What Factors causing short-term changes in intra-ocular pressure

1) Arterial blood pressure

2) Systemic venous pressure (SVP)

3) Mechanical pressure

4) Plasma osmolarity: Hyper-osmolarity due to mannitol makes intra-ocular pressure lower.

5) Blood pH : Metabolic acidosis by carbonic anhydrase inhibitors like acetazolamode reduces intra-ocular pressure.

6) Diurnal variation in intra-ocular pressure:

- Normal 5 mm Hg

- >8 mm of Hg - glaucoma

- 5 to 8 mm of Hg - glaucoma suspect

Normal peak in early morning and lowest in evening.

7) Seasonal variation

8) Systemic hyperthermia

9) Effect of general anaesthesia on intra-ocular pressure: Type of anaesthesia has role, so must be kept in mind while measuring inua- ocular pressure under GA. specially in children with congenital glaucoma.

In general, once the patient is under the effect of general anaesthesia: intra-ocular pressure is reduced.

10) Effects of drugs on intra-ocular pressure:

a) Alcohol, morphine products, lower etc.: intra-ocular pressure,

b) Steroids, caffeine, tobacco, LSD, etc.: increase intra-ocular pressure.

11) Blockage of the circulation of the aqueous -at pupil or at angle of anterior chamber: increase intra-ocular pressure.