Automated macular choroidal thickness measurement by swept-source optical coherence tomography in pseudoxanthoma elasticum

Evaluation of an Automated Choroid Segmentation Algorithm in a Longitudinal Kidney Donor and Recipient Cohort

Purpose

To evaluate the performance of an automated choroid segmentation algorithm in optical coherence tomography (OCT) data using a longitudinal kidney donor and recipient cohort.

Methods

We assessed 22 donors and 23 patients requiring renal transplantation over up to 1 year posttransplant. We measured choroidal thickness (CT) and area and compared our automated CT measurements to manual ones at the same locations. We estimated associations between choroidal measurements and markers of renal function (estimated glomerular filtration rate [eGFR], serum creatinine, and urea) using correlation and linear mixed-effects (LME) modeling.

Results

There was good agreement between manual and automated CT. Automated measures were more precise because of smaller measurement error over time. External adjudication of major discrepancies was in favor of automated measures. Significant differences were observed in the choroid pre- and posttransplant in both cohorts, and LME modeling revealed significant linear associations observed between choroidal measures and renal function in recipients. Significant associations were mostly stronger with automated CT (eGFR, P < 0.001; creatinine, P = 0.004; urea, P = 0.04) compared to manual CT (eGFR, P = 0.002; creatinine, P = 0.01; urea, P = 0.03).

Conclusions

Our automated approach has greater precision than human-performed manual measurements, which may explain stronger associations with renal function compared to manual measurements. To improve detection of meaningful associations with clinical endpoints in longitudinal studies of OCT, reducing measurement error should be a priority, and automated measurements help achieve this.

Translational Relevance

We introduce a novel choroid segmentation algorithm that can replace manual grading for studying the choroid in renal disease and other clinical conditions.

Progression of pachychoroid neovasculopathy into aneurysmal type 1 choroidal neovascularization or polypoidal choroidal vasculopathy

PURPOSE

To describe the progression of pachychoroid neovasculopathy (PNV) into pachychoroid aneurysmal type 1 choroidal neovascularization (PAT1) / polypoidal choroidal vasculopathy (PCV).

DESIGN

Retrospective longitudinal cohort study.

SUBJECTS

Patients diagnosed with PNV with a follow-up of ≥ 2 years.

METHODS

Multimodal imaging, including optical coherence tomography and fluorescein and indocyanine green angiography, was reviewed for the presence of choroidal neovascularization (CNV), aneurysms within/at the margins of the CNV and sub-foveal choroidal thickness (SFCT).

MAIN OUTCOME MEASURES

Rate of PNV to PAT1/PCV conversion and risk factors thereof.

RESULTS

In total, 37 PNV eyes of 32 patients with a mean follow-up of 3.3±1.1 (2.0 - 5.2) years were included in the study. At PNV diagnosis, mean age was 59.7±8.7 (range: 38.5 - 78.0) years and mean SFCT was 357±92 (185 - 589) μm. During follow-up, 5 eyes (13.5 %) developed aneurysms after a mean 3.4±0.8 years (2.3 - 4.2 years) years, defining PAT1/PCV. Risk of PAT1/PCV conversion was 7.4 % at year 3, 13.6 % at year 4 and 30.7 % at year 5. Mean 5.2±4.0 to 8.1±3.4 intravitreal anti-VEGF injections were given per year, resulting in a significant reduction of SFCT to 317±104 (122 to 589) μm (p= 0.0007). Age at diagnosis of PNV was significantly lower in eyes that later went on to develop PAT1/PCV (54.0±5.6 (45.9 to 60.5) vs. 61.2±8.4 (38.5 - 78.0) years, p=0.025). At end of follow-up, SFCT had on average decreased by -14.0±17.6 (-55.9 to 23.1) % in the PNV group, while it had increased by mean 6.9±4.4 (0.00 to 10.8) % in the PAT1/PCV conversion group (p=0.0025).

CONCLUSION

PNV can develop aneurysms within its type 1 CNV, defining conversion to PAT1/PCV. In this study, conversion to PAT1/PCV was seen in 13.5 % of eyes, resulting in Kaplan Meier estimates of risk for conversion of 7.4 % at year 3, 13.6 % at year 4 and 30.7 % at year 5. Younger age at diagnosis of PNV and sustained choroidal thickening despite anti-VEGF therapy might be risk factors for PNV to progress into PAT1/PCV.

Is arterial stiffness in the carotid artery associated with choroidal thinning in patients with pseudoxanthoma elasticum or controls?

PURPOSE

Patients with pseudoxanthoma elasticum (PXE) develop calcification of Bruch's membrane (BM) and choroidal thinning, as well as calcification of intracranial arteries, leading to arterial stiffness. We investigated whether arterial stiffness is associated with choroidal thinning in PXE patients, besides the presumed effect of BM calcification.

METHODS

Cross-sectional study with 75 PXE patients and 40 controls. Macular choroidal thickness was measured using optical coherence tomography scans. Functional magnetic resonance imaging was used to calculate the pulsatility index (PI) of the carotid siphon as a measure of arterial stiffness. Associations between PI and choroidal thickness were investigated using linear mixed effects models adjusted for age and ocular axial length. Furthermore, we investigated choroidal thickness in relation to the presence of retinal pigment epithelium (RPE) atrophy, its topographical distribution and age.

RESULTS

Median age was 58 years (IQR 53-66) in PXE patients and 62 years (IQR 56-67) in controls (p = 0.08). Pseudoxanthoma elasticum (PXE) patients had a thinner choroid than controls (138 μm versus 248 μm, p < 0.01). No association was observed between PI and choroidal thickness in PXE patients (β = -1.6, 95% CI -59.4 to 54.5) nor in controls (β =-47.6, 95% CI -129.7 to 31.9). In PXE patients, RPE atrophy was associated with a thinner choroid (p < 0.01). Also, the nasal choroid was thinner than the temporal choroid, and choroidal thickness already decreased with age in PXE eyes without RPE atrophy.

CONCLUSION

There was no independent association between measures of arterial stiffness and choroidal thinning in PXE patients and controls. Probably, changes in BM lead to choroidal thinning in PXE.

A Reflectivity Measure to Quantify Bruch's Membrane Calcification in Patients with Pseudoxanthoma Elasticum Using Optical Coherence Tomography

Purpose

Progressive calcification of Bruch's membrane (BM) causes considerable visual morbidity in patients with pseudoxanthoma elasticum (PXE). Since calcification is hyperreflective on optical coherence tomography (OCT), our aim was to measure BM calcification with OCT imaging.

Methods

Case-control study with 45 patients with PXE under 40 years (range, 11-39) and 25 controls (range, 14-39). Spectralis HRA-OCT imaging consisted of seven macular B-scans with 250-µm spacing. Retinal segmentation was performed with the IOWA Reference Algorithms. MATLAB was used to extract and average z-axis reflectivity profiles. Layer reflectivities were normalized to the ganglion cell and inner plexiform layers. Both median and peak layer reflectivities were compared between patients with PXE and controls. The discriminative value of the retinal pigment epithelium (RPE)-BM peak reflectivity was analyzed using receiver operating characteristic analysis.

Results

The reflectivity profile of patients with PXE differed from controls in the outer retinal layers. The normalized median RPE-BM reflectivity was 41.1 (interquartile range [IQR], 26.3-51.9) in patients with PXE, compared with 22.5 (IQR, 19.3-29.5) in controls (P = 2.09 × 10^-3). The normalized RPE-BM peak reflectivity was higher in patients with PXE (67.5; IQR, 42.1-84.2) than in controls (32.7; IQR, 25.7-38.9; P = 2.43 × 10^-5) and had a high discriminative value with an area under the curve of 0.85 (95% confidence interval, 0.76-0.95). In patients with PXE under 40 years, increasing age did not have a statistically significant effect on the RPE-BM peak reflectivity (patients under 20 years: 44.2 [IQR, 40.5-74.6]; 20-30 years: 66.0 [IQR, 45.1-83.8]; 30-40 years: 70.8 [IQR, 49.0-88.0], P = 0.47).

Conclusions

BM calcification can be measured as increased RPE-BM reflectivity in young patients with PXE and has a high discriminative value.

Translational Relevance

In patients with PXE, the OCT reflectivity of Bruch's membrane may be the first biomarker for Bruch's membrane calcification and a valuable ophthalmologic endpoint in clinical trials.

Qualitative comparison of choroidal vascularity measurement algorithms

Purpose:

To compare the accuracy of manual and automated binarization technique for the analysis of choroidal vasculature.

Methods:

This retrospective study was performed on a total of 98 eyes of 60 healthy subjects. Fovea-centered swept source optical coherence tomography (SS-OCT) scans were obtained and choroidal area was binarized using manual and automated image binarization technique separately. Choroidal vessel visualization in the binarized scans were subjectively graded (grades 0–100) by comparing them with the original OCT scan images by two masked graders. The subjective variability and repeatability was compared between two binarization method groups. Intergrader and intragrader variability was estimated using paired t-test. The degree of agreement between the grades for each observer and between the observers was evaluated using Bland–Altman plot.

Results:

The mean accuracy grades of the automatically binarized images were significantly (P < 0.001) higher (93.38% ± 1.70%) than that of manually binarized images (78.06% ± 2.92%). There was a statistically significant variability and poor agreement between the mean interobserver grades in the manual binarization arm.

Conclusion:

Automated image binarization technique is faster and appears to be more accurate in comparison to the manual method.

Reticular Pseudodrusen and Thin Choroid Are Associated With Angioid Streaks

BACKGROUND AND OBJECTIVE

To report the association of angioid streaks in patients with Pseudoxanthoma elasticum (PXE) with reticular pseudodrusen (RPD), thin choroid, and retinal pigment epithelium (RPE) atrophy using swept-source optical coherence tomography (SS-OCT) and short-wave autofluorescence (SWAF).

PATIENTS AND METHODS

Retrospective cross-sectional study. Records of consecutive patients with angioid streaks due to PXE, who presented with a decrease of vision due to choroidal neovascularization (CNV), were reviewed for best-corrected visual acuity, color fundus photographs, SS-OCT, SWAF, and red-free images with special emphasis on presence or absence of RPD, subfoveal choroidal thickness (SFCT), and RPE atrophy.

RESULTS

Sixteen eyes of eight patients with a mean age of 45.5 years ± 9.4 years were enrolled in the study. RPD were seen in 10 of the 16 eyes and were seen commonly along the superotemporal quadrant. Mean subfoveal thickness in study eyes (175.7 μm ± 37.2 μm) was significantly reduced when compared to controls (286.4 μm ± 40.8 μm). The mean SFCT was similar between the eyes with and without CNV. Four eyes had RPE atrophy in the macular area, whereas four eyes had peripapillary RPE atrophy.

CONCLUSIONS

Angioid streaks in PXE are associated with RPD, thin choroid, and RPE atrophy. These features occur at a younger age as compared to age-related macular degeneration and appear to be interrelated because of single pathophysiological mechanism. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:402-408.].

Sex-Dependent Choroidal Thickness Differences in Healthy Adults: A Study Based on Original and Synthesized Data

PURPOSE

The purpose of this study is to determine the influence of sex on choroidal thickness (CT) in healthy adults.

METHODS

Healthy Chinese adults were recruited and complete ophthalmic examinations were performed. The choroid was imaged by swept-source optical coherence tomography and the macular CT in Early Treatment Diabetic Retinopathy Study grids was obtained by the intrinsic automated segmentation software. CT in males and females was compared after controlling other factors. All of the published studies in PubMed were systemically tracked, and a syntheses analysis of the combined data of the present study and previous studies was performed to address this issue further.

RESULTS

A total of 104 healthy adults were included, of whom 38 (37%) were male and 66 (63%) were female. Older age and longer axial length (AL) each were significantly associated with thinner CT. After controlling for age and AL, the foveal CT and average macular CT were 25.5 μm (95% CI: 0.5-50.4 μm) and 22.1 μm (95% CI: 2.7-41.4 μm) thicker in men than in women, respectively. Significant differences in CT between males and females were also observed in inner and outer rings after controlling for age and AL (P < 0.05). After strict screening, 15 previously reported studies were determined to be eligible for inclusion. The combination of data collected from 2821 males and 3389 females provided further evidence that the choroid is thicker in males, with a pooled mean difference of 19.5 μm (95% CI: 11.4 to 27.6) for foveal CT and 14.7 μm (95% CI: 6.8 to 22.6) for average CT.

CONCLUSION

Our study of Chinese subjects, along with the syntheses analysis, strengthens the evidence that CT is greater in males than in females, based on OCT measurements. This observation may be pertinent for the sex disparities in some clinical conditions related to CT.