Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Corrective lens wikipedia , lookup
Blast-related ocular trauma wikipedia , lookup
Contact lens wikipedia , lookup
Idiopathic intracranial hypertension wikipedia , lookup
Visual impairment due to intracranial pressure wikipedia , lookup
Keratoconus wikipedia , lookup
Eyeglass prescription wikipedia , lookup
An introduction to the eyeball •Anterior segment •Posterior segment Anterior segment consists - Cornea - Anterior chamber - Iris -Posterior chamber -Lens -Ciliary body Lens is suspended from the ciliary body by fine delicate fibrils called suspensory ligament of the lens (Zonules) Posterior segment consists: - Vitreous cavity filled by vitreous humour Retina Choroid Optic nerve Diagrammatic representation of ocular structures Diagram of the eye ball Saggital section of eye 1. 2. 3. 4. 5. 6. 7. 8. Sclera Cornea Iris Pupil Lens Limbus Ciliarybody Ora serrata Anatomy of the Anterior Chamber • From: anterior to posterior: -Posterior surface of cornea -Anterior surface of iris -Anterior surface of lens - Peripheral recess (Angle of the anterior Chamber) -Depth 2.5mm in the centre -Decreases towards periphery -Filled with aqueous humor Angle of Anterior Chamber Formed by: Posteriorly -Root of the iris -Part of ciliary body Anterolaterally -Corneosclera(Trabicular tissue & Scleral spur) (Site of drainage of aqueous) Angles • Canal of Schlemm - Loose meshwork of tissue(Trabiculum) (Between Scleral, spur and Descemet’s membrane) - Aqueous drained by small reunite tributaries - Small venules and aqueous vein Formation of aqueous humor • Filtration theory • Ultra filtration theory • Secretion theory -Active ciliary secretion 75% -Ultra filtration 25% Walls of capillaries of epithelium of iris , Ciliarybody &retinal constitutes a system of semi permeable membrane separating blood from ocular cavity is known as blood aqueous barrier Formation of aqueous Ultrasonographicview of angle Formation of aqueous • 1. Active secretion: by the non-pigmented ciliary epithelium accounts for the vast majority. • 2. Passive secretion: by ultra filtration and diffusion. -Depend son: • Capillary hydrostatic pressure, • The oncotic pressure • The level of IOP Physiology of outflow • The trabecular meshwork (trabecular) 90% • The uveoscleral (unconventional) route 10% • Some aqueous also drains via the iris. -Collected in in P.C. -Flows through pupil into A.C. -Finally escapes through drainage channels -At angle of anterior chamber -Into the canal of Schlemm - Through aqueous veins (Approximate 2 micro Liters drains away/minute) Aqueous humor • • • • • Clear fluid Filling anterior/posterior chambers Refractive index 1.336 Viscosity 1.025 to 1.040 Osmotic pressure slightly> plasma Constituents • It contains: - Glucose - Urea - Proteins - Inorganic salts - Ascorbic acid - Lactic acid - Some dissolved Oxygen Transparent media • Cornea • Lens • Aqueous • Vitreous humor - So formation of aqueous and maintenance of Intraocular pressure are important aspect of physiology of the eye - Though yet poorly understood Intraocular pressure • • • • • • • Pressure inside the eyeball Determined by production by ciliary epithelium Drainage by trabecular meshwork Normal I.O.P. ranges from 15 -20 mm of Hg Diurnal variation: 2 mm of Hg Variation in tow eyes of 4 or 6 mm of Hg indicates Investigation A rise may occur some times In Morning or In evening Factors affecting alteration of I.O.P. • Variation in: -Capillary hydrostatic pressure Rise in: raise & vice versa • Osmotic pressure of blood • • • • Increased capillaries permeability Change in volume of eyeball Obstruction in circulation of aqueous Alteration in aqueous formation