- sensitivity of px visual field
- checking photoreceptors (cones/rods)
- requires dim room lighting
-each point = spot on retina/mapped out
Visual field testing
- highest point = fovea
- decreases into periphery
- less sensitive with age (decrease superior)
Hill of vision
-blind spot
-15 degree line of sight (ONH)
Scotoma
-Confrontation
-Tangent
-Automated
Types of Visual Fields
-general idea
-gross indication of sensitivity of each 1/4 section
-compare px to examiner
Confrontation VF
-not routinely used
-central 30 degrees
-using black felt forms
-brings forward various size white targets
-maps blind spot(scotoma)
Tangent Screen VF
- most commonly used
-uses static perimetry method
-testing central 60 degrees (30 in all directions)
-starts bright until not visible - target spot brightness = retinal sensitivity
-high value = very dim can be seen
-low value = bright light required to see
Automated VF
-90 temporally
-60 nasally
-70 inferiorly
Normal field of vision
-must be shorter than latency time for voluntary eye movement
-px looks at target= disspear on them
Stimulous Duration
-top of hill must be monitored
- HVF plot/measure blind spot, if px clicks when lit then incorrect positioning
Fixation monitoring
-dimmest target seen
-starts with 4dB brighter than expected
-descreases by 4dB when target seen
-increases by 2dB if px not responding
-50% of time target seen= threshold
- central threshold= glaucoma
-suprathreshold = general screening
Threshhold VF
-target moves/changes sizes &brightness
-for px who cant focus (kids/disabilities)
-confrantion/tangent/goldman
Kinetic Perimetry
-px covers one eye
-examiner moves hand around
-px signals
- px uncorrected/no glasses
-1 meter distance
-1,2 or 4 fingers at 45-90 degrees
-compare with examiners results
Kinetic Confrontation
-using wall/poster
-not commonly used
- but more accurate than confrontation
-maps central 30 and scotoma
- stare at target while bringing target inwards
Kinetic Tangent
- most common
- 33cm from cornea
Kinetic Goldman
- target doesn’t move/stationary
-starts dim, increases until seen - size doesn’t change
-detects scotomas (blind spots)
-automated
Static Perimetry
- false positive (clicking at nothing) 33% or 3/10
-False negative(not clicking when seen) 33%
-both mean unreliable test results
Automated VF errors
-20 degrees consisting of 17-19 sections
-early detection of glaucoma,retina,neurological
-glasses optional
-screening type = 45 sec-2 mins
-threshold= 4-5 mins
-series low spatial frequecy gratings
-stimulates ganglionic cells (neurons) in retina/ detects early glaucoma before others
Frequency Doubling Technology (FDT)
-photokeratoscopy/videokeratography
-corneal surface not spherical
-measures thousands points entire surface
-creates 3D image
- screens before OMD referrals
- diagnose keratoconus
-pre-post op for PRK/Lasik
-specialty contact lens fittings
Corneal Topography
-measures corneal thickness
-device is ultrasonic measured in microns ym (AVG 540ym)
-monitors keratoconus
- detects corneal edema
-pre/post Lasik
-glaucoma because thinner central cornea
Pachymetry
-creates baseline for conditions/diseases
-typical range= 15-60 degrees
-requires 2mm pupil size
-optomap doesn’t have pupil size requirements
- autofluorescense detects chemical tissue changes
-wait 5-10 mins for VA
Fundus Photography
-ultra-wide field (opthalmoscope)
-scanning laser (green/red wavelength)
-200 degree view without DFE (82%)
-sees through cataracts/corneal opacities/vitreous hemorrhages
-green laser = superficial
-red laser = deep layers
OPTOMAP
-non-invasive
-waves of energy
-images retina + ONH
- several directions= 3D image
1) Heidelberg Retinal Tomograph (HRT)
2) Optical Coherence Tomograph (OCT)
Tomography
- depth of anterior chamber/corneal thickness
-see 10 retinal layers/thickness
-cross-sections of pathologies
-glaucoma (ant. chamber/cup shape/disc/RNFL)
Tomography benefits
