Glory Eyecare Optometrists

Glaucoma: Key Points

• Glaucoma is the leading cause of irreversible blindness, affecting over 80 million people globally.

• It progresses silently, often without symptoms until significant vision loss occurs.

• Early detection and treatment are crucial to prevent permanent vision loss.

• High eye pressure is a key modifiable risk factor, although glaucoma can occur even with normal pressure.

 

What is Glaucoma?
Glaucoma is a progressive disease caused by optic nerve damage, leading to vision loss. This damage is often linked to increased eye pressure due to poor fluid drainage. Vision loss starts with peripheral vision and advances to central vision over time.

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Types of Glaucoma

• Open-angle glaucoma: Most common; due to gradual drainage canal damage.

• Angle-closure glaucoma: Rapid blockage of drainage canals, often with noticeable symptoms.

• Normal-tension glaucoma: Optic nerve damage occurs despite normal eye pressure.

• Congenital glaucoma: Present at birth due to underdeveloped drainage canals.

• Inflammatory glaucoma: Linked to autoimmune disorders.

• Neovascular glaucoma: Associated with diabetes and vascular issues.

 

Risk Factors

• Age (60+ years)

• Family history (especially siblings)

• Race (higher prevalence in people of African descent)

• High eye pressure or thin corneas

 

Symptoms

• Gradual loss of peripheral vision (most types)

• Acute angle-closure glaucoma symptoms:

  • Severe eye pain

  • Blurred vision

  • Halos around lights

  • Nausea and vomiting

 

Diagnosis
Key diagnostic tests include:

• Eye pressure measurement (tonometry)

• Visual field test (peripheral vision)

• Optic nerve imaging

• Gonioscopy (examining the drainage angle)

• Pachymetry (corneal thickness measurement)

 

Treatment Options
Although glaucoma has no cure, early treatment can control its progression:

1. Medications: Reduce fluid production or improve drainage.

2. Laser surgery: Improve drainage or reduce pressure.

3. Traditional surgery: Create new drainage pathways or use shunts.

4. Cataract surgery: May reduce pressure in some cases.

 

Repeat treatments or combination therapies may be needed for advanced cases.

 

Prevention
Annual eye exams are vital for early detection, especially for those at higher risk. If you notice symptoms or have concerns, consult an eye care professional promptly.

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​Glaucoma Diagnosis

Glaucoma is diagnosed through a series of tests conducted by an ophthalmologist or well-equipped experienced therapeutic optometrist to evaluate:

• Eye Pressure

  • Tonometry: Measures intraocular pressure (IOP).

• Optic Nerve Health

  • Funduscopy or Ophthalmoscopy: Examines optic nerve color and shape.

  • Optical Coherence Tomography (OCT): Provides detailed imaging of the optic nerve.

  • GDx Analyzer & Heidelberg Retinal Tomography (HRT): Assess optic nerve health.

• Visual Field

  • Perimetry: Tests peripheral vision, including sides, above, and below.

• Corneal Thickness

  • Pachymetry: Measures corneal thickness.

• Drainage Angle

  • Gonioscopy: Evaluates whether the angle between the iris and cornea is open or blocked.

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​Causes of Eye Pressure (Intra-ocular Pressure - IOP) Fluctuations

• Blinking, Saccades, and Eye Rubbing - Can trigger short-term IOP changes.

• Eye Rubbing & Eyelid Squeezing - May temporarily raise IOP by 40mm Hg or more. In extreme cases, eye rubbing can reach 310mmHg above baseline.

• Voluntary Blinks - Can temporarily increase IOP by 12mm Hg.

• Body Position - Bending, lying down, or tilting the head can elevate IOP.

• Blood Pressure - Fluctuations can affect IOP levels.

• Aqueous Humor Production - Increased production raise IOP.

• Hormone Levels: Cortisol and other hormones impact IOP.

• Circadian Rhythms - Sleep-wake cycles naturally alter IOP.

• Medications: Corticosteroids and certain drugs can cause IOP fluctuations.

• Eye Drops - Steroid, atropine, antihistamine and pupil-dilating drops can increase IOP, especially in glaucoma patients.

• Eye Injuries - Trauma may impact IOP.

• Uveitis - Inflammation can prevent proper fluid drainage.

• Blocked Drainage - Obstructed angles hinder fluid outflow.

• Stress & Hormonal shifts - Can elevate IOP.

• Drinking Water & Caffeine - Rapid intake or genetic predisposition can temporarily raise IOP.

• Breath Holding & Valsalva Maneuver - Increased chest pressure affect blood flow and IOP.

• Tight Collars/Neckties - Can restrict jugular vein and raise IOP.

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Types of IOP Fluctuations

• Short-Term: Seconds to minutes (e.g. blinking).

• Diurnal-Nocturnal: Follows daily cycles, peaking in the morning.

• Long-Term: Gradual changes due to aging or conditions.

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​Patterns of IOP Fluctuation

• IOP is highest in the early morning and lowest in the late afternoon.

• Fluctuations occur over varying timescales.

• Cyclical patterns vary between individuals.

 

Importance of IOP Fluctuations

• More common in glaucoma patients.

• Can affect treatments effectiveness (medications, laser, surgery).

• Day Phasing (measuring IOP every 2 hours over an 8-hour period) helps clinicians better manage IOP.

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Can a glaucoma patient with normal eye pressure readings?

Yes, a patient can have glaucoma with normal eye pressure readings. This is called Normal Tension Glaucoma (NTG)

 

Explanation

• Eye pressure (IOP): Normal ranges from 10–21 mmHg.

• Glaucoma: A condition causing optic nerve damage and visual field loss, typically associated with high eye pressure, but it can occur with normal pressure.

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Normal Tension Glaucoma (NTG):

• NTG occurs when glaucoma develops despite normal eye pressure. It is also known as low tension glaucoma.

Diagnosis:

• NTG is challenging to diagnose due to normal eye pressure. A thorough eye exam is necessary.

Treatment:

• Treatment focuses on lowering eye pressure, which may include medications, laser therapies, or surgery.

Risk Factors:

• Snoring (Obstructive Sleep Apnea), migraine headaches, Raynaud's phenomenon, and low diastolic blood pressure increase NTG risk.

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​Why visual field test results can be inconsistent?

Patient factors

• Inattention: Patients may not pay attention to the entire test, or they may press the button too soon. 

• Eye movement: Patients may wander off the central point of the test.

• Blood pressure: Low blood pressure can cause insufficient blood flow to the optic nerve.

Equipment factors

• Machine reliability: The machine may have poor reliability indices, such as fixation losses, false positives, or false negatives. Our equipment is one of the best equipment.

• Machine comfort: The machine may be in a noisy environment, or the patient may not be comfortable. 

Test repetition 

• Test repetition: The test is often repeated multiple times to account for errors. At least 2 consistent and reliable results are required for baseline and diagnosis.

• Machine calculations: The machine can use calculations to identify and remove errors.

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Can glaucoma patients have normal visual field results?

Yes, glaucoma patients can have normal visual field results, particularly in the early stages of the disease. However, visual field tests are essential for monitoring glaucoma, as they can detect subtle vision loss before it becomes noticeable.

Explanation:

• Early Stages: In the early stages of glaucoma, visual field defects are often subtle and may go undetected. Central vision may remain unaffected, even in advanced stages of the disease.

• Monitoring: Visual field tests are an important part of regular eye exams and can help identify early signs of glaucoma before symptoms are evident.

• Progression: Glaucoma typically progresses slowly, so consistent monitoring of visual field changes over time is crucial for effective management.

What to Expect:

• Mild Glaucoma: A normal visual field test, though abnormalities may be seen in the optic disc or retinal nerve fiber layer (RNFL).

• Moderate Glaucoma: Visual field abnormalities in one eye, while central vision may still be preserved.

• Severe Glaucoma: Visual field defects in both eyes, or significant vision loss in at least one eye.

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Can glaucoma patients have normal appearance of optic discs?

Yes, a glaucoma patient can have an optic disc that appears normal. A normal optic disc is typically pink-orange with a pale center, and glaucoma usually does not change its color. However, there are other signs that may indicate glaucoma.

Signs of Glaucoma:

• Cupping: The optic disc may appear cupped, where the diameter of the cup is larger than normal.

• Neuroretinal Rim Thinning: The neuroretinal rim (NRR) may appear thinner than usual.

• Blood Vessel Changes: Blood vessels within the optic nerve may shift or appear hemorrhagic.

• Visual Field Defects: Abnormalities in the visual field may be present.

• Cup to Disc Ratio: The ratio of the cup's diameter to the optic nerve head's diameter may be larger than normal.

Other Factors:

• Disc Size: Large optic discs may appear glaucomatous, but a large cup in a large disc can be normal.

• Disc Pallor: A pale optic disc may indicate advanced glaucoma or another condition.

An eyecare professional who specialize in glaucoma is the best resource for diagnosing glaucoma and providing appropriate care.

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Can a glaucoma patient have normal Optical Coherence Tomography (OCT) results?

Yes, it is possible for a glaucoma patient to have normal Optical Coherence Tomography (OCT) results, though this may be due to errors in the scan. While OCT is a reliable tool for detecting glaucoma, errors can lead to misdiagnosis.

OCT Scans and Glaucoma:

OCT scans help detect glaucoma by measuring the thickness of the retinal nerve fiber layer (RNFL). Glaucoma damages the RNFL, which can lead to visual loss.

Errors in OCT Scans:

Errors in OCT scans can result in false-negative diagnoses, where a patient with glaucoma is incorrectly diagnosed as normal. Such errors may be caused by artifacts, anatomical variations, or patient factors.

Patient Factors: The quality of an OCT scan can be affected by factors such as patient fixation, cooperation during the scan, and the presence of other eye conditions.

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Why multiple tests and visits are required to diagnose glaucoma?

Because it is a slow-progressing disease that can be difficult to detect in its early stages.

Why Multiple Tests and Visits Are Required:

• Establish a baseline: Repeated testing helps establish a baseline for your vision and monitor the progression of glaucoma over time.

• Avoid false positives: Multiple tests minimize the risk of false positives, reducing the likelihood of unnecessary treatments.

• Monitor treatment effectiveness: Ongoing testing enables the monitoring of treatment efficacy and adjustments as needed.

Tests Used to Diagnose Glaucoma:

• Eye pressure measurements: Assesses intraocular pressure (IOP) to identify abnormal levels.

• Visual field testing: Evaluates peripheral vision to detect any loss of vision.

• Optical coherence tomography (OCT): Provides high-resolution imaging of the optic nerve to detect structural changes.

• Other tests: Retinal imaging, dilated retinal examination, etc.

How Often Should You Be Tested: Regular eye exams are essential, particularly for those with risk factors for glaucoma. If you are at higher risk, more frequent tests may be necessary.

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How long does it take to diagnose glaucoma suspect?

A definitive diagnosis of borderline glaucoma, or glaucoma suspect, can take years due to the slow progression of the disease. Patients are closely monitored with follow-up exams every 3 to 12 months.

Explanation:

• Glaucoma suspect: A patient with borderline test results or risk factors for glaucoma.

• Follow-up exams: Necessary to recheck eyes and repeat tests as the disease progresses slowly.

• Slow progression: Glaucoma progresses gradually, making early signs difficult to detect.

• Treatment: Important to prevent irreversible vision loss.

Tests Used to Diagnose Glaucoma:

• Visual acuity testing

• Visual field testing

• Tonometry

• Pachymetry

• Slit lamp exam

• Gonioscopy

Diagnosis: A well-equipped experienced optometrist or ophthalmologist can diagnose glaucoma.