Glaucoma Overview and Mechanisms of Disease

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Questions and Answers

What is considered the most important barrier in glaucoma?

Iris barrier

Lens barrier

Scleral barrier

Corneal barrier (correct)

What does a thin cornea indicate in relation to glaucoma risk?

Lower risk of nerve fiber damage

Lower risk of central retinal vein occlusion

Higher risk of glaucoma (correct)

Higher risk of elevated IOP

Which factor relates to the overall ocular structural rigidity?

Corneal resistant factor (CRF) (correct)

Central corneal thickness (CCT)

Corneal hysteresis (CH)

Intraocular pressure (IOP)

What role does glutamate play in relation to nerve fiber health?

It maintains ion homeostasis for NMDA receptors Signup and view all the answers

What risk factor is associated with primary open-angle glaucoma (POAG) prevalence?

Age demographics Signup and view all the answers

What occurs when excess glutamate damages nerve fibers?

Excitotoxic NMDA receptor activation Signup and view all the answers

What is the role of the corneal hysteresis (CH)?

It reflects corneal viscoelasticity. Signup and view all the answers

How does delayed calcium deregulation occur in glaucoma?

From elevated glutamate levels Signup and view all the answers

Which of the following is a proposed goal of pharmacological therapy for glaucoma?

Reduction in mean IOP Signup and view all the answers

What does the term 'ischemic insult' refer to in the context of glaucoma?

Interruption of blood supply Signup and view all the answers

What primarily characterizes glaucoma?

Optic nerve head atrophy Signup and view all the answers

Which factor contributes to the resistance to trabecular aqueous outflow?

Decreased inflammatory signaling Signup and view all the answers

What percentage of aqueous outflow occurs through uveoscleral pathways?

20% Signup and view all the answers

Which mechanism is NOT a primary mechanism of glaucoma?

Increased ocular blood flow Signup and view all the answers

What role does decreased ocular blood flow play in glaucoma?

It leads to deterioration of the optic nerve head Signup and view all the answers

What happens to collagen in the trabecular meshwork with increased treatment from prostaglandin agonists?

It causes an increase in spaces between the CM fibers Signup and view all the answers

Which of the following is a factor contributing to increased IOP?

Higher production of aqueous humor Signup and view all the answers

What determines the pattern of visual field loss in glaucoma?

Programmed retinal ganglion cell death Signup and view all the answers

Which statement is true regarding the pathophysiology of resistance to aqueous outflow?

Excess collagen increases outflow resistance Signup and view all the answers

What is a result of increased episcleral venous pressure?

Increased resistance to aqueous outflow Signup and view all the answers

Study Notes

Glaucoma Overview

Glaucoma is an optic neuropathy characterized by optic nerve head atrophy and retinal ganglion cell death, leading to specific patterns of visual field loss.
Initial damage is caused by multifactorial primary mechanisms of damage (PMOD).

Primary Mechanisms of Disease

Elevated Intraocular Pressure (IOP)
- Major cause of glaucoma, influencing 80% of aqueous humor outflow through the trabecular meshwork (TM).
- Resistance often originates from the posterior ciliary body leading to decreased drainage through Schlemm's canal.
- Increased pressure in the episcleral veins impedes fluid circulation.
- Uveoscleral Outflow (USO): Accounts for 20% of outflow; increased collagen among ciliary muscle fibers can hinder fluid passage.
Decreased Ocular Blood Flow (OBF)
- Insufficient blood flow leads to further deterioration of the optic nerve head (ONH).

Ocular Biomechanical Properties

High IOP can exceed the resistance capabilities of ocular structures, primarily the cornea.
Key Components:
- Corneal Hysteresis (CH): Reflects the eye's ability to absorb and dissipate pressure.
- Corneal Resistance Factor (CRF): Indicates overall structural rigidity of the eye.
- Central Corneal Thickness (CCT): Thinner corneas correlate with a higher risk of developing glaucoma.

Secondary Mechanisms of Damage

Types of Damage:
- Mechanical damage and ischemic insult.
- Glutamate excitotoxicity disrupts neurotransmitter function and ion homeostasis in nerve fibers.
- Excess glutamate can lead to prolonged NMDA receptor activation, causing increased calcium (Ca²⁺) influx and potential toxic levels.
- Resulting conditions include delayed calcium deregulation, nitric oxide synthesis, neurotrophin deprivation, and apoptosis of nerve cells.

Glaucoma Risk Factors

Elevated IOP.
Suspicious changes in optic disc appearance.
Family history of glaucoma.
Increased susceptibility in specific populations; higher prevalence in Hispanics and blacks (Primary Open-Angle Glaucoma).
Age increases risk.
Conditions such as myopia, diabetes mellitus, systemic vascular diseases, and central retinal vein occlusion are associated with higher glaucoma risk.

Pharmacological Therapy Goals

Aim to reduce mean intraocular pressure (IOP) to minimize risk of optic nerve damage and preserve vision.

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Description

This quiz delves into the multifaceted aspects of glaucoma, focusing on its characterization as an optic neuropathy. Participants will explore primary mechanisms of disease, including elevated intraocular pressure and its effects on retinal ganglion cells and visual field loss.