Introduction to Ophthalmology Flashcards
3 layers of the eye
- outermost - fibrous
- sclera
- cornea - middle - vascular
- iris
- pupil
- ciliary body
- choroid - inner - neural
- retina - outer pigmented layer, inner neural layer -photoreceptors too)
- optic nerve
what are the anterior and posterior sections of the eye?
anterior - filled with aqueous humor
- posterior chamber
- anterior chamber
- cornea
- iris
- lens
posterior - filled with vitreous humor
- vitreous chamber
the pigmented part of the retina located in the very center.
macula
the area of best visual acuity
contains a large amount of cones—nerve cells that are photoreceptors with high acuity.
fovea
how does sight work?
- light reflects off an object enters the eye
- As it enters the eye, it is unfocused - Cornea
- Iris
- In the center of the iris is the pupil
- The pupil is where light enters the eye - Behind the pupil is the lens
- The lens focuses the light entering the eye
- The lens will bend/flatten/change shape to focus light rays - That light then falls onto the retina at the back of your eye
- The retina is a complex layer of cells that react to light - The optic nerve carries those signals to your brain where they are decoded into an image
This is where light focuses precisely on the retina
focal point
For good vision, the focal point must be on the ?
retina
The process of bending light to produce a focused image on the retina
refraction
how do most vision problems occur
an error in how our eyes refract light
Refraction errors are a type of vision problem that makes it hard to see clearly
errors of refraction
Myopia
Hyperopia
Astigmatism
Presbyopia
Keratoconus
Too much curvature of the cornea
Eyeball too long for the refractive power of the cornea and lens
leading to Trouble seeing distant objects
MC refraction problem
myopia - nearsightedness
tx for myopia
Correct with concave lens
- Wide view lens
- Diverges light rays
- Makes objects look smaller than they are
Too little curvature of the cornea
Eyeball too short for the refractive power of the cornea and lens
Nearby objects look blurry
hyperopia - farsightedness
tx for hyperopia
Correct with convex lens
The rays meet at a single point on other side of lens
Magnify objects to make them look larger
differences between concave and convex lens
- Concave
- Spreads out light rays
divergent
- Focal point in front of lens
- Parallel rays of light pass through the lens are spread out
- Image formed is smaller but clear
- Gives wider viewing angle - Convex
- Focuses the light rays to a specific point - Convergent
- Rays of light passing through it get bent in a inward direction towards a single point
- Brings light rays together to a focal point behind the lens
- Convex lenses hold magnifying abilities
Irregular shape of the cornea or lens
Light reflected to multiple areas of retina = multiple focal points
Retinal image is blurred
Astigmatism
tx for Astigmatism
Corrected with cylindrical lenses that equalize the refraction of light
Age related farsightedness
Loss of Mobility and focusing power of lens
Worse in dim light
Presbyopia
when does Presbyopia start to show? when do they stablize?
Begin to notice inability to read small print around age 44-46 years
Symptoms increase until about age 55 years then stabilize
tx for Presbyopia
reading glasses
Cornea becomes thin and cone-like
Causes sensitivity to light and glare
Causes blurred vision
Keratoconus
tx for keratoconus
Corrective lenses, contact lenses, cornea transplant
what are the photoreceptors of the retina
- Rods
- Specialized for dim light (night vision) - Cones
- Specialized for color perception
- Red, green and blue cones
- Color blindness results from deficit of one type of cone
what fills the anterior cavity between cornea and lens
Supplies nutrients to cornea and lens
aqueous humor
what fluid is Continually formed and reabsorbed
Maintains intraocular pressure
aqueous humor
what parts of the eye do not have blood vessels
Cornea and lens
fluid is in posterior cavity between lens and retina
Jelly Like substance
Maintains shape of eyeball
Holds retina in place
Vitreous humor
A group of eye diseases characterized by neuropathy to the optic nerve
Cupping of the optic disk on ophthalmologic examination
Glaucoma
what are the 2 leading causes of blindness
- cataracts
- glaucoma
what are the two pupillary reactions
Parasympathetic constriction
Sympathetic dilatation
pupillary reaction is controlled by what?
the sphincter and dilator pupillae muscles: circular group of muscles surrounding iris
3 notes to be aware of when doing direct and consensual pupillary reaction
Magnitude
Speed
Symmetry
Asymmetric size of the pupils
Has no, or sluggish pupillary reaction to light
Anisocoria
If an optic nerve lesion is present, the affected pupil will not constrict to light when light shone in that pupil. It will constrict, however, when light shone into other eye (consensual)
this is called ?
Relative Afferent Pupillary Defect - Marcus Gunn Pupil
(RAPD)
Anisocoria is MC caused by what?
pathologic - 80%
- Injury or lesion (tumor, etc.)
May be a normal variant (20%)
- Horner’s syndrome
- Adie’s syndrome
triad of horner’s syndrome
Ptosis
Miosis
Anhidrosis
from Loss of sympathetic innervation
horner’s syndrome is caused by?
Caused by a lesion along the sympathetic pathway
a pupil in one eye that is larger than the other and constricts slowly in bright light
adie’s pupil (tonic pupil)
as well as the absence of deep tendon reflexes (usually Achilles tendon) = Holmes-Adie’s
adie’s pupil is MC in who?
women in 3rd/4th decade of life
Hallmark of tertiary neurosyphilis
argyll-robertson pupil
Pupils restrict to accommodation, but not light
Usually bilateral
Argyll-Robertson Pupil
Loss of transparency in the lens
Blurred vision - Both near and distance
Painless
Absence of red reflex
cataracts
Small, yellow-white, slightly elevated lesions, which look like clouds on retinal surface
Cotton Wool Spots (AKA soft exudates)
M/C cause diabetic retinopathy and hypertensive retinopathy
Cotton Wool Spots (AKA soft exudates)
a thin layer of tissue at the back of the eye pulls away from the layer of blood vessels that provides it with oxygen and nutrients
Retinal Detachment
swelling of both optic discs in your eyes due to increased intracranial pressure
papilledema
Cherry Red Spot on fovea
Boxcar Segmentation
Retinal artery Occlusion
Widespread retinal hemorrhages
Venous dilation and tortuosity
“Blood and Thunder Fundus”
Retinal Vein Occlusion
A small artery is seen crossing a small vein
This causes compression on the small vein
A-V Nicking
Indentation (nicking) of retinal veins by stiff (arteriosclerotic retinal arteries)
AV nicking can see in what other eye problem?
hypertensive retinopathy
this is often seen in what other eye problem?
(Copper and Silver Wiring)
HTN retinopathy
Both due to atherosclerotic vessel wall thickening and chronic Hypertension
differences between copper and silver wiring
Copper:
Moderate vascular wall changes
Appear orange or yellow instead of red
Silver:
Severe vascular wall hyperplasia and thickening
Appear white
how does cupping develop?
- Optic disc carries optic nerve which exits to the brain
- Optic disc has a center called the cup which is small in comparison to the rest of the disc
- When optic nerve is damaged (glaucoma) these nerve fibers die off and blood flow is diminished
- This causes cup to become larger since the support structure is not there
Hard exudates
Diabetic Retinopathy
Smallish, yellowish-whitish distinct spots with sharp borders
Flame Hemorrhage and Hard Exudates
Flame Hemorrhage and Hard Exudates is caused by?
breakdown of blood-retina border, allowing leakage from retinal vessels
This vascular permeability allows the leakage of fluid and lipoprotein into the retina
Seen all over retina
Diabetic/hypertensive retinopathy
When necrotic vessels bleed into the nerve fiber layer
More superficial layers of the retina
larger
Flame Hemorrhages
Occur as microaneurysms rupture in the deeper layers of the retina
Blood accumulates in the inner nuclear layer
Dot-Blot Hemorrhages
Seen in diabetic retinopathy and macular degeneration
Microvascular damage and ischemia cause release of vasoproliferative factors (VEGF)
This results in new vessel from the adjacent retinal vessels in an attempt to revascularize the diseased tissue
Neovascularization
Yellow deposits under the retina
Made up of lipids and proteins
Scattered around macular region
“Tombstones” of dead retinal epithelium
Seen in Age-Related Macular Degeneration
Appear in a layer of the retina called Bruch’s membrane
Retinal Drusen
to Look at structures in anterior chamber
lids, lashes, conjunctiva, cornea, anterior chamber, iris, and lens
what do you use?
Slit Lamp Examination
to Look for corneal abrasions, ulcers, foreign bodies
what do you use?
Fluorescein Staining
