Retinal pigment epithelium melanin distribution estimated by polarisation entropy and its association with retinal sensitivity in patients with high myopia.

PURPOSE: To investigate retinal sensitivity of highly myopic eyes without choroidal neovascularisation (CNV) or patchy chorioretinal atrophy (PCA) and investigated its association with anatomical characteristics including melanin distribution at the retinal pigment epithelium (RPE), which was evaluated with polarisation-sensitive optical coherence tomography (PS-OCT). DESIGN: Retrospective consecutive observational cohort study. METHODS: We included highly myopic eyes (refractive error ≤-8.0 dioptres or axial length of ≥26.5 mm) from patients at the University of Tokyo Hospital. Retinal sensitivity was measured by microperimetry at 25 sectors within 6 degrees from the fovea. Depolarisation value, which reflected melanin pigmentation, was measured by a clinical prototype of PS-OCT and was parameterised as polarimetric entropy. Retinal sensitivity or entropy at the RPE in high myopia was compared with emmetropic control subjects. The association of retinal sensitivity with age, axial length, entropy, or choroidal thickness was assessed in per-eye and per-sector analysis. RESULTS: Twenty-three highly myopic eyes (age, 66.6±12.3 years) were included. The average retinal sensitivity was 25.3±3.0 dB, which was significantly decreased compared with the control (p<0.0001). The average entropy at the RPE in the highly myopic eyes was significantly lower than in the control (p<0.0001). Univariate analysis followed by multivariate analysis showed that besides age, axial length or choroidal thickness, RPE entropy was independently associated with retinal sensitivity (ß=4.4; 95% CI 0.5 to 8.3; p=0.03). CONCLUSIONS: Decreased depolarisation at the RPE measured with PS-OCT, which reflected altered melanin pigmentation, was independently associated with reduced retinal sensitivity in patients with early stages of myopic maculopathy without CNV or PCA.

Changes in entropy on polarized-sensitive optical coherence tomography images after therapeutic subthreshold micropulse laser for diabetic macular edema: A pilot study.

PURPOSE: To investigate the dynamics of the healing process after therapeutic subthreshold micropulse laser (SMPL) for diabetic macular edema (DME) using polarization-sensitive optical coherence tomography (PS-OCT). METHODS: Patients with treatment-native or previously-treated DME were prospectively imaged using PS-OCT at baseline, 1, 2, 3, and 6 months. The following outcomes were evaluated: changes in the entropy value per unit area (pixel2) in the retinal pigment epithelium (RPE) on the B-scan image; changes in the entropy value in each stratified layer (retina, RPE, choroid) based on the ETDRS grid circle overlaid with en face entropy mapping, not only the whole ETDRS grid area but also a sector irradiated by the SMPL; and the relationship between edema reduction and entropy changes. RESULTS: A total of 11 eyes of 11 consecutive DME patients were enrolled. No visible signs of SMPL treatment were detected on PS-OCT images. The entropy value per unit area (pixel2) in the RPE tended to decrease at 3 and 6 months from baseline (35.8 ± 17.0 vs 26.1 ± 9.8, P = 0.14; vs 28.2 ± 18.3, P = 0.14). Based on the en face entropy mapping, the overall entropy value did not change in each layer in the whole ETDRS grid; however, decrease of entropy in the RPE was observed at 2, 3, and 6 months post-treatment within the SMPL-irradiated sectors (P < 0.01, each). There was a positive correlation between the change rate of retinal thickness and that of entropy in the RPE within the SMPL-irradiated sector at 6 months (r2 = 0.19, P = 0.039). CONCLUSION: Entropy measured using PS-OCT may be a new parameter that facilitates objective monitoring of SMPL-induced functional changes in the RPE that could not previously be assessed directly. This may contribute to a more promising therapeutic evaluation of DME. CLINICAL TRIAL: This clinical study was registered in UMIN-CTR (ID: UMIN000042420).

Assessment of macular function in patients with non-vascularized pigment epithelial detachment.

Non-vascularized pigment epithelial detachments (PED) are usually associated with dry age-related macular degeneration (AMD). In this study, we aimed to investigate the correlation between visual function and morphologic parameters. Seventeen eyes of eleven patients with non-vascularized AMD were enrolled. In addition to conventional optical coherence tomography (OCT), polarization-sensitive optical coherence tomography (PS-OCT) measurements were performed by evaluating the regularity of retinal pigment epithelium (RPE) entropy within the PED area. Retinal sensitivity was measured with MP-3 microperimetry, and retinal sensitivities within (RSin) and outside (RSout) the PED area were calculated. The relationship between OCT parameters and visual function was analyzed. As a result, there was a significant difference between the RSin and RSout (p < 0.001, Wilcoxon signed rank test). Moreover, RSin was significantly related to logMAR VA (p = 0.033, linear mixed model). The regularity of RPE entropy was significantly related to visual acuity and RSin (p = 0.00038, p = 0.031, linear mixed model), although neither the height nor area of PED correlated with visual function. Our results suggest that retinal sensitivity is significantly deteriorated within the PED area and RPE entropy measured with PS-OCT was closely related to visual function in eyes with non-vascularized PED.

Three-Dimensional Distribution Of Fundus Depolarization and Associating Factors Measured Using Polarization-Sensitive Optical Coherence Tomography.

Purpose: To investigate the three-dimensional distribution and associating demographic factors of depolarization, using polarization-sensitive optical coherence tomography (PS-OCT), to evaluate melanin pigmentation in the retinal pigment epithelium (RPE) and choroid in healthy eyes. Methods: In total, 39 unaffected healthy eyes of 39 subjects were examined using a PS-OCT clinical prototype. The degree of depolarization, expressed as the polarimetric entropy, was assessed in the RPE, the superficial and the total choroid layer, especially in the center, the inner, or the outer areas centered at the fovea. The values and their association with the demographic data were analyzed. Near-infrared fundus autofluorescence (NIRAF) was also used, in the same manner, for the comparison. Twenty-eight of 39 eyes were measured twice to evaluate intrasession repeatability. Results: Both the polarimetric entropy in the RPE and the gray level in NIRAF, decreased from the center to the periphery (P < 0.001). The polarimetric entropy in the RPE was significantly associated with age in each area (P ≤ 0.001). In the RPE and the superficial choroid, the polarimetric entropy was negatively associated with axial length in each area (P ≤ 0.002). The intraclass correlation coefficient of the polarimetric entropy in the same session was excellent in each area of the RPE, superficial choroid, or total choroid layer (0.94-0.98). Conclusions: The distribution of fundus melanin pigment-related depolarization was evaluated using PS-OCT. The depolarization was associated with the subjects' demographic data, such as age or axial length. Translational Relevance: The presented information in healthy eyes provides an essential basis for the investigation into a variety of chorioretinal pathologies.

Imaging of a retinal pigment epithelium aperture using polarization-sensitive optical coherence tomography.

PURPOSE: To evaluate cases with a retinal pigment epithelium (RPE) aperture using polarization-sensitive optical coherence tomography (PS-OCT). STUDY DESIGN: Retrospective consecutive case series. METHODS: A retrospective study that included three eyes (three patients) with RPE aperture and age-related macular degeneration (AMD) evaluated at the Macular Clinic in Tokyo University Hospital. A three-dimensional dataset of depolarization information was obtained with a clinical prototype of PS-OCT. RESULTS: All patients were categorized as intermediate AMD. RPE apertures were identified with PS-OCT as discontinuities of depolarization in the RPE layer of the pigment epithelial detachment (PED). A nonuniform decrease of depolarization in the RPE layer was also observed around the aperture. Two findings were observed above the aperture, intraretinal focal areas with high reflectivity and increased depolarization and subretinal bands with moderate reflectivity and low depolarization. Retinal sensitivity according to fundus microperimetry measured at 25 points was significantly associated with the degree of depolarization at the corresponding area (r-square = 0.60, p = 0.0001). CONCLUSION: The RPE aperture was characterized as a round discontinuity of depolarization. The findings with PS-OCT suggest atrophic changes in the overlying RPE of the PED. The degree of depolarization was associated with retinal sensitivity. The current results indicate that RPE apertures developed within the spectrum of atrophic AMD.

Melanin concentration and depolarization metrics measurement by polarization-sensitive optical coherence tomography.

Imaging of melanin in the eye is important as the melanin is structurally associated with some ocular diseases, such as age-related macular degeneration. Although optical coherence tomography (OCT) cannot distinguish tissues containing the melanin from other tissues intrinsically, polarization-sensitive OCT (PS-OCT) can detect the melanin through spatial depolarization of the backscattered light from the melanin granules. Entropy is one of the depolarization metrics that can be used to detect malanin granules in PS-OCT and valuable quantitative information on ocular tissue abnormalities can be retrived by correlating entropy with the melanin concentration. In this study, we investigate a relationship between the melanin concentration and some depolarization metrics including the entropy, and show that the entropy is linearly proportional to the melanin concentration in double logarithmic scale when noise bias is corrected for the entropy. In addition, we also confirm that the entropy does not depend on the incident state of polarization using the experimental data, which is one of important attributes that depolarization metrics should have. The dependence on the incident state of polarization is also analyzed for other depolarization metrics.