Optic disc morphology of patients with OPA1 autosomal dominant optic atrophy

Comparison of the clinical and genetic features of autosomal dominant optic atrophy and normal tension glaucoma in young Chinese adults

BACKGROUND/OBJECTIVES

To compare the clinical and optical coherence tomography (OCT) characteristics of autosomal dominant optic atrophy (ADOA) and normal tension glaucoma (NTG) in Chinese patients.

SUBJECTS/METHODS

Twenty-four unrelated patients with ADOA and 21 unrelated patients with NTG, younger than 30 years, were enrolled in this study. Data regarding the demographic and clinical characteristics of the patients were collected, and their peripapillary retinal nerve fibre layer (RNFL) and macular ganglion cell complex (GCC) thicknesses were evaluated using OCT. Sequencing of genes associated with neuro-ophthalmic disorders was performed for all patients.

RESULTS

The average age at onset of the ADOA group (13.92 ± 10.73 years) was significantly younger than that of the NTG group (23.67 ± 4.98 years, P = 0.002). Best-corrected visual acuity was significantly poorer in the ADOA group (0.75 ± 0.32) than in the NTG group (0.16 ± 0.19, P < 0.001). The average peripapillary RNFL thickness and the RNFL thicknesses in the temporal upper, temporal lower, and nasal lower sectors were significantly thinner in the ADOA group than in the NTG group (all P < 0.05). Moreover, the macular GCC thickness of the ADOA group was significantly thinner than that of the NTG group (P < 0.001). Twenty-three OPA1 variants (11 novel OPA1 variants) and one OPA3 variant were detected in 24 patients with ADOA.

CONCLUSIONS

Our study revealed a distinct difference between the patterns of RNFL and GCC loss in ADOA and NTG, which will help to differentiate ADOA from NTG in young patients. Additionally, this study expanded the genetic spectrum of ADOA.

Ocular Manifestations in Patients with Sensorineural Hearing Loss

Identification of ocular manifestations in patients with sensorineural hearing loss (SNHL) can have a large impact on the outcome and treatment of pediatric patients. Due to the common co-incidence of ocular manifestations and SNHL in children, both ophthalmologic and hearing loss screening and routine examinations must be conducted to minimize adverse outcomes and worsening of pathology. Early evaluation and diagnosis is imperative for intervention and further development of the patient. Co-incidence requires a thorough evaluation that includes a comprehensive history, examination, and diagnostic testing. In this article, a literature review was conducted to analyze the presentations of various diseases and syndromes, such as Alport Syndrome, Waardenburg Syndrome, Norrie Disease, Usher Disease, Stickler Syndrome, Marfan Syndrome, Congenital Rubella, and Hereditary Optic Neuropathies. We divided the various ocular pathologies into anterior and posterior segment presentations and associated systemic findings for better understanding. Additionally, this review aims to include an update on the management of patients with both ocular and hearing loss manifestations.

Incidence of non-glaucomatous ocular disease in patients with asymmetric optic disc cupping

PURPOSE

To evaluate the incidence of non-glaucomatous ocular disease in patients with asymmetric optic disc cupping.

METHODS

A retrospective case series, including consecutive patients with cup-to-disc ratio (CDR) asymmetry greater than 0.2. All patients underwent a complete neuro-ophthalmological examination, automated perimetry with the Humphrey 24-2 visual fields program. Retinal nerve fibre layer thickness was measured by optical coherence tomography (OCT). The results of neuroimaging, macular OCT and blood tests were recorded as well. Patients were assigned a diagnosis of glaucomatous optic neuropathy (GON) or non-glaucomatous disease (NGD). The main outcome measure was the rate of non-glaucomatous ocular disease.

RESULTS

A total of 120 (67 males) patients with a mean age of 71.1 ± 12.5 years met the inclusion criteria and were included in this study. The mean asymmetry in CDR between the eyes was 0.3 ± 0.13 (range, 0.2-0.9). Twenty patients (16.6%) had a visual field defect not typical for glaucoma and positive relative afferent pupillary defect was found in 24 patients (20%). Six patients were found to have newly diagnosed non-glaucomatous ocular disease: maculopathy in three patients, retinopathy in one patient and traumatic optic neuropathy in two patients. Patients with NGD were significantly younger than the patients with GON (59.8 ± 23.3 vs. 71.3 ± 11.5 years, P = 0.001). Optic disc pallor was found in 4/93 patients with glaucoma compared to 3/6 with newly diagnosed non-glaucomatous disease (4.7% vs. 50.0%, P = 0.03).

CONCLUSIONS

Asymmetric optic disc cupping can be associated with non-glaucomatous disease and may warrant neuro-ophthalmological evaluation, especially in younger patients or those with optic disc pallor.

Comparison of Lamina Cribrosa Morphology in Normal Tension Glaucoma and Autosomal-Dominant Optic Atrophy

Purpose

To compare lamina cribrosa (LC) morphology in patients with normal tension glaucoma (NTG) and autosomal-dominant optic atrophy (ADOA).

Methods

This cross-sectional study matched 24 patients diagnosed with ADOA (24 eyes) by age and retinal nerve fiber layer thickness with 48 patients diagnosed with NTG (48 eyes) by age with 48 healthy controls (48 eyes). Optic nerve heads were scanned by enhanced-depth imaging (EDI) optical coherence tomography (OCT). The LC curvature index (LCCI) and LC depth (LCD) on B-scan images obtained using EDI-OCT were measured at seven locations spaced equidistantly across the vertical optic disc diameter and compared among the NTG, ADOA, and control groups.

Results

Mean LCCI and LCD were significantly greater in NTG than in ADOA and healthy eyes (P < 0.001 each) but did not differ significantly in ADOA and healthy eyes.

Conclusions

NTG eyes have a more posteriorly curved and deeper LC than ADOA and healthy eyes. This finding provides insight into the role of LC morphology in NTG and provides a clinical clue to distinguish between NTG and ADOA.

Citicoline and Retinal Ganglion Cells: Effects on Morphology and Function

BACKGROUND

Retinal ganglion cells (RGCs) are the nervous retinal elements which connect the visual receptors to the brain forming the nervous visual system. Functional and/or morphological involvement of RGCs occurs in several ocular and neurological disorders and therefore these cells are targeted in neuroprotective strategies. Cytidine 5-diphosphocholine or Citicoline is an endogenous compound that acts in the biosynthesis of phospholipids of cell membranes and increases neurotransmitters' levels in the Central Nervous System. Experimental studies suggested the neuromodulator effect and the protective role of Citicoline on RGCs. This review aims to present evidence of the effects of Citicoline in experimental models of RGCs degeneration and in human neurodegenerative disorders involving RGCs.

METHODS

All published papers containing experimental or clinical studies about the effects of Citicoline on RGCs morphology and function were reviewed.

RESULTS

In rodent retinal cultures and animal models, Citicoline induces antiapoptotic effects, increases the dopamine retinal level, and counteracts retinal nerve fibers layer thinning. Human studies in neurodegenerative visual pathologies such as glaucoma or non-arteritic ischemic neuropathy showed a reduction of the RGCs impairment after Citicoline administration. By reducing the RGCs' dysfunction, a better neural conduction along the post-retinal visual pathways with an improvement of the visual field defects was observed.

CONCLUSION

Citicoline, with a solid history of experimental and clinical studies, could be considered a very promising molecule for neuroprotective strategies in those pathologies (i.e. Glaucoma) in which morpho-functional changes of RGCc occurs.

Mgm1 is required for maintenance of mitochondrial function and virulence in Candida albicans

Mitochondria are dynamic organelles, and their shapes and sizes are regulated by mitochondrial fusion and fission. The proteins essential for mitochondrial fusion in Candida albicans have not been clearly characterized. In this study, Mgm1 was explored for its roles in mitochondrial function, cell cycle, hyphal growth and virulence in this pathogen. The deletion of MGM1 led to mitochondrial fragmentation and mtDNA loss and activated the checkpoint pathway to arrest the cell cycle in G1 phase. Moreover, loss of MGM1 led to defects in hyphal development and attenuation of virulence in a macrophage cell line and a mouse model of disseminated infection. These results reveal that Mgm1 plays an important role in mitochondrial dynamics and function, cell cycle progression, hyphal development and virulence in C. albicans.

Clinical and genetic features of eight Chinese autosomal-dominant optic atrophy pedigrees with six novel OPA1 pathogenic variants

BACKGROUND

Autosomal-dominant optic atrophy (ADOA) is one of the most common types of inherited optic atrophy. We identify OPA1 pathogenic variants and assess the clinical features of a cohort of Chinese ADOA patients Materials and Methods: Detailed clinical evaluations were performed and genomic DNA was extracted from peripheral blood for all the participants. Sanger sequencing was used to analyze all exons and exon/intron junctions of OPA1 for eight pedigrees. Target exome capture plus next-generation sequencing (NGS) were applied for one atypical family with photophobia. Reverse transcription polymerase chain reaction was carried out to further characterize the mRNA change of selected splicing alteration.

RESULTS

All 17 patients had impaired vision and optic-disk pallor; however, the clinical severity varied markedly. Two patients complicated with hearing loss. Six novel and two reported pathogenic variants in OPA1 (GenBank Accession No. NM_130837.2) were identified including four nonsynonymous variants (c.2400T > G, c.1468T > C, c.1567A > G and c.1466T > C), two splicing variants (c.2984-1_2986delGAGA and c.2983 + 5G > A), one small deletion (c.2960_2968delGCGTTCAAC), and one small insertion (c.3009_3010insA). RNA analysis revealed the splicing variant c.2984-1_2986delGAGA caused small deletion of mRNA (r.2983_2988del).

CONCLUSIONS

ADOA patients presented variable clinical manifestations. Novel OPA1 pathogenic variants are the main genetic defect for Chinese ADOA cases. NGS may be a useful molecular testing tool for atypical ADOA.

Genes and genetics in eye diseases: a genomic medicine approach for investigating hereditary and inflammatory ocular disorders

Past 25y have witnessed an exponential increase in knowledge and understanding of ocular diseases and their respective genetic underpinnings. As a result, scientists have mapped many genes and their variants that can influence vision and health of our eyes. Based on these findings, it is becoming clear that an early diagnosis employing genetic testing can help evaluate patients' conditions for instituting treatment plan(s) and follow-up care to avoid vision complications later. For example, knowing family history becomes crucial for inherited eye diseases as it can benefit members in family who may have similar eye diseases or predispositions. Therefore, gathering information from an elaborate examination along with complete assessment of past medical illness by ophthalmologists followed by consultation with geneticists can help create a roadmap for making diagnosis and treatment precise and beneficial. In this review, we present an update on ocular genomic medicine that we believe has tremendous potential towards unraveling genetic implications in ocular diseases and patients' susceptibilities. We also discuss translational aspects of genetic ophthalmology and genome engineering that may help advance molecular diagnostics and therapeutics.

Is Glaucoma a Neurodegeneration caused by Central Insulin Resistance: Diabetes Type 4?

How to cite this article: Dada T. Is Glaucoma a Neurodegeneration caused by Central Insulin Resistance: Diabetes Type 4? J Curr Glaucoma Pract 2017;11(3):77-79.

Mitochondrial dysfunction in ocular disease: Focus on glaucoma

Mitochondrial dysfunction commonly presents with ocular findings as a part of a systemic disorder. These ophthalmic manifestations can be the first sign of a mitochondrial abnormality, which highlights the key role of a comprehensive ophthalmic assessment. On the other hand, a number of visually disabling genetic and acquired eye diseases with no curative treatment show abnormal mitochondrial function. Recent advances in mitochondrial research have improved our understanding of previously unexplained ocular disorders utilising better diagnostic approaches. Further studies on mitochondrial dysfunction and novel modalities of treatment will help to improve outcomes of these conditions. In this review article we discuss the clinical picture of common mitochondrial-related eye diseases, diagnostic approaches and possible treatment options including a very recent interesting report about gene therapy, with a particular focus on glaucoma.

Genetic and Clinical Analyses of DOA and LHON in 304 Chinese Patients with Suspected Childhood-Onset Hereditary Optic Neuropathy

Leber hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA), the most common forms of hereditary optic neuropathy, are easily confused, and it is difficult to distinguish one from the other in the clinic, especially in young children. The present study was designed to survey the mutation spectrum of common pathogenic genes (OPA1, OPA3 and mtDNA genes) and to analyze the genotype-phenotype characteristics of Chinese patients with suspected childhood-onset hereditary optic neuropathy. Genomic DNA and clinical data were collected from 304 unrelated Chinese probands with suspected hereditary optic neuropathy with an age of onset below 14 years. Sanger sequencing was used to screen variants in the coding and adjacent regions of OPA1, OPA3 and the three primary LHON-related mutation sites in mitochondrial DNA (mtDNA) (m.3460G>A, m.11778G>A and m.14484T>C). All patients underwent a complete ophthalmic examination and were compared with age-matched controls. We identified 89/304 (29.3%) primary mtDNA mutations related to LHON in 304 probands, including 76 mutations at m.11778 (76/89, 85.4% of all mtDNA mutations), four at m.3460 (4/89, 4.5%) and nine at m.14484 (9/89, 10.1%). This result was similar to the mutation frequency among Chinese patients with LHON of any age. Screening of OPA1 revealed 23 pathogenic variants, including 11 novel and 12 known pathogenic mutations. This study expanded the OPA1 mutation spectrum, and our results showed that OPA1 mutation is another common cause of childhood-onset hereditary optic neuropathy in Chinese pediatric patients, especially those with disease onset during preschool age.

A novel 3q29 deletion associated with autism, intellectual disability, psychiatric disorders, and obesity

Copy number variation (CNV) has been associated with a variety of neuropsychiatric disorders, including intellectual disability/developmental delay (ID/DD), autism spectrum disorder (ASD), and schizophrenia (SCZ). Often, individuals carrying the same pathogenic CNV display high clinical variability. By array-CGH analysis, we identified a novel familial 3q29 deletion (1.36 Mb), centromeric to the 3q29 deletion region, which manifests with variable expressivity. The deletion was identified in a 3-year-old girl diagnosed with ID/DD and autism and segregated in six family members, all affected by severe psychiatric disorders including schizophrenia, major depression, anxiety disorder, and personality disorder. All individuals carrying the deletion were overweight or obese, and anomalies compatible with optic atrophy were observed in three out of four cases examined. Amongst the 10 genes encompassed by the deletion, the haploinsufficiency of Optic Atrophy 1 (OPA1), associated with autosomal dominant optic atrophy, is likely responsible for the ophthalmological anomalies. We hypothesize that the haploinsufficiency of ATPase type 13A4 (ATP13A4) and/or Hairy/Enhancer of Split Drosophila homolog 1 (HES1) contribute to the neuropsychiatric phenotype, while HES1 deletion might underlie the overweight/obesity. In conclusion, we propose a novel contiguous gene syndrome due to a proximal 3q29 deletion variably associated with autism, ID/DD, psychiatric traits and overweight/obesity.

Expansions of the neurovascular scleral canal and contained optic nerve occur early in the hypertonic saline rat experimental glaucoma model

PURPOSE

To characterize early optic nerve head (ONH) structural change in rat experimental glaucoma (EG).

METHODS

Unilateral intraocular pressure (IOP) elevation was induced in Brown Norway rats by hypertonic saline injection into the episcleral veins and animals were sacrificed 4 weeks later by perfusion fixation. Optic nerve cross-sections were graded from 1 (normal) to 5 (extensive injury) by 5 masked observers. ONHs with peripapillary retina and sclera were embedded, serial sectioned, 3-D reconstructed, delineated, and quantified. Overall and animal-specific EG versus Control eye ONH parameter differences were assessed globally and regionally by linear mixed effect models with significance criteria adjusted for multiple comparisons.

RESULTS

Expansions of the optic nerve and surrounding anterior scleral canal opening achieved statistical significance overall (p < 0.0022), and in 7 of 8 EG eyes (p < 0.005). In at least 5 EG eyes, significant expansions (p < 0.005) in Bruch's membrane opening (BMO) (range 3-10%), the anterior and posterior scleral canal openings (8-21% and 5-21%, respectively), and the optic nerve at the anterior and posterior scleral canal openings (11-30% and 8-41%, respectively) were detected. Optic nerve expansion was greatest within the superior and inferior quadrants. Optic nerve expansion at the posterior scleral canal opening was significantly correlated to optic nerve damage (R = 0.768, p = 0.042).

CONCLUSION

In the rat ONH, the optic nerve and surrounding BMO and neurovascular scleral canal expand early in their response to chronic experimental IOP elevation. These findings provide phenotypic landmarks and imaging targets for detecting the development of experimental glaucomatous optic neuropathy in the rat eye.

Medical management of hereditary optic neuropathies

Hereditary optic neuropathies are diseases affecting the optic nerve. The most common are mitochondrial hereditary optic neuropathies, i.e., the maternally inherited Leber's hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA). They both share a mitochondrial pathogenesis that leads to the selective loss of retinal ganglion cells and axons, in particular of the papillo-macular bundle. Typically, LHON is characterized by an acute/subacute loss of central vision associated with impairment of color vision and swelling of retinal nerve fibers followed by optic atrophy. DOA, instead, is characterized by a childhood-onset and slowly progressive loss of central vision, worsening over the years, leading to optic atrophy. The diagnostic workup includes neuro-ophthalmologic evaluation and genetic testing of the three most common mitochondrial DNA mutations affecting complex I (11778/ND4, 3460/ND1, and 14484/ND6) for LHON and sequencing of the nuclear gene OPA1 for DOA. Therapeutic strategies are still limited including agents that bypass the complex I defect and exert an antioxidant effect (idebenone). Further strategies are aimed at stimulating compensatory mitochondrial biogenesis. Gene therapy is also a promising avenue that still needs to be validated.

Optic nerve gray crescent can confound neuroretinal rim interpretation: review of the literature

The optic nerve gray crescent can be of clinical significance if unrecognized during assessment for glaucoma. It has a characteristic appearance of a slate gray area of pigmentation within the disc margins and commonly appears along the inferotemporal or temporal neuroretinal rim areas. This type of disc rim pigmentation can create the impression of neuroretinal rim thinning, and thus lead to the misdiagnosis of glaucoma or "glaucoma suspect" with attendant implications for overtreatment or unnecessary close monitoring of such patients. The gray crescent is more common in African Americans than whites (prevalence rate 27% vs 7%) and is bilateral in at least 58% of cases. It has been reported in association with Kjer optic atrophy type 1. Suggested causes of the gray crescent include an accumulation of melanocytes, or retinal pigment epithelium cells partially located in the optic nerve head region if Bruch's membrane extends internal to the peripapillary scleral ring. Other causes of pigmentation that may resemble gray crescent are conus pigmentosus and variations of peripapillary atrophy. When a gray crescent is present, clinicians should endeavour to identify the true anatomical disc margins via the scleral lip and, if necessary, evaluate the patient further with imaging and visual field studies.

First report of OPA1 screening in Greek patients with autosomal dominant optic atrophy and identification of a previously undescribed OPA1 mutation

PURPOSE

To describe the genotype-phenotype correlation in four Greek pedigrees with autosomal dominant optic atrophy (ADOA) and OPA1 mutations.

METHODS

Seven patients from four unrelated families (F1, F2, F3, F4) were clinically assessed for visual acuity, color vision, ptosis, afferent pupillary defects, and visual fields and underwent orthoptic assessment, slit-lamp biomicroscopy, and fundus examination to establish their clinical status. Genomic DNA was extracted from peripheral blood samples from all participants. The coding region (exons 1-28), including the intron-exon boundaries of the OPA1 gene, was screened in the probands of the four families, as well as in seven additional family members (four affected and three unaffected) with PCR and direct DNA sequencing.

RESULTS

All patients presented bilateral decrease in best-corrected visual acuity and temporal pallor of the optic disc. The visual fields of the adult patients showed characteristic scotomata. Other signs were present in some patients such as decreased color discrimination and a gray crescent within the neuroretinal rim. After the OPA1 gene was sequenced, a previously undescribed heterozygous splice-site mutation c.784-1G>T in intron 7 was detected in family F2. In families F1, F3, and F4, a previously reported in-frame deletion c.876_878delTGT/p.(Val294del), the frameshift c.2366delA/p.(Asn789Metfs*11), and splice-site c.1140+5G>C mutations were detected, respectively.

CONCLUSIONS

This is the first report of molecular characterization of Greek patients with ADOA. Our findings provide additional information regarding the genotype-phenotype correlation and establish the role of the OPA1 gene in Greek patients with ADOA.

SDOCT thickness measurements of various retinal layers in patients with autosomal dominant optic atrophy due to OPA1 mutations

Purpose. To specify thickness values of various retinal layers on macular spectral domain Optical Coherence Tomography (SDOCT) scans in patients with autosomal dominant optic atrophy (ADOA) compared to healthy controls. Methods. SDOCT volume scans of 7 patients with ADOA (OPA-1 mutation) and 14 healthy controls were quantitatively analyzed using manual grading software. Mean thickness values for the ETDRS grid subfields 5–8 were calculated for the spaces neurosensory retina, retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), a combined space of inner plexiform layer/outer plexiform layer/inner nuclear layer (IPL+INL+OPL), and a combined space of outer nuclear layer/photoreceptor layers (ONL+PL). Results. ADOA patients showed statistically significant lower retinal thickness values than controls (P < 0.01). RNFL (P < 0.001) and GCL thicknesses (P < 0.001) were significantly lower in ADOA patients. There was no difference in IPL+INL+OPL and in ONL+PL thickness. Conclusion. Manual subanalysis of macular SDOCT volume scans allowed detailed subanalysis of various retinal layers. Not only RNFL but also GCL thicknesses are reduced in the macular area of ADOA patients whereas subjacent layers are not involved. Together with clinical findings, macular SDOCT helps to identify patients with suspicion for hereditary optic neuropathy before genetic analysis confirms the diagnosis.

Mutation survey of the optic atrophy 1 gene in 193 Chinese families with suspected hereditary optic neuropathy

PURPOSE

Dominant optic atrophy (DOA) is the most common form of autosomal inherited optic neuropathy, mainly caused by mutations in the optic atrophy 1 (OPA1) gene. The purpose of this study was to detect OPA1 gene mutations and associated phenotypes in Chinese patients with suspected hereditary optic neuropathy.

METHODS

A cohort of 193 Chinese families with suspected hereditary optic neuropathy was collected, which had been excluded from the three common primary mitochondrial DNA mutations associated with Leber hereditary optic neuropathy in our prior screening. Sanger sequencing was used to analyze variants in the coding and adjacent regions of OPA1.

RESULTS

In this study, 11 heterozygous OPA1 mutations, among which eight were novel and three were known, were identified in 12 of the 193 families (6.2%) but in none of the 192 control individuals. These novel mutations consisted of two nonsense mutations (p.E707* and p.K797*), two missense mutations (p.T330S and p.V377I), two deletions (p.S64fs and p.L331fs), one small insertion (p.L17fs), and one splice site mutation (c.2614-2A>G). Of the 12 families, three had a family history of optic neuropathy while nine were sporadic cases. Analysis of the family members in the two sporadic cases demonstrated that one parent in each of the two families had the OPA1 mutation and mild phenotype of optic atrophy. A 4-year-old boy with severe ocular phenotype was found to be compound heterozygous for two OPA1 mutations, a p.S64fs frameshift deletion and a p.V377I missense mutation, possibly implying an additive effect.

CONCLUSIONS

This study implies that the frequency of DOA is much lower than that of Leber hereditary optic neuropathy in Chinese compared with other ethnic groups. Lack of awareness of the mild phenotype of DOA may contribute to the low frequency of OPA1-related DOA in Chinese. The phenotype associated with compound heterozygous OPA1 mutations may suggest a possible addictive effect.

Dominant optic atrophy in Denmark - report of 15 novel mutations in OPA1, using a strategy with a detection rate of 90%

Background

Investigation of the OPA1 mutation spectrum in autosomal dominant optic atrophy (ADOA) in Denmark.

Methods

Index patients from 93 unrelated ADOA families were assessed for a common Danish founder mutation (c.2826_2836delinsGGATGCTCCA) inOPA1. If negative, direct DNA sequencing of the coding sequence and multiplex ligation-dependent probe amplification (MLPA) were performed. Results from MLPA analysis have been previously reported. Haplotype analysis was carried out analysing single nucleotide polymorphisms (SNP). Retrospective clinical data were retrieved from medical files.

Results

Probably causative mutations were identified in 84 out of 93 families (90%) including 15 novel mutations. Three mutations c.983A > G, c.2708_2711delTTAG and c.2826_2836delinsGGATGCTCCA, were responsible for ADOA in10, 11 and 28 families, respectively, corresponding to 11%, 12% and 30%. A common haplotype in nine of ten c.983A > G families suggests that they descend from a single founder. The c.2708_2711delTTAG mutation was present on at least two haplotypes and has been repeatedly reported in various ethnic groups,thus represents a mutational hotspot. Clinical examinations of index patients with the two latter mutations demonstrated large inter- and intra-familial variations apparently.

Conclusions

Genetic testing for OPA1mutations assist in the diagnosis. We have identified mutations in OPA1 in 90% of families including 15 novel mutations. Both DNA sequencing and MLPA analysis are necessary to achieve a high detection rate. More than half of the affected families in Denmark are represented by three common mutations, at least two of which are due to a founder effect, which may account for the high prevalence of ADOA in Denmark.

Dominant optic atrophy

Definition of the disease

Dominant Optic Atrophy (DOA) is a neuro-ophthalmic condition characterized by a bilateral degeneration of the optic nerves, causing insidious visual loss, typically starting during the first decade of life. The disease affects primary the retinal ganglion cells (RGC) and their axons forming the optic nerve, which transfer the visual information from the photoreceptors to the lateral geniculus in the brain.

Epidemiology

The prevalence of the disease varies from 1/10000 in Denmark due to a founder effect, to 1/30000 in the rest of the world.

Clinical description

DOA patients usually suffer of moderate visual loss, associated with central or paracentral visual field deficits and color vision defects. The severity of the disease is highly variable, the visual acuity ranging from normal to legal blindness. The ophthalmic examination discloses on fundoscopy isolated optic disc pallor or atrophy, related to the RGC death. About 20% of DOA patients harbour extraocular multi-systemic features, including neurosensory hearing loss, or less commonly chronic progressive external ophthalmoplegia, myopathy, peripheral neuropathy, multiple sclerosis-like illness, spastic paraplegia or cataracts.

Aetiology

Two genes (OPA1, OPA3) encoding inner mitochondrial membrane proteins and three loci (OPA4, OPA5, OPA8) are currently known for DOA. Additional loci and genes (OPA2, OPA6 and OPA7) are responsible for X-linked or recessive optic atrophy. All OPA genes yet identified encode mitochondrial proteins embedded in the inner membrane and ubiquitously expressed, as are the proteins mutated in the Leber Hereditary Optic Neuropathy. OPA1 mutations affect mitochondrial fusion, energy metabolism, control of apoptosis, calcium clearance and maintenance of mitochondrial genome integrity. OPA3 mutations only affect the energy metabolism and the control of apoptosis.

Diagnosis

Patients are usually diagnosed during their early childhood, because of bilateral, mild, otherwise unexplained visual loss related to optic discs pallor or atrophy, and typically occurring in the context of a family history of DOA. Optical Coherence Tomography further discloses non-specific thinning of retinal nerve fiber layer, but a normal morphology of the photoreceptors layers. Abnormal visual evoked potentials and pattern ERG may also reflect the dysfunction of the RGCs and their axons. Molecular diagnosis is provided by the identification of a mutation in the OPA1 gene (75% of DOA patients) or in the OPA3 gene (1% of patients).

Prognosis

Visual loss in DOA may progress during puberty until adulthood, with very slow subsequent chronic progression in most of the cases. On the opposite, in DOA patients with associated extra-ocular features, the visual loss may be more severe over time.

Management

To date, there is no preventative or curative treatment in DOA; severely visually impaired patients may benefit from low vision aids. Genetic counseling is commonly offered and patients are advised to avoid alcohol and tobacco consumption, as well as the use of medications that may interfere with mitochondrial metabolism. Gene and pharmacological therapies for DOA are currently under investigation.

A biomechanical paradigm for axonal insult within the optic nerve head in aging and glaucoma

This article is dedicated to Rosario Hernandez for her warm support of my own work and her genuine enthusiasm for the work of her colleagues throughout her career. I first met Rosario as a research fellow in Harry Quigley's laboratory between 1991 and 1993. Along with Harry, John Morrison, Elaine Johnson, Abe Clark, Colm O'Brien and many others, Rosario's work has provided lamina cribrosa astrocyte cellular mechanisms that are biomechanically plausible and in so doing provided credibility to early notions of the optic nerve head (ONH) as a biomechanical structure. We owe a large intellectual debt to Rosario for her dogged persistence in the characterization of the ONH astrocyte and lamina cribrosacyte in age and disease. Two questions run through her work and remain of central importance today. First, how do astrocytes respond to and alter the biomechanical environment of the ONH and the physiologic stresses created therein? Second, how do these physiologic demands on the astrocyte influence their ability to deliver the support to retinal ganglion cell axon transport and flow against the translaminar pressure gradient? The purpose of this article is to summarize what is known about the biomechanical determinants of retinal ganglion cell axon physiology within the ONH in the optic neuropathy of aging and Glaucoma. My goal is to provide a biomechanical framework for this discussion. This framework assumes that the ONH astrocytes and glia fundamentally support and influence both the lamina cribrosa extracellular matrix and retinal ganglion cell axon physiology. Rosario Hernandez was one of the first investigators to recognize the implications of this unique circumstance. Many of the ideas contained herein have been initially presented within or derived from her work (Hernandez, M.R., 2000. The optic nerve head in glaucoma: role of astrocytes in tissue remodeling. Prog Retin Eye Res. 19, 297-321.; Hernandez, M.R., Pena, J.D., 1997. The optic nerve head in glaucomatous optic neuropathy. Arch Ophthalmol. 115, 389-395.).

Mitochondrial oxidative phosphorylation compensation may preserve vision in patients with OPA1-linked autosomal dominant optic atrophy

Autosomal Dominant Optic Atrophy (ADOA) is the most common inherited optic atrophy where vision impairment results from specific loss of retinal ganglion cells of the optic nerve. Around 60% of ADOA cases are linked to mutations in the OPA1 gene. OPA1 is a fission-fusion protein involved in mitochondrial inner membrane remodelling. ADOA presents with marked variation in clinical phenotype and varying degrees of vision loss, even among siblings carrying identical mutations in OPA1. To determine whether the degree of vision loss is associated with the level of mitochondrial impairment, we examined mitochondrial function in lymphoblast cell lines obtained from six large Australian OPA1-linked ADOA pedigrees. Comparing patients with severe vision loss (visual acuity [VA]<6/36) and patients with relatively preserved vision (VA>6/9) a clear defect in mitochondrial ATP synthesis and reduced respiration rates were observed in patients with poor vision. In addition, oxidative phosphorylation (OXPHOS) enzymology in ADOA patients with normal vision revealed increased complex II+III activity and levels of complex IV protein. These data suggest that OPA1 deficiency impairs OXPHOS efficiency, but compensation through increases in the distal complexes of the respiratory chain may preserve mitochondrial ATP production in patients who maintain normal vision. Identification of genetic variants that enable this response may provide novel therapeutic insights into OXPHOS compensation for preventing vision loss in optic neuropathies.

Pattern of retinal ganglion cell loss in dominant optic atrophy due to OPA1 mutations

PURPOSE

The majority of patients with autosomal dominant optic atrophy (DOA) harbour pathogenic OPA1 mutations. Although DOA is characterised by the preferential loss of retinal ganglion cells (RGCs), about 20% of patients with OPA1 mutations will develop a more severe disease variant (DOA+), with additional neuromuscular features. In this prospective, observational case series, optical coherence tomography (OCT) was used to define the pattern of retinal nerve fibre layer (RNFL) loss in patients with both the pure and syndromal forms of DOA.

METHODS

Forty patients with a molecular diagnosis of DOA due to OPA1 mutations were prospectively recruited from our neuro-ophthalmology clinic: 26 patients with isolated optic atrophy and 14 patients manifesting DOA+ features. Peripapillary RNFL thickness was measured with the Fast RNFL (3.4) acquisition protocol on a Stratus OCT.

RESULTS

There was a statistically significant reduction in average RNFL thickness in the OPA1 group compared with normal controls (P<0.0001). The percentage decrease was greatest in the temporal quadrant (59.0%), followed by the inferior (49.6%), superior (41.8%), and nasal (25.9%) quadrants. Patients with DOA+ features had worse visual outcomes compared with patients with pure DOA. Except in the temporal quadrant, RNFL measurements were significantly thinner for the DOA+ group. There was an inverse correlation between average RNFL thickness and logarithm of the minimum angle of resolution (LogMAR) visual acuity (P<0.0001).

CONCLUSIONS

RGC loss in DOA is characterised by severe involvement of the temporal papillomacular bundle, with relative sparing of the nasal fibres. RNFL thinning is more pronounced in patients with DOA+ phenotypes.

Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies

Leber hereditary optic neuropathy (LHON) and autosomal-dominant optic atrophy (DOA) are the two most common inherited optic neuropathies in the general population. Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle. Three mitochondrial DNA (mtDNA) point mutations; m.3460G>A, m.11778G>A, and m.14484T>C account for over 90% of LHON cases, and in DOA, the majority of affected families harbour mutations in the OPA1 gene, which codes for a mitochondrial inner membrane protein. Optic nerve degeneration in LHON and DOA is therefore due to disturbed mitochondrial function and a predominantly complex I respiratory chain defect has been identified using both in vitro and in vivo biochemical assays. However, the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa. The downstream consequences of these mitochondrial disturbances are likely to be influenced by the local cellular milieu. The vulnerability of RGCs in LHON and DOA could derive not only from tissue-specific, genetically-determined biological factors, but also from an increased susceptibility to exogenous influences such as light exposure, smoking, and pharmacological agents with putative mitochondrial toxic effects. Our concept of inherited mitochondrial optic neuropathies has evolved over the past decade, with the observation that patients with LHON and DOA can manifest a much broader phenotypic spectrum than pure optic nerve involvement. Interestingly, these phenotypes are sometimes clinically indistinguishable from other neurodegenerative disorders such as Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and multiple sclerosis, where mitochondrial dysfunction is also thought to be an important pathophysiological player. A number of vertebrate and invertebrate disease models has recently been established to circumvent the lack of human tissues, and these have already provided considerable insight by allowing direct RGC experimentation. The ultimate goal is to translate these research advances into clinical practice and new treatment strategies are currently being investigated to improve the visual prognosis for patients with mitochondrial optic neuropathies.

Abnormalities of the optic disc

The optic disc represents the anterior end of the optic nerve, the most forward extension of the central nervous system (CNS). The optic disc gives a rare glimpse into the CNS. Hence, diseases of the CNS are often manifested on fundus examination. Abnormalities of the optic disc may reflect eye disease (such as glaucoma), problems in development (as in various syndromes), or CNS disease (such as increased intracranial pressure). Each optic nerve is composed of about 1.2 million axons deriving from the retinal ganglion cells of one eye. Optic atrophy is a morphological sequela reflecting the loss of many or all of these axons. Myriad diseases such as hereditary, metabolic, tumor, and increased intracranial pressure can lead to optic atrophy. Some diseases, such as optic disc drusen, intracranial masses, orbital tumors, ischemic optic neuropathies, inflammations, and infiltrations, can produce optic disc edema before leading to optic atrophy. A number of new imaging modalities, such as optical coherence tomography (OCT), quantitate the thickness of the peripapillary retinal nerve fiber layer as an indirect measure of axonal loss or swelling. OCT can therefore be used to quantitate pathology or the response to therapy in various generalized CNS conditions, such as multiple sclerosis.

Optic disc evaluation in optic neuropathies: the optic disc assessment project

OBJECTIVE

Optic nerve morphology is affected by genetic and acquired disease. Glaucoma is the most common optic neuropathy; autosomal-dominant optic atrophy (ADOA) and Leber's hereditary optic neuropathy (LHON) are the most prevalent hereditary optic neuropathies. These 3 entities can exhibit similar topographical changes at the optic nerve head. Both ADOA and LHON have been reported to be misdiagnosed as glaucoma. Our aim was to determine whether glaucoma subspecialists and neuro-ophthalmologists can distinguish these diagnoses on optic disc assessment alone.

DESIGN

Observational study.

PARTICIPANTS

Twenty-three optic nerve experts.

METHODS

We randomized and masked 60 high-resolution stereoscopic optic disc photographs (15 ADOA images, 15 LHON, 15 glaucoma, and 15 normal controls). Experts were asked to assess the discs on 12 conventional topographic features and assign a presumptive diagnosis. Intra- and interanalysis was performed using the index of qualitative variation and absolute deviation.

MAIN OUTCOME MEASURES

Can glaucoma specialists and neuro-ophthalmologists distinguish among the disease entities by optic nerve head phenotype.

RESULTS

The correct diagnosis was identified in 85%, 75%, 27%, and 16% of the normal, glaucoma, ADOA, and LHON disc groups, respectively. The proportion of correct diagnoses within the ADOA and LHON groups was significantly lower than both normal and glaucomatous (P<0.001). Where glaucoma was chosen as the most likely diagnosis, 61% were glaucomatous, 34% were pathologic but nonglaucomatous discs, and 5% were normal. There was greater agreement for individual parameters assessed within the normal disc set when compared with pathologic discs (P<0.05). The only parameter to have a significantly greater agreement within the glaucomatous disc set when compared with ADOA or LHON disc sets was pallor, whereby experts agreed on is absence in the glaucomatous discs but were not in agreement on its presence or its absence in the ADOA and LHON discs (P<0.01).

CONCLUSIONS

Optic neuropathies can result in similar topographic changes at the optic disc, particularly in late-stage disease, making it difficult to differentiate ADOA and LHON from glaucoma based on disc assessment alone. Other clinical parameters such as acuity, color vision, history of visual loss, and family history are required to make an accurate diagnosis.

[Hereditary optic atrophies]

INTRODUCTION

Hereditary optic neuropathies, resulting from retinal ganglion cell degeneration, are a heterogeneous group of diseases ranging from asymptomatic forms to legal blindness.

STATE OF KNOWLEDGE

Two most frequent phenotypes are Kjer's disease, an autosomal dominant optic atrophy caused by OPA1 gene mutations, and Leber's disease due to maternally inherited mitochondrial DNA mutations.

PROSPECTS AND CONCLUSION

Both optic neuropathies usually isolated are sometimes associated with extraocular symptoms, especially neurological symptoms, thus justifying a systematic neurological evaluation and brain imaging.

Mouse models of dominant optic atrophy: what do they tell us about the pathophysiology of visual loss?

Dominant optic atrophy (DOA) is the most common inherited optic neuropathy affecting one in every 12,000 people. It presents with bilateral visual loss, central visual fields defects, colour vision disturbance and optic disc pallor. OPA1 has been identified as the responsible gene and its locus mapped to chromosome 3q28-q29. Mutations in this gene are responsible for the clinical phenotype in over 70% of patients with DOA. Histopathological studies in tissues from patients reveal loss of retinal ganglion cells but the paucity of viable human tissue has raised the importance of an animal model to study the pathophysiology of the disease. In the last decade considerable work has gone into the generation of animal, most notably mouse, models of Opa1 DOA. Two murine models of DOA have been published, designated B6;C3-Opa1(Q285STOP) and B6;C3-Opa1(329-355del) and they provide valuable insights with respect to neurological and visual phenotyping, mitochondrial dysfunction, optic nerve and axonal changes, retinal ganglion cell depletion and dendritic atrophy. Here we summarise the current state of knowledge of the mechanisms of disease based on data from these models of Opa1 DOA.

The neuro-ophthalmology of mitochondrial disease

Mitochondrial diseases frequently manifest neuro-ophthalmologic symptoms and signs. Because of the predilection of mitochondrial disorders to involve the optic nerves, extraocular muscles, retina, and even the retrochiasmal visual pathways, the ophthalmologist is often the first physician to be consulted. Disorders caused by mitochondrial dysfunction can result from abnormalities in either the mitochondrial DNA or in nuclear genes which encode mitochondrial proteins. Inheritance of these mutations will follow patterns specific to their somatic or mitochondrial genetics. Genotype-phenotype correlations are inconstant, and considerable overlap may occur among these syndromes. The diagnostic approach to the patient with suspected mitochondrial disease entails a detailed personal and family history, careful ophthalmic, neurologic, and systemic examination, directed investigations, and attention to potentially life-threatening sequelae. Although curative treatments for mitochondrial disorders are currently lacking, exciting research advances are being made, particularly in the area of gene therapy. Leber hereditary optic neuropathy, with its window of opportunity for timely intervention and its accessibility to directed therapy, offers a unique model to study future therapeutic interventions. Most patients and their relatives benefit from informed genetic counseling.

Axonal loss occurs early in dominant optic atrophy

PURPOSE

This study set out to investigate retinal nerve fibre layer (RNFL) thickness and best corrected visual acuity (BCVA) in relation to age in healthy subjects and patients with OPA1 autosomal dominant optic atrophy (DOA).

METHODS

We carried out a cross-sectional investigation of RNFL thickness and ganglion cell layer density in 30 healthy subjects and 10 patients with OPA1 DOA using optical coherence tomography (OCT). We then performed a regression analysis of RNFL thickness and BCVA versus age.

RESULTS

Both healthy subjects and DOA patients demonstrated a gradual reduction in RNFL thickness with age; the relationship was best described statistically by a model that assumed a constant offset between the two groups. Best corrected VA decreased significantly with age in DOA patients, in whom BCVA was correlated with peripapillary RNFL thickness in the inferior and superior peripapillary quadrants and with total macular thickness at eccentricities of 500-3000 microm. The observations were best described by a constant offset of 41.9 microm separating the two groups and an annual decrease in RNFL thickness of 0.48 microm (p < 0.0001). In patients with DOA, increasing age was associated with decreasing BCVA (p = 0.046).

CONCLUSIONS

This cross-sectional study found evidence of comparable age-related decreases in RNFL thickness in healthy subjects and in DOA patients, where the deficit in DOA patients is best described using a model that assumes the deficit between the groups does not vary with age. The gradual reduction of BCVA with age may be a consequence of a relative deficit in RNFL thickness that is established before the second decade of life.

The prevalence and natural history of dominant optic atrophy due to OPA1 mutations

PURPOSE

Autosomal dominant optic atrophy (DOA) is a major cause of visual impairment in young adults that is characterized by selective retinal ganglion cell loss. To define the prevalence and natural history of this optic nerve disorder, we performed a population-based epidemiologic and molecular study of presumed DOA cases in the north of England.

DESIGN

Case series.

PARTICIPANTS

Seventy-six affected probands with a clinical diagnosis of DOA were identified from our neuro-ophthalmology and neurogenetics database.

METHODS

OPA1 genetic testing was performed using a polymerase chain reaction-based sequencing strategy. OPA1-negative cases were then screened for large-scale OPA1 rearrangements and OPA3 mutations. Additional affected family members identified through contact tracing were examined, and longitudinal visual data were analyzed.

MAIN OUTCOME MEASURES

The prevalence and molecular characteristics of DOA in the north of England. Visual function and disease progression among patients with OPA1-positive mutations.

RESULTS

The detection rate of OPA1 mutations was 57.6% among probands with a positive family history of optic atrophy (19/33) and 14.0% among singleton cases (6/43). Approximately two thirds of our families with DOA harbored OPA1 mutations (14/22, 63.6%), and 5 novel OPA1 mutations were identified. Only 1 family carried a large-scale OPA1 rearrangement, and no OPA3 mutations were found in our optic atrophy cohort. The minimum point prevalence of DOA in the north of England was 2.87 per 100,000 (95% confidence interval [CI], 2.54-3.20), or 2.09 per 100,000 (95% CI, 1.95-2.23) when only OPA1-positive cases were considered. Snellen visual acuity varied markedly between OPA1-positive cases with a mean of 20/173 (range 20/20 to hand movements), and visual function worsened in 67.4% of patients during follow-up. The mean rate of visual loss was 0.032 logarithm of the minimum angle of resolution per year, but some patients experienced faster visual decline (range = 0-0.171 logarithm of the minimum angle of resolution/year). OPA1 missense mutations were associated with a significantly worse visual outcome compared with other mutational subtypes (P=0.0001).

CONCLUSIONS

Dominant optic atrophy causes significant visual morbidity and affects at least 1 in 35,000 of the general population.

[Hereditary optic atrophies]

Hereditary optic neuropathies are caused by mutations either in the nuclear or mitochondrial genome and lead to retinal ganglion cell death mediated by reduced oxidative phosphorylation, fragmentation of the mitochondrial network, and increased sensitivity to apoptosis. Nuclear mutations result in autosomal dominant optic atrophy, autosomal recessive optic atrophy, or X-linked recessive optic atrophy, whereas mitochondrial mutations result in Leber's hereditary optic neuropathy, which is maternally inherited. A tentative diagnosis of a hereditary optic neuropathy can usually be made on the grounds of a thorough patient and family history, visual field and color vision tests, and a detailed assessment of the optic nerve head. The rarity of hereditary optic neuropathies makes it difficult to include these disorders in the differential diagnosis. Molecular genetic testing of a blood DNA sample should be performed on every patient, with implications for future genetic counseling and prediction of the disease course.

Evaluation of nine candidate genes in patients with normal tension glaucoma: a case control study

Background

Normal tension glaucoma is a major subtype of glaucoma, associated with intraocular pressures that are within the statistically normal range of the population. Monogenic forms following classical inheritance patterns are rare in this glaucoma subtype. Instead, multigenic inheritance is proposed for the majority of cases. The present study tested common sequence variants in candidate genes for association with normal tension glaucoma in the German population.

Methods

Ninety-eight SNPs were selected to tag the common genetic variation in nine genes, namely OPTN (optineurin), RDX (radixin), SNX16 (sorting nexin 16), OPA1 (optic atrophy 1), MFN1 (mitofusin 1), MFN2 (mitofusin 2), PARL (presenilin associated, rhomboid-like), SOD2 (superoxide dismutase 2, mitochondrial) and CYP1B1 (cytochrome P450, family 1, subfamily B, polypeptide 1). These SNPs were genotyped in 285 cases and 282 fully evaluated matched controls. Statistical analyses comprised single polymorphism association as well as haplogroup based association testing.

Results

Results suggested that genetic variation in five of the candidate genes (RDX, SNX16, OPA1, SOD2 and CYP1B1) is unlikely to confer major risk to develop normal tension glaucoma in the German population. In contrast, we observed a trend towards association of single SNPs in OPTN, MFN1, MFN2 and PARL. The SNPs of OPTN, MFN2 and PARL were further analysed by multimarker haplotype-based association testing. We identified a risk haplotype being more frequent in patients and a vice versa situation for the complementary protective haplotype in each of the three genes.

Conclusion

Common variants of OPTN, PARL, MFN1 and MFN2 should be analysed in other cohorts to confirm their involvement in normal tension glaucoma.

Inherited mitochondrial optic neuropathies

Leber hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (DOA) are the two most common inherited optic neuropathies and they result in significant visual morbidity among young adults. Both disorders are the result of mitochondrial dysfunction: LHON from primary mitochondrial DNA (mtDNA) mutations affecting the respiratory chain complexes; and the majority of DOA families have mutations in the OPA1 gene, which codes for an inner mitochondrial membrane protein critical for mtDNA maintenance and oxidative phosphorylation. Additional genetic and environmental factors modulate the penetrance of LHON, and the same is likely to be the case for DOA which has a markedly variable clinical phenotype. The selective vulnerability of retinal ganglion cells (RGCs) is a key pathological feature and understanding the fundamental mechanisms that underlie RGC loss in these disorders is a prerequisite for the development of effective therapeutic strategies which are currently limited.

Premise and prediction-how optic nerve head biomechanics underlies the susceptibility and clinical behavior of the aged optic nerve head

We propose that age-related alterations in optic nerve head (ONH) biomechanics underlie the clinical behavior and increased susceptibility of the aged ONH to glaucomatous damage. The literature which suggests that the aged ONH is more susceptible to glaucomatous damage at all levels of intraocular pressure is reviewed. The relevant biomechanics of the aged ONH are discussed and a biomechanical explanation for why, on average, the stiffened peripapillary scleral and lamina cribrosa connective tissues of the aged eye should lead to a shallow (senile sclerotic) form of cupping is proposed. A logic for why age-related axon loss and the optic neuropathy of glaucoma in the aged eye may overlap is discussed. Finally, we argue for a need to characterize all forms of clinical cupping into prelaminar and laminar components so as to add precision to the discussion of clinical cupping which does not currently exist. Such characterization may lead to the early detection of ONH axonal and connective tissue pathology in ocular hypertension and eventually aid in the assessment of etiology in all forms of optic neuropathy including those that may be purely age-related.

Quantitative assessment of optic nerve head pallor

Ischaemia, loss of neural tissue, glial cell activation and tissue remodelling are symptoms of anterior ischaemic as well as glaucomatous optic neuropathy leading to pallor of the optic nerve head. Here, we describe a simple method for the pallor measurement using a fundus camera equipped with a colour CCD camera and a special dual bandpass filter. The reproducibility of the determined mean pallor value was 11.7% (coefficient of variation for repeated measurements in the same subject); the variation over six healthy subjects was 14.8%. A significant difference between the mean pallor of an atrophic disc and that of the contralateral eye of the same individual was found. However, even the clinically unaffected eye showed a significantly increased pallor compared to the mean of the healthy control group. Thus, optic disc pallor measurement, as described here, may be helpful in the early detection and follow-up of optic neuropathy.

Stratus OCT in dominant optic atrophy: features differentiating it from glaucoma

PURPOSE

To describe the Stratus optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness profile of dominant optic atrophy (DOA), to differentiate it from that of glaucoma.

METHODS

RNFL thickness was measured using Stratus OCT in 32 eyes of 16 DOA patients.

RESULTS

The temporal-most clock hour measurement was outside the 95% normal limit in 29 of the 32 DOA eyes (90.6%). The pattern of RNFL damage was bilaterally symmetrical in location and severity in all subjects.

CONCLUSION

Stratus OCT shows characteristic findings differentiating DOA from glaucoma.

Mitochondrial optic neuropathies: how two genomes may kill the same cell type?

Ocular involvement is a prevalent feature in mitochondrial diseases. Leber's hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA) are both non-syndromic optic neuropathies with a mitochondrial etiology. LHON is associated with point mutations in the mitochondrial DNA (mtDNA), which affect subunit genes of complex I. The majority of DOA patients harbor mutations in the nuclear-encoded protein OPA1, which is targeted to mitochondria and participates to cristae organization and mitochondrial network dynamics. In both disorders the retinal ganglion cells (RGCs) are specific cellular targets of the degenerative process. We here review the clinical features and the genetic bases, and delineate the possible common pathomechanism for both these disorders.

Familial cavitary optic disk anomalies: identification of a novel genetic locus

PURPOSE

To identify the chromosomal location of the gene involved in the pathogenesis of cavitary optic disk anomalies in a large pedigree with autosomal dominant inheritance of disease.

DESIGN

Linkage analysis of a pedigree affected with cavitary optic disk anomalies.

METHODS

Optic disk photographs were examined for the presence of cavitary optic disk anomalies. Sixteen affected family members and one obligate carrier were identified and studied with linkage analysis using both microarrays of single nucleotide polymorphisms (SNPs) and short tandem repeat polymorphism (STRP) markers.

RESULTS

Multipoint linkage analysis of SNP genotypes yielded a maximum nonparametric logarithm of the odds (LOD) score of 21.7 with markers located on chromosome 12q. Linkage was confirmed with 16 STRP markers in the 12q region. A maximum two-point LOD score of 4.06 (theta = 0) was obtained with marker D12S1700. The disease interval defined by observed recombinants is 9.1 cM, which corresponds to 13.5 Mbp. Three candidate genes (GDF-11, NEUROD4, and WIF1) in the chromosome 12q locus were evaluated as possible disease-causing genes. No mutations were detected in the coding sequence of these genes.

CONCLUSIONS

The discovery of the chromosomal location of a gene responsible for cavitary optic disk anomalies is a key step in identifying the genetic basis of this condition and ultimately may provide important insight into the pathogenesis of more common optic nerve diseases such as normal-tension glaucoma and primary open-angle glaucoma (POAG).

Dominant optic atrophy in a Japanese family with OPA1 frameshift mutation (V942fsX966)

PURPOSE

The authors report the ophthalmic characteristics of a male proband in a Japanese family with autosomal dominant optic atrophy (DOA) harboring a frameshift mutation in the OPA1 gene.

METHODS

Conventional ophthalmologic examinations including static automated perimetry were performed, as well as assessment of the three-generation family history. The peripapillary retinal nerve fiber layer (RNFL) was evaluated using scanning laser polarimetry. Mutation screening of the OPA1 gene was performed with polymerase chain reaction amplification and direct sequencing.

RESULTS

A frameshift mutation (p.V942fsX966) was identified in the proband and his mother. In comparison with the adolescent onset of visual loss in the proband and his maternal grandfather, the mother presented with only subtle temporal disc pallor and has never been aware of any visual disturbances. Symmetric thinned peripapillary RNFL was detected in the proband, whose visual field abnormalities were limited to central scotomas and were without mean deviation worsening between 11 to 17 years of age in both eyes. The proband's logMAR visual acuity (0.52 to 0.7) has remained almost unchanged for more than 10 years since initial evaluation at age 10.

CONCLUSIONS

The OPA1 mutation may be correlated with slow progression of DOA, and with phenotypic variations within the family. Further study is necessary to determine whether symmetric thinned peripapillary RNFL represents a feature of DOA.