From the Guidelines
Lowering intraocular pressure (IOP) is beneficial for patients with normal tension glaucoma (NTG), with a reasonable initial treatment goal of reducing IOP by 20% to 30% below baseline. This approach is supported by clinical trials that have shown the effectiveness of IOP reduction in slowing the progression of primary open-angle glaucoma (POAG), which includes NTG 1. Key risk factors for POAG, including NTG, include older age, African or Latino/Hispanic ethnicity, family history of glaucoma, low ocular perfusion pressure, type 2 diabetes mellitus, myopia, and thin central cornea 1.
Treatment Approaches
- IOP-lowering treatments are crucial, with options including medical, laser, and incisional surgical approaches 1.
- Adjusting computerized visual field programs and stimulus size can aid in detecting and monitoring progressive visual field loss 1.
- Computer-based imaging and stereoscopic photography provide valuable information about optic nerve status 1.
Monitoring and Follow-Up
- Regular monitoring with optical coherence tomography (OCT) is essential to detect structural changes before functional vision loss occurs.
- Clinical features of POAG, including NTG, involve an open angle on gonioscopy, glaucomatous optic nerve head (ONH) and retinal nerve fiber layer (RNFL)/macula imaging changes, and typical glaucomatous visual field defects 1.
Key Considerations
- The goal of treatment should prioritize reducing morbidity, mortality, and improving quality of life for patients with NTG.
- A multi-faceted approach, considering factors beyond elevated IOP such as vascular dysregulation, oxidative stress, and mitochondrial dysfunction, is necessary for effective management 1.
From the Research
Normal Tension Glaucoma Research
- Normal tension glaucoma (NTG) is a common form of open-angle glaucoma, with many unanswered questions regarding its mechanisms and treatment 2.
- NTG is defined as chronic open-angle glaucoma without elevated intraocular pressure or normal intraocular pressure, with normal intraocular pressure between 10 and 21 mmHg 3.
- The exact pathophysiology of NTG is not well understood, but circulatory disturbances, such as arterial hypo- and hypertension, may play a role in increasing the susceptibility of the optic nerve to intraocular pressure fluctuations and blood pressure dips 3.
Treatment of Normal Tension Glaucoma
- The primary goal of treatment is the reduction of intraocular pressure, which can stop the disease 3.
- Control of intraocular pressure remains the mainstay of managing NTG patients, but consideration must also be given to other factors, especially those that may influence perfusion of the optic nerve head 2.
- Medical and surgical interventions have been compared to no treatment, placebo, or other treatment in people with NTG, with some studies showing a beneficial effect of lowering intraocular pressure or using calcium antagonists 4.
- A prospective comparative study found that both unoprostone and latanoprost were effective in lowering intraocular pressure in NTG patients, but there were no significant differences between groups in terms of visual field loss progression or disc changes 5.
Key Findings
- NTG and primary open-angle glaucoma (POAG) represent a continuum of open-angle glaucomas, with a certain level of intraocular pressure being the predominant causative risk factor in POAG, while additional IOP-independent factors take increasing importance in NTG 2.
- Diagnosis of NTG depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visual field loss 6.
- Management of NTG follows the same principle as other chronic glaucomas, to lower the intraocular pressure by a substantial amount, enough to prevent disabling visual loss, but many NTG cases are non-progressive, and it may often be wise to determine whether the case is progressive and the rate of progression before deciding on how aggressive to be with therapy 6.