Supplemental 4% Flashcards
Normal axial length…
23.5mm
Range is 22.0mm-24.5mm
Normal AC Depth
3.24mm (varies esp with GLC pts)
Normal lens thickness
4.63mm-6.9mm (thicker as it becomes cataractous)
Normal K readings
43.0mm-44.0mm (usually withing 1D of the fellow eye)
Normal CCT (Central corneal thickness)
555mcm
Thicker the K thickness the ____
higher the IOP reading will be(real IOP lower)
Thinner the CCT…
the lower the IOP reading (actual IOP higher)
What test measures CCT?
corneal pachymetry
The goldmann tonometer was calibrated for an _____ CCT
average
Pachy also used pre and post operative refractive sx because…
if K is thin they may not be a candidate for refractive sx
Which test measures the tears using strips of filter paper.
Schirmer’s
Which Schirmer’s test measures lacrimal gland output and does not use any topical anesthetic
Schirmer’s I
Where do you place the filter paper strip when performing Schirmer’s test
on LL’s temporally to K to prevent K abrasion
How long do you leave the Schirmer’s strip in with pt eyes closed?
5 minutes(no blinking or squeezing)
Schirmer’s test that uses a topical anesthetic.
Schirmer’s II
What is the normal range for tears on the Schirmer’s test?
10-30mm
What is the dry eye range measurement on the Schirmer’s test?
<10mm
What is the Excess Lacrimation range on the Schirmer’s test?
> 30mm
What is the test that evaluates Dry Eyes with topical fluorescein dye?
TBUT (tear break up time)
How is TBUT performed?
Fluorescein is instilled and they eye is observed through the slit lamp, ask pt to close their eyes then open. When they open their eyes start timer and watch eye for tear film break up. When dry spots first appear, stop timer- this is their tear break up time. The shorter the TBUT the dryer the eye.
Drop that stains, highlights degenerating corneal and conj cells.
Rose bengal
Rose Bengal used for pts with….
Dry eyes, K abrasions, K lesions, (it stings)
Drop used to evaluate dry eyes, stains blue, does not sting, and stains muco-deficient patches (speckling of K indicates dry patches, muco-deficient or damaged K cells)
Lissamine Green
Uses a device that has a single use microchip and a docking device that analyzes the results of a tear measurement. It is objective and reliable.
Tear Osmolarity Testing
Explain how to perform Tear Osmolarity Testing
First you take a small sample taken of inferior-lateral meniscus, then dock with the device that analyzes it.
What are the ranges of results for Tear Osmolarity Testing?
Dry eye: greater than or equal to 316 mOsmol/L(Hyperosmolarity)
Borderline: 290 mOsmol/L to 316 mOsmol/L
Normal: less than or equal to 290 mOsmol/L
Glare testing is performed with…
BAT(Brightness acuity tester)
This test estimates level of functional outdoor vision like noon day sun, oncoming headlights, light reflected off of sand or snow.
BAT
What pts would you perform BAT on?
pt with CAT
and PCO
You perform BAT test with pt glasses____
on
How do you perform BAT?
Have pt leave glasses on, occlude one eye, have pt hold BAT in front of eye being tested, have them look at the eye chart through the little hole and have them read it.
How big is the hole in the BAT?
12mm
A book of pseudoisochromatic color plates that have numbers, symbols, or patterns that tests for color vision
Ishihara
In the Ishihara, there is a control plate in the beginning of book that ___pts can see, even with no color perception.
All
If pt states that they can’t see the control plate on the Ishihara, that mean…
They may not understand test or they are malingering.
Color vision test that is more precise than pseudoisochromatic plates, has 15 pastel colored chips, similar brightness, subtly different hues, patient arranges in color sequence and must use calibrated lighting for testing
15 hue test (aka Farnsworth-Munsell D-15
Color vision test that uses hue testing
Farnsworth-Munsell D-15 (aka 15-hue test)
How do you perform Farnsworth-Munsell test?
Remove all the chips aside from the starter chip that is glued inside and pt arranges chips in order of hue starting with the color part. Once pt is done, close the box then turn it upside down and then open, all the chips will be upside down and on the back are numbers. Should have been placed in order from 1-15.
Why should you not touch the color part on the chips of the 15-hue test?
Because oils from your fingers can dull the colors
You must use _____lighting for tesitng 15-hue test
calibrated
Medical term defined as chronic disabling visual impairments not correctable by glasses, CL, medical or sx treatments.
Blind
What is considered low vision?
when pt is 20/200 or less
When should braile be introduced?
When pt is 20/200 or less and connot read J13 or J18 @1-5” from the eye
Blind children need___
routine
Children who are born blind can develop _____.
These are repetative motions such as rocking, touching rubbing eyes, waving hands.
Blindisms
Early intervention with children who are born blind is important to help with____(early braille, tactual sensitivity dexterity training)
social integration
A trade off between image size and field of view.
Magnification
Larger images take up ____space
more
Magnification devices limit the field of view because of——
the apperature, the viewing window, the lens, or the video display
What are the 3 main types of magnification?
Linear, Distance, angular
Magnification that increases object size (ex: large print, large screen display, computer text)
Linear magnification
Magnification by moving the object closer (10x mag=reducing viewing distance by 90%, easier for kids than presbyopes)
Distance Magnification
Magnification achieved with optical instrument such as telescopes, telemicroscopes(Image size enlarged without changing viewing distance or modifying object)
Angular magnification
The higher the magnification the more ________
the objects motion is magnified
The most common type of telescopic magnification is…
the Galilean
Telescopic magnification that uses a + lens of one power and a - lens of a greater power.
Galilean
When would we use Galilean telescopic magnification.
When the doctor uses a high minus CL with a plus power spectacle lens on top of it. This essentially creates a Gallilean telescope.
Telescope that has a weak + objective and strong + eyepiece
Astronomic
Image that is formed in an astronomic telescope is ___ so erecting lenses or prisms must br used to turn image upright
inverted
With the astronomic telescope the lenses are separated by the sum of their _____
focal lengths
What are the different types of low vision magnifiers?
Head borne, handheld, stand supported, electronic
What should you take into consideration when recommending low vision aid?
pts physical condition
rule used to estimate the amount of mag that a low vision pt needs to read newsprint
Kestenbaum’s rule
How do you calculate magnification using Kestenbaum’s rule?
Divide VA denominator by numerator
(ex: 20/200 VA =10x mag
Low vision magnifier that are spectacle or loupes
head-borne
low vision magnifiers held in hand
hand held
low vision magnifiers that are with or without self contained illumination
stand supported
What are some instruments that evaluate AC depth>
OCT, Ascan Biometry (optical, contact, immersion), B scan, slit scanning, gonioscopy (physician performs), slit lamp (estimate), penlight (estimate)
How do you measure AC depth with a pen light?
hold the pen light perpendicular to the pts AC just temporal to the canthus, aim light so it illuminates the entire AC from the side. If deep the iris will be flat and iris will be illuminated with light, if shallow, temporal aspect of AC will illuminate but the nasal aspect will be in shadow.
Explain how to use slit lamp to check AC
Have light beems narrow and in very sharp focus with a very bright light. Aim light so one part of beam is on the iris and the other is shining onto their K. Make sure you check nasal, temporal, and centrally. If there is space between the lights then they have space in AC. the more space the deeper AC is . If very close or touching they have narrow AC
Test that measures the forward protrusion of eye
exophthalmometry
Forward protrusion of the eye is known as
proptosis
What causes proptosis?
thyroid eye disease and orbital tumors
A difference in protrusion of the 2 eyes of 2mm or more is considered—-
abnormal
What are the 2 types of exophthalmometers?
Hertel and Luedde
The ophthalmometer that the examiner sits infront of the pt and measures both eyes at the same time. It is a horizontal calibrated bar with removable carriers at each side. There are mirrors on the side that reflect the pts eye and there are mm markings on it. There is a base measurement that stays constant for each measurement on that particular pt, this corresponds to the distance between the 2 eyes.
Hertel
With this ophthalmometer the examiner sits beside pt with pt looking forward, it is a transparent ruler calibrated in mm, one end of it is notched to fit in the bony orbit, is performed one eye at a time.
Luedde
Measures high order aberrations
Wavefront diagnostics
optical distortions in the eye that are not correctable by sphere and cylinder lenses
high order abberations
The wavefront diagnostic unit creates a ___ highlighting individual imperfections(Zernicke)
map of the eye
What is wavefront diagnostic units used for…
Custom Lasik, advanced IOLs such as the tecnis IOL
Test that detects decreased corneal sensitivity due to corneal and neurological conditions.
Corneal sensitivity testing
What condition would pt likely have if doctor is doing corneal sensitivity testing?
HSK, HZV, Long term CL wear, Corneal dystrophies, K scars, trachoma, DM, or 5th CN (aka Trigeminal nerve)
Decrease corneal sensitivity is often the first sign of damage to the ___CN
5th
How do you perform K sensitivity testing?
ask pt to look in opposite direction, approach the K with a cotton wisp, when you touch K with the wisp ask pt if they felt it. Blinking does not mean they felt it, they could have seen it. Use separate wisp for each eye. Ask if they felt the same on both K.
