Comparison of multicolor scanning laser ophthalmoscopy and optical coherence tomography angiography for detection of microaneurysms in diabetic retinopathy.

This study aimed to evaluate the usefulness of multicolor (MC) scanning laser ophthalmoscopy (MC-SLO) in detecting microaneurysm (MA) in eyes with diabetic retinopathy (DR). This was a retrospective cross-sectional study. Eyes with DR underwent fluorescein angiography (FA), MC-SLO, optical coherence tomography angiography (OCTA), and color fundus photography (CFP) were analyzed. The foveal region was cut in an 6 × 6 mm image and the number of MA in each image was counted by retina specialists to determine the sensitivity and positive predictive value. FA results were used as the ground standard. MAs were classified as those with early, late, or no dye leakage based on FA images. Fifty-four eyes of 35 patients with an average age of 64.5 ± 1.24 years were included. The sensitivity of MA detection was 37.3%, 15.3%, and 4.12% in MC-SLO, OCTA, and CFP, respectively (P < 0.01 in each pair).The positive predictive value was 66.4%, 46.4%, and 27.6% in MC, OCTA, and CFP, respectively (P < 0.01 in each pair). Sensitivity for MAs with early leakage was 36.4% in MC-SLO, which was significantly higher than 4.02% in OCTA. MC-SLO was more useful in detecting MA in eyes with DR than OCTA.

Artificial intelligence for classifying uncertain images by humans in determining choroidal vascular running pattern and comparisons with automated classification between artificial intelligence.

PURPOSE: Abnormalities of the running pattern of choroidal vessel have been reported in eyes with pachychoroid diseases. However, it is difficult for clinicians to judge the running pattern with high reproducibility. Thus, the purpose of this study was to compare the degree of concordance of the running pattern of the choroidal vessels between that determined by artificial intelligence (AI) to that determined by experienced clinicians. METHODS: The running pattern of the choroidal vessels in en face images of Haller's layer of 413 normal and pachychoroid diseased eyes was classified as symmetrical or asymmetrical by human raters and by three supervised machine learning models; the support vector machine (SVM), Xception, and random forest models. The data from the human raters were used as the supervised data. The accuracy rates of the human raters and the certainty of AI's answers were compared using confidence scores (CSs). RESULTS: The choroidal vascular running pattern could be determined by each AI model with an area under the curve better than 0.94. The random forest method was able to discriminate with the highest accuracy among the three AIs. In the CS analyses, the percentage of certainty was highest (66.4%) and that of uncertainty was lowest (6.1%) in the agreement group. On the other hand, the rate of uncertainty was highest (27.3%) in the disagreement group. CONCLUSION: AI algorithm can automatically classify with ambiguous criteria the presence or absence of a symmetrical blood vessel running pattern of the choroid. The classification was as good as that of supervised humans in accuracy and reproducibility.

Quantitative analyses of diameter and running pattern of choroidal vessels in central serous chorioretinopathy by en face images.

This study was to investigate the choroidal vessels in eyes with central serous chorioretinopathy (CSC) quantitatively. We studied 41 CSC eyes and their fellow eyes, and 41 normal eyes of 41 age-adjusted individuals. En-face optical coherence tomography image of the top 25% slab of Haller's layer was analyze. The mean vessel area, vessel length, and vessel diameter were calculated. The running pattern of the vessels was quantified and used to determine the degree of symmetry, the "symmetry index". The vessel area of CSC eyes was not significantly different from that of fellow eyes but significantly larger than that of normal eyes. The vessel length of CSC eyes was not significantly different from fellow eyes but significantly shorter than that of normal eyes. The mean vessel diameter was larger in CSC eyes than in the fellow eyes and the normal eye. The symmetry index was not significantly different in CSC eyes from that of their fellow eyes but was smaller than that of normal eyes. The quantitative analysis showed that eyes with CSC had larger choroidal vessels and asymmetrical vessels running in Haller's layer.

Effect of optical correction on choroidal structure in children with anisohypermetropic amblyopia.

The aim of this study was to assess the effect of wearing optical correction on the choroidal structure in eyes of children with anisohypermetropic amblyopia. This study was conducted at the Nara Medical University Hospital and at the Tokushima University Hospital. Twenty-nine anisohypermetropic amblyopic eyes and their fellow eyes of 29 amblyopic patients (mean age, 5.7 ± 1.7 years, range 3- to 8-years) and twenty eyes of 20 age-similar control children (4.9 ± 0.8 years, range 4- to 6-years) were studied. All patients wore optical correction and 15 patients had both optical correction and patching. The values at the baseline were compared to that at one year later. The binarization method was used to determine the total, luminal, and stromal areas of the choroid in the enhanced depth imaging optical coherence tomographic images. The best-corrected visual acuity (BCVA) of the amblyopic eyes was significantly improved after the one-year period. A large luminal area was characteristic of the amblyopic eye at the baseline, and it was significantly reduced after the optical treatment. The stromal area widened significantly in the amblyopic and fellow eyes after one year whereas there were no significant changes in the choroid of the control eyes after one year. After one-year of optical correction, the luminal/stromal ratios in the amblyopic and fellow eyes were decreased and were then not significantly different from that of the normal control eyes. There was a significant and positive correlation between the improvement of the BCVA and the stromal area at the baseline (r = 0.64, P = 0.001). Wearing corrective lenses on the amblyopic eyes improves the BCVA, and the choroidal structure of the amblyopic eye becomes closer to that of the control eyes. The narrowed luminal area is a specific response of the amblyopic eye associated with the correction of the refractive error. The larger stromal area in the amblyopic eyes at the baseline is a predictive factor for improvements of the BCVA.

Kago-Eye2 software for semi-automated segmentation of subfoveal choroid of optical coherence tomographic images.

PURPOSE: To determine the capabilities of the "Kago-Eye2" software to semi-automatically segment the choroid in the optical coherence tomographic (OCT) images. STUDY DESIGN: A cross-sectional, prospective study of 44 healthy volunteers. METHODS: The Kago-eye2 software was developed to detect the border between Choriocapillaris and Sattler's layer (C-S) and between Sattler's layer and Haller's layer (S-H). The intra- and inter-grader agreements were determined for the segmentations made with semi-automated and manual analysis using the Kago-Eye2 software. The inter-method agreements were determined for two independent graders. RESULTS: Forty-four right eyes of 44 heathy volunteers (22 men) with a mean age of 35.0 ± 8.8 years were studied. The intra-grader agreement of the C-S border was 0.97 for grader 1 and 0.892 for grader 2 for the manual segmentation, and 0.908 for grader 1 and 0.842 for grader 2 for the Kago-Eye2 segmentation. For the S-H border, the intra-grader agreement was 0.96 for grader 1 and 0.981 for grader 2 for manual segmentation and 0.855 for grader 1 and 0.839 for grader 2 with the Kago-Eye2. For the C-S and S-H border, the inter-grader agreement was 0.548 and 0.902 for manual segmentation and 0.947 and 0.833 for the Kago-Eye2. The inter-method agreement was 0.565 for the C-S border and 0.759 for the S-H border. CONCLUSION: The Kago-Eye2 software can segment the layers of the subfoveal choroid with good reproducibility and repeatability. We conclude that the Kago-Eye2 software can be used for semi-automatic segmentation of the choroidal layers.

Relationship between retinal artery trajectory and axial length in Japanese school students.

PURPOSE: The trajectories of the supratemporal and infratemporal retinal arteries are associated with the position of the nerve fiber layer defects of glaucomatous eyes. However, no reports have thus far been published on changes in the retinal artery trajectory (RA trajectory) along with growth. Thus, the purpose of this study was to investigate the differences in the RA trajectories of elementary and junior high school students and the associations with axial length (AL). STUDY DESIGN: Prospective cross-sectional observational study. METHODS: In total, 122 right eyes of healthy elementary school students (61 boys, 61 girls) and 170 right eyes of healthy junior high school students (83 boys, 87 girls) were studied. The AL was measured and color fundus photographs were taken, and used for the analysis. The RA trajectory was plotted in the color fundus photographs and fitted to a second-degree polynomial equation, [Formula: see text], using ImageJ. The coefficient "a" represented the steepness of the trajectories. The differences in the RA trajectories and ALs of elementary and junior high school students were determined using the Mann-Whitney test. The association between the RA trajectory and AL was determined using the Spearman rank correlation. RESULTS: The AL and the RA trajectory of the junior high school students were significantly greater than those of the elementary school students (P < 0.001). The RA trajectory was significantly associated with the AL in both elementary (r = 0.26, P = 0.005) and junior high (r = 0.32, P < 0.001) school students. CONCLUSIONS: Junior high school students have a longer AL and narrower RA trajectory than do elementary school students. A longer AL is associated with a narrower RA trajectory in both elementary and junior high school students.

Semi-automated software to measure luminal and stromal areas of choroid in optical coherence tomographic images.

PURPOSE: To determine the capabilities of "EyeGround" software in measuring the choroidal cross sectional areas in optical coherence tomographic (OCT) images. STUDY DESIGN: Cross sectional, prospective study. METHODS: The cross-sectional area of the subfoveal choroid within a 1500 µm diameter circle centered on the fovea was measured both with and without using the EyeGround software in the OCT images. The differences between the evaluation times and the results of the measurements were compared. The inter-rater, intra-rater, inter-method agreements were determined. RESULTS: Fifty-one eyes of 51 healthy subjects were studied: 24 men and 27 women with an average age of 35.0 ± 8.8 years. The time for analyzing a single image was significantly shorter with the software at 3.2±1.1 min than without the software at 12.1±5.1 min (P <0.001). The inter-method correlation efficient for the measurements of the whole choroid was high [0.989, 95% CI (0.981-0.994)]. With the software, the inter-rater correlation efficient was significantly high [0.997, 95% CI (0.995-0.999)], and the intra-rater correlation efficient was also significantly high [0.999, 95% CI (0.999-1.0)]. CONCLUSION: The EyeGround software can measure the choroidal area in the OCT cross sectional images with good reproducibility and in a significantly shorter times. It can be a valuable tool for analyzing the choroid.

Diurnal variations in luminal and stromal areas of choroid in normal eyes.

AIMS: To determine the diurnal variations of the luminal and stromal areas of the choroid in normal eyes. METHODS: This was a prospective observational study of 38 eyes of 38 normal subjects. The blood pressure, heart rate, intraocular pressure and enhanced depth imaging optical coherence tomographic (EDI-OCT) images were recorded every 3 hours between 6:00 and 21:00 hours. The horizontal EDI-OCT images of the subfoveal choroid were converted to binary images. The central choroidal thickness (CCT), total cross-sectional choroidal area, the luminal areas, stromal areas and the ratio of luminal area to total choroidal area (L/C ratio) were determined. RESULTS: There were significant diurnal variations in the CCT, total choroidal area, luminal area and L/C ratio with the maximum values at 6:00 hours and the minimum values at 15:00 hours (p<0.001 for the CCT, p=0.011 for the total choroidal area, p<0.001 for the luminal area and p=0.014 for the L/C ratio). There was no significant variation in the stromal area (p=0.216). The range of fluctuation in the CCT was significantly correlated with that in the luminal area and the total choroidal area (p<0.001). However, there was no significant correlation between the fluctuation range in the CCT and that in the stromal area (p=0.095). There was no statistical relationship between the systemic parameters and the choroidal parameters. CONCLUSIONS: The changes in the luminal area are most likely responsible for the diurnal change in the CCT and subfoveal choroidal area. TRIAL REGISTRATION NUMBER: UMIN000019060, Pre-results.

Correction: Choroidal Structure in Children with Anisohypermetropic Amblyopia Determined by Binarization of Optical Coherence Tomographic Images.

[This corrects the article DOI: 10.1371/journal.pone.0164672.].

Choroidal Structure in Children with Anisohypermetropic Amblyopia Determined by Binarization of Optical Coherence Tomographic Images.

PURPOSE: To compare the choroidal structure of the subfoveal area in the eyes of children with anisohypermetropic amblyopia to that of the fellow eyes and to age-matched controls using a binarization method of the images obtained by enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: This study was performed at Nara Medical University Hospital, Tokushima University Hospital, and Kagoshima University Hospital, Japan. Forty amblyopic eyes with anisohypermetropic amblyopia and their fellow eyes (5.9 ± 2.1 years, mean ± standard deviation), and 103 age-matched controls (6.7 ± 2.4 years) were studied. The control eyes were divided into myopic, emmetropic, and hyperopic eyes. The total choroidal area, luminal area and stromal area of the subfoveal choroid were measured by the binarization method. The luminal/stromal ratio and the axial length of the amblyopic eyes were compared to that of the control eyes. RESULTS: The total choroidal area in the amblyopic eyes was significantly larger than that of the fellow eyes (P = 0.005). The luminal/stromal ratio was significantly larger in the amblyopic eyes than that of the fellow eyes (P<0.001) and the control hyperopic eyes (P<0.001). There was a significant negative correlation between the luminal/stromal ratio and the axial length in the control eyes (r = -0.30, P = 0.001), but no significant correlation was found in the amblyopic eyes. CONCLUSIONS: The choroidal structure of the amblyopic eyes was different from that of the fellow and the control hyperopic eyes. The choroidal changes are related to amblyopia.

Structural Changes of Inner and Outer Choroid in Central Serous Chorioretinopathy Determined by Optical Coherence Tomography.

PURPOSE: To determine the structural changes of the choroid in eyes with central serous chorioretinopathy (CSC) by enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: A retrospective comparative study was performed at two academic institutions. Forty eyes with CSC, their fellow eyes, and 40 eyes of age-matched controls were studied. Subfoveal cross sectional EDI-OCT images were recorded, and the hypo reflective and hyperreflective areas of the inner and outer choroid in the EDI-OCT images were separately measured. The images were analyzed by a binarization method to determine the sizes of the hyporeflective and hyperreflective areas. RESULTS: In the inner choroid, the hyperreflective area was significantly larger in the CSC eyes (35,640±10,229 µm2) than the fellow eyes (22,908±8,522 µm2) and the control eyes (20,630±8,128 µm2; P<0.01 vs control for both, Wilcoxon signed-rank test). In the outer choroid, the hyporeflective area was significantly larger in the CSC eyes (446,549±121,214 µm2) than the control eyes (235,680±97,352 µm2, P<0.01). The average ratio of the hyporeflective area to the total choroidal area was smaller in the CSC eyes (67.0%) than the fellow eyes (76.5%) and the control eyes (76.7%) in the inner choroid (P<0.01, both). However, the ratio was larger in the CSC eyes (75.2%) and fellow eyes (71.7%) than in the control eyes (64.7%) in the outer choroid (P<0.01, both). CONCLUSIONS: The larger hyperreflective area in the inner choroid is related to the inflammation and edema of the stroma of the choroid in the acute stage of CSC. The larger hyporeflective areas in the outer choroid is due to a dilatation of the vascular lumens of the larger blood vessels. These are the essential characteristics of eyes with CSC regardless of the onset.

Changes of choroidal structure after corticosteroid treatment in eyes with Vogt-Koyanagi-Harada disease.

AIMS: To report the changes of the choroidal structure in the enhanced depth imaging optical coherence tomographic (EDI-OCT) images after high-dose corticosteroid treatment for acute Vogt-Koyanagi-Harada (VKH) disease. METHODS: Retrospective, observational case series. Thirty-four eyes of 17 patients with acute VKH disease were examined by EDI-OCT before, and 1, 4 and 52 weeks after the treatment. The EDI-OCT images were binarised by ImageJ, a publicly accessible software. The luminal, stromal and total choroidal areas and ratio of luminal/stromal area (L/S ratio) were measured in the subfoveal choroid of 1500 µm width. The area of the peripapillary atrophy (PPA) was measured in the fundus photographs at 1 and 52 weeks. For statistical analyses, a generalised estimating equation method was used to eliminate the effect of within-subject intereye correlations. RESULTS: Before treatment, the EDI-OCT images could not be binarised because of poor image quality in most of the cases. After treatment, the luminal, stromal and total choroidal areas were significantly decreased during the follow-up period (all p<0.05). The L/S ratio significantly fluctuated over time (p=0.0201), and was significantly lower at 4 weeks than at 1 week (p=0.0158). The L/S ratio at 1 week was significantly correlated with increase in the PPA area, subsequent chronic recurrences and total dose of corticosteroid (p<0.0001, p=0.0006, p=0.0037, respectively). CONCLUSIONS: The L/S ratio measured by binarisation of EDI-OCT images was predictive factor for the progression of PPA, subsequent chronic recurrences and total dose of corticosteroid, and may serve as a marker for degree of choroidal inflammation in the VKH disease.

Soft shell technique during vitrectomy for proliferative vitreoretinopathy.

PURPOSE: To determine whether ophthalmic viscoelastic devices (OVDs) can be used during vitrectomy to prevent perflorocarbon liquid (PFCL) from leaking into the subretinal space through retinal tears in eyes with proliferative vitreoretinopathy (PVR). The OVDs are adhesive materials that can temporally close retinal breaks. We introduce a "soft shell technique", which allows the unfolding of the retina by PFCL. METHODS: We studied five eyes of five patients with proliferative vitreoretinopathy that underwent vitrectomy using the soft shell technique. After removing the core vitreous, the OVDs were carefully injected over the area where confluent retinal folds were formed with possible retinal breaks. This created a soft shell shield on the retina that can prevent the intravitreal PFCL from leaking into the subretinal space. RESULTS: The soft shell technique still allowed the PFCL to unfold the retina even if iatrogenic breaks are present. The high viscosity of OVDs sealed the iatrogenic retinal breaks and thus prevented the PFCL from leaking into the subretinal space during the vitrectomy. All patients had an improvement of the visual acuity, and four eyes had a reattachment of the retina. CONCLUSIONS: Although only five eyes were examined, the success of the soft shell technique indicates that it can be used with PFCL, which facilitates the unfolding of the contracted retina.

Association of retinal thickness and optic disc-to-fovea angle to axial length of young healthy eyes.

AIM: To determine the relationship between the axial length (AL) and the retinal thickness in the posterior pole and to the optic disc-to-fovea (ODF) angle of healthy eyes. PROCEDURES: A prospective, observational cross-sectional study (registration number, UMIN000006040) of 64 healthy right eyes (mean age 26.0±4.5 years) was performed. The thickness of the 64 areas within the central 24° area were measured in the Spectralis spectral domain-optical coherent tomographic images obtained by posterior pole scans. Each area was 3°×3°. The ODF angle was measured in each fundus photograph. The relationships between the AL and the retinal thickness of each of the 64 areas and the ODF angle were investigated by linear regression analyses. RESULTS: The mean AL was 25.0±1.3 mm and the mean ODF angle was 17.2°±1.0°. The average retinal thickness of the four areas around the fovea was constant and not significantly correlated with the AL. However, the retinal thicknesses of 54 of the other 60 areas were significantly and negatively correlated with the AL (R=-0.25 to -0.56, P<0.05). The ODF angle was also constant and not significantly correlated with the AL (R=-0.17, P=0.19). CONCLUSION: The lack of significant correlations between the AL and the retinal thicknesses of the central 6° or the ODF angle suggests that there might be some feedback system to keep the central retinal thickness and ODF angle constant regardless of an elongation of the AL.

Luminal and stromal areas of choroid determined by binarization method of optical coherence tomographic images.

PURPOSE: To determine the proportion of luminal and stromal areas of normal choroids in the optical coherence tomographic (OCT) images obtained by enhanced depth imaging (EDI)-OCT. DESIGN: A prospective, masked, observational cross-sectional study. METHODS: setting: This study was performed at the Kagoshima University Hospital, Japan. STUDY POPULATION: One hundred and eighty right eyes of 180 healthy volunteers (106 women; mean age of 55.9 years) without ocular pathology. observational procedures: The EDI-OCT images of the posterior choroid 7500 µm from the optic disc in the horizontal plane were converted to binary images. The total cross-sectional choroidal area, luminal area, and stromal area of the choroid were measured. MAIN OUTCOME MEASURES: Correlations between clinical factors and each choroidal structure and ratio of luminal/stromal areas were determined. The correlations of each choroidal structure and the age, sex, axial length (AL), and refractive errors were calculated. RESULTS: The mean total cross-sectional choroidal area was 1.84 mm(2) (luminal area 1.21 mm(2) and stromal area 0.63 mm(2)). Multivariate analysis (standardized partial regression coefficient) showed that age (-0.723, P < .001) was significantly correlated with the reduced area of the choroid, and the correlation was greater than that for the AL (-0.408, P < .001). The ratio of luminal/stromal area was significantly reduced in eyes with longer ALs (-0.531, P < .001), and the strength of the correlation was greater than that of age (-0.389, P < .001). CONCLUSIONS: Although both the luminal and the stromal areas decrease with increasing age and with longer ALs, the degree of decrease and areas affected were not the same.

Different Effects of Thrombin on VEGF Secretion, Proliferation, and Permeability in Polarized and Non-polarized Retinal Pigment Epithelial Cells.

We investigated the effect of thrombin on the secretion of vascular endothelial growth factor (VEGF), on cellular proliferation, and on the integrity of the barrier function of polarized retinal pigment epithelial (RPE) cells. In addition, we compared the responses of polarized to that of non-polarized RPE cells. Porcine polarized RPE cells were established using Transwell membranes. The polarization of the RPE cells was determined by their high transepithelial electrical resistance (TER > 200 Ω cm(2)) and by their differential secretion of VEGF (basal direction >apical direction by 2.5×). RPE cells were incubated with thrombin (5-20 U/ml) for 24 h. The concentration of VEGF in the culture medium was measured by enzyme-linked immunosorbent assay, and the TER was measured. Cellular proliferation was assessed by Ki-67 immunostaining. The area of laser-induced choroidal naovascularization (CNV) was measured in rat eyes and compare to that of controls with or without thrombin. Our results showed that thrombin significantly increased VEGF secretion both in polarized and non-polarized RPE cells in a dose-dependent way. Thrombin did not significantly affect the TER or the expression of tight-junctional proteins in polarized RPE cells, but decreased it in non-polarized RPE cells by inducing intercellular gaps. Ki-67-positive cells were observed in non-polarized RPE cells but not in polarized RPE cells as controls. After thrombin exposure, the number of Ki-67-positive cells increased significantly in non-polarized RPE cells but not in polarized RPE cells. The area of CNV was larger in thrombin-injected eye than control eyes. Although thrombin increased VEGF secretion regardless of cell polarity, its effects on proliferation and barrier integrity were dependent upon cell polarity. Cell polarization is an important factor for determining the response of RPE cells to thrombin, and the different responsive patterns to thrombin upon cell polarity might explain the complicated pathology of such diseases as age-related macular degeneration.

Objective determination of optimal number of spectral-domain optical coherence tomographic images of retina to average.

PURPOSE: To determine by objective methods the minimum number of spectral-domain optical coherence tomographic (SD-OCT) images to average to obtain the clearest retinal image. METHODS: SD-OCT Images were obtained from 9 healthy eyes and also from a phantom eye model. The SD-OCT images were obtained by averaging 1, 5, 20, 60, and 100 B-scan images. The reflectivity (mean gray value) of the different retinal layers was evaluated in these images. The image quality was evaluated by the size of the standard deviations (SDs) and the contrast-to-noise ratios (CNRs). A phantom eye model made by TiO2 silicone plates was also examined. RESULTS: The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (P<0.05, post hoc Tukey's honestly significant difference tests). The SD of the automatic real time averaging of 1 (ART = 1) and ART = 5 were significantly larger than the SD of ART = 100 (P<0.05). The SDs of all other averaged numbers were not significantly larger than that of ART = 100. The CNR increased with an increase in the number of images averaged, and there was a significant increase between ART = 1 to 5 and between ART = 5 to 20 (P<0.05). No significant differences in the CNR was observed between ART = 5, ART = 20 and ART = 60. Similar results were obtained with the phantom eye model. CONCLUSIONS: Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.

Blood components and OCT reflectivity evaluated in animal model.

BACKGROUND/PURPOSE: To see the relationship between blood components and optical coherence tomography (OCT) reflectivity using an animal model in which the aqueous humor was substituted by different experimental solutions without changing the integrity of the retina. MATERIALS AND METHODS: The aqueous humor of an enucleated swine eye was replaced with plasma obtained from healthy volunteers. The OCT reflectivity of the anterior chamber filled with each plasma was calculated from individual OCT images, and was expressed by an arbitrary unit (AU). The concentration of blood components such as cholesterol, hemoglobin (Hb) and bilirubin of each individual was measured, and the correlation between each of them and the OCT reflectivity of aqueous humor in an enucleated swine eye was analyzed. Using the same model, the effects of the single plasma component on OCT reflectivity were examined. RESULTS: Blood samples were obtained from 24 individuals. OCT reflectivity was 30.68 ± 14.8 AU (average ± SD), ranging from 11.11 to 60.31 AU. OCT reflectivity correlated significantly with the concentration of triglycerides (R = 0.634, p = 0.001) and total cholesterol (R = 0.488, p = 0.015) using Spearman's rank correlation coefficient. While a partial correlation analysis showed that it correlated significantly with triglyceride (R = 0.60, p = 0.003), but not total cholesterol. OCT reflectivity was highest in a balanced salt solution (BSS) with Hb (average 42.05 AU), followed by fibrinogen (8.08 AU), bilirubin (6.12 AU) and γ-globulin (2.85 AU). Albumin did not increase the reflectivity of the BSS with a normal concentration (1.11 AU) compared to the control BSS alone (0.73 AU). CONCLUSIONS: OCT reflectivity was most strongly affected by the presence of triglycerides among the blood components. Some molecules such as Hb and fibrinogen significantly increase the OCT reflectivity. This information should be helpful for interpreting the OCT findings correctly.

Choroidal structure in normal eyes and after photodynamic therapy determined by binarization of optical coherence tomographic images.

PURPOSE: To determine changes in choroidal structure by binarization of optical coherence tomographic (OCT) images. METHODS: Choroidal images were recorded by enhanced depth imaging OCT. The subfoveal choroidal images were analyzed, and the luminal and interstitial areas were converted to binary images by the Niblack method. The interrater, intrarater, and intersession agreements of the binary images were determined for healthy eyes. In eyes with age-related macular degeneration (AMD), the binary images of the choroid before photodynamic therapy (PDT) were compared to those after PDT. The untreated fellow eyes were studied as controls. RESULTS: In healthy eyes, the average ratio of the luminal to choroidal area was 65.4%. The interrater agreement rate was high, with intraclass correlation coefficient (ICC) 0.985 and 0.988 for the choroid and luminal areas, respectively. The intrarater ICC was 0.996 for the choroid and 0.997 for the luminal areas. The intersession ICC was 0.993 for the choroid and 0.984 for the luminal areas. In eyes with AMD, the subfoveal choroidal area, the luminal area, and the interstitial areas were thinner 6 months after PDT (all P < 0.01, Wilcoxon signed-rank sum test). The ratio of the luminal to choroidal area was significantly decreased to 62.8% (P < 0.01, Wilcoxon signed-rank sum test). The ratio for the fellow eyes was not significantly changed. CONCLUSIONS: The Niblack binarization method can be used to analyze the luminal area of choroid in an OCT image with good repeatability and reproducibility. The change in the subfoveal choroidal area after PDT is due mainly to a decrease in the luminal areas.