Normal IOP 10 to 21mmHg,
Acute rise in pressure to 40-50mmHg can cause rapid visual loss and retinal vasculature occlusion. IOP 20-30mmHg can cause glaucomatous damage over several years.
Few mechanism for raised IOP:
1. blocked flow from PC to AC (between iris and lens)
2. Blocked trabecular meshwork by iris / in the trabecular flow
3. Episcleral veins raised in pressure
Haloes of light, cloudy cornea and pain is a feature of very high IOP.
Visual field loss due to sustained high IOP (which cause optic nerve head ischaemia and pressure on nerve fibers) produce characteristic arcuate scotoma, spared the central vision. Until the terminal stage (tunnel vision) when there still some nerve fiber survived at richly innervated macula and vision can still be 6/6.
Risk factor for PoAG:
1. Increasing age
2. First degree relative having glaucoma (1 in 10)
3. African carribean x5 than caucasian
4. Pt having ocular hpt esp those wth thin cornea, larger CDR, high myopia
How to increase ocular absorption of drug:
1. Punctal occlusion
2. Closing of eyelid as it will stop lacrimal pumping mechanism, reduce drug passage through lacrimal duct.
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