Research Profile: Nurhan Torun, MD, FRCSC

Nurhan Torun, MD, FRCSC

Assistant Professor of Ophthalmology, Harvard Medical School

Chief of Ophthalmology, BIDMC

Research Group

Marc A. Bouffard, MD
Edsel Ing, MD

Research Focus

My research in 2016 - 2017 focused on investigating newer non-invasive tests for giant cell arteritis (GCA). GCA is the most common vasculitis of the elderly and causes irreversible blindness in up to 20 percent of patients. GCA can be a diagnostic conundrum when it presents in an atypical or occult fashion. There is no highly specific biomarker for GCA to date. Blood tests for inflammation have limited sensitivity, and “seronegative” GCA can occur in up to 4 percent of patients. The 1990 American College of Rheumatology (ACR) classification criteria for GCA are not diagnostic criteria. Although TABx is an invasive and time-consuming test, most authorities feel that it remains the gold standard for the diagnosis of GCA.

Although the most common complication of GCA is visual loss, most clinical prediction algorithms for GCA do not incorporate an ocular blood flow measurement. Possible methods to assess reduction in blood flow in GCA include fluorescein angiography, oculoplethysmography, dynamic contour tonometry, and OCT angiography. Delayed choroidal filling greater than 20 seconds on fluorescein angiography is suggestive but not specific for GCA. In patients with GCA, Dr. Thomas Bosley (Johns Hopkins University) showed there is reduced ocular pulse amplitude with his pneumo-oculoplethysmography (OPG) technique. OPG is a cumbersome technique that is rarely performed nowadays.

Pascal Dynamic contour tonometry was popularized for glaucoma over the last decade. Dynamic contour tonometry (DCT) provides a digital readout of intraocular pressure as well as an estimation of the ocular pulse amplitude (OPA). The OPA is the difference in intraocular pressure during the cardiac cycle, and represents the pulsatile wave front produced by the varying amount of choroidal blood flow between systole and diastole. The DCT painlessly estimates the OPA and ocular blood flow in 7 seconds. In collaboration with a group at the University of Toronto, we hypothesized that the DCT OPA would be reduced in patients with positive TABx compared with negative TABx. All patients undergoing TABx for suspected GCA were included in this prospective, multicenter study. On univariate logistic regression, only the average ocular pulse amplitude and platelet count showed a statistically significant difference between the biopsy groups. Age, CRP, biopsy length, and jaw claudication did not show a statistically significant difference on univariate logistic regression. We found OPA to be inversely related to the risk of GCA and to be a statistically significant predictor of positive TABx; we concluded that it can be incorporated as part of a prediction rule for GCA (Figure 1).

In addition, our project “Oculomotor Assessment as a Potential Biomarker for Huntington’s Disease,” for which I am collaborating with Dr. Wasim Malik (Massachusetts General Hospital) and Dr. Samuel Frank (BIDMC), was funded by the Huntington’s Disease Society of America. The major goals of this project are to develop a novel eye-movement based paradigm for assessment, diagnosis and progression monitoring of Huntington’s disease (HD), using a convenient and portable eye-tracking system, and to develop a novel quantitative biomarker for early diagnosis of HD, leading to better detection, improved clinical management, and therapy development for this disease. 

Accomplishments 2016-2017

  • I was selected for the Physician Leadership Program at BIDMC for 2017-2018.
  • In July 2017, I was invited to Waterville, Maine, to give the following four one-hour talks at the Lancaster Course, one of the largest ophthalmology review courses given to national and international ophthalmologists and residents. I was asked to deliver the same talks again in July 2018:
    Pearls and Pitfalls of Neuro-ophthalmic Examination
    Neuro-ophthalmic Emergencies
    Central Processing Disorders of Vision
    Ocular Myasthenia and Extraocular Myopathies
  • I was the primary thesis advisor to Anh-Dao Cheng (former Boston University MSc candidate, currently enrolled in Boston University Medical School) for her MSc Thesis: Optic Nerve Atrophy: How Sensitive is MRI Determined Optic Nerve Size Compared to Optical Coherence Tomography (OCT)?
  • I accepted an invitation to give a talk on Electrophysiological testing in Neuro-ophthalmology at the New England Ophthalmological Society Meeting in June 2018.
  • I was invited to give Thorndike lecture series talk to internal medicine residents at BIDMC on Ophthalmic Emergencies in September 2017.
  • I was the guest speaker at Parkinson’s Disease Baby Boomer Support Group in June 2017 and discussed vision related problems in Parkinson’s Disease.

Teaching, Training, and Education

I am involved in didactic and bedside teaching of residents. I developed a curriculum of 12 core neuro-ophthalmology lectures that I delivered each year to neurology residents at BIDMC. I supervise ophthalmology residents in my comprehensive ophthalmology clinics and while doing on-call duty. I am actively involved in surgical teaching of ophthalmology residents as well.

I am also one of the instructors teaching the Core Medicine Ophthalmology Course to Harvard Medical School students in the Longwood Medical Area; this involves 8 to 10 two-hour lectures each year.

Since 2015, I have been one of the Neuro-ophthalmology Fellowship Preceptors for the Harvard Neuro-ophthalmology Fellowship.

Selected Research Support

Oculomotor Assessment as a Potential Biomarker for Huntington’s Disease; Huntington’s Disease Society of America, 2016- 2018; Co-investigators: Nurhan Torun, MD and Samuel Frank, MD (PI: Wasim Q. Malik, PhD)

Selected Publications

Gaier ED, Torun N. The enigma of NAION: An update for the comprehensive ophthalmologist. Curr Opin Ophthalmol 2016;27(6):498-504.

Bouffard MA, Nathavitharana R, Yassa D, Torun N. Retreatment with ethambutol after toxic optic neuropathy. J Neuroophthalmol 2017;37(1):40-42.

Bouffard MA, Torun N. Divergence Palsy due to Divalproex and Oxcarbazepine. Clin Neuropharmacol 2017;40(3):154-155.

Bouffard MA,  Cornblath W,  Rizzo III JF, Lee MS, DeLott LB, Eggenberger E, Torun N. Transient Monocular Vision Loss Upon Awakening: A Benign Amaurosis Phenomenon. J Neuroophthalmol 2017;37(2):122-125.

Ravindran K. Schmalz P, Torun N, Ronthal M, Chang YM, Thomas AJ. Angiographic Findings in the Tolosa-Hunt Syndrome and Resolution after Corticosteroid Treatment. Neuroophthalmology 2017;42(3):159-163.

Ing E, Pagnoux C, Tyndel F, Sundaram A, Hershenfeld S, Ranalli P, Chow S, Le T, Lutchman C, Rutherford S, Lam K, Bedi H, Torun N. Lower dynamic contour tonometry ocular pulse amplitude is associated with biopsy-proven giant cell arteritis. Can J Ophthalmol 2018;53(3):215-221.