Abstract
Historically, distinct mitochondrial syndromes were recognised clinically by their ocular features. Due to their predilection for metabolically active tissue, mitochondrial diseases frequently involve the eye, resulting in a range of ophthalmic manifestations including progressive external ophthalmoplegia, retinopathy and optic neuropathy, as well as deficiencies of the retrochiasmal visual pathway. With the wider availability of genetic testing in clinical practice, it is now recognised that genotype-phenotype correlations in mitochondrial diseases can be imprecise: many classic syndromes can be associated with multiple genes and genetic variants, and the same genetic variant can have multiple clinical presentations, including subclinical ophthalmic manifestations in individuals who are otherwise asymptomatic. Previously considered rare diseases with no effective treatments, considerable progress has been made in our understanding of mitochondrial diseases with new therapies emerging, in particular, gene therapy for inherited optic neuropathies.
摘要
从历史上来看, 不同的线粒体疾病的症状在临床上可由眼科表现识别。由于线粒体与代谢活跃组织相关, 疾病常累及眼部, 导致一系列的眼部表现, 包括进行性眼外肌麻痹、视网膜视神经病变, 以及视交叉后路缺陷。随着基因检测在临床实践中的广泛应用, 研究人员已意识到线粒体疾病中的基因型-表型相关性可能不精确: 很多典型症状可能与多个基因和基因突变相关, 并且相同的基因突变可能有多种临床表现, 包括无症状者的亚临床表现。线粒体疾病之前认为是无有效治疗方法的罕见病, 随着新治疗方法的出现, 我们对线粒体疾病的理解取得了较大进步, 尤其表现在遗传性视神经病变的基因治疗。
Similar content being viewed by others
Introduction
Mitochondrial diseases are a clinically heterogeneous group of disorders that arise as a result of dysfunction of the mitochondrial respiratory chain [1]. Historically, these diseases were classified into distinct syndromes based on their clinical presentations. However, with developments in whole genome sequencing technology and increased availability of genetic testing in the past decade, in particular mitochondrial DNA (mtDNA) sequencing, it is now recognised that many of these classic syndromes are associated with multiple genes and genetic variants, including variants in the nuclear DNA (nDNA) (Table 1). Additionally, the same genetic variant may have different clinical presentations depending on the level of tissue mutation load, a unique characteristic of mitochondrial disease. Within a cell, pathogenic mtDNA mutations are frequently mixed with normal mtDNA, a state known as heteroplasmy (Fig. 1). As the percentage of mutant mtDNA (mutant load) increases, the bioenergetic defect becomes increasingly severe, leading to a continuum of clinical presentations [1]. In this review, we provide an update on the ophthalmic presentations of mitochondrial disease and review their management, including extraocular manifestations, retinopathy, optic neuropathy, and visual dysfunction arising from dysfunction of the retrochiasmal visual pathways.
Extraocular manifestations
Given the high energy demand of muscle tissue, extraocular muscle dysfunction is one of the major clinical manifestations of mitochondrial disease. First described by Von Graefe in 1868 [2], the syndrome of progressive external ophthalmoplegia (often termed ‘chronic progressive external ophthalmoplegia’ or CPEO) is a constellation of clinical findings relating to myopathy of the extraocular muscles, including bilateral ptosis and symmetrical reduction in ocular movements due to myopathy and, in later stages, to fibrotic restriction (Fig. 2). Affecting ~3.4 people per 100,000, CPEO can present on a spectrum between an isolated CPEO phenotype and disorders where CPEO is one feature of a multisystem syndrome—as a group termed CPEO ‘plus’ (Table 1) [3].
The onset of CPEO is often insidious and while it can occur at any age, it is often seen in young adults (mean age 29 years) presenting with bilateral symmetrical ptosis as the result of poor function of the levator palpebrae superioris [3,4,5]. Classically, diplopia was not considered a presenting feature: the symmetrical nature of the extraocular myopathy and the ptosis itself (and in many patients a degree of visual suppression) preventing diplopia in the early stages. However, several case series have reported diplopia in up to 50% of cases, and early oculomotor changes can often be seen on examination including slowed saccades before any deviation becomes manifest [6, 7].
Clinical spectrum of Chronic Progressive External Ophthalmoplegia (CPEO)
Several syndromes include a CPEO presentation (Table 1)—perhaps the most notable CPEO plus syndrome was described by Kearns and Sayre [8], in which CPEO is accompanied by pigmentary retinopathy (discussed in Retinal Manifestations below), cardiac conduction defects, raised cerebrospinal fluid protein levels, and cerebellar ataxia [9]. With a prevalence of ~1.5 per 100,000 in one study [10], the Kearns Sayre Syndrome (KSS) generally presents in young adults and represents an intermediate phenotype along the spectrum of disease severity. At the more severe end of this spectrum lies the Pearson Syndrome, where large-scale mitochondrial DNA deletions lead to respiratory chain dysfunction manifesting with sideroblastic anaemia, exocrine pancreatic dysfunction, and myopathy among other features usually leading to death in infancy [11, 12]. In patients with the Pearson Syndrome who survive infancy, CPEO often develops together with pigmentary retinopathy and Leigh-like Syndrome (discussed in ‘Retinal Manifestations’ below) in early life.
This spectrum of severity is reflected in the genetic heterogeneity underlying CPEO. While around half of solved cases are sporadic, 50% are inherited either in an autosomal fashion or maternally (Table 1) [7]. Like many mitochondrial disorders, there can be great variability in the phenotypes of patients with the same genetic diagnoses, which are thought to relate to the level of mitochondrial heteroplasmy or exposure to environmental mitochondrial toxins [13, 14].
Extraocular manifestations—management
Whilst the clinical diagnosis is often not in doubt, several conditions (Table 2) can present with some features common to CPEO and these should be excluded by appropriate examination or investigation, especially if genetic testing for a genetic variant associated with CPEO is uninformative. Additionally, all patients with CPEO should undergo a dilated fundus examination to visualise retinal abnormalities that might suggest KSS. If KSS is suspected clinically, neurological assessment and additional investigations such as cardiac assessment and lumbar puncture should be considered.
Management of ptosis
Ptosis associated with CPEO can be challenging both for the patient (who may adopt an altered head position, have their visual axis obscured or be troubled by poor cosmesis) and the surgeon (with continued progression, absent Bell’s reflex and poor residual levator palpebrae superioris function (LPF)). In early disease, where there is residual LPF, surgical approaches to augment this muscle can be useful [15]. However, as muscle function becomes impaired with progression of the disease, suspensory approaches with fascia lata or, more often, silicone are indicated [4, 16, 17]. Conservative measures such as ptosis props and scleral contact lenses have a role and, while they may be poorly tolerated early in disease, they may have an adjunctive role when surgical options have been exhausted or are not appropriate [15].
Management of ophthalmoplegia
Symptomatic ophthalmoplegia is managed with a combination of conservative approaches, botulinum toxin, and surgical interventions. The progressive, symmetrical nature of ophthalmoplegia may necessitate a nuanced discussion with patients regarding the need for repeated interventions over their lifetime and patients should be carefully consented for the high likelihood of multiple procedures, and the need for adjuncts as the disease progresses.
While occlusion will resolve diplopia, Fresnel prisms can be useful in managing a varying deviation as they can be easily adjusted over time. Prisms can also be helpful for small residual angles, particularly as there is suggestion that CPEO patients can have narrower fusional amplitudes [18]. Botulinum toxin alone, although insufficient for the larger exodeviations seen in CPEO, may be particularly useful for residual angles that may develop post-surgically [19, 20].
Strabismus surgery for CPEO should be carefully planned and patients informed that the deviation will invariably return given the progressive nature of the underlying cytopathy. Forced duction testing can be very useful, as under-action and failure of ipsilateral antagonist muscles to relax can both lead to deviations. It has been suggested that muscle resection can be more effective than recession [21]. However, one larger case series has suggested near-maximal horizontal surgery using adjustable sutures to be the most effective [20].
Retinal manifestations
Although primary retinal ganglion cell (RGC) loss involving the inner retina and optic atrophy are classical manifestations of mitochondrial disease (discussed in ‘Optic Neuropathy’ below), outer retinal involvement is also observed as part of the phenotype of several syndromic central nervous system diseases caused by mtDNA mutations. Additionally, pathogenic defects in nDNA have also been identified to cause combined optic atrophy and retinal dystrophy [22]. In the outer retina, the photoreceptors, retinal pigment epithelium (RPE), and Müller cells contain large numbers of mitochondria, making these cell populations vulnerable to mitochondria dysfunction and oxidative damage [23]. The retina can be involved as part of the phenotype of several mitochondrial syndromes including KSS; Neuropathy, Ataxia, Retinitis Pigmentosa (NARP); Maternally Inherited Leigh Syndrome (MILS); and Maternally Inherited Diabetes and Deafness (MIDD) (discussed in more detail below) [22]. Historically, various terms have been used to describe the retinal manifestations of mitochondrial disease, including ‘pigmentary degeneration’ and ‘salt and pepper retinopathy’ [9, 24]. Identification of these classic mitochondrial retinopathies may help facilitate the clinical and molecular diagnosis of specific mitochondrial diseases.
A recent classification system, based on multimodal imaging findings from 23 patients with retinopathy and genetically-defined mitochondrial disease, identified three distinct phenotypes of mitochondrial retinopathy [25]. Sporadic single large-scale mtDNA deletions, such as those associated with CPEO, exhibited either mild, focal pigmentary abnormalities on ophthalmoscopy (Type 1 mitochondrial retinopathy; usually visually asymptomatic), or widespread granular fundus alterations on ophthalmoscopy and autofluorescence (Type 3 mitochondrial retinopathy; frequently associated with nyctalopia and severe widespread visual dysfunction). Type 2 mitochondrial retinopathy was usually associated with the m.3243A>G mutation in MT-TL1 (the most common disease-causing mtDNA mutation with a carrier rate of ~1 in 400 people) [26] and displayed a spectrum of manifestations including multifocal white-yellowish subretinal deposits and pigmentary changes (limited to the posterior pole) or chorioretinal atrophy with or without foveal involvement. Patients frequently reported problems in dim light and, if they had chorioretinal atrophy, severe central vision loss.
Neuropathy, Ataxia, Retinitis Pigmentosa (NARP) and Maternally Inherited Leigh Syndrome (MILS)
NARP is a progressive neurodegenerative disease that presents clinically with the features in its name and other associated findings, including seizures, cognitive impairment, and developmental delay [27]. The characteristic ocular finding is a salt and pepper retinopathy that appears early in the disease course and eventually progresses to retinitis pigmentosa [28]. Other visual symptoms include nyctalopia and constriction of visual fields.
NARP is primarily caused by the m.8993T>G/C mutation in MT-ATP6, leading to complex V dysfunction and impaired ATP production [27, 29]. This particular mtDNA variant is also the most common one associated with MILS, a severe multisystem mitochondrial disorder characterised by encephalopathy, lactic acidosis, cardiomyopathy, and respiratory dysfunction [30]. In contrast to NARP, which generally presents in childhood, the first signs of MILS are seen in infancy [31]. The heteroplasmy level of the mutant mtDNA species is helpful in determining the phenotypic expression of the mtDNA variant, with a high mutation load (>90%) causing the more severe MILS phenotype and a mutation load 60–90% causing NARP [32, 33].
Maternally Inherited Diabetes and Deafness (MIDD)
First described by Van den Ouweland et al. [34], MIDD is a multisystem disorder characterised by maternally transmitted diabetes mellitus and sensorineural hearing deafness. Most cases of MIDD are due to the aforementioned m.3243A>G mutation in MT-TL1, encoding a mitochondrial transfer RNA. It should be noted that the m.3243A>G mutation is clinically heterogeneous and, depending on mutant load and tissue level, can present as MIDD; Mitochondrial Encephalomyopathy Lactic Acidosis and Stroke-like episodes (MELAS); CPEO; an overlap syndrome; or with a clinical phenotype that does not fall within the criteria for currently recognised mitochondrial syndromes [26].
Most patients with MIDD remain visually asymptomatic with good visual acuity. Despite diabetes mellitus being a defining feature, the prevalence of diabetic retinopathy is lower than those with type 2 diabetes mellitus of similar duration [35, 36]. Instead, the majority of patients with MIDD exhibit a specific macular pattern dystrophy (mean age at detection 46.5 years, range 27–71 years) [35, 36], characterised by RPE hyperpigmentation that surrounds the macula or is more extensive and encompasses the optic disc [35, 37, 38]. A unique feature of the macular pattern dystrophy in MIDD, that may help to distinguish it from other maculopathies, is the finding of occult RPE disruption seen on autofluorescence imaging as a diffuse speckled pattern, extending beyond the macular abnormalities seen on ophthalmoscopy [38, 39]. Autofluorescence imaging has been suggested as a useful marker of disease progression [40, 41]. As the disease progresses, areas of speckled pigments on autofluorescence evolve into areas of atrophy, with relative sparing of the fovea until the advanced stages of the disease.
Multimodal imaging, in particular, OCT and wide-field autofluorescence, should be performed as subtle outer retinal changes of mitochondrial retinopathies may not be obvious on ophthalmoscopy. Visual electrophysiology testing including visually-evoked potentials, pattern electroretinogram and full-field electroretinogram should also be considered, especially in subclinical forms of mitochondrial retinopathies as they may help to localise the abnormality and detect outer retinal dysfunction while there are no structural changes observed.
Retinal manifestations—management
Although genotype-phenotype correlations are not always clear-cut, the specific pattern of retinal abnormalities may be helpful in guiding genetic testing and subsequent management. Macular pattern dystrophy in association with hearing loss are defining features of MIDD and this combination should prompt testing for the m.3243A>G mutation in MT-TL1. As the m.3243A>G mutation is associated with both MIDD and MELAS, patients with this mutation should be referred for multidisciplinary investigations to identify other organ involvement, including sensorineural hearing loss, diabetes, cardiac conduction defects and kidney disease.
There are currently no specific pharmacological treatments for mitochondrial retinopathies. Those with advanced disease involving the fovea or with chorioretinal atrophy may benefit from supportive management, such as visual impairment registration and referral to a low vision clinic.
Optic neuropathies
Inherited optic neuropathies (IONs) are characterised by bilateral and progressive degeneration of the optic nerve secondary to a genetic variant which invariably affects mitochondrial function [42]. Clinically, they are characterised by loss of visual acuity/field and colour vision caused by RGC loss. The archetypical ION is an isolated bilateral optic neuropathy as seen in Leber hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA). However, many IONs can present as part of a systemic syndrome such as Wolfram syndrome, where the optic atrophy is accompanied by diabetes insipidus, diabetes mellitus and sensorineural hearing loss. Furthermore, a subgroup of LHON and DOA can sometimes present with extraocular features referred to as LHON “plus” and DOA “plus”, respectively. It should be stressed, however, that establishing causation between these extraocular features and the underlying mtDNA or nDNA genetic variant is not always straightforward.
Leber Hereditary Optic Neuropathy (LHON)
Considered the prototype of mitochondrial disease, LHON is an important cause of inherited mitochondrial blindness, affecting ~ 1 in 30,000 individuals [43]. In most affected individuals (peak age 15–35 years), painless bilateral sequential vision loss is the only symptom of LHON, with an inter-eye delay of weeks to months. Visual acuity declines rapidly to 20/200 or less, reaching a nadir ~ 4–6 weeks after onset. Long-term visual prognosis is generally poor for most patients with visual acuity worse than 20/400 [44].
Three primary mtDNA point mutations (m.3460G>A in MT-ND1, m.11778G>A in MT-ND4 and m.14484T>C in MT-ND6) account for ∼ 90% of LHON cases globally [42]. These three mutations all involve genes encoding subunits of complex I, the first enzyme of the mitochondrial respiratory chain. In LHON, defective mitochondrial oxidative phosphorylation precipitates a bioenergetic crisis and elevated levels of reactive oxygen species (ROS), leading to RGC dysfunction and release of signalling factors that trigger cellular apoptosis [23]. The m.14484T>C mtDNA variant and onset of LHON before the age of 12 (childhood LHON) are associated with a relatively more favourable visual prognosis [45].
Not all individuals who carry a genetic mutation associated with LHON will experience visual loss. The penetrance of LHON has often be reported as being ~50% among male carriers and ~10% among female carriers, highlighting the marked sex bias. However, in a recent national Australian cohort, the penetrance of LHON was reported to be lower at 17.5% for male carriers and 5.4% for female carriers [46]. These differences could reflect other genetic and environmental influences with the latter possibly having changed over time e.g. smoking habits. This incomplete penetrance is not fully explained by mitochondrial heteroplasmy, as most LHON carriers are homoplasmic. External metabolic stressors, such as smoking, excessive alcohol consumption and certain toxins, have been identified as contributory factors leading to disease conversion [47]. Hormonal influences are also thought to modulate the risk of visual loss with oestrogens being protective for female LHON carriers [48, 49].
Dominant Optic Atrophy (DOA)
DOA is the most common ION with an estimated minimum prevalence of 1 in 25,000 [50]. Visual loss typically presents in the first two decades of life with the majority of patients declining steadily over time to reach the criteria for registration as visually impaired. OPA1 (3q21) is thought to be the causative gene in over 60–70% of DOA cases [51]. Over 450 pathogenic variants of OPA1 have been described with missense variants and variants located in the GTPase/dynamin domain associated with a worse ocular phenotype and a higher probability of DOA ‘plus’ [78].
Retrochiasmal vision loss—management
Managing the retrochiasmal manifestations of mitochondrial diseases is challenging. There are currently no licensed disease-modifying treatments. Medications that have been trialled to prevent or treat stroke-like episodes in MELAS include coenzyme-Q10, L-arginine, L-carnitine and high-dose taurine supplementation [79]. Treatment for MELAS is generally supportive and may include referral to low vision service for those with visual impairment; cochlear implantation for those with sensorineural hearing loss; anticonvulsant therapy for seizure prevention (avoiding sodium valproate), and screening for other organ involvement including cardiac conduction defects, diabetes, kidney disease, and other ocular manifestations.
Conclusion
Due to their predilection for metabolically active tissues, the eye is involved in over half of all patients with mitochondrial disease; affecting the extraocular muscles, retina and optic nerves. Although often considered as rare diseases with little or no effective treatments, significant progress has been made in the development of gene therapy and gene editing platforms, in particular for patients with mitochondrial optic neuropathies. A paradigm shift in therapy for mitochondrial disorders is underway and this must be reflected in a dramatic alternation in our clinical management of these patients: early and accurate molecular diagnosis must be the standard of care for these patients. In order to have access to nascent gene therapies and the exciting range of therapeutic trials underway in this traditionally underserved area of ophthalmology, patients need timely, expert neuro-ophthalmological evaluation and genetic testing.
Summary
-
Ophthalmic manifestations of mitochondrial disease include, but are not limited to, progressive external ophthalmoplegia, retinopathy, optic neuropathy, and deficiencies of the retrochiasmal visual pathways.
-
Although traditionally recognised by ‘classic’ presentations, genotype–phenotype correlations in mitochondrial disease are imprecise; all patients should have genetic testing even if the presentation is not ‘classic’.
-
Recent advancements in the development of gene therapy and gene editing techniques for mitochondrial diseases underscore the importance of timely neuro-ophthalmological evaluation and genetic testing.
References
Wallace DC, Chalkia D. Mitochondrial DNA genetics and the heteroplasmy conundrum in evolution and disease. Cold Spring Harb Perspect Biol. 2013;5:a021220.
Von Graefe A. Verhandlungen arztlicher gesellschaften. Berliner medicinische gesellschaft. Berl Klin Wschr. 1868;5:125–7.
Yu-Wai-Man P, Clements AL, Nesbitt V, Griffiths PG, Gorman GS, Schaefer AM, et al. A national epidemiological study of chronic progressive external ophthalmoplegia in the United Kingdom - molecular genetic features and neurological burden. Investig Ophthalmol Vis Sci. 2014;55:5109–9.
Park RB, Akella SS, Aakalu VK. A review of surgical management of progressive myogenic ptosis. Orbit. 2023;42:11–24.
Bucelli RC, Lee MS, McClelland CM. Chronic progressive external ophthalmoplegia in the absence of ptosis. J Neuroophthalmol. 2016;36:270–4.
Ritchie AE, Griffiths PG, Chinnery PF, Davidson AW. Eye movement recordings to investigate a supranuclear component in chronic progressive external ophthalmoplegia: a cross-sectional study. Br J Ophthalmol. 2010;94:1165–8.
McClelland C, Manousakis G, Lee MS. Progressive external ophthalmoplegia. Curr Neurol Neurosci Rep. 2016;16:53.
Kearns TP, Sayre GP. Retinitis pigmentosa, external ophthalmophegia, and complete heart block: unusual syndrome with histologic study in one of two cases. AMA Arch Ophthalmol. 1958;60:280–9.
Kearns TP. External ophthalmoplegia, pigmentary degeneration of the retina, and cardiomyopathy: a newly recognized syndrome. Trans Am Ophthalmol Soc. 1965;63:559–625.
Remes AM, Majamaa-Voltti K, Karppa M, Moilanen JS, Uimonen S, Helander H, et al. Prevalence of large-scale mitochondrial DNA deletions in an adult Finnish population. Neurology. 2005;64:976–81.
Pearson HA, Lobel JS, Kocoshis SA, Naiman JL, Windmiller J, Lammi AT, et al. A new syndrome of refractory sideroblastic anemia with vacuolization of marrow precursors and exocrine pancreatic dysfunction. J Pediatr. 1979;95:976–84.
Farruggia P, Di Marco F, Dufour C. Pearson syndrome. Expert Rev Hematol. 2018;11:239–46.
Heighton JN, Brady LI, Sadikovic B, Bulman DE, Tarnopolsky MA. Genotypes of chronic progressive external ophthalmoplegia in a large adult-onset cohort. Mitochondrion. 2019;49:227–31.
Pfeffer G, Sirrs S, Wade NK, Mezei MM. Multisystem disorder in late-onset chronic progressive external ophthalmoplegia. Can J Neurol Sci. 2011;38:119–23.
Lane CM, Collin JR. Treatment of ptosis in chronic progressive external ophthalmoplegia. Br J Ophthalmol. 1987;71:290–4.
Eshaghi M, Arabi A, Eshaghi S. Surgical management of ptosis in chronic progressive external ophthalmoplegia. Eur J Ophthalmol. 2021;31:2064–8.
Ahn J, Kim NJ, Choung HK, Hwang SW, Sung M, Lee MJ, et al. Frontalis sling operation using silicone rod for the correction of ptosis in chronic progressive external ophthalmoplegia. Br J Ophthalmol. 2008;92:1685–8.
Wallace DK, Sprunger DT, Helveston EM, Ellis FD. Surgical management of strabismus associated with chronic progressive external ophthalmoplegia. Ophthalmology. 1997;104:695–700.
Richardson C, Smith T, Schaefer A, Turnbull D, Griffiths P. Ocular motility findings in chronic progressive external ophthalmoplegia. Eye. 2005;19:258–63.
Tinley C, Dawson E, Lee J. The management of strabismus in patients with chronic progressive external ophthalmoplegia. Strabismus. 2010;18:41–7.
Sorkin JA, Shoffner JM, Grossniklaus HE, Drack AV, Lambert SR. Strabismus and mitochondrial defects in chronic progressive external ophthalmoplegia. Am J Ophthalmol. 1997;123:235–42.
Zeviani M, Carelli V. Mitochondrial retinopathies. Int J Mol Sci. 2021;23:210.
Lefevere E, Toft-Kehler AK, Vohra R, Kolko M, Moons L, Van Hove I. Mitochondrial dysfunction underlying outer retinal diseases. Mitochondrion. 2017;36:66–76.
Mullie MA, Harding AE, Petty RK, Ikeda H, Morgan-Hughes JA, Sanders MD. The retinal manifestations of mitochondrial myopathy. A study of 22 cases. Arch Ophthalmol. 1985;103:1825–30.
Birtel J, von Landenberg C, Gliem M, Gliem C, Reimann J, Kunz WS, et al. Mitochondrial retinopathy. Ophthalmol Retin. 2022;6:65–79.
Nesbitt V, Pitceathly RD, Turnbull DM, Taylor RW, Sweeney MG, Mudanohwo EE, et al. The UK MRC Mitochondrial Disease Patient Cohort Study: clinical phenotypes associated with the m.3243A>G mutation-implications for diagnosis and management. J Neurol Neurosurg Psychiatry. 2013;84:936–8.
Holt IJ, Harding AE, Petty RK, Morgan-Hughes JA. A new mitochondrial disease associated with mitochondrial DNA heteroplasmy. Am J Hum Genet. 1990;46:428–33.
Kerrison JB, Biousse V, Newman NJ. Retinopathy of NARP syndrome. Arch Ophthalmol. 2000;118:298–9.
Rantamaki MT, Soini HK, Finnila SM, Majamaa K, Udd B. Adult-onset ataxia and polyneuropathy caused by mitochondrial 8993T->C mutation. Ann Neurol. 2005;58:337–40.
Santorelli FM, Shanske S, Macaya A, DeVivo DC, DiMauro S. The mutation at nt 8993 of mitochondrial DNA is a common cause of Leigh’s syndrome. Ann Neurol. 1993;34:827–34.
Leigh D. Subacute necrotizing encephalomyelopathy in an infant. J Neurol Neurosurg Psychiatry. 1951;14:216–21.
Carelli V, Baracca A, Barogi S, Pallotti F, Valentino ML, Montagna P, et al. Biochemical-clinical correlation in patients with different loads of the mitochondrial DNA T8993G mutation. Arch Neurol. 2002;59:264–70.
Makela-Bengs P, Suomalainen A, Majander A, Rapola J, Kalimo H, Nuutila A, et al. Correlation between the clinical symptoms and the proportion of mitochondrial DNA carrying the 8993 point mutation in the NARP syndrome. Pediatr Res. 1995;37:634–9.
van den Ouweland JM, Lemkes HH, Ruitenbeek W, Sandkuijl LA, de Vijlder MF, Struyvenberg PA, et al. Mutation in mitochondrial tRNA(Leu)(UUR) gene in a large pedigree with maternally transmitted type II diabetes mellitus and deafness. Nat Genet. 1992;1:368–71.
Guillausseau PJ, Massin P, Dubois-LaForgue D, Timsit J, Virally M, Gin H, et al. Maternally inherited diabetes and deafness: a multicenter study. Ann Intern Med. 2001;134:721–8.
Massin P, Virally-Monod M, Vialettes B, Paques M, Gin H, Porokhov B, et al. Prevalence of macular pattern dystrophy in maternally inherited diabetes and deafness. GEDIAM Group. Ophthalmology. 1999;106:1821–7.
Smith PR, Bain SC, Good PA, Hattersley AT, Barnett AH, Gibson JM, et al. Pigmentary retinal dystrophy and the syndrome of maternally inherited diabetes and deafness caused by the mitochondrial DNA 3243 tRNA(Leu) A to G mutation. Ophthalmology. 1999;106:1101–8.
Michaelides M, Jenkins SA, Bamiou DE, Sweeney MG, Davis MB, Luxon L, et al. Macular dystrophy associated with the A3243G mitochondrial DNA mutation. Distinct retinal and associated features, disease variability, and characterization of asymptomatic family members. Arch Ophthalmol. 2008;126:320–8.
Rath PP, Jenkins S, Michaelides M, Smith A, Sweeney MG, Davis MB, et al. Characterisation of the macular dystrophy in patients with the A3243G mitochondrial DNA point mutation with fundus autofluorescence. Br J Ophthalmol. 2008;92:623–9.
Ovens CA, Ahmad K, Fraser CL. Fundus autofluorescence in maternally inherited diabetes and deafness: the gold standard for monitoring maculopathy? Neuroophthalmology. 2020;44:168–73.
Muller PL, Treis T, Pfau M, Esposti SD, Alsaedi A, Maloca P, et al. Progression of retinopathy secondary to maternally inherited diabetes and deafness—evaluation of predicting parameters. Am J Ophthalmol. 2020;213:134–44.
Newman NJ, Yu-Wai-Man P, Biousse V, Carelli V. Understanding the molecular basis and pathogenesis of hereditary optic neuropathies: towards improved diagnosis and management. Lancet Neurol. 2022;22:172–88.
Yu-Wai-Man P, Griffiths PG, Brown DT, Howell N, Turnbull DM, Chinnery PF. The epidemiology of Leber hereditary optic neuropathy in the North East of England. Am J Hum Genet. 2003;72:333–9.
Yu-Wai-Man P, Newman NJ, Carelli V, La Morgia C, Biousse V, Bandello FM, et al. Natural history of patients with Leber hereditary optic neuropathy-results from the REALITY study. Eye. 2022;36:818–26.
Barboni P, La Morgia C, Cascavilla ML, Hong EH, Battista M, Majander A, et al. Childhood-onset leber hereditary optic neuropathy - clinical and prognostic insights. Am J Ophthalmol. 2022.
Lopez Sanchez MIG, Kearns LS, Staffieri SE, Clarke L, McGuinness MB, Meteoukki W, et al. Establishing risk of vision loss in Leber hereditary optic neuropathy. Am J Hum Genet. 2021;108:2159–70.
Mejia-Vergara AJ, Seleme N, Sadun AA, Karanjia R. Pathophysiology of conversion to symptomatic leber hereditary optic neuropathy and therapeutic implications: a review. Curr Neurol Neurosci Rep. 2020;20:11.
Jankauskaite E, Ambroziak AM, Hajieva P, Oldak M, Tonska K, Korwin M, et al. Testosterone increases apoptotic cell death and decreases mitophagy in Leber’s hereditary optic neuropathy cells. J Appl Genet. 2020;61:195–203.
Pisano A, Preziuso C, Iommarini L, Perli E, Grazioli P, Campese AF, et al. Targeting estrogen receptor beta as preventive therapeutic strategy for Leber’s hereditary optic neuropathy. Hum Mol Genet. 2015;24:6921–31.
Yu-Wai-Man P, Chinnery PF. Dominant optic atrophy: novel OPA1 mutations and revised prevalence estimates. Ophthalmology. 2013;120:1712.e1711.
Alexander C, Votruba M, Pesch UE, Thiselton DL, Mayer S, Moore A, et al. OPA1, encoding a dynamin-related GTPase, is mutated in autosomal dominant optic atrophy linked to chromosome 3q28. Nat Genet. 2000;26:211–5.
Weisschuh N, Schimpf-Linzenbold S, Mazzola P, Kieninger S, **ao T, Kellner U, et al. Mutation spectrum of the OPA1 gene in a large cohort of patients with suspected dominant optic atrophy: Identification and classification of 48 novel variants. PLoS One. 2021;16:e0253987.
Yu-Wai-Man P, Griffiths PG, Burke A, Sellar PW, Clarke MP, Gnanaraj L, et al. The prevalence and natural history of dominant optic atrophy due to OPA1 mutations. Ophthalmology. 2010;117:1538–46. 1546.e1531
Yu-Wai-Man P, Griffiths PG, Gorman GS, Lourenco CM, Wright AF, Auer-Grumbach M, et al. Multi-system neurological disease is common in patients with OPA1 mutations. Brain. 2010;133:771–86.
Del Dotto V, Carelli V. Dominant Optic Atrophy (DOA): modeling the kaleidoscopic roles of OPA1 in mitochondrial homeostasis. Front Neurol. 2021;12:681326.
Amati-Bonneau P, Valentino ML, Reynier P, Gallardo ME, Bornstein B, Boissiere A, et al. OPA1 mutations induce mitochondrial DNA instability and optic atrophy ‘plus’ phenotypes. Brain. 2008;131:338–51.
Olichon A, Elachouri G, Baricault L, Delettre C, Belenguer P, Lenaers G. OPA1 alternate splicing uncouples an evolutionary conserved function in mitochondrial fusion from a vertebrate restricted function in apoptosis. Cell Death Differ. 2007;14:682–92.
Muench NA, Patel S, Maes ME, Donahue RJ, Ikeda A, Nickells RW. The influence of mitochondrial dynamics and function on retinal ganglion cell susceptibility in optic nerve disease. Cells. 2021;10:1593.
Pass T, Wiesner RJ, Pla-Martin D. Selective neuron vulnerability in common and rare diseases-mitochondria in the focus. Front Mol Biosci. 2021;8:676187.
Chen BS, Yu-Wai-Man P, Newman NJ. Developments in the treatment of leber hereditary optic neuropathy. Curr Neurol Neurosci Rep. 2022;22:881–92.
Catarino CB, von Livonius B, Priglinger C, Banik R, Matloob S, Tamhankar MA, et al. Real-world clinical experience with idebenone in the treatment of leber hereditary optic neuropathy. J Neuroophthalmol. 2020;40:558–65.
Carelli V, Carbonelli M, de Coo IF, Kawasaki A, Klopstock T, Lagreze WA, et al. International consensus statement on the clinical and therapeutic management of leber hereditary optic neuropathy. J Neuroophthalmol. 2017;37:371–81.
Romagnoli M, La Morgia C, Carbonelli M, Di Vito L, Amore G, Zenesini C, et al. Idebenone increases chance of stabilization/recovery of visual acuity in OPA1-dominant optic atrophy. Ann Clin Transl Neurol. 2020;7:590–4.
Wan X, Pei H, Zhao MJ, Yang S, Hu WK, He H, et al. Efficacy and safety of rAAV2-ND4 treatment for Leber’s hereditary optic neuropathy. Sci Rep. 2016;6:21587.
Yu-Wai-Man P, Newman NJ, Carelli V, Moster ML, Biousse V, Sadun AA, et al. Bilateral visual improvement with unilateral gene therapy injection for Leber hereditary optic neuropathy. Sci Transl Med. 2020;12:eaaz7423.
Newman NJ, Yu-Wai-Man P, Carelli V, Moster ML, Biousse V, Vignal-Clermont C, et al. Efficacy and safety of intravitreal gene therapy for Leber hereditary optic neuropathy treated within 6 months of disease onset. Ophthalmology. 2021;128:649–60.
Newman NJ, Yu-Wai-Man P, Subramanian PS, Moster ML, Wang AG, Donahue SP, et al. Randomized trial of bilateral gene therapy injection for m.11778G>A MT-ND4 Leber optic neuropathy. Brain. 2022;146:1328–41.
Liu Y, Eastwood JD, Alba DE, Velmurugan S, Sun N, Porciatti V, et al. Gene therapy restores mitochondrial function and protects retinal ganglion cells in optic neuropathy induced by a mito-targeted mutant ND1 gene. Gene Ther. 2022;29:368–78.
Bacman SR, Gammage PA, Minczuk M, Moraes CT. Manipulation of mitochondrial genes and mtDNA heteroplasmy. Methods Cell Biol. 2020;155:441–87.
Mok BY, Kotrys AV, Raguram A, Huang TP, Mootha VK, Liu DR. CRISPR-free base editors with enhanced activity and expanded targeting scope in mitochondrial and nuclear DNA. Nat Biotechnol. 2022;40:1378–87.
Paull D, Emmanuele V, Weiss KA, Treff N, Stewart L, Hua H, et al. Nuclear genome transfer in human oocytes eliminates mitochondrial DNA variants. Nature. 2013;493:632–7.
Gorman GS, Grady JP, Turnbull DM. Mitochondrial donation-how many women could benefit? N. Engl J Med. 2015;372:885–7.
Stoke Therapeutics. Stoke therapeutics reports third quarter financial results and provides business updates. https://investor.stoketherapeutics.com/news-releases/news-release-details/stoke-therapeutics-reports-third-quarter-financial-results-and-0. Accessed 18 Oct 2022.
PYC Therapeutics. PYC Therapeutics Set To Announce Efficacy Results For Second Investigational Drug Program. https://pyctx.com/wp-content/uploads/2021/05/PYC-Therapeutics-Set-To-Announce-Efficacy-Results-For-Second-Investigational-Drug-Program.pdf Accessed 18 Oct 2022.
Goto Y. MELAS (mitochondrial myopathy, encephalopathy lactic acidosis, and stroke-like episodes): clinical features and mitochondrial DNA mutations. Nihon Rinsho. 1993;51:2373–8.
Hirano M, Ricci E, Koenigsberger MR, Defendini R, Pavlakis SG, DeVivo DC, et al. Melas: an original case and clinical criteria for diagnosis. Neuromuscul Disord. 1992;2:125–35.
Shinkai A, Shinmei Y, Hirooka K, Tagawa Y, Nakamura K, Chin S, et al. Optical coherence tomography as a possible tool to monitor and predict disease progression in mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes. Mitochondrion. 2021;56:47–51.
Latvala T, Mustonen E, Uusitalo R, Majamaa K. Pigmentary retinopathy in patients with the MELAS mutation 3243A->G in mitochondrial DNA. Graefes Arch Clin Exp Ophthalmol. 2002;240:795–801.
Hirano M, Emmanuele V, Quinzii CM. Emerging therapies for mitochondrial diseases. Essays Biochem. 2018;62:467–81.
Acknowledgements
BSC is supported by the Cambridge-Rutherford Memorial Scholarship, awarded by the Royal Society Te Apārangi—Rutherford Foundation and the Cambridge Commonwealth, European & International Trust; and the Bushell Travelling Fellowship in Medicine or the Allied Sciences, awarded by the Royal Australasian College of Physicians (RACP) Foundation. MJG acknowledges funding from the NIHR (CL-2019-18-004), Academy of Medical Sciences (SGL023\1051), Moorfields Eye Charity (GR001207), Eye Research UK (SEE 006) & ProRetina Foundation Deutschland (Pro-Re/Projekt/Gilhooley-Whitehead-Lindner.04-2021). PYWM is supported by an Advanced Fellowship Award (NIHR301696) from the UK National Institute of Health and Care Research (NIHR). PYWM also receives funding from Fight for Sight (UK), the Isaac Newton Trust (UK), Moorfields Eye Charity (GR001376), the Addenbrooke’s Charitable Trust, the National Eye Research Centre (UK), the International Foundation for Optic Nerve Disease (IFOND), the NIHR as part of the Rare Diseases Translational Research Collaboration, the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014), and the NIHR Biomedical Research Centre based at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.
Author information
Authors and Affiliations
Contributions
BSC and PYWM were responsible for the conception and design of the manuscript. BSC, JPH, MJG, and NJ were responsible for preparing the initial draft, including tables and figures. All authors contributed equally to revising the manuscript and approving the final manuscript.
Corresponding author
Ethics declarations
Competing interests
PYWM is a consultant for GenSight Biologics, Santhera/Chiesi, Stoke Therapeutics and Transine Therapeutics. All other authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Chen, B.S., Harvey, J.P., Gilhooley, M.J. et al. Mitochondria and the eye—manifestations of mitochondrial diseases and their management. Eye 37, 2416–2425 (2023). https://doi.org/10.1038/s41433-023-02523-x
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41433-023-02523-x
- Springer Nature Limited