Ophthalmic System Flashcards by N N

The eyes sit in the bony depression of the skull called the _____

orbits

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The function of orbit:

Protect the eyes, stabilize and anchor the eyes muscles

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3 examples of eyes accessory structure :

Conjunctiva, lacrimal (gland/duct), eye muscles

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_______:
A thin, protective mucus membrane
Passes from the eyelids to the surface of the eye ball, where it covers the sclera

Conjunctiva

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________:
Lines the inner aspect of the eyelids; protective mucus membrane

Palpebral conjunctiva

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______:
A group of structures that produce and drain tears

Lacrimal

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Lacrimal glands secrete ____; are supply
by the ____ nerve

lacrimal fluid, facial (CN VII)

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Eye muscles are capable of moving the eye in ____ direction

almost all

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Functions of Lacrimal fluid (tears):

Protect, clean, lubricate and moisten the eyeball

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Lacrimal fluid (tears) is __________.

a watery solution contains salts, mucus,
and lysozyme (a bactericidal enzyme)

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____: empty tears onto the surface of the conjunctiva of the upper lid

Lacrimal ducts

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Functions of eyelids:

Shade the eyes during sleep.
Protect eyes from excessive light and foreign objects.
Spread lubricating secretions over the
eyeballs.

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Functions of eyelashes & eyebrow:

Protect eyeballs from foreign objects,
perspirations, and direct sunlight

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Internal structure of eye:
Outer (____) Avascular Layer includes:
_______

Fibrous,
sclera, cornea

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Functions of sclera:

Gives shape to the eyeball and makes it more rigid.
Protects the inner parts of the eyeball.
Serves as a site of attachment for the extrinsic eye muscles.

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______:
White, protective fibrous tissue
Surrounding the posterior 4/5 except the cornea
A layer of dense connective tissue made up mostly collagen and elastic fiber

Sclera

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______:
Transparent and highly sensitive in the front
Mainly collagen fibre
Curved shape helps focus light to retina
Central part of the cornea receives oxygen from outside air

Cornea

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Internal structure of eye:
Middle (_____) Avascular Layer includes:
_________

Vascular,
choroid, iris, ciliary body

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______:
Rich, vascular coat to nourish the retina
Cover posterior 4/5 of the eye
Contains numerous blood vessels provide nutrients to the posterior surface of the retina
Contains melanocytes to produce melanin
Melanin prevents reflection and scattering of light within the eyeball and make image cast on retina more sharp and clear

Choroid

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______:
The coloured portion of the eyeball
Consists of melanocytes
Regulating the amounts of light to enter the eye
Autonomic reflexes regulate pupil diameter in response to light levels:

Bright light → parasympathetic fibres of the oculomotor (III) nerve stimulate the circular muscles of the iris to contract →
decrease pupil size (constriction)
Dim light → sympathetic neuron stimulate the radial muscles of the iris to contract → increase pupil size (dilation)

Iris

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Regulation of light enter into eyes by iris and _______ muscles.

dilator pupillae & sphincter pupillae

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______:
Contains melanin-producing melanocytes → dark brown in colour; contract and relax to control the shape of lens, adapting it from far or near vision

Ciliary body

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______:
Secrete _____ and help maintain
intra-ocular pressure; nourishes the lens and the cornea; drain into through the trabecular meshwork and the canal of Schlemm in the angle of the anterior chamber

Ciliary processes, aqueous humor

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Normally aqueous humor is completely replaced about
every __ minutes

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Function of aqueous humor:

nourishes the lens and cornea

Aqueous Humor: From the ____ chamber to the ____ chamber through the pupil Drain through the trabecular meshwork and the canal of Schlemm in the angle of the anterior chamber (_______)

posterior, anterior, Scleral venous sinus

Lens: Bi-convex, transparent, avascular structure with no nerve or blood supply ___% protein & ___% water Locate behind the ___, in front of the _____, supported by the suspensory ligaments, attached to the ciliary body To focus light rays on the retina for accommodation

35, 65, Iris, vitreous humour

When lens loses its transparency, it will develop _____.

cataract

Inner layer of eyes is called ____; complex nervous tissue layer: Pigmented layer: A sheet of melanin-containing epithelial cells located between the choroid and the neural part of the retina) Neural (sensory) layer: Processes visual data extensively before sending nerve impulses into axons that form the optic nerve 3 layers of retinal neurons: ______ cell layer, ______ cell layer, _____ layer Contains rods and cones cells (photoreceptors) Blood supply – central retinal artery & vein

retina ganglion, bipolar, photoreceptor

Retina has two layers:

Pigmented layer, neural (sensory) layer

Retina contains: blood supply - central retinal artery & vein Blind spot (the optic disc) - no rods and cones → we cannot see images that strike the blind spot _______ - the center of the posterior portion of the retina; an area full of cones _____ - at the center of the macula; contains only cones; the area of highest visual acuity

Macula lutea, Fovea

________: Gelatinous substance fills the posterior segment between the lens and the retina; consists of mostly water, collagen fibres and hyaluronic acid

Vitreous Humor

Functions of vitreous humor:

Give shape to the eyeball, contain phagocytic cells that remove debris

The vitreous humor undergo constant replacement (T/F)

Floaters is caused by __________.

Degeneration and breakage of the vitreous humor / presence of cellular debris

Pressure in the eye & glaucoma is called ______.

Intraocular pressure

Intraocular pressure is mainly produced by ____ and partly by the _____

aqueous humor, vitreous humor

Normal intraocular pressure:

12-21mmHg

Functions of intraocular pressure:

Maintains the shape of the eyeball and prevents it from collapsing

______: Increase in aqueous humor production or blockage of its drainage Increase intraocular pressure, press the retinal ganglion cells, cause the irreversible loss of the cells, excavation and degeneration of the optic nerve head

Glaucoma

Consequence of serious glaucoma:

Tunnel vision, blind

_______ is bending of light by the lens and cornea. Light rays enter the eye → refracted at the surfaces of the cornea and the lens → focus on the retina

Refraction

Images focused on the retina are _____, and undergo right-to-left reversal

inverted

A normal eye can sufficiently refract light rays from an object __m (20 ft) away so that a clear image is focused on the retina

_____ (nearsightedness) The eyeball is too deep, or the resting curvature of the lens is too great, caused the image projected in front of the retina. The person will see distant objects as blurry and out of focus.

Myopia

_____ (farsightedness) The eyeball is too shallow or the lens is too flat.

Hyperopia (presbyopia) (presbys, old man)

Refractive problems examples:

Presbyopia, astigmatism

Astigmatism:

Either the cornea or lens has an irregular curvature. Part of the image is distorted or blurred.

______: Either the cornea or lens has an irregular curvature. Part of the image is distorted or blurred

Astigmatism

Presbyopia:

Age-related loss of reading vision Loss the ability to accommodate near objects Flexibility of the natural lens diminishes with age + the loss of power of ciliary muscle (Old people's lenses lose elasticity)

______: Age-related loss of reading vision Loss the ability to accommodate near objects Flexibility of the natural lens diminishes with age + the loss of power of ciliary muscle (Old people's lenses lose elasticity)

Presbyopia

________: the increase in the curvature of the lens for near vision

Accommodation

Near point vision is the minimum distance from the eye that an object can be clearly focused with maximum accommodation. ~ __cm (4 in.) in a young adult

Viewing distant objects ______ muscle ____→ lens flattened

ciliary, relaxes

Viewing close objects _______ muscles _____→ lens become more convex

ciliary, contracts

Parasympathetic fibres of the ______ (CN ___) nerve innervate the ciliary muscle of the ciliary body, and therefore mediate the process of accommodation

oculomotor, III

Narrowing the diameter of the pupil, due to the contraction of the __________

circular muscle of the iris

Testing pupillary response to light: Light shined in one eye normally results in the constriction of ____ pupils

both

Pupillary Reflexes Direct Response:

Pupil constricts when the light is shone on to it

Pupillary Reflexes Consensual response:

The other pupil also constricts

CN III lesion: loss of _____

consensual pupillary light reflex

CN II lesion: loss of _____

direct pupillary light reflex

Test for visual acuity by:

Snellen chart / E chart or Rosenbaum pocket vision chart

Snellen chart / E chart: * Well-lit area * Distance __ft or __m * Cover one eye * Read out the letters from the biggest to the smallest __/__ or __/__ Standard vision Seeing __ft away as if it was __ft away

20, 6 20,20 6,6 20,20

_________: - To identify visual field defects - Measures peripheral vision compared to the examiner - Advance finder, starting from periphery, and ask patient to indicate when the finger is first visible

Visual field test

Test colour blindness by: Mostly difficult to differentiate _____ colour

Ishihara Colour Blindness Test, red and green colour

Functions of rod cells → Rhodopsin:

Allow us to see dim light (black, white, shade of greys)

Functions of cone cells → Cone photopigments:

Produce colour vision, 3 types of cones: red, blue, green

Photoreceptors contains 2 parts:

Opsin (a glycoprotein) Retinal (a derivative of vitamin A)

Function of opsin part of photoreceptors (a glycoprotein):

Absorb different colours (wavelength) of incoming light

Retinal part of photoreceptors (a derivative of vitamin A) Form from carotene, the plant pigment that gives carrots orange colour Good vision depends on adequate diet ary intake of carotene rich vegetables such as carrots, spinach, broccoli, etc. Function:

The light absorbing part

Bleaching of visual pigments: after absorbing a photon, the ______ molecule begins to break down into _____ and ____.

rhodopsin, retinal, opsin (trans-retinal completely separates from opsin)

In darkness, retinal is in bent shape → ___-retinal When cis-retinal absorbs a photon of light, it straightens out → ___-retinal The cis to trans conversion is called ______

cis, trans, isomerization

An enzyme called ____ coverts trans-retinal back to cis-retinal

retinal isomerase

The ___-retinal then bind to opsin, reforming a functional photopigment. This part of the cycle (i.e. the re-synthesis of photopigment) is called _____

cis, regeneration

Ophthalmic System Flashcards

(75 cards)