Vision Lab Flashcards by Lauren Yeiser

Cornea
- Function: Refracts light to focus it on the retina.
- Location: Anterior surface of the eye; continuous with the sclera.
- Tunic: Part of the outer fibrous tunic.
- Description: Outermost transparent, avascular, dome-shaped structure covering the iris and pupil.

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Sclera
- Function: Maintains the shape of the eyeball and provides protection and attachment for extraocular muscles.
- Location: Outer posterior 5/6 of the eyeball; continuous with the cornea anteriorly and dura mater posteriorly.
- Tunic: Part of the outer fibrous tunic.
- Description: Opaque, dense connective tissue; the “white” of the eye; avascular and tough.

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Iris
- Function: Controls pupil size to regulate the amount of light entering the eye.
- Location: Anterior part of the vascular tunic, between the cornea and the lens; forms the visible colored part of the eye.
- Tunic: Part of the middle vascular tunic (uvea).
- Description: Pigmented, contractile diaphragm with a central opening (the pupil); contains two muscle layers:
- Sphincter pupillae (circular muscle) — constricts pupil (parasympathetic)
- Dilator pupillae (radial muscle) — dilates pupil (sympathetic)

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Ciliary Body
- Function: Produces aqueous humor; controls lens shape for focusing (accommodation).
- Location: Part of the vascular tunic; continuous with the choroid and connected to the iris. Composed of ciliary muscle and ciliary processes
- Tunic: Part of the middle vascular tunic (uvea).
- Description: Ring of tissue composed of ciliary muscle (smooth muscle) and ciliary processes; anchors the suspensory ligaments (zonular fibers) that hold the lens.

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flesh colored

Ciliary Processes
- Function: Secrete aqueous humor into the posterior chamber; help anchor suspensory ligaments, part of ciliary body.
- Location: Arise from the inner surface of the ciliary body.
- Tunic: Part of the middle vascular tunic (uvea).
- Description: Folded, vascular extensions of the ciliary body; highly vascular and covered by a double layer of epithelium.

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white colored

Suspensory Ligaments
- Function: Anchor the lens to the ciliary processes and transmit tension from the ciliary muscle to adjust lens shape (accommodation).
- Location: Extend between the ciliary processes and the lens capsule.
- Description: Fine, transparent fibers that suspend the lens in place; relax when the ciliary muscle contracts (allowing the lens to thicken for near vision).

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Pupil
- Function: Regulates the amount of light entering the eye by changing diameter.
- Location: Central opening of the iris.
- Description: Circular aperture whose size is controlled by two iris muscles:
- Sphincter pupillae (circular muscle) — constricts pupil (parasympathetic)
- Dilator pupillae (radial muscle) — dilates pupil (sympathetic)

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Lens
- Function: Focuses light onto the retina by changing shape (accommodation).
- Location: Posterior to the iris and pupil; suspended by suspensory ligaments from the ciliary processes.
- Description: Transparent, biconvex, avascular structure enclosed in a flexible capsule; thickens for near vision when ciliary muscle contracts, and flattens for distance vision when relaxed.

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Ora Serrata

Function: Marks the anterior boundary of the photosensitive retina; transition point to the non-visual retina.
Location: Anterior edge of the neural tunic, just posterior to the ciliary body.
Tunic: Part of the neural tunic
Description: Jagged (serrated) margin where the multilayered neural retina ends and the simple, non-photosensitive pigmented layer continues over the ciliary body.

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Macula Lutea
- Function: Provides sharp, detailed central vision; contains the highest concentration of cone photoreceptors.
- Location: Central region of the retina, lateral to the optic disc.
- Tunic: Part of the neural tunic (retina).
- Description: Yellowish, oval area of the retina specialized for visual acuity; its central depression, fovea centralis, is the point of greatest visual resolution.

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Fovea Centralis
- Function: Provides the sharpest visual acuity and best color discrimination.
- Location: Center of the macula lutea in the retina.
- Tunic: Part of the neural tunic (retina).
- Description: Small central pit containing only cone photoreceptors; area where light falls directly on photoreceptors without distortion from other retinal layers.

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yellow

Optic Disc
- Function: Point where axons of retinal ganglion cells exit the eye to form the optic nerve; no image detection (blind spot).
- Location: Medial to the macula lutea on the retina.
- Tunic: Part of the neural tunic
- Description: Circular area where the optic nerve, central retinal artery, and vein enter or leave the eye; lacks photoreceptors, resulting in a physiological blind spot.

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blue

Central Retinal Vein
- Function: Drains deoxygenated blood from the retina.
- Location: Emerges from the retina at the optic disc and runs alongside the central retinal artery.
- Description: Collects blood from retinal capillaries and exits the eye through the optic nerve; ultimately drains into the superior ophthalmic vein or directly into the cavernous sinus.

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red

Central Retinal Artery
- Function: Supplies oxygenated blood to the inner layers of the retina.
- Location: Enters the eye through the optic nerve and emerges at the optic disc.
- Description: Branch of the ophthalmic artery; radiates across the inner surface of the retina to nourish ganglion cells and inner retinal layers.

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Optic Nerve (Cranial Nerve II)
- Function: Transmits visual information from the retina to the brain.
- Location: Extends from the optic disc at the posterior retina to the optic chiasm.
- Description: Composed of axons from retinal ganglion cells; passes through the optic canal of the sphenoid bone and carries sensory (afferent) signals for vision to the brain.

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Lacrimal Glands
- Function: Produce the aqueous layer of the tear film to lubricate, nourish, and protect the eye surface.
- Location: Superolateral part of the orbit, within the lacrimal fossa of the frontal bone.
- Description: Serous, tubuloacinar glands that secrete tears into the superior conjunctival fornix via multiple excretory ducts; stimulated by parasympathetic fibers from the facial nerve (CN VII).

label 1,2 & 3

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Optic Chiasm

The optic chiasm is the X-shaped structure where optic nerve fibers from the nasal (medial) retina of each eye cross to the opposite side.

Located just above the pituitary gland and below the hypothalamus.

This crossing allows visual information from the right and left visual fields to be processed in the opposite cerebral hemisphere.

Only the axons from the nasal (medial) half of each retina cross to the opposite side.

Axons from the temporal (lateral) half of each retina do not cross — they stay on the same side (ipsilateral).

partial crossing allows visual information from the right visual field of both eyes to be processed in the left hemisphere, and left visual field info to go to the right hemisphere.

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Lacrimal Ducts (Excretory Ducts of Lacrimal Gland)
- Function: Transport tears from the lacrimal gland to the surface of the eye.
- Location: Extend from the lacrimal gland to open into the superior conjunctival fornix.
- Description: 6–12 small ducts that carry lacrimal fluid to the upper outer part of the conjunctival sac, where tears spread across the eye surface during blinking.

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Lacrimal Canaliculus (plural: Canaliculi)
- Function: Drain tears from the eye surface into the lacrimal sac.
- Location: Begin at the lacrimal puncta on the medial margin of each eyelid and run medially toward the lacrimal sac.
- Description: Small channels (superior and inferior) that transport tears after they pass through the lacrimal puncta; typically join to form a common canaliculus before entering the lacrimal sac.

Lacrimal Sac
- Function: Collects tears from the lacrimal canaliculi and drains them into the nasolacrimal duct.
- Location: In the lacrimal fossa, between the lacrimal bone and maxilla, just lateral to the nasal bridge.
- Description: Upper dilated end of the nasolacrimal drainage system; lined with epithelium and continuous inferiorly with the nasolacrimal duct.

Nasolacrimal Duct
- Function: Drains tears from the lacrimal sac into the inferior nasal meatus.
- Location: Extends from the inferior end of the lacrimal sac, running through the nasolacrimal canal in the maxilla.
- Description: Final part of the tear drainage system; lined with mucosa and opens into the lateral wall of the nasal cavity beneath the inferior nasal concha.

Palpebrae (Eyelids)
- Function: Protect the eyes from debris, bright light, and drying; help spread the tear film across the eye surface.
- Location: Cover the anterior surface of the eye; consist of upper (superior) and lower (inferior) eyelids.
- Description: Movable skin folds containing connective tissue (tarsal plates), skeletal muscle (orbicularis oculi), and glands (e.g., tarsal glands); lined internally by conjunctiva.

model lists 11, 12 as tarsal plate but tarsal plate is internal to 11 and 12

Medial Canthus & Lateral Canthus
- Function: Serve as the junction points where the upper and lower eyelids meet; help guide tear drainage at the medial angle.
- Location:
- Medial Canthus: Inner corner of the eye, near the nose.
- Lateral Canthus: Outer corner of the eye, near the temple.
- Description:
- Medial Canthus: Contains structures involved in tear drainage, including the lacrimal caruncle and puncta.
- Lateral Canthus: Simple eyelid junction without tear drainage structures.

*red, fleshy part *

**Lacrimal Caruncle** - *Function:* Contains sebaceous and sweat glands that contribute to the tear film and may trap debris. Plays a role in the drainage of tears and can sometimes become inflamed or swollen - *Location:* Medial canthus of the eye, on the inner corner between the upper and lower eyelids. - *Description:* Small, pink, fleshy mound of modified skin; non-keratinized and glandular *#7 is the lacrimal papillae, located near medial canthus*

*16*

**Palpebral Conjunctiva** - *Function:* Protects the eye and inner eyelid surface; helps produce mucus for tear film stability. - *Location:* Lines the inner surface of the upper and lower eyelids. - *Description:* Thin, transparent mucous membrane continuous with the bulbar conjunctiva; reflects at the fornices to cover the anterior surface of the sclera.

*17*

**Bulbar Conjunctiva (Ocular Conjunctiva)** - *Function:* Protects the exposed anterior surface of the sclera and contributes to tear film stability. - *Location:* Covers the anterior part of the sclera up to the corneal margin; continuous with the palpebral conjunctiva at the fornices. - *Description:* Thin, transparent mucous membrane that allows the white of the eye to remain visible while providing lubrication and immune protection.

**Tarsal Glands (Meibomian Glands)** - *Function:* Secrete an oily substance that prevents evaporation of the tear film and keeps eyelids from sticking together. - *Location:* Embedded within the tarsal plates of the upper and lower eyelids; ducts open along the eyelid margin. - *Description:* Long, modified sebaceous glands not associated with hair follicles; essential for tear film stability and eye surface protection. *in image labeled as meibomian glands*

*space*

**Anterior Chamber (of the Anterior Cavity)** - *Function:* Holds **aqueous humor** that nourishes the cornea and lens and helps maintain intraocular pressure. - *Location:* Space between the cornea and the iris. - *Description:* Filled with aqueous humor flowing from the posterior chamber through the pupil; drains into the scleral venous sinus (canal of Schlemm).

*space*

**Posterior Chamber (of the Anterior Cavity)** - *Function:* Produces and holds **aqueous humor** before it flows into the anterior chamber. - *Location:* Narrow space between the posterior surface of the iris and the anterior surface of the lens and ciliary processes. - *Description:* Aqueous humor is secreted here by the ciliary processes and passes through the pupil to reach the anterior chamber.

**Scleral Venous Sinus (Canal of Schlemm)** - *Function:* Drains aqueous humor from the anterior chamber into the venous circulation, helping maintain intraocular pressure. - *Location:* At the limbus — the junction between the cornea and sclera, just deep to the trabecular meshwork. - *Description:* Circular endothelial-lined channel that encircles the eye; receives aqueous humor filtered through the trabecular meshwork and passes it into episcleral veins.

**Posterior Cavity (Vitreous Chamber)** - *Function:* Maintains the shape of the eyeball and holds the retina in place by exerting internal pressure. - *Location:* Space between the lens and the retina. - *Description:* Filled with vitreous humor — a clear, gel-like substance that is not continuously replaced; supports the retina against the pigmented choroid, which provides most of the retina’s blood supply. The inner retina also receives blood from the central retinal artery.

*outer layer*

**Choroid** - *Function:* Provides oxygen and nutrients to the outer layers of the retina; absorbs stray light to reduce internal reflection. - *Location:* Between the retina and the sclera, forming most of the posterior portion of the vascular tunic. - *Tunic:* Part of the **middle vascular tunic** (uvea). - *Description:* Highly vascular and pigmented layer composed of connective tissue, capillaries, and melanocytes; dark brown in color due to melanin, which prevents light scatter within the eye.

**Superior Rectus Muscle** - *Location:* Runs from the common tendinous ring at the back of the orbit to the superior surface of the eyeball. - *Eye Movement:* Elevates the eye (moves it upward) - *Innervation:* Oculomotor nerve (Cranial Nerve III)

**Superior Oblique Muscle** - *Eye Movement:* Internal rotation, slight depression - *Innervation:* Trochlear nerve (Cranial Nerve IV)

**Lateral Rectus** - *Eye Movement*: Rolls eye laterally - *Innervation*: Abducens (VI)

**Inferior Oblique** - *Eye Movement*: External rotation, slight elevation - *Innervation*: Oculomotor (III)

*f*

**Inferior Rectus** - *Eye Movement*: Rolls eye down Oculomotor (III)

**Inferior Rectus** - *Eye Movement*: Rolls eye medially Oculomotor (III)

Layers of retina

**Layers of the Retina** - *Function:* Convert light into neural signals and transmit them to the brain. - *Order (from outermost to innermost):* 1. **Pigmented Epithelium** – Absorbs stray light and supports photoreceptors. 2. **Photoreceptor Layer** – Contains rods and cones that detect light and color. 3. **Bipolar Cell Layer** – Intermediate neurons that transmit signals from photoreceptors to ganglion cells. 4. **Ganglion Cell Layer** – Contains output neurons whose axons form the optic nerve.

**Refraction**

- *Definition:* The bending of light as it passes through a medium of one density into another, such as from air into the cornea or lens, allowing light to be focused on the retina.

**Focal Point**

- *Definition:* The specific point at which light rays converge after passing through a refractive surface, ideally falling on the retina for clear vision.

**Focal Distance**

Focal distance is the distance between the lens of the eye and the retina when the eye is focusing on an object. More specifically: It is the distance required for light rays from an object being focused to converge precisely on the retina after passing through the lens. For a clear image, the lens must bend (refract) light so that the focal point lands on the retina, especially the fovea centralis in the macula. The focal distance changes depending on how far away the object is — the lens changes shape (via accommodation) to keep the image sharp on the retina. Summary: Focal distance = distance from the lens to the retina when focusing light from a specific object to form a clear image.

**Accommodation**

- *Definition:* The process by which the ciliary muscle adjusts the lens shape to focus on near or distant objects by altering its curvature.

**Emmetropia**

- *Definition:* The normal condition of the eye in which light is properly focused on the retina without the need for corrective lenses. typically looking at object 20 feet (6 meters) away

**Myopia**

- *Definition:* Also called nearsightedness; a condition where the focal point falls in front of the retina, making distant objects appear blurry.

**Hyperopia**

- *Definition:* Also called farsightedness; a condition where the focal point falls behind the retina, making near objects appear blurry.

**Presbyopia**

- *Definition:* Age-related loss of the eye’s ability to accommodate due to decreased elasticity of the lens, resulting in difficulty focusing on close objects