2/16/2016

Tear Film Layers Basic Ocular oil Anatomy aqueous

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Lynn E. Lawrence, CMSgt (ret), CPOT, ABOC,COA What functions does each layer of the tear perform?

Healthy Tears A complex mixture of proteins, Lipid Secretion: Meibomian Glands mucins, and electrolytes coated by a lipid layer Left: Transillumination of eyelid showing • Antimicrobial proteins meibomian glands • Growth factors & suppressors of inflammation Right: • Soluble mucin helps stabilize Secretion of lipid tear film at lid margin • Electrolytes for proper osmolarity (295-300) – pH slightly alkaline (7.4) • The lipid layer restricts evaporation to 5-10% of tear flow – Also helps lubricate Why is a tear salty tasting? Where does a contact lens rest?

Lipid Secretion: Meibomian Glands A Healthy Tear Film

What eye is this?

800 nm 8,000 nm 100 nm Transillumination of meibomian glands (WC Posey, Diseases of the Eye, 1902)

How does the lipid layer aid in contact lens wear? A healthy tear film is comprised of 3 layers: Mucin, Aqueous, and Lipid

(Transillumination image from Dry Eye and Ocular Surface Disorders, 2004)

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Two Primary Forms of Dry Eye Oil & Water

Remember science class? Oil floats.

Oil does not mix with water, but rather sits on top of water.

800 nm Oil is what keeps 8,000 nm 100 nm water from evaporating.

The two primary forms of dry eye are Evaporative Dry Eye, also known as Meibomian Gland Dysfunction or MGD and Aqueous Dry Eye. The majority of dry eye sufferers have MGD.

The Tear Film Structure In Our Eyes The Meibomian Glands

The meibomian glands are located in the eyelids

The aqueous (water) layer The aqueous layer is When your meibomian glands provides natureal lubrication protected by the lipid (oil) do not produce sufficient oil, and is produced by the layer that is produced by the water evaporates causing lacrimal glands. meibomian glands located in burning, redness, dryness, the eyelids. irritation and eye fatigue. This is called Meibomian Gland Dysfunction or MGD.

Meibomian Glands & Blinking LipiView II: Interferometer

When we blink the meibomian glands express the Blockages in the meibomian glands result in insufficient oil Avg LLT 35 nm Avg LLT 90 nm necessary protective oils to coat the tear film

Avg LLT – Average Lipid Layer Thickness (LLT) in nanometers (nm). Number less than 90 Blinking stimulates the meibomian glands to secrete oils and spread a protective oil layer across the tear indicates increased film. When we partially blink the eyelids do not touch, so no pressure is applied at the meibomian glands to probability for MGD. release these oils. Over time the oils harden in the glands and blockages develop.

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LipiView II: Partial Blink Analysis LipiView II: Dynamic Meibomian Imaging

Meibomian gland structure is observed with Dynamic Meibomian Imaging (DMI). DMI produces three A decrease in lipid layer thickness is images (surface illumination, transillumination and merged) to capture a comprehensive view of associated with incomplete blinking. meibomian gland structure. If left untreated, the glands can shrink and deteriorate. The loss of glands is unlikely to be reversible. Increase in visual fatigue is associated with Failure to treat blocked glands is likely to lead to further structural compromise. incomplete blinking. Merged (Surface + Transillumination) Surface Illumination Transillumination Presence of partial blinks greater than 40% of total blinks is considered contributory to dry eye condition.

Normal Gland Structure If partial blinking is present, patient education and blink training should be considered.

Gland Truncation & Dilation

Severe Gland Drop Out

Intervention & Prevention Meibomian Gland Evaluator

Upper Eyelid

Meibomian Lower Eyelid Glands Over Time Temporal Nasal Central

Meibomian gland function is evaluated by assessing how glands respond to Prevention Intervention gentle force, imitating that of a deliberate blink.

Current model of treatment is interventional.

Future of MGD treatment must be preventative.

CLEAR OIL SECRETION NO OIL SECRETION (BLOCKED) OPAQUE SOLID SECRETION Glands are functioning using the No oil is expressed using the MGE Glands not functional; requires more MGE force than the MGE

Anatomy Blue Eyes

• More Like to have: – Melanoma – AMD – Photophobia – Better with pain

What function does the pupil have? http://www.msn.com/en-us/health/medical/7-things-your-eye-color-says-about-your- health/ar-BBiNSGg?li=AAa0dzB&ocid=IDMD&page=4&fullscreen=true#image=4

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• Eyebrows Eyebrows and Eyelashes The Eyelid – Thickened ridge of skin with short hairs – Diverts perspiration • 7 Layers of the eyelids • Eyelashes 1. Skin-thinnest layer – Also protects 2. Subcutaneous – Sebaceous glands at base of each lash are called Glands of Zeis connective tissue which produce a lubricating fluid 3. Striated Muscle • Fluid can harden and clog the 4. Sub-muscular connective gland, producing a stye or tissue painless chalazion. If painful and infected it is called an 5. Tarsal plate or fibrous layer external hordeolum 6. Smooth muscle 7. Conjunctiva (Bulbar/Palpebral) Cataracts (myotonia) are caused by? How are Hordoleum and Chalazions treated?

Lacrimal Apparatus Anatomy and Physiology of the Eyeball

• Sometimes a person cannot produce natural tears that they 3 Layers might need some punctal plugs. • Fibrous Layer *Cornea *Sclera

• Vascular Layer *Choroid *Ciliary body *Iris

• Nerve Layer *Retina *Macula *Optic nerve

What are the three main parts of the crystalline lens? What is the main function of each layer?

Sclera Conjunctiva

• An epithelial membrane which • White in color covers the anterior sclera and • Primary function is protection continues to the back surfaces of the lids to form a • Pierced posteriorly by the optic conjunctival sac nerve • Has blood vessels which can • Acts as insertion points for the burst and cause six EOMs subconjunctival hemorrhage • Junction between the cornea • Three parts and sclera is called the Limbus – Bulbar – Palpebral – Fornix - where bulbar and palpebral meet

What is the total power of the eye? Name the mucus producing cell?

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Cornea Cornea

What is it called when blood vessels • Composed of 5 layers grow onto the cornea? – Epithelium…24 hr healing What happens when a patient gets • Outermost layer a scar in the visual pathway? • 5 cell layers thick • Index of refraction is 1.37 • Heals very quickly • Does not scar • Approximately .5mm in thickness – Bowman's membrane- layer just under the epithelium NOTE: will • Transparent Organ (no blood vessels / avascular) scar – Stroma – middle tissue that forms 90% of the cornea • Primary function is refraction of light rays – Descemet's membrane- thin elastic layer deep in the cornea • Refractive power approx + 45.00 D – Endothelium - only one cell layer thick; lines undersurface of the cornea, where it regulates corneal water content

What is the crossover point for the nasal optic nerves? What cranial nerve is tied to corneal sensations?

Endothelial detail with nuclei Confocal Scanner Aqueous Humor

• Manufactured by ciliary body • Characteristics: – Clear – Watery consistency (99% H2O) • Functions – Refraction of light – Intraocular Pressure (IOP) Epithelial detail with nuclei – Probably nourishes posterior surface of the cornea and the crystalline lens • Flows from posterior chamber through the pupil into the anterior chamber

Which cells do not regenerate Epithelium or Endothelium? How does aqueous flow out of anterior chamber?

Crystalline Lens Crystalline Lens...approx 12-14 diopters of power • 3 things happen during accommodation: – Pupils constrict • Functions – Eyes converge – Refraction of light – Lens gets thicker – Accommodation • Focus adjustment of the • The crystalline lens contains a high degree of eye protein • Presbyopia is the loss in – Changes in the lens protein causes the lens to lose its transparency accommodation which is a condition termed "cataract" – First noticed around age 40. Due to a loss in – Aphakia is the absence of a lens. It can be removed during cataract flexibility of the lens extraction Name the three main parts of the lens? How much focusing power does the lens have?

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Iris Ciliary Body

• Most anterior portion of the • Located near the base of vascular layer the iris and posterior to it • Gives the eye its color, i.e. • Composed of blood blue eyes, brown eyes, etc. vessels and muscle fibers • Consists of blood vessels, (ciliary muscle) pigment and muscle tissue • Cilliary process produces • Regulates light aqueous • Smaller with age

What does the sphincter muscle control? Ciliary body is attached to suspensatory ligaments called?

Nerve Layer - Retina Vitreous Chamber

• Functions: • Visual Receptors are Cones and Rods – Refraction of light – Cones – Internal support • Produce color vision • Give improved acuity • Spots in vision may be • Used in day vision = “Photopic” = normal and high levels of floaters in the vitreous illumination – Rods…120 million • Produce black and white vision • Function in dim light = “Scotopic” = low level of illumination – Cones and Rods… 6 million Post vitreous detachment • Used under mesopic vision = between scotopic and photopic • Both rods and cones are used.

How many chambers are inside the eye? The _____ is the strongest refractive media and has about ____ diopters of power.

The retina (Cranial Nerve II)

Pigment epithelium Vitreous

Which cranial nerve controls the superior oblique muscle? The levator palpebrae raises the eyelid and is innervated by CN #?

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Retina – 10 layers Identification of Retinal Layers Outside of eye • Pigment epithelium NFL ILM GCL IPL OPL • Rods • Cones • Outer plexiform layer • Horizontal cells

• Bipolar cells Stratus OCT™ • Amacrine cells IS/OS RPE/CC Choroid NFL: Nerve Fiber Layer IS/OS: Junction of inner and outer IPL: Inner Plexiform Layer • Inner plexiform layer ILM: Inner Limiting Membrane photoreceptor segments OPL: Outer Plexiform GCL: Ganglion Cell Layer RPE: Retinal Pigment Epithelium • Ganglion cells CC: Choriocapillaris • Nerve fiber layer Cross-sectional image of live tissue; a virtual biopsy Vitreous (inside of eye)

Nerve Layer - Retina Nerve Layer - Retina

• Optic nerve head (optic disc) • Ora Serrata – No receptors - – Land mark attachment site physiological blind spot for choroid and retina – Point of exit of optic – nerve Most anterior portion of retina – Appears yellow compared to the orange – Nearly all rods retina

How many layers are in the retina?

What is Pars Plana?

Anatomy and Physiology New Advancement of the extraocular muscles  The Extra-ocular Muscles (EOM)  Organized into an umbrella-like • ARCUS II Retinal bundle among the orbital fat, orbital blood vessels and Prosthesis nerves  Six muscles associated with eye • Netherlands 2nd movements  Superior rectus (S.R.)  Inferior rectus (I.R.) • Patient is Jerone  Medial rectus (M.R.)  Lateral rectus (L.R.) Perk, has retinitis  Superior oblique (S.O.) pigmentosa  Inferior oblique (I.O.) • Dr. Marco Mura, MD How many cranial nerves control these 6 muscles?

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Extra Ocular Muscles Extraocular Muscles

• Medial Rectus - Most powerful, adduction, CN III • Inferior Rectus - Primary is depression, CN III • Lateral Rectus - Abduction, CN VI • Superior Rectus - Primary is elevation

What is the name of the point where the muscles come together? Which muscle close the eye lid and is innervated by cranial #7?

Bony Orbit Muscles and Function • Openings of the orbit – Purpose of openings • LR6…SO4…3 • Transmit arteries and/or veins to and from the orbit – Rectus • Transmit nerves to and from the orbit – Obliques – Types of openings • Fissures (crevices/cracks) – Intorsion • Foramina (holes) – Extorsion – Major openings – Elevation • Optic foramen - II cranial nerve - Optic Nerve – Depression • Supraorbital fissure - IV cranial nerve - Trochlear Nerve

The transition zone between the sclera and the cornea is called? An obvious upward/superior deviation of the eye is called?

Orbit Cranial Nerves LR6SO43 Muscles 1. Frontal bone…forehead • Lateral rectus muscles 2. Ethmoid bone…weakest #6 …abducens nerve 3. Palatine bone…smallest • Superior Oblique #4 4. Zygomatic bone…strongest …trochlear nerve 5. Lacrimal bone • All other muscles are 6. Maxillary bone controlled by #3 … oculomotor nerve

The conjunctiva has two divisions, they are? Name the 3 chambers of the internal eye?

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Visual Pathway Objectives Anatomy Physiology • Define the visual • The Orbit pathway - Bones, etc. • • The Sinuses Identify structures in - Locations the visual pathway • Human Body Planes • Testing used for the • External Structures - Eyelids visual pathway - Conjunctiva • Identify defects within - Eyelashes and Eyebrows the visual pathway • Lacrimal System

Anisometropia occurs when there is a ______? The outer layer of the eyeball is called?

Visual Pathway Visual Pathway

• Visual pathway has seven structures • Physical – Retina – Optic Nerve – Optic Chiasm • Physiological – Optic Tract – Lateral Geniculate Body (LGB) • Psychological – Optic Radiations – Visual Cortex …where vision occurs What causes your physiological blind spot?

Aniseikonia occurs when an object viewed by one eye is ______?

Visual Pathway Retina

• Divided into four quadrants like the brain • Fovea at exact center • Optic nerve head is located in nasal half • Each quadrant sees the exact opposite visual field

Antimetropia occurs when ______? What is an exudate?

What is papilledema?

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Optic Chiasm

• Temporal fibers do not cross • Nasal fibers do cross • Some fibers from the macula cross while others do not What part of the brain does the vision occur?

Growth beneath Pituitary Gland Visual Field Defects • Common types of field Homonymous heminopia defects – Blind spots - Areas of blindness in the visual field – Hemianopsia - Blindness in one half of the visual field of one or both eyes Incongruous homonymous • Homonymous - Involving the nasal half of the visual field of one eye and the temporal half of the visual field of the other eye • Incongruous - Binasal defect An area of blindness within a visual field is called?

10 2/16/2016

Is this possible? You be the judge Review Questions

• The point where the upper and lower eyelids meet is called a. ora serrata b. canthus c. joint d. sphinx

• The blockage of the meibomian gland is called the ______when it causes pain, and the ______when it does not cause pain.

Review Questions Review Questions

• The eyelid will protect your eyes from… • The drain port for tears is called? a. blinking a. canal of Schlemm b. dust particles b. punctum c. stray tears c. lacrimal gland d. a burning punctum d. zonnule of Zinn

• What main muscles raises the eyelid? • In what layer of the eye will chronic diseases normally manifest?

• What structure prevents a contact from going behind the globe of the eye? • Name the five layers of the cornea in order

Review Questions Review Questions

• What are the layers of a tear film?

• What is the most anterior part of the retina. • Where is tear mucin produced?

• Why is the tear film important in contact lens wear? • What is the total power of the Cornea, the crystalline lens assembly, and the overall eye? • The optic nerve is which cranial nerve?

• What is the most posterior layer of the retina? • What function does the Canal of Schlemm have?

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Review Review Questions

• Opia means what? • Identify the name for the 3 parts of the conjunctiva

• What is the difference between a tropia and a phoria? • In what layer of the eye will the retina be found?

• Avascular means what? • What is the strongest bone of the bony orbit? • How many extra-ocular muscles are oblique?

• What muscle of the lid would be involved in ptosis? • What does the root word “papill” mean?

Review Questions Review Questions

• ______exist when the foveal lines of sight of the two eyes • When the power of the crystalline lens correspond with axial do not point at the same object. length of the eye, so that parallel light rays are appropriately – A. binocularity refracted to focus on the retina is called? – B. strabismus – A. emmetropia – C. conjunctivitis – B. ammetropia – D. FB sensation – C. hyperopia – D. myopia • Of the following all are anomalies of the binocular system except: • An opacity of the crystalline lens is known as? – A. strabismus – A. photophobia – B. Amblyopia – B. cataract – C. anomalous correspondence – C. edema – D. conjunctivitis – D. aphakia

Review Questions Review Questions

• Which test checks for eye movement and helps detect the • Which test uses Pseudo Isochromatic Plates? dominate eye? – A. IOP – A. muscle H – B. color test – B. cover test – C. visual acuity – C. cover/uncover – D. myopia – D. snellen

• Glaucoma screening test that used puff of air onto the eye surface: • This checks the power of the eye: – A. NCT – A. NCT – B. snellen – C. amsler grid – B. taking case history – D. accommodation – C. Autorefractor – D. taking blood pressure

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Review Questions Review Questions • Which test is used to check six cardinal position of gaze for motility? • What is a good tear BUT? – A. Muscle H – B. APD – C. Amsler Grid • What device checks the brain-eye connection? – D. Tropia

• Examination of the eye is performed by using a slit lamp or another name for slit lamp is: • What device measures the distance between – A. non-contact tonometer – B. biomicroscope the pupils? – C. pupilometer – D. lensometer • What device measures corneal thickness?

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