Glaucoma represents a group of progressive optic neuropathies characterized by degeneration of retinal ganglion cells (RGCs) and their axons, leading to characteristic optic nerve cupping and visual field loss. While traditionally classified as an ocular disease, growing evidence positions glaucoma as a neurodegenerative disorder with significant overlap in pathogenic mechanisms with Alzheimer's disease (AD) and Parkinson's disease (PD).[@goldberg2024][@weinreb2024]
Classification
Primary Glaucoma Types
Primary Open-Angle Glaucoma (POAG): Most common form, characterized by open anterior chamber angle and progressive optic nerve damage
Primary Angle-Closure Glaucoma (PACG): Acute or chronic obstruction of aqueous humor outflow through the iridocorneal angle
Normal-Tension Glaucoma (NTG): Optic nerve damage with normal intraocular pressure
Secondary Glaucoma Types
Exfoliative Glaucoma: Associated with pseudoexfoliation material
Pigmentary Glaucoma: Caused by pigment dispersion from the iris
Traumatic Glaucoma: Following ocular injury
Uveitic Glaucoma: Associated with intraocular inflammation
Glaucoma represents a group of progressive optic neuropathies characterized by degeneration of retinal ganglion cells (RGCs) and their axons, leading to characteristic optic nerve cupping and visual field loss. While traditionally classified as an ocular disease, growing evidence positions glaucoma as a neurodegenerative disorder with significant overlap in pathogenic mechanisms with Alzheimer's disease (AD) and Parkinson's disease (PD).[@goldberg2024][@weinreb2024]
Classification
Primary Glaucoma Types
Primary Open-Angle Glaucoma (POAG): Most common form, characterized by open anterior chamber angle and progressive optic nerve damage
Primary Angle-Closure Glaucoma (PACG): Acute or chronic obstruction of aqueous humor outflow through the iridocorneal angle
Normal-Tension Glaucoma (NTG): Optic nerve damage with normal intraocular pressure
Secondary Glaucoma Types
Exfoliative Glaucoma: Associated with pseudoexfoliation material
Pigmentary Glaucoma: Caused by pigment dispersion from the iris
Traumatic Glaucoma: Following ocular injury
Uveitic Glaucoma: Associated with intraocular inflammation
| Molecule | Role in Glaucoma | Connection to Neurodegeneration | |----------|------------------|--------------------------------| | Tau Protein | Hyperphosphorylation in RGCs | Links to AD pathology[@liu2025] | | Amyloid-Beta | Accumulates in retina and optic nerve | Shared with AD pathogenesis | | BDNF | Neurotrophic factor, reduced in glaucoma | Also depleted in AD/PD | | GFAP | Astrocyte activation marker | Glial response in neurodegeneration |
Genetic Factors
Key Genes Associated with Glaucoma
MYOC (Myocilin): Primary gene for juvenile-onset POAG, encodes myocilin protein
OPTN (Optineurin): Associated with NTG, also linked to ALS
TBK1: Regulates OPTN function, shared with ALS/FTD
CYP1B1: Primary congenital glaucoma gene
WDR36: Associated with POAG susceptibility
Polygenic Risk
Genome-wide association studies (GWAS) have identified numerous susceptibility loci, indicating a complex polygenic architecture similar to other neurodegenerative diseases.
Neurodegeneration Links
Shared Mechanisms with Alzheimer's Disease
Epidemiological studies reveal significant co-occurrence of glaucoma and AD:[@goldberg2024]
Tau Pathology: Recent studies demonstrate tau protein accumulation in glaucomatous retinae, suggesting common tauopathic mechanisms[@liu2025]
Amyloid-Beta Deposition: Aβ has been detected in retinal tissues from glaucoma patients
Common Risk Genes: APOE ε4 allele increases risk for both conditions
Biomarker Overlap: Similar CSF and blood biomarker profiles
Shared Mechanisms with Parkinson's Disease
Mitochondrial Dysfunction: Complex I deficiency in both conditions
Oxidative Stress: Elevated oxidative markers in aqueous humor
Alpha-Synuclein: Detected in retinal tissues of glaucoma patients
Neuroinflammation: Microglial activation patterns common to both
Clinical Features
Symptoms
Visual Field Defects: Typically始于周边视野,逐渐进展至中心视力
Optic Nerve Cupping: Increased cup-to-disc ratio
Intraocular Pressure Elevation (in most forms)
Retinal Nerve Fiber Layer Thinning: Detectable via OCT
Visual Field Testing: Humphrey or Goldmann perimetry
Confocal Scanning Laser Ophthalmoscopy: Optic nerve head imaging
Aqueous Humor Analysis: Biomarker detection
Therapeutic Approaches
Current Treatments
| Treatment | Mechanism | Limitations | |-----------|-----------|-------------| | Prostaglandin Analogs | Increase uveoscleral outflow | Local side effects | | Beta Blockers | Reduce aqueous production | Systemic effects | | Carbonic Anhydrase Inhibitors | Reduce aqueous production | Systemic side effects | | Alpha Agonists | Reduce production + increase outflow | Tachyphylaxis | | Surgical Interventions | Create alternative outflow pathways | Invasive, complications |
Emerging Neuroprotective Strategies[@nucci2024]
BDNF Mimetics: Neurotrophic factor replacement
Caspase Inhibitors: Block apoptotic pathways
Antioxidants: Combat oxidative stress
Gene Therapy: Target MYOC, OPTN mutations
Stem Cell Therapy: RGC replacement approaches
Animal Models
Common Models
DBA/2J Mouse: Spontaneous ocular hypertension
Chronic Elevated IOP Models: Laser or hypertonic saline induction
Transgenic Models: MYOC, OPTN mutations
Excitotoxicity Models: NMDA-induced RGC death
Recent Research (2024-2025)
Neurodegeneration Links: Research has established connections between primary open-angle glaucoma and neurodegenerative diseases including Alzheimer's disease and Parkinson's disease, suggesting shared pathogenic mechanisms involving retinal ganglion cell death and axonal degeneration.[@goldberg2024]
Tau Protein Involvement: Studies have identified tau protein pathology in glaucomatous retinae, linking glaucoma to Alzheimer's disease pathophysiology and suggesting potential common therapeutic targets.[@liu2025]
Biomarker Studies: Emerging research on glaucoma as a window into CNS neurodegeneration has identified candidate biomarkers that may aid early detection of both ocular and brain pathologies.[@nucci2024]