRF between the keratorefractive groups. Corvis ST showed no differences in radius at highest concavity (HC radius), time until first applanation (A1 Time), time until second applanation (A2 Time), and deflection length at highest concavity (HC deflection length) between groups. LASIK treated eyes had significantly shorter time until highest concavity than eyes treated with ReLEx smile (HC Time, p?=?0.01). The A1 deflection length was significantly shorter in the keratorefractive groups compared to the healthy controls (p?<?0.05).

Conclusions

Keratorefrative procedures alter the corneal biomechanical properties with regard to corneal hysteresis and corneal resistant factor. The flap-based LASIK and ReLEx flex and the flap-free ReLEx smile result in similar reduction in corneal biomechanics when evaluated by Corvis ST and ORA.     

Corvis ST评估高度近视患者角膜生物力学参数及其相关因素

目的：利用Corvis ST评估高度近视患者角膜生物力学参数及其相关因素。方法：横断面研究。选取2017 年6-10 月就诊于温州医科大学附属眼视光医院的高度近视患者53 例，其中男17 例，女36 例，年龄18～53（33.0±9.6）岁，均取右眼检测数据。应用Corvis ST测量角膜生物力学参数，包括第1 次压平速率（A1V）、长度（A1L）；第2 次压平速率（A2V）、长度（A2L）以及最大凹陷位置的形变幅度（DA）、曲率半径（HCR）、顶点距离（PD）。比较高度近视患者（-6～-10 D，23 眼）和超高度近视患者（≤-10 D，30 眼）角膜生物力学参数的差异，并分析各参数与年龄、眼压、眼轴长度（AL）、中央角膜厚度（CCT）及视网膜神经纤维层（RNFL）厚度的相关性。数据采用独立样本t检验、Pearson相关进行分析。结果：高度近视组与超高度近视组之间的A2L差异具有统计学意义（t=1.95，P=0.043）。双变量相关分析结果显示眼压与A1V、PD、DA呈负相关（r=-0.56、-0.46、-0.63，P<0.001），与A2V呈正相关（r=0.37，P=0.005）；PD与AL呈正相关（r=0.43，P=0.001）。A1L、A2L、A2V与CCT呈正相关（r=0.33，P=0.043；r=0.28，P=0.041；r=0.39，P=0.003）；角膜压平范围与下方RNFL厚度呈负相关（r=-0.45，P=0.001）。所有参数与年龄不存在相关性。结论：高度近视患者的角膜生物力学与AL、CCT呈正相关，与眼压和RNFL厚度呈负相关，提示高度近视的角膜易发生变形，下方的RNFL受累较严重。     

A cross-sectional study to compare intraocular pressure measurement by sequential use of Goldman applanation tonometry,dynamic contour tonometry,ocular response analyzer,and Corvis ST

Objective:

To study the correlation and effect of sequential measurement of intraocular pressure (IOP) with Goldmann applanation tonometer (GAT), ocular response analyzer (ORA), dynamic contour tonometer (DCT), and Corvis ST.

Setting and Design:

Observational cross-sectional series from the comprehensive clinic of a tertiary eye care center seen during December 2012.

Methods:

One hundred and twenty-five study eyes of 125 patients with normal IOP and biomechanical properties underwent IOP measurement on GAT, DCT, ORA, and Corvis ST; in four different sequences. Patients with high refractive errors, recent surgeries, glaucoma, and corneal disorders were excluded so as to rule out patients with evident altered corneal biomechanics.

Statistical Analysis:

Linear regression and Bland–Altman using MedCalc software.

Results:

Multivariate analysis of variance with repeated measures showed no influence of sequence of device use on IOP (P = 0.85). Linear regression r² between GAT and Corvis ST, Corvis ST and Goldmann-correlated IOP (IOPg), and DCT and Corvis ST were 0.37 (P = 0.675), 0.63 (P = 0.607), and 0.19 (P = 0.708), respectively. The Bland–Altman agreement of Corvis ST with GAT, corneal compensated IOP, and IOPg was 2 mmHg (−5.0 to + 10.3), −0.5 mmHg (−8.1 to 7.1), and 0.5 mmHg (−6.2 to 7.1), respectively. Intraclass correlation coefficient for repeatability ranged from 0.81 to 0.96.

Conclusions:

Correlation between Corvis ST and ORA was found to be good and not so with GAT. However, agreement between the devices was statistically insignificant, and no influence of sequence was observed.     

Ganglion cells apoptosis in diabetic rats as early prediction of glaucoma: a study of Brn3b gene expression and association with change of quantity of NO, caspase-3, NF-κB, and TNF-α

AIM: To find a new concept to show whether or not apoptosis of retinal ganglion cells (RGCs) can be determined in the histology of acute hyperglycemia in the role of expressed Brn3b gene related to nitric oxide (NO), caspase-3, nuclear factor kappa-B (NF-κB), and tumor necrosis factor-α (TNF-α) as an early predictor of primary open angle glaucoma (POAG) eyes and their associations. METHODS: Experimental in vivo study was carried out using adult male, white Sprague-Dawley rats aged ≥2mo, weighing 150-200 g. The animals were divided into two groups, one group receiving intraperitoneal injection of streptozotociz 50 mg/kg in 0.01 mol/L citric buffer and pH 4.5 and a comparison made with the control group. Retinal tissue was divided into two parts (both experimental and control groups respectively): a) right retina for immunohistochemistry (IHC; caspase-3 and TNF-α); b) left retina was divided into two parts for the purpose of real-time polymerase chain reaction (PCR) test (RNA extraction for Brn3b gene expression analysis) and ELISA test (NO and NF-κB). RESULTS: The experimental group showed a decrease in Brn3b gene expression compared to the control group (1.3-fold lower in 2nd month; 1.1-fold lower in 4th month and 2.5-fold lower in 6th month). However, there was a decrease of NO, caspase-3, and an increase of NF-κB and TNF-α quantity. CONCLUSION: The expression of mRNA Brn3b gene is inversely proportional to apoptosis in RGCs. The quantity of NO, caspase-3, NF-κB and TNF-α is influential in expression of Brn3b in RGCs caused by hyperglycemia in diabetic rats.     

Outcomes of photorefractive keratectomy in patients with posterior corneal steepening

PurposeTo assess post-operative outcomes following photorefractive keratectomy (PRK) in patients with posterior corneal steepening compared to an age, gender and refraction matched control group.MethodsA retrospective matched case-control study that analysed outcomes of PRK in eyes with posterior corneal steepening as shown by the Sirius tomography (Sirius, CSO, Italy), versus normal eyes. Both groups were age, gender and refraction matched. Data collected include: demographic data, pre-operative and post-operative refraction, uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), maximal ablation depth. Inferior–superior ratio, central corneal thickness (CCT), mean posterior keratometry (K), Baiocchi Calossi Versaci index for the front (BCV_f) and back (BCV_b) cornea, the symmetry index of front (SI_f) and back (SI_b) corneal curvature were assessed pre- and postoperatively.ResultsOverall, 89 study eyes and 954 normal myopic eyes were included. Compared to the control group, corneas with posterior steepening demonstrated significantly reduced CDVA (p < 0.0001 and p = 0.007) and lower CCT (p < 0.0001 and p = 0.03), before and following the operation, respectively. Pre-operative BCV_f, BCV_b, SI_f and SI_b were significantly higher in corneas with posterior steepening (p < 0.0001) and remained higher following the surgery except for BCV_f. Ectasia occurred in one eye (1.1%). The safety and efficacy indices at 12 months were comparable for both groups.ConclusionPRK on corneas with posterior steepening results in similar refractive outcomes compared to normal eyes, 1 year following the surgery. Keratectasia is a rare, however a possible complication.Subject terms: Outcomes research, Corneal diseases     

Repeatability and reliability of measurements obtained by the combined Scheimpflug and Placido-disk tomography in different stages of keratoconus

ObjectiveThe objective of this study is to evaluate the repeatability and reliability of corneal parameters in different stages of keratoconus patients using a combined Scheimpflug–Placido disc analysis system.Materials and methodsIn this prospective study, three consecutive measurements were performed by the same observer using Scheimpflug–Placido disc anterior segment analysis device in keratoconus patients. Flattest and steepest simulated keratometry and corneal volume, corneal aberrations, thinnest corneal thickness, symmetry index, keratoconus vertex and Baiocchi–Calossi–Versaci index were recorded. Keratoconic eyes were divided into four stages using the Amsler–Krumeich classification. Repeatability was evaluated using within the subject standard deviation, repeatability index (Ri) and coefficient of variation; reliability was evaluated by intraclass correlation coefficient (ICC). Pearson correlation coefficients were used to assess the correlation between the parameters evaluated.ResultsTwo hundred sixty-one eyes of 261 keratoconus patients were included in the study. The repeatability for all corneal curvature parameters decreased as the keratoconus severity increased, and there is a positive correlation between keratometry of the apex and corneal curvature parameters (p < 0.05) except mean simulated keratometry. The corneal aberrations were repeatable in all keratoconus subgroups (Ri < 0.34 μm). There are also positive correlations between keratometry of apex and corneal aberrations (p < 0.05) except total high-order root mean square and spherical aberration. The reliability was excellent (ICC > 0.90) for all indices except keratoconus vertex back.ConclusionThe parameters used in the diagnosis and follow-up of keratoconus in the Sirius corneal tomography system may differ more than expected at stages 3 and 4 of the disease. Awareness of this situation may be helpful in planning follow-up and treatment.Subject terms: Outcomes research, Corneal diseases     

Biomechanical Glaucoma Factor and Corneal Hysteresis in Treated Primary Open-Angle Glaucoma and Their Associations With Visual Field Progression

PurposeTo investigate the relationship between biomechanical glaucoma factor (BGF) measured with Corvis ST and glaucomatous visual field (VF) progression, compared to corneal hysteresis (CH) measured with ocular response analyzer using a longitudinal dataset of primary open-angle glaucoma (POAG). The discriminative powers of BGF and CH were also compared using a cross-sectional dataset.MethodsThe longitudinal dataset included 166 POAG eyes. The rate of VF change during the follow-up period was evaluated using the mean of 52 pointwise total deviations in the Humphrey 24-2 field test. Variables associated with the VF progression rate were identified from BGF, CH, age, baseline VF severity, and intraocular pressure during the VF follow-up period by identifying the optimal model. The cross-sectional dataset included 68 POAG eyes and 68 healthy eyes. Using this dataset, the area under the curve (AUC) values of the receiver-operating curve were compared between CH and BGF.ResultsThe optimal multivariate linear mixed model to describe the VF rate included age and CH, but not BGF. Between POAG and healthy eyes, CH was statistically different (P < 0.001), although this was not the case with BGF. The AUC values were 0.61 and 0.71 for BGF and CH, respectively (P = 0.027).ConclusionsCH, but not BGF, was associated with VF progression in POAG patients under treatment. BGF was not useful to discriminate POAG between treated and normal eyes.     

Evaluating target intraocular pressures in primary congenital glaucoma

Purpose:The aim of this study was to evaluate long-term intraocular pressures that provide stabilization/reversal of glaucomatous neuropathy after surgery in primary congenital glaucoma (PCG).Methods:Prospective evaluation of consecutive PCG patients who underwent trabeculectomy-trabeculotomy and followed up for ≥2 years. Records of regularly performed examination under anesthesia were maintained to ascertain intraocular pressure, (IOP), fundus, refraction and corneal diameter. Outcomes – Primary: cup: disc ratio and intraocular pressure, Secondary: corneal changes and refractive errorResults:A total of 174 eyes of 108 children with PCG had a preoperative IOP of 22.44 ± 9.5 mm Hg. Postoperative review IOP was 11.8 ± 4.5 mm Hg, cup-disc-ratio was 0.52 ± 0.23 and corneal diameter was 12.75 ± 0.9 mm. Primary outcomes: Linear regression analysis showed a significant positive correlation of review IOP with cup disc ratio, P = 0.004. 67.9%, of eyes at a review IOP range of 6-12 mm Hg showed reversal, 14.1%, were stable, at 6-15 mm Hg, while 3.84% showed an increase in cup: disc ratio 16-22 mm Hg. Patients operated before 6 months of age had a significantly smaller final cup-disc ratio, P = 0.0013. Patients with a final cup: disc ratio of >0.9 were significantly older at surgery, P < 0.001. Secondary outcomes: There was a positive correlation of final myopia with review IOP on linear regression analysis, P = 0.012. The final spherical error in eyes having cup disc ratio of ≤ 0.5 was –0.96 ± 4.5 diopters, as against -3.45 ± 7.7 diopters in eyes having cup-disc ratio of 0.6-0.8 and -3.8 ± 6.9 diopters in eyes with cup disc ratio of ≥0.9, P = 0.015. There was no significant change in corneal diameter.Conclusion:Patients operated after 6 months of age had a larger final cup: disc ratio, while postoperative review intraocular pressures over 2 years of at least ≤15 mm Hg in primary congenital glaucoma eyes, commonly lead to reversal/stability of the neuropathy, and a lower incidence and degree of myopia.     

Effect of corneal stromal pocket irrigation in small-incision lenticule extraction

ObjectivesTo investigate the effect of corneal stromal pocket irrigation after small-incision lenticule extraction (SMILE) on visual acuity, intraocular pressure (IOP), corneal parameters and complications after surgery.MethodsA total of 242 eyes of 121 patients undergoing SMILE were enrolled in this prospective controlled study, and it was designed for one eye to randomly undergo SMILE with balanced salt solution irrigation of the corneal stromal pocket, while the other eye was not. The uncorrected distance visual acuity (UDVA) and slit lamp examination were recorded at 1 hour, 1 day, 1 week, and 1 month. Postoperative corneal density, corneal biomechanical, corneal endothelial cell number, and anterior OCT images were compared at 1 day, 1 week, and 1 month.ResultsCompared with the nonirrigation group, the irrigation group showed significantly higher UDVA at 1 day postoperatively (P < 0.05), but there was no significant difference during the rest of the postoperative period (1 hour, 1 week, and 1 month). In addition, no significant differences were found in IOP, corneal density, corneal biomechanics, corneal endothelial cells, and corneal morphology. No visual decline or severe postoperative complications were found in the patients in this study.ConclusionsInterlamellar irrigation did not affect IOP, corneal parameters, morphology, complications, or UDVA at 1 hour, 1 week, and 1 month after the operation, but it may promote UDVA 1 day after the operation.Subject terms: Refractive errors, Outcomes research, Surgery     

Distribution of corneal and ocular spherical aberrations in eyes with cataract in the Taiwanese population

Purpose:

To investigate the distribution of corneal and ocular spherical aberrations (SAs) in eyes with cataract in the Taiwanese population.

Methods:

Corneal and ocular SAs were measured in the central 6-mm optical zone using wavefront aberrometry. Axial length (AL) and keratometry (K) were also evaluated in each eye.

Results:

A total of 413 eyes in 234 patients were analyzed. The mean age of the patients was 66.8 ± 10.64 years. The mean AL and K values were 24.32 mm and 44.08 D, respectively. The mean corneal SA was 0.307 ± 0.135 μm and ocular SA was −0.042 ± 0.487 μm. Ocular and corneal SAs were significantly correlated (r² = 0.04, p < 0.001). Corneal and ocular SAs were not significantly correlated with K (p = 0.096 and p = 0.634, respectively), but were significantly correlated with AL (p < 0.001). Multilinear regression showed that corneal SAs and age were the dependent variables that predicted ocular SAs (r² = 0.143, F = 13.65, p < 0.01), especially in patients who were aged > 50 years, for whom a strongly significant positive correlation was found (r² = 0.102, F = 11.10, p < 0.001).

Conclusion:

Corneal and ocular SAs varied among cataract patients and correlated with AL. After 50 years of age, ocular SAs increased significantly because of an increase in internal (lenticular) SAs. Corneal SAs in Taiwanese patients were larger than those in Japanese patients and similar to those in Chinese and Malaysian populations. Preoperative measurement of wavefront aberrations is necessary to select which aspherical intraocular lenses are most suitable for achieving better postoperative visual quality.     

Prognostic factors of visual quality after transepithelial photorefractive keratectomy in patients with low-to-moderate myopia

Purpose:The aim of this study was to evaluate visual quality after high-frequency transepithelial photorefractive keratectomy (t-PRK) by assessing the relationship between the operational parameters and the first-year postoperative corneal higher-order aberrations (HOAs).Methods:This was a retrospective study of low-to-moderate myopic eyes treated with t-PRK. The files of 46 low-to-moderate myopic patients (90 eyes; myopia up to −5D) were included in the study. Eyes having a cylindrical refractive error more than 2D and the patients not having completed a 1-year follow-up were excluded from the study. Factors including age, preoperative mean spherical equivalent (MSE), mean keratometry (Km), central corneal thickness (CCT), scotopic pupil, optical zone (OZ), transition zone (TZ), ablation zone (AZ), central ablation depth (CAD), and static cyclotorsion correction (SCC) were analyzed for association with the first-year postoperative corneal HOAs.Results:Corneal HOAs were found to be increased postoperatively with a 6-mm pupil (P < 0.05). The increased spherical aberration had a positive correlation with patient age, preoperative MSE, Km, TZ, and CAD, whereas it had a negative relationship with OZ and AZ (P < 0.05). The corneal coma had a significantly positive correlation with preoperative MSE and a significantly negative relationship with OZ (P < .05).Conclusion:Postoperatively induced corneal HOAs may affect patients'' scotopic vision (night time driving, cinema) when the pupils get larger. The relationship between patient age, preoperative MSE, Km, CAD, TZ, OZ, AZ, and postoperative corneal HOAs underlines the need to consider the effects of these parameters on the final vision quality.     

Cataract surgery in eyes with associated coloboma: Predictors of outcome and safety of different surgical techniques

Purpose:The aim of this study was to report the outcome of cataract surgery with different surgical techniques in eyes with coexisting coloboma and to define factors of prognostic importance.Methods:Retrospective case sheet review of patients presenting between January 2016 and December 2018, who underwent cataract surgery in eyes with coexisting coloboma.Results:Of the 3,30,231 cases operated during the study period, 280 eyes of 276 patients had associated colobomatous malformation. The prevalence of coloboma in eyes undergoing cataract surgery was 0.085%. The mean age of the patients was 46.4 years (range 19 - 88 years). Phacoemulsification (PE) was performed in 130 eyes (46.4%), manual small incision cataract surgery (M-SICS) was done in 115 eyes (41.1%), and 35 eyes (12.5%) underwent intra capsular cataract extraction. Intra-operative complications were noted in 26 (9%) eyes. Incidence of intra-operative and post-operative complications was comparable between PE and M-SICS groups (p = 0.94). The mean corrected distance visual acuity (CDVA) improved from logMAR 1.71 ± 0.62 to 0.87 ± 0.61 (p = 0.00009). On multivariate analysis, microcornea (p = 0.002), type 1 and 2 coloboma (p < 0.001), and intraoperative complications (p = 0.001) were associated with poor visual outcome.Conclusion:Favorable functional outcomes can be achieved with phacoemulsification in eyes with softer cataract and corneal diameter >8 mm and with M-SICS in eyes with hard cataracts and corneal diameter of 6–8 mm. PE should be considered as the primary choice whenever permissible by the corneal diameter and severity of nuclear sclerosis. Poor functional outcomes were seen in eyes with smaller corneal diameter, extensive chorioretinal coloboma, and intraoperative complications.     

Evaluation of the White-to-White Distance in 39,986 Chinese Cataractous Eyes

PurposeTo investigate the distribution of white-to-white (WTW) distance and its associations with other biometric parameters in Chinese cataractous eyes.MethodsData on 39,986 eyes from 23,627 Chinese cataract patients were analyzed. Ocular biometric parameters, including WTW distance, corneal curvature, anterior chamber depth (ACD), lens thickness (LT), central corneal thickness (CCT), and axial length (AL), were obtained using the ZEISS IOLMaster 700.ResultsThe mean age of patients was 63.7 ± 12.4 years, and 57.61% were female. The mean WTW distance was 11.69 ± 0.46 mm. The WTW distance was larger in male patients than in female patients for all age groups (all P < 0.001). The WTW distance was positively correlated with corneal curvature and ACD and negatively correlated with age, LT, and CCT (all P < 0.001). Multivariable analysis revealed that a larger WTW distance was associated with younger age; male gender; larger corneal curvature, ACD, and LT; and thinner CCT (all P < 0.001). Notably, the association between WTW distance and AL was not linear. As the AL increased, the WTW distance initially increased, reached a peak in the group with ALs of 24.5 to 26 mm, and then slowly decreased. However, all of the myopic eyes (AL > 24.5 mm) still had larger WTWs than the normal and short eyes (AL ≤ 24.5 mm).ConclusionsIn Chinese cataractous eyes, the WTW distance was larger in younger male patients with flatter corneas, deeper anterior chambers, thicker lenses, and thinner central corneas. The association between WTW distance and AL was not linear, and WTW distance was the largest in eyes with ALs of 24.5 to 26 mm.     

A comparative study on endothelial cell loss in nanophthalmic eyes undergoing cataract surgery by phacoemulsification

Purpose:The purpose of this study is to compare the endothelial cell loss (ECL) in nanophthalmic eyes and age-matched controls undergoing cataract surgery by phacoemulsification and also to identify the risk factors influencing the endothelial cell density (ECD). This was a prospective comparative interventional case series.Methods:We enrolled 19 nanophthalmic eyes (study group) and 42 age-matched cataract controls (control group) undergoing phacoemulsification after meeting the inclusion criteria. Ocular parameters like best-corrected visual acuity, intraocular pressure, pachymetry, specular microscopy, and slit lamp findings were noted preoperatively and at month 1 and 3 postsurgery. All nanophthalmic eyes underwent cataract surgery with concomitant prophylactic posterior sclerostomy.Results:The median percentage endothelial loss in nanophthalmic eyes was 4.0 (IQR 0–23.5), 7.4 (IQR 1.0–-22.4) at 1 and 3 months postoperatively compared to 6.3 (IQR 1.7–14.1) and 6.4 (IQR 2.6–-12.1) in age controlled normal eyes (P = 0.94, P = 0.46, respectively). Linear regression analysis showed increasing age as the only variable influencing the percentage decrease in corneal ECD in the study group (P = 0.001). Nanophthalmic eyes with ACD <2.5 mm had a significantly greater reduction in ECD at 3 months postcataract surgery compared to baseline (P = 0.039). Visual outcomes and IOP reduction in the study group with ACD >2.5 mm were significantly better postcataract surgery (P = 0.02 and P = 0.002, respectively).Conclusion:The percentage of ECL in nanophthalmic eyes undergoing phacoemulsification is equivalent to normal eyes. However, in the nanophthamic eyes with AC depth <2.5 mm, the percentage cell loss was significantly higher warranting the need for extensive intraoperative care. Increasing age was found to be the only significant risk factor influencing the ECD in short eyes.     

单纯近视患者Corvis ST测定的角膜形变参数与角膜形态学参数的相关性

背景 Corvis ST生物力学眼压测量仪(Corvis ST)可测得角膜形变的参数,同时可记录角膜受力时的动态变化过程,对近视眼行角膜屈光手术前后角膜结构和功能的预测具有重要的临床意义,但单纯近视眼角膜各形变参数的测定值范围及意义有待研究. 目的 利用Corvis ST测量近视眼角膜形变参数值范围并分析其临床意义,为角膜屈光手术的术前筛查及术后稳定性、安全性的预测等提供参考.方法 采用描述性研究方法,纳入2014年6月至2015年1月在天津市眼科医院拟行角膜屈光手术的单纯近视眼患者257例477眼,所有受检眼均采用Corvis ST测定角膜形变参数,包括第1次压平时间(1stA-time)、角膜长度(1stA-length)和压平速度(1stA-velocity),第2次压平时间(2ndA-time)、角膜长度(2ndA-length)和压平速度(2ndA-velocity),产生最大压陷的时间(HC-time)和最大压陷时的变形幅度(HC-DA)、峰距(HC-PD)、反向曲率半径(HC-R),非接触式眼压(IOPnct)和中央角膜厚度(CCTst);用Pentacam三维眼前节分析诊断系统(Pentacam)检查受检眼结构参数CCT和角膜曲率;用眼反应分析仪(ORA)测定受检眼角膜生物力学参数,包括角膜阻力因子(CRF)、角膜滞后量(CH)、模拟Goldmann眼压(IOPg)和角膜补偿眼压(IOPcc).对上述参数值行Shapiro-Wilk正态性检验并计算各参数总体均值的95％可信区间(CI);用Pearson线性相关分析或Spearman秩相关分析法对角膜形变参数与角膜结构参数及角膜生物力学参数的相关性进行分析;采用多元线性回归法分析1stA-time、2nd A-time和HC-DA随着各角膜形态学及角膜生物力学参数的变化. 结果 角膜形变参数中仅1stA-time、2nd A-time、HC-time、HC-DA、CCTst和IOPnct服从正态分布;1stA-time、1stA-length、2ndA-length、2ndA-velocity、HC-R与CCT值间均呈正相关(r=0.338、rs=0.129、rs=0.282、rs=0.374、r=0.306,均P＜0.01),而1stA-velocity、2ndA-time、HC-DA及HC-PD与CCT均呈负相关(rs=-0.235、r=-0.130、r=-0.259、r=-0.226,均P＜0.01).CRF和CH与1stA-time、2ndA-length、2ndA-velocity、HC-time、HC-R均呈正相关(均P＜0.05),而与HC-PD、△A-length均呈负相关(均P＜0.05).1stA-time、2nd A-time和HC-DA均随着CRF和IOPcc改变发生变化,回归方程分别为1stA-time=6.185+0.066CRF+0.034IOPcc(F=300.123,P=0.000)、2ndA-time=23.397-0.074I0Pcc-0.044CRF(F=227.979,P=0.000)和HC-DA=1.523-0.017IOPcc-0.017CRF(F=152.662,P=0.000).Corvis ST测得的CCTst值、IOPst值和IOPnct值均明显低于Pentacam测得的CCT[(548.23±26.31) μm]和ORA测得的IOPg值[(15.02±2.72) mmHg](1 mmHg =0.133 kPa)和IOPcc值[(16.02±2.56) mmHg],差异均有统计学意义(t=11.00、2.919、6.815,均P＜0.01).结论 Corvis ST测定的单纯近视眼的角膜形变参数可客观定量描述角膜生物力学特性,IOP及角膜3 mm区陡中心曲率(K2)均可影响角膜的形变反应,Corvis ST在测量CCT及IOP方面的可信度有待进一步研究.     

Reproducibility and clinical relevance of the ocular response analyzer in nonoperated eyes: corneal biomechanical and tonometric implications

PURPOSE: To assess the reproducibility of the ocular response analyzer (ORA) in nonoperated eyes and the impact of corneal biomechanical properties on intraocular pressure (IOP) measurements in normal and glaucomatous eyes. METHODS: In the reliability study, two independent examiners obtained repeated ORA measurements in 30 eyes. In the clinical study, the examiners analyzed ORA and IOP-Goldmann values from 220 normal and 42 glaucomatous eyes. In both studies, Goldmann-correlated IOP measurement (IOP-ORAg), corneal-compensated IOP (IOP-ORAc), corneal hysteresis (CH), and corneal resistance factor (CRF) were evaluated. IOP differences of 3 mm Hg or greater between the IOP-ORAc and IOP-ORAg were considered outcome significant. RESULTS: Intraexaminer intraclass correlation coefficients and interexaminer concordance correlation coefficients ranged from 0.78 to 0.93 and from 0.81 to 0.93, respectively, for all parameters. CH reproducibility was highest, and the IOP-ORAg readings were lowest. The median IOP was 16 mm Hg with the Goldmann tonometer, 14.5 mm Hg with IOP-ORAg (P < 0.001), and 15.7 mm Hg with IOP-ORAc (P < 0.001). Outcome-significant results were found in 77 eyes (29.38%). The IOP-ORAc, CH, and CRF were correlated with age (r = 0.22, P = 0.001; r = -0.23, P = 0.001; r = -0.14, P = 0.02, respectively), but not the IOP-ORAg or IOP-Goldmann. CONCLUSIONS: The ORA provides reproducible corneal biomechanical and IOP measurements in nonoperated eyes. Considering the effect of ORA, corneal biomechanical metrics produces an outcome-significant IOP adjustment in at least one quarter of glaucomatous and normal eyes undergoing noncontact tonometry. Corneal viscoelasticity (CH) and resistance (CRF) appear to decrease minimally with increasing age in healthy adults.     

角膜生物力学分析仪测量近视患者中央角膜厚度和眼压的准确性评价

背景 Corvis ST角膜生物力学分析仪(Corvis ST)能测量角膜生物力学指标、眼压和中央角膜厚度(CCT),且测量的眼压值为校正CCT和生物力学因素的修正值,在国外已用于临床,但目前对中国人群CCT和眼压测量准确性的研究报道较少. 目的 评估Corvis ST测量近视患者CCT和眼压的准确性,为其临床应用提供参考.方法 采用诊断性试验方法,对2012年11-12月在广西视光中心准分子激光门诊行术前检查的56例近视患者进行Corvis ST、Goldmann压平式眼压计(GAT)和A型超声检查,采用配对t检验法比较Corvis ST测量CCT值与A型超声测量结果的差异及Corvis ST测量眼压值与GAT测量结果的差异,采用Bland-Ahman法评价不同测量方法测量结果的一致性.结果 Corvis ST测得的CCT值为(539.82±19.79) μm,高于A型超声测量的CCT值(535.34±19.41) μm,两者比较差异有统计学意义(t=4.19,P＜0.01).Corvis ST测得CCT均值较A型超声测量均值高4.5 μm,95％的一致性界限为-11.2 ～20.2 μm,7.1％ (4/56)的点在95％的一致性界限以外.Corvis ST和GAT测得的眼压值分别为(15.75±1.60)mmHg(1 mmHg=0.133 kPa)和(16.23±2.40)mmHg,两者比较差异有统计学意义(t=2.15,P=0.04).Corvis ST测得的眼压均值较GAT测得均值低0.5 mmHg,95％一致性界限为-3.8 ～2.8 mmHg,3.57％ (2/56)的点在95％一致性界限以外. 结论 Corvis ST测量的CCT稍高于A型超声,2种检测仪器测量的CCT结果一致性较差,临床上不可互相代替.Corvis ST测量的眼压值稍低于GAT,二者测量值具有较好的一致性,临床上可以互相替代.     

Corneal biomechanics measured with the ocular response analyser in patients with unilateral open‐angle glaucoma

Purpose: To evaluate the relationship between biomechanical properties of the cornea and intraocular pressure (IOP) and the role of biomechanical properties in eyes of patients with unilateral primary open‐angle glaucoma (POAG). Methods: The biomechanical properties of corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ocular response analyser (ORA). In an experimental setting, three human donor eyes with Schiotz‐tonometry‐controlled IOP were investigated. In addition, a series of patients with unilateral POAG were evaluated. Main outcome measures were CH, CRF, corneal‐compensated IOP (IOPcc), standard automated perimetry parameters mean defect (MD) and pattern standard deviation, central corneal thickness, Goldmann applanation tonometry (GAT), and cup‐to‐disc ratio. Results: A highly significant linear correlation between CH and the corneal‐compensated IOP (IOPcc, r = ?0.926; p < 0.001) was found. The correlation between IOP_CC and CRF was not significant (r = 0.335; p = 0.08). In total, 36 eyes of 18 patients with unilateral POAG were examined. Regarding uncorrected CH (mean 7.73 ± 1.46 mmHg glaucomatous eye and 9.28 ± 1.42 mmHg fellow eye), there was a highly significant difference between both eyes. This difference disappears, when CH was corrected for IOP (9.44 ± 3.78 mmHg and 9.97 ± 3.22 mmHg, respectively). Conclusions: Corneal hysteresis but not corneal resistance factor is dependent on IOP. In patients with unilateral POAG, IOP is higher in the affected eye. When CH is corrected for IOP, corneal biomechanical properties do not differ in both eyes of patients with unilateral POAG.     

Efficacy of Hyperbaric Oxygen Therapy on Central Corneal Thickness,Intraocular Pressure,and Nerve Fiber Layer in Patients with Type 2 Diabetes: A Prospective Cohort Study

PurposeTo evaluate the effect of hyperbaric oxygen therapy (HBOT) on central corneal thickness (CCT), intraocular pressure (IOP), and the retinal nerve fiber layer (RNFL) thickness in patients with type 2 diabetes mellitus.MethodsThis prospective non-randomized cohort study consisted of type 2 diabetes mellitus patients who received 30 sessions of HBOT for diabetic foot ulcer. The CCT, IOP, and RNFL measured at baseline, after the 10th session of HBOT, after the 20th session of HBOT, after the 30th session of HBOT, and after the 3 months of the last session of HBOT. We gained the superior-nasal, superior-temporal, inferior-nasal, inferior-temporal, nasal and temporal quadrant RNFL values with a spectral-domain optical coharence tomography.ResultsForty-six eyes of 46 patients included in the study. During the study period, a statistically significant increase in mean IOP values compared to baseline was observed (p < 0.001). We found no significant changes at CCT and all quadrants of RNFL values during HBOT and after 3 months of the treatment (p > 0.05). During the study period, the IOP levels increased over 21 mmHg (between 22 and 28 mmHg) in seven eyes (15.2%). The mean hemoglobin A1c values of these patients with IOP >21 mmHg were 8.2 ± 0.9 mg/dL, and there was significant differences compared with those of patients with IOP values ≤21 mmHg (7.4 ± 2.8 mg/dL) (p = 0.001).ConclusionsHBOT increase IOP in type 2 diabetic patients especially in ones with impaired blood glucose regulation. However, it does not cause any changes in CCT and RNFL. As diabetic retinopathy and diabetic foot ulcer are in common pathologies, thus this brief report concludes a need for further studies with longer follow-up periods to explore the potential interaction of HBOT on CCT, IOP, and RNFL.