Thickness In Normal Eyes Research Articles

Direct comparison of spectral-domain and swept-source OCT in the measurement of choroidal thickness in normal eyes

ObjectiveTo compare spectral-domain optic coherence tomography (SD-OCT) and swept-source OCT (SS-OCT) in the study of choroidal thickness (CT) in healthy eyes.MethodsProspective, cross-sectional, single-centre study. 82 healthy eyes of 46 patients...

Evaluation of central retinal thickness and subfoveal choroidal thickness in normal eyes

AbstractPurpose To determine central retinal thickness and subfoveal choroidal thickness using optical coherence tomography (OCT) and to evaluate association between both thickness and age, gender and axial length.Methods Spectral domain OCT images (Bioptigen, Bioptigen, inc., Durham, NC) were obtained in 151 eyes of 151 healthy volunteers without retinal diseases. The IOL master (Carl Zeiss Meditech) was used to measure the eye length to compensate axial scale factor of the SD‐OCT images. The choroidal thickness at the fovea and central retinal thickness was measured. Statistical analysis using paired t‐test and Pearson correlation were performed to evaluate the correlation between both thickness and age, axial length, and gender.Results The mean and median age of the 151 subjects were 33.3 and 29 years old, respectively (range, 7 to 80 years). There were 57 males and 94 females. The mean and median axial lengths of the eye were 24.54±0.98 mm and 24.37 mm respectively. The mean central retinal thickness were 213.89±14.64μm. Increasing age and axial length were not correlated with central retinal thickness. The mean choroidal thickness in these normal eyes was 214.43±13.63μm. Increasing age (Pearsun correlation ‐ 0.193, R2=‐0.0372, p=0.018) and increasing axial length (Pearsun correlation ‐ 0.189, R2=‐0.0359, p=0.020) were correlated with decreasing choroidal thickness. Central retinal thickness and subfoveal choroidal thickness have no relationship between them in our study (Pearsun correlation ‐ 0.139, R2=0.0192, p=0.090 ).Conclusion Only the choroidal thickness at the fovea in normal eyes showed an inverse correlation with age and axial length. And there is no significant relationship between central retinal thickness and subfoveal choroidal thickness.

Effect of Age on Individual Retinal Layer Thickness in Normal Eyes as Measured With Spectral-Domain Optical Coherence Tomography

To determine the effect of age on the thickness of individual retinal layers, measured with spectral-domain optical coherence tomography (SD-OCT), in a population of healthy Caucasians. One hundred and twenty subjects with an age ranging between 18 and 81 years were examined with SD-OCT. Mean layer thickness was calculated for seven retinal layers, in the fovea (region 1 of the 9 Early Treatment Diabetic Retinopathy Study [ETDRS] regions); in the pericentral ring (ETDRS regions 2 to 5); and the peripheral ring (ETDRS regions 6 to 9) following automated segmentation using the Iowa Reference Algorithm. In addition, mean peripapillary retinal nerve fiber layer (RNFL) thickness was measured. The partial correlation test was performed on each layer to determine the effect of age on layer thickness, while correcting for spherical equivalent, sex, and Topcon image quality factor as confounders, followed by Bonferroni corrections to adjust for multiple testing. The thickness of the peripapillary RNFL (R = -0.332; P < 0.001); pericentral ganglion cell layer (R = -0.354, P < 0.001); peripheral inner plexiform layer (R = -0.328, P < 0.001); and foveal outer segment layer (R = -0.381, P < 0.001) decreased significantly with increasing age. Foveal RPE thickness (R = 0.467, P < 0.001) increased significantly with increasing age; other layers showed no significant differences with age. Several macular layers and the peripapillary RNFL thickness showed significant changes correlated with age. This should be taken into consideration when analyzing macular layers and the peripapillary RNFL in SD-OCT studies of retinal diseases and glaucoma.

Outer photoreceptor layer thickness mapping in normal eyes and eyes with various macular diseases using spectral domain optical coherence tomography: A pilot study

To obtain a de novo map of outer photoreceptor layer (OPRL) thickness using a semiautomatic segmentation method for commercial spectral-domain optical coherence tomography (SD-OCT) and analyze the features of the resulting OPRL map in normal eyes and eyes with various inactive macular diseases. Forty normal eyes and 50 eyes with various inactive macular diseases such as resolved central serous chorioretinopathy (20 eyes), surgically-repaired macular hole (10 eyes), epiretinal membrane (10 eyes), and reattached rhegmatogenous retinal detachment (10 eyes) were screened. All subjects underwent a 12 radial scan protocol in SD-OCT. The segmentation lines defining the OPRL were modified using built-in software. The diseased eyes were subdivided into two groups (good vision, or intermediate to poor vision) based on a visual acuity better or worse than 20/40. The map of the OPRL thickness was obtained automatically by the embedded software and was presented as the Early Treatment Diabetic Retinopathy Study (ETDRS) style. The mean OPRL thickness in normal eyes in all subfields was 40.37 ± 4.35 μm. The central subfield area showed the greatest mean OPRL thickness in normal eyes. The mean OPRL thickness of diseased eyes with good vision in the central subfield was greater than that of eyes with intermediate to poor vision. The OPRL thickness map showed various patterns according to the type of macular diseases. We suggest that our semiautomated segmentation method using a 12 radial scan protocol is simple, fast, and suitable for producing a reliable OPRL map with ETDRS. This quantitative data could be useful in clinical practice or research of various macular diseases.

Relationship between progression of visual field damage and choroidal thickness in eyes with normal‐tension glaucoma

To measure choroidal thickness in normal eyes and in patients with normal-tension glaucoma using enhanced depth imaging optical coherence tomography and evaluate the association between choroidal thickness and progression of visual field damage. Cross-sectional comparative study. A total of 62 eyes of 62 normal subjects and 45 eyes of 45 normal-tension glaucoma patients were examined. The choroid was measured at the fovea and 3 mm nasal and temporal from the fovea. In the separate study, both eyes of the patients with normal-tension glaucoma were included in the analyses. Visual fields were measured with automated perimetry. Changes in mean deviation per year (dB/year), that is, mean deviation slope, were calculated. Difference in the choroidal thickness between the normal subjects and the patients with normal-tension glaucoma. The relationship between mean deviation slope and the choroidal thickness in eyes with normal-tension glaucoma was analysed. Compared with normal subjects, the choroidal thickness was significantly thinner in eyes with normal-tension glaucoma at 3 mm nasal from the fovea (P = 0.02). There was a significant correlation between the choroidal thickness at 3 mm nasal from the fovea and the mean deviation slope (Pearson's r = 0.413; P < 0.001). The decrease in the thickness of the choroid at 3 mm nasal from the fovea in eyes with normal-tension glaucoma may be associated with progressive visual field loss. Thus, choroidal abnormalities may play a role in the pathogenesis of normal-tension glaucoma.

Repeatability and Reproducibility of Subfoveal Choroidal Thickness in Normal Eyes of Japanese Using Different SD-OCT Devices

To compare subfoveal choroidal thickness (SCT) measurements of three different commercially available spectral-domain optical coherence tomography instruments with healthy eyes of Japanese. A prospective, cross-sectional study was performed at a single institution. SCT of the right eye of 43 normal subjects was measured using three different SD-OCTs: Heidelberg Spectralis-OCT (Spectralis), Cirrus HD-OCT (Cirrus), and Topcon 3D OCT-1000 Mark II (Topcon). Two separate measurements were performed for the same eye with a maximum by a single examiner. SCT was defined as the distance from the posterior edge of the retinal pigment epithelium to the choroid/sclera junction. After manual segmentation, measurements were made using calipers equipped on each machine by masked raters. Intraclass, interrater, and intermachine agreements were assessed. Forty-three subjects (mean age, 30.5 years) were enrolled. Of 43 eyes, the SCT of 39 eyes (90.7%) could be measured using each machine. Intraclass correlation coefficients (95% confidence intervals) were 0.976 (0.954-9.987), 0.958 (0.919-0.978), and 0.939 (0.895-0.971) with Spectralis, Cirrus, and Topcon, respectively. Interrater correlation coefficients (95% confident interval) were 0.944 (0.893 to 0.971), 0.956 (0.831 to 0.983), and 0.924 (0.825 to 0.964) with Spectralis, Cirrus, and Topcon, respectively. The average SCT was 272.6, 272.8, and 269.2 μm with Spectralis, Cirrus, and Topcon, respectively. The intermachine correlation coefficient was significantly high among the machines (P<0.001, Spearman), 0.97 (Spectralis-Cirrus), 0.96 (Cirrus-Topcon), and 0.98 (Topcon-Cirrus). Bland-Altman plot analysis showed no typical trend among the machines. SCT measurements obtained with three different SD-OCTs were highly correlated and could be used interchangeably. (http://upload.umin.ac.jp number, UMIN000005287.).

Spectral- and time-domain optical coherence tomography measurements of macular thickness in normal eyes and in eyes with diabetic macular edema

To report macular thickness values in normal eyes and eyes with diabetic macular edema (DME) using time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT), and to derive a conversion equation. The index study was a prospective investigation conducted on 80 eyes from 40 normal subjects and 130 eyes from 118 patients with DME seen in our clinic. Retinal thickness values from the central 1 mm of the macula and surrounding four ETDRS subfields were acquired using TD-OCT (Stratus OCT) and SD-OCT (SPECTRALIS HRA+OCT). Measurements of the central (C) subfield from both devices were used to derive a conversion equation. The equation was used to predict SD-OCT values using measurements from TD-OCT. Agreement between predicted and actual SD-OCT measurements was assessed. In normal eyes, the mean difference between TD-OCT and SD-OCT measurements of the C subfield was 76 μm (CI(95)=74 and 77, respectively). The conversion equation, y=1.029x+72.49, was derived. In eyes with DME, using the equation, SPECTRALIS-predicted values were 5% higher than actual measurements, with 95% of predicted values falling within 9% of the actual measurements. Relocating SD-OCT grids to match the location on TD-OCT resulted in predicted values falling within 7% of actual measurements. The percent difference between actual thickness measurements from SPECTRALIS and predicted thickness measurements, using the conversion equation, was within reported limits of repeatability of Stratus in eyes with DME. Our equation may help correlate OCT values from both devices in standard care and clinical trials for DME.

Macular Ganglion Cell Layer Imaging in Preperimetric Glaucoma with Speckle Noise–Reduced Spectral Domain Optical Coherence Tomography

To visualize the macular ganglion cell layer (GCL) and measure its thickness in normal eyes and eyes with preperimetric glaucoma, using speckle noise-reduced spectral domain optical coherence tomography (SD-OCT). Retrospective consecutive case series. Thirty-seven eyes of 37 patients with preperimetric glaucoma and 39 normal eyes of 39 volunteers. Vertical and horizontal SD-OCT B-scan images were acquired with minimal speckle noise by using eye-tracking to obtain and average 50 B-scans at each identical location of interest. B-scan images were manually analyzed for GCL, retinal nerve fiber layer (RNFL), and inner plexiform layer shapes and thicknesses in the macula. Macular GCL images and thickness in normal eyes and in eyes with preperimetric glaucoma. The macular GCL was clearly seen on speckle noise-reduced SD-OCT images in normal eyes and eyes with preperimetric glaucoma. In each eye with preperimetric glaucoma, thinning of the macular GCL was visually apparent, particularly on vertical scans. The mean regional macular GCL was most severely thinned in the inferior perifoveal region, where its thickness was <70% of its normal thickness in 30 (81.1%) of the 37 eyes and <50% of its normal thickness in 13 (35.1%) of the 37 eyes. When the sensitivity and specificity for detecting abnormal thinning (outside the lower limit of 99% confidence interval [CI] for the means in the 39 normal eyes) in at least one 0.5-mm segment or sector were compared, the macular GCL on vertical B-scans exhibited higher sensitivity (81.1%) than the other layers on vertical B-scans (99% CI, 5.4%-59.5%; P = 0.00075-0.02100), the macular GCL (99% CI, 40.5%; P = 0.00027) on horizontal B-scans, the other layers (99% CI, 5.4%-48.6%; P<0.00048-0.00400) on horizontal B-scans, and circumpapillary RNFL automatically measured on SD-OCT (54.1%; P = 0.021), and scanning laser polarimetry with variable corneal compensation (24.3%; P = 0.00095). All the macular layers on both the vertical and horizontal B-scans and circumpapillary RNFL thickness exhibited comparable specificity (91.4-100.0%, statistically not different). Speckle noise-reduced SD-OCT imaging allowed clear visualization and measurement of the macular GCL, which was severely thinned in eyes with preperimetric glaucoma. Proprietary or commercial disclosure may be found after the references.

Therapeutic efficiency of tissue-engineered human corneal endothelium transplants on rabbit primary corneal endotheliopathy.

To evaluate the therapeutic efficiency of tissue-engineered human corneal endothelia (TE-HCEs) on rabbit primary corneal endotheliopathy (PCEP), TE-HCEs reconstructed with monoclonal human corneal endothelial cells (mcHCECs) and modified denuded amniotic membranes (mdAMs) were transplanted into PCEP models of New Zealand white rabbits using penetrating keratoplasty. The TE-HCEs were examined using diverse techniques including slit-lamp biomicroscopy observation and pachymeter and tonometer measurements in vivo, and fluorescent microscopy, alizarin red staining, paraffin sectioning, scanning and transmission electron microscopy observations in vitro. The corneas of transplanted eyes maintained transparency for as long as 200 d without obvious edema or immune rejection. The corneal thickness of transplanted eyes decreased gradually after transplanting, reaching almost the thickness of normal eyes after 156 d, while the TE-HCE non-transplanted eyes were turbid and showed obvious corneal edema. The polygonal corneal endothelial cells in the transplanted area originated from the TE-HCE transplant. An intact monolayer corneal endothelium had been reconstructed with the morphology, cell density and structure similar to those of normal rabbit corneal endothelium. In conclusion, the transplanted TE-HCE can reconstruct the integrality of corneal endothelium and restore corneal transparency and thickness in PCEP rabbits. The TE-HCE functions normally as an endothelial barrier and pump and promises to be an equivalent of HCE for clinical therapy of human PCEP.

Determinants of Perimacular Inner Retinal Layer Thickness in Normal Eyes Measured by Fourier-Domain Optical Coherence Tomography

To determine the effects of age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness on perimacular inner retinal layer thickness in the normal human eye as measured by Fourier-domain optical coherence tomography (FD-OCT). In this cross-sectional observational study, 182 Korean healthy subjects aged from 22 to 84 years were included. To obtain the inner retinal layer thickness, perimacular ganglion cell complex thickness, which extends from the internal limiting membrane to the inner nuclear layer, was measured by FD-OCT on one randomly selected eye of each subject. Linear regression analyses of the effects of demographic and clinical variables, including age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness, on perimacular inner retinal layer thickness were performed. The mean inner retinal layer thickness for the entire population was 93.87 μm. Thinner inner retinal layer measurements were associated with older age (P = 0.010) and greater axial length (P = 0.021). Mean inner retinal layer thickness decreased by approximately 1.59 μm for every decade of age and by approximately 1.56 μm for every 1-mm greater axial length. There was no relationship between inner retinal layer thickness and sex, anterior chamber depth, optic disc area, or central corneal thickness. Inner retinal layer thickness, as measured by FD-OCT, varies significantly with age and axial length. The effect is small but clinically relevant in the interpretation of inner retinal layer thickness measurements.

Quantification of Retinal Nerve Fiber Layer Thickness in Normal Eyes, Eyes with Ocular Hypertension, and Glaucomatous Eyes with SD-OCT

To quantitatively evaluate and compare retinal nerve fiber layer (RNFL) thickness between normal eyes, eyes with ocular hypertension (OHT), and glaucomatous eyes in an Indian population using spectral domain optical coherence tomography (SD-OCT). Average and quadrant RNFL values were compared among three groups (66 normal eyes, 55 OHT eyes, and 51 glaucomatous eyes) and the discriminating power of each parameter was evaluated by calculating areas under receiver operator curves (AROCs). The mean RNFL thickness was 93.45 ± 16.9 μm in glaucomatous eyes, significantly less than in normal (112.48 ± 6.8 μm) and OHT (110.09 ± 10.9 μm) eyes. OHT eyes had significantly thinner RNFL thickness in the temporal quadrant (P = .006) than normal eyes. RNFL thickness in glaucomatous eyes differed significantly from normal eyes in most parameters except nasal quadrant (P = .1) and from OHT eyes in most parameters except temporal (P = .4) and nasal quadrants (P = .3). The parameter with the largest AROC to discriminate between OHT and normal eyes was temporal quadrant (0.65). Inferior quadrant RNFL thickness had the largest AROC (0.93) to distinguish between OHT and glaucomatous eyes and normal and glaucomatous eyes. SD-OCT identified differences in most parameters between eyes with glaucoma and normal eyes and also between eyes with glaucoma and OHT. Overlap of RNFL thickness between normal and OHT eyes limits the ability of this instrument to differentiate between normal and OHT subjects.

Comparison of Retinal Nerve Fiber Layer Thickness in Normal Eyes Using Time-Domain and Spectral-Domain Optical Coherence Tomography

To compare retinal nerve fiber layer (RNFL) thickness measurements between 3 different spectral-domain optical coherence tomography (SD-OCT) instruments (Spectralis; Heidelberg Engineering; Cirrus; Carl Zeiss Meditec; RTVue; Optovue, Inc) and one time-domain OCT (Stratus; Carl Zeiss Meditec). Prospective, cross-sectional study. RNFL thickness was measured on both eyes of 40 normal subjects using Stratus, Spectralis, RTVue, and Cirrus OCT on the same day. Scans were repeated 2 to 8 weeks later in the same fashion. Agreement with Stratus was evaluated for each SD-OCT and intervisit reproducibility was assessed for all machines. Mean RNFL thickness determined by each of the 3 SD-OCT instruments was highly correlated with Stratus (r = 0.87-0.91). The mean RNFL thickness (mean ± standard deviation) was 110.1 ± 12.8 μm for Stratus, 106.6 ± 12.8 μm for Spectralis, 98.7 ± 10.9 μm for Cirrus, and 112.8 ± 13.2 μm for RTVue. The average differences between each SD-OCT and Stratus for mean RNFL thickness were all statistically significant (P ≤ .001), as were most quadrant measurements. All 4 instruments demonstrated excellent intraclass correlation coefficient values for mean RNFL thickness (0.90-0.97). However, intervisit variability was lowest for RTVue as evidenced by reproducibility values, followed by Stratus, Cirrus, and Spectralis (6.59, 8.83, 8.89, and 11.72 μm, respectively). RNFL measurements taken with Spectralis, RTVue, and Cirrus all have excellent correlation to Stratus, with good reproducibility in normal eyes. Despite high correlations, RNFL values are significantly different between instruments and should not be used interchangeably.

Comparison of Corneal Thickness Measurements Using Galilei, HR Pentacam, and Ultrasound

To assess the degrees of agreement in measuring corneal thickness in normal eyes between 2 noncontact systems based on the dual Scheimpflug system (Galilei; Ziemer) and rotating Scheimpflug imaging (HR Pentacam; Oculus) and also between each of these methods and the gold-standard method of ultrasound pachymetry. In a prospective study, measurement agreement was assessed in 47 eyes of 47 healthy subjects. All eyes were examined with each of the 3 devices. Measurements made with the Galilei and HR Pentacam were compared with those made with ultrasound. The central corneal thickness (CCT) and thinnest pachymetry of the Galilei and HR Pentacam were also compared. The mean values of CCT obtained from Galilei, HR Pentacam, and ultrasound were 560.57 ± 29.10, 542.31 ± 30.50, and 548.61 ± 29.92 μm, respectively. The 95% limits of agreement of each of these devices with ultrasound were -11.03 and +34.94 μm for the Galilei and -33.67 and +20.74 μm for the Pentacam. The 95% limits of agreement of Galilei with Pentacam in measurement of central and thinnest corneal thickness were -3.39 and +33.11 and -10.40 and +27.29 μm, respectively. Although CCT measurements made with the HR Pentacam were thinner (P < 0.001), and those obtained with Galilei were thicker (P < 0.001) than those made with ultrasound, there were significant correlation between Galilei and ultrasound (r = 0.92; P < 0.0001) and between HR Pentacam and ultrasound (r = 0.89; P < 0.0001). The central and thinnest corneal thickness measurements made with the HR Pentacam were thinner (P < 0.0001) than those made with Galilei, but there was a significant correlation between Galilei and HR Pentacam in measuring CCT (r = 0.96; P < 0.0001) and thinnest corneal thickness (r = 0.95; P < 0.0001). Bland-Altman plots showed good agreement between these methods. Although differences between the devices were statistically significant, there was good correlation and agreement between Galilei and Pentacam in measuring central and thinnest corneal thickness. The corneal thickness measurements made with the HR Pentacam and Galilei also showed good correlation and agreement with those made with ultrasound.

Pachymetric mapping with Fourier-domain optical coherence tomography

To evaluate the repeatability of Fourier-domain optical coherence tomography (OCT) pachymetric mapping and compare central corneal thickness (CCT) measurements by OCT, ultrasound pachymetry, and scanning-slit tomography. Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. A Fourier-domain OCT system was used to map the corneal thickness in normal eyes with scans centered on the corneal vertex or the pupil. Repeatability of central and pericentral map sectors was assessed by pooled standard deviation. The CCT measurements were compared between the OCT, ultrasound, and scanning-slit devices. Pupil centration (SD: 1.3 microm central, 1.8 to 3.8 microm pericentral) provided better repeatability than vertex centration (SD: 1.7 microm central, 2.4 to 5.7 microm pericentral) in all sectors (P<.035). The mean CCT was 536.9 microm +/- 27.0 (SD) by OCT, 556.6 +/- 30.5 microm by ultrasound, and 537.2 +/- 32.6 microm by scanning-slit tomography (acoustic factor 0.92). The CCT measured by OCT was significantly thinner than by ultrasound pachymetry (P = .007; mean difference -19.7 microm; 95% limits of agreement [LoA], -40.4 to 0.9 microm) but not than by scanning-slit tomography (P = .2637; mean difference -0.3 microm; 95% LoA, -24.0 to 23.5 microm). The CCT by OCT correlated well with ultrasound and scanning-slit CCTs (r = 0.940 and r = 0.934, respectively). Pachymetric mapping with Fourier-domain OCT was highly repeatable. Repeatability was better with pupil-centered scans than with corneal vertex-centered scans. Ultrasound pachymetry, Fourier-domain OCT, and scanning-slit tomography should not be used interchangeably for CCT assessment.

Comparison of Retinal Thickness in Normal Eyes Using Stratus and Spectralis Optical Coherence Tomography

Spectral-domain optical coherence tomography (SD-OCT) is an advancement over time-domain OCT (TD-OCT) in the imaging of retinal disorders. Retinal thickness measured by SD-OCT differs from that measured by TD-OCT because the delineation of the outer boundary of the retina differs in the two instruments. The present study aims to evaluate this difference by comparing macular thickness, as obtained by Stratus and Spectralis OCT, in subjects without any known retinal disease. Thirty-six subjects with no history of retinal disease and with normal vision and normal intraocular pressure were enrolled in the study. Both Stratus and Spectralis OCT scanning were performed by the same operator on all subjects in one eye. Central point thickness (CPT) and retinal thickness in nine ETDRS subfields, including central subfield (CSF), were measured. Student's t-test was used to determine statistical significance. Mean CPT, as measured by the Stratus and Spectralis OCT, was 166.9 +/- 20.9 microm and 225.1 +/- 17.1 microm (P < 0.0001), and mean CSF was 202.3 +/- 19.6 microm and 271.4 +/- 19.6 microm (P < 0.0001), respectively. Although the mean difference in CSF thickness was 69.1 microm, it ranged from 61.9 to 74 microm in the other eight ETDRS subfields. An increased measurement in retinal thickness of approximately 65 to 70 microm, as measured by Spectralis OCT compared with Stratus OCT, is consistent with the extent of axial retinal thickness measured by the two instruments. This increased measurement corresponds to the inclusion of the outer segment-RPE-Bruch's membrane complex by Spectralis OCT, which is relevant to studies using the newer SD-OCT for assessment of retinal thickness.

ENHANCED DEPTH IMAGING OPTICAL COHERENCE TOMOGRAPHY OF THE CHOROID IN CENTRAL SEROUS CHORIORETINOPATHY

The purpose of the study was to evaluate the choroidal thickness in patients with central serous chorioretinopathy, a disease attributed to increased choroidal vascular hyperpermeability. Patients with central serous chorioretinopathy underwent enhanced depth imaging spectral-domain optical coherence tomography, which was obtained by positioning a spectral-domain optical coherence tomography device close enough to the eye to acquire an inverted image. Seven sections, each comprising 100 averaged scans, were obtained within a 5 degrees x 30 degrees rectangle to encompass the macula. The subfoveal choroidal thickness was measured from the outer border of the retinal pigment epithelium to the inner scleral border. The mean age of subjects undergoing enhanced depth imaging spectral-domain optical coherence tomography was 59.3 years (standard deviation, 15.8 years). Seventeen of 19 patients (89.5%) were men, and 12 (63.2%) patients had bilateral clinical disease. The choroidal thickness measured in 28 eligible eyes of the 19 patients was 505 microm (standard deviation, 124 microm), which was significantly greater than the choroidal thickness in normal eyes (P < or = 0.001). Enhanced depth imaging spectral-domain optical coherence tomography demonstrated a very thick choroid in patients with central serous chorioretinopathy. This finding provides additional evidence that central serous chorioretinopathy may be caused by increased hydrostatic pressure in the choroid.

A Pilot Study of Enhanced Depth Imaging Optical Coherence Tomography of the Choroid in Normal Eyes

To measure macular choroidal thickness in normal eyes at different points using enhanced depth imaging (EDI) optical coherence tomography (OCT) and to evaluate the association of choroidal thickness and age. Retrospective, observational case series. EDI OCT images were obtained in patients without significant retinal or choroidal pathologic features. The images were obtained by positioning a spectral-domain OCT device close enough to the eye to acquire an inverted image. Seven sections were obtained within a 5 x 30-degree area centered at the fovea, with 100 scans averaged for each section. The choroid was measured from the outer border of the retinal pigment epithelium to the inner scleral border at 500-microm intervals of a horizontal section from 3 mm temporal to the fovea to 3 mm nasal to the fovea. Statistical analysis was performed to evaluate variations of choroidal thickness at each location and to correlate choroidal thickness and patient age. The mean age of the 30 patients (54 eyes) was 50.4 years (range, 19 to 85 years), and 14 patients (46.7%) were female. The choroid was thickest underneath the fovea (mean, 287 microm; standard deviation, +/- 76 microm). Choroidal thickness decreased rapidly in the nasal direction and averaged 145 microm (+/- 57 microm) at 3 mm nasal to the fovea. Increasing age was correlated significantly with decreasing choroidal thickness at all points measured. Regression analysis suggested that the subfoveal choroidal thickness decreased by 15.6 microm for each decade of life. Choroidal thickness seems to vary topographically within the posterior pole. The thickness of the choroid showed a negative correlation with age. The decrease in the thickness of the choroid may play a role in the pathophysiologic features of various age-related ocular conditions.

Morphometric Analysis of Human Peripapillary Retinal Nerve Fiber Layer Thickness

The peripapillary retinal nerve fiber layer (RNFL) thickness pattern in the normal human eye has been well characterized using data obtained with scanning laser polarimetry and optical coherence tomography. The authors sought to characterize the normative peripapillary RNFL thickness and pattern using histologic sections obtained from healthy postmortem human eyes. Seventeen unpaired normal postmortem eyes were recruited into this study. Each eye was sectioned using the "umbrella technique" to obtain four concentric peripapillary rings, each centered on the optic disc, with diameters of 3.0, 3.5, 4.0, and 4.5 mm. RNFL thickness data along each ring section was measured at 100 equidistant locations. Thickness data, for each ring diameter, across all eyes were averaged to arrive at normative thickness values for the peripapillary RNFL thickness in eyes processed using this technique. Average RNFL thicknesses (+/-SD) for the 3.5-mm diameter ring were as follows: overall, 60.3 +/- 19.5 microm; superior, 75.3 +/- 26.5 mum; inferior, 69.4 +/- 22.4 microm; nasal, 48.1 +/- 15 microm; temporal, 49.2 +/- 26.4 microm. Qualitatively, the RNFL thickness showed a double-hump pattern with relatively similar superior and inferior peaks and with temporal and nasal troughs. Progressively larger peripapillary rings showed progressively thinner RNFL thickness at all quadrants. In contrast, the relative thickness percentage for each quadrant remained unchanged among the four different diameter rings. Histologic data from a group of healthy postmortem eyes demonstrate the pattern of RNFL thickness in normal eyes. These data corroborate imaging findings of peripapillary RNFL thickness patterns obtained using commercially available RNFL imaging devices.

Macular Thickness Measurements in Normal Eyes Using Spectral Domain Optical Coherence Tomography

Knowledge of the macular thickness in a normal population is important for the evaluation of pathological macular change. The purpose of this study was to define and measure macular thickness in normal eyes using spectral domain optical coherence tomography (OCT). Fifty eyes from 50 normal subjects (29 men and 21 women, aged 22 to 68 years) were scanned with a prototype Cirrus HD-OCT system (5 microm axial resolution) (Carl Zeiss Meditec, Inc.). The proprietary Cirrus segmentation algorithm was used to produce retinal thickness maps, which were then averaged over 9 regions defined by a circular target centered at the true fovea location. The macular thickness of 13 subjects scanned with both HD-OCT and StratusOCT were compared. After centering the fovea, the mean and standard deviation values for retinal thickness measurements were calculated point wise and averaged on standard regions. For patients scanned with both systems, the thickness measurements from HD-OCT were approximately 50 microm larger than those from StratusOCT. The difference between the two measurements decreased somewhat with eccentricity. Using HD-OCT, it is possible to acquire retinal data sets containing an unprecedented number of data points. Furthermore, it is possible to use OCT fundus images to evaluate the scan quality and to center the measurement at the fovea. These advantages, together with good automated segmentation, can produce more accurate retinal thickness measurements. Incorporation of the photoreceptor layer in the measurements is anatomically meaningful and may be significant in evaluating various retinal pathologies and visual acuity outcomes.

The use of the Reichert ocular response analyser to establish the relationship between ocular hysteresis, corneal resistance factor and central corneal thickness in normal eyes

Purpose The aim of this study was to measure ocular hysteresis and corneal resistance factor (CRF), novel methods of analysing ocular rigidity/elasticity and to determine the relationship between central corneal thickness (CCT), hysteresis and CRF in normal subjects. Design Prospective, cross-sectional, clinical trial. Participants The study included 207 normal eyes. Methods Hysteresis and CRF were measured by the ocular response analyser. The CCT was measured using a hand held ultrasonic pachymeter. Main outcome measures Ocular hysteresis and CRF in normal patients and their relationship with CCT. Results The mean hysteresis was 10.7 ± 2.0 mmHg standard deviation (S.D.) (range 6.1–17.6 mmHg); the mean CRF was 10.3 ± 2.0 (range 5.7–17.1 mmHg). The mean CCT was 545.0 ± 36.4 μm (471–650 μm). The relationship between hysteresis and CCT; CRF and CCT; CRF and hysteresis were significant ( p < 0.0001). Conclusion This study demonstrated that corneal hysteresis increased with increasing CCT, however, the correlation was moderate. It would appear that CCT, hysteresis and CRF may measure different biomechanical aspects of ocular rigidity and are likely to be useful additional measurement to CCT in the assessment of ocular rigidity when measuring intraocular pressure (IOP). This may be of particular importance when trying to correct IOP measurements for increased or decreased ocular rigidity.