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Hurvitz Brain Sciences Program

SRI Programs

Stephan Ong Tone
Dr. Stephan Ong Tone, MDCM, PhD, FRCSC

Clinician-Scientist
Specialist of Diseases & Surgery of the Cornea, Anterior Segment & Cataracts
Assistant Professor, Department of Ophthalmology and Vision Sciences Assistant Professor, Department of Laboratory Medicine and Pathobiology Associate Graduate Faculty, Department of Laboratory Medicine and Pathobiology

Sunnybrook Health Sciences Centre
2075 Bayview Ave., Room A3-38
Toronto, ON
M4N 3M5

Phone: 416-480-5340
Fax: 844-222-4521

Clinical Profile

Administrative assistant: Paige Machat 
Phone: 416-480-5340

Ophthalmic technician: Cherrie Zhang

Surgical coordinator: Jennifer Chee
Phone: 416-480-6100 ext. 1696

Biography:

Dr. Ong Tone is a fellowship-trained clinician-scientist in Cornea and External Diseases at Sunnybrook Health Sciences Centre and Sunnybrook Research Institute, and an assistant professor at the University of Toronto. Dr. Ong Tone specialized in the diagnosis and treatment of cataracts, diseases of the cornea, anterior segment and external eye. Dr. Ong Tone performs complex cataract surgery, anterior segment surgery, corneal crosslinking, pterygium excision, ocular surface reconstruction, and corneal transplantation including penetrating keratoplasty (PKP), deep anterior lamellar keratoplasty (DALK), Descemet’s stripping endothelial keratoplasty (DSEK), Descemet’s membrane endothelial keratoplasty (DMEK), and Descemet’s stripping only (DSO).

Dr. Ong Tone completed his BSc, MDCM and PhD in Neurological Sciences at McGill University. He then went on to complete his Ophthalmology residency at the University of Toronto, where he served as co-chief resident and became a Fellow of the Royal College of Surgeons of Canada in Ophthalmology. Dr. Ong Tone completed a two year clinical-research fellowship in Cornea, External Disease and Refractive Surgery at Massachusetts Eye and Ear, Harvard Medical School, where he served as co-chief Cornea fellow. During his fellowship, he received numerous awards including the 2018 Shire Research Scholarship, 2019 Claes H. Dohlman MD, PhD, Fellowship Award, and 2019-2020 Abelson Family Fellowship Award that recognize outstanding clinician-scientist trainees. Dr. Ong Tone has presented his clinical and basic science research at numerous international meetings and most recently was awarded Best Paper in Cornea at the 2019 American Academy of Ophthalmology Annual Meeting for his work on corneal endothelial cell migration in Fuchs endothelial corneal dystrophy (Fuchs dystrophy).

Dr. Ong Tone’s research interests include understanding the mechanisms that regulate and maintain a normal and healthy corneal endothelium, and investigating diseases such as Fuchs dystrophy, that affect the corneal endothelium. Dr. Ong Tone’s research aims to understand what causes Fuchs dystrophy, and what regulates corneal endothelial cell migration in Fuchs dystrophy. To answer these questions, he has developed a new method of observing the movement of corneal endothelial cells from tissues that have been removed from Fuchs dystrophy patients during corneal transplant surgery. Furthermore, Dr. Ong Tone tries to understand what makes the movement different between patients including genetics, biological sex, and other cell signaling pathways. Overall, with a greater understanding of Fuchs dystrophy and corneal endothelial cell biology, potential new therapies and regenerative treatments can be developed aimed at curing Fuchs dystrophy and other causes of corneal blindness.

Research Profile

Research administrative assistant: Sue Santillo
Phone: 416-480-5504
Email: sue.santilo@sunnybrook.ca
Lab website: www.ongtonelab.com

Education:

  • BSc in Anatomy and Cell Biology, 2005, McGill University, Canada
  • PhD in Neurological Sciences, 2011, Montreal Neurological Institute, McGill University, Canada
  • MDCM, 2013, Faculty of Medicine, McGill University, Canada
  • Ophthalmology Residency, 2018, Department of Ophthalmology and Vision Sciences, University of Toronto, Canada
  • Fellow of the Royal College of Physicians and Surgeons of Canada, 2018
  • Clinical-Research Fellowship in Cornea, External Eye Diseases and Refractive Surgery, 2020, Massachusetts Eye and Ear, Harvard Medical School, USA

Appointments and Affiliations:

  • Clinician-Scientist, Biological Sciences Platform, Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute
  • Cornea Specialist, Sunnybrook Health Science Centre
  • Assistant Professor, Department of Ophthalmology and Vision Sciences, University of Toronto
  • Assistant Professor, Department of Laboratory Medicine and Pathobiology
  • Associate Graduate Faculty, Department of Laboratory Medicine and Pathobiology

Research Foci:

  • Fuchs endothelial corneal dystrophy
  • Regeneration of the corneal endothelium
  • Endothelial to mesenchymal transition of the corneal endothelium
  • Cellular migration of corneal endothelial cells
  • Genetics of Fuchs endothelial corneal dystrophy

Research Summary:

The corneal endothelium (CE) is the inner layer of the cornea that plays a key role in maintaining the clarity of the cornea, and thus keeping vision clear. The CE is composed of corneal endothelial cells (CECs) that rest on a specialized membrane called Descemet’s membrane. Damage to these CECs results in a decreased ability to pump fluid out of the cornea, which leads to fluid accumulation in the cornea, reduction in vision, and eye pain. Fuchs endothelial corneal dystrophy (FECD) is the most common disease of the CE affecting approximately 4 per cent of the population over the age of 40 years, and is also the leading indication for corneal transplantation worldwide. FECD is a typically age-related late-onset disease with a female predilection characterized by CEC death and the formation of abnormal collagen deposits called guttae. There are limited options for the treatment of FECD, which usually involves surgical intervention with a corneal transplant. Recently, a surgical technique termed Descemet’s Stripping Only (DSO) has been developed whereby the abnormal central CE is removed without replacing it with a transplant. The cornea clears as result of the healthier and normal-appearing CECs migrating from the periphery towards the center of the cornea. However, despite the importance of cell migration in DSO and FECD, little is known about what controls this process.

Dr. Ong Tone’s research interests include understanding the mechanisms that regulate and maintain a normal and healthy CE, and investigating diseases such as FECD. Dr. Ong Tone’s research aims to understand what causes FECD, and what regulates CEC migration in FECD. To answer these questions, he has developed a novel live imaging technique to observe the movement of CECs from tissues that have been collected from FECD patients during corneal transplant surgery. Furthermore, Dr. Ong Tone tries to understand what makes CEC behaviour different between patients including genetics (TCF4 genetic mutation), biological sex, and other cell signalling pathways such as the endothelial-to-mesenchymal transition pathway. Overall, with a greater understanding of FECD pathogenesis and CEC biology, potential new therapies and regenerative treatments can be developed aimed at curing FECD and other causes of corneal blindness.

Selected Publications:

See current publications list at PubMed.

  1. Ong Tone S, Wylegala A, Böhm M, Melangath, G, Deshpande, N, Jurkunas UV. Increased corneal endothelial cell migration in Fuchs endothelial corneal dystrophy: A live cell imaging study.Ophthalmology Science. 2021 March 9 https://doi.org/10.1016/j.xops.2021.100006
  2. Ong Tone S, Kocaba V, Böhm M, Wylegala A, White TL, Jurkunas UV. Fuchs endothelial corneal dystrophy: The vicious cycle of Fuchs pathogenesis. Prog Retin Eye Res. 2020 May 8:100863. doi: 10.1016/j.preteyeres.2020.100863. Epub ahead of print. PMID: 32438095; PMCID: PMC7648733
  3. Ong Tone S, Wylegala A, Boehm M, Melangath G, Jurkunas UV; Increased corneal endothelial cell migration in Fuchs endothelial corneal dystrophy, with or without TCF4 repeat expansion. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1188
  4. Liu C, Miyajima T, Melangath G, Miyai T, Vasanth S, Deshpande N, Kumar V, Ong Tone S, Gupta R, Zhu S, Vojnovic D, Chen Y, Rogan EG, Mondal B, Zahid M, Jurkunas UV. Ultraviolet A light induces DNA damage and estrogen-DNA adducts in Fuchs endothelial corneal dystrophy causing females to be more affected. Proc Natl Acad Sci U S A. 2020 Jan 7;117(1):573-583. doi: 10.1073/pnas.1912546116. Epub 2019 Dec 18. PMID: 31852820; PMCID: PMC6955350.
  5. Ong Tone S, Bruha MJ, Böhm M, Prescott C, Jurkunas U. Regional variability in corneal endothelial cell density between guttae and non-guttae areas in Fuchs endothelial corneal dystrophy. Can J Ophthalmol. 2019 Oct;54(5):570-576. doi: 10.1016/j.jcjo.2018.12.009. Epub 2019 Jun 17. PMID: 31564347; PMCID: PMC6776238.
  6. Ong Tone S, Melangath G, Deshpande N, Jurkunas UV; Immortalization of Fuchs Endothelial Corneal Dystrophy (FECD) Corneal Endothelial Cells (CEnC) Retains TCF4 Repeat Expansion. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2174.