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Normal Tension Glaucoma Summary

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Title: Normal Tension Glaucoma Summary
Authors:William Clark, BA; Brian Stagg, MD
Date: 05/22/20
Keywords/Main Subjects: Glaucoma, Open-Angle Glaucoma, Normal Tension Glaucoma

• Definition: Normal Tension Glaucoma (NTG) is a form of glaucoma with open anterior chamber angles, characteristic optic neuropathy and visual field loss in the setting of non-elevated (<22 mmHg) intraocular pressure (IOP).¹
• Etiology: Proposed mechanisms for NTG include vascular dysregulation, increased sensitivity to normal IOP, and elevated translaminar pressure.²
• Differential diagnosis: NTG is often overlooked or misdiagnosed. Identifying NTG requires clinical suspicion and vigilant optic nerve examination. As NTG is a diagnosis of exclusion, it is imperative to investigate multiple etiologies for optic nerve cupping and visual field loss.³
• Evaluation: A thorough history should be obtained. Baseline examination includes best-corrected visual acuity, pupillary response testing, IOP measurement, slit lamp examination, gonioscopy, dilated fundus examination and visual field testing.³
• Key findings: IOP measurements should be below 22 mmHg. Optic disc evaluation often reveals focal rim notching, splinter (Drance) hemorrhages near the optic nerve head, and localized retinal nerve fiber layer atrophy.⁴ Visual field testing often reveals deep, focal scotomas close to fixation.⁵
• Management: A 30% IOP reduction has been shown to lower the risk of visual field progression in NTG.⁶ IOP-lowering medications, laser trabeculoplasty and incisional surgery are effective forms of therapy.⁷

References

1. Allingham RR, Damji KF, Freedman SF, Freedman SF, Rhee DJ, Shields MB. Shields Textbook of Glaucoma. Wolters Kluwer; 2010. Accessed April 6, 2020. http://ebookcentral.proquest.com/lib/eastcarolina/detail.action?docID=3418252
2. Killer H, Pircher A. Normal tension glaucoma: review of current understanding and mechanisms of the pathogenesis. Eye. 2018;32(5):924-930. doi:10.1038/s41433-018-0042-2
3. Bagheri N, Wajda B, Calvo C, Durrani A. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease. Wolters Kluwer; 2016. Accessed April 28, 2020. http://ebookcentral.proquest.com/lib/eastcarolina/detail.action?docID=4931402
4. Hendrickx KH, van den Enden A, Rasker MT, Hoyng PF. Cumulative incidence of patients with disc hemorrhages in glaucoma and the effect of therapy. Ophthalmology. 1994;101(7):1165-1172. doi:10.1016/s0161-6420(94)31192-4
5. Caprioli J, Spaeth GL. Comparison of visual field defects in the low-tension glaucomas with those in the high-tension glaucomas. Am J Ophthalmol. 1984;97(6):730-737. doi:10.1016/0002-9394(84)90505-1
6. Comparison of glaucomatous progression between untreated patients with normal-tension glaucoma and patients with therapeutically reduced intraocular pressures. Collaborative Normal-Tension Glaucoma Study Group. Am J Ophthalmol. 1998;126(4):487-497. doi:10.1016/s0002-9394(98)00223-2
7. Prum BE, Rosenberg LF, Gedde SJ, et al. Primary Open-Angle Glaucoma Preferred Practice Pattern(®) Guidelines. Ophthalmology. 2016;123(1):P41-P111. doi:10.1016/j.ophtha.2015.10.053

Faculty Approval by: Brian Stagg, MD
Identifier: Moran_CORE_27930
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