Genetic Microcephaly

Ocular anomalies include strabismus, nystagmus and retinal abnormalities

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Eleni Papageorgiou MD
Eleni Papageorgiou MD
Children with genetic microcephaly frequently display ocular anomalies, particularly strabismus, nystagmus and retinal anatomic abnormalities, Eleni Papageorgiou MD, PhD told WSPOS Subspecialty Day 2016 in Copenhagen, Denmark. Optical coherence tomography (OCT) shows significantly thinner perimacular retina, ganglion cell layer, nuclear layers and ellipsoid zone, as well as reduced disc diameters in patients with microcephaly compared with neurologically typical controls. The findings suggest that coincident abnormalities in the retina and central nervous system may have a common genetic cause, said Dr Papageorgiou, who with colleagues at the University of Leicester, UK, conducted an observational study comparing the two groups. Children with genetic microcephaly frequently display ocular anomalies, particularly strabismus, nystagmus and retinal anatomic abnormalities, Eleni Papageorgiou MD, PhD told WSPOS Subspecialty Day 2016 in Copenhagen, Denmark. Optical coherence tomography (OCT) shows significantly thinner perimacular retina, ganglion cell layer, nuclear layers and ellipsoid zone, as well as reduced disc diameters in patients with microcephaly compared with neurologically typical controls. The findings suggest that coincident abnormalities in the retina and central nervous system may have a common genetic cause, said Dr Papageorgiou, who with colleagues at the University of Leicester, UK, conducted an observational study comparing the two groups. VARIABLE RETINAL FINDINGS Microcephaly is defined as head circumference smaller than three standard deviations below the mean, and occurs in about one in 10,000 births, Dr Papageorgiou noted. The study compared ocular characteristics of 27 children with microcephaly, with a mean age of 9.4 years, with 27 age-matched controls, and used handheld OCT to assess differences in the fovea and optic discs. Ocular abnormalities were observed in 22, or 82%, of the 27 microcephaly patients. Nystagmus, mostly gaze-evoked, was the most common abnormal finding, seen in 59% of patients, followed by strabismus in 52%, amblyopia in 26%, and high refractive error in 22%. Optic nerve hypoplasia, chorioretinal dysplasia, retinal pigment anomalies and falciform retinal folds were also observed, reported Dr Papageorgiou, Consultant Paediatric Ophthalmologist, Department of Ophthalmology, University Hospital of 
Larissa, Greece. On OCT examination, thinning of the parafoveal retina was commonly observed among microcephaly patients (see figure), as were foveal pits that were very wide or very steep, Dr Papageorgiou said. Foveal hypoplasia and mottled retinal nerve fibre and ganglion cell layers were also observed in several cases. Comparing mean retinal layer thickness, in microcephaly patients overall retinal thickness was reduced (p=0.001), as were the ganglion cell layer (p<0.001), inner nuclear layer (p<0.001), outer nuclear layer (p=0.007), and inner segment-outer segment junction (p=0.014), Dr Papageorgiou said. While cup diameter and depth were similar in the two groups, disc diameters were consistently smaller in the microcephaly group, though this was not always evident on fundoscopy, Dr Papageorgiou said. OCT revealed a mean disc diameter of 1.12mm in the microcephaly group compared with 1.20mm in controls, she noted. “The findings are possibly due to a reduction in retinal cell number and retinal size parallel to the reduction in brain neurons and brain size observed in microcephaly. We hypothesise there may be some common gene expression in the central nervous system and retina,” Dr Papageorgiou concluded. Eleni Papageorgiou: e_papage@yahoo.com Microcephaly is defined as head circumference smaller than three standard deviations below the mean, and occurs in about one in 10,000 births, Dr Papageorgiou noted. The study compared ocular characteristics of 27 children with microcephaly, with a mean age of 9.4 years, with 27 age-matched controls, and used handheld OCT to assess differences in the fovea and optic discs. Ocular abnormalities were observed in 22, or 82%, of the 27 microcephaly patients. Nystagmus, mostly gaze-evoked, was the most common abnormal finding, seen in 59% of patients, followed by strabismus in 52%, amblyopia in 26%, and high refractive error in 22%. Optic nerve hypoplasia, chorioretinal dysplasia, retinal pigment anomalies and falciform retinal folds were also observed, reported Dr Papageorgiou, Consultant Paediatric Ophthalmologist, Department of Ophthalmology, University Hospital of 
Larissa, Greece. On OCT examination, thinning of the parafoveal retina was commonly observed among microcephaly patients (see figure), as were foveal pits that were very wide or very steep, Dr Papageorgiou said. Foveal hypoplasia and mottled retinal nerve fibre and ganglion cell layers were also observed in several cases. Comparing mean retinal layer thickness, in microcephaly patients overall retinal thickness was reduced (p=0.001), as were the ganglion cell layer (p<0.001), inner nuclear layer (p<0.001), outer nuclear layer (p=0.007), and inner segment-outer segment junction (p=0.014), Dr Papageorgiou said. While cup diameter and depth were similar in the two groups, disc diameters were consistently smaller in the microcephaly group, though this was not always evident on fundoscopy, Dr Papageorgiou said. OCT revealed a mean disc diameter of 1.12mm in the microcephaly group compared with 1.20mm in controls, she noted. “The findings are possibly due to a reduction in retinal cell number and retinal size parallel to the reduction in brain neurons and brain size observed in microcephaly. We hypothesise there may be some common gene expression in the central nervous system and retina,” Dr Papageorgiou concluded. Eleni Papageorgiou: e_papage@yahoo.com