NRSR 21 Lesson 21: Visual Problems Flashcards
Glaucoma
Excess production or decreased outflow can elevate intraocular pressure above the normal 10 to 21 mm Hg (Lewis 385)
The most frequent cause of blindness among African Americans (Lewis 388)
Accomodation
a process that allows a person to focus on near objects, such as when reading. Anything altering the clarity of the lens affects light transmission. (Lewis 385)
Refraction
Refraction is the ability of the eye to bend light rays so that they fall on the retina. In the normal eye, parallel light rays are focused through the lens into a sharp image on the retina. This condition is termed emmetropia and means that light is focused exactly on the retina, not in front of it or behind it. (Lewis 385)
Myopia
can see near objects clearly (nearsightedness), but objects in the distance are blurred. (Lewis 385)
Hyperopia
can see distant objects clearly (farsightedness), but close objects are blurred. (Lewis 385)
Astigmatism
caused by unevenness in the cornea, which results in visual distortion. (Lewis 385)
Presbyopia
a loss of accommodation, causing an inability to focus on near objects. It occurs as a normal process of aging, usually around age 40. (Lewis 385)
Iris
The iris provides the color of the eye. This structure has a small round opening in its center, the pupil, which allows light to enter the eye. The pupil constricts via action of the iris sphincter muscle (innervated by CN III [oculomotor nerve]) and dilates via action of the iris dilator muscle (innervated by CN V [trigeminal nerve]) to control the amount of light that enters the eye. (Lewis 386)
Lens
a biconvex, avascular, transparent structure located behind the iris. It is supported by the anterior and posterior zonule. The primary function of the lens is to bend light rays so that they fall onto the retina. Accommodation occurs when the eye focuses on a near object and is facilitated by contraction of the ciliary body, which changes the shape of the lens. (Lewis 386)
Ciliary Body
The ciliary body consists of the ciliary muscles, which surround the lens and lie parallel to the sclera; the ciliary zonule, which attaches to the lens capsule; and the ciliary processes, which constitute the terminal portion of the ciliary body. The ciliary processes lie behind the peripheral part of the iris and secrete aqueous humor. (Lewis 386-387)
Choroid
The choroid is a highly vascular structure that serves to nourish the ciliary body, the iris, and the outer portion of the retina. It lies inside and parallel to the sclera and extends from the area where the optic nerve enters the eye to the ciliary body (see Fig. 21-1). (Lewis 387)
Retina
The retina is the innermost layer of the eye that extends and forms the optic nerve. Neurons make up the major portion of the retina. Therefore retinal cells are unable to regenerate if destroyed. The retina lines the inside of the eyeball, extending from the area of the optic nerve to the ciliary body (see Fig. 21-1). (Lewis 387)
Normal Physical Assessment of Visual System
- Visual acuity 20/20 OU; no diplopia
- External eye structures symmetric and without lesions or deformities
- Lacrimal apparatus nontender and without drainage
- Conjunctiva clear; sclera white
- PERRLA
- Lens clear
- EOMI
- Disc margins sharp
- Retinal vessels normal, with no hemorrhages or spots
EOMI, Extraocular movements intact; OU, both eyes; PERRLA, pupils equal, round, reactive to light and accommodation. (Lewis 390)
Visual Acuity Testing
Patient reads from Snellen chart at 20 ft (distance vision test) or Jaeger’s chart at 14 in (near vision test); examiner notes smallest print patient can read on each chart.
Determines distance and near visual acuity (Lewis 390)
Confrontation Visual Field Test
Examiner shines light into patient’s pupil and observes pupillary response; each pupil is examined independently; examiner also checks for consensual and accommodative response.
Determines if patient has normal pupillary response (Lewis 390)
Pupil Function Testing
Examiner shines light into patient’s pupil and observes pupillary response; each pupil is examined independently; examiner also checks for consensual and accommodative response.
Determines if patient has normal pupillary response (Lewis 390)
Tono-pen Tonometry
Covered end of probe is gently touched several times to anesthetized corneal surface; examiner records several readings to obtain a mean intraocular pressure (see Fig. 21-6).
Measures intraocular pressure (normal pressure is 10-22 mm Hg) (Lewis 390)
Ophthalmoscopy
Examiner holds ophthalmoscope close to patient’s eye, shining light into back of eye and looking through aperture on ophthalmoscope; examiner adjusts dial to select one of lenses in ophthalmoscope that produces desired amount of magnification to inspect retina (see Fig. 21-7).
Provides magnified view of retina and optic nerve head (Lewis 390)
Color Vision Testing
Patient identifies numbers or paths formed by pattern of dots in series of color plates.
Determines ability to distinguish colors (Lewis 390)
Keratometry
Examiner aligns projection and notes readings of corneal curvature.
Measures corneal curvature; often done before fitting contact lenses, before doing refractive surgery, or after corneal transplantation (Lewis 390)
Common Assessment Visual Abnormalities: Pain ( Foreign body sensation)
Superficial corneal erosion or abrasion; can result from contact lens wear or trauma; conjunctival or corneal foreign body (Lewis 391)
Common Assessment Visual Abnormalities: Pain (Severe, deep, throbbing)
Anterior uveitis, acute glaucoma, infection; acute glaucoma also associated with nausea, vomiting (Lewis 391)
Common Assessment Visual Abnormalities: Spots, floaters
Most common cause is vitreous liquefaction (benign phenomenon); other possible causes include hemorrhage into the vitreous humor, retinal holes or tears (Lewis 391)
