Direct OPTOS Nerve Size Determination of Prevalent Optic Nerve Hypoplasia in Alaska
Received 16 December 2019
Accepted for publication 4 February 2020
Published 20 February 2020 Volume 2020:14 Pages 491—499
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 3
Editor who approved publication: Dr Scott Fraser
Andrew W Arnold,1 Andrew M Eller,2 Kyle A Smith,3 Robin L Grendahl,4 R Kevin Winkle,4 Robert W Arnold4
1Pacific Northwest University College of Osteopathic Medicine, Yakima, WA, USA; 2University of Arkansas Medical School, Little Rock, AR, USA; 3Accurate Vision Center, Anchorage, AK, USA; 4Alaska Children’s Eye & Strabismus, Anchorage, AK 99508, USA
Correspondence: Robert W Arnold
Alaska Children’s Eye & Strabismus, 3500 Latouche #280, Anchorage, AK 99508, USA
Tel +1 907 561-1917
Fax +1 907 563-5373
Background: Optic nerve hypoplasia (ONH), one of the most common causes of pediatric blindness in developed countries, has been difficult to directly quantify. We sought to measure optic nerve size in Alaskan pediatric patients with optic nerve hypoplasia using ultra-widefield fundus imaging.
Methods: Adult and pediatric patients underwent conventional ultra widefield fundus imaging (OPTOS, Dunfermline, Scotland) with manual image processing to determine optic nerve size validated against refractive error and nystagmus and compared to optical spectral domain tomography. De-identified cases were then compared relative to visual acuity and birth prevalence.
Results: In Alaska’s only pediatric ophthalmology outreach clinic, 108 cases of ONH less than 20 years old were clinically identified with 80 having ultra-widefield analysis. Median horizontal optic nerve diameter for 135 normals was 1.70 (95% C.I. 1.49, 2.14) whereas in patients clinically diagnosed with optic nerve hypoplasia was 1.23 (95% C.I 0.38, 1.45). Visual acuity (20/y) was related to horizontal optic nerve diameter (x) by y = 187 x-4.1. Horizontal nerve diameter h could be estimated from vertical nerve diameter v by h = 0.73v + 0.3 even in nystagmus patients. From 108 with ONH, 6 had threshold retinopathy of prematurity, 12 profound nystagmus, 32 legally blind, 6 with septo-optic dysplasia, and 5 with fetal alcohol syndrome. ONH is very prevalent in Alaska occurring at least 8– 10 per 10,000 births.
Conclusion: Compared to vertical diameter, horizontal diameter was more distinctive of optic nerve hypoplasia and more perturbed by nystagmus. Both were independent of refractive error. When hand-held, spectral domain OCT is not convenient, ultra-widefield fundus analysis is recommended for direct estimation of optic nerve size in children and adults. Optic nerve hypoplasia is prevalent in Alaskan children.
Keywords: pediatric blindness, optic nerve, birth defect, dysmorphic, retinopathy of prematurity, septo-optic dysplasia, OPTOS
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