The most central part of the macula that enables clear vision, the fovea has a high concentration of cones that lack several inner retinal layers. Foveal hypoplasia is defined as the lack of foveal depression with continuity of all neurosensory retinal layers in the fovea.1 Cones also control the constriction and dilation of the pupil in response to change in light stimulus, namely the pupil light response. It is a useful tool for assessing afferent and efferent defects in neuro-ophthalmic disorders. However, no reports have been published to date regarding the pupil light response in foveal hypoplasia. We have recorded the pupil light response in a patient with unilateral foveal hypoplasia in the absence of other ocular or systemic findings.
A 3-year-old boy had decreased visual acuity in the left eye. Another clinic ophthalmologist and orthoptist performed part-time occlusion therapy (6 hours/day), and then the boy presented to our hospital. Several routine examinations revealed a visual acuity of 6/6 in the right eye and 6/30 in the left eye and cycloplegic refractions of +1.00 diopters (D) in both eyes. This report followed the tenets of the Declaration of Helsinki for research involving human participants and informed consent was obtained from the patient and his parents.
Spectral domain optical coherence tomography of the left eye demonstrated a reduced foveal pit and continuity of the inner retinal layers (Figure 1). An intact foveal contour and normal pigmentation of the macula in the right eye were revealed (Figure 1A) and blunting of the foveal reflex with decreased macular pigmentation was noted in the left eye (Figure 1B).
Spectral domain optical coherence tomography imaging. (A) The right eye appears normal. (B) The left eye shows foveal hypoplasia.
The RETeval (LKC Technologies, Inc., Gaithersburg, MD) system consists of a handheld electroretinography (ERG) recording device with a disposable skin electrode.2Figure 2 shows the actual waveform of ERGs. In the photopic and flicker ERG measurements (Figures 2A–2B), there was a remarkable difference between the normal eye and the affected eye. Scotopic and flash ERGs were slightly different (Figures 2C–2D).
Actual waveform of (A) photopic, (B) flicker, (C) scotopic, and (D) flash electroretinography.
Infrared pupillography (Iriscorder Dual C-10641; Hamamatsu Photonics, Hamamatsu, Japan) was used to measure the pupil response induced by red (635 nm) and blue (470 nm) light stimulus. After 15 minutes of dark adaptation, the response to first red and then blue light stimuli with a light intensity of 2.3 log cd/m2 for 5 seconds was measured. In both eyes, the pupil contraction to the blue light stimulus was greater than to the red light stimulus (Figure 3). Laterality of pupil constriction to the red but not to the blue light stimulus was observed (Figures 3A–3B).
Representative pupil recording data. (A) Red light stimulus. (B) Blue light stimulus.
Foveal hypoplasia is often associated with systemic diseases (aniridia, albinism, microphthalmus, and achromatopsia) and with other visual disorders such as decreased visual acuity (range: 6/18 to 6/60) and nystagmus.1 Oliver et al.3 described 15 patients with isolated bilateral foveal hypoplasia without other ocular or systemic findings. However, unilateral foveal hypoplasia is highly unusual.4
Spectral domain optical coherence tomography has been described as a useful tool to detect foveal hypoplasia, especially in patients with impaired or subnormal vision of unknown etiology. Thomas et al.5 described a novel grading system for the findings of foveal hypoplasia.
The overall ERG responses do not exclude the possibility of a localized foveal defect. Ten of 12 patients with isolated foveal hypoplasia showed normal results in photopic and scotopic ERGs, indicating that their retinal function was normal.3
In contrast, the association between the pupil light response and the neurosensory retinal layers remains unknown in foveal hypoplasia. The pupil response to high-intensity blue light is driven by melanopsin-containing retinal ganglion cells because there are few S cones. Pupil response to red light is mediated mostly by M and L cones.6,7 One hypothesis for the laterality of pupil constriction to red light is a potential effect on melanopsin-containing retinal ganglion cells in the eye with predominantly affecting cones. Our results provide the functional data supporting this hypothesis. However, the differential diagnosis may include early retinal degeneration and retinopathy of prematurity.8 Consequently, these results indicate that the colored-light pupil response can be used to predict the retinal state in patients with foveal hypoplasia.
- Duke-Elder S. The eye in evolution. In: Duke-Elder S, ed. System of Ophthalmology, Vol. 1. London; Henry Kimpton: 1958.
- Kato K, Kondo M, Sugimoto M, Ikesugi K, Matsubara H. Effect of pupil size on flicker ERGs recorded with RETeval System: new mydriasis-free full-field ERG system. Invest Ophthalmol Vis Sci. 2015;56:3684–3690. doi:10.1167/iovs.14-16349 [CrossRef]
- Oliver MD, Dotan SA, Chemke J, Abraham FA. Isolated foveal hypoplasia. Br J Ophthalmol. 1987;71:926–930. doi:10.1136/bjo.71.12.926 [CrossRef]
- Shields RA, Cavuoto KM, McKeown CA, Chang TC. Unilateral foveal hypoplasia in a child with bilateral anterior segment dysgenesis. Clin Case Rep. 2015;3:676–678. doi:10.1002/ccr3.319 [CrossRef]
- 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;118:1653–1660. doi:10.1016/j.ophtha.2011.01.028 [CrossRef]
- Kawasaki A, Collomb S, Léon L, Münch M. Pupil responses derived from outer and inner retinal photoreception are normal in patients with hereditary optic neuropathy. Exp Eye Res. 2014;120:161–166. doi:10.1016/j.exer.2013.11.005 [CrossRef]
- Kurtenbach A, Kernstock C, Zrenner E, Langrová H. Electrophysiology and colour: a comparison of methods to evaluate inner retinal function. Doc Ophthalmol. 2015;131:159–167. doi:10.1007/s10633-015-9512-z [CrossRef]
- Hammer DX, Iftimia NV, Ferguson RD, et al. Foveal fine structure in retinopathy of prematurity: an adaptive optics Fourier domain optical coherence tomography study. Invest Ophthalmol Vis Sci. 2008;49:2061–2070. doi:10.1167/iovs.07-1228 [CrossRef]