Influence of Aberration-Free, Narrowband Light on the Choroidal Thickness and Eye Length

Purpose

To determine whether light chromaticity without defocus induced by longitudinal chromatic aberration (LCA) is sufficient to regulate eye growth.

Methods

An interferometric setup based on a spatial light modulator was used to illuminate the dominant eyes of 23 participants for 30 minutes with three aberration-free stimulation conditions: (1) short wavelength (450 nm), (2) long wavelength (638 nm), and (3) broadband light (450-700 nm), covering a retinal area of 12°. The non-dominant eye was occluded and remained as the control eye. Axial length and choroidal thickness were measured before and after the illumination period.

Results

Axial length increased significantly from baseline for short-wavelength (P < 0.01, 7.4 ± 2.2 µm) and long-wavelength (P = 0.01, 4.8 ± 1.7 µm) light. The broadband condition also showed an increase in axial length with no significance (P = 0.08, 5.1 ± 3.5 µm). The choroidal thickness significantly decreased in the case of long-wavelength light (P < 0.01, -5.7 ± 2.2 µm), but there was no significant change after short-wavelength and broadband illumination. The axial length and choroidal thickness did not differ significantly between the test and control eyes or between the illumination conditions (all P > 0.05). Also, the illuminated versus non-illuminated choroidal zone did not show a significant difference (all P > 0.05).

Conclusions

All stimulation conditions with short- and long-wavelength light and broadband light led to axial elongation and choroidal thinning. Therefore, light chromaticity without defocus induced by LCA is suggested to be insufficient to regulate eye growth.

Translational Relevance

This study helps in understanding if light chromaticity alone is a sufficient regulator of eye growth.

Assessment of macular choroidal and retinal thickness: a cohort study in Tibetan healthy children

This research investigates the distribution, progressive changes, and contributing factors of macular choroidal and retinal thickness in Tibetan children utilizing swept-source optical coherence tomography (SS-OCT). The Lhasa childhood study recruited 1632 students from seven primary schools in Lhasa. These participants underwent OCT and ophthalmological evaluations, encompassing retinal and choroidal thickness measurements, refractive error, axial length (AL), and systemic examinations. The median age of the scholars was 8.57 ± 0.50 years with a median spherical equivalent (SE) of 0.19 ± 1.28D. Multivariate regression analysis revealed that thinner macular choroid thickness was correlated with lower value of SE, worse best-corrected visual acuity, higher mean arterial blood pressure (MABP) and boys, while retinal thickness was associated with better image quality and lower value of SE. The choroid and retina were significantly thinner in myopic children. SE was positively related to the thickness of all choroidal and full retinal subregions. In comparison to baseline data from 20 months prior, most regions of the full retina had significantly thinned. Choroidal thickness of Tibetan children is thinner than that of same-age children from other regions. Thinning of retina, the outer-sector GCC and GCIPL may be specified as a follow-up and prognostic indicator for myopia.

The suprachoroidal space in patients affected by retinitis pigmentosa

BACKGROUND AND OBJECTIVE

The Suprachoroidal Space (SCS) is a theoretical structure which can be demonstrated between the inner border of the sclera and the outer boundary of the choroid. SCS is being studied for its potential uses as a route for drug delivery and innovative surgical techniques for the treatment of many retinal diseases. Retinitis pigmentosa (RP) is a group of inherited eye disorders characterized by a gradual loss of photoreceptors, resulting in vision impairment, which typically presents as night blindness and progressive visual field loss. The purpose of the study is to define the morphology of outer choroidal margins by means of SS-OCT in RP.

MATERIAL AND METHOD

This is a retrospective observational study designed to evaluate the presence of SCS in RP. We performed Swept Source optical coherence tomography (SS-OCT) in a group of 55 patients affected by RP (26 males and 29 females, 110 eyes) with a mean age of 51.8 ± 13.7 years. In the control group, we included 28 healthy subjects (6 males and 22 females, 56 eyes) with a mean age of 48,8 ± 16,6 years.

RESULTS

OCT scans allowed the outer choroidal margin and inner scleral margin to be delineated with certainty in all 110 eyes. In the RP group SCS was detected in 47 of 110 eyes (42,7%), in the control group SCS was detected in 11 eyes (19,6%). Subjects with SCS visible (RP group) had reduced retinal thickness (168.4 µm) compared to those with not visible SCL (211.2 µm, P = .007).

CONCLUSIONS

SS-OCT can be successfully applied to assess the presence of SCS in RP and the high rate of SCS found in the RP patients is encouraging when considering future innovative therapies.

Vascular Choroidal Alterations in Uncomplicated Third-Trimester Pregnancy

(1) Purpose: To evaluate the anatomy and perfusion of choroidal substructures in third-trimester pregnant women using optical coherence tomography (OCT) and OCT angiography (OCTA) imaging. (2) Methods: In this cross-sectional study, women in their third trimester of uncomplicated pregnancy and non-pregnant age-matched women were recruited. Participants underwent enhanced depth imaging (EDI) OCT and OCTA. Subfoveal choroidal thickness (SFCT), as well as choroidal sublayer perfusion, were compared between groups. (3) Results: In total, 26 eyes of 26 pregnant and 26 eyes of 26 non-pregnant women were included. The median age in both groups was 29 years. The median SFCT was 332 (211–469) µm in the pregnant group and 371.5 (224–466) µm in the non-pregnant cohort (p = 0.018). The median choriocapillaris perfusion (CCP) was significantly lower in the pregnant group (46% vs. 48%, p = 0.039). Moreover, Haller’s layer perfusion correlated significantly with mean arterial pressure in non-pregnant women (CC = 0.430, p = 0.028) but not in pregnant ones (CC = 0.054, p = 0.792). (4) Conclusions: SFCT was found to be thinner and CCP was lower in third-trimester pregnant women. Hormonal changes during pregnancy and consecutive impacts on autoregulation of small choroidal vessels might play an important role. Therefore, altered choroidal measurements during third-trimester pregnancy should be carefully evaluated as, to some extent, it could be a normal physiological change.

Choroidal thickness assessment in keratoconus patients treated with cross-linking compared to healthy population

PURPOSE

To analyze the choroidal thickness between patients with keratoconus undergoing cross-linking treatment and a healthy population, as well as to determine the factors that influence choroidal thickness.

METHODS

This was an observational, analytical, case-control study that was conducted from February 2021 to June 2021. Choroidal thickness was measured at different locations, including the subfoveal, nasal (1000 μm), temporal (1000 μm), superior (1000 μm) and inferior (1000 μm) locations using a Spectral-domain optical coherence tomography with enhanced depth imaging, which allowed us to obtain horizontal and vertical B-scans centered on the fovea.

RESULTS

This study included 21 patients with keratoconus (mean age, 21.86 ± 5.28 years) and 28 healthy patients (mean age, 24.21 ± 4.71 years). Choroidal thickness was significantly greater in patients with keratoconus than in healthy patients in each of the following measured locations: subfoveal (P < 0.001); nasal (1000 μm) (P < 0.001), temporal (1000 μm) (P < 0.001), superior (1000 μm) (P < 0.001) and inferior (1000 μm) (P < 0.001) locations. Variables such as age (ρ = - 0.09; P = 0.50) and refraction (ρ = 0.14; P = 0.34) were not found to be associated with choroidal thickness. In a stepwise multiple linear regression, the group was the single variable correlated with choroidal thickness (β = 0.88; P < 0.001).

CONCLUSION

Choroidal thickness is thicker in keratoconus patients treated with cross-linking than in the healthy population. This finding could be associated with inflammatory choroidal mechanisms in keratoconus patients, but more studies are needed. Age and refractive error do not seem to influence choroidal thickness.

NEW INSIGHTS INTO THE ASSOCIATION BETWEEN CHOROIDAL VESSELS AND CHORIOCAPILLARIS IN NORMAL EYES

PURPOSE

To determine the relationship between large-sized and medium-sized choroidal vessels and choriocapillaris using the three-dimensional choroidal vascularity index (3D CVI) and percentage of flow deficits (FD%).

METHODS

Prospective observational study. The main outcome measures included choroidal volume parameters (3D CVI, mean choroidal thickness, total choroidal volume, choroidal luminal volume, and choroidal stromal volume), choriocapillaris parameters (FD%, average area of FD, and FD count), and age and axial length.

RESULTS

A total of 63 healthy individuals with an average age of 40.60 ± 12.32 years were included in this study. Univariate analysis showed that FD% (R = 0.295, P = 0.019) and area of FD (R = 0.276, P = 0.028) were significantly positively associated with 3D CVI, and FD count was negatively associated with 3D CVI (R = -0.297, P = 0.018). After adjusting for age and axial length, a significant correlation between FD% and 3D CVI (R = 0.264, P = 0.039) and between area of FD and 3D CVI remained (R = 0.267, P = 0.037). However, no significant correlation was found between FD count and 3D CVI after adjusting for axial length (R = -0.220, P = 0.085).

CONCLUSION

In healthy individuals, choroidal vessel dilatation as suggested by elevated 3D CVI may lead to decreased choriocapillaris perfusion, which was correlated with an enlarged area of FD in choriocapillaris.

A new optical coherence tomography method for subfoveal choroidal thickness measurement: A single-center observational study

Several macular pathologies are associated with choroidal vascular supply and thus require choroidal thickness evaluation. However, there is no standard subfoveal choroidal thickness (SFCT) measurement method. This study investigated a new method of SFCT measurement, using optical coherence tomography.This is a single-center observational study. Eighty-two senior medical students participated as observers and independently measured the SFCT on 5 standard optical coherence tomography images of healthy adults in a tertiary care setting. They used 3 different methods: the observer's own method, the conventional method, perpendicular to the retinal pigment epithelium, and the new method, along a virtual line connecting the umbo with the most elevated point of the ellipsoid. Additionally, the SFCT angle-the angle between the measurement line and the vertical line of the image-was measured and compared between methods. The intraclass correlation coefficient was used to determine interpersonal variability.The intraclass correlation coefficients for SFCT, measured using methods 1, 2, and 3, were 0.853, 0.880, and 0.896, respectively (P < .001 for all). Method 3 was the highest. The intraclass correlation coefficients of the SFCT angles were 0.647, 0.842, and 0.307, respectively (P < .001 for all).The new method showed the lowest interpersonal variability and could therefore be a reliable standard for SFCT measurement, even in foveae with a steep slope on optical coherence tomography.Trial registration: Not applicable.

Choroidal Thickness in Young Adults and its Association with Visual Acuity

PURPOSE

To describe the choroidal thickness (ChT) in a large sample of young adults with the aim of establishing a normative ChT profile reference in this demographic cohort and explore its association with best-corrected visual acuity (BCVA).

DESIGN

Cross-sectional study.

METHODS

From a single center, 741 young adults (19-30 years of age, 49% male) were recruited to undergo a comprehensive ophthalmic examination, including BCVA measurement, post-cycloplegic autorefraction, ocular biometry, tonometry, and spectral-domain optical coherence tomography (SD-OCT) imaging. The enhanced depth imaging mode on the SD-OCT was used. The main outcome measure was the central macular ChT (0.5-mm radius around the fovea). The ChTs at the inner (between 0.5-mm and 1.5-mm radius) and outer macular rings (between 1.5-mm and 2.5-mm radius) were also measured.

RESULTS

The median central macular ChT was 370 μm (interquartile range 312-406 μm). The choroid was thickest at the superior-inner, inferior-inner, and central macular regions (370-373 μm) and thinnest nasally at the outer macular region (median 256 μm). Decreased central macular ChT was associated with younger age, female sex, nonwhite ethnicities, and myopia (P ≤ .013). There was a significant association between better BCVA and increased central macular ChT (P < .001), after adjusting for age, sex, ethnicity, and ocular measures. His relationship was only apparent in eyes with central macular ChTs <300 μm (P = .019) and absent in eyes with ChTs >300 μm.

CONCLUSIONS

The central ChT of young adults was 370 μm. There was a significant association between worse BCVA and thinner choroids below a threshold of 300 μm, raising the possibility that ChT could be predictive of visual function.

Determination of Referential Rates for Optical Coherence Tomography and Optical Coherence Tomography Angiography Flow Deficits in the Macular Choriocapillaris in Ophthalmologically Healthy Children

Background and Objectives: Despite the growing number of new research publications, normative references for children's optical coherence tomography (OCT) parameters are still not completed. We chose to explore this topic because of the lack of normative parameters that is due to an improvement in different technologies and instruments. Our aim was to determine referential rates of retinal nerve fiber layer (RNFL) thickness and flow deficits (FD%) in the macular choriocapillaris (CC) in normal eyes of ophthalmologically healthy children. Materials and Methods: Ophthalmologically healthy 8- to 14-year-old individuals participated (n = 75) in this study. OCT images were taken using an swept-source-OCT (SS-OCT) instrument (DRI-OCT Triton, Topcon, Tokyo, Japan). The early treatment diabetic retinopathy study (EDTRS) grid (6 × 6 mm) divided the RNFL into the thickness maps. The FD% values of the CC were calculated on the 3 × 3-mm scans in a 1-mm circle (C1), 1.5-mm rim (R1.5), and the entire 2.5-mm circle (C2.5), and on the 6 x 6-mm scans in a 1-mm circle (C1), 1.5-mm rim (R1.5), the entire 2.5-mm circle (C2.5), 2.5-mm rim (R2.5), and 5-mm circle (C5). Results: Both scan quantifications of FD% in the C1, C2.5, and R1.5 sectors were similar, but the 6 × 6-mm scan measurements were statistically significantly smaller than the 3 × 3-mm ones. Significant moderate correlations were found between axial length (AxL) and FD% in the 6 × 6-mm scans, namely C1 (r = -0.347, p = 0.002), C2.5 (r = -0.337, p = 0.003), R1.5 (r = -0.328, p = 0.004), R2.5 (r = -0.306, p = 0.008), and C5 (r = -0.314, p = 0.006). Conclusions: The thinnest RNFL layers were on the temporal and nasal sides. FD% values in the C1, C2.5, and R1.5 sectors were similar between the 3 × 3-mm and 6 × 6-mm scans. The negative moderate correlations between AxL and FD% were found in all C1, C2.5, C5, R1.5, and R2.5 sectors of the 6 × 6-mm scans. Further prospective studies are needed to determine more accurate normative references for children's OCT parameters.

Automatic choroidal segmentation in OCT images using supervised deep learning methods

The analysis of the choroid in the eye is crucial for our understanding of a range of ocular diseases and physiological processes. Optical coherence tomography (OCT) imaging provides the ability to capture highly detailed cross-sectional images of the choroid yet only a very limited number of commercial OCT instruments provide methods for automatic segmentation of choroidal tissue. Manual annotation of the choroidal boundaries is often performed but this is impractical due to the lengthy time taken to analyse large volumes of images. Therefore, there is a pressing need for reliable and accurate methods to automatically segment choroidal tissue boundaries in OCT images. In this work, a variety of patch-based and fully-convolutional deep learning methods are proposed to accurately determine the location of the choroidal boundaries of interest. The effect of network architecture, patch-size and contrast enhancement methods was tested to better understand the optimal architecture and approach to maximize performance. The results are compared with manual boundary segmentation used as a ground-truth, as well as with a standard image analysis technique. Results of total retinal layer segmentation are also presented for comparison purposes. The findings presented here demonstrate the benefit of deep learning methods for segmentation of the chorio-retinal boundary analysis in OCT images.

[Choroidal thickness in preschool children]

Objective: To estimate the choroidal thickness (CT) in healthy children aged 2-6 years old and its relation to axial length, age and gender. Methods: Cross-sectional study. CT was assessed using spectral domain optical coherence tomography (OCT) in 126 children aged 2 to 6 years. CT was measured at nine locations, including the subfovea and 1 mm and 3 mm nasal, temporal, superior and inferior to the fovea. Results: Mean subfoveal choroidal thickness (SFCT) was 331.56±62.03 μm. The choroid was thickest at the subfoveal and 1 mm temporal area, and thinner nasally compared to temporally, superiorly and inferiorly. No statistical significance of SFCT between male and female was noted. Stepwise multiple regression analysis revealed that axial length and age were associated significantly with SFCT (P=0.00), while there was no detectable effect of sex on SFCT (P=0.94). Conclusions: Choroidal thickness was negatively correlated to axial length and positively correlated to age in preschool children. The development of the choroid in early childhood offset the effect of the expansion of eyes. Gender played a minor role in the choroidal development in early childhood. (Chin J Ophthalmol, 2019, 55:111-114).

Medical and Surgical Applications for the Suprachoroidal Space

In recent years, advances in ocular imaging, drug delivery, and ophthalmic surgery have allowed for better visualization and access to the suprachoroidal space. Although previously considered as only a potential space, the suprachoroidal space may serve as a route for drug delivery to the posterior pole, an egress for glaucoma drainage devices, a location for temporary buckling, and a site for prosthesis implantation. Drugs delivered to the suprachoroidal space may achieve higher concentrations in the retina while minimizing exposure to anterior segment tissues, potentially reducing risks of glaucoma or cataracts. Finally, advanced multimodal imaging now allows not only a better understanding of the physiology of the suprachoroid, but also in vivo monitoring of pathologies and drug delivery to the suprachoroidal space. Here, we discuss the newest developments in the medical and surgical applications of this space with potential.

Choroidal thickness changes in non-treated acute and ranibizumab-treated chronic central serous chorioretinopathy

To evaluate the changes in subfoveal retinal, and choroidal thicknesses (CT) in the non-treated acute and the ranibizumab-treated chronic central serous chorioretinopathy (CSCR) patients.This retrospective study included 32 eyes of 32 consecutive patients with CSCR. There were 12 patients who presented with a spontaneous resolution of CSCR (Group 1) and 20 patients who were treated with ranibizumab for persistent subretinal fluid (SRF) (Group 2). Optical coherence tomography (OCT) imaging of subfoveal retinal thickness and enhanced depth imaging OCT of CT at subfoveal; at nasal and temporal 500 μm (T500); at nasal and temporal 1500 μm (T1500) were analyzed. The Student t test and multivariate analysis were used to compare variables within and between groups, respectively and correlations were analyzed using Pearson correlation coefficient. A P value of P < .05 was accepted as significant.The mean patient age was 38.94 ± 8.41 years (range, 20-53 years). Female/male ratio was 4/28. The mean duration of follow-up was 21.6 ± 8.2 months in the chronic CSCR group. Visual acuity improved and central foveal thickness (FT) decreased significantly in both groups. CT decreased significantly only at nasal 1500 μm (N1500) in the acute group and at all measured points in the chronic group compared with baseline, except at T500 (P = .07). No significant difference in central FT was detected between the 2 groups. Compared with the acute group, baseline subfoveal CT was significantly higher in chronic patients. There was a significant difference between the groups in baseline and final CT at T500. No significant difference was found at T1500. At nasal 500 μm and N1500, the difference between the groups was significant only for final CT values.Chronic CSCR was associated with higher baseline CT values in the subfoveal region and at T500. CT significantly decreased at most of the measured points in ranibizumab-treated chronic CSCR patients, whereas it significantly decreased only at 1 point in spontaneously resolved acute CSCR patients.

Macular choroidal thickness and peripapillary retinal nerve fiber layer thickness in normal adults and patients with optic atrophy due to acute idiopathic demyelinating optic neuritis

Purpose

To evaluate the association between macular choroidal thickness and peripapillary RNFL thickness in patients with optic atrophy due to acute idiopathic demyelinating optic neuritis and in normal controls using spectral domain optical coherence tomography (SD-OCT).

Methods

We performed SD-OCT peripapillary RNFL circular scan centered on the optic disc with horizontal and vertical crosshair scans through the fovea using the enhanced depth technique in 62 eyes with optic atrophy due to acute idiopathic demyelinating optic neuritis and 86 eyes of normal controls. The association between RNFL thickness and macular choroidal thickness measurements was assessed.

Results

The mean age was 43 ± 14 years (mean ± SD) in patients with optic atrophy and 45 ± 16 years in healthy controls (p = 0.791). There was a significant association between nasal peripapillary RNFL thickness and choroidal thickness at 3.0 mm nasal to the foveal center in patients with optic atrophy in multivariate analysis (estimate = 1.398, p = 0.011). In controls, there were significant associations between global average, superior, and inferior peripapillary RNFL thickness and choroidal thickness at 3.0 mm superior to the foveal center (estimate = -60.112, p = 0.044, estimate = 15.821, p = 7.312, and estimate = 15.203, p = 7.222, respectively).

Conclusions

Our SD-OCT data revealed that there was a significant association between peripapillary RNFL thickness and macular choroidal thickness in patients with optic atrophy due to acute idiopathic demyelinating optic neuritis and in controls, although the mechanism remained unclear. The difference in the pattern of association between patients with optic atrophy and controls suggests that optic atrophy caused by acute idiopathic demyelinating optic neuritis could affect the pattern of association between peripapillary RNFL thickness and macular choroidal thickness.

Changes in Subfoveal Choroidal Thickness During Pregnancy and After Delivery

BACKGROUND AND OBJECTIVE

This study was performed to investigate longitudinal changes in the subfoveal choroidal thickness (SFCT) during pregnancy and after delivery.

PATIENTS AND METHODS

The SFCT was measured in the first and third trimesters, shortly after delivery, and 1 month after delivery in 25 eyes of 25 women. Enhanced depth imaging optical coherence tomography was used for measurement.

RESULTS

The mean SFCT was 347 μm ± 86 μm, 329 μm ± 81 μm, 333 μm ± 81 μm, and 330 μm ± 87 μm in the first and third trimesters, shortly after delivery, and 1 month after delivery, respectively. The SFCT in the first trimester was significantly greater than that in the third trimester, shortly after delivery, and 1 month after delivery.

CONCLUSIONS

This study indicates that the SFCT is greater in the first trimester and decreases in the third trimester of pregnancy. The SFCT does not subsequently change until 1 month after delivery. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:816-821.].

Early post-treatment choroidal thickness to alert sunset glow fundus in patients with Vogt-Koyanagi-Harada disease treated with systemic corticosteroids

Purpose

To determine if early post-treatment central choroidal thickness (CCT) changes can predict sunset glow fundus (SGF) development in patients with Vogt-Koyanagi-Harada (VKH) disease treated using systemic corticosteroids.

Methods

This retrospective case series included 39 eyes of 21 treatment-naïve patients with acute VKH disease who could be followed up for more than 12 months after systemic corticosteroid therapy. The eyes were divided into two groups according to whether SGF was present or absent at 12 months (9 eyes of 5 patients versus 30 eyes of 16 patients, respectively). Using enhanced depth imaging optical coherence tomography, CCT values were measured before treatment, then at 1 week and 1 and 3 months after treatment in both groups and compared between the two groups.

Results

Development of SGF was found 4–11 months after treatment. Mean post-treatment CCT decreased significantly at all examinations compared with baseline in both groups, along with resolution of serous retinal detachment. One week after treatment, mean CCT was significantly higher in eyes with SGF than in those without (P = 0.024). SGF was present at 12 months in 9 of 22 eyes with CCT values > 410 μm at 1 week after starting treatment, in contrast with none of 17 eyes with CCT ≤ 410 μm at this time (P = 0.003).

Conclusions

The current study suggested the potential validity of early post-treatment CCT as a feasible index to alert future progression to SGF in patients with VKH disease treated using systemic corticosteroids.

Past, Present, and Future Concepts of the Choroidal Scleral Interface Morphology on Optical Coherence Tomography

The choroid is the most vascular tissue in the eye and it has been implicated in the pathophysiology of a variety of ocular diseases. A new era of research in the choroid began with the improved ability to visualize this layer and its inner and outer boundaries using spectral domain optical coherence tomography (OCT) with enhanced depth imaging and swept source OCT. The accuracy and precision of qualitative and quan-titative assessments of the choroidal layer support the potential use of OCT-derived choroidal parameters for diagnosis, monitoring of disease progression, planning surgical access, and evaluating treatment response. Although there is increasing interest in measuring choroidal thickness, there is currently no consensus nomenclature to classify choroidal layers and boundaries. Furthermore, the definition and description of the choroidal scleral interface is inconsistent in the literature, contributing to interstudy variation in choroidal thickness measurements. The purpose of this review is to provide an overview of the literature on the definition of choroidal layers and choroidal scleral boundary, review the discrepan-cies, and harmonize the terminology so that a consensus nomenclature can be proposed.

The effect of topical atropine on the choroidal thickness of healthy children

The purpose of the current study was to investigate the effect of topical atropine on choroidal thickness using spectral-domain optical coherence tomography. A total of 30 healthy eyes from 30 children were analyzed in this study. A single drop of 1% atropine gel was administered twice daily for a week. Choroidal thickness (CT) was measured using SD-OCT, and changes in CT before and after administration of the eye drops were analyzed at the subfovea and at 1.0-mm intervals (up to 3.0 mm) from the fovea at superior, inferior, nasal, and temporal locations. Pre- and post-cycloplegic axial length (AL) was also measured using the IOLMaster. We observed that administration of 1% atropine gel led to a significant increase in the choroidal thickness under the fovea and at all intervals from the fovea. The greatest change in CT was observed in the inferior meridian, while the nasal meridian exhibited the least change. AL did not significantly differ before and after cycloplegia, and there was no significant correlation between the changes in AL and subfoveal CT. It was concluded that administration of 1% atropine gel can significantly increase CT in the eyes of young Chinese children, albeit with different magnitude at different locations.

Repeatability of Choroidal Thickness Measurements on Enhanced Depth Imaging Optical Coherence Tomography Using Different Posterior Boundaries

PURPOSE

To assess the reliability of manual choroidal thickness measurements by comparing different posterior boundary definitions of the choroidal-scleral junction on enhanced depth imaging optical coherence tomography (EDI-OCT).

DESIGN

Reliability analysis.

METHODS

Two graders marked the choroidal-scleral junction with segmentation software using different posterior boundaries: (1) the outer border of the choroidal vessel lumen, (2) the outer border of the choroid stroma, and (3) the inner border of the sclera, to measure the vascular choroidal thickness (VCT), stromal choroidal thickness (SCT), and total choroidal thickness (TCT), respectively. Measurements were taken at 0.5-mm intervals from 1.5 mm nasal to 1.5 mm temporal to the fovea, and averaged continuously across the central 3 mm of the macula. Intraclass correlation coefficient (ICC) and coefficient of reliability (CR) were compared to assess intergrader and intragrader reliability.

RESULTS

Choroidal thickness measurements varied significantly with different posterior boundaries (P < .001 for all). Intergrader ICCs were greater for SCT (0.959-0.980) than for TCT (0.928-0.963) and VCT (0.750-0.869), even in eyes where choroidal-scleral junction visibility was <75%. Intergrader CRs were lower for SCT (41.40-62.31) than for TCT (61.13-74.24) or VCT (72.44-115.11). ICCs and CRs showed greater reliability for averaged VCT, SCT, or TCT measurements than at individual locations. Intragrader ICCs and CRs were comparable to intergrader values.

CONCLUSIONS

Choroidal thickness measurements are more reproducible when measured to the border of the choroid stroma (SCT) than the vascular lumen (VCT) or sclera (TCT).

Age-Dependent Morphologic Alterations in the Outer Retinal and Choroidal Thicknesses Using Swept Source Optical Coherence Tomography

Purpose

To evaluate the age-dependent morphologic alterations in the outer retina and choroid at the macula using swept-source optical coherence tomography (OCT).

Methods

Thirty eyes (30 normal subjects; average age, 49 years) were examined; five (age range, third-eighth decades of life) had refractive errors of ±2 diopters or less and no fundus abnormalities. An Early Treatment Diabetic Retinopathy Study (ETDRS) map of the outer retinal and choroidal thickness was constructed using swept-source OCT. The outer retinal and choroidal segmentation lines were drawn automatically, partially manually, within 6 millimeters of the macula.

Results

The mean outer retinal and choroidal thicknesses in the 6-millimeter-diameter circle were 145±13 and 236±68 microns, respectively. The choroidal thickness and age were negatively (r = -0.66, P<0.01) correlated; the outer retinal thickness and age were not correlated (r = -0.16, P = 0.39). The outer retinal and choroidal thicknesses in the ETDRS map were not correlated (r = -0.13, P = 0.49) within 1 millimeter but correlated (r = 0.32, P<0.01) within 6 millimeters.

Conclusions

The choroid thins with aging. The outer retina remains stable. Outer retina and choroid are correlated in the entire macula except for the center. ETDRS map can be useful for evaluation of the morphologic relationship between the outer retina and choroid.

Correlation Between Choroidal Thickness and Ciliary Artery Blood Flow Velocity in Normal Subjects

BACKGROUND AND OBJECTIVE

To study the correlation between the choroidal thickness (CT) measured by spectral-domain optical coherence tomography (SD-OCT) and retrobulbar blood flow measured by color Doppler flowmetry (CD) in normal subjects.

PATIENTS AND METHODS

Healthy subjects underwent enhanced-depth imaging SD-OCT and CD using a linear 6 MHz to 18 MHz transducer. The maximal peak systolic velocity and resistance index (RI) were obtained for the ophthalmic artery (OA), short posterior ciliary artery (SPCA), and central retinal artery (CRA) and correlated with the subfoveal CT measured by SD-OCT.

RESULTS

Twenty-seven eyes of 27 healthy patients were enrolled (mean age: 40.6 ± 12.4 years; range: 27-68 years). An inverse proportional relationship (P = .0496) was identified between the RI of the SPCA (mean, 0.6117 ± 0.07911) and the subfoveal CT (319.9 µm ± 83.79 µm) but not between the RI and the OA (mean: 0.7019 µm ± 0.07317 µm) or the CRA (mean: 0.68843 µm ± 0.08994 µm).

CONCLUSION

The results of this study suggested there is an inverse proportional relationship between the RI of the SPCA and the subfoveal CT. The data also suggested a correlation between a decrease in the CT and increased RI in the retrobulbar arteries. Therefore, lower choroidal blood flow may explain the thinner CT in normal subjects.

Choroidal Line Scan Measurements in Swept-Source Optical Coherence Tomography as Surrogates for Volumetric Thickness Assessment

PURPOSE

To compare choroidal thickness of different areas on swept-source optical coherence tomography (SSOCT) line and cube scans for their interchangeable use.

DESIGN

Validity analysis.

METHODS

SSOCT line and cube scans were obtained from 21 patients with various choroidal thicknesses. Subfoveal center point choroidal thickness, mean central millimeter choroidal thickness, and mean 6-mm-area choroidal thicknesses were obtained from both eyes by 2 independent graders in a reading center setting. Cross-correlations were performed using Passing and Bablok regression models. A 95% confidence interval of slope that included 1 was considered to indicate no significant difference. Average choroidal thickness of center point, Early Treatment Diabetic Retinopathy Study grid subfields, and total grid area of 6 mm on both scans and the correlation between different areas served as main outcome measures.

RESULTS

No significant difference between line scans/corresponding subfields of cube scans (outer nasal 0.92-1.11, inner nasal 0.88-1.06, central 0.94-1.11, inner temporal 0.95-1.12, outer temporal 0.93-1.17). No significant difference between subfoveal center point measurement/mean of choroidal thickness in the central millimeter of cube scans (0.89-1.08). Significant difference of subfoveal center point measurement or mean of central millimeter area of cube scans to entire 6-mm area of cube scans (1.01-1.53 and 1.03-1.38).

CONCLUSIONS

Measurements on a single SSOCT horizontal line scan can represent the entire choroid but subfoveal center point measurements are only indicative for the central millimeter area. There is a consistent overestimation of choroidal thickness when trying to estimate overall choroidal thickness from any central measurement.

Relationship Between Peripapillary Choroid and Retinal Nerve Fiber Layer Thickness in a Population-Based Sample of Nonglaucomatous Eyes

PURPOSE

To describe the relationship between peripapillary choroidal thickness and retinal nerve fiber layer (RNFL) thickness in a population-based sample of nonglaucomatous eyes.

DESIGN

Population-based, cross-sectional study.

METHODS

A total of 478 nonglaucomatous subjects aged over 40 years were recruited from the Singapore Malay Eye Study (SiMES-2). All participants underwent a detailed ophthalmic examination, including Cirrus and Spectralis optical coherence tomography (OCT) for the measurements of RNFL thickness and peripapillary choroidal thickness, respectively. Associations between peripapillary choroidal thickness and RNFL thickness were assessed using linear regression models with generalized estimating equations.

RESULTS

Of the 424 included subjects (843 nonglaucomatous eyes), 60.9% were women, and the mean (SD) age was 66.74 (10.44) years. The mean peripapillary choroidal thickness was 135.59 ± 56.74 μm and the mean RNFL thickness was 92.92 ± 11.41 μm. In terms of distribution profile, peripapillary choroid was thickest (150.04 ± 59.72 μm) at the superior and thinnest (110.71 ± 51.61 μm) at the inferior quadrant, whereas RNFL was thickest (118.60 ± 19.83 μm) at the inferior and thinnest (67.36 ± 11.36 μm) at the temporal quadrant. We found that thinner peripapillary choroidal thickness (PPCT) was independently associated with thinner RNFL thickness globally (regression coefficient [β] = -1.334 μm for per-SD decrease in PPCT, P = .003), and in the inferior (β = -2.565, P = .001) and superior (β = -2.340, P = .001) quadrants even after adjusting for potential confounders.

CONCLUSIONS

Thinner peripapillary choroid was independently associated with thinner RNFL globally and in the inferior and superior regions. This structure-structure relationship may need further exploration in glaucomatous eyes prior to its application in clinical settings.

En Face Optical Coherence Tomography for Visualization of the Choroid

BACKGROUND AND OBJECTIVE

To assess posterior pole choroid patterns in healthy eyes using en face optical coherence tomography (OCT).

PATIENTS AND METHODS

This observational study included 154 healthy eyes of 77 patients who underwent en face OCT. The mean age of the patients was 31.2 years (standard deviation: 13 years); 40 patients were women, and 37 patients were men. En face imaging of the choroidal vasculature was assessed using an OCT Optovue RTVue (Optovue, Fremont, CA). To generate an appropriate choroid image, the best detectable vessels in Haller's layer below the retinal pigment epithelium surface parallel plane were selected.

RESULTS

Images of diverse choroidal vessel patterns at the posterior pole were observed and recorded with en face OCT. Five different patterns of Haller's layer with different occurrences were assessed. Pattern 1 (temporal herringbone) represented 49.2%, pattern 2 (branched from below) and pattern 3 (laterally diagonal) represented 14.2%, pattern 4 (doubled arcuate) was observed in 11.9%, and pattern 5 (reticular feature) was observed in 10.5% of the reference plane.

CONCLUSION

In vivo assessment of human choroid microvasculature in healthy eyes using en face OCT demonstrated five different patterns. The choroid vasculature pattern may play a role in the origin and development of neuroretinal pathologies, with potential importance in chorioretinal diseases and circulatory abnormalities.

Choroidal thickness and retinal vascular caliber correlations with internal carotid artery Doppler variables

PURPOSE

Decreased retinal arteriolar caliber and increased retinal venular caliber have been associated with increased cardiovascular mortality. This study aimed to evaluate correlations of choroidal thickness and retinal vascular caliber measurements with internal carotid artery (ICA) Doppler ultrasound variables.

METHODS

In this cross-sectional and observational study, 43 eyes and ICAs of 43 healthy volunteers were examined. Spectral domain optical coherence tomography was used to measure subfoveal choroidal thickness (SFCT) and retinal vascular caliber. The ICA Doppler ultrasonographic parameters were diameter, flow volume, peak-systolic velocity, end-diastolic velocity, resistance index (RI), and pulsatility index (PI).

RESULTS

Negative correlations emerged between ICA RI and SFCT (p = 0.017, r = -0.36) as well as between ICA PI and retinal arteriolar caliber (p = 0.015, r = -0.37). A negative linear correlation appeared between ICA diameter and SFCT (p = 0.005, r = -0.42), although ICA diameter and flow volume showed no association with retinal vessel caliber (p > 0.05).

CONCLUSIONS

Choroidal thickness is negatively correlated with ICA diameter and ICA RI, while retinal arteriolar caliber is inversely related with ICA PI in normal volunteers.

Age, Sex, and Ethnic Variations in Inner and Outer Retinal and Choroidal Thickness on Spectral-Domain Optical Coherence Tomography

PURPOSE

To evaluate age, sex, and ethnic variations in inner and outer retinal and choroidal thickness and foveal pit, using spectral-domain optical coherence tomography (SD OCT).

DESIGN

Single-center observational cross-sectional study.

METHODS

Ninety randomly selected, healthy individuals of white, black, and South Asian origin underwent SD OCT raster and enhanced depth imaging scan. Manual measurements of inner and outer retinal thickness and choroidal thickness up to 3 mm nasal and temporal to the fovea were performed. The age, sex, and ethnic differences in these parameters were analyzed.

RESULTS

The mean inner retinal thickness was lower by approximately 12 μm in black subjects across the central retina compared to white subjects (P < .05). The central foveal thickness below the foveal pit was lower in eyes of blacks compared to South Asians (12 μm, P = .035) and white subjects (18 μm, P < .0001). The fovea was also significantly wider in eyes of black and South Asian subjects compared to white individuals. The inner retinal thickness decreased by 0.5 μm per year of age of subjects and was thinner by 6.1 μm (P < .02) in female compared to male subjects. The subfoveal choroidal thickness did not vary between ethnic groups but the temporal choroid was significantly thinner in black subjects (P < .05). The choroid showed an age-related decline in thickness of 2 μm per year of age of the subjects.

CONCLUSIONS

Interethnic differences include wider fovea, lower central foveal thickness, and thinner inner retina in eyes of black subjects compared to their white and South Asian counterparts.

Automated segmentation of the choroid in retinal optical coherence tomography images

The choroid is a tissue layer at the back of the eye, which can be imaged by optical coherence tomography (OCT). Choroidal thickness has been proven to be correlated to several ophthalmic diseases in several studies. In this paper we proposed a novel segmentation technique to address this challenge. This technique firstly automatically segments the inner boundary of the choroid using a two-stage fast active contour model. It secondly allows a real-time human-supervised automated segmentation on the outer boundary of the choroid. Dice similarity coefficient (DSC) was used to evaluate the agreement between manual annotation and our automated measurements on 30 images captured from patients diagnosed with diabetes. The mean DSC value is 92.7% (standard deviation 3.6%) in the range of 85.5% to 98.1%. Results show that this new technique can achieve choroid segmentation with high accuracy.

Optical coherence tomography measurements of choroidal thickness in healthy eyes: correlation with age and axial length

BACKGROUND AND OBJECTIVE

To evaluate subfoveal choroidal thickness (CT) in healthy eyes using spectral-domain optical coherence tomography (SD-OCT) and provide correlations between age and axial length.

PATIENTS AND METHODS

Enhanced depth SD-OCT imaging was performed with Cirrus (Carl Zeiss Meditec, Dublin, CA) and Spectralis (Heidelberg Engineering, Heidelberg, Germany) instruments. CT was measured from the outer limit of the retinal pigment epithelium to the inner surface of the sclera.

RESULTS

The study enrolled 155 patients, with at least 20 in each decade between 22 and 89 years old. Mean axial length was 23.6 mm. Mean Heidelberg subfoveal CT was 286 µm. The correlation between Heidelberg and Zeiss subfoveal CT measurements was strong (r = .978) and significant (P < .001). Mean subfoveal CT was 7.7 µm thinner by Heidelberg versus Cirrus (P < .001). Multiple linear regression analysis revealed that age (P < .001), axial length (P = .001), and sex (P = .025) were significantly related to Heidelberg subfoveal CT.

CONCLUSION

There is a strong negative correlation between CT and age (P <.001), with a 25 µm decrease in CT for each decade of life. Increasing axial length demonstrated a negative correlation with CT, decreasing 24.9 µm for each mm of axial length. Future studies of CT measurements can be performed on either instrument and must account for axial length, age, and sex to make appropriate conclusions.

Anterior and posterior ocular biometry in healthy Chinese subjects: data based on AS-OCT and SS-OCT

Background

To measure the anterior and posterior ocular biometric characteristics concurrently and to determine the relationship between the iris and choroid in healthy Chinese subjects.

Methods

A total of 148 subjects (270 eyes) were enrolled in this cross-section study. The anterior and posterior ocular biometric characteristics were measured simultaneously by anterior segment optical coherence tomography (AS-OCT) and swept-source optical coherence tomography (SS-OCT).

Results

Compared with male eyes, female eyes had narrower anterior biometric parameters that presented with smaller anterior segment parameters [including anterior chamber depth (ACD), width (ACW), area (ACA), and volume (ACV); (all p<0.001)], narrower anterior chamber angle parameters [including angle opening distance (AOD750), trabecular–iris space area (TISA750), and angle recess area (ARA); (all p<0.001)], higher iris curvature (ICURV) (p = 0.003), and larger lens vaults (LV) (p = 0.019). These anterior ocular biometric parameters were correlated with increasing age (p<0.01). Iris thickness (IT750) and iris area (IAREA) were associated with age, ACW, and pupil diameter (all p<0.05), while choroidal thickness (CT) was associated with age, gender, and axial length (all p<0.05). Univariate regression analysis showed that greater CT was significantly associated with smaller IAREA (p = 0.026).

Conclusion

Compared with male eyes, female eyes had narrower anterior biometric parameters that correlated with increasing age, which would be helpful in explaining the higher prevalence of angle closure rates in the female gender and in aging people. Increased CT might be associated with smaller iris area; however, this possibility needs to be investigated in future studies before this conclusion is made.

Diurnal variations in blood flow at optic nerve head and choroid in healthy eyes: diurnal variations in blood flow

To investigate the diurnal variations of the ocular blood flow in healthy eyes using laser speckle flowgraphy (LSFG), and to determine the relationship of the diurnal variations between the ocular blood flow and other ocular parameters.This prospective cross-sectional study was conducted at Nagoya University Hospital. We studied 13 healthy volunteers whose mean age was 33.5 ± 7.6 years. The mean blur rate (MBR), expressing the relative blood flow, on the optic nerve head (ONH) and choroidal blood flow was determined by LSFG (LSFG-NAVI) every 3 hours from 6:00 to 24:00 hours. The intraocular pressure (IOP), choroidal thickness measured by enhanced depth imaging optical coherence tomography, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) in the brachial artery were also recorded. We evaluated the diurnal variations of the parameters and compared the MBR to the other parameters using a linear mixed model.The diurnal variations of the MBR on the ONH varied significantly with a trough at 9:00 hours and a peak at 24:00 hours (P < 0.001, linear mixed model). The MBR of choroid also had significant diurnal variations with a trough at 15:00 hours and a peak at 18:00 hours (P = 0.001). The IOP (P < 0.001), choroidal thickness (P < 0.001), SBP (P = 0.005), DBP (P = 0.001), and HR (P < 0.001) also had significant diurnal variations. Although the diurnal variation of the MBR on the ONH was different from the other parameters, that on the choroid was significantly and positively correlated with the DBP (P = 0.002), mean arterial pressure (P = 0.023), and mean ocular perfusion pressure (P = 0.047).We found significant diurnal variations in the ONH and choroidal blood flow. Although the ONH blood flow had its own diurnal variation because of strong autoregulation, the choroidal blood flow was more likely affected by systemic circulatory factors because of poor autoregulation.

Distribution and determinants of choroidal thickness and volume using automated segmentation software in a population-based study

PURPOSE

To objectively quantify choroidal thickness and choroidal volume using fully automated choroidal segmentation software applied to images obtained from enhanced depth imaging spectral-domain optical coherence tomography (EDI SD OCT) in a population-based study; and evaluate the ocular and systemic determinants of choroidal thickness and choroidal volume.

DESIGN

Prospective cross-sectional study.

METHODS

Participants ranging in age from 45 to 85 years were recruited from the Singapore Malay Eye Study-2 (SiMES-2), a follow-up population-based study. All participants (n = 540) underwent a detailed ophthalmic examination, including EDI SD OCT for measurements of thickness and volume of the choroid.

RESULTS

The intrasession repeatability of choroidal thickness at 5 measured horizontal locations and macular choroidal volume using automated choroidal segmentation software was excellent (intraclass correlation coefficient, 0.97-0.99). Choroid was significantly thicker under the fovea (242.28 ± 97.58 μm), followed by 3 mm temporal (207.65 ± 80.98 μm), and was thinnest at 3 mm nasal (142.44 ± 79.19 μm) location. The mean choroidal volume at central macular region (within a circle of 1 mm diameter) was 0.185 ± 0.69 mm(3). Among the range of ocular and systemic factors studied, age, sex, and axial length were the only significant predictors of choroidal thickness and choroidal volume (all P < .05).

CONCLUSIONS

Using a new automated choroidal segmentation software, we provide fast, reliable, and objective measurements of choroidal thickness and volume in a population-based sample. Male sex, younger age, and shorter axial length are the factors independently associated with thicker choroid and larger choroidal volume. These factors should be taken into consideration when interpreting EDI SD OCT-based choroidal thickness measurements in clinics.

Enhanced depth imaging spectral-domain optical coherence tomography of the choroid in Thai population

OBJECTIVE

To examine subfoveal choroidal thickness (SFCT) in Thai population using enhanced depth imaging spectral- domain optical coherence tomography (EDI-OCT) and to study its correlation with foveal retinal pigment epithelium thickness (FRPE), central neurosensory retinal thickness (CNRT), age, and refraction.

MATERIAL AND METHOD

Four hundred eighty eyes from 240 subjects without glaucoma, retinal, or choroidal diseases underwent scanning of the retina and choroid using EDI-OCT SFCT FRPE, and CNRT measurements were based on the 1:1 micron images and wereperformed by two independent observers. The reliability ofmeasurements between the observers was evaluated by intraclass correlation coefficient (ICC). The correlations of SFCT with FRPE, CNRT, age, and refractive error were analyzed

RESULTS

The mean age of the subjects was 36.22 years (range 20-81years). The means (95% reference intervals) of SFCT, CNRT andFRPE were 294.02 μm (137.14-450.90 μm), 174.22 μm (141.82-206.62 μm), and 41.94 μm (34.65-49.23 μm), respectively. SFCT and CNRThad excellent reliability between the two observers [ICC = 0.947 (95% CI, 0.918-0.963) and 0.929 (95% CI, 0.906-0.945), respectively], while FRPE showed good reliability [ICC = 0. 729 (95% CI, 0.637-0.793)]. SFCT had a low positive correlation with FRPE (r = 0.179, p<0. 0001) but not with CNRT (p = 0.317). SFCT showed a positive correlation with refraction (r = 0.338, p<0.0001) and a negative correlation with age (r = -0.166, p<0.0001). Regression analysis suggested that the SFCT decreased by 12.23 pm per one decade oflife and by 11.42 pm per one diopter of myopia.

CONCLUSION

Normal values of SFCT in Thai population were obtained SFCT significantly decreased with older age and higher myopia. SFCT was associated with FRPE, reflecting the same vascular supply of the choroid and retinal pigment epithelium. When measured with our technique based on the 1:1 micron images, the reliability ofSFCT measurement was very high despite highly morphologic inter-individual variations.

The short-term effects of exercise on intraocular pressure, choroidal thickness and axial length

Purpose

To explore ocular changes in healthy people after exercise.

Methods

Twenty five volunteers underwent exercise for 15 minutes on a treadmill. Measurements of choroidal thickness, intraocular pressure (IOP), ocular biometry, and blood pressure were taken before and after exercise. Enhanced Depth Imaging optical coherence tomography (EDI-OCT) was used to measure choroidal thickness at the fovea. Intraocular pressure (IOP) was measured by Goldmann applanation tonometry. Ocular biometric measures were collected using A scan ultrasound. Blood pressure was measured concurrently with the acquisition of the scans.

Results

Twenty five volunteers (25 eyes) with a mean age of 25.44±3.25 years were measured. There was a significant increase in systolic and diastolic pressure after exercise (P<0.05). The IOP showed a significant decrease after exercise (P<0.05). However there was no significant difference in the mean choroidal thickness, ocular axial length, anterior chamber depth, lens thickness, or vitreous length before and after exercise measurements (P>0.05).

Conclusion

There was a significant decrease in IOP from exercise without a change in choroidal thickness and ocular biometric measures. IOP and choroidal thickness were not correlated, suggesting that the IOP decrease from exercise is not due to changes in choridal thickness.

[Attach importance to choroidal research with enhanced depth imaging spectral-domain optical coherence tomography]

With the enhanced depth imaging spectral-domain optical coherence tomography occurs, choroidal structures and thickness can be observed accurately. So far studies about this technology are focused on the changes of the choroidal thickness and its related factors. While as a non-invasive examination, this technique can also be used to observe structural features of choroidal lesions; measure the diameter of choroidal vessels; study the pathogenesis of disease; differentiate a variety of fundus disease; and follow-up medical or surgical treatment. So it has great scientific value and broad application prospects.

Choroidal analysis in healthy eyes using swept-source optical coherence tomography compared to spectral domain optical coherence tomography

PURPOSE

To compare analyses of choroidal thickness and volume in healthy eyes measured concurrently with prototype long-wavelength swept-source optical coherence tomography (OCT) and commercially available spectral-domain optical coherence tomography (OCT) with and without enhanced depth imaging (EDI).

DESIGN

Prospective cross sectional study.

METHODS

The study included 19 healthy subjects (19 eyes), who were prospectively recruited to undergo 2 consecutive imaging sessions on the same randomly selected eye using spectral domain OCT and a prototype long-wavelength swept-source OCT. On spectral domain OCT, 2 line scans, 1 with and 1 without EDI, and 1 volumetric scan were obtained. On swept-source OCT, 1 line scan and 1 volumetric scan were obtained. Scan patterns on swept-source OCT were created to simulate those available on Cirrus HD-OCT to keep the time of image acquisition constant. Swept-source OCT volumetric scans were motion corrected using a novel registration algorithm. Choroidal thickness and volume were analyzed.

RESULTS

The choroidoscleral interface was clearly visualized in 19/19 (100%) of eyes imaged by swept-source OCT, compared to 14/19 (73.6%) and 13/19 (68.4%) eyes imaged by spectral domain OCT, with and without EDI, respectively. There was no significant difference in choroidal thickness measurements on the line scans obtained on either system (P = 0.10). Choroidal volume could not be assessed on volumetric scans from spectral domain OCT. Mean choroidal volume from swept-source OCT volumetric scans was 11.77 ± 3.13 mm(3) (6.43 mm(3)-17.15 mm(3)).

CONCLUSION

This is the first study that compares simultaneously a prototype long-wavelength swept-source OCT to a commercially available spectral domain OCT for a detailed analysis of choroid in healthy eyes. Swept-source OCT shows potential for better choroidal analysis. Studies using swept-source OCT in diseased eyes will further define this new technology's utility in chorioretinal diseases.

Enhanced visualization of the choroido-scleral interface using swept-source OCT

An accurate analysis of the thickness and volume of choroid using optical coherence tomography (OCT) requires precise visualization of the choroido-scleral interface. Results of studies that use spectral-domain OCT (SD-OCT) to look at the percent visualization of the choroido-scleral interface for accurate analysis of choroidal thickness show varying success rates. This study assessed the visualization of choroido-scleral interface in 19 healthy participants (19 eyes) prospectively recruited for consecutive high-definition raster scanning with an SD-OCT system with and without enhanced depth imaging (EDI) and a prototype long-wavelength swept-source OCT (SS-OCT) system. Choroido-scleral interface was visualized in all eyes imaged on SS-OCT, compared with 13 of 19 (68.4%) and 14 of 19 (73.6%) eyes imaged on SD-OCT without EDI (P = .009) and with EDI (P = .02), respectively. The prototype long-wavelength SS-OCT system, with its higher acquisition speed and deeper tissue penetration, may have better clinical utility in determining the involvement of choroid in various chorioretinal diseases.

Effect of candesartan on the expression of sclera-choroidal intercellular adhesion molecule-1 in hypercholesterolemic models

OBJECTIVE

To evaluate the effect of blocking the angiotensin II AT-1 receptor by the systemic administration of candesartan on the expression of intercellular adhesion molecule-1 in the sclera and choroid of hypercholesterolemic rabbits.

METHODS

New Zealand rabbits were divided into 3 groups, as follows: GI, which was fed a rabbit standard diet; GII, which was fed a hypercholesterolemic diet; and GIII, which received hypercholesterolemic diet plus candesartan. Samples of the rabbits' sclera and choroid were then studied by hematoxylin-eosin staining and histomorphometric and immunohistochemical analyses for intercellular adhesion molecule-1 expression.

RESULTS

Histological analysis of hematoxylin- and eosin-stained sclera and choroid revealed that macrophages were rarely present in GI, and GII had significantly increased macrophage numbers compared to GIII. Moreover, in GII, the sclera and choroid morphometry showed a significant increase in thickness in comparison to GI and GIII. GIII presented a significant increase in thickness in relation to GI. Sclera and choroid immunohistochemical analysis for intercellular adhesion molecule-1 expression revealed a significant increase in immunoreactivity in GII in relation to GI and GIII. GIII showed a significant increase in immunoreactivity in relation to GI.

CONCLUSION

Candesartan reduced the expression of intercellular adhesion molecule-1 and consequently macrophage accumulation in the sclera and choroid of hypercholesterolemic rabbits.

Correlation of choroidal thickness with outer and inner retinal layers

BACKGROUND AND OBJECTIVE

To investigate the correlation of choroidal thickness with the outer and inner retinal layers.

PATIENTS AND METHODS

A retrospective OCT scan review was conducted for healthy patients. Choroidal, outer retinal layer, and inner retinal layer thicknesses were measured at the fovea and 500 μm, 1,000 μm, and 1,500 μm temporal and nasal to the fovea. Retinal thickness was also measured at the foveal center. Choroidal thickness (CT) was compared at different locations, and correlation of CT with the outer and inner retinal layers was examined.

RESULTS

Mean CT was thinnest nasally, thicker in the subfoveal region, and then thinner again temporally. Correlations found between CT and outer retinal layer thicknesses at temporal points to the fovea were slightly higher than correlations between CT and inner layer thicknesses.

CONCLUSION

The correlation between choroidal thickness and the outer retinal layer was very weak. Similar prospective trials are needed to assess the correlation of CT with retinal layers.

Automated segmentation and characterization of choroidal vessels in high-penetration optical coherence tomography

An automated choroidal vessel segmentation and quantification method for high-penetration optical coherence tomography (OCT) was developed for advanced visualization and evaluation of the choroidal vasculature. This method uses scattering OCT volumes for the segmentation of choroidal vessels by using a multi-scale adaptive threshold. The segmented choroidal vessels are then processed by multi-scale morphological analysis to quantify the vessel diameters. The three-dimensional structure and the diameter distribution of the choroidal vasculature were then obtained. The usefulness of the method was then evaluated by analyzing the OCT volumes of normal subjects.

Measurement of choroidal perfusion and thickness following systemic sildenafil (Viagra(®) )

PURPOSE

To demonstrate anatomic and physiologic changes in the human choroid following systemic sildenafil citrate (Viagra®) using enhanced depth imaging spectral domain-optical coherence tomography (EDI-OCT) and swept-scan high-frequency digital ultrasound.

METHODS

Seven healthy male subjects (mean age 32.7 years) were evaluated at baseline and 2 hr after ingesting 50 mg of sildenafil. Swept-scan high-frequency digital ultrasound and EDI-OCT were utilized to measure choroidal perfusion and thickness, respectively. Results were read by masked observers. The Wilcoxon signed-rank test and t-test were used to analyse differences in choroidal flow and thickness at baseline and 2 hr after ingestion of sildenafil.

RESULTS

Two hours following sildenafil, increased choroidal perfusion was observed in 11 of 12 eyes measured by swept-scan high-frequency digital ultrasound. The mean increase was 3.46 (±2.00) times baseline with a range of 0.47-7.80 times baseline (p = 0.004). Increased choroidal thickness was observed in 12 of 12 eyes measured with EDI-OCT. The average choroidal thickness increased by 11.6% temporal to the fovea, 9.3% nasal to the fovea and 10.7% underneath the fovea (p < 0.001 for all values).

CONCLUSIONS

Choroidal perfusion and thickness both increase in response to systemic sildenafil. These changes could secondarily affect retinal function, explain previously reported clinical symptoms and potentially be a useful adjunct for treatment of ocular diseases that would benefit from increased choroidal blood flow.

[Peripapillary choroidal thickness in primary open angle glaucoma and normal subjects measured by enhanced depth imaging optical coherence tomography]

OBJECTIVE

To compare peripapillary choroidal thickness (CT) between primary open angle glaucoma (POAG) and normal subjects using enhanced depth imaging optical coherence tomography (EDI-OCT).

METHODS

This research was a cross-sectional study. A 360-degree 3.4 mm diameter peripapillary circle scan was performed for retinal nerve fiber layer (RNFL) assessment by EDI-OCT in one eye of 40 POAG patients and 41 age- and sex-matched normal subjects. The observer used the manual segmentation function to delineate the posterior edge of the retinal pigment epithelium and the sclerochoroidal interface. The RNFL thickness algorithm function was used to automatically generate the CT in corresponding sectors. The intra- and inter-observer reproducibility was evaluated by intraclass correlation coefficient (ICC). Repeated measures ANOVA and LSD-t test were used to analyze differences in CT by peripapillary location. A Pearson correlation was calculated for variation in CT relative to age and RNFL. Spearman rank correlation was calculated to test the strength of the relationship between global mean RNFL and visual field mean deviation (MD) and between CT and MD. Independent-samples t-test was conducted to compare mean RNFL and CT between POAG and normal subjects.

RESULTS

The intra- and interobserver ICC values ranged from 0.993 to 0.999 and 0.993 to 0.998 respectively. In both groups, the CT showed a negative correlation with age at each peripapillary location (r = -0.509 to -0.608, -0.549 to -0.668; P = 0.000 to 0.001) but no significant correlation with RNFL for any location (r = -0.186 to 0.273, -0.090 to 0.132; P = 0.092 to 0.869). The peripapillary CT was thickest superotemporally and superonasal, then nasally and temporally, and was thinnest inferotemporally and inferonasal (P = 0.000 to 0.036). Compared to normal subjects, eyes with POAG had significantly thinner RNFL at all locations (t = 6.975 to 16.087, P = 0.000), but CT measurements did not differ between groups for any location (t = -0.474 to 0.367, P = 0.637 to 0.978). In POAG patients, the global mean RNFL (rs = -0.511, P = 0.001) but not CT (rs = -0.285, P = 0.079) was found to significantly correlate with visual field MD.

CONCLUSIONS

The peripapillary CT in POAG neither differ from that in normal subjects nor correlate with RNFL and visual field index, which does not support using it as a clinical parameter in glaucoma diagnosis or management.

Retinal polarization-sensitive optical coherence tomography at 1060 nm with 350 kHz A-scan rate using an Fourier domain mode locked laser

We present a novel, high-speed, polarization-sensitive, optical coherence tomography set-up for retinal imaging operating at a central wavelength of 1060 nm which was tested for in vivo imaging in healthy human volunteers. We use the system in combination with a Fourier domain mode locked laser with active spectral shaping which enables the use of forward and backward sweep in order to double the imaging speed without a buffering stage. With this approach and with a custom designed data acquisition system, we show polarization-sensitive imaging with an A-scan rate of 350 kHz. The acquired three-dimensional data sets of healthy human volunteers show different polarization characteristics in the eye, such as depolarization in the retinal pigment epithelium and birefringence in retinal nerve fiber layer and sclera. The increased speed allows imaging of large volumes with reduced motion artifacts. Moreover, averaging several two-dimensional frames allows the generation of high-definition B-scans without the use of an eye-tracking system. The increased penetration depth of the system, which is caused by the longer probing beam wavelength, is beneficial for imaging choroidal and scleral structures and allows automated segmentation of these layers based on their polarization characteristics.

[Relationship between gender and posterior pole choroidal thickness in normal eyes]

OBJECTIVE

To investigate and compare the choroidal thickness between healthy male and female subjects.

METHOD

Six-hundred and twenty eyes of 310 healthy volunteers with no ophthalmic disease history were recruited, including 152 males and 158 females. All volunteers were subgrouped into Group A to F according to their ages. Enhanced depth imaging choroidal scans were obtained in all eyes by using spectral-domain optical coherence tomography. Subfoveal choroidal thickness (SFCT) and choroidal thickness at 1 mm/3 mm superior, inferior, nasal and temporal to the fovea were measured. Choroidal thickness was compared between male and female in the subgroups with different age.

RESULTS

Mean SFCT was higher in 152 males (298.02 ± 101.47) µm than that in 158 females (256.28 ± 90.87) µm with statistically significant difference (t' = 4.853, P < 0.05). Choroid at 1 mm and 3 mm from the fovea were also thicker in the male (t' = 5.050, t = 4.597, t = 5.225, t = 5.363, t = 5.608, t' = 4.239, t = 4.108, t' = 5.589; P < 0.05). In any subgroup from A to E, SFCT in male was significantly thicker than female, after adjusted for refractive error (t = 2.343, t' = 2.163, t = 3.239, t = 2.181, t' = 2.982; P < 0.05). In Group F, mean SFCT in male was thicker than female, but without statistical significance (t' = 0.681, P > 0.05).

CONCLUSIONS

Gender was one of the factors that affect the choroid thickness in healthy populations. In subjects under 70, male have thicker choroid than female. This result at least partially explained the gender predilection of macular diseases, such as central serous chorioretinopathy and idiopathic macular hole.

Bio-heat transfer simulation of retinal laser irradiation

Retinopathy is a surgical process in which maladies of the human eye are treated by laser irradiation. A two-dimensional numerical model of the human eye geometry has been developed to investigate transient thermal effects due to laser radiation. In particular, the influence of choroidal pigmentation and that of choroidal blood convection-parameterized as a function of choroidal blood perfusion-are investigated in detail. The Pennes bio-heat transfer equation is invoked as the governing equation, and finite volume formulation is employed in the numerical method. For a 500-μm diameter spot size, laser power of 0.2 W, and 100% absorption of laser radiation in the retinal pigmented epithelium (RPE) region, the peak RPE temperature is observed to be 103 °C at 100 ms of the transient simulation of the laser surgical period. Because of the participation of pigmented layer of choroid in laser absorption, peak temperature is reduced to 94 °C after 100 ms of the laser surgery period. The effect of choroidal blood perfusion on retinal cooling is found to be negligible during transient simulation of retinopathy. A truncated three-dimensional model incorporating multiple laser irradiation of spots is also developed to observe the spatial effect of choroidal blood perfusion and choroidal pigmentation. For a circular array of seven uniformly distributed spots of identical diameter and laser power of 0.2 W, transient temperature evolution using simultaneous and sequential mode of laser surgical process is presented with analysis.

Automated segmentation of intramacular layers in Fourier domain optical coherence tomography structural images from normal subjects

Segmentation of optical coherence tomography (OCT) cross-sectional structural images is important for assisting ophthalmologists in clinical decision making in terms of both diagnosis and treatment. We present an automatic approach for segmenting intramacular layers in Fourier domain optical coherence tomography (FD-OCT) images using a searching strategy based on locally weighted gradient extrema, coupled with an error-removing technique based on statistical error estimation. A two-step denoising preprocess in different directions is also employed to suppress random speckle noise while preserving the layer boundary as intact as possible. The algorithms are tested on the FD-OCT volume images obtained from four normal subjects, which successfully identify the boundaries of seven physiological layers, consistent with the results based on manual determination of macular OCT images.