Optical Coherence Tomography Angiography in Foveal Hypoplasia

Characterizing Foveal Hypoplasia Using Optical Coherence Tomography Angiography: Evaluation of Microvascular Abnormalities and Clinical Significance

This study aimed to evaluate foveal avascular zone (FAZ) features and macular flow density (FD) in various retinal layers in a cohort of patients with foveal hypoplasia (FH) using optical coherence tomography angiography (OCTA), in order to characterize microvascular abnormalities and explore their potential clinical significance. FAZ parameters and FD, as well as retinal thickness and volume values were analyzed and compared between patients with FH and an age- and gender-matched control cohort. Correlations between disease severity and visual acuity (VA), as well as between disease severity and FAZ features were evaluated. A total of 19 eyes with FH and 19 control eyes were included. The study group showed significantly higher FD values in the foveal sectors of the superficial and deep capillary plexus compared to controls. FAZ area, perimeter, and acircularity index (ACI) were noticeably altered in eyes with FH; however, they did not correlate with disease severity. Visual acuity was negatively correlated with disease severity. The results of this study provide evidence of altered microvasculature architecture specifically in the foveal sectors of patients with FH. The higher FD values in the foveal sectors of FH patients suggest a potential compensatory response of the retinal microvasculature. FAZ parameters and FD values of the foveal sectors could be used as part of an OCTA-based grading system in FH patients.

Clinical spectrum of blunted foveal contour

Foveal hypoplasia is the absence of a foveal depression and the presence of the ganglion cell layer in the foveola. A spectrum of clinical characteristics, including normal or variably decreased visual acuity, has been described in patients with blunted foveal contours. Multiple systemic and ophthalmologic conditions including albinism, aniridia, nanophthalmos, prematurity, and fovea plana have been associated with this anomaly. This article illustrates select clinical conditions characterized by a blunted foveal contour. Given the heterogeneity of findings, a thorough medical history and detailed physical and ocular examinations are usually sufficient for the clinician to make the correct diagnosis.

[Area of the foveal avascular zone in patients with refractive errors]

PURPOSE

To investigate the dependence of the area of the foveal avascular zone (FAZ) on axial eye length (AL) and to develop a feasible method for correcting this dependence.

MATERIAL AND METHODS

The study involved 209 patients over the age of 18 years (209 eyes), of them 52 patients with AL of 20-22 mm (hyperopia group), 60 patients with AL of 25.5-28.5 mm (myopia group) and 97 patients with AL of 22.5-24.5 mm (emmetropia group). Optical coherence tomography angiography (OCTA) examination was performed on Cirrus HD-OCT 5000 with AngioPlex («Carl Zeiss Meditec», Germany).

RESULTS

FAZ area was corrected using the Littmann-Bennett formula modified by A.A. Shpak and M.V. Korobkova. FAZ area values both in emmetropic patients and in patients with refractive errors varied over a very wide range. Before correction, AL had a significant influence on the FAZ area (mm²), which compared to the emmetropia group (0.27±0.09) was significantly reduced in the myopia group (0.21±0.07; p<0.000) and increased in the hyperopia group (0.31±0.11; p=0.015). The corrected FAZ area values did not differ in the compared groups. After correction the FAZ area decreased on average by 19% in the hyperopia group and increased by 25% in the myopia group. A chart and an Excel (Microsoft)/LibreOffice Calc program have been developed for correction of the FAZ area depending on the AL.

CONCLUSION

Refractive errors, especially high-degree ones, have a significant effect on the FAZ area. This study proposes an original chart and a calculation program for correct interpretation of FAZ area measurements in patients with refractive errors, providing an accessible and quick way to assess the obtained results.

Multimodal Imaging of Isolated Foveal Hypoplasia: A Case Report

Fovea hipoplazisi, normal foveanın gelişmemesi ile karakterizedir. İzole veya başka oküler durumlarda sekonder olarak gelişebilmektedir. Optik koherens tomografi (OKT), floresein anjiyografi, fundus otofloresans ve OKT anjiyografi tanıda kullanılabilir. Bu olgu sunumunda multimodal görüntüleme ile tanı konulan, foveal hipoplazili bir hastayı sunmaktayız.

Clinicopathologic correlation of aniridia: Optical coherence tomography angiography and histopathologic observations

Purpose

To describe optical coherence tomography angiography (OCTA) findings in a patient with aniridia and correlate with representative histopathology.

Observations

OCTA images of the macula of a pediatric aniridic patient, who has nystagmus and impaired vision bilaterally, demonstrate a complete absence of the foveal avascular zone (FAZ) in both the superficial and deep vascular complexes (SVC and DVC). In addition, larger superficial blood vessels were found to be abnormally diving from the SVC into the DVC. Similarly, immunofluorescence with confocal microscopy imaging of a retinal histopathology specimen from a 2 month old aniridic patient demonstrated larger vessels diving in the same manner.

Conclusions and importance

This study highlights the clinical, imaging and histopathologic findings of aniridia. Supine OCTA imaging, performed during examination under anesthesia, allowed for visualization of retinal microvasculature in eyes with nystagmus. The histopathology images helped validate OCTA findings that, with further investigation, may lead to new information about the development of abnormal retinal microvasculature.

Case Report: Optical Coherence Tomography Angiography of Idiopathic Foveal Hypoplasia and Its Correlation With Visual Acuity

SIGNIFICANCE

Foveal hypoplasia is described clinically by the absence of a foveal pit and subsequent reduction in visual acuity. Optical coherence tomography angiography provides precise segmentation of the retinal vascular supply demonstrating the vascular perfusion in affected patients. Preservation of perfusion is linked to visual acuity and function.

PURPOSE

This case report describes a patient with foveal hypoplasia and preservation of visual acuity with preserved retinal capillary density of the superficial and deep capillary plexuses on optical coherence tomography angiography. In addition, the diagnostic findings of foveal hypoplasia as seen on optical coherence tomography angiography will be described.

CASE REPORT

A 25-year-old Caucasian female with history of foveal hypoplasia presented to the clinic for evaluation. She had no other visual, ocular, or systemic complaints. Her ocular history included Duane syndrome, accommodative insufficiency, and traumatic brain injury. Her medical history included cardiac ablation secondary to supraventricular tachycardia, gall bladder removal, maxillary sinus cyst, and a history of migraines. Best-corrected visual acuity was 20/15 in the right and left eyes. Funduscopic examination was unremarkable. Spectral domain optical coherence tomography revealed absence of the anatomical foveal pit with normal inner retinal morphology. Optical coherence tomography angiography confirmed a decreased foveal avascular zone; however, a vascular density analysis showed normal perfusion to the inner retinal plexuses.

CONCLUSIONS

Optical coherence tomography angiography is a rapid, noninvasive imaging modality that provides excellent insight into the microvasculature supply to the retina and choroid. As such, it allows for an in-depth analysis into the pathophysiology behind certain conditions such as foveal hypoplasia.

Foveal abnormalities determined by optical coherence tomography angiography in children with history of retinopathy of prematurity

PURPOSE

To describe the foveal characteristics of children with a history of retinopathy of prematurity (ROP) using optical coherence tomography angiography (OCTA).

METHODS

All eyes were examined by OCTA (RTVue AVANTI, Optovue Inc, Fremont, CA) with a scan of 3 × 3 mm cantered on the fovea. The size of the foveal avascular zone (FAZ), central retinal thickness (CRT), and foveal bulge were measured.

RESULTS

Forty-eight eyes of 26 children with a history of ROP and a mean age of 8.8 years with a range of 4-16 years (ROP group) were studied. Sixty-six eyes of 36 children without any fundus abnormalities and with an average age of 10.5 years and a range of 3-17 years (control group) were studied as controls. The mean FAZ area in the ROP group was 0.18 mm² which was significantly smaller than the 0.32 mm² in the control group (p < 0.01). The mean CRT was significantly thicker in the ROP group (228 µm) compared to the control group (189 µm; p < 0.01). The size of FAZ was not measurable in 5 eyes (10.4%) of 3 children in the ROP group. The correlation between the FAZ area and CRT was significant in both the ROP and control groups (r = -0.53 in ROP; r = -0.57 in control; both p < 0.01). There was no significant difference in the height of the foveal bulge between two groups (p = 0.64).

CONCLUSIONS

The FAZ is smaller in ex-preterm children with a history of ROP (including laser treatment for ROP) than in children who were not premature.

Multimodal imaging in a patient with Prader-Willi syndrome

Background

Prader-Willi syndrome (PWS) is a genetic disease caused by loss of expression of the paternally inherited copy of several genes on the long arm of chromosome 15. Ophthalmic manifestations of PWS include strabismus, amblyopia, nystagmus, hypopigmentation of the iris and choroid, diabetic retinopathy, cataract and congenital ectropion uvea. An overlap between PWS and oculocutaneous albinism (OCA) has long been recognized and attributed to deletion of OCA2 gene located in PWS critical region (PWCR).

Case report

A 30-year-old male patient with PWS presented with vision loss in his left eye. His right eye had normal visual acuity. Multimodal imaging revealed absence of a foveal depression and extremely reduced diameter of the foveal avascular zone in the right eye and an inactive type 2 macular neovascular lesion in the left eye.

Conclusions

We report a presumed association of fovea plana and choroidal neovascularization with PWS. The use of multimodal imaging revealed novel findings in a PWS patient that might enrich our current understanding of the overlap between PWS and OCA.

Foveal avascular zone area measurements with optical coherence tomography angiography in patients with nanophthalmos

PURPOSE

To compare the area of the superficial foveal avascular zone (SFAZ) and deep foveal avascular zone (DFAZ) between patients with nanophthalmos and age matched controls.

METHODS

This prospective and comparative study included 19 eyes from 11 patients with nanophthalmos (study group) and 19 eyes from 19 healthy subjects (control group). SFAZ and DFAZ were measured with optical coherence tomography angiography (OCT-A). All participants underwent a standardised ocular examination including best corrected visual acuity (BCVA), central macular thickness (CMT), subfoveal choroidal thickness (SFCT) anterior chamber depth (ACD), axial length (AL), and refractive error (RE) measurements.

RESULTS

Mean SFAZ and DFAZ area in the nanophthalmic eyes and in the control eyes were 0.09 ± 0.12 mm², 0.10 ± 0.10 mm² and 0.37 ± 0.10 mm², 0.37 ± 0.10 mm² respectively (p < 0.001 and p < 0.001). Mean BCVA, RE, AL, ACD CMT, SFCT, were 0.40 ± 0.34 logMAR Unit, 10.0 ± 2.2 18.1 ± 1.5 mm, 2.15 ± 0.28 mm, 367.1 ± 87.4 µm, 489.2 ± 85.2 µm respectively, in nanophthalmic eyes and there was a statistically significant difference between groups (p < 0.001 for each). There were negative correlations for both SFAZ and DFAZ with RE (r = -0.733 and r = -0.758, p < 0.001), CMT (r = -0.823 and r = -0.82, p < 0.001), SFCT (r = -0.647 and r = -0.717 p < 0.001) for the entire study population. SFAZ and DFAZ area were significantly correlated with AL (r = 0.732 and r = 0.745, p < 0.001) and ACD (r = 0.614 and r = 0.654, p < 0.001). In study group, 5 eyes did not have neither SFAZ nor DFAZ, 3 eyes had only DFAZ and 1 eye had only SFAZ in the OCT-A images.

CONCLUSIONS

SFAZ and DFAZ area were significantly smaller in nanophthalmic eyes than control eyes.

Unmeasurable small size of foveal avascular zone without visual impairment in optical coherence tomography angiography

PURPOSE

To report the clinical characteristics of eyes with an unmeasurable small size of foveal avascular zone (FAZ) in the optical coherence tomography angiographic (OCTA) images.

METHODS

Two-hundred sixty-seven eyes of 255 patients (mean age 60.4 years) without retinal and choroidal disorders to cause any type of visual impairment were examined by optical coherence tomography angiography (OCTA; RTVue XR Avanti, Optovue, Fremont, CA). Cross-sectional images at the fovea (DRI-OCT, Topcon, Japan) and fundus autofluorescence (CX-1 MYD/NM, Canon, Japan) were also recorded from all eyes.

RESULTS

Four eyes (1.5%) of 3 patients (2 men, 1 woman; average age, 63.3 years) were found to have an unmeasurable small size of FAZ in the OCTA images. The best-corrected visual acuity was better than 20/20 in all eyes. Cross-sectional OCT images showed the presence of a foveal depression and the inner retinal layers in the foveal depression. These inner retinal layers were detected as a hyperreflective bands at the fovea. Fundus autofluorescence showed hypo-autofluorescence at the fovea as in normal eyes.

CONCLUSIONS

An unmeasurable small size of FAZ without visual impairment was detected in 1.5% of 267 normal eyes. These eyes may be classified as low-grade foveal hypoplasia.

Assessing the Accuracy of Foveal Avascular Zone Measurements Using Optical Coherence Tomography Angiography: Segmentation and Scaling

PURPOSE

The foveal avascular zone (FAZ) is altered in numerous diseases. We assessed factors (axial length, segmentation method, age, sex) impacting FAZ measurements from optical coherence tomography (OCT) angiography images.

METHODS

We recruited 116 Caucasian subjects without ocular disease, and acquired two 3 × 3 mm AngioVue scans per each right eye (232 total scans). In images of the superficial plexus, the FAZ was segmented using the AngioVue semiautomatic nonflow measurement tool and ImageJ manual segmentation. In images from the full retinal thickness, the FAZ was segmented using the AngioAnalytics automatic FAZ tool. Repeatability, reliability, and reproducibility were calculated for FAZ measurements (acircularity, area).

RESULTS

FAZ area (mean ± SD) for manual segmentation was 0.240 ± 0.0965 mm2, greater than both semiautomatic (0.216 ± 0.0873 mm2) and automatic (0.218 ± 0.0869 mm2) segmentation (P < 0.05). Not correcting for axial length introduced errors up to 25% in FAZ area. Manual area segmentation had better repeatability (0.020 mm2) than semiautomatic (0.043 mm2) or automatic (0.056 mm2). FAZ acircularity had better repeatability with automatic than manual segmentation (0.086 vs. 0.114). Reliability of all area measurements was excellent (intraclass correlation coefficient [ICC] = 0.994 manual, 0.969 semiautomatic, 0.948 automatic). Reliability of acircularity measurements was 0.879 for manual and 0.606 for automatic.

CONCLUSION

We identified numerous factors affecting FAZ measurements. These errors confound comparisons across studies and studies examining factors that may correlate with FAZ measures.

TRANSLATIONAL RELEVANCE

Using FAZ measurements as biomarkers for disease progression requires assessing and controlling for different sources of error. Not correcting for ocular magnification can result in significant inaccuracy in FAZ measurements, while choice of segmentation method affects both repeatability and accuracy.