Refraction 1 Flashcards
Name the chart that measures VA?
Snellen chart
Name of the color deficiency test 2
Ishihara Test
Farnsworth D-15
What is the purpose of the duochrome chart?
Refine the final sphere in the visual assessment
Which equipment is used to check refractive error in young children?
Retinoscope
Name the test that requires red lens on od and a green on the os?
Worth’s four dot test
What would the chief complaint be of a patient with diplopia?
Double vision
Term for myopia resulting from the elongation of the globe of the eye
Axial myopia
What is the term for the eye’s ability to change in power in order to focus on objects at different distances?
Accommodation
What is the purpose of mydriatic drops in the eye?
Dilates the pupil
What is the term when both eyes are directed in the same direction except when one eye is covered?
Heterophoria
What are the 4 forms of medication that is instilled into the eye?
Solution, suspension, ointment, systematic
What are the four steps of subjective refinement? In order. 4 MARKS QUESTION IN QUIZ
Sphere, cylinder axis, cylinder power, sphere
What does cycloplegic agents do? 2
act by paralyzing the sphincter muscle of the iris, causing dilation
paralyzes the ciliary muscle, which inactivates accommodation
What do Mydriatic agents do?
act on the iris musculature and dilate the pupils
What do miotics do?
act by stimulating the sphincter muscle of the iris, which constricts the pupil
What can topically applied steroids do the eye? 4
- raise the pressures
-activate the growth of virsus
-activate the growth of bacteria
-cause delay in wound healing
Explain VA and how it is determined
determined by the smallest object that can be clearly seen and distinguished at a distance compared to distance the patient is from the chart letters / distance from the chart at which a normal person can see.
What happens if the patient squints when obtaining the VAs?
false/wrong reading, only allows central rays in which makes the vision better
What does ocular motility refer to?
the movements of the eye in all directions of gaze and to its relationship in movement with its fellow eye
When assessing the ocular motility, what are we looking for? 3
-the vision or fixation of each eye
-alignment of both eyes in all directions of gaze
-the ability of the two eyes to work together binocularly
What are the 9 positions of gaze?
-dextroversion (right gaze),
-levoversion (left gaze),
-supraversion (straight-up gaze),
-infraversion (straight-down gaze)
-4 oblique positions
-primary gaze
What is the Hirschberg’s test?
a penlight test- shines the light in the child’s eyes and notes the position of the reflex of light.
What 4 conditions could be present if the light reflex in the hirschberg’s test is not in the center of the pupil?
i. Esotropia - reflex is temporally placed in one eye and is normal in the other eye
ii. Exotropia – reflex is nasally placed in one eye.
iii. Hypertropia – reflex is inferiorly placed
iv. Hypotropia – reflex is superiorly placed.
What is the Krimsky’s test?
Prisms are placed in front of the fixating eye until its forced to move over (note the prism needed, it is the same as the deviation present)
What is the cover test? and what does/could it show?
manifest strabismus tropia is revealed by observation by observation of any eye movements of the uncovered eye to take up fixation when the cover is placed before the fellow eye.
What is the near point of convergence?
the point at which fusion can no longer be maintained and one eye deviates outward. The px will see double
What is the 4 worth dot testing? 3
investigating fusion, suppression, and binocular functions of the eyes ability to work together
4 worth dot test, 2 red lights seen?
left eye suppression
4 worth dot test, 3 green lights seen?
right eye suppression
4 worth dot test, 3 green on the left and 2 red on the right seen?
Esotropia: no suppression
4 worth dot testm 2 red on the left and 3 green on the right seen?
Exotropia: no suppression
What is the difference between subjective and objective refraction?
subjective = we determine and evaluate the refractive error based on the patient’s input
objective = we determine and evaluate the refractive error based purely on our judgment
4 worth dot test, 1 red, 2 green and 1 white seen?
normal result
You are performing retinoscopy on a patient and you add a minus trial lens frame to bring the reflex to no movement. Was the light against movement or with?
the light is against the movement
What can irregular movements of the light during retinoscopy indicate? 3
keratoconus, corneal scarring, catarcts
What test do we do to determine if a patient has uncorrected refractive error or an ocular pathology?
pinhole test - cuts out periphery rays of light, pinhole will improve vision if it is a refractive error
What is bincoluar balancing?
equalize the accommodative effort between the 2 eyes. They do not necessarily accommodate by the same amount under monocular conditions
What happens if binocular balancing is not achieved?
If the prescriptions are not balanced the eyes accommodate by the least amount possible to produce a clear image in one eye. The other eye may have a slightly blurred image and asthenopia could result.
If the patient says the second lens si darker and smaller during refraction, what does this mean and which lens should you use?
it means they are overcorrected and we are adding too much minus
choose the minus lens
What are 3 techniques used to determine astigmatism axis?
jackson cross - cylinder
fan-and-block technique
astigmatic clock
What are the 2 methods to measure he amplitude of accommodation and name the technique
Technique - Blur technique
method 1 - push-up-to blur
method 2 - push down to clear
What does confrontational field test?
detects a patient’s field of view in comparable with their own (normal).
What is the order of the process of general refraction? 5
a. Perform lensometry to get current rx if px has glasses & Medical hx
b. Take autorefractor readings (Objective Ref.)
c. Take aided VA with current glasses
d. Subjective Refraction
e. Compare aided VA with Subj. Refract. Result with current glasses.
What is the purpose of the fogging technique?
to create a situation where an attempt at accommodating will blur the vision, inducing relaxation of accommodation
What are 3 types of myopia?
axial (eyeball too long)
curvature (increase in corneal curvature)
index (refractive change in the lens)
What are the 2 types of hyperopia/hypermetropia?
axial (eyeball too short)
curvature (flattening of the cornea/lens)
What is absolute hypermetropis?
the portion of the refractive error that is not compensated for by accommodation
What is accommodation?
adjustment by the eye for seeing different distances
What is amplitude of accommodation?
the difference between the maximum and minimum powers of a particular eye and therefore gives the total amount of accommodation available
What is aniseikonia?
a condition in which the ocular image of an object as seen by one eye is different in size and shape to the other and cannot be fused
What is anisometropia?
a condition in which there is a difference in the refractive error of the two eyes
What is aphakia?
absence of the lens of the eye
What is asthenopia?
a wastebasket term denoting a number of sensations that accompany uncorrected
refractive error and problems in ocular motility
What is negative accommodation?
to focus from near to distance, the eye decreases its D power
What is positive accommodation?
to focus on a near object, the eye increases its D power
What is emmetropia?
a normal eye with no refractive error
What is far point of accommodation?
that point conjugate with the centre of the macula by refraction at the unaccommodated
and uncorrected eye
What is the conoid of Sturm?
the area between the 2 focal points of a spherocylindric combination assumes a conoid shape
What is cycloplegic refraction?
An objective refraction being performed with the aid of a pharmaceutical agent designed
to prevent or reduce accommodation during refraction; wet refraction.
What is manifest refraction?
A refraction done without cycloplegic agents, dry refraction.
How many dots of light would a patient see with Worth’s 4 dot if there is Right eye suppression?
3 green lights
Assuming your working distance when doing retinoscopy is 66cm. What is the dioptric power of your working lens?
+1.50
Which eyedrop is used to constrict pupils?
Miotic
How do Antidepressants affect your pupils?
dilation
Patient prefers the letters on the red side means:
Patient prefers the letters on the green side means:
red - more minus power
green - more plus power
What does the scissor reflex indicate when performing retinscopy?
Corneal Irregularities
What is a good near point convergence result?
8-10cm
Where should corneal reflection be on a normal patient?
slightly nasal
Which category does a referral to doctor falls under in a patient;s chart?SOAP
Plan
When assessing the cylinder axis with astigmatic clock, where should you line the cylinder correction?
90 degrees away from the blackest line
During fogging, how much power are you adding on the fogged eye?
+1.00
If you cannot get your patient to see the letters on both red+green equally good, which side should you pick?
red
What is wet refraction?
Refraction with cycloplegia
If a patient fails Unilateral cover test, what does that indicate?
Strabismus tropia
How long should you cover one eye before uncovering during Unilateral cover test?
1-2 seconds
If you see against motion with retinoscopy, you should add minus. T/F
TRUE
Jackson Cross Cylinder only allows you to refine the patient’s cylinder axis. T/F
FALSE - can do power and axis
What is the last step in automated refraction?
Binocular balancing
What is the standard near vision distant?
14-16 inches
