Glaucoma Basic sciences Dr.Qumber Abbas

Agenda  Aqueous production Anatomy Physiology  Aqueous out flow Anatomy physiology

anatomy  ciliary body has two components Posterior pars plana (4mm) Anterior pars plicata (2mm)

Pars plicata  pars plicata consists of 70 radially oriented ciliary processes which project into the posterior chamber:  A ciliary process is; Lined by pigmented epithelial layer And non-pigmented epithelial layer Central arteriole

Physiology : Non-pigmented Epithelium of Ciliary Process  It has: Tight junctions (blood aqueous barrier) Na/K ATPase pump (actively secretes Na ions into posterior chamber, water follows passively under osmotic gradient)  Carbonic anhydrase also plays role in production (unknown mechanism)

Factors Affecting Aqueous Secretion Diminished by: 1. factors that inhibit active metabolism e.g. 1.Hypoxia 2.Hypothermia  Drugs  Beta-blockers (timolol)  Sympathomimetics (adrenaline)  Carbonic anhydrase inhibitors (diamox)

Factors Affecting Aqueous Secretion 3. Cyclodestructive procedures  Cyclocryotherapy  Laser ablation

Factors Affecting Aqueous Secretion 4.Ciliary body shutdown 1.Inflammation of sectretory ciliary epithelium associated with iridocyclitis 2.Retinal detachment Passive secretion play very little role

Aqueous outflow anatomy of The 1.trabecular meshwork sieve like structure in angle three components 1.The uveal meshwork (innermost) Cord-like meshes from root of iris to schwalbe line. Large intertrabecular spaces Less resistance

2. The corneoscleral meshwork (middle portion) from scleral spur to shwalbe line sheet like meshes intertrabecular spaces smaller than uveal The endothelial meshwork (outermost) (,juxtacanalicular) links corneoscleral meshwork with the endothelium of the inner wall of the shlemm canal Offers major resistance

2. Schlemm canal  Circumferential channel in perilimbal area 1. Inner wall lined by endothelial cells 2. Outer wall by flat cells 3. Collector channels in outer wall connect with episcleral veins

Physiology Flow from posterior to anterior chamber via pupil. Then exit via 2 routs:  Trabecular route(90%) Increased by  Drugs Miotics sympathomimetics  Laser trabeculoplasty  Trabeculotomy  Some aqueous also drains via the iris  Uveoscleral route(10%) Decreased by miotic Increased by  Atropine(mydriatic)  Sympathomimetics  Prostaglandins Passes across the face of ciliary body into suprachoroidal space and drained by venous circulation in ciliary body, choroid and sclera