Glaucoma: Intraocular Pressure, Vision, Symptoms, and Treatment

Glaucoma is a group of diseases characterized by progressive damage to the optic nerve, which can lead to irreversible vision loss. Although there are many factors influencing the development and progression of glaucoma, elevated intraocular pressure (IOP) is the only clinically significant and modifiable risk factor [2, 4]. Understanding the mechanisms of development, timely diagnosis, and adequate treatment are critical for preserving vision.

What is glaucoma and how does it develop?

Glaucoma is defined as an optic neuropathy, meaning damage to the optic nerve, the cause of which is not fully established [2]. The disease is based on an imbalance between the production and outflow of aqueous humor — the clear fluid that fills the anterior and posterior chambers of the eye. Aqueous humor is produced by the ciliary processes and leaves the eye via two main pathways: the trabecular (conventional) and the uveoscleral (unconventional) [4].

Impaired outflow of aqueous humor, most often via the conventional pathway, leads to an increase in IOP [4]. This elevated pressure is the primary risk factor in the pathogenesis of glaucoma, causing damage to the retina and progressive degeneration of the optic nerve, which can ultimately lead to blindness [4]. It is important to note that up to 40% of patients may develop glaucoma without an obvious increase in IOP, which highlights the complexity of the disease and the presence of other risk factors [2].

Symptoms of glaucoma: When to sound the alarm?

The insidious nature of glaucoma lies in the fact that it is often asymptomatic in the early stages. Vision loss occurs gradually, starting from the peripheral fields, and the patient may not notice changes until the disease reaches an advanced stage.

The main symptoms that may indicate glaucoma or its complications include:

• Gradual narrowing of the visual field (tunnel vision).
• Appearance of halos around light sources.
• Blurred vision.
• Pain or discomfort in the eye (especially during an acute glaucoma attack).
• Redness of the eye.

In rare cases, glaucoma can be caused by complications after other ophthalmic surgeries. For example, Uveitis-Glaucoma-Hyphema (UGH) syndrome is a rare complication after cataract surgery caused by mechanical friction between the intraocular lens (IOL) and adjacent structures of the uveal tract. This can lead to progressive ocular hypertension, hyphema (bleeding into the anterior chamber of the eye), and vision loss [1].

The influence of blood pressure on glaucoma

The relationship between blood pressure (BP) and glaucoma is an important area of research that requires collaboration between cardiologists and ophthalmologists [2, 5]. Ocular perfusion pressure (OPP) is defined as the difference between BP and IOP [5]. Low BP leads to low OPP, which can cause ischemic damage to the optic nerve and progression of glaucoma [5].

Studies show that both high and low BP can be associated with glaucoma. Low BP is particularly dangerous and is associated with disease progression in patients with normal-tension glaucoma (NTG) [5]. Patients with low nighttime BP readings are at the highest risk of glaucoma progression. Therefore, ambulatory blood pressure monitoring is a useful tool for identifying patients at high risk of disease progression [5]. Specialists should consider the relationship between BP and glaucoma when treating patients with comorbidities, avoiding excessive BP reduction, especially at night [5].

Diagnostics and treatment methods for glaucoma

Early diagnosis of glaucoma is crucial for preventing irreversible vision loss. It includes:

• Measurement of intraocular pressure (IOP): Regular measurement of IOP is a key element of diagnosis and monitoring [4].
• Fundus examination: Assessment of the optic nerve for damage.
• Gonioscopy: Examination of the anterior chamber angle to assess the aqueous humor outflow pathways [1].
• Optical coherence tomography (OCT): Allows for detailed visualization of eye structures, including the optic nerve and retina [1].

The main goal of glaucoma treatment is to lower IOP to a target level to prevent further damage to the optic nerve [2]. Treatment methods include:

• Medical therapy: Most often, these are eye drops that reduce the production of aqueous humor or improve its outflow [1].
• Surgical treatment: If medical therapy is ineffective or in certain types of glaucoma, surgery may be required. An example is the implantation of an Ahmed valve to improve the outflow of intraocular fluid or repositioning of a displaced IOL in UGH syndrome [1].
• Acetazolamide: This drug is used to lower both intraocular and intracranial pressure and can be effective in some forms of glaucoma and idiopathic intracranial hypertension [3, 6].
• New approaches: New therapeutic strategies are currently being researched. For example, glucagon-like peptide-1 receptor agonists (GLP-1RAs) demonstrate anti-inflammatory and neuroprotective properties in preclinical models of other neurodegenerative diseases, such as multiple sclerosis [6, 7]. Although direct application for glaucoma is still being studied, these studies open prospects for future neuroprotective strategies in ophthalmology.

Prevention and living with glaucoma

For people at high risk of developing glaucoma (e.g., those with a family history, diabetes, or high BP), regular preventive check-ups with an ophthalmologist are essential. Early detection and initiation of treatment can significantly slow the progression of the disease and preserve vision.

Patients diagnosed with glaucoma must strictly follow the doctor's recommendations, use prescribed medications regularly, and attend follow-up appointments. Controlling comorbidities, such as arterial hypertension or hypotension, also plays an important role in the comprehensive management of glaucoma [5].

Sources

1. Uveitis-Glaucoma-Hyphema Syndrome Secondary to Asymmetric Intraocular Lens (IOL) Haptic Fixation: A Clinical Lesson in Mechanism-Based Diagnosis and Treatment. https://pubmed.ncbi.nlm.nih.gov/42256830/
2. Blood pressure and glaucoma: At the crossroads between cardiology and ophthalmology. https://pubmed.ncbi.nlm.nih.gov/30882185/
3. Pediatric Intracranial Hypertension: A Spotlight on Imaging, the Idiopathic Intracranial Hypertension Treatment Trial, and COVID-19 Associated Cases. https://pubmed.ncbi.nlm.nih.gov/34749916/
4. Intraocular pressure and glaucoma. https://pubmed.ncbi.nlm.nih.gov/12170640/
5. Management of Blood Pressure in Patients with Glaucoma. https://pubmed.ncbi.nlm.nih.gov/28929290/
6. Review of Acetazolamide and Novel Medical Paradigms for Idiopathic Intracranial Hypertension Treatment. https://pubmed.ncbi.nlm.nih.gov/40801435/
7. GLP-1 receptor agonists in multiple sclerosis: a systematic review of preclinical and clinical evidence. https://pubmed.ncbi.nlm.nih.gov/42470876/

The information provided in this article is for reference purposes only and does not replace professional medical advice. Always consult a qualified specialist for the diagnosis and treatment of any diseases.