Visual Fields and Eye Diagnostics

retina, optic, chiasm, opposite, tracts, geniculate, radiation, cortex

Visual field pathway

• Light rays striking the ______ generate potentials in the photoreceptors which are sent to the _____ nerve

• Impulses pass through the optic nerve and go to the optic ______

  • Inner nasal halves cross to the ________ side where they join fibers from the outer temporal halves

• Optic chiasm then progresses to the Optic ______

• Fibers of the optic tracts synapse in the dorsal lateral _________ nucleus of the thalamus

• Optic tracts progress to the Optic ________

• Optic radiation progresses to the primary visual ______ in the occipital lobe

Hemianopia

Defect in half of a visual field

Homonymous

Defect is on the same side of visual field

Heteronymous

Defect is on the opposite sides of visual field

blindness

1 - Complete lesion of Optic nerve will cause _________

Bitemporal heteronymous hemianopia

3 - lesion of the optic chiasm will cause what visual pathway dysfunction?

Homonymous hemianopia

4 - Destruction of one optic tract causes which visual pathway dysfunction?

homonymous defect

7 - Optic radiation gets damaged; this is an ocular pathway in the internal capsule, temporal lobe, or occipital lobe and destruction causes this

Monocular blindness

• Site of lesion: optic nerve

• Description of visual field defect: blindness in the affected eye

Bitemporal heteronymous hemianopia

Site of lesion - Optic chiasm

Description of visual field defect: loss of fibers crossing the midline from the nasal half of each retina causes loss of temporal visual field on both sides

homonymous hemianopia

Site of lesion: optic tract

Description of visual field defect: loss of fibers for the visual field on the opposite side to the lesion

Homonymous hemianopia

Site of lesion: optic radiation

Description of visual field defect: loss of fibers for the visual field on the opposite side to the lesion

Homonymous hemianopia with macular sparing

site of lesion: visual cortex (one side)

Description of visual field defect: loss of visual processing for the visual filed on the opposite side of the lesion

Refractory, focal, accommodation, convergence

Vision

• Structures in the eye bends light rays (_________ media)

  • Lens, cornea, and humors

• Light rays converge on the retina at a single _____ point

• _____________

  • Curvature of the lens is adjustable

  • allows for focusing on nearby objects

• ___________

  • Active process of turning the eyes inward to maintain alignment of the visual axes with an object

Myopia

• Nearsightedness

• Globe is too long

• Near vision is clear, Distant vision is blurry

• Corrected by concave lens

Hyperopia

• Farsightedness

• Globe is too short

• Near vision is blurry, distant vision is clear

• Corrected by convex lens

Presbyopia

• Lens is unable to increase its refractive power

• Can’t accommodate on near objects

• Age-related vision problems, why older people need reading glasses

Astigmatism

• Unequal curvature of the cornea

• images are distorted

Legal Blindness

• Best corrected acuity of 20/200 or less in the better eye

• Binocular visual field of 20 degrees or less

Flame hemorrhages

represent bleeding from the inner capillary network of the retina

Dot hemorrhages

small, round, superficial hemorrhages that originate from the superficial capillary network of the retina

Hard exudates

• Well circumscribed, shiny, yellow deposits located within the retina

• Arise at areas of retinal edema and indicate increased capillary permeability

• Contain lipoproteins and lipid laden macrophages

Cotton wool spots

• Yellow/white superficial retinal lesions with indistinct feathery borders

• Represent areas of edema within the retinal nerve fiber layer due to focal ischemia

Retinal neovascularization

• Irregular meshwork of fine blood vessels that grow in response to severe retinal ischemia or chronic inflammation

• very fragile

Cherry red spot

• At the macula

• Associated with central retinal artery occlusion

• surrounded by pallor

conjunctival, corneal, fluorescein, saline, conjunctiva, irregularity, blue, irregularity, altered, green

Fluorescein stain

• Instillation of fluorescein into the ___________ sac to outline any irregularities of the _______ surface

• Equipment

  • ___________ papers or sterile individual dropper units

• Technique

  • Wet fluorescein paper with sterile ______ > touch ___________ > fluorescein spreads over the corneal surface

  • Any ___________ in the cornea is stained by the fluorescein and is more easily visualized using a light with a ____ filter

• Interpretation

  • If no superficial corneal __________, a uniform film of dye covers the cornea

  • If corneal surface has been _______, the affected area absorbs more of the dye and will stain a deeper _____

Slit lamp exam

• Table mounted binocular microscope with adjustable illumination source

• Linear beam of light is projected onto the globe, illuminating an optical cross section of the eye

• The angle, width, length, intensity of the light beam, and magnification (10x-16x) can be adjusted

• Three-dimensional view

anterior, conjunctival, tear, dilated, cells, turbidity, inflammation

Slip Lamp Exam

• ________ half of the globe can be visualized

• Details of the lid margins and lashes, the palpebral and bulbar ____________ surfaces, the _____ film and cornea, the iris, and the aqueous can be seen

• Through a _______ pupil, the lens and anterior vitreous can be seen

• Highest magnification setting can show the abnormal presence of _____ within the aqueous (red or white blood cells, pigment granules)

• Aqueous _________, called “flare” (increased protein concentration) due to ____________ can be detected

Ishihara, Hardy-Rand-Rittler, macula, red-green, color, hues

Ishihara/Hardy-Rand-Rittler plates

• ________ - detects red-green color deficiency

• _____-____-_______ - detects red-green and blue-yellow color deficiency

• Normal color vision requires healthy function of the ______ and optic nerve

• Most common congenital abnormality is ___-_____ color deficiency

• Acquired optic nerve and macular conditions can cause impaired _____ vision

• Depict colored numbers or figures that stand out from a background of colored dots

  • ____ make it difficult for a color deficient patient to distinguish

Tonometry

Determines Intraocular pressure

8-20 mm Hg

Normal IOP

glaucoma

If the IOP is greater than 20 mm Hg, further investigation is indicated for which disease?

Normal monocular visual field

160 degrees of horizontal plane and 135 degrees in the vertical plane

Normal binocular visual fields

exceeds 180 degrees in horizontal plane

Physiologic blind spot

5 degree blind spot in each eye, corresponding to the optic disc and located 15 degrees temporal in a fixed eye

Perimetry

patient fixates on a central target and test objects are randomly presented at different locations throughout the visual field. If objects seen, patient will respond

Visual field mapping

Reason

• Assesses the combined function of the retina, the optic nerve, and the intracranial visual pathway

• Used to detect or monitor field loss due to disease at any of these locations

separately, macular, straight, distortion, missing

Amsler Grid

• Viewed by each eye __________ at normal reading distance and with reading glasses (if used)

• Most commonly used to test _______ function

• While fixating on the central dot, the patient checks to see that the lines are all _______, without __________, and that no spots or portions of the grid are _______

scotoma

blank area; either central or paracentral; can indicate disease of the macula or optic nerve

Metamorphopsia

Wavy distortion of the lines while looking at an amsler grid

can indicate macular edema or submacular fluid