02/03/2014. Average Length: 23mm (Infant ~16mm) Approximately the size of a quarter Volume: ~5mL

Transcription

1 Identify the anatomy of the eye. Explain the basic physiology of the parts of the eye. Briefly discuss various surgeries related to different parts of the anatomy. Average Length: 23mm (Infant ~16mm) Approximately the size of a quarter Volume: ~5mL Extraocular Muscles Brain Muscle Primary Function Innervating Nerve Medial rectus Nasal (adduction) CN III (Oculomotor Nerve) Lateral rectus Temporal (abduction) CN VI (Abducens Nerve) Inferior Rectus Superior rectus Upward (elevation) CN III (Oculomotor Nerve) Superior Oblique Inferior rectus Downward (depression) CN III (Oculomotor Nerve) Superior oblique Inferior oblique Rotates towards the nose (incyclotorsion) Rotates away from the nose (excyclotorsion) CN IV (Trochlear Nerve) CN III (Oculomotor Nerve) Lens Medial Rectus Lateral Rectus Superior Rectus 1

2 Muscle Secondary Function Tertiary Function Medial rectus None None Lateral rectus None None Superior rectus Incyclotorsion Nasal (adduction) Common conditions: Ptosis Dermatochalasis Inferior rectus Excyclotorsion Nasal (adduction) Superior oblique Downward (depression) Temporal (abduction) Inferior oblique Upward (elevation) Temporal (abduction) Lids are sagging, eyes appear sleepy, not open all the way Folds or droopy eyelids, extra skin Glands along the lid margin that secret oil into the tear layer to prevent evaporation of the tear film, keeps eyes moist 2

3 a. Lacrimal gland b. Superior lacrimal punctum c. Superior lacrimal canal d. Lacrimal sac e. Inferior lacrimal punctum f. Inferior lacrimal canal g. Nasolacrimal canal Lipid Layer Produced by the meibomian glands Aqueous Layer Secreted by lacrimal glands Secreted by goblet cells in the conjunctiva Mucous Layer Transparent tissue surrounding the sclera Protective layer Vascularized Red eye Dense collagen Avascular ~1mm thick Function: Structural integrity, protection 3

4 Limbus- area where the cornea meets the conjunctiva, where limbal stem cells reside promote growth of new corneal epithelial cells act as a barrier to prevent conjunctival epithelial cells from migrating onto the corneal surface Cornea: 11-12mm wide, 10mm high, 550µm thick 2/3 rd of refractive power of the eye Five layers: Epithelium, Bowman s layer, stroma (90%), Descemet s Membrane, endothelium The ciliary body produces aqueous fluid. The aqueous flows around the lens through the pupil into AC, then drains through TM to episcleral veins to the Schlemm s Canal, then to the orbital veins. The amount of pressure inside the eye Normal between 10-21mmHg The pressure is necessary to maintain the eye s shape, nourishment, and function Increased IOP (ocular hypertension) Can cause ON damage One sign of possible glaucoma Medical and surgical treatment Angle Ciliary body Trabecular Meshwork Aqueous humor (fluid) Iris Open angle Closed angle Low IOP (hypotony) Usually postsurgical (decreased CB production (irdocyclitis), or wound leak, overfiltering bleb Can cause retinal detachment and/or corneal folds Like a deflated balloon 4

5 Sphincter muscle Circular muscle fibers Constricts the pupil In bright light or with accommodation Ciliary body is also a sphincter muscle As the ciliary body tenses, the zonules loosen allowing the lens to fatten and have more accommodative ability (near vision) Dilator muscle Smooth, radial muscle fibers Noradrenaline response fight or flight Dilates the pupil In the dark or relaxed accommodative state Distance Near Vision At the same time the pupils constrict for accommodation. Cycloplegics: Parasympathetic antagonists (parasympatholytics) Act by paralyzing the iris sphincter muscle Also paralyzes the ciliary muscle used in lens accommodation Ex: Tropicamide, Cyclopentolate, Homatropine, Atropine Mydriatics: Sympathetic agonists (sympathomimetics): Act by stimulating the iris dilator muscle Ex: Phenylepherine Miotics Parasympathomimetics Stimulates the iris sphincter, constricts the pupil Allows for increased drainage (used to treat glaucoma) Ex: Pilocarpine, Carbachol Lens: 1/3 of the refractive Power of the eye ~20D Capsule, Nucleus, Cortex Responsible for accommodation A cloudy lens is a cataract Capsular Bag (lens sack) Describe the M&M s analogy Surrounds the lens Broken bag = vitreous prolapse PCO = secondary cataract Responsible for structural integrity of the globe Clear, jelly-like, mostly water Thins in aging causing floaters 5

6 Avascular, clear tissue, light sensitive tissue ~250µm thick (1/4 mm) Macula contains photoreceptor cells: rods/cones Rods: Poor acuity, detect motion Function best in dim light About 125million rod cells Arteries- oxygenated blood sent from the heart to the eye Veins- blood sent away from the eye Cones: Detect color and small details Cluster in the fovea, center of the macula Function best in bright light, daylight conditions About 6million cone cells Fluorescein Angiogram A-B:Pre-injection C: choroidal flush D: Arterial E: Arterial-Venous (Laminar flow) F: Brightest/ Microvasculature visible G-I: recirculation, dye fades; ON stains Vascularized tissue ~500µm thick (1/2mm) Responsible for the Red reflex on slit lamp exam and Red Eye in photos Dark tissue on dissection Latin uva (uvea) = grape Uvea includes: iris, ciliary body, choroid Provides oxygen/ nourishment to outer retina 6

7 The optic nerve, also called Cranial Nerve II (CNII), transmits visual information from the retina to the brain. ~30mm long from posterior globe to orbital apex Temporal retinal fibers stay on same side of brain. Nasal retinal fibers cross to opposite side of brain. Any Questions? 7