Vision Science I Flashcards
What ocular structures comprise the Uvea?
Choroid, Ciliary Body, Iris
List the structures of the eye in order from anterior to posterior, I.e., what structures does light pass through as it enters the eye?
Cornea —> Aqueous Humor —> Pupil —> Lens —> Vitreous Humor —> Retina
Cornea —> Anterior Chamber —> Pupil —> Posterior Chamber —> Lens —> Vitreous Humor —> Retina
What structure provides the most optical power in the eye?
Cornea: ~40D or 2/3 of overall power of the eye (~60D)
What structure suspends the lens and attaches it to the ciliary muscle?
Zonule fibers
What happens to the lens as it ages?
Lens turns yellow and becomes stiff, leading to cataracts. The ability for the lens to change shape during accommodation weakens, causing presbyopia.
How does the eye regulate how much light enters the eye?
The iris changes shape (dilate/constrict) to allow more/less light to enter the eye.
What cells detect light in the retina?
Photoreceptors - rods and cones
The fovea is primarily comprised of what type of cell?
Cones
Compare the optical axis and the visual axis.
Optical axis = imaginary line bisects through the center of the cornea, pupil, lens and posterior pole.
Visual axis = imaginary line from the nodal point N’ of the lens to the fovea.
The optical axis and the visual axis are different by 5 degrees.
What area of the eye has the best acuity?
Fovea/fovea centralis
What is the physiological blind spot and why don’t we detect it in everyday life?
The physiological blind spot occurs at the optic nerve where there are no photoreceptors. The optic nerve is where axons of ganglion cells leave the eye to relay visual information to the brain.
Usually, the eye is constantly moving to center an image on the fovea and the brain fills in the missing information from the blind spot so we may perceive light even if the eye does not detect it.
In a typical fungus photo, where is the optic disc relative to the macula/fovea?
The optic disc is roughly 15 degrees nasally displaced relative to the macula
Why does the macula appear dark on the fungus photo?
The macula contains pigments that absorb blue light that is damaging to the eye. The pigment causes the macula to appear darker than the rest of the retina.
What is the thickness of the retina?
~200 - 300 microns.
What is the significance of fluorescein angiography?
Fluorescein angiography is used to image blood vessels, particularly in the eye to detect neovascularization, hemorrhage, or other vascular conditions.
Fluorescein dye is injected into the patient’s blood and blue light is used to photograph/record the vessels. Because it is an invasive technique, new technology has made it obsolete.
