Approach to Studying and Managing Glaucoma
The comprehensive approach to studying and managing glaucoma focuses on early diagnosis, monitoring structural and functional changes, and controlling intraocular pressure (IOP) to prevent vision loss and maintain quality of life. 1
Definition and Pathophysiology
- Glaucoma is a chronic, progressive optic neuropathy characterized by damage to the optic nerve, death of retinal ganglion cells, and loss of retinal nerve fiber layer (RNFL), resulting in progressive visual field loss 1
- It is the second leading cause of blindness worldwide after cataracts, with an estimated 76 million people affected globally in 2020 1
- Primary open-angle glaucoma (POAG) is the most common form, characterized by open anterior chamber angles and optic nerve damage with or without elevated IOP 1
Risk Factors
- Elevated intraocular pressure (IOP) - the only modifiable risk factor 1, 2
- Older age 1
- Family history of glaucoma 1
- African race or Latino/Hispanic ethnicity 1
- Thin central corneal thickness 1
- Low ocular perfusion pressure 1
Diagnostic Approach
Comprehensive Initial Evaluation
- Complete ocular history (refractive error, trauma, prior surgery) 1
- Family history of glaucoma, including severity and outcomes 1
- Systemic history (asthma/COPD, migraine, Raynaud's syndrome, diabetes, cardiovascular disease) 1
- Race/ethnicity assessment 1
Essential Diagnostic Tests
- Intraocular pressure (IOP) measurement with multiple readings at different times of day 3
- Gonioscopy to assess anterior chamber angle and exclude angle closure or secondary causes 3
- Central corneal thickness (CCT) measurement, as thinner corneas are associated with higher risk of progression 3
- Optic nerve head (ONH) examination to identify structural changes:
- Vertical elongation of the optic cup
- Decreased neuroretinal rim width
- Cup enlargement
- Diffuse or focal narrowing of the neuroretinal rim 3
- Retinal nerve fiber layer (RNFL) assessment 3
- Visual field testing using standard automated perimetry (SAP) 1
- Structural imaging:
- Stereoscopic optic disc photography
- Optical coherence tomography (OCT) of ONH, RNFL, and macular ganglion cell complex 3
Classification of Glaucoma Severity
- Mild: Definite optic disc, RNFL, or macular imaging abnormalities with normal visual field on standard automated perimetry 1
- Moderate: Definite optic disc, RNFL, or macular imaging abnormalities with visual field abnormalities in one hemifield not within 5 degrees of fixation 1
- Severe: Definite optic disc, RNFL, or macular imaging abnormalities with visual field abnormalities in both hemifields and/or loss within 5 degrees of fixation in at least one hemifield 1
Management Approach
Goals of Treatment
- Control IOP in the target range 1
- Maintain stable optic nerve/RNFL status 1
- Preserve stable visual fields 1
- Maintain quality of vision and preserve quality of life 1
Determining Target IOP
- Target IOP should be individualized based on:
- Stage of glaucoma damage (structural optic nerve injury and functional visual field loss)
- Baseline IOP at which damage occurred
- Age of patient
- Additional risk factors (e.g., CCT, life expectancy, prior rate of progression) 1
- Lowering pretreatment IOP by 25% or more has been shown to slow progression of POAG 1
- Lower target IOP is justified for more severe optic nerve damage, rapidly progressing damage, or presence of other risk factors 1
Treatment Options
1. Pharmacological Therapy
First-line therapy: Prostaglandin analogues (PGAs) such as latanoprost 0.005% once daily
Other medication classes:
2. Laser Therapy
- Laser trabeculoplasty (argon laser trabeculoplasty or selective laser trabeculoplasty) should be considered when:
- Works by increasing outflow of aqueous humor through the trabecular meshwork 5
3. Surgical Interventions
- Indicated when IOP cannot be adequately controlled with medications or laser therapy 6
- Options include:
- Trabeculectomy
- Glaucoma drainage tube implantation
- Ciliary body cyclodestruction
- Minimally invasive glaucoma surgeries (MIGS) 6
Monitoring and Follow-up
- Untreated low-risk patients: Follow-up every 12-24 months 3
- Treated or high-risk patients: More frequent follow-up (every 3-6 months) until stable 3
- Each follow-up visit should include:
- Visual acuity measurement
- Slit-lamp biomicroscopy
- IOP measurement
- Periodic ONH and RNFL evaluation 3
- Both structural (optic nerve/RNFL) and functional (visual field) assessments are necessary as some patients show visual field loss without corresponding optic nerve progression 1
Special Considerations
- Patients considering keratorefractive surgery should be informed about potential impact on contrast sensitivity and IOP measurement accuracy 1
- LASIK, SMILE, and femtosecond laser-assisted cataract surgery may be relatively contraindicated in patients with advanced glaucomatous damage 1
- Multifocal intraocular lenses may further reduce contrast sensitivity in patients with glaucomatous optic neuropathy 1
Quality of Life Impact
- Glaucoma can significantly impact quality of life, affecting daily activities like reading, walking, and driving 1
- Performance deteriorates with worsening glaucoma severity or when both eyes are affected 1
- People with glaucoma are more likely to experience falls and motor vehicle collisions 1
- Direct medical costs for glaucoma in the US are estimated at nearly $3 billion annually 1
Common Pitfalls to Avoid
- Relying solely on IOP for diagnosis - approximately half of all individuals with POAG have IOP levels below 22 mmHg 1
- Focusing only on structural or functional assessment - both are necessary as some patients show visual field loss without corresponding optic nerve changes 1
- Failing to adjust target IOP when progression occurs despite treatment 1
- Overlooking medication side effects and adherence issues, which can significantly impact treatment success 1