Kerala Journal of Ophthalmology

OPHTHA INSTA
Year
: 2020  |  Volume : 32  |  Issue : 2  |  Page : 126--127

The mystery of the missing pit


Neethu Pradeep, N Sujatha, V Sudha, PV Geethakumari 
 Department of Ophthalmology, Government Medical College, Thrissur, Kerala, India

Correspondence Address:
Dr. Neethu Pradeep
Department of Ophthalmology, Government Medical College, Thrissur, Kerala
India

Abstract

Foveal hypoplasia refers to the underdevelopment of fovea, characterized by the continuity of the inner retinal layers in the presumed foveal area; the foveal avascular zone may be limited or absent, and retinal vessels may be seen coursing through the foveal region. It is usually associated with aniridia, albinism, achromatopsia, or retinopathy of prematurity. Isolated foveal hypoplasia is a rare clinical entity. We hereby report a case of congenital nystagmus with foveal hypoplasia. Fundus finding in isolated foveal hypoplasia though typical is very subtle and often difficult to detect, especially due to accompanying nystagmus. The presence of nystagmus and poor vision in infants or children without any ocular finding should prompt the ophthalmologist to carry out a thorough fundus examination of the foveal area and to perform an optical coherence tomography to confirm the diagnosis.



How to cite this article:
Pradeep N, Sujatha N, Sudha V, Geethakumari P V. The mystery of the missing pit.Kerala J Ophthalmol 2020;32:126-127


How to cite this URL:
Pradeep N, Sujatha N, Sudha V, Geethakumari P V. The mystery of the missing pit. Kerala J Ophthalmol [serial online] 2020 [cited 2020 Sep 30 ];32:126-127
Available from: http://www.kjophthal.com/text.asp?2020/32/2/126/293302


Full Text



A 6 year old boy was brought by the mother with complaints of abnormal eye movements since birth. There was no history of day or night blindness, photophobia, or prematurity. No significant family history was noted. General and systemic examination was unremarkable. Ocular examination showed pendular nystagmus. Best-corrected visual acuity was 6 / 36 both eye. Anterior segment examination was within the normal limits. Pupillary reactions were brisk. Dilated fundus examination and fundus photo revealed a normal optic nerve head with absent foveal reflex [Figure 1]. Optical coherence tomography (OCT) showed the absence of foveal depression and persistence of inner retinal layers at fovea, i.e., without extrusion of plexiform layers, outer segment lengthening, or outer nuclear layer widening (Grade 4 foveal hypoplasia)[1][Figure 2].{Figure 1}{Figure 2}

Clinical finding: Isolated Foveal Hypoplasia

Cardinal diagnostic features

Clinical: Nystagmus, brisk pupil with fundus showing normal optic nerve head and absent foveal reflex.

OCT: Thomas et al.[1] proposed a structural grading system of foveal hypoplasia based on OCT.

Grade 1-Extrusion of plexiform layers with a shallow foveal pit, outer segment lengthening, and outer nuclear layer wideningGrade 2-Grade1 with the absence of a foveal pitGrade 3-Grade2 with the absence of outer segment lengtheningGrade 4-Grade 3 with the absence of outer nuclear layer widening.Atypical-Absence of extrusion of plexiform layers with a shallow foveal pit and IS/OS disruption.

OCT being noninvasive is the preferred investigation for confirming the diagnosis.

FFA shows the absence of foveal avascular zone (FAZ), but being an invasive procedure, it is not easily done in children.

Seen in

Foveal hypoplasia[2] can be isolated or associated with albinism, aniridia, achromatopsia, microphthalmos, retinopathy of prematurity, and incontinentia pigmenti.

Described by

Waardenburg in 1963 described foveal hypoplasia and stated that it may occur as an isolated defect.[3]

Why it occurs

Normal foveal development begins at fetal week 25 and is completed 15–45 months after birth. The development of the foveal pit involves the bidirectional movement of neurons in the inner and outer retina. The cells of the inner retina are displaced centrifugally to form the foveal pit, and the cones are displaced centripetally so that the density of cones in the foveal pit increases.[4] Foveal hypoplasia is a condition in which the foveal pit does not fully develop and is characterized by the absence of foveal pigmentation and/or the FAZ. Hypomorphic mutations of the PAX6 gene is known to cause isolated foveal hypoplasia, which has autosomal dominant inheritance.[5] Recently, mutations in the SLC38A8 gene were identified to have an autosomal-recessive type of isolated foveal hypoplasia.[6]

What else to examine

Look for nystagmus, aniridia, and albinism. The clinical diagnosis is often missed due to the subtle nature of the fundus finding. This report illustrates the importance of careful examination of foveal area in infants and children with poor vision and nystagmus and to perform an OCT to confirm the diagnosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Thomas MG, Kumar A, Mohammad S, Proudlock FA, Engle EC, Andrews C, et al. Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity? Ophthalmology 2011;118:1653-60.
2Oliver MD, Dotan SA, Chemke J, Abraham FA. Isolated foveal hypoplasia. Br J Ophthalmol 1987;71:926-30.
3Wardenburg PJ. Genetics and Ophthalmology. Vol. 2. Assen: Royal Van Gorcum; 1963. p. 1722-3.
4Provis JM, Dubis AM, Maddess T, Carroll J. Adaptation of the central retina for high acuity vision: Cones, the fovea and the avascular zone. Prog Retin Eye Res 2013;35:63-81.
5Azuma N, Nishina S, Yanagisawa H, Okuyama T, Yamada M. PAX6 missense mutation in isolated foveal hypoplasia. Nat Genet 1996;13:141-2.
6Poulter JA, Al-Araimi M, Conte I, van Genderen MM, Sheridan E, Carr IM, et al. Recessive mutations in SLC38A8 cause foveal hypoplasia and optic nerve misrouting without albinism. Am J Hum Genet 2013;93:1143-50.