Techniques and details: visual acuity in the adult patient Flashcards
a. Normal visual acuity (with or without) glasses implies:
a. Ocular media are relatively clear in the visual axis
b. The fovea centralis is relatively intact
c. Cranial nerve 2 and the visual
b. Normal visual does not indicate the eye is free of?
disease
snellen chart: how to Recordpatient’s visual acuity
a. the smallest line on which patient can distinguish more than one half the letters is visual acuity. The number of letters missed on the same line also should be recorded such as 20/20-1 or 20/40-2
Fovea, found in the center of macula, is the what?
area of max visual acuity. It’s 1.5 mm in diameter and contains only cones.
Max visual acuity occurs in
~3 degrees of visual field. Once outside f. acuity is reduced
Acuity is poor at?
periphery of retina
Legal Blindness:
distant vision of 20/200 or less in the better eye when correction the best possible correction has been applied, and/or; a visual field that subtends an angle of less than 20 degrees
Presbyopia: “old vision”
a. Age related loss of elasticity in lens
b. Leads to far sightedness for near vision
Ciliary muscles relaxed:
for far vision
Ciliary m. contracted:
for accommodation
Presbyopia:
inability to accommodate would lead to far sighted ness for near vision
Refraction:
bending of light waves, about 80% of refraction occurs in cornea and about 20% in lens
Normal acuit:
emmetropia- the refraction of the cornea and lens match the eyes length (true emmetropia is rare)
Refractive myopia and near .sightedness
parallel light rays come to focus in front of the retina. Refratctive power of cornea/lengs is too great
Axial myopia and extreme near sightedness
parallel light rays come to focus way in front of the retina, the eyeball is too long for the refractive power of the eye. There is an increased chance of retinal detachment
Refractive hyperopia and far sightedness-
parallel light rays come to focus behind of the retina. The refractive power of the cornea/lens is too little
Axial hyperopia and extreme far sightedness-
parallel light rays come to focus way behind the retina. The eyeball is too short for refractive power of the eye. There is an increased change of acute glaucoma.
astigmatism:
a. unequal refraction in different meridians of eyeball
b. might affect as many as 1 in 3 people. Incidence increases with age
c. Astigmatism can cause difficulties in seeing fine detail
Regular astigmatism:
the lines should look the same
rough assessment: estimation of the visual fields by confrontation (defects)
a. negative defects: objective blind spots
b. positive defects: perceived blind spots
hemianopia:
blindness in half visual field
quadrantanopia:
blindess in one quarter of V.F
bitemporal hemianopia
midline of optic chiasm:
left homonymouse hemianopia with relative preservation of macular vision can be seen with?
migraine, vertebral TIAs, and /or occlusion f posterior cerebral arter. If macular vision is preserved, the patient might be unaware of visual deficit
First exam component: ophthalmologic exam:
a. Are pupils equal in size and round?
b. Do the pupils react to light?
c. Do pupils accommodate to near vision?
Second ophthalmologic exam component
a. Assesses alignment of eyes in primary/neutral position
third ophthalmologic exam component:
a. first assesses fixation with eyes in primary/neutral position
b. then assess conjugate pursuit movements in “yoked” pairs of EOMs
c. Attention to pupillary shape, size, and response to external stimuli provides extremely valuable clinical information. No ocular examination is complete without testing of extraocular muscle movement
