Eye Anatomy 2024-2025 PDF

Eye Anatomy Trisevgeni Ntinioti, MD, MScs, PhD Academic year 2024-2025 Basic Ophthalmic Anatomy  The eye is shaped liked a round ball, with a slight bulge at the front 3 main layers: 1. Outer layer: sclera (white opaque membrane).The slight bulge in the scle...

Eye Anatomy Trisevgeni Ntinioti, MD, MScs, PhD Academic year 2024-2025 Basic Ophthalmic Anatomy  The eye is shaped liked a round ball, with a slight bulge at the front 3 main layers: 1. Outer layer: sclera (white opaque membrane).The slight bulge in the sclera at the front of the eye is cornea (clear membrane ) 2. Middle layer: choroid. The front of the choroid is iris (colored part of the eye). In the center of the iris is pupil (circular hole). 3. Inner layer: retina. Contains sensory retina and retinal pigment epithelium (RPE). RPE lies between the sensory retina and the wall of the eye.  Inside of the eye is divided into sections 1. Anterior chamber: is the front part of the eye between cornea and iris 2. Posterior chamber: is between iris and lens 3. Vitreous chamber: is between the lens and the back of the eye Fluids Fluid fills most of the inside of the eye. *Both anterior/posterior chambers are filled with aqueous humor **The vitreous chamber contains vitreous humor. Those 2 fluids press against the inside of the eyeball and keep its shape  Basic Ophthalmic Anatomy-outer eye 1. Eyelids: - protection of the eyeball - secretion, distribution & drainage of tear -blinking distributes tears across cornea and maintance a smooth optical surface. Contains: 1.skin and subcutaneous tissue 2.orbicularis oculi 3.levator apparatus 4.conjunctiva  Closure by contraction of orbicularis oculi muscle (facial nerve) Opening by levator muscle (oculomotor nerve) Orbicularis oculi muscle has 3 parts: a. palpebral part (gently closes the eyelids) b. lacrimal part (drainage of the tears) c. orbital part (tightly closes the eyelids) Tarsal plates are located deep to palpebral region of the orbicularis oculi muscle and separated to the upper eyelid(superior tarsus) and lower eyelid(inferior tarsus) Meibomian glands(tarsal glands), ciliary glands of Moll(sweat glands) and glands of Zeis (sebaceous glands) *eyelashes are protective and *grey line is visible along the length of the lid margin between the lashes and the meibomian glands Rich arterial supply:  Ophthalmic artery: lacrimal, medial palpebral, supraorbital, dorsal nasal and supratrochlear arteries  Facial artery: angular branch  Superficial temporalartery: transverse facial artery branch Venus drainage:  Superior/inferior ophthalmic vein  2. Conjunctiva:  a mucous membrane  contributes to tear production  Avoid infections/resistance to microorganism Tears: water, mucous, chemicals against microorganisms Superior & inferior Meniscus on lower Lacrimal gland puncta at the nasal lid margin end of the eyelids nose nasolacrimal duct Lacrimal sac 3. Cornea: innervated and avascular tissue *sensation is derived from the nasociliary branch of the first division of (ophthalmic) of the trigeminal nerve *contains autonomic sympathetic nerve fibers *source of nutrients is aqueous humor Main function is refraction and transmission of light due to curved shape of the cornea *Cornea and sclera constitute the outer covering or coat of the eyeball (oval aspherical shell)with the main purpose to protects the structures inside the eye **cornea is a transparent tissue that acts as a structural barrier and protects the eye against infections ***contributes to 2/3 of the refractive power of the eye Layers: Epithelium -barrier to chemicals and water -barrier to microbes-to provide a smooth surface as an internal part of tear film -cornea interface contributing to refractive power of the eye -Langerhans cells which perform important immunological functions Membrane of Bowman -helps in maintaining the corneal shape Stroma -mechanical strength to cornea -transparency of cornea -main refracting lens  Dua’s (2013) or pre-Descemet’s membrane - acellular, collagen, elastin  Descemet’s membrane -resting layer for endothelial cells  Endothelium -maintains corneal clarity by removing water from the corneal stroma  Photos Central cornea 500μm thick Peripheral cornea 700μm Corneal diameter 11-12 in males, 10-12 in females 90% of thickness is stroma Corneal limbus: -border between cornea and sclera -highly vascularized  Basic Ophthalmic Anatomy-inner eye 1.Uvea comprises: 1.Iris: circular colored part of the eye -2 layers:  Stroma (Pigmented fibrovascular layer) is connected to a sphincter muscle (sphincter pupillae) which contracts the pupil in a circular motion and a set of dilator muscles (dilator pupillae), which pull the iris to enlarge the pupil.  Pigmented epithelial cells -can regulate the amount of light that can enter the retina -constriction is parasympathetic -dilation is sympathetic 2.Ciliary body: -anterior part (ciliary epithelium) forms aqueous humor -posterior part merges into the retina at the ora serata 3.choroid: consisting of blood vessels, connective tissue and pigment cells  provides oxygen and nutrition to the outer retinal layers 2.Lens (crystalline lens)  transparent biconvex structure  relatively dehydrated  is located between iris and vitreous  comprises a mass of long cells (fibers) that provide proteins  is enclosed within an elastic capsule  -the capsule is attached by zonular fibers to the ringlike ciliary muscle that encircles the lens 3.Aqueous humor: 4.Vitreous humor: Space between cornea and iris Between lens and retina  Is a transparent water-like fluid  is transparent, colorless, similar to blood plasma gelatinous mass  Is secreted from ciliary body  Is 99% vitally water  Contains collagen fibrils and  Fills both chambers  Maintains the intraocular hyaluronan  Is in contact with retina, ora pressure and inflates the globe serata and optic disk of the eye  Degeneration due to ageing  Provides nutrition for the changes avascular ocular tissues: cornea,  Helps to cushion the eye trabecular meshwork, lens during trauma  Presence of immunoglobulins to  Minor role as a metabolic defend against pathogens sump  For refractive index  Prevents eye dryness 5.Retina : key bridge between the light that enters your eyes and the images you see  2 parts: macula and peripheral  Peripheral retina fills at the edges retina of the  Macula is the center of the vision visual field (fovea)  Contains many types of cells Photoreceptors convert Ganglion cell axons pass the light energy into Transmit to ganglion cells across the surface of the electrical via connector neurones retina and end at the *contains vitA linked to optic disk protein opsin Rods photoreceptors Cones photoreceptors (peripheral retina) for (macula) for vision in light vision in low light and and color detection of movement  RPE is composed of a single layer of RPE cells  Blood supply from central retinal artery and vein and from choroid  Blood-retinal-barrier: consisting of tight junctions between the endothelial cells of the retinal vessels and between the RPE cells  The barrier isolates the retina from systemic circulation  Is an extension of central nervous system 6.Optic nerve: critical to your vision Transmits electrical impulses from the eye to the brain The ganglion cell axons in the retinal nerve fiber layer make a right-angled turn into the optic nerve at the disk which has no photoreceptor (blind spot) Optic disk has a central cavity (optic cup) which is pale in comparison with the redness of the nerve fibers “Confiden ce is everything in this THANK YOU business”