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Show Letters to the Editor on our data "lowering IOP may not be beneficial in preventing visual loss in normotensive eyes with ONHD." We believe the strength of our statement is commensurate with the level of evidence provided by our data and does not hinder future studies from further evaluating this issue from a different perspective. Dr. Katz correctly noted that the statistical analyses performed "by eye" did not take into account that the measurements involved are likely correlated between eyes of a single subject. The data were thus reanalyzed using 2 methods to account for intrasubject correlation, reducing the sample to one eye per subject and using mixed effects models with a random effect by the subject. For most tests reported in our manuscript, the new analyses came to the same conclusions. Tests with nonsignificant results remained nonsignificant. In fact, P values generally increased with the reanalysis. The significant findings of the association of ocular hypertension (IOP $ 22 mm Hg) and less depressed perimetric mean deviation were found to be nonsignificant on reanalysis. However, as noted in the text, these results were suspect already due to the low sample of patients with ocular hypertension. We are confident that our overall statistical conclusions are valid. Dr. Katz portrays ONHD patients as medically vulnerable in the sense that there are few reasonable treatment options and states that "concluding that one should not offer these therapies (IOP lowering drops) to our patients with ONHD is without merit and potentially a disservice to patients." The notion that our study concluded that providers should not offer IOP lowering therapies in ONHD is erroneous and does not appear in our manuscript text. In fact, the study authors as a group will, in certain circumstances (e.g., significant progressive visual field defects, moderate to severe visual field loss, and ocular hypertension), discuss with and offer IOP lowering therapies to patients. Although we agree that, in general, topical IOP lowering treatments are safe, one must consider that many of the 1%-2% of the population with ONHD are diagnosed in childhood and that there is no endpoint for treatment. Those who have no significant progression will believe the drops are working, whereas those who have visual field progression may be tempted to "double down" on IOP lowering by seeking out multiple drops or high-risk incisional glaucoma surgery. The financial burden of drops can also become significant over decades of use. The notion of treatment without supportive evidence can quickly become a slippery slope. We believe that the lack of definitive evidence against the efficacy of IOP lowering medications in ONHD-related optic neuropathy should not serve as a carte blanche for providers to prescribe treatment under the flawed logic that doing something is better than doing nothing. Historically, the appeal to cure has been used to support other "relatively inexpensive" and safe treatments of questionable efficacy including vision therapy for a broad range of ocular motility disorders and antibiotics for chronic Lyme disease. Neuro-Ophthalmology in South India (where consultation and surgeries [mainly cataract] are free). In our retrospective analysis from January 2017 to December 2017, there were 143, 946 referrals to various specialty clinics, of which 9,238 (6.4%) were referred for neuroophthalmic evaluation. Of these, 7,387 patients were referred from paying hospitals and 1851 were referred from free direct and camp sections. For our analysis, we included only the paying section referrals, of which 1851 patients (25%) were excluded as they turned out to be non-neuroophthalmic cases, compared to 16% in the study by Dhiman et al. Thus, our patient cohort comprised 5,402 patients. We compared our results with those of Dhiman et al. Optic nerve disorders were seen in 64.6% (n = 3,511) W e were greatly interested in the article by Dhiman et al (1) discussing their experience with neuroophthalmology in a central government-funded tertiary eye care hospital in North India. We wish to share our experience from a private nongovernmental organization (NGO) tertiary eye care hospital in South India. Our hospital offers services to patients in 3 tiers as per their choice: (1) paying section (where patient pays for the services); (2) free direct section (where consultation is free and the surgeries are steeply subsidized); (3) camp section 144 Michael Shyne, MS Biostatistical Design and Analysis Center, University of Minnesota, Minneapolis, Minnesota Gregory P. Van Stavern, MD Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri Kaitlyn W. Nolan, MD Michael S. Lee, MD Collin M. McClelland, MD Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota The authors report no conflicts of interest. Letters to the Editor: J Neuro-Ophthalmol 2019; 39: 142-145 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Letters to the Editor of our patients compared to 63.8% (n = 1,020) in their study. We saw 84.6% (n = 2,971) of optic nerve disorders without disc edema and 15.4% (n = 540) with disc edema compared to 67% (n = 635) and 33% (n = 335), respectively, in their study. The most common optic nerve disorder without disc edema was traumatic optic neuropathy seen in 13% (n = 383) compared to 27.7% (n = 190) in their study. In the optic disc edema group, ischemic optic neuropathy was present in 34.4% (n = 186) of cases compared to 37.6% (n = 126) in their study. Papilledema was seen in 23% (n = 124) compared to 23.2% (n = 78) in their study. The most common cranial nerve palsy occurred with the sixth nerve in 44.3% (n = 314), followed by third nerve in 26% (n = 184), fourth nerve in 11.3% (n = 80), and seventh nerve in 18.4% (n = 130). Dhiman et al reported involvement of sixth, third, fourth, and seventh nerves with frequencies of 44%, 21.9%, 20.1%, and 14%, respectively. Our comparative analysis demonstrated that the occurrence of neuro-ophthalmic diseases in 2 diverse tertiary care centers in North India (central government funded) and Letters to the Editor: J Neuro-Ophthalmol 2019; 39: 142-145 South India (NGO) is quite similar. We strongly agree with Dhiman et al that in a vast country like ours, with a population of over a billion people, more subspecialtytrained neuro-ophthalmologists are needed. Virna M. Shah, DO Venkatapathy Narendran, DNB Department of Neuro Ophthalmology, Postgraduate Institute of Ophthalmology, Aravind Eye Hospital, Coimbatore, India The authors report no conflicts of interest. REFERENCE 1. Dhiman R, Singh D, Gantayala SP, Ganesan VL, Sharma P, Saxena R. Neuro-Ophthalmology at a tertiary eye care centre in India. J Neuroophthalmol. 2018;38:308-311. 145 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
