Updates on Normal Tension Glaucoma Management

Research Article

Austin Ophthalmol. 2020; 4(1): 1013.

Updates on Normal Tension Glaucoma Management

Zarei R1, Fakhraie G1, Mortazavi M1*, Vahedian Z1, Mirghorbani M1, Masoumi A1 and Khabazkhoob M2

¹Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran

²Noor Eye Research Center, Noor Eye Hospital, Tehran, Iran

*Corresponding author: Mehdi Mortazavi, Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran; Email: smmortazavi63@yahoo.com

Received: January 25, 2020; Accepted: March 03, 2020; Published: March 10, 2020

Abstract

Purpose: To review the recent publications and updates on the treatment of normal tension glaucoma (NTG).

Design: Systematic review.

Methods: Relevant publications were identified in Medline, Scopus, Embase and Cochrane using the keywords. Results were reviewed, tabulated and summarized.

Results: The literature focuses on prostaglandin analogues as the first line of treatment in NTG. However, there are several reports on the use of beta blockers, a2 agonists and combination drugs. Fifteen papers reporting the outcome of surgical treatment of NTG met our inclusion criteria. There is an increasing trend toward the use of neuroprotective agents to stop the progressive glaucomatous damage in NTG. Five papers were identified reporting the role of neuroprotection in this type of glaucoma.

Conclusion: The present review summarizes the treatment options for patients with NTG. Medical treatment remains the first choice. However, there are several surgical options that can be considered in refractory cases that require further intraocular pressure (IOP) reduction. Neuroprotection is an interesting field of research in NTG that might offer new hopes to overcome this debilitating condition in the future.

Keywords: Glaucoma; Prostaglandin; Neuroprotection

Introduction

Normal tension glaucoma (NTG) is a type of open-angle glaucoma with typical glaucomatous optic nerve head damage, characteristic visual field defects, progressive changes on follow-up examinations and maximum intraocular pressure (IOP) less than 21mmHg [1]. Risk factors of NTG include: 1: Older age; 2: Female gender; 3: East Asian ethnicity; 4: Low central corneal thickness [2]. Moreover, signs of vascular dysregulation (such as cold hands and feet, migraine headache and systemic hypertension or hypotension) are more likely to be found in patients with NTG. Other pertinent findings may include a history of sleep apnea or arterial obstructive disease [2]. Flammer syndrome is a recently described clinical condition. Patients with this clinical entity may suffer from a group of symptoms, which are related to blood flow dysregulation such as cold hands and/ or feet, increased sensitivity to pain, decreased sensation of thirst, migraine and tinnitus [3]. It is found that impaired blood flow to the optic nerve head and normal tension glaucoma is more common in patients with Flammer syndrome [4].

Goldman applanation tonometry, stereoscopic biomicroscopy of optic nerve head, gonioscopy, optical coherence tomography and visual field analysis are essential for diagnosis of NTG. Early diagnosis of NTG is of paramount importance due to its lack of symptoms until advanced stages [2].

Until now, IOP remains the only modifiable risk factor for the treatment of glaucoma. Although NTG is defined by an IOP that is in the normal range, IOP still plays an important role in the pathogenesis of NTG, and lowering IOP is effective in slowing the progression of glaucomatous damage [2]. Results of Early Manifest Glaucoma Trial revealed that glaucoma progression was decreased by 10% with each mmHg reduction in IOP [5]. Collaborative Normal Tension Glaucoma Study showed that IOP reduction of 30% slows the progression of NTG [6]. Several hypotensive medications have become available in the market in recent years. Previous studies have shown that prostaglandin analogues are the effective agents for lowering IOP in NTG patients, with mean IOP reduction of 20% [7]. Timolol has the same efficacy, although it may have greater IOP reduction at trough than at peak [8]. Surgical intervention is the next line of treatment should the maximum medical therapy fails to slow the progression. Recently, the role of neuroprotective agents is highlighted in prevention of retinal ganglion cell (RGC) loss.

In this paper, we aim to review the most recent publications regarding the treatment of NTG.

Methods

We searched four databases including Medline, Scopus, Embase and Cochrane for these keywords; “NTG”, “normal tension”, “normal pressure”, “low tension”, “low pressure”, “treat*”, “therap*”, “medication” and “manag*”. Search results were confined to papers published from 2011 to 2017. 1162 articles identified in the preliminary search, and 505 items were duplicates. Remaining 657 papers underwent primary screen for relevant subjects and 301 items were chosen. Abstracts were studied carefully, and 60 articles were selected for full-text evaluation and conducting a review. The final selection was rechecked by another reviewer to prevent any missing or improper selection. We included only papers with full-text or abstract in English.

IOP lowering medications

The first line of treatment in NTG patients is antiglaucoma medication to slow the progression of visual field and structural changes. Table 1 summarizes the results of studies investigating the role of medical therapy in NTG.