Glaucoma Disease Progression

Role of Intra Ocular Pressure

Dr Shabbir Husain

(Cross-references:

  1. Introduction and Target Intra-ocular pressure - Dr. Ravin Das
  2. The role of intra-ocular pressure in glaucoma (Landmark studies in Glaucoma) - Dr. Shabbir Hussain (Slide 1-28)
  3. Implementing what we have learnt - Dr. Major Avinash Mishra (Slide 29-50)
  4. Achieving the targets set by the studies & reaching difficult target pressures - Dr. Rahul Shukla (Slide 51-85)
  5. Lumigan™ the Indian experience (L.E.E.D) - Dr. Shabbir Hussain. (Slide 86-100)


Is "Good Enough", "Low Enough"?
Glaucoma Diseases Progression Key Considerations

  • Good number of patients may be diagnosed only after some damage the optic nerve
  • Even when 40% of the nerve fibers are lost, patients can retain normal visual field
  • 56% of all newly diagnosed patients in the US present with moderate Glaucoma (already suffered optic nerve damage) at the time of diagnosis
  • Rate of disease progression can vary from patient to patient
  • Predicting the disease progression course is difficult

Land mark studies like AGIS, OHTS, EMGT illustrate the benefit of IOP reduction in all types of Glaucoma patients regardless of the severity of disease.

Lowering intraocular pressure can
- Prevent further progression of existing field damage:
- Prevent optic-nerve damage from progressing to visual field damage
- Prevent ocular Hypertension from progression to nerve damage

Glaucoma Diseases Progression - High Risk Groups

  • Patients on beta-blocker therapy for long time and experiencing "Drift"
  • Patients who do not respond sufficiently to Latanoprost
  • Patients who have not achieved their target IOP with current medications
  • Patients with some visual field damage
  • Patients with some optic nerve changes
  • Patients on multiple drug therapy
  • Patients with high baseline IOP
  • Patients having more than one risk factor like heredity, Diabetes, Hypertension


Glaucoma Treatment: Aim to Achieve and Maintain Lower Target Pressures and prevent disease progression

Evidence from controlled, prospective, randomized clinical trials:
Reducing IOP to lower target pressures can prevent glaucoma and slow or stop progression

  • OHTS
  • EMGT
  • CIGTS
  • CNTG
  • AGIS

Ocular Hypertension Treatment Study (OHTS)

Objective: To determine the safety and efficacy of topical medication in delaying or preventing the onset of glaucoma
1636 participants randomized to: Observation or topical glaucoma medication

Lowering IOP: Delays or Prevents the Development of POAG


IOP Lowering in OHT Reduces the Incidence of POAG



OHTS Results

Arch Ophthalmol 2002; 120: 701

  • 5 years
  • Cumulative probability of POAG

    medication group = 4.4% (N = 817)
    observation group = 9.5% (N = 819)
    Endpoint > 50% optic disc alone (no VF loss)

Development of POAG - Observation Group


Risk Factors for the Development of POAG in OHT

Hazard ratios:

1.22 (1.01, 1.49)
1.10 (1.04, 1.17)
1.71 (1.40, 2.09)
1.27 (1.06, 1.52)
1.27 (1.14, 1.40)
1.32 (1.19, 1.47)


Early Manifest Glaucoma Trial (EMGT)

Objective: To compare the effect of immediate therapy to lower IOP versus late or no treatment on the progression of newly detected open-angle glaucoma

255 patients randomized to: Laser trabeculoplasty plus topical betaxolol or to no initial treatment

Treatment and Observation Groups: IOP and Safety Results

In treated patients, IOP was reduced 25% from a baseline of 20.6 mm Hg to 15.5 mm Hg
at month 3
Treatment was well-tolerated but associated with increased incidence of lens opacities

Early Treatment Reduces and Delays the Progression of Glaucoma

Fewer Treated Patients Have Glaucoma Progression


Benefit of 1 mm Hg Additional IOP Lowering

Each incremental 1 mm Hg decrease in IOP was associated with a: 10% decrease in the risk of glaucoma progression


Collaborative Initial Glaucoma Treatment Study (CIGTS)

Objective: To determine if newly diagnosed patients with open-angle glaucoma are better treated initially with medication or filtration surgery

Medication group: n = 307
Surgery group: n = 300

Medical Management vs Surgery

Both Lower IOP

Medical Management vs Surgery - Both Effectively Prevent Visual Field Loss

Implications of EMGT and CIGTS: Optimal Treatment for Early Glaucoma

Patients with any field loss should be treated aggressively to reach low pressures that reduce the risk of progression

Both medical treatment and surgery effectively reduce IOP and the risk of progression

No change in usual approach at this time (medical treatment first for most patients)


Collaborative Normal-Tension Glaucoma Trial (CNTG)

Objective: To determine if IOP-lowering treatment is effective in reducing the progression of normal-tension glaucoma

140 eyes randomized to: Medical or surgical treatment (target 30% below baseline)
or no Tx

Lowering IOP Reduces the Risk of Vision Loss in NTG


Advanced Glaucoma Intervention Study (AGIS) 7


Objective: To determine the effects of surgical and laser IOP-lowering procedures in glaucoma patients with IOP uncontrolled on medications

789 eyes
Analyses of IOP lowering and progression:
Predictive: Does IOP during first 1.5 years predict later visual field loss?
Associative: Are consistently low pressures associated with stable visual fields?

Consistently Low IOP Reduces Vision Loss in Advanced Glaucoma

Low Target Pressure: Better Prognosis for Glaucoma Management

  • Patients with IOP < 18 mm Hg (mean 12.3): no mean change in visual fields over 8 years
    Aggressive treatment had a more favorable outcome
  • Pressures in the low normal range may be needed for some patients who already have field loss

Management of Glaucoma

  • Do corneal thickness testing on patients with: ocular hypertension or glaucoma
  • Recognize: lower IOP = better prognosis
  • Set a target pressure based on risk factors
  • Prescribe therapy likely to reach the target pressure
  • Monitor patients with serial visual field testing and optic nerve examination


Conclusions

  • Reducing IOP can prevent, slow, and stop glaucoma
  • Decision to treat in OHT based on evaluation of the risk of glaucoma vs the risks and costs of treatment
  • Individualization of care necessary for setting a target IOP
  • Include corneal pachymetry
  • The lower the IOP, the less the risk of glaucoma and field loss
  • Just 1 mm Hg additional IOP lowering can improve the prognosis
  • Multiple medications or surgery may be needed to reach target pressures
  • Optimal glaucoma management: Treat early, treat aggressively, and, think long-term