Optical Coherence Tomography in the Diagnosis of Foveal Hypoplasia

It is frequently difficult to diagnose ocular albinism or foveal hypoplasia in patients who have darkly pigmented hair, skin, or irides. Fundus findings may be subtle and most commonly include the absence of foveal pigmentation or the circumfoveal light reflex.¹ Traditionally in such cases, the diagnosis has been based on the detection of nystagmus coupled with fluorescein angiographic demonstration of a poorly formed capillary-free zone. Since these findings may be difficult to detect, especially in the setting of nystagmus, foveal hypoplasia may be more common than is generally believed.

Optical coherence tomography (OCT) is a noninvasive imaging modality that produces high-resolution, 2-dimensional images of ocular structures. We report the use of OCT to establish a diagnosis of foveal hypoplasia in a patient with decreased vision, in whom the diagnosis had been suspected clinically.

A 45-year-old white woman was referred for evaluation of bilaterally decreased vision. She related a history of nystagmus, high myopia, and poor vision since childhood. She was not born prematurely and was systemically healthy. Her family history was notable for poor vision, nystagmus, and early cataracts in her paternal grandmother, father, and sister.

The patient exhibited no signs of cutaneous albinism. Her best-corrected visual acuity was 20/80 OU and her pupillary responses were normal. Mild horizontal nystagmus and a 15 prism diopter exotropia were present. A 1-mm corneal pannus encompassed the superior 270° of each eye. The fundi were lightly pigmented. The optic nerves were normal. In each eye, the retinal vessels were slightly dragged temporally, and foveal reflexes were absent (Figure 1).

Fluorescein angiography revealed an irregular capillary-free zone in each eye. In the right eye, several vessels traversed the peripheral aspects of the capillary-free zone. No choroidal neovascularization was seen in either eye. Electroretinographic amplitudes were within normal limits.

Following pupillary dilation, a commercial OCT unit (Humphrey Instruments, Zeiss-Humphrey, San Leandro, Calif) was used to obtain 5.92-mm radial sections through the entire macular area of each eye (Figure 2A and B). Standard OCT software was used to generate retinal topographic measurements. In all sections, the retina was of normal thickness and no foveal depression was detectable (Figure 2 D and E). Instead, there was continuity of multiple retinal layers through the area where the foveal center was expected to be located.

Foveal hypoplasia is an ocular abnormality that may be seen in isolation or in association with other ocular or systemic signs. Typical associated findings include nystagmus, aniridia or iris transillumination, cataract, and skin hypopigmentation. Visual acuity is in the range of 20/50 to 20/200.¹ An autosomal dominant syndrome of congenital nystagmus, foveal hypoplasia, corneal pannus, and presenile cataracts has been reported,² and our patient's phenotype and family history are most compatible with this syndrome. In cases with only moderate reduction in vision or without associated signs, the diagnosis of foveal hypoplasia may not be straightforward. The differential diagnosis includes high myopia, early retinal degeneration, and retinopathy of prematurity.

Optical coherence tomography allows detailed examination of macular anatomy. It can thus provide insight into the foveal architecture in patients with foveal abnormalities or visual impairment as well as confirmation of clinical diagnosis, perhaps even obviating the need for electroretinography or angiography.

The OCT findings in this case offer insight into the microanatomy of foveal hypoplasia. Normally, the foveal declivity is evidenced angiographically by a termination of capillaries. Histologically, this area consists of cone photoreceptors and lacks several of the inner retinal layers as well as retinal vasculature.³

In histologic specimens of foveal hypoplasia, by contrast, the structure of the central macula resembles that of the peripheral macula, with persistence of ganglion cells and nuclear layers.⁴ These histologic findings are recapitulated in our patient's OCT data, which show preservation of multiple inner retinal layers when there should be none. We are aware of no other conditions that may produce similar OCT findings. Perhaps a more accurate term for this condition, then, is foveal dysgenesis. In summary, OCT provided a definitive diagnosis of foveal hypoplasia and may prove helpful in the diagnosis of patients with unexplained visual loss.

Support for this research was provided by the Heed Ophthalmic Foundation, Cleveland, Ohio (Dr Recchia).

None of the authors has any proprietary or financial interest in any material or instrumentation presented herein.

Corresponding author and reprints: Michael T. Trese, MD, Associated Retinal Consultants, PC, 3535 W 13 Mile Rd, Suite 632, Royal Oak, MI 48073 (e-mail: mgjt46@aol.com).