Spectrum of optic nerve hypoplasia

Aberrant gene expression yet undiminished retinal ganglion cell genesis in iPSC-derived models of optic nerve hypoplasia

BACKGROUND

Optic nerve hypoplasia (ONH), the leading congenital cause of permanent blindness, is characterized by a retinal ganglion cell (RGC) deficit at birth. Multifactorial developmental events are hypothesized to underlie ONH and its frequently associated neurologic and endocrine abnormalities; however, environmental influences are unclear and genetic underpinnings are unexplored. This work investigates the genetic contribution to ONH RGC production and gene expression using patient induced pluripotent stem cell (iPSC)-derived retinal organoids (ROs).

MATERIALS AND METHODS

iPSCs produced from ONH patients and controls were differentiated to ROs. RGC genesis was assessed using immunofluorescence and flow cytometry. Flow-sorted BRN3+ cells were collected for RNA extraction for RNA-Sequencing. Differential gene expression was assessed using DESeq2 and edgeR. PANTHER was employed to identify statistically over-represented ontologies among the differentially expressed genes (DEGs). DEGs of high interest to ONH were distinguished by assessing function, mutational constraint, and prior identification in ONH, autism and neurodevelopmental disorder (NDD) studies.

RESULTS

RGC genesis and survival were similar in ONH and control ROs. Differential expression of 70 genes was identified in both DESeq2 and edgeR analyses, representing a ~ 4-fold higher percentage of DEGs than in randomized study participants. DEGs showed trends towards over-representation of validated NDD genes and ONH exome variant genes. Among the DEGs, RAPGEF4 and DMD had the greatest number of disease-relevant features.

CONCLUSIONS

ONH genetic background was not associated with impaired RGC genesis but was associated with DEGs exhibiting disease contribution potential. This constitutes some of the first evidence of a genetic contribution to ONH.

Non-Arteritic Anterior Ischaemic Optic Neuropathy Associated with Optic Nerve Hypoplasia and Elevated Intraocular Pressure

A 46-year-old woman with no known past medical history presented with sudden painless visual impairment in the left eye. Ocular examination showed a swollen and hyperaemic left optic disc with a small and crowded right optic disc. Intraocular pressures were moderately elevated. Investigations for underlying ischaemic and inflammatory markers were normal. A diagnosis of left non-arteritic anterior ischaemic optic neuropathy (NAAION) was made, with associated ocular hypertension. On follow-up, NAAION resolved with anti-glaucoma medication and repeat fundus examination confirmed the presence of an underlying hypoplastic disc. The coexistence of optic disc hypoplasia and elevated intraocular pressure may further augment the risk of developing NAAION.

Thinner retinal nerve fibre layer in young adults with foetal alcohol spectrum disorders

BACKGROUND/AIMS

Ophthalmological abnormalities such as ptosis, strabismus, refractive errors and optic nerve hypoplasia have been reported in foetal alcohol spectrum disorders (FASD). The purpose of this study was to investigate whether retinal thickness, retinal nerve fibre layer (RNFL) and optic disc area (ODA) differ between individuals with FASD and healthy controls.

METHODS

Best-corrected visual acuity (BCVA) in terms of logarithm of the minimum angle of resolution (logMAR), refraction, and fundus variables measured by optical coherence tomography were obtained from 26 young adults with FASD (12 women, median age 23 years) and 27 controls (18 women, median age 25 years).

RESULTS

The total thickness of the peripapillary RNFL was significantly lower in the FASD group than in controls; median (range) in the right/left eye was 96.5 (60-109)/96 (59-107) µm in the FASD group and 105 (95-117)/103 (91-120) µm among controls (p=0.001 and p=0.0001). Macular RNFL and retinal thickness measurements from the FASD group were also lower in most of the nine ETDRS areas, except for the central parts. Median (range) BCVA in the best eye was 0.00 (-0.1-0.3) logMAR in the FASD group and 0.00 (-0.2-0.0) logMAR in controls (p=0.001). No significant differences between the groups were found regarding ODA or refraction.

CONCLUSION

Significant differences in peripapillary and macular RNFL, retinal thickness and BCVA were found in this group of young adults with FASD compared with healthy controls. However, there were no differences in the size of the optic disc.

Non-Cell Autonomous Roles for CASK in Optic Nerve Hypoplasia

Purpose

Heterozygous mutations in the essential X-linked gene CASK associate with optic nerve hypoplasia (ONH) and other retinal disorders in girls. CASK^+/− heterozygous knockout mice with mosaic CASK expression exhibit ONH with a loss of retinal ganglion cells (RGCs) but no changes in retinal morphology. It remains unclear if CASK deficiency selectively affects RGCs or also affects other retinal cells. Furthermore, it is not known if CASK expression in RGCs is critical for optic nerve (ON) development and maintenance.

Methods

The visual behavior of CASK^+/− mice was assessed and electroretinography (ERG) was performed. Using a mouse line with a floxed CASK gene that expresses approximately 40% CASK globally in all cells (hypomorph) under hemizygous and homozygous conditions, we investigated effects of CASK reduction on the retina and ON. CASK then was completely deleted from RGCs to examine its cell-autonomous role. Finally, for the first time to our knowledge, we describe a hemizygous CASK missense mutation in a boy with ONH.

Results

CASK^+/− heterozygous mutant mice display reduced visual contrast sensitivity, but ERG is indistinguishable from wildtype. CASK hypomorph mice exhibit ONH, but deletion of CASK from RGCs in this background does not exacerbate the condition. The boy with ONH harbors a missense mutation (p.Pro673Leu) that destabilizes CASK and weakens the crucial CASK–neurexin interaction.

Conclusions

Our results demonstrate that mosaic or global reduction in CASK expression and/or function disproportionately affects RGCs. CASK expression in RGCs does not appear critical for cell survival, indicating a noncell autonomous role for CASK in the development of ON.

Abnormalities of the Optic Nerve in Down Syndrome and Associations With Visual Acuity

Background: Various ocular anomalies are present in the vast majority of individuals with Down syndrome; however, we know little about optic nerve abnormalities. The aim of this cross-sectional comparative study was to describe optic disc morphology in patients with Down syndrome and to determine if the differences found are potentially related to visual acuity.

Subjects/methods: Assessable fundus images were obtained in 50 children with Down syndrome and 52 children without Down syndrome. Morphological analysis of the optic nerve was performed, including the disc-to-macula distance (DM) to disc diameter (DD) ratio (DM/DD), the cup-to-disc ratio and optic disc ovality. Data relating to ophthalmological status were retrospectively analyzed to evaluate the possible causes of reduced visual acuity.

Results: DM/DD was significantly larger (p = 0.0036) and the cup-to-disc ratio was significantly smaller (p = 0.018) in children with Down syndrome, compared to controls. The optic discs were also more frequently torted (p = 0.034), tilted (p = 0.0049) and oval (p = 0.026). Furthermore, crescents (p = 0.0002), peripapillary atrophy (p = 0.0009), and pigment anomalies (p < 0.0001) were also more prevalent in children with Down syndrome than in those without. Visual acuity was significantly lower in children with Down syndrome compared to controls with similar refraction problems and strabismus prevalence (p < 0.0001). The mean DM/DD and the presence of a crescent was not directly related to visual acuity (r = 0.39, p = 0.31), (r = 0.35, p = 0.12) respectively. Visual acuity was diminished in 80% of children with Down syndrome and the smallest discs and in 84% of those with tilted discs. However, other causes may contribute to the diminished visual acuity in these cases.

Conclusion: The optic nerve head in children with Down syndrome is affected by various anatomical and developmental abnormalities. Unrelated to refraction (spherical equivalent), the optic discs appear smaller and more frequently mal-inserted in Down syndrome. Optic disc hypoplasia, as well as severe tilting, may reduce vision but they do not represent major contributors to the decrease of vision in such children. As these children often have multiple ocular and neurosensory problems, it remains challenging to relate visual acuity problems with a specific abnormality. Smaller discs may lead to optic disc drusen formation in children with Down syndrome.

Clinical features of superior segmental optic hypoplasia: hospital-based study

PURPOSE

To determine the clinical features of patients diagnosed with superior segmental optic hypoplasia (SSOH) and to quantitatively compare retinal nerve fiber layer (RNFL) thickness in SSOH eyes, to that in normal subjects.

STUDY DESIGN

Retrospective comparative case series.

METHODS

We examined the medical charts of 106 eyes of 59 patients with SSOH and 35 eyes of 35 normal subjects as controls. Forty-four of 59 patients had been examined by spectral-domain optical coherence tomography (SD-OCT). Eyes with SSOH were classified into a definite and a suspect type determined by standard automated perimetry. The definite type had inferior visual field (VF) defects, while the suspect type did not have inferior VF defects. The findings of the SD-OCT images of 35 eyes with SSOH were compared to those of the 35 normal eyes.

RESULTS

Of the 106 eyes with SSOH, 56 (52.8%) were classified as the definite type and 50 (47.2%) as the suspect type. OCT showed that the average of the total RNFL thickness was significantly thinner in the SSOH group than in the normal group (P < 0.001; Mann-Whitney U test). Sectorial analysis demonstrated that the RNFL was thinner than controls in all quadrants (all P < 0.001; Mann-Whitney U test). The comparison of the hourly sectors showed that the RNFL was thinner at 10, 11, 12, 1, 2, 3, 5, and 6 o'clock sectors in the SSOH group than controls.

CONCLUSIONS

Approximately one-half of eyes with SSOH had a detectable VF defect. OCT showed that eyes with SSOH have a thinner RNFL than controls except in 4 o`clock and from 7 o'clock to 9 o'clock.

Optic Nerve Hypoplasia in Fetal Alcohol Syndrome: An Update

Optic nerve hypoplasia was detected in up to one half of a group of Swedish children born to alcoholic mothers. Using an experimental model of pre- and postnatal alcohol exposure in rats fed a liquid diet, reduced optic nerve size from gestational day 21 (294 ± 26×102 μm2 vs 502 ± 16×102 μm2; n=6; p≤0.001) to later in development was observed as a result of the daily mean blood alcohol levels achieved in dams and their offspring. Altered glial cells and degenerating and atrophic optic axons, myelin sheaths and ganglion cells were frequent in the alcohol-exposed optic nerves.

Smaller optic nerve (1,918 ± 61×102 μm2 vs 2.195 ± 40×102 μm2; n=4; p≤0.001), reduced gaglion cell and axonal densities, and ultrastructural damage to the macroglial cells and myelin sheaths were also detected in the treated group. All these changes remained in the retina and optic nerve of the oldest rats, as a consequence of the long-lasting effects of prenatal alcohol exposure. In summary, alcohol as a major teratogenic agent may induce dysmorphogenesis and irremediable damage to the retina and optic nerve, which frequently manifests itself as hypoplastic optic nerve.

Retinal Nerve Fiber Layer Protrusion Associated with Tilted Optic Discs

SIGNIFICANCE

This study resulted in the identification of an optic nerve head (ONH) feature associated with tilted optic discs, which might potentially contribute to ONH pathologies. Knowledge of such findings will enhance clinical insights and drive future opportunities to understand disease processes related to tilted optic discs.

PURPOSE

The aim of this study was to identify novel retinal nerve fiber layer (RNFL) anomalies by evaluating tilted optic discs using optical coherence tomography. An observed retinal nerve fiber protrusion was further investigated for association with other morphological or functional parameters.

METHODS

A retrospective review of 400 randomly selected adult patients with ONH examinations was conducted in a referral-only, diagnostic imaging center. After excluding other ONH pathologies, 215 patients were enrolled and evaluated for optic disc tilt and/or torsion. Gross anatomical ONH features, including size and rim or parapapillary region elevation, were assessed with stereoscopic fundus photography. Optical coherence tomography provided detailed morphological information of individual retinal layers. Statistical analysis was applied to identify significant changes between individual patient cohorts.

RESULTS

A dome-shaped hyperreflective RNFL bulge, protruding into the neurosensory retina at the optic disc margins, was identified in 17 eyes with tilted optic discs. Available follow-up data were inconclusive regarding natural changes with this ONH feature. This RNFL herniation was significantly correlated with smaller than average optic disc size (P = .005), congenital disc tilt (P < .0001), and areas of rim or parapapillary elevation (P < .0001).

CONCLUSIONS

This study reports an RNFL protrusion associated with tilted optic discs, which has not previously been assessed as an independent ONH structure. The feature is predominantly related to congenital crowded, small optic discs and variable between patients. This study is an important first step to elucidate diagnostic capabilities of tilted disc morphological changes and understanding associated functional deficits.

Ocular Manifestations in Fetal Alcohol Syndrome

PURPOSE

To report the prevalence of ocular abnormalities in a group of Portuguese children with a complete fetal alcohol syndrome (FAS).

METHODS

Complete ophthalmologic examination in a sample of consecutive children with FAS. Ocular fundus photography was carried out on the cooperative FAS children and on 25 reference children. Ocular fundus anomalies were recorded by the observation of ocular fundus photography. The ratio between the distance of the center of the disc to the fovea and optic disc diameter (DM/DD) was determined. Small optic disc was defined as a DM/DD ratio above mean control group +1 SD.

RESULTS

The authors studied 32 children with FAS (mean age: 9 +/- 5 years; 72% boys). The mean corrected visual acuity (VA) was 0.8 +/- 0.2. Refraction ranged from -23.00 to +6.50 spherical equivalent. Ocular findings included short horizontal palpebral fissure (81% of children), strabismus (28% of children), epicanthus (27% of eyes), blepharoptosis (16% of eyes), telecanthus (13% of children), nystagmus (1 child), and cataract (1 eye). Ocular fundus photography analysis showed retinal vessel tortuosity in 30% of the eyes and optic disc hypoplasia in 25%. The mean DM/DD for the control and FAS groups was 2.72 +/- 0.20 and 2.89 +/- 0.25 (p=0.001). Forty percent of the eyes of FAS children had small optic discs.

CONCLUSIONS

The most common ocular findings were anomalies of retinal fundus and minor changes in the outer region of the eyes. The authors noted better VA and less severity of disease than others, which might be due to a different selection of patients, different pattern of alcohol consumption, or genetic differences.

Optic Nerve Hypoplasia Is a Pervasive Subcortical Pathology of Visual System in Neonates

Purpose

Optic nerve hypoplasia (ONH) is the most common cause of childhood congenital blindness in developed nations, yet the fundamental pathobiology of ONH remains unknown. The objective of this study was to employ a ‘face validated' murine model to determine the timing of onset and the pathologic characteristics of ONH.

Methods

Based on the robust linkage between X-linked CASK haploinsufficiency and clinically diagnosed ONH, we hypothesized that heterozygous deletion of CASK (CASK^(+/−)) in rodents will produce an optic nerve pathology closely recapitulating ONH. We quantitatively analyzed the entire subcortical visual system in female CASK^(+/−) mice using immunohistochemistry, anterograde axonal tracing, toluidine blue staining, transmission electron microscopy, and serial block-face scanning electron microscopy.

Results

CASK haploinsuffiency in mice phenocopies human ONH with complete penetrance, thus satisfying the ‘face validity'. We demonstrate that the optic nerve in CASK^(+/−) mice is not only thin, but is comprised of atrophic retinal axons and displays reactive astrogliosis. Myelination of the optic nerve axons remains unchanged. Moreover, we demonstrate a significant decrease in retinal ganglion cell (RGC) numbers and perturbation in retinothalamic connectivity. Finally, we used this mouse model to define the onset and progression of ONH pathology, demonstrating for the first time that optic nerve defects arise at neonatally in CASK^(+/−)mice.

Conclusions

Optic nerve hypoplasia is a complex neuropathology of the subcortical visual system involving RGC loss, axonopathy, and synaptopathy and originates at a developmental stage in mice that corresponds to the late third trimester development in humans.

VEP analysis methods in children with optic nerve hypoplasia: relationship to visual acuity and optic disc diameter

PURPOSE

Assessing vision in young children with optic nerve hypoplasia (ONH) is challenging due to multi-directional infantile nystagmus, the range of optic nerve loss, and cognitive delay. This study examined visual evoked potential (VEP) responses and averaging techniques in children with ONH. The assumption is that EEG epochs with inconsistent temporal phase would be associated with nystagmus, signal reduction due to axon loss, and visual inattention.

METHODS

A retrospective chart review was performed on 44 children (average age 2.2 years; SD 1.9). Optic disc diameter was estimated by ophthalmoscopy. Visual function was measured under binocular viewing and then compared to the eye with the larger optic disc to exclude secondary amblyopia. Visual acuity was measured by Teller cards or by recognition optotypes, and both measures were converted into log minimum angle of resolution (logMAR). VEPs were recorded to onset/offset of horizontal gratings and to reversing checkerboards. Signal-to-noise ratios (SNRs) were estimated from phase consistency across epochs in the Fourier domain. VEPs were also averaged after (1) correction of epochs for phase shifts across a limited bandwidth, or (2) selection of only epochs showing phase consistency.

RESULTS

Optic disc diameter, logMAR, VEP amplitudes, and VEP SNR were all significantly inter-correlated. Optic disc diameter correlated best with VEP SNR (Spearman rho = 0.82; p < 0.001). Age-corrected logMAR correlated with optic disc diameter and VEP SNR (Spearman rho = -0.695 and 0.70, respectively; p < 0.001). VEP latency poorly correlated with optic disc diameter or logMAR. Correction of phase shifts or selection of epochs based on phase consistency significantly increased VEP amplitude and SNR for children with optic disc diameters <1000 microns. Correction of phase inconsistency did not improve the correlation of VEP parameters with optic disc diameter or with logMAR.

CONCLUSIONS

In ONH, the size of the optic nerve is correlated with VEP SNR and logMAR. The results imply a direct relationship between the reduction in optic nerve axons and generalized reduction in visual function. Our calculation of VEP SNR provides objective assessment of optic nerve function that is independent of subjective scoring of VEP peaks.

Ocular, Neurologic and Systemic Findings of the Cases with Optic Nerve Hypoplasia

Aim:

To describe the associated ocular, neurologic, and systemic findings in a population of children with optic nerve hypoplasia (ONH) and to evaluate the relationship between ocular signs and neurologic findings.

Method:

A retrospective chart review of 53 patients with the diagnosis of ONH seen between December 1998 and September 2012 was performed. All neurodevelopmental anomalies, neuroradiologic findings, endocrinologic and systemic findings were recorded. Poor vision was defined as the visual acuity poorer than logMAR 1.0 or inadequate central steady maintained fixation.

Results:

Thirty (56.6%) of the 53 children with ONH were boys. Mean age at presentation was 56.2±46.8 months (range; 3 months to 18 years). Poor vision defined for the purpose of this study was found in 47.2% of 53 patients. Thirty-three (62.3%) children had nystagmus. Thirty-four (64.2%) children had strabismus. Thirteen (38.2%) of those with strabismus had esotropia, 20 (58.8%) had exotropia. The total number of the children with neurodevelopmental deficit was 22 (41.5%) in our study.

Conclusion:

The vision of young children with ONH should be monitored at least annually, and any refractive errors should be treated. Neuroimaging of the brain and endocrinologic evaluation is necessary in all cases with ONH.

Macular optical coherence tomography in patients with unilateral optic nerve hypoplasia

PURPOSE

To characterize the extent and location of macular thinning in patients with unilateral optic nerve hypoplasia (ONH) as compared to the contralateral normal eye.

METHODS

The medical records of patients with unilateral ONH who underwent spectral domain optical coherence tomography (SD-OCT) of the macula were retrospectively reviewed. SD-OCT scans were manually segmented by 3 observers in 3 macular regions (superior, central, inferior). Boundaries identified included the inner limiting membrane, the junction between the inner nuclear layer and outer plexiform layer, and the neural retina-retinal pigment epithelium interface. Using custom MATLAB software, inner and outer retinal thickness profiles were quantified. A paired t test was used to compare the retinal thickness between the ONH eye and the contralateral normal eyes.

RESULTS

Inner retinal thickness of the ONH eye was decreased in all areas of the macula (superior, central, and inferior) compared to the contralateral normal eye (P < 0.05). Outer retinal thicknesses were also decreased in the central and inferior sections compared with the normal eye (P < 0.05).

CONCLUSIONS

Optic nerve hypoplasia is a congenital disease known to result in thinning of the nerve fiber and ganglion cell layer. Our small cohort demonstrated thinning of the inner retinal layers as well as the outer retinal layers in the ONH eye compared with the contralateral normal eye.

The usefulness of multimodal imaging for differentiating pseudopapilloedema and true swelling of the optic nerve head: a review and case series

Ophthalmic practitioners have to make a critical differential diagnosis in cases of an elevated optic nerve head. They have to discriminate between pseudopapilloedema (benign elevation of the optic nerve head) and true swelling of the optic nerve head. This decision has significant implications for appropriate patient management. Assessment of the optic disc prior to the advanced imaging techniques that are available today (particularly spectral domain optical coherence tomography and fundus autofluorescence), has mainly used diagnostic tools, such as funduscopy and retinal photography. As these traditional methods rely on the subjective assessment by the clinician, evaluation of the elevated optic nerve head to differentiate pseudopapilloedema from true swelling of the optic nerve head can be a challenge in clinical practice with patients typically referred for further neuroimaging investigation when the diagnosis is uncertain. The use of multimodal ocular imaging tools such as spectral domain optical coherence tomography, short wavelength fundus autofluorescence and ultrasonography, can potentially aid in the differentiation of pseudopapilloedema from true swelling of the optic nerve head, in conjunction with other clinical findings. By doing so, unnecessary patient costs and anxiety in the case of pseudopapilloedema can be reduced, and appropriate urgent referral and management in the case of true swelling of the optic nerve head can be initiated.

Optic nerve hypoplasia in children and adolescents; prevalence, ocular characteristics and behavioural problems

PURPOSE

To report prevalence, ocular characteristics and coexisting behavioural problems in children and adolescents with optic nerve hypoplasia (ONH), which is a common cause of visual impairment in children in western countries, often associated with neurological or endocrinological problems and where autism has been reported in severe cases with blindness.

METHODS

This is a population-based cross-sectional study of patients <20 years of age who had been diagnosed with ONH and lived in the county of Stockholm in December 2009. Ophthalmological assessments including fundus photographs with optic disc analyses were made. A questionnaire was used to screen for behaviour and development.

RESULTS

The prevalence of ONH in all living children <18 years of age in Stockholm was 17.3/100 000 with a prevalence of visual impairment (<0.3) of 3.9/100 000. In total, 66 patients, median age 9.3 years (0.6-19.4), 36 with bilateral and 30 with unilateral ONH, were included in the current study; 53 were re-examined clinically, group A, and 13 agreed to retrospective analyses of existing medical records, group B. Analyses of the optic discs were made in fundus photographs from 53 patients comparing a semi-automated (Retinal Size Tool) and a manual method (Zeki). There was a strong curvilinear correlation (r(S)  = -0.91 p < 0.0001 for both eyes). Behavioural problems were more common (p < 0.05) in bilateral ONH.

CONCLUSION

Optic nerve hypoplasia is a common ocular malformation with a prevalence of 17.3/100 000 children and adolescents <18 years of age in Stockholm. Unilateral ONH seems as common as bilateral.

Optic nerve hypoplasia

Optic nerve hypoplasia (ONH) is a congenital anomaly of the optic disc that might result in moderate to severe vision loss in children. With a vast number of cases now being reported, the rarity of ONH is obviously now refuted. The major aspects of ophthalmic evaluation of an infant with possible ONH are visual assessment, fundus examination, and visual electrophysiology. Characteristically, the disc is small, there is a peripapillary double-ring sign, vascular tortuosity, and thinning of the nerve fiber layer. A patient with ONH should be assessed for presence of neurologic, radiologic, and endocrine associations. There may be maternal associations like premature births, fetal alcohol syndrome, maternal diabetes. Systemic associations in the child include endocrine abnormalities, developmental delay, cerebral palsy, and seizures. Besides the hypoplastic optic nerve and chiasm, neuroimaging shows abnormalities in ventricles or white- or gray-matter development, septo-optic dysplasia, hydrocephalus, and corpus callosum abnormalities. There is a greater incidence of clinical neurologic abnormalities in patients with bilateral ONH (65%) than patients with unilateral ONH. We present a review on the available literature on the same to urge caution in our clinical practice when dealing with patients with ONH. Fundus photography, ocular coherence tomography, visual field testing, color vision evaluation, neuroimaging, endocrinology consultation with or without genetic testing are helpful in the diagnosis and management of ONH. (Method of search: MEDLINE, PUBMED).

The optic nerve head in congenital fibrosis of the extraocular muscles

OBJECTIVE

Optic nerve head abnormalities have been reported in some patients with congenital fibrosis of the extraocular muscles (CFEOM). This study prospectively assesses optic nerve head appearance in a consecutive CFEOM cohort.

METHODS

All patients with CFEOM referred between 2006 and 2010 and who were mature enough to cooperate with fundus photography were included. Fundus photographs were reviewed with attention to optic nerve head features (eg, cupping >0.6, asymmetric cupping >0.3, optic nerve hypoplasia). Interested participants had CFEOM candidate gene analysis (KIF21A, TUBB3, PHOX2A) for genetic counseling purposes.

RESULTS

Ten CFEOM patients (five CFEOM1, five CFEOM3, age range 5-23 years) from eight families (all consanguineous but one) participated. All 10 patients had notable disc excavation (5) or optic nerve hypoplasia (5). CFEOM candidate gene analysis was performed in all patients and revealed a heterozygous p.R954W KIF21A mutation only in the patient who was not from a consanguineous family.

CONCLUSIONS

Our observations suggest the optic nerve head can be affected by the orbital dysinnervation that occurs in CFEOM. Because careful clinical optic nerve head assessment is difficult in young patients with CFEOM and associated large angle incomitant strabismus, optic nerve head abnormalities may be under-diagnosed. The absence of mutations in known CFEOM genes in our cohort of consanguineous families suggests further genetic heterogeneity of this group of conditions.

Clinical distinction between nasal optic disc hypoplasia (NOH) and glaucoma with NOH-like temporal visual field defects

Purpose:

To report on the clinically important differences between nasal optic hypoplasia (NOH) and glaucoma with NOH-like temporal visual field defect (VFD).

Method:

Five NOH (four bilateral and one unilateral) patients, three unilateral NOH patients with glaucoma, and two glaucoma patients with NOH-like temporal VFD were clinically characterized. Superior segmental optic nerve hypoplasia was also associated with glaucoma in one eye of a bilateral NOH case and the NOH eye of a unilateral NOH patient. Ocular manifestations including refractive errors, size, and appearances of the optic discs, retinal nerve fiber thickness (NFLT) ascertained by optical coherence tomography (OCT), and VFD were examined.

Results:

Ophthalmic examinations revealing NOH showed high myopia at more than −5.0D, a small disc with nasal double-ring appearance, significantly decreased NFLT by OCT, and retinal nerve fiber layer defect in the corresponding nasal sector. Stationary temporal VFD varied from a slight depression of the peripheral isopters to wide sector defects. In contrast, two glaucoma patients with NOH-like temporal VFD showed several different clinical features, including mild myopia less than −5D, a normal size with glaucomatous disc cupping; a slight decrease in nasal NFLT and progression of temporal and other glaucomatous VFD.

Conclusion:

Careful evaluation of optic disc appearance and measurement of NFLT using OCT may help to distinguish between NOH and glaucoma with NOH-like temporal VFD.

Birth weight deviation and early postnatal growth are related to optic nerve morphology at school age in children born preterm

The aim of this study was to evaluate the influence of early and later postnatal growth variables on optic disc morphology in children (n = 53) born at gestational age <32 wk. On fundus photographs taken at a median age of 5.4 y, the optic discs were evaluated using digital image analysis and compared with those of a control group (n = 203). The results were analyzed in relation to gestational age, birth weight (BW) SD score (SDS), IGF-1 weight at postmenstrual age 32 wk (SDS), and weight, length, and head circumference (SDS) at follow-up. The preterm children's optic disc and neuronal rim areas were smaller than in the control group. Low BW (SDS) and weight at wk 32 (SDS) were associated with larger area of the optic cup and reduced neuronal rim area. Preterm children with known brain lesions (n = 6) had significantly larger cups than preterm children without known brain lesions. The association found between both low BW and poor early growth and later reduced neuronal tissue of the optic nerve indicate that early weight gain is important for neural development in preterm children.

Pseudo-Foster Kennedy Syndrome due to unilateral optic nerve hypoplasia: a case report

INTRODUCTION

Pseudo-Foster Kennedy Syndrome is described as unilateral optic disc swelling with contralateral optic atrophy in the absence of an intracranial mass causing compression of the optic nerve. This occurs typically due to bilateral sequential optic neuritis or ischaemic optic neuropathy.

CASE PRESENTATION

We describe a case of pseudo-Foster Kennedy Syndrome in a two year old boy with unilateral papilloedema due to a congenital optic disc anomaly in one eye preventing transmission of raised intracranial pressure to the optic nerve.

CONCLUSION

From our findings we conclude that congenital optic nerve hypoplasia is a cause of pseudo-Foster Kennedy Syndrome.

Developmental abnormalities of the optic nerve and chiasm

Developmental anomalies of the optic nerve are an important and growing cause of lifelong visual handicap and they are often associated with systemic abnormalities. This review focuses on the ocular and systemic aspects of developmental anomalies arising from defects of fetal fissure closure and retinal ganglion cell development, and covers some other optic-disc anomalies that have systemic significance.

Association of optic nerve hypoplasia with mitochondrial cytopathies

Ocular complications are common in the mitochondrial cytopathies and include optic atrophy and retinal degeneration. We retrospectively reviewed 80 patients with nonsyndromic mitochondrial cytopathies (ie, not Kearns-Sayre syndrome, myoclonus epilepsy associated with ragged red fibers [MERRF], mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes [MELAS], neuropathy ataxia and retinitis pigmentosa, Leigh disease, maternally inherited diabetes and deafness, and myoneurogastrointestinal disorder and encephalopathy) and found 10 cases of optic nerve hypoplasia. Optic nerve hypoplasia occurs in at least 12% of patients with nonsyndromic mitochondrial cytopathies. Although the exact pathogenesis of optic nerve hypoplasia in the context of mitochondrial cytopathy is unknown, we postulate that it is the result of excessive apoptosis during embryonic ganglion cell and/or axonal development from abnormal mitochondrial function and cellular energy metabolism.

RetCam image analysis of optic disc morphology in premature infants and its relation to ischaemic brain injury

AIMS

To assess optic disc characteristics in premature infants with and without ischaemic brain injury and to evaluate the role of optic disc morphology in dating the injury.

METHODS

RetCam fundal images, cranial ultrasounds and magnetic resonance imaging (MRI) of 109 premature infants were analysed. The study cohort was divided into subgroups depending on the presence or absence of periventricular leucomalacia (PVL) and intraventricular haemorrhage (IVH). The control group consisted of infants with normal neuroimaging at term and 2 years of age. Using the image analysis software of the RetCam, optic disc diameter (ODD), optic disc area (ODA), and optic cup area (OCA) were measured at 33-34 weeks gestational age. As serial cranial ultrasonography had been performed, it was possible to date the brain injury in those infants with periventricular white matter (PVWM) damage.

RESULTS

Although there was a trend towards reducing ODD, ODA, and OCA with increasing severity of IVH, only the IVH 4 group differed significantly from the controls for these parameters (p = 0.002, p = 0.02, and p = 0.04, respectively). 44.4% of infants with grade 4 IVH had small discs. Only one patient had a large cup in a normal sized disc; this patient had IVH 4. In patients with PVWM damage, the median time of insult was 27 weeks in those with small discs and 28 weeks in those with normal discs. This difference was not significant (p = 0.23).

CONCLUSIONS

Premature infants with IVH 4 have an increased incidence of optic nerve hypoplasia. We found no association between disc morphology and timing of brain injury.

Cognitive and behavioural characteristics in blind children with bilateral optic nerve hypoplasia

AIM

To describe cognitive and behavioural characteristics in a group of blind children with bilateral optic nerve hypoplasia (ONH).

METHODS

Data from records, parents, teachers, and repeated developmental assessments of 13 blind children with ONH born in 1988-1998 were analysed. All children had neuroimaging and/or hormonal evidence of midline malformations. They were all blind and able to communicate with speech.

RESULTS

Severe mood swings and temper tantrums were common, especially during the first years of life. Later in life, sluggish tempo, low frustration tolerance and a narrow range of interests were common. Autism had been diagnosed in 6/13 children, autistic-like condition (ALC) was found in another three. The behaviour of the remaining four children was not within the autism spectrum. Eight children had cognitive capacities within the normal or near-normal range; five had mental retardation. Autism/ALC was found in all cognitive subgroups. All children exhibited fluent speech and, of these, 12 had started to talk at the expected age, but had clear deficiencies in communicative ability.

CONCLUSION

These children had a common pattern of behavioural characteristics including autism spectrum disorders independent of intellectual capacities.

Optic nerve axons: life and death before birth

In the 2004 Bowman Lecture, I give a panegyric for Sir William Bowman, an estimate of the importance and the epidemiology of anterior visual pathway developmental disorders, followed by a history of the anterior visual system. I review the normal development of the optic nerve and chiasm and the main developmental disorders: Optic Nerve Aplasia, Optic Nerve Hypoplasia and Achiasmia.

Optic nerve hypoplasia with intracranial arachnoid cyst

BACKGROUND

The frequent association between optic nerve hypoplasia (ONH) and other central nervous system abnormalities has been widely reported in the literature. Occasional reference has been made to arachnoid cyst as one of the associated findings.

METHOD

The charts and neuroradiologic findings of the 40 patients with ONH seen in our department as well as the Visually Impaired Program during the past 8 years were reviewed.

RESULTS

An intracranial arachnoid cyst was present in 5 of the 40 patients (12.5%) with ONH and visual impairment. These patients' clinical and neuroradiologic findings are reported here.

CONCLUSION

The presence of an intracranial arachnoid cyst in a patient with hypoplastic optic nerves could occur as a coincidental association between these lesions. Alternatively, a common mechanism could give rise to both abnormalities. Three such possibilities-including damage to the developing visual pathway by the arachnoid cyst, absence of an axonal guidance molecule similar to netrin-1 identified in the mouse, or a common genetic mutation involving the myocillin gene causing both abnormalities-are considered.

Septo-optic dysplasia and amniotic bands: Further evidence for a vascular pathogenesis

Septo-optic dysplasia (SOD) is a heterogeneous disorder. While most cases represent an isolated defect, SOD has also been seen in association with mutations in single genes, as a part of multiple congenital anomaly syndromes and with exposure to various teratogens. We report a boy with features of SOD who also has limb defects suggestive of amniotic bands. This case, in addition to others in the literature, provides evidence for a vascular pathogenesis of SOD in some individuals. This hypothesis is also supported by the sporadic occurrence of SOD and its association with decreased maternal age, vascular teratogens, and neuropathologic findings suggestive of vascular insults.

Visually impaired children with posterior ocular malformations: pre- and neonatal data and visual functions

AIM

To analyse pre- and neonatal data and ocular findings in children with visual impairment caused by posterior ocular malformations.

METHODS

Medical records were scrutinized, dried blood spot cards were analysed for virus DNA and ophthalmological assessments were performed in 28 children with optic nerve hypoplasia (ONH) and 10 with optic/chorio-retinal coloboma.

RESULTS

Prenatal exposure to possible teratogens was documented in 5/28, herpes simplex virus type 1 DNA was identified in the dried blood spot cards of 1/26 children and neonatal hypoglycaemia in 12/28 children with ONH. The time delay from ocular to endocrinological diagnosis and treatment was 3 years. Children with ONH and severe visual impairment had endocrinopathy more often (11/13) than ONH children with better visual functions (5/15). Prenatal exposure to teratogens or neonatal hypoglycaemia was not identified in any of the children with coloboma.

CONCLUSION

Neonatal hypoglycaemia was common in children with ONH. Severe visual impairment predicted endocrinopathy. Analysis of dried blood spot cards could serve as an additional diagnostic tool in children with ocular malformations.

Optical coherence tomography of superior segmental optic hypoplasia

AIM

To describe optical coherence tomography (OCT) images of superior segmental optic hypoplasia (SSOH).

METHODS

Five patients (two men and three women, ages 10-45 years) presented with ophthalmoscopic features and visual field defects of SSOH. All affected eyes had good visual acuity and inferior altitudinal or inferonasal visual field loss. The mothers of three patients had type 1 diabetes mellitus. OCT (Humphrey Instrument, CA, USA) was used to evaluate tomographically the optic disc and peripapillary retina of both eyes of each patient. Control data on retinal nerve fibre layer (RNFL) thickness were obtained from 13 normal eyes, one eye each from 13 normal subjects.

RESULTS

Seven of 10 eyes in patients had SSOH. Scans in the vertical meridian through the affected optic discs showed a superior defect of the optic disc associated with decreased RNFL thickness and, in some cases, an abnormal extension of a complex of retinal pigment epithelium and choroid over the edge of the lamina cribrosa. Circular scans around the seven optic discs revealed various decreases of peripapillary RNFL thickness in the superior quadrants. Vertical scans through the fovea also showed superior thinning of RNFL. Quantitative assessment of the peripapillary RNFL thickness revealed significantly decreased values in the superior quadrants compared to normal eyes.

CONCLUSIONS

OCT provides a new tool for quantitative evaluation of optic nerve hypoplasia as exemplified in this study of SSOH. It can reveal minimal degrees of segmental hypoplasia previously undetected.

Endocrinopathies associated with midline cerebral and cranial malformations

We systematically reviewed a series of patients (n = 85) with midline cerebral and cranial malformations to correlate the endocrinopathy with the neuroanatomic defect. Midline cleft lip and palate was associated not only with growth hormone deficiency (GHD) but also with diabetes insipidus (DI); holoprosencephaly and optic nerve hypoplasia with absence of the septum pellucidum had a similar incidence of GHD and DI. Optic nerve hypoplasia with absence of the septum pellucidum had the highest incidence of multiple pituitary endocrinopathies and of neonatal hypoglycaemia. Unilateral, although more commonly bilateral, optic nerve hypoplasia was associated with GHD.

Periventricular leukomalacia: an important cause of visual and ocular motility dysfunction in children

The immature visual system in infants born preterm is vulnerable to adverse events during the perinatal period. Periventricular leukomalacia affecting the optic radiation has now become the principal cause of visual impairment and dysfunction in children born prematurely. Visual dysfunction is characterized by delayed visual maturation, subnormal visual acuity, crowding, visual field defects, and visual perceptual-cognitive problems. Magnetic resonance imaging is the method of choice for diagnosing this brain lesion, which is associated with optic disk abnormalities, strabismus, nystagmus, and deficient visually guided eye movements. Children with periventricular leukomalacia may present to the ophthalmologist within a clinical spectrum from severe cerebral visual impairment in combination with cerebral palsy and mental retardation to only early-onset esotropia, normal intellectual level, and no cerebral palsy. Optimal educational and habilitational strategies need to be developed to meet the needs of this group of visually impaired children.

The normal optic nerve head

BACKGROUND

The normal optic nerve head varies from one person to another, and there is often intraindividual variation as well. Factors such as race and age play an important role in distinguishing what may be considered normal variations in optic nerve head appearance.

METHODS

A literature search and review of the latest studies on the optic nerve head was conducted.

RESULTS

Results of recent studies showed that variations in the average cup-to-disc ratio exist for different races, and with age there is a gradual loss of nerve fibers leading to an overall increase in the cup-to-disc ratio. There is also evidence that congenitally larger optic nerves have larger cup-to-disc ratios and more nerve fibers. Smaller optic nerves, in contrast, have smaller cup-to-disc ratios and fewer nerve fibers. These findings are presented along with sample photographs depicting the normal variations in optic nerve head appearance.

CONCLUSION

Over the past 30 years, technology has allowed for changing views about what may be considered normal in reference to the optic nerve head. This information is valuable to the eye care practitioner in helping to make appropriate patient care management decisions.

Ocular fundus abnormalities in children born before 29 weeks of gestation: a population-based study

PURPOSE

Preterm birth has been found to be associated with increased morbidity of the central nervous and vascular tissues. To investigate the influence of preterm birth on the optic disc and retinal vessels, we examined the ocular fundus in school-aged children born very preterm.

METHODS

A prospective, population-based study was performed in 50 very preterm children (median age 7 years, range 5-9 years) with a median gestational age at birth of 27 weeks (range 24-28 weeks) and a median birth weight of 1055 g (range 450-1520 g). The ocular fundus was examined by ophthalmoscopy in 50 children, and the optic nerve and retinal vessel morphology was evaluated by digital image analysis of ocular fundus photographs in 45 of these children.

RESULTS

The median optic disc area was significantly smaller (p = 0.0002) in the preterm children compared with a reference group. There was no difference in cup area and, consequently, the rim area was significantly smaller (p = 0.0002) in the preterm children. Children with early signs of brain lesions commonly had a rim area below the median of the reference group. Preterm children also commonly had an abnormal retinal vascular pattern that was independent of a previous history of retinopathy of prematurity.

CONCLUSION

Very preterm birth was associated with subnormal optic disc and rim areas and an abnormal vascular pattern. The findings clearly demonstrate the effect of preterm birth on the development of these structures. The long term clinical prognosis of these findings has yet to be determined.

The bst locus on mouse chromosome 16 is associated with age-related subretinal neovascularization

Ocular neovascularization is the leading cause of blindness in developed countries and often causes rapid loss of vision in age-related macular degeneration. Acute visual loss is most often due to hemorrhage from new vessels that have extended from the choroid into the subretinal space. Growth of abnormal vessels beneath the retina in this condition is known as subretinal neovascularization (SRN). Age-related animal models of macular degeneration and SRN have not been described. Current animal models of SRN depend on chemical or physical stimuli to initiate growth of subretinal vessels. The genes responsible for age-related human macular degeneration with SRN have not been firmly identified. We report an angiogenic phenotype in Bst/+ mice that is age-related, clinically evident, and resembles human SRN. This represents a spontaneous, genetically determined model of SRN. Bst/+ mice offer the possibility of exploring the molecular mechanisms of SRN without the need for exogenous agents.

The clinical and morphologic spectrum of optic nerve hypoplasia

PURPOSE

The purpose of this study was to characterize the clinical and morphologic spectrum of all children referred for optic nerve hypoplasia to a tertiary referral hospital in Sweden during a 9-year period.

SUBJECTS AND METHODS

A retrospective review was undertaken of the charts of 117 children (age range, 0.25-16 years), treated at the Children's Hospital, Göteberg between 1988 and 1996, after the diagnosis of optic nerve hypoplasia. Ocular fundus morphologic condition was evaluated by digital image analysis of fundus photographs in 50 children, and neuroimaging was performed in 57 children.

RESULTS

Of the 117 children with optic nerve hypoplasia, 66 (56%) were boys and 51 (44%) were girls. Preterm birth occurred in 24 (20%), and 14 (12%) were born small for gestational age. Additional diagnoses, such as fetal alcohol syndrome, septo-optic dysplasia, perinatal adverse events, and neuropsychiatric disorders, were made in 88%; 7% had unilateral optic nerve hypoplasia. Most of the children had small optic disc, cup, and neuroretinal rim areas, as well as retinal vascular abnormalities; 75% were visually impaired, and a high incidence of nystagmus and strabismus was found among these children.

CONCLUSION

This study indicates that optic nerve hypoplasia has a wide clinical and morphologic spectrum and is associated with a broad range of disorders of the central nervous system. It is suggested that differences in the etiology and timing of the lesion as well as associated lesions may explain this spectrum of optic nerve hypoplasia in children.

Diagnostic value of magnetic resonance imaging and planimetric measurement of optic disc size in confirming optic nerve hypoplasia

PURPOSE

This study set out to evaluate magnetic resonance imaging (MRI) and measurement of optic disc size as diagnostic tools for confirming the diagnosis of optic nerve hypoplasia (ONH) in children with impaired growth.

METHODS

MRI was performed to study the size of the intracranial visual pathways, and image analysis measurements of fundus photographs were performed to determine the size of the optic disc. Results from these investigations were compared with those using the gold standard for diagnosis of ONH, which was the clinical eye examination (visual function, ophthalmoscopic signs, or both). Forty children (median age, 9 years; range, 3 to 19 years) with impaired growth were included in the study.

RESULTS

The prevalence of ONH among the children was 15%. MRI classification of the visual pathways had a higher positive predictive value than image analysis measurement of the optic disc size (1.0 vs 0.6).

CONCLUSIONS

MRI is a good tool for confirming the diagnosis of ONH and may thus facilitate early detection. On the other hand, a small optic disc per se is not a definite indicator of ONH but should encourage further investigation with MRI, especially if there is a clinical suspicion of ONH.

Fundus morphology assessed by digital image analysis in children with fetal alcohol syndrome

BACKGROUND

Fetal alcohol syndrome (FAS) is associated with anomalies of the eye ground. The aim of this study was to evaluate the development of fundus morphology in children with FAS from early childhood to adolescence.

METHODS

Funds photographs were evaluated by digital image analysis in 16 children with FAS. Age at the baseline study was between 0.25 and 14 years, and the median follow-up period was 7 years (range: 0.5 to 12). Sixteen sex- and age-matched healthy children were used as controls.

RESULTS

Children with FAS had a smaller optic disc area, lower frequency of excavations, greater tortuosity of retinal vessels, and a smaller number of vascular branching points compared with the controls. There were no significant differences in the funds abnormalities between the first and last examinations.

CONCLUSION

No interval change of retinal funds morphology was found at follow up, suggesting that the ocular abnormalities associated with FAS remain unchanged during childhood.

Clinical assessment, optic disk measurements, and visual-evoked potential in optic nerve hypoplasia

PURPOSE

Because there is a broad spectrum of visual dysfunction in eyes with optic nerve hypoplasia, we determined whether any clinical observations, including optic disk measurements, could predict visual outcome in eyes with hypoplastic optic nerves.

METHODS

We prospectively studied the eyes of 19 children (eight consecutive and 11 randomly selected), ages 7 to 92 months, in whom a diagnosis of optic nerve hypoplasia was made by an ophthalmologist. Clinical assessment included visual acuity, pupillary responses, and nystagmus. The ratio of the horizontal disk diameter to the disk-macula distance was calculated from fundus photographs. The amplitude and latency of the flash visual-evoked potential as well as the threshold response to pattern reversal checks were recorded.

RESULTS

Visual acuity was associated with pupil reactivity, nystagmus, the ratio of the horizontal disk diameter to the disk-macula distance, pattern visual-evoked potential threshold, and flash visual-evoked potential amplitude (P < .001 for all parameters). All eyes with a ratio of the horizontal disk diameter to the disk-macula distance greater than .30 had good visual acuity, and all eyes with a ratio of the horizontal disk diameter to the disk-macula distance less than .30 had poor visual acuity. No eye with a ratio of the horizontal disk diameter to the disk-macula distance less than or equal to .15 had visual acuity better than light perception.

CONCLUSIONS

Visual-evoked potential and photogrammetric measurement of relative disk size can be used to approximate visual acuity in eyes with optic nerve hypoplasia. This finding could lead to a diagnostic criterion or a severity classification for optic nerve hypoplasia.

Congenital optic disk anomalies

Over the past decade, a wealth of information has accumulated pertaining to the diagnosis and management of patients with congenital optic disk anomalies. As new examples of each entity have been detailed, the diagnostic criteria for each anomaly have become more clearly defined. The advent of sophisticated noninvasive neuroimaging techniques has further refined our ability to accurately detect and categorize the associated CNS anomalies that complicate many of these conditions. In light of recent findings, this review will critically examine many of the well-entrenched concepts pertaining to the diagnosis, evaluation, and treatment of patients with congenital optic disk anomalies. In so doing, it will attempt to dispel some longstanding misconceptions that pervade the literature and obscure our understanding of the pathogenesis, neuroradiological associations, and systemic implications of each anomaly.

Optic nerve hypoplasia: comparative effects in children and rats exposed to alcohol during pregnancy

Children with the fetal alcohol syndrome often have ocular anomalies. These include abnormalities of the eyes and adnexa (strabismus, blepharoptosis, epicanthus), as well as intraocular defects (cataract, glaucoma, persistent hyperplastic primary vitreous, retinal and optic nerve anomalies). Based on the clinical results in an ophthalmological study of a group of Swedish children with the fetal alcohol syndrome, in which optic nerve hypoplasia was found in up to one-half of the group, an experimental study was designed in rats pre- and perinatally exposed to alcohol by means of a liquid diet. The optic nerve was seriously affected. Macroglial cells and optic axons were ultrastructurally damaged. The diameter of the optic nerve cross section, glial cell nuclear area, axonal diameter, and the total number of optic axons showed significantly lower values in the alcohol-exposed group than in the controls. In addition, the retina from the alcohol-exposed animals displayed significantly lower values of the retinal thickness and ganglion cell nuclear volume, as compared to the controls. Thus, rats exposed to alcohol in utero developed hypoplasia of the optic nerve similar to the findings in children born to alcoholic mothers. This strongly supports the hypothesis that prenatal alcohol exposure may adversely affect the development of the optic nerve.