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