What is the angle subtended by the Snellen letters?
5 minutes of arc.
How can the normal eye distinguish between two points that are separated by an angle of 1 minute?
This corresponds to the distance that the cone cells are from each other.
In regards to the letters on the Snellen chart....
Even though they subtend the same amount of arc, some letters are easier to recognize than others.
Why is the standard testing distance of 20 feet used to test visual acuity?
Because this relaxes accommodation.
How should the illumination in the exam room be during the distant acuity test?
It should be no less than one-fifth of the charts illumination.
What would be an inadequate occluder?
A patients hands because they could look through their fingers.
What is a Malingerer?
A patient who intentionally and falsely claims to have poor vision.
What would be an appropriate acuity tests for an illiterate patient?
E game, Landolt C, and sometimes numbers.
Visual acuity in a patient with posterior subcapsular cataracts will usually worsen when tested in what way?
In bright light.
How can the standard acuity chart or projector produce a falsely high sense of the patients usable vision?
Because it is high contrast.
What are some things that could cause a falsely low density acuity reading?
A fingerprint on projector bulb; smudges on the chart, mirrors, or slides; an old projector bulb.
What does a visual acuity of 20/20 indicate?
The media are clear, the optic nerve is functioning properly, and the fovea is being utilized for fixation.
Why should a patient be told not to squint during the acuity test?
Because squinting will give a falsely high acuity.
What if a patient is unable to read the Snellen 20/400 line?
You should decrease the testing distance until the patient can recognize the 20/400 figure.
If a patient cannot read the 20/400 line until they are 10 feet away, what should the vision should be recorded as?
10/400
A vision of 15/20 is tested how far from the target?
15 feet.
If a patient sees all the letters on a line and one on the next lowest line, how should it be recorded?
That line (ex 20/50) +1
A patient reads all letters on one line, three letters on second line, and one letter on the next lowest line. How is it recorded?
20/40 + 3 + 1.
If a new patients vision is recorded as cc 20/40 od. 20/20 os, how were they tested?
With glasses.
OS refers to vision in which eye?
The left eye.
If a patient is found to have 20/80 without correction, then to have 20/25 with a pinhole, how would this be written?
VA sc 20/80, PH 20/25
If a patient is unable to read the largest letters on the chart, what is another option?
Have patient to count fingers at increasing distances.
If a patient is unable to count fingers at 6 inches, the next option is to?
See if patient can detect hand movement.
How should a hand motion test be performed?
By increasing the testing distance after each accurate response.
Under what circumstances would you use a muscle light to evaluate a patients vision?
When patient has failed to see hand motion.
What is the difference between light perception and light projection?
Light perception is the ability to see light. Light projection is the ability to locate the light.
If a patient is unable to see or locate the light, how is their vision recorded?
NLP (no light perception)
Why is it appropriate to include notes with the visual acuity measurement?
To indicate the patients attention during the test.
Why else is it appropriate to include notes with the visual acuity measurement?
To indicate the use of contact lenses or low vision aids.
Your patient informs you that their vision was checked at their last weeks appointment and does not need to be checked again. What should your response be?
Explain why vision needs to be checked at every visit.
What could be the reason a patient is missing the letters on the right side of the chart?
A visual defect may be present.
Is vision better when testing both eyes or individually?
Vision is usually slightly better when tested together than each eye tested alone.
In an ocular emergency, should visual acuity be checked?
On a case by case basis.
How do you estimate vision of an uncorrected aphake?
A +10.00 or +12.00 diopter trial lens and a pinhole.
How should visual acuity be tested in a patient with nystagmus ?
1. Use a +6.00 diopter trial lens as an occluder and have him keep both eyes open. 2.Allow the patient to tilt their head if they normally do so. 3.Allow the patient to wear his usual distance correction.
The "crowding phenomenon" affects the visual acuity of patients with what type of problem?
Amblyopia
How is it best to check acuity on patients with the "crowding phenomenon"?
Using a row a figures.
When checking a patients near vision, what is most important to do?
Have the patient wear her usual reading glasses or bifocals.
Where should the patient be told to hold the near card?
at 14-16 inches.
Which of the following is not normal near vision? 14/14, J2, N5, L1
L1 (there is no such designation.
What is important when checking the visual acuity of a preschool child?
Make sure he is consistently identifying the pictures.
What should be done if a child has trouble identifying the letters?
Try numbers, rings, pictures, or E's.
What should a child be told regarding the visual acuity test?
That the letters will get too small to read, but to do the best they can.
A disadvantage to the Allen cards is?
It presents single pictures instead of a row of figures.
When testing the vision of a child with the Allen cards, a difference of how many feet between the eyes is considered significant?
A distance of 5 feet or more is considered positive finding for Amblyopia.
By convention, vision is usually tested by checking the right eye first and the left eye second. In which case might it be best to reverse the order?
In a child who is known to be amblyopic in the left eye.
Why is it best to check an amblyopic eye first?
The child might memorize the chart if the strong eye is tested first.
How do you test the presence of vision in an infant?
Seeing in his/her eyes follow a moving light.
How would you test a nonverbal toddler's vision?
Determine if he sees equally well out of each eye.
What are the earliest and easiest letters recognized by children?
HTOV.
A 6 month old baby continues to look at you happily if you cover her right eye. If you cover her left eye, she becomes distracted and tries to move away from the cover. What could this indicate?
Vision could be weaker in the right eye.
What would be the appropriate notation for the child who's vision is compromised in the right eye?
Prefers OS.
Which notation means that a 6 month old infant's vision is probably normal?
Central, steady, and maintained.
What is important when checking vision in children?
Move quickly because they get bored and tired.
What is best to do when teaching a child the E game for the first time?
Send an E card home and let the parents practice with the child.
What is the most important information when checking visual acuity in children?
Any difference between the acuity of the two eyes.
What is NOT true regarding the pinhole?
It compensates for media opacities.
An intelligent literate patient sees 20/400 without correction, 20/200 with correction, and 20/200 with the pinhole. What is the most reasonable assumption?
He has some type of ocular pathology.
What is color vision testing used to detect?
1.Presence of normal color vision, 2.Type and severity of color defect. 3.Those who may not qualify for certain jobs.
Which color test is difficult to perform in the standard office?
Nagel anomaloscope.
How do you test a patient using the color plates?
The patient should be tested with near correction if warn and plates should be held at 14-16 inches from patient.
What should you do before proceeding with the actual color plate test?
The patient is shown a sample that is discernable to normal and abnormal alike.
How long should the patient be given to recognize the number in a color plate?
2-3 seconds.
What are the illumination requirements for the color plates?
Illumination varies according to the type of test administered.
When using color plates, what score is indicated for abnormal color vision?
The score varies according to the type of test.
What are the color plates useful for?
They are to be used as a screening device such as for job applications.
Why is a color plate for that shows no obvious number to normal and abnormal alike useful?
A malinger may invent a number, thus identifying himself.
What is the D-15 color vision test?
Utilizes one fixed, and 15 movable, multicolored caps.
How do you score the D-15 color vision test?
One records the patient's answers on a special score sheet.
What should you do before starting the D-15 color vision test?
The examiner removes the caps from the box and scrambles them.
When explaining the D-15 color vision test, what is the patient told to do?
To arrange the caps in blending order like a rainbow.
When the patient is finished completing the D-15 color test, what should the examiner do?
The examiner then closes the box, latches it shut, and turns it over.
How is the order the patient chose to arrange the caps during the D-15 color test recorded?
It is recorded by connecting the cap numbers on the score sheet.
What will a normal D-15 color test look like?
It will appear as a connected circle.
If there are two crisscrosses of confusion on the D-15 color test, what is the defect?
The defect would be moderate.
How is a type of color defect evident on a D-15 color test revealed?
By the angle of the pattern.
How many colors are in the Farnsworth-Munsell 100 Hue test?
It has 85 caps of various colors in 4 trays.
What is the main disadvantage of the Farnsworth-Munsell 100-Hue test?
It is time consuming to conduct and score.
What is the one case that the Farnsworth-Munsell 100 Hue test is not useful?
For a pituitary tumor.
What does a Farnsworth-Munsell 100 Hue test tray contain?
It has a stationary cap at both ends.
How do you conduct the Farnsworth-Munsell 100 Hue test?
The caps are arranged tray by tray.
In the Farnsworth-Munsell 100 Hue test, what is the patient instructed to do?
Arrange the caps of each tray in a regular hue series.
What would be false regarding the scoring of the Farnsworth-Munsell 100 Hue test?
It produces crisscrosses of confusion.
In the Farnsworth-Munsell 100 Hue test score pattern, where do the outermost spikes of the circle point to?
It points to the wavelength of light where the patient has the greatest confusion.
What does color not depend on?
It does not depend on Chromisity.
Which eye structure is responsible for color vision?
Cones.
What are the photosensitive pigments of the eye sensitive to?
Red, green, and blue.
What are color vision defects believed to result from?
A decrease or absence of one or more visual pigments.
What defect should be color vision tested one eye at a time?
Suspected acquired color defect.
Hereditary color defects most often fall into which category?
Red-green category.
What is NOT true regarding acquired color defects?
They always occur in both eyes.
How can acquired color vision defects be cured?
Can often be cured of the causative factor is eliminated.
Who is effected by Hereditary color vision defects?
More males that females.
Which eye or eyes is effected by Hereditary color vision defects?
Both eyes equally.
What colors are protans most likely to confuse?
Red-bluegreen.
What colors are duetans most likely to confuse?
Green-reddish purple.
What colors are tritans most likely to confuse?
Violet-greenish yellow.
When should children have their color vision checked?
Before starting school.
How can children be tested using the color plates?
By having them trace the number.
When checking color vision in young children by matching tests, what should one must do?
Avoid calling the color by name.
What should the test object be in a color vision matching test?
It should be displayed to the child only momentarily.
What is frequently detected among children with color vision defects?
Reading disabilities.
The prescription of a lens is written in what order?
Sphere power, cylinder power, cylinder axis.
If all the lines of the lensometer target clear at the same time, what should the lens be?
Spherical.
If the single line and triple lines of the lensometer target do not clear at the same time, what should the lens be?
Spherocylindrical.
If the lens is determined to be spherocylindrical, one can deduce that the patient has what?
Astigmatism.
How does a lensometer measure prism diopters?
BY the rings in the reticle.
How is prism direction indicated in the lensometer?
By the position of the target.
IF the target can be centered in the lensometer, how does one determine whether or not there is induced prism due to decentration?
By marking the centers and observing the glasses on the patient.
What do lenses result in that are not correctly centered on visual axis?
Unwanted prism results.
The target of the right lens is displaced to the right, and the lines cross at the third ring. What is the prism power and direction?
3 prism diopters base-in.
The target of the left lens is displaced to the right, and the lines cross between the first and second rings. What is the prism power and direction?
1.5 prism diopters base-out.
When is base-out prism induced?
The optical center separation is less than the pupillary distance with minus lenses.
Can the power of the mid-level trifocal lens segment be read?
It can be read using the lensometer.
What is the best method for reading the add on a no-line progressive lens?
Mark the lens first using the template from that manufacturer.
The distance portion of the lens prescription is -1.25 sphere. You are now reading the bifocal add, and the lensometer dial reads +1.50. What should the add be recorded as?
+2.75
When are slab-off (bicentric) lenses most useful?
Anisometropia.
What is the purpose of the slab-off lens?
To neutralize unwanted vertical prism for reading.
What is the general term for the curvature of the standard surface?
Base curve.
What all could an intolerance to change in base curve cause?
Eyes could feel tired or drawn, swimmy head or nausea, distortion or slant.
What amount can patients tolerate in a base curve change?
0.75 diopters.
What is the first step in reading a pair of glasses with the lensometer?
Adjust the eyepiece of the instrument.
What do you do when adjusting the lensometer eyepiece?
Where your own habitual correction.
What should be done before adjusting the lensometer eyepiece?
Turn the eyepiece to the plus position.
When adjusting the lensometer eyepiece, the eyepiece is slowly rotated to what position?
Until the target is first seen to be clear.
What would failing to properly adjusting the lensometer eyepiece before reading lenses result in?
An inaccurate reading.
What is the first step when beginning to read the right lens?
Try to center the target by moving the stage.
You have centered and read the distant portion of the right lens of a pair of bifocals. What is the next step?
Switch to the left lens and note the position of the target.
How can a lens be read in a lensometer in plus or minus form?
By changing the axis 90 degrees.
What should you do if the single line is clear and you wish to read the lens in minus cylinder form?
Turn the power focusing wheel away from yourself.
You have taken the following lensometer reading: the single line clears at -2.00. The triple lines clear at -3.00. Axis is on 083. What is the prescription?
-2.00-1.00x083
You have taken the following lensometer reading: the single line clears at +6.25. The triple lines clear at +8.00. Axis is on 132. What is the prescription?
+6.25+1.75x132
You have taken the following lensometer reading: the single line clears at -1.50. The triple lines clear at +1.25. The axis is on 097. What is the prescription?
-1.50+2.75x097.
You have taken the following lesometry reading: the single line clears at 2.25. The triple lines clear at -0.25. The axis is on 178. What is the prescription?
-0.25+2.50x088
What is the Geneva lens clock or lens measure used for?
The base curve of a lens.
On what lens is the Geneva lens clock most accurate?
Crown glass.
If the feet of the lens measure are held on a flat surface, how will the hand read?
Zero.
If the lens measure if placed against the convex (outer) lens surface, which set of numbers should be read?
Black numbers.
When placing the lens clock on a lens to read it, how should the clock be held?
Perpendicular to the lens.
When is it possible to take a reading of the segments?
If all three feet rest on the segment.
What is important to do when using the Geneva lens clock to compare different pairs of glasses?
Compare lenses of the same material.
What do the algebraic sums of the lens that measure readings from the front and back surface of a lens represent?
It represents the dioptric power of the lens.
Under what circumstances might neutralizing eyeglasses with trial lenses be used?
When a lensometer is not available.
How is it possible to estimate the prescription of eyeglasses with a trial lens?
With and against motion.
Presence of cylinder can be observed by watching for distortion of a straight edge as a lens is rotated. Which of the following is true regarding the areas of least to greatest distortion?
These areas indicate the cylinder axis, and will be 90 degrees from each other.
Viewing a straight edge through a lens while rotating the glasses to check for presence of cylinder doesn't work in which type of lens?
No-line trifocal
If a straight edge, viewed through a lens, exhibits "against" motion as the lens is moved, which lens should be used to neutralize?
Minus
Plus or minus trial lenses are added or subtracted until the straight edge viewed through the eyeglass lens exhibits how?
Does not appear to move.
Why must care be used when calculating the estimated prescription?
The glasses lens is of an opposite power as the neutralizing trial lens.
Which item is most difficult to read accurately when neutralizing glasses with trial lenses?
Cylinder axis
An eyeglasses lens appears to be neutralized with a +3.00 sphere in the 90-degree meridian and a +6.00 sphere in the 180-degree meridian. What is the estimated prescription?
-3.00 -3.00 x 090
How do you read the bifocal portion of a aphakic spectacle lens?
The distance and bifocal spherical power should be read with the temples toward the technician.
How is the conventional eyeglass prescription recorded?
Sphere, cylinder, axis.
Each of these might be written on the eyeglasses prescription:
Prism, vertex distance, and pupillary distance.
Each of these might be written on the eyeglasses prescription as notations on the add:
Slab-off, segment height, and no-line.
What is true regarding the power of a trifocal segment?
Any power can be ordered.
Which of the following statements is true?
a) a lens has the same amount of cylinder whether it is measured in plus or minus form.
b) minus cylinder is preferred because it is more accurate.
c) Transposition is the conversion of plus to minus cylinder or
Minus cylinder is preferred because it is more accurate.
How is transposition accomplished?
Adding sphere and cylinder, changing cylinder sign, and changing axis 90 degrees.
Why should care be give to figure transposition correctly?
May result in an incorrect prescription.
Transpose: +2.00 -1.00 x 075
+1.00 +1.00 x 165
Transpose: -3.00 +2.00 x090
-1.00 -2.00 x 180
Why is ultrasound a valuable diagnostic tool?
Sound waves are used, not radiation that is harmful to patient.
What does ultrasound employ the use of?
Sound waves.
What does the term A-scan refer to?
One-dimensional amplitude scan.
What is the "A" in A-scan stand for?
Amplitude.
The term biometry could refer to measuring the what?
The axial length of the eye, thickness of an extraocular muscle, or height of a tumor.
What is the axial length of the adult eye?
23 to 24 mm.
The axial length of the eye is important when calculating for what?
The intraocular lens power.
What is Gain?
The sensitivity, or electronic amplification, of the sound wave signal.
What are the parts of an A-scan echo?
Peak, width, ascending limb or leading edge, baseline, descending limb or falling edge.
Where must the retinal echo be when evaluating an axial length scan?
To the left of the scleral and orbital echos.
In an axial length A-scan, if there is only one tall echo from the back of the eye with no other echoes behind it, what would this indicate?
That the sound beam is directed to the optic disc and the measurement is incorrect.
What would extra echoes between the anterior and posterior lens spikes indicate?
A dense cataract.
A measurement error of 1 mm in an axial eye length could result in a postoperative refractive error of how much?
3.0 D
When comparing the axial lengths of a patients left and right eye, how much of a difference between the eyes should signal you to repeat the measurement of both eyes?
0.3mm
How could an A-scan be artificially shortened?
Pressing on the globe too hard with the probe.
Which biometric measurements may be performed with the standardized A-scan?
Axial length, optic nerve thickness, or tumor height.
What are unwanted echoes that do not represent ocular structures?
Pseudo-echoes.
What are the structures on an A-scan?
Posterior lens, orbital fat, cornea, retina, anterior lens, and sclera.
What would be considered a "good" echoe scan?
If all echoes are clearly defined, tall, and steeply rising.
What is the exophthalmometer used to measure?
Ocular protrusion.
What is an exophthalmometer used to indicate?
Thyroid eye disease, orbital tumor, and lid retraction.
When using the Hertel or Luedde exophthalmometer, how should the assistant be positioned?
At eye level with the patient.
When using the Hertel or Luedde exophthalmometer, what does the assistant observe?
The position of the cornea on a scale.
The Amsler grid is used to document visual field defects within what degree?
Within the central 20 degrees.
What types of patients require the Amsler grid?
The patient with macular degeneration, the patient complaining of a central blot in their vision, the patient complaining of a curtain over the left half of vision.
What is important to do when checking a patient with the Amsler grid?
Cover one eye at a time, use good reading light, have the patient use his regular reading glasses, hold the chart 14-16" away.
What is the patient told to do when checking them with the Amsler grid?
To look at the central dot on the grid.
What is helpful to tell the patient when checking them with the Amsler grid?
To outline any missing or distorted areas with a pencil or their finger.
What are some advantages of the Amsler grid?
It is useful for bedridden eye exams, most people easily understand it, it is handy for home use by the patient.
When would the Schirmer's test be indicated?
Dacryocysticitis.
What is the difference between Schirmer's test I and II?
The use of an anesthetic.
What is Schirmer's test I used to measure?
Reflex tears.
What is Schirmer's test II used to measure?
Normal tearing.
What is the measuring time for the Schirmer's test?
5 minutes.
What are some facts regarding the Schirmer's Test?
It is brief; It is portable; It can be done at bedside.
How can constriction of the pupil be accomplished?
Shining a bright light into the eye; having the patient focus on a near object; using miotics.
How can dilation of the pupil be accomplished?
Pinching the patients neck; having the patient focus on a near object; dimming the room lights.
Any pupil smaller than what size is considered mydriatic?
2 mm or smaller.
Any pupil larger than what size is considered mydriatic?
6 mm or larger.
What types of people tend to have smaller pupils?
Older people.
What is another name for unequal pupil size?
Anisocoria.
What could cause abnormal pupil shape?
Surgery, trauma, or birth defect.
What does direct pupillary response refer to?
The reaction of one pupil to light.
How is it possible to test the consensual light response in healthy eyes?
If one pupil reacts to light, the other will react with it.
When checking pupil responses to light, what all should be done?
Dim to the room lights; have the patient look at a distant object;shine the light source from the side.
How do you test pupillary response to accommodation?
Observe the pupils as the patient looks from a distant object to a light source.
How can the Marcus Gunn pupillary sign be identified?
Can be identified with the swinging flashlight test.
What are Argyll Robertson pupills associated with?
Central nervous system syphilis.
What distinguishes Argyll Robertson puppils?
Unreactive to direct or consensual light.
What is associated with Ptosis, Miosis, and lack of perspiration (anhydrosis) on the affected side?
Horner's Syndrome.
What type of disorders can cause a change in pupilary size?
Iritis, angle-closure glaucoma attack, and drug reactions.
What is the most common cause of finding a pupillary defect?
Weak flashlight batteries.
When using a penlight to estimate the depth of the anterior chamber, what technique is best?
Shine the light flatly from one side, in the plane of the iris.
When using a penlight to estimate anterior chamber depth, how would an open angle appear?
It would have little or no shadow.
How does estimating the anterior chamber depth with a penlight work?
An narrow angle and bowed iris cast a shadow on the iris.
Why is it important to estimate the anterior chamber depth prior to dilation?
Because narrow angles precipitate an angle-closure glaucoma attack.
In slit lamp assessment of the corneal periphery, the dark interval should be approximately how much of the total corneal width for the angle to be considered open and safe for dilation?
1/4 of the total corneal width.
What is the angle subtended by the Snellen letters?
5 minutes of arc.
How can the normal eye distinguish between two points that are separated by an angle of 1 minute?
This corresponds to the distance that the cone cells are from each other.
In regards to the letters on the Snellen chart....
Even though they subtend the same amount of arc, some letters are easier to recognize than others.
Why is the standard testing distance of 20 feet used to test visual acuity?
Because this relaxes accommodation.
How should the illumination in the exam room be during the distant acuity test?
It should be no less than one-fifth of the charts illumination.
What would be an inadequate occluder?
A patients hands because they could look through their fingers.
What is a Malingerer?
A patient who intentionally and falsely claims to have poor vision.
What would be an appropriate acuity tests for an illiterate patient?
E game, Landolt C, and sometimes numbers.
Visual acuity in a patient with posterior subcapsular cataracts will usually worsen when tested in what way?
In bright light.
How can the standard acuity chart or projector produce a falsely high sense of the patients usable vision?
Because it is high contrast.
What are some things that could cause a falsely low density acuity reading?
A fingerprint on projector bulb; smudges on the chart, mirrors, or slides; an old projector bulb.
What does a visual acuity of 20/20 indicate?
The media are clear, the optic nerve is functioning properly, and the fovea is being utilized for fixation.
Why should a patient be told not to squint during the acuity test?
Because squinting will give a falsely high acuity.
What if a patient is unable to read the Snellen 20/400 line?
You should decrease the testing distance until the patient can recognize the 20/400 figure.
If a patient cannot read the 20/400 line until they are 10 feet away, what should the vision should be recorded as?
10/400
A vision of 15/20 is tested how far from the target?
15 feet.
If a patient sees all the letters on a line and one on the next lowest line, how should it be recorded?
That line (ex 20/50) +1
A patient reads all letters on one line, three letters on second line, and one letter on the next lowest line. How is it recorded?
20/40 + 3 + 1.
If a new patients vision is recorded as cc 20/40 od. 20/20 os, how were they tested?
With glasses.
OS refers to vision in which eye?
The left eye.
If a patient is found to have 20/80 without correction, then to have 20/25 with a pinhole, how would this be written?
VA sc 20/80, PH 20/25
If a patient is unable to read the largest letters on the chart, what is another option?
Have patient to count fingers at increasing distances.
If a patient is unable to count fingers at 6 inches, the next option is to?
See if patient can detect hand movement.
How should a hand motion test be performed?
By increasing the testing distance after each accurate response.
Under what circumstances would you use a muscle light to evaluate a patients vision?
When patient has failed to see hand motion.
What is the difference between light perception and light projection?
Light perception is the ability to see light. Light projection is the ability to locate the light.
If a patient is unable to see or locate the light, how is their vision recorded?
NLP (no light perception)
Why is it appropriate to include notes with the visual acuity measurement?
To indicate the patients attention during the test.
Why else is it appropriate to include notes with the visual acuity measurement?
To indicate the use of contact lenses or low vision aids.
Your patient informs you that their vision was checked at their last weeks appointment and does not need to be checked again. What should your response be?
Explain why vision needs to be checked at every visit.
What could be the reason a patient is missing the letters on the right side of the chart?
A visual defect may be present.
Is vision better when testing both eyes or individually?
Vision is usually slightly better when tested together than each eye tested alone.
In an ocular emergency, should visual acuity be checked?
On a case by case basis.
How do you estimate vision of an uncorrected aphake?
A +10.00 or +12.00 diopter trial lens and a pinhole.
How should visual acuity be tested in a patient with nystagmus ?
1. Use a +6.00 diopter trial lens as an occluder and have him keep both eyes open. 2.Allow the patient to tilt their head if they normally do so. 3.Allow the patient to wear his usual distance correction.
The "crowding phenomenon" affects the visual acuity of patients with what type of problem?
Amblyopia
How is it best to check acuity on patients with the "crowding phenomenon"?
Using a row a figures.
When checking a patients near vision, what is most important to do?
Have the patient wear her usual reading glasses or bifocals.
Where should the patient be told to hold the near card?
at 14-16 inches.
Which of the following is not normal near vision? 14/14, J2, N5, L1
L1 (there is no such designation.
What is important when checking the visual acuity of a preschool child?
Make sure he is consistently identifying the pictures.
What should be done if a child has trouble identifying the letters?
Try numbers, rings, pictures, or E's.
What should a child be told regarding the visual acuity test?
That the letters will get too small to read, but to do the best they can.
A disadvantage to the Allen cards is?
It presents single pictures instead of a row of figures.
When testing the vision of a child with the Allen cards, a difference of how many feet between the eyes is considered significant?
A distance of 5 feet or more is considered positive finding for Amblyopia.
By convention, vision is usually tested by checking the right eye first and the left eye second. In which case might it be best to reverse the order?
In a child who is known to be amblyopic in the left eye.
Why is it best to check an amblyopic eye first?
The child might memorize the chart if the strong eye is tested first.
How do you test the presence of vision in an infant?
Seeing in his/her eyes follow a moving light.
How would you test a nonverbal toddler's vision?
Determine if he sees equally well out of each eye.
What are the earliest and easiest letters recognized by children?
HTOV.
A 6 month old baby continues to look at you happily if you cover her right eye. If you cover her left eye, she becomes distracted and tries to move away from the cover. What could this indicate?
Vision could be weaker in the right eye.
What would be the appropriate notation for the child who's vision is compromised in the right eye?
Prefers OS.
Which notation means that a 6 month old infant's vision is probably normal?
Central, steady, and maintained.
What is important when checking vision in children?
Move quickly because they get bored and tired.
What is best to do when teaching a child the E game for the first time?
Send an E card home and let the parents practice with the child.
What is the most important information when checking visual acuity in children?
Any difference between the acuity of the two eyes.
What is NOT true regarding the pinhole?
It compensates for media opacities.
An intelligent literate patient sees 20/400 without correction, 20/200 with correction, and 20/200 with the pinhole. What is the most reasonable assumption?
He has some type of ocular pathology.
What is color vision testing used to detect?
1.Presence of normal color vision, 2.Type and severity of color defect. 3.Those who may not qualify for certain jobs.
Which color test is difficult to perform in the standard office?
Nagel anomaloscope.
How do you test a patient using the color plates?
The patient should be tested with near correction if warn and plates should be held at 14-16 inches from patient.
What should you do before proceeding with the actual color plate test?
The patient is shown a sample that is discernable to normal and abnormal alike.
How long should the patient be given to recognize the number in a color plate?
2-3 seconds.
What are the illumination requirements for the color plates?
Illumination varies according to the type of test administered.
When using color plates, what score is indicated for abnormal color vision?
The score varies according to the type of test.
What are the color plates useful for?
They are to be used as a screening device such as for job applications.
Why is a color plate for that shows no obvious number to normal and abnormal alike useful?
A malinger may invent a number, thus identifying himself.
What is the D-15 color vision test?
Utilizes one fixed, and 15 movable, multicolored caps.
How do you score the D-15 color vision test?
One records the patient's answers on a special score sheet.
What should you do before starting the D-15 color vision test?
The examiner removes the caps from the box and scrambles them.
When explaining the D-15 color vision test, what is the patient told to do?
To arrange the caps in blending order like a rainbow.
When the patient is finished completing the D-15 color test, what should the examiner do?
The examiner then closes the box, latches it shut, and turns it over.
How is the order the patient chose to arrange the caps during the D-15 color test recorded?
It is recorded by connecting the cap numbers on the score sheet.
What will a normal D-15 color test look like?
It will appear as a connected circle.
If there are two crisscrosses of confusion on the D-15 color test, what is the defect?
The defect would be moderate.
How is a type of color defect evident on a D-15 color test revealed?
By the angle of the pattern.
How many colors are in the Farnsworth-Munsell 100 Hue test?
It has 85 caps of various colors in 4 trays.
What is the main disadvantage of the Farnsworth-Munsell 100-Hue test?
It is time consuming to conduct and score.
What is the one case that the Farnsworth-Munsell 100 Hue test is not useful?
For a pituitary tumor.
What does a Farnsworth-Munsell 100 Hue test tray contain?
It has a stationary cap at both ends.
How do you conduct the Farnsworth-Munsell 100 Hue test?
The caps are arranged tray by tray.
In the Farnsworth-Munsell 100 Hue test, what is the patient instructed to do?
Arrange the caps of each tray in a regular hue series.
What would be false regarding the scoring of the Farnsworth-Munsell 100 Hue test?
It produces crisscrosses of confusion.
In the Farnsworth-Munsell 100 Hue test score pattern, where do the outermost spikes of the circle point to?
It points to the wavelength of light where the patient has the greatest confusion.
What does color not depend on?
It does not depend on Chromisity.
Which eye structure is responsible for color vision?
Cones.
What are the photosensitive pigments of the eye sensitive to?
Red, green, and blue.
What are color vision defects believed to result from?
A decrease or absence of one or more visual pigments.
What defect should be color vision tested one eye at a time?
Suspected acquired color defect.
Hereditary color defects most often fall into which category?
Red-green category.
What is NOT true regarding acquired color defects?
They always occur in both eyes.
How can acquired color vision defects be cured?
Can often be cured of the causative factor is eliminated.
Who is effected by Hereditary color vision defects?
More males that females.
Which eye or eyes is effected by Hereditary color vision defects?
Both eyes equally.
What colors are protans most likely to confuse?
Red-bluegreen.
What colors are duetans most likely to confuse?
Green-reddish purple.
What colors are tritans most likely to confuse?
Violet-greenish yellow.
When should children have their color vision checked?
Before starting school.
How can children be tested using the color plates?
By having them trace the number.
When checking color vision in young children by matching tests, what should one must do?
Avoid calling the color by name.
What should the test object be in a color vision matching test?
It should be displayed to the child only momentarily.
What is frequently detected among children with color vision defects?
Reading disabilities.
The prescription of a lens is written in what order?
Sphere power, cylinder power, cylinder axis.
If all the lines of the lensometer target clear at the same time, what should the lens be?
Spherical.
If the single line and triple lines of the lensometer target do not clear at the same time, what should the lens be?
Spherocylindrical.
If the lens is determined to be spherocylindrical, one can deduce that the patient has what?
Astigmatism.
How does a lensometer measure prism diopters?
BY the rings in the reticle.
How is prism direction indicated in the lensometer?
By the position of the target.
IF the target can be centered in the lensometer, how does one determine whether or not there is induced prism due to decentration?
By marking the centers and observing the glasses on the patient.
What do lenses result in that are not correctly centered on visual axis?
Unwanted prism results.
The target of the right lens is displaced to the right, and the lines cross at the third ring. What is the prism power and direction?
3 prism diopters base-in.
The target of the left lens is displaced to the right, and the lines cross between the first and second rings. What is the prism power and direction?
1.5 prism diopters base-out.
When is base-out prism induced?
The optical center separation is less than the pupillary distance with minus lenses.
Can the power of the mid-level trifocal lens segment be read?
It can be read using the lensometer.
What is the best method for reading the add on a no-line progressive lens?
Mark the lens first using the template from that manufacturer.
The distance portion of the lens prescription is -1.25 sphere. You are now reading the bifocal add, and the lensometer dial reads +1.50. What should the add be recorded as?
2.75
When are slab-off (bicentric) lenses most useful?
Anisometropia.
What is the purpose of the slab-off lens?
To neutralize unwanted vertical prism for reading.
What is the general term for the curvature of the standard surface?
Base curve.
What all could an intolerance to change in base curve cause?
Eyes could feel tired or drawn, swimmy head or nausea, distortion or slant.
What amount can patients tolerate in a base curve change?
0.75 diopters.
What is the first step in reading a pair of glasses with the lensometer?
Adjust the eyepiece of the instrument.
What do you do when adjusting the lensometer eyepiece?
Where your own habitual correction.
What should be done before adjusting the lensometer eyepiece?
Turn the eyepiece to the plus position.
When adjusting the lensometer eyepiece, the eyepiece is slowly rotated to what position?
Until the target is first seen to be clear.
What would failing to properly adjusting the lensometer eyepiece before reading lenses result in?
An inaccurate reading.
What is the first step when beginning to read the right lens?
Try to center the target by moving the stage.
You have centered and read the distant portion of the right lens of a pair of bifocals. What is the next step?
Switch to the left lens and note the position of the target.
How can a lens be read in a lensometer in plus or minus form?
By changing the axis 90 degrees.
What should you do if the single line is clear and you wish to read the lens in minus cylinder form?
Turn the power focusing wheel away from yourself.
You have taken the following lensometer reading: the single line clears at -2.00. The triple lines clear at -3.00. Axis is on 083. What is the prescription?
-2.00-1.00x083
You have taken the following lensometer reading: the single line clears at +6.25. The triple lines clear at +8.00. Axis is on 132. What is the prescription?
+6.25+1.75x132
You have taken the following lensometer reading: the single line clears at -1.50. The triple lines clear at +1.25. The axis is on 097. What is the prescription?
-1.50+2.75x097.
You have taken the following lesometry reading: the single line clears at 2.25. The triple lines clear at -0.25. The axis is on 178. What is the prescription?
-0.25+2.50x088
What is the Geneva lens clock or lens measure used for?
The base curve of a lens.
On what lens is the Geneva lens clock most accurate?
Crown glass.
If the feet of the lens measure are held on a flat surface, how will the hand read?
Zero.
If the lens measure if placed against the convex (outer) lens surface, which set of numbers should be read?
Black numbers.
When placing the lens clock on a lens to read it, how should the clock be held?
Perpendicular to the lens.
When is it possible to take a reading of the segments?
If all three feet rest on the segment.
What is important to do when using the Geneva lens clock to compare different pairs of glasses?
Compare lenses of the same material.
What do the algebraic sums of the lens that measure readings from the front and back surface of a lens represent?
It represents the dioptric power of the lens.
Under what circumstances might neutralizing eyeglasses with trial lenses be used?
When a lensometer is not available.
How is it possible to estimate the prescription of eyeglasses with a trial lens?
With and against motion.
Presence of cylinder can be observed by watching for distortion of a straight edge as a lens is rotated. Which of the following is true regarding the areas of least to greatest distortion?
These areas indicate the cylinder axis, and will be 90 degrees from each other.
Viewing a straight edge through a lens while rotating the glasses to check for presence of cylinder doesn't work in which type of lens?
No-line trifocal
If a straight edge, viewed through a lens, exhibits "against" motion as the lens is moved, which lens should be used to neutralize?
Minus
Plus or minus trial lenses are added or subtracted until the straight edge viewed through the eyeglass lens exhibits how?
Does not appear to move.
Why must care be used when calculating the estimated prescription?
The glasses lens is of an opposite power as the neutralizing trial lens.
Which item is most difficult to read accurately when neutralizing glasses with trial lenses?
Cylinder axis
An eyeglasses lens appears to be neutralized with a +3.00 sphere in the 90-degree meridian and a +6.00 sphere in the 180-degree meridian. What is the estimated prescription?
-3.00 -3.00 x 090
How do you read the bifocal portion of a aphakic spectacle lens?
The distance and bifocal spherical power should be read with the temples toward the technician.
How is the conventional eyeglass prescription recorded?
Sphere, cylinder, axis.
Each of these might be written on the eyeglasses prescription:
Prism, vertex distance, and pupillary distance.
Each of these might be written on the eyeglasses prescription as notations on the add:
Slab-off, segment height, and no-line.
What is true regarding the power of a trifocal segment?
Any power can be ordered.
Which of the following statements is true?
a) a lens has the same amount of cylinder whether it is measured in plus or minus form.
b) minus cylinder is preferred because it is more accurate.
c) Transposition is the conversion of plus to minus cylinder or
Minus cylinder is preferred because it is more accurate.
How is transposition accomplished?
Adding sphere and cylinder, changing cylinder sign, and changing axis 90 degrees.
Why should care be give to figure transposition correctly?
May result in an incorrect prescription.
Transpose: +2.00 -1.00 x 075
+1.00 +1.00 x 165
Transpose: -3.00 +2.00 x090
-1.00 -2.00 x 180
Why is ultrasound a valuable diagnostic tool?
Sound waves are used, not radiation that is harmful to patient.
What does ultrasound employ the use of?
Sound waves.
What does the term A-scan refer to?
One-dimensional amplitude scan.
What is the "A" in A-scan stand for?
Amplitude.
The term biometry could refer to measuring the what?
The axial length of the eye, thickness of an extraocular muscle, or height of a tumor.
What is the axial length of the adult eye?
23 to 24 mm.
The axial length of the eye is important when calculating for what?
The intraocular lens power.
What is Gain?
The sensitivity, or electronic amplification, of the sound wave signal.
What are the parts of an A-scan echo?
Peak, width, ascending limb or leading edge, baseline, descending limb or falling edge.
Where must the retinal echo be when evaluating an axial length scan?
To the left of the scleral and orbital echos.
In an axial length A-scan, if there is only one tall echo from the back of the eye with no other echoes behind it, what would this indicate?
That the sound beam is directed to the optic disc and the measurement is incorrect.
What would extra echoes between the anterior and posterior lens spikes indicate?
A dense cataract.
A measurement error of 1 mm in an axial eye length could result in a postoperative refractive error of how much?
3.0 D
When comparing the axial lengths of a patients left and right eye, how much of a difference between the eyes should signal you to repeat the measurement of both eyes?
0.3mm
How could an A-scan be artificially shortened?
Pressing on the globe too hard with the probe.
Which biometric measurements may be performed with the standardized A-scan?
Axial length, optic nerve thickness, or tumor height.
What are unwanted echoes that do not represent ocular structures?
Pseudo-echoes.
What are the structures on an A-scan?
Posterior lens, orbital fat, cornea, retina, anterior lens, and sclera.
What would be considered a "good" echoe scan?
If all echoes are clearly defined, tall, and steeply rising.
What is the exophthalmometer used to measure?
Ocular protrusion.
What is an exophthalmometer used to indicate?
Thyroid eye disease, orbital tumor, and lid retraction.
When using the Hertel or Luedde exophthalmometer, how should the assistant be positioned?
At eye level with the patient.
When using the Hertel or Luedde exophthalmometer, what does the assistant observe?
The position of the cornea on a scale.
The Amsler grid is used to document visual field defects within what degree?
Within the central 20 degrees.
What types of patients require the Amsler grid?
The patient with macular degeneration, the patient complaining of a central blot in their vision, the patient complaining of a curtain over the left half of vision.
What is important to do when checking a patient with the Amsler grid?
Cover one eye at a time, use good reading light, have the patient use his regular reading glasses, hold the chart 14-16" away.
What is the patient told to do when checking them with the Amsler grid?
To look at the central dot on the grid.
What is helpful to tell the patient when checking them with the Amsler grid?
To outline any missing or distorted areas with a pencil or their finger.
What are some advantages of the Amsler grid?
It is useful for bedridden eye exams, most people easily understand it, it is handy for home use by the patient.
When would the Schirmer's test be indicated?
Dacryocysticitis.
What is the difference between Schirmer's test I and II?
The use of an anesthetic.
What is Schirmer's test I used to measure?
Reflex tears.
What is Schirmer's test II used to measure?
Normal tearing.
What is the measuring time for the Schirmer's test?
5 minutes.
What are some facts regarding the Schirmer's Test?
It is brief; It is portable; It can be done at bedside.
How can constriction of the pupil be accomplished?
Shining a bright light into the eye; having the patient focus on a near object; using miotics.
How can dilation of the pupil be accomplished?
Pinching the patients neck; having the patient focus on a near object; dimming the room lights.
Any pupil smaller than what size is considered mydriatic?
2 mm or smaller.
Any pupil larger than what size is considered mydriatic?
6 mm or larger.
What types of people tend to have smaller pupils?
Older people.
What is another name for unequal pupil size?
Anisocoria.
What could cause abnormal pupil shape?
Surgery, trauma, or birth defect.
What does direct pupillary response refer to?
The reaction of one pupil to light.
How is it possible to test the consensual light response in healthy eyes?
If one pupil reacts to light, the other will react with it.
When checking pupil responses to light, what all should be done?
Dim to the room lights; have the patient look at a distant object;shine the light source from the side.
How do you test pupillary response to accommodation?
Observe the pupils as the patient looks from a distant object to a light source.
How can the Marcus Gunn pupillary sign be identified?
Can be identified with the swinging flashlight test.
What are Argyll Robertson pupills associated with?
Central nervous system syphilis.
What distinguishes Argyll Robertson puppils?
Unreactive to direct or consensual light.
What is associated with Ptosis, Miosis, and lack of perspiration (anhydrosis) on the affected side?
Horner's Syndrome.
What type of disorders can cause a change in pupilary size?
Iritis, angle-closure glaucoma attack, and drug reactions.
What is the most common cause of finding a pupillary defect?
Weak flashlight batteries.
When using a penlight to estimate the depth of the anterior chamber, what technique is best?
Shine the light flatly from one side, in the plane of the iris.
When using a penlight to estimate anterior chamber depth, how would an open angle appear?
It would have little or no shadow.
How does estimating the anterior chamber depth with a penlight work?
An narrow angle and bowed iris cast a shadow on the iris.
Why is it important to estimate the anterior chamber depth prior to dilation?
Because narrow angles precipitate an angle-closure glaucoma attack.
In slit lamp assessment of the corneal periphery, the dark interval should be approximately how much of the total corneal width for the angle to be considered open and safe for dilation?
1/4 of the total corneal width.