eye issues

strabismus

• cross eyes

• if the center of focus in each eye is off too far, the brain does not perceive the image being viewed as one, unified image – instead

  the two versions of the image will either diverge or converge, depending on the nature of the cross-eyed condition

convergent strabismus

Both right and left medial rectus muscles contracting at the same time

divergent strabismus

Left lateral rectus contracting more than right lateral rectus

tunics

• fibrous,

• vascular

• retinal

fibrous tunic

sclera and cornea

• thickest layer

• dense fibrous connective tissue

  • both collagen and fibers

• thickest at posterior end and thinest at anterior end

  • provides physical support and protection of internal eye structures

  • serves as attachement site for the 6 extroocular muscles that move the eye,and help maintan eye shape for focusing ability

vascular tunic

iris, cilliary body, choroid

• behind iris is the pupillary muscles that dilate or constrict the pupil

  • circular muscles that constrict of the pupil when they contract and radial muscles cause dilation of the pupil

• smooth muscles cells, allows for lens accomocdation

Sensory and neural tunic

• retina

  • photoreceptors

two cavities

• anterior and posterior cavity

anterior cavity

aqueous humor

posterior cavity

vitreous humor

glaucoma

when the canal of schlemm is blocked and aqueous humor can’t drain properly, Pressure pushes backward on the lens, interfering with the ability of the lens to focus light on the retina,

rods

found along margins of retina and scattered everywhere on its surface aside from the macula lutea and fovea centralis

• responds to dim wavelengths of light

cones

• bright wavelengths of light and provide collor vision

  • most concentrated in the macula lutea and fovea centralis

emmetropia

normal 20/20 vision

• light focuses directly on the retina

accommodation

when our lense changes shape to maintain appropriate focal distrance to the retina

myopia

nearsightedness

• light focuses in front of the retina

• eyeball is too elongated or lens is too rounded

hyperopia

farsightedness- light focuses behind the retina

• eyeball is too shallow or the lens is too flat

presbyopia

old sightedness- older individuals become farsighted as their lens loses elasticity

nyctlaopia

night blindness

astigmatism

An unusual or abnormal curvature to either the cornea or the lens (or both) can cause multiple refractions of light onto the retina, none of which are focused correctly by accommodation