Aqueous Humour ppt/notes/pdf/download/hd

Aqueous Humour is a clear, transparent, watery fluid that fills the anterior and posterior chambers of the eye. It plays an essential role in maintaining intraocular pressure (IOP), providing nutrition to the avascular structures of the eye such as the cornea, lens, and trabecular meshwork, and also helps in removing metabolic wastes. The aqueous humour is secreted by the non-pigmented epithelium of the ciliary processes located in the pars plicata region of the ciliary body. Once formed, it first fills the posterior chamber, then passes through the pupil into the anterior chamber, and finally drains out of the eye through the trabecular meshwork into the Canal of Schlemm, ultimately joining the episcleral veins. In terms of composition, aqueous humour is about 98–99% water. It contains electrolytes like sodium, chloride, and bicarbonate ions, as well as small quantities of glucose, amino acids, lactate, ascorbate, and dissolved oxygen. The protein content is very low (0.02–0.05%), which is important for maintaining optical transparency. The formation of aqueous humour involves three mechanisms — diffusion, ultrafiltration, and active secretion. Diffusion allows small molecules to passively move across membranes, ultrafiltration helps plasma filtrate to pass through fenestrated capillaries of the ciliary body, and active secretion—mainly driven by the Na⁺/K⁺ ATPase pump—is the major process responsible for aqueous production. Carbonic anhydrase enzyme also plays a role in the ionic transport mechanism that regulates the fluid’s composition and secretion rate. After formation, the circulation pathway of aqueous humour begins in the posterior chamber, flows through the pupil into the anterior chamber, and drains through two main routes: 1. Conventional (Trabecular) Pathway: Through the trabecular meshwork → Canal of Schlemm → collector channels → episcleral veins. 2. Unconventional (Uveoscleral) Pathway: Through the ciliary muscle and suprachoroidal space → absorbed into scleral veins. The normal IOP is maintained between 10–21 mmHg due to the balance between aqueous production and outflow. If this balance is disturbed, intraocular pressure rises, leading to glaucoma, which causes progressive optic nerve damage and visual field loss. The functions of aqueous humour are multiple. It maintains the shape and tone of the eyeball by sustaining IOP, nourishes avascular tissues such as the lens and cornea by supplying essential metabolites, removes carbon dioxide and metabolic wastes, maintains transparency and refractive index, and participates in immune defense by containing antibodies and ascorbate which neutralize free radicals. Clinically, drugs that modify aqueous humour dynamics are vital in glaucoma management. Beta-blockers and carbonic anhydrase inhibitors decrease aqueous production, while prostaglandin analogs and miotics increase its outflow. Aqueous Humour Aqueous Humour of eye Anterior segment Anterior chamber Posterior......