Five-year-old girl referred due to poor vision
Alignment testing showed esotropia and complex nystagmus, and fundoscopic exam showed bilateral mild optic nerve pallor.
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A 5-year-old girl was referred to the New England Eye Center for an eye exam after failing a vision test at her pediatrician’s office.
Her family reported that she held things close to her face in order to inspect them. She was previously prescribed glasses with myopic correction, which she wore at school but usually not at home. She also had a history of intermittent esotropia. Part-time patching was previously attempted with no substantial improvement in vision. Her medical history included global developmental delay, cerebral palsy with left-sided spastic hemiplegia and left ankle contracture, treated with an Achilles tendon tenotomy at age 2 years. She did not take any medications and had no known drug allergies. She lived with her grandmother who was her legal guardian. Her mother had a history of alcohol and drug abuse during pregnancy. Family medical history included diabetes and hypertension in several relatives, but family ocular history was unremarkable.
Examination
The patient’s best corrected visual acuities were 20/400 in the right eye and 20/80 in the left eye, using Allen cards. Her cycloplegic refraction was –5.00 sphere in the right eye and –4.00 +1.25 × 110 in the left eye. Pupils were equal, round and reactive to light, with no relative afferent pupillary defect. IOPs taken with an Icare tonometer were 15 mm Hg in the right eye and 17 mm Hg in the left eye. Extraocular movements were full. Alignment testing revealed an alternating esotropia and complex nystagmus with irregular waveforms with both vertical (upbeat) and horizontal (not clearly directional) oscillations. Null point of the nystagmus was in left gaze. Confrontation visual fields were unreliable. Worth 4-dot testing revealed suppression of the right eye at distance and near. The Stereo Butterfly test revealed no stereoacuity. External and anterior segment exams were unremarkable.
Source: Malgorzata Dymerska Peterson, MD, Thomas R. Hedges III, MD, and Paul D. Reese, MD
Fundoscopic examination revealed clear vitreous bilaterally. Optic nerves had mild pallor with nasal peripapillary atrophy or partial double-ring appearance bilaterally (Figure 1). The cup-to-disc ratio was about 0.4 in both eyes. Maculae appeared normal bilaterally. The retinal vessels appeared to be of normal course and caliber bilaterally.
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Bilateral poor vision in a child
The differential diagnosis for a child with bilateral poor vision, strabismus, nystagmus and optic nerve atrophy includes optic nerve hypoplasia, hereditary optic nerve atrophy, congenital glaucoma, anterior visual pathway gliomas, and retinal dystrophies such as Leber congenital amaurosis, congenital stationary night blindness and achromatopsia.
Optic nerve hypoplasia is typically associated with a characteristic double-ring appearance of the optic nerve but can also present with optic nerve atrophy, such as seen in our patient. Hereditary optic nerve atrophy (autosomal dominant, autosomal recessive, X-linked and mitochondrial) was considered, although there was no family history of ocular disease. Congenital glaucoma was thought less likely given normal IOP and no indication of buphthalmos or optic nerve cupping. In the setting of bilateral optic nerve atrophy, the patient must be evaluated for neoplastic processes such as optic nerve, chiasmal or hypothalamic gliomas, suprachiasmal tumors and meningiomas. Retinal dystrophies can initially be associated with unremarkable fundoscopic findings and should be considered in a child with poor vision. Other etiologies, such as previous optic neuritis and previous papilledema, can also lead to optic nerve atrophy.
Additional workup
If optic nerve hypoplasia is suspected in a child, the utmost priority should be given to evaluation of pituitary hormone levels, given the potentially life-threatening consequences, especially if the clinical context is suggestive of pituitary gland dysfunction. Given the complex nystagmus and pronounced optic nerve atrophy in our patient, however, MRI imaging of the brain was obtained first. It showed bilateral optic nerve atrophy (Figure 2), absence of the septum pellucidum and right-sided closed lip schizencephaly lined by dysplastic gray matter (Figure 3), most compatible with septo-optic dysplasia. No pituitary gland abnormalities were noted on the MRI of the brain. However, the patient was referred back to the pediatrician for urgent pituitary hormone testing.
Discussion
Optic nerve hypoplasia is a congenital abnormality of the optic nerve. It occurs secondary to disruption of normal optic nerve development during embryogenesis. Fetal alcohol syndrome and maternal use of quinine, phenytoin and LSD during pregnancy have been described as possible associations, although frequently the etiology is unclear. Segmental hypoplasia of the optic nerve can also occur and is associated with maternal type 1 diabetes.
On clinical examination, the optic disc may appear smaller than expected, and there may be an associated double ring of chorioretinal atrophy around the optic nerve. The appearance of the optic disc in our patient was different from the typical double-ring atrophy seen in severe optic nerve hypoplasia. However, the disc may exhibit pallor, as in our patient. There may also be an abnormal number of optic disc vessels, and retinal vasculature may exhibit increased tortuosity.
The majority of patients have bilateral involvement, but unilateral optic nerve hypoplasia can also occur. Vision varies from normal to severely diminished. Visual field defects occur frequently with optic nerve hypoplasia, with inferior and nasal defects being most common. The degree to which vision is affected does not necessarily correspond to the degree of hypoplasia of the nerve. Patients with bilateral optic nerve hypoplasia often develop congenital sensory nystagmus. Strabismus may also be present.
About 15% of patients with optic nerve hypoplasia, whether unilateral or bilateral, have abnormalities of the pituitary gland. This commonly manifests with growth hormone deficiency, but other pituitary hormones may also be affected. The child’s ability to thermoregulate may be affected, and neonatal hypoglycemia may result; thus, patients with suspected optic nerve hypoplasia, whether unilateral or bilateral, should undergo further endocrinologic workup as soon as possible.
Optic nerve hypoplasia is also associated with abnormalities of midline structures in the brain, so an MRI is indicated for further evaluation. Septo-optic dysplasia (de Morsier syndrome) is a combination of optic nerve hypoplasia and an absent septum pellucidum. Other brain abnormalities that can occur are anomalies of the corpus callosum, schizencephaly, encephalomalacia and periventricular leukomalacia.
- References:
- Basic and Clinical Science Course Neuro-Ophthalmology. Chapter 4: The patient with decreased vision: classification and management. Congenital optic nerve head anomalies. American Academy of Ophthalmology. 2017-2018;143-144.
- Basic and Clinical Science Course Pediatric Ophthalmology and Strabismus. Chapter 26: Optic disc abnormalities. American Academy of Ophthalmology. 2017-2018;353-355.
- Borchert M. J Neuroophthalmol. 2012;doi:10.1097/WNO.0b013e31824442b8.
- Brodsky MC, et al. Arch Ophthalmol. 1993;doi:10.1001/archopht.1993.01090010070029.
- Lambert SR, et al. Surv Ophthalmol. 1987;doi:10.1016/0039-6257(87)90069-5.
- Skarf B, et al. Arch Ophthalmol. 1984;doi:10.1001/archopht.1984.01040030046032.
- For more information:
- Malgorzata Dymerska Peterson, MD, Thomas R. Hedges III, MD, and Paul D. Reese, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Christine Benador-Shen, MD, and Malgorzata Dymerska Peterson, MD. They can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.