Ophthalmic System Flashcards
The eyes sit in the bony depression of the skull called the _____
orbits
The function of orbit:
Protect the eyes, stabilize and anchor the eyes muscles
3 examples of eyes accessory structure :
Conjunctiva, lacrimal (gland/duct), eye muscles
_______:
A thin, protective mucus membrane
Passes from the eyelids to the surface of the eye ball, where it covers the sclera
Conjunctiva
________:
Lines the inner aspect of the eyelids; protective mucus membrane
Palpebral conjunctiva
______:
A group of structures that produce and drain tears
Lacrimal
Lacrimal glands secrete ____; are supply
by the ____ nerve
lacrimal fluid, facial (CN VII)
Eye muscles are capable of moving the eye in ____ direction
almost all
Functions of Lacrimal fluid (tears):
Protect, clean, lubricate and moisten the eyeball
Lacrimal fluid (tears) is __________.
a watery solution contains salts, mucus,
and lysozyme (a bactericidal enzyme)
____: empty tears onto the surface of the conjunctiva of the upper lid
Lacrimal ducts
Functions of eyelids:
Shade the eyes during sleep.
Protect eyes from excessive light and foreign objects.
Spread lubricating secretions over the
eyeballs.
Functions of eyelashes & eyebrow:
Protect eyeballs from foreign objects,
perspirations, and direct sunlight
Internal structure of eye:
Outer (____) Avascular Layer includes:
_______
Fibrous,
sclera, cornea
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.
______:
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
______:
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
Internal structure of eye:
Middle (_____) Avascular Layer includes:
_________
Vascular,
choroid, iris, ciliary body
______:
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
______:
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
Regulation of light enter into eyes by iris and _______ muscles.
dilator pupillae & sphincter pupillae
______:
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
______:
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
Normally aqueous humor is completely replaced about
every __ minutes
90
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)
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
6
_____ (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
10
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
