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AUTHOR REPLY
Ahead of print publication  

Reply to “the spectrum of neuro-ophthalmologic involvement in mitochondrial disorders is broad”


1 Department of Ophthalmology, Royal Perth Hospital; Department of Ophthalmology, Sir Charles Gairdner Hospital; Department of Ophthalmology, Perth's Children's Hospital, Perth, WA, Australia
2 Department of Ophthalmology, Royal Perth Hospital; Department of Neurology, Fiona Stanley Hospital; Department of Neurology, Joondalup Health Campus, Perth, WA, Australia, Australia
3 Department of Ophthalmology, Emory University School of Medicine; Department of Neurology, Emory University School of Medicine; Department of Neurological Surgery, Emory University School of Medicine, Atlanta, GA, USA

Date of Submission06-Apr-2021
Date of Acceptance05-May-2021
Date of Web Publication16-Jul-2021

Correspondence Address:
Nancy J Newman,
Emory Eye Center, Neuro-Ophthalmology Unit, 1365B Clifton Road NE, Atlanta, GA 30322
USA
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjo.tjo_19_21



How to cite this URL:
Lock JH, Irani NK, Newman NJ. Reply to “the spectrum of neuro-ophthalmologic involvement in mitochondrial disorders is broad”. Taiwan J Ophthalmol [Epub ahead of print] [cited 2021 Dec 8]. Available from: https://www.e-tjo.org/preprintarticle.asp?id=321677



Dear Editor,

We thank Dr. Finsterer for his interest in our manuscript. As dysfunction of the mitochondria likely represents the final common pathway of nearly every pathophysiologic process, it is not surprising that mitochondrial disorders can present with a wide variety of common and uncommon ophthalmologic and neurologic involvement. Our review, which was limited in space by editorial constraints, was meant to highlight those specific neuro-ophthalmologic manifestations that should raise suspicion for underlying mitochondrial disorders. We are happy to briefly address a few of Dr. Finsterer's points and the readership is directed to the references included in both letters for further discussion of these topics.

While we agree with the author that cataracts and glaucoma may occur in patients with mitochondrial disorders, these are unarguably two of the most common presentations to the eye clinic and far more likely to be coincidental than related to an occult mitochondrial disorder, especially when presenting in isolation. Although it is plausible that mitochondrial dysfunction underlies the complex pathophysiology of glaucoma, it is much more important for the general ophthalmologist to consider the diagnosis of a mitochondrial disorder such as dominant optic atrophy when assessing a patient with excavated cupping, but also pallor of the retained neuroretinal rim, temporal retinal nerve fiber thinning cecocentral scotomas and normal intraocular pressures, rather than diagnosing the patient with normal-tension glaucoma.

Megalocornea, keratoconus, choroidal atrophy and pupillary dysfunction when associated with certain neuro-ophthalmic, neurologic or systemic signs should certainly prompt clinicians to consider underlying mitochondrial disorders.[1],[2],[3] However, in isolation, they are unlikely to represent a mitochondriopathy.

We agree with Dr. Finsterer that nystagmus can be a manifestation of mitochondrial disorders which affect vision (especially in early childhood) or those portions of the brain involved in gaze holding or vestibular function.[4] However, in isolation, nystagmus is exceedingly rare as a presenting feature of mitochondrial disorders[5],[6],[7],[8] and should in fact prompt evaluation for alternative etiologies, both acquired and inherited.

Finally, migraine is a very common disabling neurobiological headache disorder with an estimated 1-year prevalence of 15% worldwide.[9] We agree that migraines with aura when associated with other discriminating features such as retrochiasmal visual field loss, strokes, seizures, hearing loss, cardiomyopathy, diabetes mellitus and short stature should prompt a workup for potential mitochondrial disorders and this has been highlighted in our article. However, with such a high prevalence of migraine in the general population, evaluation of an occult mitochondriopathy in migraineurs without other suspicious features would be low yield.

Within the space constraints of our manuscript, our focus was to distinguish those neuro-ophthalmologic presentations that should prompt the readership to consider underlying mitochondrial diseases in the appropriate clinical context.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors declare that there are no conflicts of interests of this paper.



 
  References Top

1.
Vallabh NA, Romano V, Willoughby CE. Mitochondrial dysfunction and oxidative stress in corneal disease. Mitochondrion 2017;36:103-13.  Back to cited text no. 1
    
2.
Schrier SA, Falk MJ. Mitochondrial disorders and the eye. Curr Opin Ophthalmol 2011;22:325-31.  Back to cited text no. 2
    
3.
Finsterer J, Zarrouk-Mahjoub S, Daruich A. The Eye on Mitochondrial Disorders. J Child Neurol 2016;31:652-62.  Back to cited text no. 3
    
4.
Rose LV, Rose NT, Elder JE, Thorburn DR, Boneh A. Ophthalmologic presentation of oxidative phosphorylation diseases of childhood. Pediatr Neurol 2008;38:395-7.  Back to cited text no. 4
    
5.
Hvid K, Nissen KR, Bayat A, Roos L, Grønskov K, Kessel L. Prevalence and causes of infantile nystagmus in a large population-based Danish cohort. Acta Ophthalmol 2020;98:506-13.  Back to cited text no. 5
    
6.
Bertsch M, Floyd M, Kehoe T, Pfeifer W, Drack AV. The clinical evaluation of infantile nystagmus: What to do first and why. Ophthalmic Genet 2017;38:22-33.  Back to cited text no. 6
    
7.
Widgren P, Hurme A, Falck A, Keski-Filppula R, Remes AM, Moilanen J, et al. Genetic aetiology of ophthalmological manifestations in children-a focus on mitochondrial disease-related symptoms. Acta Ophthalmol 2016;94:83-91.  Back to cited text no. 7
    
8.
Fahnehjelm KT, Olsson M, Naess K, Wiberg M, Ygge J, Martin L, et al. Visual function, ocular motility and ocular characteristics in patients with mitochondrial complex I deficiency. Acta Ophthalmol 2012;90:32-43.  Back to cited text no. 8
    
9.
GBD 2016 Headache Collaborators. Global, regional, and national burden of migraine and tension-type headache, 1990-2016: Asystematic analysis for the Global Burden of Disease Study 2016. Lancet Neurol 2018;17:954-76.  Back to cited text no. 9
    




 

 
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