Introduction to Ocular Anatomy Tracy Cruz, C.O.A, C.S.A, O.C.S. Objectives Identify the anatomy of the . Explain the basic physiology of the parts of the eye. Briefly discuss various surgeries related to different parts of the anatomy.

General Size / Volume

Eyelids

Hordeolum/Stye Chalazion Blepharitis with Scurf Meibomian Glands Meibomian gland dysfunction is blockage or some other abnormality of the Meibomian glands so they don’t secrete enough oil into the tears. Because the tears then evaporate too quickly, MGD is associated with dry eye syndrome. MGD is one form of blepharitis (inflammation of the eyelids). Dermatochalasis

Dermatochalasis is a medical condition, defined as an excess of skin in the upper or lower eyelid, also known as "baggy ." It may be either an acquired or a congenital condition. It is generally treated with blepharoplasty. Ptosis

“Ptosis” is the medical term for a drooping upper eyelid. Eyelid drooping can sometimes affect your vision if it's severe. Ptosis isn't a specific disease but a manifestation of developmental or acquired abnormalities. In most cases, correction requires surgery, but some causes are diseases that can be treated medically. Eyelid Malposition

Five Layers Epithelium Bowmans membrane Storma Descemets membrane Endothelium

Cornea

1. The . This outer layer of the cornea is five to seven cells thick and measures about 50 microns — making it slightly less than 10 percent of the thickness of the entire cornea. Epithelial cells are constantly being produced and sloughed off in the tear layer of the surface of the eye. The turnover time for the entire corneal epithelium is about one week. Cornea

2. Bowman’s layer . This is a very thin (8 to 14 microns) and dense fibrous sheet of connective tissue that forms the transition between the corneal epithelium and the underlying stroma. Cornea

3. The corneal stroma . This middle layer of the cornea is approximately 500 microns thick, or about 90 percent of the thickness of the overall cornea. It is composed of strands of connective tissue called collagen fibrils. These fibrils are uniform in size and are arranged parallel to the cornea surface in 200 to 300 flat bundles called lamellae that extend across the entire cornea. The regular arrangement and uniform spacing of these lamellae is what enables the cornea to be perfectly clear Cornea

4. Descemet’s membrane . This very thin layer separates the stroma from the underlying endothelial layer of the cornea. Descemet's (pronounced "DESS-eh-mays") membrane gradually thickens throughout life — it's about 5 microns thick in children and 15 microns thick in older adults. Cornea

5. The corneal endothelium . This is the innermost layer of the cornea. The back of the endothelium is bathed in the clear aqueous humor that fills the space between the cornea and the and . The corneal endothelium is only a single layer of cells thick and measures about 5 microns. Most of the endothelial cells are hexagonal (six-sided), but some may have five or seven sides. The regular arrangement of these cells is sometimes called the endothelial mosaic. Tear Film and

Conjunctiva: A thin, clear, moist membrane that coats the inner surfaces of the eyelids (palpebral conjunctiva ) and the outer surface of the eye (ocular, or bulbar, conjunctiva ). Inflammation of the conjunctiva is called conjunctivitis (pinkeye). Sclera: The tough white outer coat over the eyeball that covers approximately the posterior five-sixths of its surface. The sclera is continuous in the front of the eye with the cornea and in the back of the eye with the external sheath of the optic nerve. The word " sclera " is from the Greek "skleros" = hard. Anterior Chamber

Anterior chamber: The space in the eye that is behind the cornea and in front of the iris. The cornea is the outer, transparent, dome-like structure that covers the iris, pupil, and the anterior chamber . Anterior Chamber Angle Closed Angle Intraocular Pressure (IOP)

The term ocular hypertension usually refers to any situation in which the pressure inside the eye, called intraocular pressure, is higher than normal. Eye pressure is measured in millimeters of mercury (mm Hg).

Normal eye pressure ranges from 12-21 mm Hg, and eye pressure of greater than 22 mm Hg is considered higher than normal . When the IOP is higher than normal but the person does not show signs of , this is referred to as ocular hypertension. The pressure is necessary to maintain the eye’s shape, nourishment, and function. Increased IOP: can cause ON damage and vision loss one sign of possible glaucoma may need medical /surgical treatment Hypotony Hypotony is usually defined as an intraocular pressure (IOP) of 5 mm Hg or less. Low IOP can adversely impact the eye in many ways, including corneal decompensation, accelerated cataract formation, maculopathy, and discomfort. When the eye pressure is too low it can cause several distortions of the , and cornea that can degrade vision. Treatment of hypotony is especially important when it is associated with visual loss. Extraocular Muscles

Direction of Action of Intraocular Muscles Iris

The sphincter muscle functions to constrict the pupil in bright light ( pupillary light reflex ) or during . The dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye , running radially in the iris and therefore fit as a dilator. The pupillary dilator consists of a spoke like arrangement of modified contractile cells called myoepithelial cells. Dilating Drops (Red Top Bottles) Cycloplegic drugs are generally muscarinic receptor blockers. These include atropine, cyclopentolate, homatropine, scopolamine and tropicamide. They are indicated for use in cycloplegic refraction (to paralyze the in order to determine the true of the eye ), the treatment of .and also to reduce painful ciliary muscle spasm.

A mydriatic drug is an agent that induces dilation of the pupil. Drugs such as tropicamide are used in medicine to permit examination of the retina and other deep structures of the eye. Pupil Constricting Eye Drops (Green Top Bottles)

Miotics are eye drops that stimulate the parasympathetic nervous system causing the pupil of the eye to become smaller. ... Pilocarpine (one of the miotics) has been used for almost 150 years for the treatment of glaucoma. Crystalline Lens

Crystalline Lens. The lens is a transparent structure in the eye that is suspended immediately behind the iris that brings rays of light to a focus on the retina. The crystalline lens is the name given to the natural lens that humans are born with. Cortical Cataract

Vitreous Vitreous: A clear, jelly-like substance that fills the middle of the eye. Also called the vitreous humor, "humor" in medicine referring to a fluid (or semifluid) substance. Retina

Cones and Rods

Cone: A type of specialized light-sensitive cell (photoreceptor) in the retina of the eye that provides color vision and sharp central vision. By contrast, the rods are the retinal photoreceptors that provide side vision and the ability to see objects in dim light ().

Rod: A type of specialized light-sensitive cell (photoreceptor) in the retina of the eye that provides side vision and the ability to see objects in dim light (night vision). By contrast, the cones are the retinal photoreceptors that provide sharp central vision and color vision. Retinal Vessels

The retinal blood vessels are the central retinal artery and vein, and their branches. The arteria centralis retinæ and its accompanying vein pierce the optic nerve, and enter the bulb of the eye through the porus opticus.

Choroid. The extensive vascular netowrk layered between the retina and sclera. Its function is to provide nourishment to the outer layers of the retina and dissipate heat. It is part of the uveal tract. Optic Nerve

Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images.

Glaucomatous Progression of Optic Nerve Damage Visual Pathway Types of surgery

Cataract surgery- is the removal of the natural lens of the eye that has developed an opacification, which is referred to as a cataract, and its replacement with an . IOL Exchange – surgical procedure that can be done if the patient has an IOL related problem during your procedure or some other type of complication develops, certain aspects of the surgery can be adjusted or redone. This includes repositioning the IOL or removing it and replacing it with a different lens .

Pterygium excision - Pterygia are wing-shaped folds of conjunctiva and fibrovascular tissue that invade the superficial corneal layers. ... Here, a visually-significant pterygium is removed and a conjunctival autograft is placed in the area of resection to reduce the risk of recurrence.

Superficial Keratectomy- is surgical removal of corneal epithelium plus sub- epithelial fibrous, fibrovascular, or dystrophic tissue in the front corneal layers.

DMEK – ( Descemet Membrane Endothelial Keratoplasty)- is a partial-thickness cornea transplant procedure that involves selective removal of the patient's Descemet membrane and endothelium, followed by transplantation of donor corneal endothelium and Descemet membrane without additional stromal tissue from the donor. Types of surgery cont’d

DSEK – ( Descemet's Stripping with Endothelial Keratoplasty) is a partial thickness cornea transplant procedure that involves selective removal of the patient's Descemet membrane and endothelium, followed by transplantation of donor corneal endothelium in addition to donor corneal stroma. The transplanted tissue is approximately 100-200 microns thick. DSEAK – (Descemet’s Stipping Automated Endothelial Keratoplasty) is DSEK in which the donor tissue is prepared using an automated keratome.

DWEK – ( Descemetorhexis Without Endothelial Keratoplasty) is a proposed term to describe the surgical removal of Descemet membrane (DM) without subsequent endothelial transplantation, in the treatment of Fuchs Endothelial Corneal Dystrophy (FECD).

DALK – ( Deep anterior lamellar keratoplasty) is a surgical procedure for removing the corneal stroma down to Descemet's membrane. It is most useful for the treatment of corneal disease in the setting of a normally functioning endothelium.

PK – (P enetrating keratoplasty) or traditional corneal transplant surgery, a circular button-shaped, full-thickness section of tissue is removed from the diseased or injured cornea using either a surgical cutting instrument called a trephine or a femtosecond laser. Thank You!!!!