TARGET INTRAOCULAR PRESSURE

Dr. Samarth Mishra

Introduction

Glaucoma

progressive optic neuropathy as a results of RGCs loss

VFL

IOP- important risk factor & only factor that can be modified at present time

Reducing IOP is currently the only clinically proven way to slow down the progression of glaucoma

Fundamental goal-

Slowing the rate of RGCs loss to age dependent rate

Reduce the rate of progression of glaucomatous damage

Target IOP

A “target” pressure should be set as a goal of long term therapy.

it should be chosen on an individual basis, weighing potential benefits and risks of treatment for each patient.

Definition: “upper limit of IOP that prevents further glaucomatous damage”

Also called the “Ideal pressure”, “safe level of IOP”

Evidence from Clinical Studies

Ocular Hypertension Treatment Study (OHTS)

≥20% reduction of IOP from initial value, leads to a lower rate of glaucoma progression in OHT patients.

Collaborative Initial Glaucoma Treatment Study (CIGTS)

To determine newly dx pts with POAG are better treated initially with medication Vs filtering Sx.

Both lowered IOP; Sx >medication

Glaucoma progress will be minimal if pts are treated aggressively to achieve low target pressure.

Early Manifest Glaucoma Trial (EMGT)

Compare the effect of immediate t/t to lower IOP Vs no t/t on progression of newly detected POAG.

For every 1 mm drop in IOP, a 10% reduction in risk of glaucomatous progression was observed.

Early t/t reduces & delays glaucoma progression

Advanced Glaucoma Intervention Study (AGIS)

Trabeculectomy Vs laser trabeculoplasty in pts with IOP uncontrolled by medication

Target IOP was set at <18 mmHg

Follow-up pts with lower IOP were free from visual field impairment.

Collaborative Normal Tension Glaucoma Study (CNTGS)

Effect of IOP decrease in patients with NTG or low tension glaucoma

≥30% IOP reduction from base line, decrease delayed the progression of glaucomatous lesions by 3 years

Establishing a target IOP

Why? To maintain functional vision throughout the patients lifetime with a minimal effect on quality of life

When? On initial visit & review periodically

How? Individualized

Assessment of target IOP

Based on an individual glaucoma risk assessment

1.Estimation of amount of glaucoma damage (optic disc and visual field assessment).

If advanced optic nerve damage at the time of diagnosis, set lower target IOP & vice versa

2.Appreciation of the damaging IOP or “maximum” IOP at which damage has occurred.

lower IOP at initial presentation, set lower target IOP & vice versa

3. Life expectancy of pts.

High expectancy, set lower the target IOP & vise versa.

4. Identification of the other risk factors for progression (presence of a severe damage in other eye, family history of blindness from glaucoma, high myopia, ethnicity, vascular risk factors)

5. Assessment of the rate of progression of glaucoma damage, i.e severity of damage that has already occurred versus time.

6. Centre corneal thickness

Factors Set High target IOP Set Low target IOP

Initial presentation Higher IOP Lower IOP

Life expectance Shorter Longer

ONH damage Early Advanced

HOW TO CALCULATE A TARGET PRESSURE

1. IOP <21 mm Hg

2. Lower IOP by 20%-30% from base line

3. Lower IOP by 1/3 of base line

4. A formula proposed by H. Jampel at 1995 AAO Glaucoma update

Target IOP = IP (1- IP/100)

Modified Jampel Target IOP, 1999

Ex. IP- 30 , Z- 2

TP= 30 (1-30/100)-2 ± 2 = 19±2 mm Hg

AAO GUIDELINES: TARGET IOPClinical conditions Target IOP

1. Glaucoma patients with mild damage (optic disc cupping but no VF loss)

Reduction of 20-30% from baseline

2. Glaucoma patients with advance damage Reduction of 40% or more from baseline

3. Normal pressure glaucoma or NTG Reduction of 30% from baseline

4. Ocular hypertension Reduction of 20% from baseline

5. Open angle glaucoma with IOP in the mid to high 20s

Target IOP range 14-18 mmHg

6. Advanced Glaucoma Target IOP < 15 mmHg

7. OHT whose IOP > 30 mmHg with no sign of optic nerve damage

Target IOP < 20 mmHg

Recommended target IOPs in the Guidelines of the European Glaucoma Society (2003)

POAG Target IOP

Early Glaucoma <18 mm Hg

Mod Glaucoma <15 mm Hg

Adv Glaucoma <12 mm Hg

Terminal Glaucoma <10 mm Hg

NTG Target IOP

Early Glaucoma <15 mm Hg

Mod Glaucoma <12 mm Hg

Adv Glaucoma <10 mm Hg

HOW TO USE A TARGET PRESSURE

Draw an IOP curve for each glaucomatous patient and to highlight the target pressure on the curve.

Target pressures should be reevaluated periodically.

because a target IOP that is appropriate when you first see a patient may not be safe pressure

10 yrs later patient may develope any new systemic or ocular conditions that might affect the risk/benefit ratio of therapy.

HOW TO USE A TARGET PRESSURE cont..

Target pressure needs to be lowered if glaucomatous damage is progressing despite IOP’s below the initially set target.

Conversely, the target IOP range may have to be increased if achieving the target IOP causes adverse ocular or systemic side effects.

Listen to Expert

“ You’re not going to have one target pressure that’s appropriate for every patient. It is a dynamic process and you always have to be alert and open to modification.”

L. Jay Katz,

Professor of Ophthalmology

Jefferson Medical College

Listen to Expert

“Patients should be followed closely over time and their target pressures should be adjusted, depending upon how the patient is doing. If the patient progresses, the target pressure should be lowered. If the patient does very well, the target might be raised.”

Stevens Simmons,

Associate Clinical Professor,

Albany Medical College

Target Intraocular Pressure Calculator

Key PointsIOP is a significant, modifiable risk factor in Glaucoma

Lowering IOP to a target level is helpful across the spectrum of ds states & IOP levels:

Advanced glaucoma

Normal tension glaucoma

Newly diagnosed glaucoma

Target IOP range must be:

Individualized

Re-evaluated periodically

THANK YOU