Nondestructive quantification of analyte diffusion in cornea and sclera using optical coherence tomography

PURPOSE: Noninvasive functional imaging, monitoring, and quantification of analytes transport in epithelial ocular tissues are extremely important for therapy and diagnostics of many eye diseases. In this study the authors investigated the capability of optical coherence tomography (OCT) for noninvasive monitoring and quantification of diffusion of different analytes in sclera and cornea of rabbit eyes. METHODS: A portable time-domain OCT system with wavelength of 1310 +/- 15 nm, output power of 3.5 mW, and resolution of 25 mum was used in this study. Diffusion of different analytes was monitored and quantified in rabbit cornea and sclera of whole eyeballs. Diffusion of water, metronidazole (0.5%), dexamethasone (0.2%), ciprofloxacin (0.3%), mannitol (20%), and glucose solution (20%) were examined, and their permeability coefficients were calculated by using OCT signal slope and depth-resolved amplitude methods. RESULTS: Permeability coefficients were calculated as a function of time and tissue depth. For instance, mannitol was found to have a permeability coefficient of (8.99 +/- 1.43) x 10(-6) cm/s in cornea and (6.18 +/- 1.08) x 10(-6) cm/s in sclera. The permeability coefficient of drugs with small concentrations (where water was the major solvent) was found to be in the range of that of water in the same tissue type, whereas permeability coefficients of higher concentrated solutions varied significantly. CONCLUSIONS: Results suggest that the OCT technique might be a powerful tool for noninvasive diffusion studies of different analytes in ocular tissues. However, additional methods of OCT signal acquisition and processing are required to study the diffusion of agents of small concentrations.     

Assessment of central corneal thickness using optical coherence tomography

PURPOSE: To demonstrate the capability of model OCT3 optical coherence tomographer to evaluate central corneal thickness (CCT) in normal human corneas in vivo and compare the results with the those of standard ultrasound (US) pachymetry and Orbscan. SETTING: New York Eye & Ear Infirmary Resident Clinic, New York, New York, USA. METHODS: The CCT in 22 eyes of 11 subjects was determined with the OCT3 (Carl Zeiss Meditec), Orbscan (Bausch & Lomb, Inc.), and US pachymetry (DGH Technology, Inc.). Three central corneal scans of each eye were obtained using the OCT3. First, OCT3 data were processed using the standard OCT software program (OCT3(std)). Second, OCT3 raw data were exported and measurements were repeated using Scion Image for Windows program (OCT3(sci)). The OCT3 and Orbscan results were compared with the mean of 5 US pachymetry measurements in each eye. RESULTS: The OCT3(std), OCT3(sci), and Orbscan CCT measurements showed high correlations with US pachymetry (r=0.981, r=0.984, and r=0.942, respectively; P<.0001). Bland-Altman analysis showed a high level of agreement between US pachymetry and OCT3 techniques but not Orbscan. High repeatability for OCT3(std) (r(2)=0.05) and OCT3(sci) (r(2)=0.01) was also seen. CONCLUSION: Results show the OCT3 is an accurate, noninvasive, and reproducible technique for evaluation of CCT.     

Comparison of central corneal thickness using anterior segment optical coherence tomography vs ultrasound pachymetry

PURPOSE: To determine if there is a systematic difference in central corneal thickness (CCT) measured using anterior segment optical coherence tomography (AS-OCT) as compared with ultrasound pachymetry. DESIGN: Prospective observational study. METHODS: Consecutive subjects with clinically normal corneas underwent CCT measurement by both ultrasound and AS-OCT while participating in a population-based study in Ghana, West Africa. One eye of each subject was randomly selected for analysis. Two measurements were taken and averaged. Agreement and interobserver variability were also analyzed. RESULTS: One hundred and fifty-five subjects of African ethnicity and average age 57 years (standard deviation [SD] 12; range, 40 to 98 years) were included. Measurements by AS-OCT and US were taken a mean of 15 days (maximum, six weeks) apart. The mean (SD) [range] US CCT was 525.3 microm (33.5) [422, 653] and 499.0 microm (32.0) [428, 613] with AS-OCT. Measurements by the two modalities were strongly correlated (r(2) = 0.82; P < .001), and a significant difference was observed between mean US and AS-OCT CCT (SD) [range] of 26.3 microm (14.2) [-63, 12] (P < .001). The width of the limits of agreement was 28 microm, about 6% of the average pachymetry reading. In 50 eyes randomly remeasured with OCT by a second observer, the intraclass correlation coefficient was 0.91. There was a small but significant systematic difference between observers (mean 6.9 microm, SD 10.9 microm), or 1.4% (P < .001), increasing the difference noted above. CONCLUSION: There is a reproducible systematic difference between CCT measurements taken with ultrasound and OCT. It is important to note in clinical practice, that measurements acquired by these two modalities are not directly interchangeable.     

薄角膜正常眼压性青光眼OCT检测与分析

目的 探讨薄角膜正常眼压性青光眼(NTG)患者视盘周围视网膜神经纤维层(RNFL)厚度及视盘结构的OCT特征.方法 采用OCT对21例(42只眼)中央角膜厚度(CCT)低于正常人群范围(＜500μm)的正常眼压性青光眼患者进行RNFL及视盘扫描,并根据其CCT值分为:组1(480μm≤CCT＜500μm)和组2(460μm≤CCT＜480μm),比较分析两组RNFL厚度、视盘参数及30.中心视野指数.结果 两组患者的OCT检测参数包括Avg.Thick、Savg、Iavg、Navg、Tavg差异无统计学意义(P＞0.05),Max-Min值差异有统计学意义(P＜0.05);视盘参数(垂直盘沿容积值等)、视野参数(MD、MS值)差异无统计学意义(P＞0.05).两组患者的RNFL平均厚度与视野平均缺损值MD呈强且负的直线关系(r=-0.602,P=0.000).结论 OCT能对NTG患者视盘及视网膜神经纤维层做出定量测量和分析,且与视野检测指标有良好的相关性,在NTG的早期诊断中有重要意义;薄角膜NTG患者的角膜厚度水平与视网膜神经纤维层缺损程度无明显相关.

Abstract：

Objective To investigate the thickness changes of peripapillary retinal nerve fiber layer (RNFL) in normal tension glaucoma (NTG) with thin cornea measured by optical coherence tomography (OCT).Methods Twenty-one NTG patients (42 eyes) with thin cornea were divided into two groups according to their central corneal thickness (CCT):group 1 (480μm≤CCT＜500μm) and group 2 (460μm≤CCT＜480μm),and analysis the different results of OCT scan and visual outcome in two groups.Results There were no significant differences in OCT parameters of Avg.,Thick,Savg,Iavg,Navg and Tavg among the two groups (P ＞0.05),while Max-Min was lower in group 2 (P ＜0.05);There were also no significant differences in the optic nerve head analysis results,visual field mean defect (MD) and mean sensitivity (MS) among two groups (P＞0.05).The average RNFL thickness and MD showed a strong and negative linear relationship(r =-0.602,P =0.000).Conclusions OCT can make quantitative measurement and analysis of optic disc and RNFL for NTG patients,and has a good correlation with vision field.It has important significance in the early diagnosis of NTG.For NTG patients with thin corneas,there is no significant correlation between the level of CCT and extent of retinal nerve fiber layer defect.     

FD-OCT、Visante OCT及A超角膜测厚仪测量人中央角膜厚度的比较

目的比较FD-OCT、Visante OCT及A超角膜测厚仪测量人中央角膜厚度的差异,为临床检查提供参考。方法 选取健康志愿者27人(54眼),依次用FD-OCT、VisanteOCT及A超角膜测厚仪测量双眼中央角膜厚度,三种仪器均测量3次,取其平均值,对所得数据进行统计学分析。结果 54眼志愿者中央角膜厚度测量结果:FD-OCT测量值为(530.74±31.74)μm,Visante OCT为(554.06±33.32)μm,A超为(531.61±31.76)μm。三种测量方法结果差异有统计学意义(F=9.053,P<0.01)。两两比较显示:FD-OCT测量结果与A超相比,差异无统计学意义(P>0.05);Visante OCT与A超相比,差异有统计学意义(P<0.05);Visante OCT和FD-OCT相比,差异也有统计学意义(P<0.05),但两种测量结果高度相关(r=0.949),前者所测中央角膜厚度较后者厚(23.32±10.46)μm,两者差值的95%可信区间为20.46～26.17μm。结论 A超作为目前角膜厚度测量的金标准,随着检查舒适度、检查速度等要求的提高,使用渐显局限。新的角膜测厚仪的出现,有望改善这些问题,但是诊断分析时需注意其可能带来的测量结果偏差。     

In vivo quantification of human aqueous veins by enhanced depth imaging optical coherence tomography and optical coherence tomography angiography images

AIM: To investigate the aqueous vein in vivo by using enhanced depth imaging optical coherence tomography (EDI-OCT) and optical coherence tomography angiography (OCTA). METHODS: In this cross-sectional comparative study, 30 healthy participants were enrolled. Images of the aqueous and conjunctival veins were captured by EDI-OCT and OCTA before and after water loading. The area, height, width, location depth and blood flow of the aqueous vein and conjunctival vein were measured by Image J software. RESULTS: In the static state, the area of the aqueous vein was 8166.7±3272.7 μm2, which was smaller than that of the conjunctival vein (13 690±7457 μm2, P<0.001). The mean blood flow density of the aqueous vein was 35.3%±12.6%, which was significantly less than that of the conjunctival vein (51.5%±10.6%, P<0.001). After water loading, the area of the aqueous vein decreased significantly from 8725.8±779.4 μm2 (baseline) to 7005.2±566.2 μm2 at 45min but rose to 7863.0±703.2 μm2 at 60min (P=0.032). The blood flow density of the aqueous vein decreased significantly from 41.2%±4.5% (baseline) to 35.4%±3.2% at 30min but returned to 45.6%±3.6% at 60min (P=0.021). CONCLUSION: The structure and blood flow density of the aqueous vein can be effectively evaluated by OCT and OCTA. These may become biological indicators to evaluate aqueous vein changes and aqueous outflow resistance under different interventions in glaucoma patients.     

In vivo histology of cotton-wool spots using high-resolution optical coherence tomography

PURPOSE: To provide optical characteristics of cotton-wool spots (CWS) on optical coherence tomography (OCT) and scan the retina after CWS have ophthalmoscopically disappeared. DESIGN: Observational case reports. METHODS: We studied four eyes of four patients with retinopathy due to human immunodeficiency virus (HIV) and hypertension. The StratusOCT Model 3000 in single-line mode was used for imaging of acute and resolved CWS and adjacent normal retina. The fundus photography served as a template for OCT scanning in localization of CWS. Retinal tissue reflectivity images were compared. RESULTS: There were differences in reflectivity of normal retina, the retina in the area of active CWS, and the retina in the same area after CWS has resolved. Most striking was that the OCT documented a persistent focal area of hyper-reflectivity in the area of the resolved CWS, indicative of retinal gliosis that could be imaged. CONCLUSIONS: CWS show a hyper-reflective pattern on OCT that persists even after they become ophthalmoscopically invisible.     

相干光断层扫描与荧光素眼底血管造影在中心性浆液性脉络膜视网膜病变诊断中的对比观察

目的观察对比相干光断层扫描（OCT）和荧光素眼底血管造影（FFA）在中心性浆液性脉络膜视网膜病变（CSC）诊断中的特点。设计回顾性病例系列。研究对象临床诊断为CSC的58例（62眼）患者。方法对临床诊断为CSC且均行FFA及OCT检查的58例（62眼）患者的临床资料进行对比观察,分析其影像特征。随访中每月行OCT检查,每3个月行FFA检查,对比两种影像学检查观察疾病演变过程的特点。主要指标FFA及OCT影像学表现。结果58例（62眼）患者OCT检查中,60眼（96．8％）有神经上皮脱离,其中55眼（88．7％）FFA表现为荧光渗漏,且均在OCT神经上皮脱离范围内,另5眼未见异常荧光;5眼（8．1％）伴色素上皮脱离,而FFA未见特殊表现;2眼（3．2％）OCT仅见色素上皮脱离,其中1眼FFA见黄斑鼻侧透见荧光,另1眼无异常荧光。治疗后3个月,OCT检查62眼中16眼（24．2％）见神经上皮脱离,16眼中FFA仅5眼（8．1％）有荧光渗漏;2眼伴色素上皮脱离,而FFA未有特殊表现。对FFA检查及随诊中发现渗漏点在中心凹500μm外者（57眼）行激光光凝治疗。结论OCT和FFA在对CSC的诊断上各具优势,OCT可观察到视网膜病变的形态改变,FFA可定位血管渗漏,利于激光治疗。两者结合是CSC最有效的影像诊断技术。     

Sterile structural imaging of donor cornea by optical coherence tomography

PURPOSE: The purpose of the study was to demonstrate a new noncontact method for sterile measurement of structure and thickness of donor cornea with use of optical coherence tomography (OCT). METHODS: A commercially available OCT instrument designed for retinal measurements was used for noncontact assessment of human corneas. Structural changes occurring during organ culture were evaluated in 29 corneas. Comparison with histology was performed, and the ability of OCT to detect corneal scars and corneal thickness was investigated. RESULTS: Corneal epithelium, stroma, and posterior curvature, as well as thickness, can be measured by standard OCT while the cornea remains in its storage bottle. Epithelial changes leading to a reduction of epithelial thickness, stromal structural changes, and hydration folds can be visualized. OCT scans correlate well with histology. Preexisting and developing corneal scars can be detected by OCT. CONCLUSIONS: Corneal structural imaging can be performed under sterile conditions by OCT. This provides a method for improvement of corneal storage and a screening method for signs of photorefractive surgery and scarring in donor cornea.     

Predicting retinal sensitivity using optical coherence tomography parameters in central serous chorioretinopathy

Graefe's Archive for Clinical and Experimental Ophthalmology - To predict changes in retinal sensitivity using optical coherence tomography (OCT) in eyes with central serous chorioretinopathy...     

Comparison between central corneal thickness measurements by ultrasound pachymetry and optical coherence tomography

PURPOSE: Measurement of central corneal thickness (CCT) plays an important role in both diagnostic and therapeutic assessment of ocular diseases. Although ultrasound pachymetry (U-PACH) is regarded as the golden standard for measurement of CCT, optical coherence tomography (OCT) may offer advantages as it can locate the central cornea with precision with no corneal touch. Nevertheless, the agreement of OCT with U-PACH has not yet been gauged by Bland-Altman analysis. This study compares CCT measurement by OCT with that by U-PACH. METHODS: Healthy subjects without ocular abnormality (except refractive errors less than or equal to -6.0 D), contact lens wear or ocular surgery were recruited. CCT was measured in one eye of normal subjects using OCT and U-PACH. Results were compared using correlation and Bland-Altman plots. RESULTS: Fifty subjects were recruited. Mean +/- SD CCT measured by OCT was 565 +/- 33 microm. This was highly correlated (Pearson's coefficient = 0.934) with the mean thickness measured by U-PACH (543 +/- 33 microm). The coefficients of variation were good and comparable at 7.9% for U-PACH and 3.5% for OCT. Compared with U-PACH, OCT consistently overestimated the CCT by a mean of 23 microm as shown on Bland-Altman plot. CONCLUSION: CCT measured by OCT and U-PACH is highly correlated. With appropriate adjustment factor, OCT agrees well with U-PACH and is a reliable alternative for CCT measurement.     

Comparison of epiretinal membranes of differing pathogenesis using optical coherence tomography

PURPOSE: To compare optical coherence tomography (OCT) images of idiopathic epiretinal membranes (ERMs) with those of secondary ERMs. METHODS: OCT was performed on 70 eyes of 63 consecutive patients with biomicroscopic evidence of ERMs and 23 eyes of 23 healthy volunteers without ERMs. OCT findings were correlated with the clinical pathogenesis of the ERM. RESULTS: Evaluation by OCT established that 48 of 70 ERMs were globally adherent to the retina and that 22 of 70 ERMs were focally adherent to the retina. When correlated to clinical pathogenesis, 20% of idiopathic membranes and 52% of secondary membranes were focally attached to the retina. There was a significant difference in the pattern of membrane attachment to the retina in the two pathogenic groups (P = 0.007). Eight of nine eyes with macular pseudoholes were associated with globally adherent membranes. CONCLUSION: Secondary ERMs are more likely to be characterized by focal retinal adhesion than are primary ERMs. Primary ERMs tend to be globally adherent. This finding may contribute to understanding the underlying mechanisms of ERM formation in different clinical settings.     

应用OCT观察高度近视并发白内障患者超声乳化术后黄斑中心凹厚度变化

目的:探讨超声乳化联合人工晶状体植入术的高度近视黄斑区视网膜厚度变化与术后视力的相关性.方法:随访67例67眼高度近视并发白内障超声乳化术后1wk,1、3mo的最佳矫正视力(BCVA),并行OCT检查测量黄斑中心凹视网膜厚度(CFT).于术后3mo根据患者的视力恢复情况分为A组(BCVA>0.5)和B组(BCVA≤0.5).采用重复测量数据的方差分析后两两比较、Spearman相关分析以及独立样本t检验对数据进行统计分析.结果:BCVA(LogMAR)术后各时间点较术前均好转且差异有统计学意义(F=115.04,P<0.01).CFT术前较术后1wk,1mo差异有统计学意义(P=0.04、0.02),较术后3mo差异无统计学意义(P=0.52);术后3mo较术后1wk,1mo增厚,差异均有统计意义(P<0.01).排除黄斑中心凹病变眼术后3mo的BCVA与CFT在统计学上显著相关(r=0.28,P=0.03).术后3mo A、B组间CFT差异有统计学意义(t=-2.24,P=0.03),年龄及人工晶状体度数差异均无统计学意义.结论:超声乳化联合人工晶状体植入术治疗高度近视并发白内障术后黄斑中心凹区视网膜各层结构的完整及其厚度预示可达到较好的最佳矫正视力.     

Comparison of autofluorescence and optical coherence tomography findings in acute and chronic central serous chorioretinopathy

AIM:To discuss and compare the fundus autofluorescence (FAF) and optical coherence tomography (OCT) in acute or chronic central serous chorioretinopathy (CSCR).METHODS: Medical records of 100 cases of CSCR were reviewed. Acute and chronic cases were evaluated according to the duration of decreased visual acuity, serous retinal detachment (RD) and focal leakage on fluorescein angiography (FA). Chi-square test was used for statistical analysis.RESULTS:Forty cases had acute and 60 cases had chronic CSCR. FAF showed focal hypo-autofluorescence in 34 (85%) and iso-autofluorescence in 6 (15%) of acute cases and hypo-autofluorescence in 51 (85%), hyper-autofluorescence in 6 (10%) and iso-autofluorescence in 3 (5%) of chronic cases. OCT showed serous RD with distinct borders correlated with FAF findings (hypo-autofluorescence) in all acute CSCR cases. In chronic CSCR group, OCT showed serous RD with indistinct borders correlated with FAF findings. The differences between the OCT and FAF findings of the two groups were significant (P=0.000).CONCLUSION: OCT and FAF findings can support the clinical observations in differential diagnosis of acute and chronic CSCR and help clinicians to evaluate retinal pigment epithelium, outer segments of photoreceptors and the components of serous RD.     

Histologic correlation of in vivo optical coherence tomography images of the human retina

PURPOSE: To correlate in vivo human retina optical coherence tomography (OCT)3 images with histology. DESIGN: Case series. METHODS: Linear OCT3 scans through the macula and optic nerve were obtained in three eyes of three patients who then underwent exenteration surgery for orbital cancers. OCT3 images were then correlated with histology. RESULTS: On histology, two eyes were normal, and one eye had dry macular degeneration. The plexiform layers on histology correlated with the green/yellow areas on the OCT3 scans, and the nuclear layers correlated with the black areas on the OCT3 scans. CONCLUSIONS: The authors are unaware of previous reports correlating histology to in vivo human retina OCT3 images. Our findings using human eyes are not different from previous animal studies, in that the plexiform layers are optically highly backscattering and the nuclear layers are not.