Importance Of Diurnal Variation

Dr Samarth Mishra

Introduction

Diurnal Variation Of IOP• 95% population: 11mmhg to 21mmhg

• Mean IOP: 15.8 ± 2.6 mmHg.

• IOP highest in early morning & lowest in late evening

• Mean amplitude of daily fluctuation in N: <5mmhg

• Variation in IOP: >5mmhg; suspicious

>8mmhg; diagnostic of glaucoma

• In 1904, Maslenikow, 1st ophthalmologist to quantitate daily fluctuations in IOP.

NORMAL INDIVIDUAL

• In 1963, de Venecia and Davis studied in 115 prison inmates with normal IOP; highest IOP at 5 AM & midnight & range of diurnal variation 4.9 mm Hg.

• Thiel found that highest IOP occurred between 5 & 7 AM before the patients arose.

• Katavisto found highest IOP values at 8 AM.

• Drance found highest IOP at 6 AM; mean diurnal range was 3.7 mm Hg.

GLAUCOMATOUS PATIENTS

• Thiel reported that IOP increased from midnight to 3 AM, reaching a peak between 3 and 7 AM.

• Drance found in untreated OAG, a peak IOP at 6 AM & mean diurnal variation 11mmhg.

• Kitazawa and Horie’s found mean variation of IOP 16 mm Hg.

• Katavisto found

1. Morning rise in 20%

2. Afternoon rise in 25%

3. Biphasic rise in 55%

EFFECTS OF GLAUCOMA THERAPY ON THE

DIURNAL CURVE

• Drance studied 132 patients receiving "medical therapy” whose IOP ≤19 mm Hg.

• diurnal variation: 7 to 8 mm Hg which is lower than 11 mm Hg that had been seen in untreated glaucoma pts.

• In untreated patients 46% peaks at 6 AM and only 14% at 10 PM.

• In the treated patients only 25% peaks at 6 AM, while 23% at 10 PM.

CAUSES OF THE DIURNAL VARIATIONS

A. Hormonal factors:

1. Cortisol

peaks in the early morning 8 am & lowest level at about midnight-4 am

2. Melatonin

3. Exogenous administration of corticosteroid:

• increase in IOP in patients with OAG 4 to 8 hours after administration.

B. Autonomic or Humoral control of Aq flow:

Facility of Aq humor outflow; effect small & clinically insignificant

Formation of Aq: due to circulating catecholamines

• Low- during sleep

• Increases during day

C. Mechanical factors:

1. Tension in intraocular muscle compresses globe during contracture. e.g. sleeping

2. Accommodation with corresponding contraction of the ciliary muscles; i.e. during sleep there is less accommodative effort than at other times

3. Alterations in blink pattern

SIGNIFICANCE OF DIURNAL VARIATIONS

• Important clinical implications for glaucoma patients.

• large diurnal variation (>8mmhg): risk factor for progression of glaucoma.

• IOP peaks over a certain level or a diurnal range in IOP above a certain level might be DD of ocular hypertension, in absence of visual field loss or glaucomatous cupping.

• In case of pts with NTG, a single pressure taken at a specific time represents a HIGH or LOW points, which doesn’t represent pts avg. pressures; important in DD of NTG.

• Office diurnal curve:

Checking the pressure every 1 or 2 hours from about 8 a.m. to 6 p.m.

Useful in therapy toward peak IOP, as well as controlling the avg. pressure during a certain time of day.

THANK YOU