Download OPT 210 Final Content 2025 Update: Comprehensive Guide to OCT and Perimetry and more Exams Advanced Education in PDF only on Docsity!
OPT 210 FINAL CONTENT 2025 UPDATE WITH CORRECT
SOLUTIONS!!
What is an OCT? noninvasive imaging technique that uses low coherence, near infrared light to capture micrometer resolution and penetrate optical media to create cross sectional data
The light paths existing in OCT are nearly the same. What does this allow for? high resolution
If the light wavelength of OCT is longer than visible light, what does this allow for? ability to see through cornea, lens, vitreous, retina (translucent and even opaque materials)
What does an OCT of the angle-anterior chamber include? cornea, iris, angle (nasal and temporal)
What is the purpose of a single angle OCT? -to estimate angle openness, when patient is unable to tolerate gonio -to confirm iris approach -can measure angle in degrees
When performing angle OCT, what angle is considered narrow? <15°
What is true about quality of single angle OCT? -must include angle (where iris attaches/inserts into angle) without obstruction -must be able to recognize structures (starting with scleral spur)
What are limitations of single angle OCT? -can only scan 1 nasal and 1 temporal angle -unable to visualize amount of TM pigment -unable to visualize most abnormal findings (synechiae, neo, etc)
What are some tips to mapping an angle OCT? -find scleral spur -ciliary body is directly behind it -TM is in front of scleral spur -schwalbe's line is located on the anterior chamber side of the sclera to cornea histological transition -look at iris approach (specifically peripheral iris)
What is the purpose of pachymetry? -to understand glaucoma risk and true IOP -to measure changes in corneal thickness (edema, thinning)
What are examples of highly reflective structures that will block light transmission? -blood vessels -hemorrhages -exudates -pigment/RPE hyperplasia -floaters -media opacities -RPE
What is the variability of OCT machines? 4-10 microns
When assessing ONH disease, where should you take an OCT? -disc rim RNFL scan (thickness) -circum or peripapillary RNFL scan (thickness) -parafoveal GCL scan (thickness)
What is the ganglion cell complex? -RNFL + GCL + IPL
When assessing macular disease, where should you take an OCT?
-macular overall thickness scan macular dense scan -macular radial scan (star through fovea each time)
What are the common scan types of anterior segment OCT? -angle-anterior chamber -angle (single)
What is included in an angle-anterior chamber OCT? cornea, iris, angle (nasal and temporal); this gives a big picture view
What is the purpose of a single angle OCT?? to estimate angle openness when a patient cant tolerate gonio (also to confirm iris approach)
What angle is considered to be narrow for an angle OCT? <15°
What are limitations of an angle OCT? -can only scan 1 nasal and 1 temporal angle -unable to visualize TM pigment -unable to visualize abnormal findings
Where are photoreceptor outersegments thickest? fovea
What is Henle's fiber layer? RNFL axons traveling obliquely rather than horizontally
What retinal layers are absent above the foveal pit? superficial retinal layers; allows for the best light transmission
What are examples of artifacts in an OCT? -blood vessels -hemorrhages -exudates -pigment/RPE hyperplasia -floaters -media opacities -RPE
What is the result of loss of hyper reflective structures? increase light transmission/reflectivity
What makes up the ganglion cell complex? -RNFL -GCL -IPL
What are examples of scans that can be done for optic nerve disease? -disc rim RNFL scan + thickness -circum or peripapillary RNFL scan + thickness -parafoveal GCL scan + thickness
What is perimetry? process of measuring differential light sensitivity; ability to see contrast difference between a stimulus relative to a known background luminance
What is the purpose of perimetry? -early and efficient detection of functional loss of the visual system -most important clinical tool for measuring visual function outside the fovea -to diagnose and manage optic nerve disease, neurological disease, and retinal disease (central 30°) -to evaluate vision standards of visual disability
What are clinical indications of perimetry? -atypical exam findings
-optic neuritis -papilledema -thyroid orbitopathy -optic nerve drusen -optic nerve atrophy/pallor -presence of lesion
What neurological diseases can be indications for perimetry? any lesion that can affect the CN2 pathway
T or F: a lesion in the inferior temporal arcade but nasal to the fovea will result will result in a defect in the superior temporal quadrant of the visual field. True; visual field defects are described in relation to the fovea/center of vision
Is perimetry tested monocularly or binocularly? monocularly; due to overlap of visual fields between the eyes; this can help determine where the lesion is located
What has the highest sensitivity in island of vision? fovea; highest threshold/lowest stimulus brightness
What is the physiological blindspot? optic nerve; absolute scotoma is present independent of stimulus value
Where is the optic nerve located from fixation along the horizontal meridian? 15°
located 60° below the horizontal meridian
What are the monocular visual field limits? -60° superior to fixation -60° nasal to fixation -70-75° inferior to fixation -100-110° temporal to fixation
What is the height and shape of island of vision dependent on? -luminance -contrast -age -stimulus size (and duration) -disease
What is an absolute defect? zero sensitivity (blind in that location)
-learning curve -ability -pupil size -refractive error -anterior anatomy -media opacities
How is perimetry a learning curve? 15% of normal first time takers give abnormal results; need multiple tests to determine a baseline
How does pupil size impact visual fields? -should be performed undilated -pinpoint pupils can reduce retinal luminance -large pupil may reduce sensitivity in central target locations
How does refractive error impact visual field? lack of correction reduces sensitivity by 1dB per 1D of blur
How does anterior anatomy impact visual fields? -prominent eyebrows -large noses/bridges -drooping eyelids
-small palpebral apertures
these all cause artifacts
How do media opacities impact visual fields? -nuclear cataracts and dry eye can depress sensitivity (general or diffuse depression) -corneal opacities, cataract opacities, vitreous opacities can cause localized depression of sensitivity
What does a manual perimeter test? central 30° of visual field
What equipment is used for tangent screen? -felt square black felt with concentric circles, radial lines and a central white fixation target -wand with test objects of different sizes
What is the set up for tangent screen manual perimetry? -moderate room lighting -patient seated 1 meter from the screen and eye level to the fixation target -patient wears habitual rx with one eye covered at a time -examiner stands on the side being tested -can retest with different distances
What are characteristics of arc perimeter? -both central and peripheral fields can be examined -patient places chin on chin rest and fixates on reflection of own eye -bowl is rotated every 30°; 8-12 meridians tested -plots out 90° -tested at 33 cm
What is the goldmann perimeter used for? low vision patients (reduced BCVA or severely constricted fields)
What are characteristics of the Goldmann perimeter? -bowl extends to 90° to each side of fixation -light is projected into bowl -adjustable stimulus values (size, intensity, light transmission)
What is the standard test stimulus for goldmann perimetry? III4e
What is the procedure of goldmann perimetry? -Insert blank pantograph into holder -Attach colored pencil to projection arm (different color for each isopter) -Insert the appropriate correcting lens; occlude one eye
-Select stimulus -Technique for stimulus movement: Kinetic: 5° per second Move from non-seeing to seeing -Fixation monitoring (by operator) through telescope in center of bowl -Plot 8 directions or clock hours / patient hits clicker when light first seen
What are disadvantages of automated perimetry? -Uniformity -Reproducibility -Patient fixation monitors -Statistical analysis -Patient reliability -Random presentation -Screening and threshold strategies -Central and peripheral (near-periphery) testing
What are disadvantaged for automated perimetry? -cost -test time -patient dependent
What are the two types of automated perimetry? -standard automated perimetry * -frequency doubling perimetry
III and V are most often used (V for low vision) I, II, IV are most often used in research
What is the stimulus brightness? 39 dB is the dimmest that a young observer can see
What is the background luminance for perimetry? 31.5 abs
What is the stimulus duration? 200 ms (based on re fixation speed)
What is the stimulus timing? 200 ms (may depend on individual response time)
What is the stimulus velocity/ direction? 2-5°/sec
What is the stimulus color and background color? white on white or blue on yellow
How is differential light sensitivity calculated? brightness= 1/threshold sensitivity (dB)
What is the normal peripheral sensitivity range? 20-40 dB; depends on age and disease
What is the abnormal vision range? 0-30 dB but can depend on age/disease
What are the test types for automated perimetry? -threshold -suprathreshold -kinetic
What test patterns are available for automated perimetry? -Central 30- -Central 24- -Central 24-2C (SITA Faster option only) -Central 10- -Peripheral 60- -Macula
