Fundus findings in Leber's hereditary optic neuroretinopathy. III. Fluorescein angiographic studies

Mitochondrial retinopathies and optic neuropathies: The impact of retinal imaging on modern understanding of pathogenesis, diagnosis, and management

Advancements in ocular imaging have significantly broadened our comprehension of mitochondrial retinopathies and optic neuropathies by examining the structural and pathological aspects of the retina and optic nerve in these conditions. This article aims to review the prominent imaging characteristics associated with mitochondrial retinopathies and optic neuropathies, aiming to deepen our insight into their pathogenesis and clinical features. Preceding this exploration, the article provides a detailed overview of the crucial genetic and clinical features, which is essential for the proper interpretation of in vivo imaging. More importantly, we will provide a critical analysis on how these imaging modalities could serve as biomarkers for characterization and monitoring, as well as in guiding treatment decisions. However, these imaging methods have limitations, which will be discussed along with potential strategies to mitigate them. Lastly, the article will emphasize the potential advantages and future integration of imaging techniques in evaluating patients with mitochondrial eye disorders, considering the prospects of emerging gene therapies.

Mitochondrial optic neuropathies

Mitochondrial optic neuropathies have a leading role in the field of mitochondrial medicine ever since 1988, when the first mutation in mitochondrial DNA was associated with Leber's hereditary optic neuropathy (LHON). Autosomal dominant optic atrophy (DOA) was subsequently associated in 2000 with mutations in the nuclear DNA affecting the OPA1 gene. LHON and DOA are both characterized by selective neurodegeneration of retinal ganglion cells (RGCs) triggered by mitochondrial dysfunction. This is centered on respiratory complex I impairment in LHON and defective mitochondrial dynamics in OPA1-related DOA, leading to distinct clinical phenotypes. LHON is a subacute, rapid, severe loss of central vision involving both eyes within weeks or months, with age of onset between 15 and 35 years old. DOA is a more slowly progressive optic neuropathy, usually apparent in early childhood. LHON is characterized by marked incomplete penetrance and a clear male predilection. The introduction of next-generation sequencing has greatly expanded the genetic causes for other rare forms of mitochondrial optic neuropathies, including recessive and X-linked, further emphasizing the exquisite sensitivity of RGCs to compromised mitochondrial function. All forms of mitochondrial optic neuropathies, including LHON and DOA, can manifest either as pure optic atrophy or as a more severe multisystemic syndrome. Mitochondrial optic neuropathies are currently at the forefront of a number of therapeutic programs, including gene therapy, with idebenone being the only approved drug for a mitochondrial disorder.

Thiosulfate-Cyanide Sulfurtransferase a Mitochondrial Essential Enzyme: From Cell Metabolism to the Biotechnological Applications

Thiosulfate: cyanide sulfurtransferase (TST), also named rhodanese, is an enzyme widely distributed in both prokaryotes and eukaryotes, where it plays a relevant role in mitochondrial function. TST enzyme is involved in several biochemical processes such as: cyanide detoxification, the transport of sulfur and selenium in biologically available forms, the restoration of iron–sulfur clusters, redox system maintenance and the mitochondrial import of 5S rRNA. Recently, the relevance of TST in metabolic diseases, such as diabetes, has been highlighted, opening the way for research on important aspects of sulfur metabolism in diabetes. This review underlines the structural and functional characteristics of TST, describing the physiological role and biomedical and biotechnological applications of this essential enzyme.

Clinical Overview of Leber Hereditary Optic Neuropathy

Leber hereditary ptic neuropathy (LHON) is a disease of young adults with bilateral, painless, subacute visual loss. The peak age of onset of LHON is in the second and third decades of life. Men are 4 times more likely to be affected than women. In about 25-50% of cases, both eyes are affected simultaneously. In unilateral cases, the other eye is usually affected 2 to 3 months later. Visual acuity deteriorates to counting fingers or worse with a dense central or centrocecal scotoma. In the subacute phase, the optic disc may appear hyperemic with swelling of the peripapillary retinal nerve fibre layer, peripapillary telangiectasias, and increased vascular tortuosity. Ocular coherence tomography of the macula shows marked thinning of the ganglion cell complex even at this stage. The diagnosis of LHON is made in a subject with a consistent clinical history and/or one of three common pathogenic mitochondrial DNA (mtDNA) variants identified by molecular genetic testing. Idebenone was approved by the European Medicines Agency under exceptional circumstances for the treatment of LHON. Current evidence suggests some benefit to vision in a subset of affected individuals treated with idebenone, particularly when treated within the first year of onset of vision loss. In this article, we discuss aetiology, clinical features, diagnosis, differential dignosis, prognosis and treatment.

Longitudinal Study of Optic Disk Perfusion and Retinal Structure in Leber's Hereditary Optic Neuropathy

Purpose

The purpose of this study was to evaluate optic disk perfusion and neural retinal structure in patients with subacute Leber's hereditary optic neuropathy (LHON) and LHON carriers, as compared with healthy controls.

Methods

This study included 8 patients with LHON in the subacute stage, 10 asymptomatic carriers of a LHON-associated mitochondrial DNA mutation, and 40 controls. All subjects underwent measurement of the retinal nerve fiber layer (RNFL) thickness, the ganglion cell-inner plexiform layer (GCIPL) thickness using optical coherence tomography and optic disk microvascular perfusion (Mean Tissue [MT]) using laser speckle flowgraphy (LSFG). Patients were re-examined after a median interval of 3 months from the baseline visit.

Results

LHON carriers had higher values of RNFL thickness, GCIPL thickness, and disk area than controls (P < 0.05), whereas MT was not different between the two groups (P = 0.936). Median MT and RNFL thickness were 32% and 15% higher in the early subacute stage of the disease than in controls (P < 0.001 and P = 0.001). MT declined below the values of controls during the late subacute stage (P = 0.024), whereas RNFL thickness declined later during the dynamic stage (P < 0.001). GCIPL thickness was lower in patients with LHON than in controls independently of the stage of the disease (P < 0.001).

Conclusions

The high blood flow at the optic disk during the early subacute stage may be the consequence of vasodilation due to nitric oxide release as compensation to mitochondrial impairment. Optic disk perfusion as measured by LSFG is a promising biomarker for LHON diagnosis and monitoring as well as an objective outcome measure for assessing response to therapies.

Oxidative Stress in Optic Neuropathies

Increasing evidence indicates that changes in the redox system may contribute to the pathogenesis of multiple optic neuropathies. Optic neuropathies are characterized by the neurodegeneration of the inner-most retinal neurons, the retinal ganglion cells (RGCs), and their axons, which form the optic nerve. Often, optic neuropathies are asymptomatic until advanced stages, when visual impairment or blindness is unavoidable despite existing treatments. In this review, we describe systemic and, whenever possible, ocular redox dysregulations observed in patients with glaucoma, ischemic optic neuropathy, optic neuritis, hereditary optic neuropathies (i.e., Leber's hereditary optic neuropathy and autosomal dominant optic atrophy), nutritional and toxic optic neuropathies, and optic disc drusen. We discuss aspects related to anti/oxidative stress biomarkers that need further investigation and features related to study design that should be optimized to generate more valuable and comparable results. Understanding the role of oxidative stress in optic neuropathies can serve to develop therapeutic strategies directed at the redox system to arrest the neurodegenerative processes in the retina and RGCs and ultimately prevent vision loss.

OCTA in neurodegenerative optic neuropathies: emerging biomarkers at the eye-brain interface

OCTA imaging in optic neuropathies.

Choroidal thickness and the retinal ganglion cell complex in chronic Leber's hereditary optic neuropathy: a prospective study using swept-source optical coherence tomography

Background/Objectives

Choroidal thinning has been suggested in Leber’s hereditary optic neuropathy (LHON). No study has been conducted of the choroid in relation to the retinal ganglion cell-inner plexiform layer (RGC-IPL). We sought to measure choroidal thickness in chronic LHON and to correlate thickness changes with the RGC-IPL.

Subjects/Methods

Chronic LHON, 11778 mitochondrial DNA (mtDNA) mutation, patients (26 eyes; mean age: 35.1 ± 16.1 years) were prospectively recruited at Doheny Eye Center, University of California Los Angeles from March 2016 to July 2017. Age-matched healthy controls (27 eyes; mean age: 32.4 ± 11.1 years) were enroled for comparison. Swept-source optical coherence tomography (SS-OCT) imaging was performed in chronic LHON patients and compared with age-matched healthy controls.

Results

The macular choroid was significantly thinner in chronic LHON (250.5 ± 62.2 μm) compared with controls (313.9 ± 60.2 μm; p < 0.0001). The peripapillary choroid was also significantly thinner in chronic LHON (135.7 ± 51.4 μm) compared with controls (183.0 ± 61.8 μm, p < 0.001). Choroidal thickness strongly correlated with retinal nerve fibre layer (RNFL) thickness in both the macular (R² = 0.72; 95% CI, 0.57–0.84) and peripapillary regions (R² = 0.53; 95% CI, 0.31–0.70). Choroidal thickness was also significantly correlated with macular RGC-IPL thickness (R² = 0.51; 95% CI, 0.26–0.73).

Conclusions

Choroidal thinning in chronic LHON correlated strongly with both RNFL and RGC-IPL thicknesses. These findings may suggest a pathophysiological mechanism involving vascular pathology of the choroid in relation to the retinal ganglion cell complex in LHON.

Mitochondrial disorders and the eye

Mitochondria are cellular organelles that play a key role in energy metabolism and oxidative phosphorylation. Malfunctioning of mitochondria has been implicated as the cause of many disorders with variable inheritance, heterogeneity of systems involved, and varied phenotype. Metabolically active tissues are more likely to be affected, causing an anatomic and physiologic disconnect in the treating physicians' mind between presentation and underlying pathophysiology. We shall focus on disorders of mitochondrial metabolism relevant to an ophthalmologist. These disorders can affect all parts of the visual pathway (crystalline lens, extraocular muscles, retina, optic nerve, and retrochiasm). After the introduction reviewing mitochondrial structure and function, each disorder is reviewed in detail, including approaches to its diagnosis and most current management guidelines.

Leber's hereditary optic neuropathy: Severe vascular pathology in a severe primary mutation

The purpose of the present article was to evaluate the previously unreported vascular alterations in Leber's Hereditary Optic Neuropathy (LHON) 3460 mitochondrial DNA (mtDNA) mutation. Among the three primary mtDNA mutations, namely 11778, 14484, and 3460, LHON 3460 is the most rare and historically recognized as having the poorest visual prognosis. Optical coherence tomography angiography (OCTA) is a novel imaging modaility providing high-resolution microcirculation maps and enhancing visualization of the optic disc and peripapillary capillary beds. We herein exploit the advantages of OCTA, for the first time, to assess the optic nerve head and peripapillary microvasculature changes in an affected patient and compare these vascular changes with an asymptomatic carrier for LHON 3460, serving as a control. Vascular changes in LHON 11778 and 14484 have classically shown microvasculature attenuation localized specifically to the temporal peripapillary quadrant. In the present case, however, OCTA in LHON 3460, the most severe of the three mutational subtypes, illustrated significant vascular attenuation involving the nasal peripapillary region in addition to the temporal peripapillary microvascular changes classically seen in LHON. Our findings suggest that vascular measures may serve useful for objectively assessing mitochondrial disease. Further OCTA studies involving the nasal peripapillary region may be warranted to further understand vascular pathogenesis in LHON.

Topographic Macular Microvascular Changes and Correlation With Visual Loss in Chronic Leber Hereditary Optic Neuropathy

PURPOSE

To study the macular microvascular networks in patients affected by chronic Leber hereditary optic neuropathy (LHON) using optical coherence tomography angiography (OCTA), and to quantify these changes in different macular sectors.

DESIGN

Prospective cross-sectional study.

METHODS

Patients with a clinical and molecularly confirmed diagnosis of LHON (affected patients in the chronic stage) were enrolled from the neuro-ophthalmology clinic at the Doheny-UCLA. Patients and controls underwent a complete ophthalmologic evaluation, including imaging with OCTA.

RESULTS

Twenty-nine eyes from 15 LHON patients (14 male) and 20 eyes from 20 healthy subjects (13 male) were included in the analysis. Mean age was 32.0 ± 14.2 years (range 16-49 years) in the LHON group and 34.2 ± 10.1 years (range 23-48 years) in the control group (P = .552). In the parafoveal region, the vessel length density was lower in LHON patients, at both the SCP (9.1% ± 0.5% and 9.3% ± 0.4%, P = .041) and DCP (9.4% ± 0.5% and 9.8% ± 0.3%, P = .008) levels. In the sectorial analysis, vascular changes remained significant only in the parafoveal nasal and inferior regions. Univariate linear regression analysis demonstrated that the strongest associations with visual acuity were with parafoveal SCP perfusion density (R² = .276, P = .045) and parafoveal SCP vessel length density (R² = .277, P = .044).

CONCLUSIONS

LHON eyes have SCP and DCP changes that are mainly confined to the nasal and inferior parafoveal sectors that correspond to the papillomacular bundle. Furthermore, visual loss is associated with the SCP flow impairment, but not with the OCT-detectable structural damage.

A Meta-analysis of the association between different genotypes (G11778A, T14484C and G3460A) of Leber hereditary optic neuropathy and visual prognosis

AIM

To analyze the influences of different genotypes (G11778A, T14484C and G3460A) of Leber hereditary optic neuropathy (LHON) on visual prognosis.

METHODS

After a systematic literature search, all relevant studies evaluating the association between the three primary mutations of LHON and visual prognosis were included. All statistical tests were calculated with Revman 5.2 and STATA 12.0.

RESULTS

Ten independent studies were included finally. A significant association between the three primary mutations and prognostic vision over 0.3 were found in G11778A versus T14484C [odds ratio (OR)=0.10, 95% confidence interval (CI)=0.05-0.17, P<0.001], G11778A versus G3460A (OR=0.18, 95%CI=0.09-0.37, P<0.001) and T14484C versus G3460A (OR=2.45, 95%CI=1.10-5.48, P<0.05). In addition, obtained by pairwise comparison, the vision during onset, age of onset and sex ratio of these three kinds of patients, have no statistical significance (P>0.05).

CONCLUSION

From pairwise comparison, we conclude that these three different genotypes of LHON are related to patients' visual prognosis. The T14484C patients might have a best prognostic vision, G3460A second, and G11778A worst. And there is little relation between the three different genotypes and patients' vision, age of onset and sex ratio.

A retrospective analysis of characteristics of visual field damage in patients with Leber's hereditary optic neuropathy

The objective of this study is to investigate the characteristics and the evolution of visual field damage caused by Leber’s hereditary optic neuropathy (LHON) and to provide clinical data for the diagnosis of LHON. Parameters of visual field in 32 consecutive patients (49 eyes) with LHON who were confirmed by genetic diagnostic tests were retrospectively measured within 1 week, between three to six months, and at six months after onset. Visual field defects revealed central scotoma in 26 eyes (53.1 %), paracentral scotoma in 12 eyes (24.5 %), ceco-central defects in 6 eyes (12.2 %), blind spot enlargenment in 3 eyes (6.1 %), quadrantanopia in 2 eyes (4.1 %) within 1 week after onset. After 3 to 6 months, ceco-central defects were detected in 22 eyes (44.9 %), central isopter constriction in 10 eyes (20.4 %), hemianopia or quadrantanopia in 5 eyes (10.2 %), central scotoma in 4 eyes (8.2 %), and paracentral scotoma in 1 eye (2.0 %). After 6 months, central isopter constriction was observed in 18 eyes (36.7 %), diffuse defects in 21 eyes (42.9 %), ceco-central defects in 3 eyes (6.1 %), hemianopia or quadrantanopia in 5 eyes (10.2 %), and central scotoma in 2 eyes (4.1 %). LHON at different stages was characterized by different focal visual field defects: visual field defects in LHON patients within 1 week after onset were mostly central or paracentral scotoma, which was enlarged around the ceco-central defect, or connected to form a blind spot after 3–6 months. Diffuse and central isopter constriction defects were usually developed after 6 months. Damages firstly appeared in papillomacular bundle and gradually expanded outward. These characteristics of visual field defects reported in this study might provide a clinical basis for better diagnosis of LHON.

Characterization of retinal nerve fiber layer thickness changes associated with Leber's hereditary optic neuropathy by optical coherence tomography

In the present study, the changes in the retinal nerve fiber layer (RNFL) thickness associated with Leber’s hereditary optic neuropathy (LHON) were examined by Cirrus high definition-optical coherence tomography (OCT), and the correlation between the RNFL thickness and the best corrected visual acuity (BCVA) was evaluated. A cross-sectional study was performed. Sixty-eight eyes from patients with LHON and 30 eyes from healthy individuals were scanned. Affected eyes were divided into 5 groups according to disease duration: Group 1, ≤3 months; group 2, 4–6 months; group 3, 7–9 months; group 4, 10–12 months; and group 5, >12 months. The RNFL thickness of the temporal, superior, nasal and inferior quadrants and the 360° average were compared between the LHON groups and the control group. The eyes in groups 1 and 2 were observed to have a thicker RNFL in the superior, nasal and inferior quadrants and a higher 360°-average RNFL thickness compared with those of the control group (P<0.05), the RNFL was observed to be thinner in the temporal quadrant in groups 1 and 2. The eyes in groups 3 and 4 showed a thinner RNFL in the temporal (P=0.001), superior and inferior (both P<0.05) quadrants, and a lower 360°-average RNFL thickness as compared with controls (P=0.001). No significant correlation was identified between BCVA and RNFL thickness. RNFL thickness was observed to undergo a unique process from thickening to thinning in the patients with LHON. Changes in different quadrants occurred at different time periods and the BCVA was not found to be correlated with RNFL thickness.

Cuban epidemic optic neuropathy and its relationship to toxic and hereditary optic neuropathy

The similarities and differences between toxic/nutritional and hereditary optic neuropathy and the pathophysiologic mechanisms that they have in common are described. This is based on data from the epidemic suffered in Cuba in 1992, which affected the optic nerves of many individuals and the experience of the authors in dealing with various toxic optic neuropathies, as well as Leber's hereditary optic neuropathy.

A subhyaloid haemorrhage as the presenting symptom of bilateral optic neuropathy

A 28 year-old man with a spontaneous vitreous haemorrhage as the first sign of Leber's optic atrophy is presented. The blood collected in a central retrohyaloid area covering the left macula. The exact starting point of the haemorrhage was never positively identified, but it seemed to originate from an area of microangiopathy adjacent to the optic disc. For 8-10 months the vision of the left eye gradually decreased to counting fingers. A year later the visual acuity dropped to the same level on the right eye. The picture was compatible with Leber's optic atrophy. Other disorders causing bilateral optic neuropathy were excluded. A careful family history revealed several cases of visual problems for several generations. Vitreous haemorrhage as the first sign of Leber's optic atrophy has not previously been reported. Peripapillar microangiopathy, however, has been described in the asymptomatic stage of the disease.

The genetics of leber hereditary optic neuropathy--prototype of an inherited optic neuropathy with mitochondrial dysfunction

Leber Hereditary Optic Neuropathy is a maternally inherited condition that is characterized by acute or subacute bilateral loss of vision, usually in otherwise healthy young individuals. Several point mutations in the mitochondrial genome have been identified in patients with the condition. Scientific advances into a better understanding of the molecular pathogenesis have been hampered by the lack of an animal model for the disease. This article summarizes what is known about the clinical features, epidemiology and genetics of Leber Hereditary Optic Neuropathy and reviews recent experiments scientists have used in addressing the many unanswered questions that remain about the disease.

Mitochondrial dysfunction as a cause of optic neuropathies

Mitochondria are increasingly recognized as central players in the life and death of cells and especially of neurons. The energy-dependence of retinal ganglion cells (RGC) and their axons, which form the optic nerve, is singularly skewed. In fact, while mitochondria are very abundant in the initial, unmyelinated part of the axons anterior to the lamina cribrosa, their number suddenly decreases as the myelin sheath begins more posteriorly. The vascular system also presents different blood-brain barrier properties anterior and posterior to the lamina, possibly reflecting the different metabolic needs of the optic nerve head (unmyelinated) and of the retrobulbar optic nerve (myelinated). Mitochondrial biogenesis occurs within the cellular somata of RGC in the retina. It needs the coordinated interaction of nuclear and mitochondrial genomes. Mitochondria are then transported down the axons and distributed where they are needed. These locations are along the unmyelinated portion of the nerve, under the nodes of Ranvier in the retrobulbar nerve, and at the synaptic terminals. Efficient transportation of mitochondria depends on multiple factors, including their own energy production, the integrity of the cytoskeleton and its protein components (tubulin, etc.), and adequate myelination of the axons. Any dysfunction of these systems may be of pathological relevance for optic neuropathies with primary or secondary involvement of mitochondria. Leber's hereditary optic neuropathy (LHON) is the paradigm of mitochondrial optic neuropathies where a primary role for mitochondrial dysfunction is certified by maternal inheritance and association with specific mutations in the mitochondrial DNA (mtDNA). Clinical phenocopies of this pathology are represented by the wide array of optic neuropathies associated with vitamin depletion, toxic exposures, alcohol and tobacco abuse, and use of certain drugs. Moreover, the recent identification of mutations in the nuclear gene OPA1 as the causative factor in dominant optic atrophy (DOA, Kjer's type) brought the unexpected finding that this gene encodes for a mitochondrial protein, suggesting that DOA and LHON may be linked by similar pathogenesis. Polymorphisms in this very same gene may be associated with normal tension glaucoma (NTG), which might be considered a genetically determined optic neuropathy that again shows similarities with both LHON and DOA. Exciting new developments come from first examples of mitochondrial optic neuropathies in animal models that are genetically determined or are the result of ingenious engineering of mitochondrial gene expression, or from biochemical manipulations of the respiratory complexes. Even more exciting is the first successful attempt to correct the LHON-related complex I dysfunction by the allotopic nuclear expression of the recoded mitochondrial gene. There is hope that the genetic complexities, biochemical dysfunctions, and integrated anatomical-physiological cellular relationships will soon be precisely delineated and that promising therapeutic and prophylactic strategies will be proposed.

Familial optic atrophy with white matter changes

We report two brothers who suffer from infantile onset optic atrophy and blindness. MRI of the brain demonstrated periventricular white matter changes in both children. Neurological and developmental examination are normal. Extensive laboratory investigations rule out metabolic disorders that can be associated with optic atrophy. No mutations associated with Leber hereditary optic neuropathy (LHON) were found and sequencing of the mitochondrially encoded complex 1 subunits was normal. We suggest that this family represents either an atypical variant of LHON with a yet undescribed mtDNA mutation or a new syndrome.

Relative afferent pupillary defects in patients with Leber hereditary optic neuropathy and unilateral visual loss

PURPOSE

It has been suggested that the pupillary light reaction is relatively preserved in the affected eyes of patients with Leber hereditary optic neuropathy (LHON). To test the hypothesis that visual-pupillomotor dissociation exists in LHON, we performed a retrospective study to evaluate the magnitude of the relative afferent pupillary defect (RAPD) in patients who had experienced monocular visual loss. We also compared the size of the measured RAPD with the size of the RAPD that would be expected on the basis of documented visual field loss.

METHODS

We identified a cohort of patients with LHON and monocular visual loss, whose pupillary reactions had been quantified using neutral density filters. From a review of the case records, we determined whether an RAPD was present, as well as the magnitude of the documented RAPDs. We also calculated the expected size of the RAPD for each patient, using previously established templates that correlated the size of the RAPD with the degree of visual field loss.

RESULTS

An RAPD was identified in all 10 patients in this study. There was no significant difference between the size of the measured and predicted RAPD, nor did the size of the RAPD correlate with visual acuity or the time interval between the onset of visual loss and evaluation.

CONCLUSION

The results of this study do not support the hypothesis that visual-pupillomotor dissociation is a common feature of LHON.

Mastocytosis-induced nyctalopia

Systemic mastocytosis is characterized by an increased number of mast cells in multiple organs particularly skin. A 55-year-old man with mastocytosis presented with nyctalopia caused by malabsorption of vitamin A. Diagnosis was made by documenting a low vitamin A level and an ERG that showed rod-cone deficiency with rods affected more than cones. Vitamin A therapy led to return of good visual function. To our knowledge, this is the first reported case of mastocytosis induced nyctalopia. Vitamin A deficiency should be considered as a potential cause of visual loss in patients with sudden onset of night blindness.

Mitochondrial DNA diseases: genotype and phenotype in Leber's hereditary optic neuropathy

We have investigated 107 patients from 79 families with Leber's hereditary optic neuropathy (LHON), defined by the presence of one of the mitochondrial DNA (mtDNA) mutations at positions 11778 (60 families), 3460 (7), or 14484 (12). Only about 60% of the index patients had a history of similarly affected relatives. The ratios of affected male:female patients were 2.5:1 (11778), 2:1 (3460), and 5.7:1 (14484). Visual loss developed between the ages of 11 and 30 years in 69% with a range of 6-62 years, and this was not significantly different between mutation groups or males and females. Retinal microangiopathy was not detected in 36% of patients examined within 3 months of visual loss. A multiple sclerosis-like illness occurred in 45% of females with the 11778 mutation. Prognosis was better in the 14484 than the 3460 or 11778 patients, with useful recovery in 71% of patients. Good visual outcome was positively correlated with early age of onset (before 20 years). Unusual presentations, including young or old age at onset, caused diagnostic difficulties in this series, usually in the absence of a family history, which were resolved by mtDNA analysis. Recurrence risks to relatives could be derived from this series of families with genetically defined LHON.

Central nervous system involvement in Leber's optic neuropathy

Six months after the onset of visual loss a 23-year-old male patient with Leber's optic neuropathy associated with a mitochondrial DNA mutation developed brain stem involvement with Parinaud's syndrome and oculopalatal myoclonus. Magnetic resonance imaging (MRI) revealed a high signal area in the brain stem, corresponding to a hypodense area in the CT scan that did not show contrast enhancement. Distinct diminution but not complete remission of the MRI findings was found in the 5-year follow-up, which was not accompanied by clinical improvement. Although the MRI findings were compatible with a demyelinating lesion, neither extensive evoked potential studies nor spinal fluid examination supported this.

Optic disc pallor: a false localizing sign

A 20-year-old pregnant woman was referred with bilateral mild visual acuity loss and optic disc pallor. Because of profound color vision deficits out of proportion to her acuity loss, an abnormality of the cone photoreceptors was suspected. An electroretinogram confirmed the diagnosis of a cone dystrophy and precluded further costly and invasive testing. Cone dystrophy should be considered in the differential diagnosis of any patient with bilateral, nonrefractive visual loss, especially if color vision is disproportionately affected, even with a normal retinal appearance and no significant family history.

Late onset Leber's optic neuropathy: a case confused with ischaemic optic neuropathy

A case is reported of a 63-year-old man with progressive central visual loss in one eye followed 11 months later by involvement of the fellow eye. A diagnosis of chronic ischaemic optic neuropathy was considered. However, despite a negative family history, the absence of electrocardiographic abnormalities, and minimal fundus changes a diagnosis of Leber's optic neuropathy was made on the basis of magnetic resonance imaging findings and the mitochondrial DNA mutation at base pair 11778.

Leber hereditary optic neuropathy in Australia

Leber hereditary optic neuropathy (LHON) presents with sudden onset of visual loss mainly in young adult males. LHON is not uncommon in Australia, accounting for 2% of invalid blind pensions. We have identified 20 unrelated families carrying mitochondrial DNA mutations associated with LHON and 135 of 291 individuals with documented LHON are currently alive in Australia. The mean age of onset of visual loss for males was 26 years and for females 27 years, with a range from six to 65 years. The mean risk of visual loss was 20% for males and 4% for females. There are over 1750 male and female carriers living in Australia who have not yet lost vision; 600 carriers are under 24 years of age. The expected number of new cases of blindness from LHON is three to four per year.

The clinical characteristics of pedigrees of Leber's hereditary optic neuropathy with the 11778 mutation

In a study of the phenotypic characteristics of pedigrees of Leber's hereditary optic neuropathy positive for the mitochondrial DNA mutation at position 11778, 28 of 49 pedigrees were represented by singleton cases. Seven families, including six singleton pedigrees, had maternal family members with a mixture of mutant and normal mitochondrial DNA (heteroplasmy). Seventy-two affected individuals from 43 families showed a male predominance of 81.9% (59/72) and ages of onset of visual loss ranging from 8 to 60 years. The time interval between affected eyes averaged 1.8 months; the duration of progression of visual loss in each eye averaged 3.7 months. Visual acuity was 20/200 or worse in 107 of 109 (98.2%) eyes. Telangiectatic microangiopathy, disk pseudoedema, or vascular tortuosity, ophthalmoscopic features believed to be classic of Leber's hereditary optic neuropathy, were noted in 30 of 52 patients. Visual-evoked responses were typically absent or abnormal. Electrocardiograms, fluorescein angiograms, cerebrospinal fluid analyses, brain computed tomography, and magnetic resonance imaging were usually normal. There were no consistent neurologic or systemic illnesses associated with these Leber's pedigrees. In many cases, the diagnosis would not have been suspected because of the absence of a compatible family history, typical clinical profile, or ophthalmoscopic appearance. Genetic analysis showed the mitochondrial DNA mutation at position 11778, which established the diagnosis of Leber's hereditary optic neuropathy and has allowed for a broader view of the clinical features of this disease.

BAEP changes in Leber's hereditary optic atrophy: further confirmation of multisystem involvement

A neurophysiological study of 11 patients belonging to 5 families affected by Leber's hereditary optic atrophy is reported. Electromyography, nerve conduction velocities and somatosensory evoked potentials were normal. Visual evoked potentials were absent or delayed, desynchronized and reduced in amplitude. Brainstem auditory evoked potentials were anomalous in 64% of subjects all without hearing defects. These changes which have never before been reported, confirm multisystem involvement in this disease.

Leber's hereditary optic atrophy

Leber described a particular type of hereditary optic atrophy in 1871. The clinical features of all cases since reported are reviewed. There is characteristically acute visual loss, circumpapillary teleangiectatic micropathy, tortuosity of the retinal vessels and oedema in the retinal nerve fibres. 85% of those affected are male, but affected fathers do not transmit the condition to their children. The exact mode of inheritance is still obscure but it is suggested that inheritance may be mitochondrial; enlarged subsarcolemmal mitochondria in LOA patients have been described. Colour vision defects are observed not only in patients, but also in presumed carriers. Electrophysiological investigations demonstrate optic nerve damage, but are not indicative of any particular pathology. It has been reported that in many cases of LOA the severity of the disease is related to tobacco smoking. Increased cyanocobalamin blood levels in patients and increased cyanide blood levels support this hypothesis.

Studies on Leber's optic neuropathy III

Neurological investigations, HLA-typing and viral antibody studies were performed in patients with Leber's optic neuropathy (LON), in individuals at risk to develop the disease, in obligatory (female) carriers of the disease, and compared with controls. The only relevant findings were an excess of minor neurological abnormalities in patients with LON and in some individuals from the at risk group. Occasionally, an association of LON and a multiple sclerosis-like picture was observed.

Arteriovenous anastomoses of the retina

The authors reviewed the clinical findings in 13 patients followed at Montefiore Medical Center and in 85 cases described in the literature with primary arteriovenous communication of the retina (AVCR). The characteristics of AVCR include: young age at detection; both sexes affected; detected on routine examination, and less frequently after decreased vision or referral after diagnosing systemic arteriovenous communication (AVC); unilateral involvement; single or multiple sites in the same fundus; and predilection for the papillomacular area and the superotemporal quadrant. Vision correlated inversely with the grade of AVCR. The presence of concomitant systemic AVC correlated directly with the grade of AVCR. It is concluded that grade I AVCR and the majority of grade II AVCR represent isolated retinal vascular anomalies, and there is no need for extensive search for systemic AVC if these patients remain asymptomatic.