Presented by Linda Martien, CPC, CPC-H, - PowerPoint Presentation

Presented byLinda Martien, CPC, CPC-H, CPMA Anatomy for ICD-10The Eye and Ocular Adnexa

Objectives – the Eye and Ocular AdnexaAfter this session, you should be able to: Describe the functions of the:EyelidLacrimal SystemOrbitConjunctiva, Sclera, Cornea, Iris, Ciliary Body and LensChoroid, Retina, Vitreous Body, and GlobeOptic Nerve and Visual Pathways

Objectives – the Eye and Ocular AdnexaExplain how the optic nerve and visual pathways impact the eyesIdentify infectious diseases of the eye and ocular adnexa Identify neoplasms of the eye and ocular adnexaIdentify other diseases and conditions of the eyes, such as:CataractsGlaucomaVisual disturbancesBlindness

Objectives – the Eye and Ocular AdnexaIdentify newborn conditionsDefine congenital anomalies and the impact they have on the other organs and body functionsUnderstand key differences between ICD-9 and ICD-10Describe a variety of diseases and disease processes affecting the eye and ocular adnexa Compare and contrast the code assignments from both ICD-9 and ICD-10

The Eye and Ocular Adnexa

The Eye and Ocular AdnexaFirst Layer: Fibrous tunica (scleretic coat) – external layer of the eye and is divided into two parts, the sclera (the white of the eye) and the anterior cornea.The sclera includes:Episcleral laersSchlemm’s canal Trabecular meshworkThe cornea includes: The limbus The following layers: Epithelial layer Bowman’s layer Stroma layer Descemer’s layer Endothelium

The Eye and Ocular AdnexaSecond Layer: Vascular tunic (uvea or choroid coat). Middle layer of the eye pigmented with melanin. Provides the eye with its blood supply and forms the iris Structures contained in this layer are:ChoroidCapillary lamina of choroidsBruch’s membrane Ciliary BodyCiliary processes:Ciliary muscle Iris Stroma Pupil Iris dilator muscle Iris sphincter muscle

The Eye and Ocular AdnexaThird Layer: Retina – inner layer of the eye which is composed mostly of nervous tissueIt contains:CellsPhotoreceptor cells – rods, cones, horizontalBipolar cellsRetinal ganglion cells LayrsRods and cones Retinal pigment epithelium Other Macula Foveola Fovea

The Eye and Ocular AdnexaOther parts of the eye include: Anterior segmentAnterior chamberAqueous humorPosterior chamberLensPosterior segment Vitreous body (humor)Other Globe Eyelids Lacrimal system Orbit Optic nerve and visual pathways

Anatomy and FunctionConjunctivaClear, moist membrane made up of non-keratizing epithelium. It covers the sclera and lines the inside of the eyelids. The conjunctiva that coats the inner aspect of the eyelids is the palpebral conjunctiva, the covering on the outer surface of the eye is the ocular or bulbar conjunctiva.Sclera Protective, outer layer which maintains the shape of the globe; provides attachment for extraocular muscle insertion and is continuous with the dura mater and the cornea.Episcleral layerStromaLamina fuscaEndothelium

Anatomy and FunctionCorneaTransparent fibrous coat covering the front of the eye; works with lens to refract light; accounts for about 2/3 of the eye’s optical power. Light is admitted through the cornea. The cornea has five layers:Corneal epithelium layer – thin multi-cellular tissue layer, fast growing, easily regenerates. Made of non-keritinized statified squamous epithelium and has several layers, of which the top, exposed layer sheds constantly. The basal layer regenerates cells continuously.

Anatomy and FunctionCornea (cont’)Bowman’s LayerAlso know as the anterior limiting membrane – condensed layer of collagen that protects the stromal layerCorneal Stroma LayerTransparent, thick, middle layer containing collagen fibers along with interconnected keratocytes – functions to the general repair and maintenance of the cells of the cornea Descemet’s Membrane LayerKnown as the posterior limiting membrane, thin acellular layer lying between the corneal proper substance and the corneal endothelium; basement layer of the endothelium and is composed of collagen from the stromal layer.

Anatomy and FunctionCorneal EndotheliumSingle layer of simple squamous mitochondria rich cells responsible for regulating flue and solute substances between the aqueous and corneal stromal compartments. It sits in the aqueous humor and the cells do not regenerate. Impacts fluid regulation that maintains the cornea in a slightly dehydrated state. I

Anatomy and FunctionSchlemm’s Canal and Trabecular MeshworkAlso know an as the scleral venous sinus – an endothelium lined tube in the eye and collects aqueous humor from the anterior chamber and delivers it to the bloodstream. Inner lining is the trabecular meshwork which manages the outflow resistance of the aqueous humor. ChoroidPart of the vascular tunic, highly vascular structure composed of capillaries and small arteries and veins. Lies between the sclera and retina. It provides oxygen and other nutrients to the outer layers of the retina. Together with the ciliary body and iris, it forms the uveal tract.

Anatomy and FunctionCiliary BodyCircumferential tissue composed of ciliary muscle and processes. The muscle of the ciliary body controls accomodation, the process where the eye changes optical power to maintain a clear image (focus). Also regulates flow of aqueous humor into Schlemm’s Canal.Is coated by a double layer of ciliary epithelium which produces the aqueous humor. The inner layer covers the vitreous body and is continuous from the neural tissue of the retina. Outer layer is greatly pigmented and comprises the cells of the dilator muscles in the iris.

Anatomy and FunctionIrisThe colored part of the eye, responsible for controlling the size and diameter of the pupil and the amount of light reaching the retina. It is attached to the sclera and the anterior ciliary body, together know as the uvea. Two layers – stromal and pigmented epithelial cells.In front of the iris the Trabecular Meshwork where the aqueous humor drains out of the eye. Primary location where intraocular pressure is regulated. Failure to control this pressure leads to diseases such as glaucoma.

Anatomy and FunctionRetinaLight sensitive tissue lining covering about 65% of the back inner surface of the eye. Rod and cone photosensitive cells convert light energy into signals that are carried to the brain via the optic nerve.In the middle of the retina is the small dimple named the fovea or fovea centralis. Most color perception and sharpest vision is located here. Two distinct visual systems of the eye – photopic and scoptopic vision.Photopic – more sensitive to light, not color sensitive and made up of rod cellsScoptopic – less sensitive to light, color sensitive and made up of cone cells

Retina Anatomy

Anatomy and FunctionRetina (cont’)Rods – single type cell supports vision in low light. Cylindrical in shape and located in the outer edges of the retina. Mainly used in peripheral vision.Cones – three types of cone cells, each absorbs light from a different portion of the spectrumLong wavelength light (reds) Middle wavelength light (greens)Short wavelength light (blues)

Rod and Cone Anatomy

Anatomy and FunctionCone cells (cont’)Special type of neuron cell that is responsible for color perception and visual acuity.Function best in bright light Macula – contains the cone cellsNeural AnatomySynaptic terminal, a bulb at the end of the axon (part of a neuron) where neurotransmitter molecules are stored and released.Generates a synapse (nerve signal)Retinal ganglion cells collect the visual information and transmit it to the thalamus, hypothalamus and the mesencephalon (middle brain) RGCs have a long axon that extends to the brain. These form the optic nerve.

Anatomy and Function Anterior ChamberThe space in the eye filled with aqueous humor, it lies between the iris and the corneal endothelium.Aqueous HumorFlows through the pupil into the anterior chamber through a narrow opening between the front of the lens and the back of the iris, through Schlemm’s canal and into the anterior ciliary veins. It’s main function is to provide optic power to the cornea but also maintains intraocular pressure, shapes the globe, provides nutrients to avascular optical tissue and carries away products from that tissue.

Anatomy and FunctionPosterior ChamberThe space behind the iris and in front of the lens. It holds the aqueous humor for later transport to the anterior chamber.LensThe front of the iris – held in place by zonules (rings of fibrous strands). When relaxed the lens flattens (increased diameter), when contracted it comes more spherical (decreased diameter) = curvature of the lense which allows the eye to adjust its focus between near and far objects. The opening is controlled by the autonomic nervous system.

Anatomy and FunctionEyelidsThe folds of skin above and below the eyes.Tarsal platesTwo plates that are thick, elongated plates of dense connective tissue found in each eyelid – form and support the eye Epicanthic foldsLocated in the upper eyelid from the nasal bone to the inferior side of the eyebrow – covers the inner corner (medial canthus) of the eyeMeibomian glands(tarsal glands) are sebaceous glands at the rim of the eyelids. Responsible for the supply of sebum, an oily substance that prevents the evaporation of tear film of the eye which stops tears from spilling onto the cheeks. Also make the lids airtight when closed. Palpebral fissureThe separation between the upper and lower eyelids

Eyelid Anatomy

Anatomy and FunctionGlobeThe globe of the eye (bulbus oculi) is the eyeball without its appendages. It consists of a wall enclosing a cavity filled with fluid. It is surrounded by the socket (orbit) and covered externally by the eyelidsLacrimal system Contains structures for tear production and drainage. Consists of lacrimal glands, lake, canaluculi, puncta and sac and nasolacrimal ducts.Glands – Secrets tears with excretory ducts and moves fluid to the surface of the eyeLake – a tear pool located in the lower conjunctival cul-de-sacCanaluculi – narrows channels in each eyelid that drains tears from the lacrimal lace to the lacrimal sac.Sac – holds tears and drains into the nasolacrimal ducts which carries tears into the nasal cavity

Lacrimal Anatomy

Anatomy and FunctionOrbitThe socket in the skull which the eye and its appendages are locatedVitreous BodyAlso called the Vitreous Humor, is the transparent, colorless gel that fills the space between the lens and the retina. Produced by specific retinal cells. Assists in keeping the retina in place by pressing against the choroids and adhering to the retina in three areas. Optic Nerve and Visual PathwaysAlso referred to as a cranial nerve (CN) IITransmits visual information from the retina to the brain.Three layers which contain retinal ganglion cell axons

Differences Between ICD-9 and ICD-10 Eye and Adnexa CodingIn ICD-10-CM, a new chapter, Chapter 1, has been added specifically for diseases of the Eye and Adnexa. In ICD-9-CM they are included in a single chapter, Disease of the Nervous System and Sense Organs (Chapter 6)Combination codes have been expanded in ICD-10-CM.Example:Diabetic retinopathy with or without macular edema ICD-10 E08.3xICD-9 250.5x, 362.01-362.06, 362.07

Documentation Elements for ICD-10Laterality, meaning the side of the body affected, must be documented as right, left, or bilateral Eye abbreviations:OS – left eye (oculus sinister)OD – right eye (oculus dexter)

Diseases, Disorders, Injuries and Other Conditions of the Eye and AdnexaRetinal detachmentsThe retinal is pulled or lifted away from its normal position Can occur by retinal break, hole or tear, by injury or trauma, or in patients who are predisposed, such as those with severe myopia (near sightedness), after cataract surgery or patients with proliferative diabetic retinopathy.Breaks occur when the vitreous gel separates from its attachments to the retina, typically in the peripheral parts of the retina.See H33.xxx series in ICD-10

Retinal DetachmentsRhegmatogenous retinal detachment Due to a break, hole or tear in the retinaExudative, serous or secondary retinal detachmentOccurs due to inflammation, injury or vascular abnormalities that result in fluid accumulating beneath the retina without a break, hole or tearTractional retinal detachmentOccurs when fibrovascular tissue pulls the sensory retina from the retina pigment epithelium. Caused by inflammation, injury or neovascularization.

Retinal Detachment

CataractsPartial or complete clouding on or in the lens or lens capsule which may obscure vision.Infantile or juvenile cataractsOccur early in life Used interchangeably with “congenital cataracts” but are not the sameCongenital cataracts are present at birthInfantile cataracts present early in life but are not present at birthConditions or diseases associated with congenital cataracts are:Chondrodysplasia syndrome Conradi syndromeDown syndromeEctodermal dysplasiaGalactosemia Lowe syndrome Pierre-Robin syndrome Trisomy 13

CataractsCataracts with NeovascularizationTermed rubeosis, is an abnormal blood vessel growth in the front of the eye. Not unusual in diabetes. Can obstruct drainage of aqueous fluid from the front of the eye causing eye pressure to be elevated Cataracts in Inflammatory Disorders and Degenerative DiseasesCaused by underlying inflammatory disorder, such as chorioiditis, or a degenerative disease, such as degenerative myopia.Drug Induced CataractsOne that has been induced by exposure to a drug, such as an oral, topical, or inhaled steroid. Long term use of statins and phenothiazines are also included in this category.

Disorders of Refraction and AccommodationMyopiaAlso call nearsightedness – occurs when the eyeball is too long or the lens is too spherical. Distant images are brought to focus in front of the retina but are quickly out of focus before the light hits the retina. HypermetropiaAlso called farsightedness – occurs when the eyeball is too short or the lens has flattened out or is inflexible. The light rays entering the eye will not be brought into focus by the time they reach the retina.

GlaucomaGroup of diseases of the eye characterized by damage of the optic nerve. Usually but not always caused by an increase in intraocular pressure (IOP) leading to progressive, irreversible loss of vision. The loss of ganglion cells (RGC) is in a pattern and is considered a type of optic neuropathy which can lead to permanent damage to the optic nerve, loss of peripheral vision and eventually, blindness. Open angle glaucomaClosed angle glaucoma

GlaucomaOpen Angle GlaucomaChronic Progresses more slowly than closed angle glaucomaIncluded in this type is Primary Open-Angle Glaucoma (POAG)Normal Tension GlaucomaA type of Open Angle Glaucoma also called Normal Tension Glaucoma (Low Pressure Glaucoma), similar to POAG, may cause optic nerve damage and visual field loss but the IOP remains in the normal range.Closed angle glaucomaAppears rather quickly and often painful. May be caught more quickly as symptoms are acute and noticeable.

GlaucomaInfantile GlaucomaAlso know as congenital glaucoma is present at birth and is usually diagnoses before the age of one. Phacolytic GlaucomaLeakage of lens protein from a mature cataract into the aqueous fluid, blocking fluid outflow and causing increased IOPAssociated with other Eye ConditionsChamber angle, iris and other anterior segment anomalies may cause glaucoma Secondary GlaucomaMay develop in the presence of an eye infection, inflammation, tumor, enlarged cataract, or eye injury. Also seen in advanced cases of cataracts or diabetes and may be caused by drugs, such as steroids.

Infectious Diseases of the EyeConjunctivitis – infection of the conjunctiva that results in redness, swelling, irritation and/or inflammation of the conjunctiva Allergic conjunctivitisReaction to an external force or allergen. Mast cells release histamine and blood vessels are stimulated causing dilation, irritation of nerve endings and increased tearingBacterial conjunctivitisCost common is pyogenic (puss producing), causing irritation and grittiness or scratchiness, a yellow or greyish stringy, opaque, mucopurulent dischargeChemical conjunctivitisAlso known as irritant or toxic conjunctivitis, can be very painful. Necrosis of the conjunctiva may occur.

Conjunctivitis

ConjunctivitisFollicular conjunctivitisIdentified by lymphoid follicles in the conjunctival stroma. They are elevated, having germinal centers which are a response to an infectious agent. Viral conjunctivitisCommonly know as “pink eye”, is typically associated with an infection of the throat or upper respiratory tract or a common cold. Ad adenovirus is the most common causative agent.KeratoconjunctivitisInpacts both cornea and conjunctiva

BlepharitisInflammation of the eyelash follicles along the edge of the eyelid. Typically caused by seborrheic dermatitis, rosacea, a type of bacteria or a combination of these conditions.Excess oil is produced by the glands of the eyelid. To much oil causes the normal bacteria to overgrow. May be related to repeated styes and chalazia.

BlepharitisAnterior blepharitisAffects the outside front of the eyelid Posterior blepharitisAssociated with dysfunction of the meibomian glands of the eyelidsBoth types typically occur at the same time, but in different degrees of severity

Corneal UlcersAn open sore on the corneaFrequently caused by infection in the eye due to:Bacteria – improper contact care, extended contact wearing Viruses – herpes simplex (cold sores), varicella (chickenpox, shingles)Fungi – improper contact care, overuse of eye drops containing steroidsA protazoan - acanthamoeba

Corneal UlcersOther less common causesScratches (abrasion) – caused by trauma, chemical burns Foreign bodiesInadequate eye closure – Bells PalsySeverely dry eyes – leaves eyes without germ fighting tearsSymptoms of corneal ulcers are red eye, pain, foreign body sensation, tearing, pus or thick discharge from the eye, blurry vision, swollen eyelids and/or a white or grey round spot on the cornea that is visible.

DacryoadenitisInflammation of the tear producing lacrimal gland and is usually caused by bacteria or a virus which includes mumps, Epstein-Barr virus, staphylococcus, and gonococcus. Noninfectious chronic dacryoadenitis is typically caused by sarcoidosis, thyroid eye disease, or orbital pseudotumors.

EndophthalmitisSevere swelling and inflammatory condition within intraocular cavities, affective the aqueous or vitreous humor. Typically caused by bacteria, fungi or other microorganisms or may be a complication of eye surgery, such as when there is a part of the natural lense that is retained in the eye. Endogenous (metastatic) – results from the spread of an organism from a distant source of infection. Occurs when there is a direct assult of an infectin or by changes in the vascular epithelium caused by substrates released during infection. Intraocular destruction occurs.Exogenous – results from a complication of ocular surgery, foreign bodies within the eyeball, and/or blunt or penetrating ocular trauma.

KeratitisInflammation of the cornea with intense pain and some impaired vision. Types are:Filamentary keratitis – with twised filaments of mucoid material on the surface of the cornea Photokeratitis – painful, inflammed cornea that occurs due to overexposure to UV lightsPunctate keratitis – occurs with death of cells on the surface of the cornea, fiber like deposits form Superficial keratitis – typically does not cause corneal scarring

ChalazionWhen the Meibomian gland (tiny oil gland) in the eye is blocked a chalazion develops. Symptoms include eyelid tenderness or pain, increased tearing, and sensitivity to light

Cytomegalovirus RetinitisCaused by the herpes group of viruses, most people are exposed to CMV during the course of their lifetime but typically only those with a weakened immune system become ill with the infection, such as: AIDSOrgan transplantBone marrow transplantDrug that suppresses immune systemChemotherapy

Neoplasms of the EyeAll parts of the eye may be affected neoplasms, which may be primary (rhabdomyosarcoma, retinoblastoma), secondary (metastatic), or benign (dermoid cyst)Eyelid tumors Most common is basal cell carcinoma, it affects the skin and is slow growingOthers includeSquamous carcinomasMalignant melanoma

Neoplasms of the EyeSquamous CarcinomaNodular squamous conjunctival carcinoma is a form of squamous carcinoma that grows rapidly and is invasive. This type usually extends beneath the conjunctival epithelium, thus has the potential to be metastatic. MelanomaBeing in the melanocytes which are cells that produce melanin, the pigment responsible for variations in skin color. Melanoma can also develop in other parts of the eye such as the choroid, conjunctiva, lacrimal gland, and retina because there sites also contain melanin producing cells.

Neoplasms of the Eye - MelanomasLentigo maligna melanoma (LMM) lesions are flat and tan with irregular borders and become increasingly mottled as they grow. This type spreads slowly, stays in the superficial layers and does not metastize. Nodular melanoma (NM) lesions are slightly elevated, blue black, and resemble blood blisters. This type grows rapidly and is normally fully invasive into other parts of the body

Neoplasms of the EyeIntraocular Tumors – uveal melanoma is the most common of intraocular tumors and may occur in the choroid, iris and ciliary body. Anther common tumor is intraocular lymphoma, a subtype of primary nervous system lymphoma. Orbital Dermoid Cysts – mass of histologically normal tissue in an abnormal location.Nevus – benign by definition, nevi are circumscribed malformations not due to external causes and are composed of melanocytes.Giant Choroidal Nevi – often confused with melanoma but characteristics are different.

Signs and Symptoms of the EyeUsually a symptom of other disorders, such as:Vascular diseaseNeurological diseases and conditions Muscular disordersCancerTraumaDiabetesCongenital conditions

Signs and Symptoms of the EyeBlurred Vision – refers to loss of sharpness of vision and the inability to see small details. Diplopia – double visionNystagmus – abnormal eye movement usually resulting in blurred vision. The type of nystagmus depends on the underlying cause.Horizontal nystagmus is a jerking movement that goes from side to side.Vertical nystagmus refers to up and down movement, usually indicates a problems with the CNSChildhood nystagmus is typically associated with eye defects such as retinal disorders. Most of familial and not a symptom of an underlying disease In adults, nystagmus can be a symptom of an underlying disease, such as multiple sclerosis or head trauma.

ScotomasBlind spots - areas in the field of vision that have been partially altered. A scotoma results in an area of partially diminished or entirely deteriorated visual acuity, surrounded by a normal field.Annular scotoma (ring) – a circular area of depressed vision that involves a fixation point Paracentral scotoma – a blind spot that is adjacent to the fixation pointScintillating scotoma – a localized area of diminished vision edged by shimmering colored lights. This is the visual aura that usually preceeds a migraine headache.

Visual Impairment and BlindnessDefined – when a person is lacking in visual perception due to physiological or neurological factors they are considered to have a form of visual impairment or blindness. Visual impairment – any chronic visual deficit that impairs every day functioning and is not correctable by eyeglasses or contact lenses. Residual vision and light perception with the ability to tell dark from light may be apparent.Total blindness – the complete lack of form and there is no visual light perceptionLegal blindness – The WHO and USA differ in definition of legal blindness

Legal BlindnessWHO – visual impairment on a ‘Profound’ to ‘Total’ levelUSA – starts the definition earlier, with legal blindness starting one level earlier at the ‘Severe Visual Impairment’ level

Newborn and Congenital ConditionsAmblyopia – also known as ‘lazy eye’, a loss of vision in an eye which is otherwise healthy. May be caused by other conditions, such as strabismis, refractory disorders, or trauma.Coloboma – a congenital malformation where part of the eye does not form due to failure of fusion of an embryonic feature called the intraocular fissure. This causes a gap between those structures of the eye that fail to close up before a child is born. The effect on eyesight is dependent on the size of the gap and can be mild or more severe.

ColobomaLens – a piece of lens is absent, usually appears with a notchRetina (macula) – the center of the retina does not develop normally. Normal eye development is interrupted or following inflammation of the retina is uteroOptic disc – the optic disc is slight or largely hollowed out

Retinopathy of PrematurityAbnormal blood vessel development in the retinal of a premature infant. There are five stages of ROP:Stage 1 – mild abnormal blood vessel growthStage 2 – moderate abnormal blood vessel growth Stage 3 – severe abnormal blood vessel growthStage 4 – severe abnormal blood vessel growth with partially detached retinaStage 5 – Severe abnormal blood vessel growth with total retinal detachment

StrabismusA condition when the eyes are not parallel and are not aligned with each other. One eye will turn or wander in or out, or up or down. It usually involves lack of coordination between the extraocular muscles that prevent the gaze of each eye coming to the same point in space.

Eye Muscle Anatomy Muscle Primary Function Medial rectus moves eye towards nose Lateral rectus moves eye away from nose Superior rectus raises eye Inferior rectus lowers eye Superior oblique rotates eye Inferior oblique rotates eye

Types of StrabismusEsotropia – eye are typically crossed, there is double vision, the eyes are not aligned in the same direction, uncoordinated eye movement and/or visual loss in one eye. Paralysis of the lateral rectus muscle caused an abnormal inward deviation of one eye.Exotropia – the eye is turned out, there is crossed diplopia.

Types of Esotropia and ExotropiaMonocular – affecting one eyeAlternating – fixation alternates between the right and left eye so that at one moment the right eye fixates and left eye turns inward, and in the next, the left eye fixates and the right turns inward.Intermittent – not always present, it may be visible when looking at close objects or when looking at distant objects and not close ones. Most intermittent types are accommodative, where an attempt is made to focus the eyes but they converge, activating the accommodation reflex.

Eye InjuriesAbrasions – the wearing away of the layer of the eye (cornea or conjunctiva) as a result of applied frictionForeign body – if trapped under the eyelid can cause abrasion and require manual extraction. In more serious cases the FB results in intraocular penetration.Eyelid and ocular laceration – can be minor, when the lid margin or tarsal plate is not affected, or major, affecting the medial portion of the eyelid and lead to lacrimal canaliculus. Intraocular laceration can penetrate the eyeball, have eye tissue prolapse, have a foreign body, and may cause a rupture of the eyeball.

Ocular BurnsTwo types of burns of the eye, thermal and corrosive. Burns that come from a heat source (excluding the sun) such as fire, electricity, or radiation are thermal burns. Burns caused by chemicals are considered corrosive.Chemical (corrosive) eye injuries – can be defined as tissue damage in the eye or a serious decrease in vision due to exposure to a chemical or irritant. Mild burns disrupt or damage only the surface cells and heal quickly. If stronger it can go deeper into the next layer of the cornea, the stroma, which may irreversible, and even possibly causing cataracts and/or glaucoma.

Chemical Burn CategoriesIrritants – typically have a normal pH and cause more irritation to the eye than damage (pepper spray)Alkali burns – these chemicals penetrate the surface of the eye and can cause severe injury to the eye. Examples are ammonia, lye, and lime, which are in cleaning products, drain cleaners, and oven cleaners.Acid burns – usually less severe than alkali burns, does not penetrate the eye as easily. An exception is hydrofluoric acid. This chemical usually only damages the front of the eye but still can cause damage to other layers resulting in blindness. Examples are acetic acid and sulfuric acid, which are in vinegar, fingernail polish, and automobile batteries.

Postoperative ComplicationsKeratopathy (bullous aphakic) – following cataract surgery (ABK) – corneal edema, caused by changes in the corneal epithelium, allowing it to be in an abnormal state of hydration. When the endothelial cells are damaged the remaining cells rearrange themselves to cover the posterior corneal surface. The cells become irregular and enlarged. The endothelium becomes unable to act as a pump to the cornea and the stroma begins to swell. Folds are seen in the Descemet membrane.

Questions

Lab – Cow Eye Dissection The cow eye is similar to the eye of a human. By dissecting and examining the anatomy of a preserved cow eye you can learn how your own eye forms images of the world around you and sends these images to your brain.

Observation: External Anatomy Look carefully at the preserved cow eye. The most noticeable part of the eye is the large mass of grey tissue that surrounds the posterior (back) of the eye and is attached to the sclera. The second most noticeable part of the eye is the cornea, located in the anterior (front) part of the eye. Due to the fact that the eye has been preserved, the cornea is cloudy and bluish-grey in color. It may also be wrinkly and seem a bit “deflated”. On the posterior side of the eye, nestled in the fat and muscle tissue, there is a noticeably round protuberance that feels stiffer than the surrounding tissue. This is the optic nerve, and it sends the images collected in the eye to the brain.

Dissection: Internal Anatomy1. Place the cow eye on the dissecting tray. Carefully cut away the excess fat and muscle. As you get closer to the actual eyeball, you may notice muscles that are attached directly to the sclera and along the optic nerve. These are the extrinsic muscles that allow a cow to move its eye up and down and from side to side. Keep cutting along the sclera, separating the membrane that attaches the muscle to it. After removing the excess tissue, the sclera and optic nerve should be exposed but still intact.

Internal Anatomy (cont.’)2. Using a sharp scalpel, cut through the sclera around the middle of the eye so that one half will have the anterior features of the eye (the cornea, lens, iris, and ciliary body) and the other half will contain the posterior features (most noticeably where the optic nerve is attached to the eye). The inside of the eyeball is filled with fluid. This is the vitreous humor. Depending on how the specimen was preserved, it will be either a dark liquid that will flow out easily, or a slightly gelatinous material that you can pour out to remove. In a living eye, the vitreous humor is clear and gel-like.

Internal Anatomy (cont.’)3. Flip the anterior half of the eye over so the front of it is facing upward. Using a pair of sharp scissors, cut the cornea from the eye along the boundary where the cornea meets the sclera. When the scissors have cut in far enough, a clear fluid will start to seep out – this is the aqueous humor. While cutting out the cornea, be careful to not accidentally cut the iris or the lens. After removing the cornea, pick it up and look through it. Although it is cloudy to the degrading of the tissue, it is still fairly transparent. Notice the toughness and strength of the cornea. It is designed this way to protect them ore delicate features found inside the eye.

Internal Anatomy (cont.’)4. With front of the anterior half of the eye facing up, locate the iris. Notice how the iris is positioned so it surrounds and overlaps the lens. This position allows the iris to open and close around the lens to allow different amounts of light into the eye. In bright light, the iris contracts to let in less light. In dim light, such as at night, the iris expands to let in more light. 5. Flip the anterior half over and examine the back half. Locate the lens and ciliary body. The ciliary body surrounds the lens, allowing it to change the shape of the lens to help the eye focus on the object it is viewing.

Internal Anatomy (cont.’)6. After examining both sides of the anterior half of the eye, pull the lens out. While the cow was alive, the lens was clear and very flexible. In a preserved cow eye, the lens will most likely have yellowed and become very hard. However, it may still be possible to look through the lens and see its ability to magnify objects. Try this by placing the lens on a piece of paper with writing on it.

Internal Anatomy (cont.’)7. On the posterior half of the eye, there is a thin, tissue-like material that slides easily inside the sclera. This is the retina. The retina contains photoreceptor cells that collect the light entering the eye through the lens from the outside world. These images are sent to the optic disc, the spot where the optic nerve attaches to the eye. At this point, there are no photoreceptor cells; there are only nerves sending images to the brain. Because of this, this place in the eye is often referred to as the blind spot, since no images cant be formed here. To compensate for this blind spot, the other eye often sees the images that the first eye cannot see and vice versa. In the rare occasions where neither eye can see a particular spot, the brain “fills in” the spot using the surrounding background information it receives from the eye.

Internal Anatomy (cont.’)8. Most of the retina is not attached to the eye. Instead, it is held in place by fluids in the eye. There tissue of the retina gathers at the back of the eye where it forms in the optic nerve. This is the only pace where the retina is attached to the eye. Using a pair of tweezers, gently lift the retina off the inside wall of the eye. The retina may tear because it is very delicate. Underneath the retina you will find a very shiny and colorful tissue. This is the choroid coat. The choroid coat is also know as the vascular tunic because it supplies the eye with blood and nutrients. In a human eye, the choroid coat is very darkly covered to minimize the reflection of light which would cause distorted images.

Internal Anatomy (cont.’)9. Notice that the choroid coat in the cow’s eye is very colorful and shiny. This reflective material is the tapetum lucidum, and its reflective properties allow a cow to see at night reflecting the light this is absorbed through the retina back into the retina. While this does allow the cow to see better at night than humans can, it distorts the clarity of what the cow sees because the light is reflected so much. The tapetum lucidum is alos responsible for the “glowing” eyes of animals, such as cats, when a small amount of light reflects off the tapetum lucidum in an otherwise dark room.