Eye Anatomy and Physiology_Basic_Module1_Ppt

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Presentation Transcript

Anatomy & major eye diseases : 

Anatomy & major eye diseases

Ocular Anatomy : 

Ocular Anatomy Overview of the eye: Cornea Iris Crystalline lens Retina

Part 1: Structures around the eye : 

Part 1: Structures around the eye

External eye - Conjunctiva : 

External eye - Conjunctiva Thin mucus membrane covering the sclera Acts as a lining for upper and lower lids Function: Important in tear film and mucus formation to keep the eyes clean and moist

Conjunctiva : 

Conjunctiva Thin mucus membrane extending from the limbus posteriorly covering the anterior part of the sclera Then the conjunctiva is reflected at the fornix to cover the inside of the upper and lower lids The folding of conjunctiva between the eye ball and eye lid creates a bag like structure called the conjunctival sac

Slide 6: 


Tearfilm : 

Tearfilm Produced by the tear & other glands A layer of water, oils and nutrients that flow over the exposed surfaces of the eye Approximately 0.5ml/1.0ml of tears are produced each day Virtually no tears are produced during sleep Function: Keep the eye moist, clean, & form a smooth refractive surface

Tear film structure & function : 

Tear film structure & function

Slide 9: 

Tear Flow

Eyelids & Tears : 

Eyelids & Tears

Slide 11: 

Part 2: THE EYE - Anatomy

Slide 12: 

Cornea Structure Transparent; No blood vessels Endothelium critical to transparency (viscoelastics for protection) The shape of the cornea directly impacts visual acuity Function: major refractive structure of the eye (+45D) The junction between Sclera & Cornea is called Limbus Outer Fibrous Layer : Cornea + Sclera

The CorneaGauging the Corneal Diameter : 

The CorneaGauging the Corneal Diameter

Corneal structure : 

Corneal structure Epithelium Bowman’s Membrane Stroma Descemet’s Membrane Endothelium Outside: Tear Inside: Aqueous Humour

Corneal physiology : 

Corneal physiology Epithelial cells are tightly joint together & highly regenerative. They serve as a natural barrier towards micro-organism invasion to the cornea. Cornea is transparent because of the highly regular line up of collagen fibres Wound / ulcers penetrating the Bowman’s membrane results in new collagen fibre formation which does not have the regular pattern – scar formation.

Corneal physiology : 

Corneal physiology Endothelial cells is responsible for maintaining the water balance & thus transparency of the cornea. Hypoxia (lack of oxygen) can result in reduced endothelial activities and the cornea will swell (edema), causes haziness and new blood vessel formation both affecting corneal transparency Corneal Edema Corneal New Vessel

Corneal Physiology : 

Corneal Physiology Oxygen necessary to maintain transparency and avoid hypoxic stress Hypoxia = reduced oxygen levels CL wear may compromise oxygen availability

Corneal Physiology : 

Corneal Physiology Corneal oxygen supply Open eye Atmosphere (21% oxygen @ sea level) Limbal blood vessels Aqueous humor Closed eye Palpebral and limbal blood vessels (7% oxygen) Aqueous humor

Corneal Physiology : 

Corneal Physiology Hydration dynamics The stroma is a “sponge,” freely absorbing water Bounded by two cell layers designed to maintain water content at ~78% Endothelium cells contain active “pumps” Cornea swells when pumps can’t keep up with inflow of water from tearfilm

Why the Cornea Swells : 

Why the Cornea Swells Epithelium responds to hypoxia by producing excess lactate Lactate enters stroma and changes pH/osmolarity Change in osmolarity pulls H2O into stroma Results in corneal swelling (edema)

Sclera : 

Sclera “The White of the Eye” Function: Protective layer of the eye Also collagen fibres No regular patterns Tendons of extra-ocular muscles blend with it for insertion

Uvea : 

Uvea The middle vascular layer of eye, uvea, consists of 3 structures: Iris (11 – 13 mm) and Pupil (3 – 4 mm) Ciliary Bodies & Zonules Choroid

Iris & pupil : 

Iris & pupil Function: Control the amount of light entering the eye by adjusting the pupil size Circular shaped diaphragm containing 2 sets of muscles to control the pupil size. (circular & radial muscles) With pigment & non-pigmented cells. Many pigments = 'brown eyes'; some pigments = 'green eyes‘; very few pigments = 'blue eyes‘ The pupil should be equally big & round and respond both to light & accommodation

Uvea: Ciliary Body : 

Uvea: Ciliary Body Function: Increase refractive power to help focusing at near (accommodation); produce aqueous humour Contraction of ring shape ciliary muscle causes the ciliary body to move anteriorly.

Lens : 

Lens Second major refractive component of the eye (20D, ~30% of total power) Elastic nature helps focusing at different distances Lens grows with age Capsule Nucleus Cortex

Uvea: Choroid : 

Uvea: Choroid Thin, spongy, highly vascular, dark brown, layer. Function: Important to provide nutrition to the inner eye (retina)

Slide 27: 

SCLERA CHOROID RETINA VITREOUS Retina Inner layer of eye that contains 10 layers & 120 millions photoreceptors & over 1 Million nerve fibres. Function: Transform light energy to electrical signals

Retina: macula & fovea : 

Retina: macula & fovea Macula (macula lutea and fovea centralis). At posterior pole of eye It is called the Macular Lutea because it contains a lot of Lutein: a yellow substance which is a form of Vitamin A to protect the macular from free radical damages due to high energy radiation Spot of most acute vision. Fovea: Small shallow depression in the center of macula caused by almost complete absence of inner retinal layers. Rods absent and only cones.

Examination of the Retina : 

Examination of the Retina Direct Ophthalmoscopy

Optic Nerve : 

Optic Nerve Carries visual impulses from the retina to the brain Consist of 1 Million Nerve Fibres

Common eye diseases - Anterior : 

Common eye diseases - Anterior Superficial Conjunctiva – Conjunctivitis, Hemorrhage Cornea – Keratitis, Corneal Ulcer Eye lid – Ptosis, Trichiasis, Blepharitis, Hordeolum (Stye) Dry eye Anterior Segment Glaucoma – Abnormal Intra-Ocular Pressure Cataract – The crystalline lens turns opaque Iritis– Inflammation of the Iris

Glaucoma : 

Glaucoma Normal range : 12 – 16 mm Hg IOP of 21 mm Hg or above is highly suspicious The AOA definition : a group of ocular diseases with various causes that ultimately are associated with a progressive optic neuropathy leading to loss of visual function

Cataract : 

Cataract Cataract – cloudy of the lens that blocks some light from reaching the retina & interfering with vision.

Common eye diseases – Posterior Segment : 

Common eye diseases – Posterior Segment Vitreous – degeneration causes floaters. Common & usually harmless, however, sudden onset or worsening can mean serious retinal problem. Degenerated vitreous can cause traction on the retina resulting in retinal detachment.

Common eye diseases – Posterior Segment : 

Common eye diseases – Posterior Segment Retina – Retinal degeneration (causing retinal holes and retinal detachment). Strongly associated with high myopia. – Retinal hemorhage (diabetes, hypertension or a hit at the head or the eye)

Thank You : 

Thank You

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