Foveal architecture plays a critical role in visual function. The fully developed fovea has a central depression, known as the foveal pit, and an elevation in the ellipsoid zone (EZ). There is loss of foveal vasculature and inner retinal layers during fetal development. Additionally, there is centripetal migration of cones that causes the fovea to be highly compact with tall and slender cone photoreceptors, which then causes a small elevation in the ellipsoid layer of the central fovea. This is usually symmetric. Foveal hypoplasia results in the incomplete or absent development of the fovea and is clinically characterized by lack of a foveal light reflex and occasionally mild pigmentary changes. The foveal avascular zone (FAZ) can go undetected on fluorescein angiography (FA) but appears hypoautofluorescent on autofluorescence.1–6 Optical coherence tomography (OCT) can provide valuable insights by demonstrating inner retinal layer continuity beyond the fovea, loss of the foveal contour, and a flat central EZ. Foveal hypoplasia can be an isolated finding, but it has also been noted in several conditions including albinism, PAX6 mutations, aniridia, retinopathy of prematurity, microphthalmus, and achromatopsia.4
Optical coherence tomography angiography (OCTA) is a new imaging technique that noninvasively visualizes retina vessels in addition to providing cross-sectional images of the retina as with standard OCT. Although FA represents the standard method for assessing retinal circulation, OCTA has demonstrated a unique ability to discern capillary networks at different retinal layers as well as demonstrating large retinal vessels.7–10 OCTA has recently been used to study several diseases, including age-related macular degeneration, retinal vascular events, and glaucoma.11,12
Here, we provide the first descriptions of OCTA in patients with foveal hypoplasia, including in a patient with unilateral foveal hypoplasia, which is extremely rare. A normal OCTA has been provided as a reference (Figure 1).
Optical coherence tomography angiography of the left eye of a normal person; the images of superficial (left image) and deep (right image) capillary plexus clearly illustrate the foveal avascular zone.
A 5-year-old girl was brought to the eye clinic because her parents noticed she had difficulty seeing objects. Cycloplegic refraction was plano-3.5×180° in right eye and plano-2.75×170° in left eye. She was without nystagmus, and her examination demonstrated normal anterior segments without any ocular misalignment. Bilaterally blunted foveal reflexes were apparent on dilated fundus exam (Figure 2). Fundus photographs (TRC50LX; Topcon, Tokyo, Japan), spectral-domain OCT (SD-OCT) (HRA 2; Heidelberg Engineering, Heidelberg, Germany), and OCTA (Optovue, Fremont, CA) were obtained. SD-OCT confirmed diagnosis of foveal hypoplasia by revealing reduced foveal depression in addition to continuity of the inner retinal layers in both foveae (Figure 2). OCTA demonstrated an absence of a definite FAZ in both superficial and deep capillary plexus of her right eye. Her left eye had a small FAZ in the deep capillary plexus but did not have a FAZ in the superficial capillary plexus.
Imaging of the right (top panel) and left (bottom panel) eye in a 5-year-old girl with foveal hypoplasia. Blunted foveal reflex is seen in the fundus photos (A, E). There is a lack of the foveal avascular zone (FAZ) in the superficial capillary plexus of both eyes (B, F). There is an absent deep capillary plexus FAZ in the right eye (C), but a small deep capillary plexus in the left eye (G). Spectral-domain optical coherence tomography in both eyes (D, H) demonstrates inner retinal layer continuity and a slightly shallow foveal contour.
A 40-year-old woman was referred for a routine ophthalmologic examination. Best-corrected visual acuity (BCVA) was 20/25 and 20/30 in the right and left eyes, respectively. Her refraction was plano-0.5 ×80° in the right eye and −0.5 sphere in the left eye. Her ophthalmic examination was unremarkable except for the lack of a foveal reflex on funduscopic examination. SD-OCT revealed bilateral decreased foveal depression with uninterrupted inner retinal layers consistent with foveal hypoplasia (Figure 3). OCTA demonstrated an absence of the FAZ in the superficial capillary plexi and a small FAZ in deep capillary plexi in both eyes (Figure 3).
Spectral-domain optical coherence tomography (SD-OCT) and OCT angiography (OCTA) of a 40-year-old woman with bilateral foveal hypoplasia (case 2; top panel, right eye; bottom panel, left eye). SD-OCT with decreased foveal depression with continuity of the inner retina in both eyes (A, D). Both eyes lack a foveal avascular zone (FAZ) in the superficial capillary plexus but have a small deep capillary plexus FAZ.
A 22-year-old man was referred to our clinic with the chief complaint of poor vision in the right eye since childhood. His refraction and BCVA were plano and 20/40, respectively, in the right eye and +0.50 and 20/20, respectively, in the left eye. Except for a blunted foveal reflex in his right eye, his ocular examination was unremarkable. The patient was without a FAZ on FA and had a loss of the foveal depression with inner retinal layer continuity on SD-OCT in the right eye, whereas the left eye had normal imaging findings. OCTA in the right eye provided more details of the FAZ when compared to FA. Right eye OCTA demonstrated severely reduced FAZ in the superficial vascular plexus and a present FAZ in the deep capillary plexus, with normal vascular appearance in the left eye (Figure 4).
Multimodal imaging of a 22-year-old man with unilateral foveal hypoplasia. (A) Fundus photograph of the right eye showed no foveal reflex. (B) Fundus fluorescein angiography showed lack of a foveal avascular zone (FAZ). (C, D) Fundus autofluorescence and infrared imaging with equivocal findings. (E) Spectral-domain optical coherence tomography (SD-OCT) reveals a shallow foveal pit and continuity of inner retinal layer. (F) OCT angiography with an extremely small FAZ in the superficial capillary plexus.
Given the patient's characteristic findings in the right eye, he was diagnosed with unilateral foveal hypoplasia.
Patients with foveal hypoplasia can have a wide range of vision, from normal to severely impaired.6 Although characteristic clinical, FA, and OCT findings have been described, the diagnosis can be challenging in those with equivocal presentations. OCTA enables imaging of deeper retinal plexi and the ability to visualize different capillary layers separately.
This series provides the first descriptions of OCTA in eyes with foveal hypoplasia. All affected eyes had an absent or severely reduced FAZ in the superficial capillary plexus, whereas four eyes had a small but present FAZ in the deep capillary plexus. Reliable visual acuity could not be attained in our first case due to the patient's age, whereas the second case in this series maintained good vision. The third case in our series had unilateral foveal hypoplasia, which is exceptionally rare.13 The visual acuity in his affected eye was diminished, possibly from an element of amblyopia due to the unilateral nature of his disease. Thomas et al. found that a structural grading system they developed for foveal hypoplasia, based on the stage of foveal development cessation, provided a prognostic indicator for visual acuity.14 The degree of FAZ constriction and presence of the deep capillary plexus FAZ on OCTA may serve to characterize foveal hypoplasia, and future studies should investigate its predictive value on vision. We would anticipate that the size of the FAZ on OCTA would correlate with visual potential, and may even serve to assess the utility of amblyopia therapy in children with unilateral foveal diseases. All our cases had isolated foveal hypoplasia. Future investigations may help to further clarify the pathophysiologic importance of a present deep capillary plexus FAZ and degree of FAZ attenuation and how they may relate to associated conditions such as albinism. OCTA holds promise in the assessment of subnormal vision and may be helpful in detecting subtle cases of foveal hypoplasia.
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- Mendis KR, Balaratnasingam C, Yu P, et al. Correlation of histologic and clinical images to determine the diagnostic value of fluorescein angiography for studying retinal capillary detail. Invest Ophthalmol Vis Sci. 2010;51(11):5864–5869. doi:10.1167/iovs.10-5333 [CrossRef]
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- Thomas MG, Kumar A, Mohammad S, et al. Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity?Ophthalmology. 2011;118(8):1653–1660. doi:10.1016/j.ophtha.2011.01.028 [CrossRef]