CLINICAL TESTS - Optics ones Flashcards
What are the findings from the four worth dot test?
Red covers RIGHT EYE.
What are the 3 definitions of binocular vision?
- Simultaneous perception
- Fusion
- Stereopsis (perceive 3D)
What tests can be used to assess binocular vision?
- Worth 4 dot test / Bagolini glasses - Simultaneous perception and fusion
- Synoptophore
- Prisms - range of motor fusion
- Stereoacuity tests: Titmus, TNO, Lang, Frisby
What does the Maddox rod test?
Heterophories and heterotropias at near and far fixation distances.
Single maddox rod: horizontal and vertical
Double maddox rod: Torsional deviations?
What does the four diopter base out test measure?
Small central suppression scotoma / foveal suppression
Difference in minutes of arc between
Titmus
TNO
Lang
Frisby
Synoptophore
Frisby 15-600 seconds of arc
Titmus - 40-3000 seconds of arc
TNO: 15-480 seconds of arc
Lang: 550-1200 seconds of arc
Synoptophore: 90-720 seconds of arc
Lang and Frisby do not need glasses.
Frisby - FAST TO 600 miles.
TNO: Tigers Never
Titmus: Tigers Take Time (40-3000)
Lang: Leaps super high (550-1200)
Synoptophore: Sleek 90 and Perfect 720.
What does the Worth Four Dot test test for?
Binocular vision
1. Suppression
2. Anomalous Retinal Correspondence (ARC)
What does a keratometer measure?
Measures curvature of anterior surface of cornea, across a fixed chord length (2-3mm) which lies within optical spherical zone of the cornea.
Used for
1. Non conact tear break-up test
2. Differentiation of corneal astigmatism
3. Detection of irregular astigmatism
Whats the difference between a Bausch & Lomb Keratometer and a Javal & Schiotz Keratometer?
They are both manual keratometers 36-52D can be measured.
B&L : one position keratometer - both horizontal and vertical meridian measured by keeping keratometer in same position
J & S: two position keratometer: after measuring one meridian, need to change position to measure other meridian.
- has variable object size
- A wollaston prism is used to achieve doubling of the image.
When is an extended keratometer used?
Anything higher than 52D
–> +1.25D lens (equal to 9D) placed over eyepiece
Anything less than 36D
—> A -1.00 lens (equal to 6D) placed over eyepiece.
What can the synoptophore be used to measure?
All three grades of BSV
Grade 1: Simultaneous perception (red slides) –> can map suppression scotoma and angle of deviation objectively and subjectively
Grade 2: Fusion (Green) –> sensory and motor fusion
Grade 3: Stereopsis (yellow)
What are the findings of the synoptophore in normal retinal corespondence?
What are the findings of the synotophore in anomalous retinal correspondence?
Normal retinal correspondence: Objective angle = subjective angle of deviation.
Anomalous retinal correspondence: Objective angle not equal to subjective angle - the patient does not perceive true fovea as fovea, adn they are moving one of the images to the pseudofovea.
When ARC is detected, you can determine angle of anomaly, which is distance of pseudo-fovea from true fovea. Nasal + sign, Temporal - sign.
What is used to eliminate chromatic aberration in the focimeter?
Green light is used.
What does the four prism diopter base out test detect?
Small central suppression or foveal suppresion.
What is the normal scenario after a 4D BO prism is placed in front of the right eye?
What are the abnormal pathological findings?
Normal
1. Levoversion of right eye - rays deviate towards base, so right eye moves left to refixate on fovea - indicates absence of foveal suppresion of RIGHT eye.
- Initial levoversion of left eye - Hering’s law
- Subsequent refixation of left eye to the right to avoid diplopia –> Absence of foveal suppression of the LEFT eye.
Foveal suppresion of right eye: no movement of both eyes.
Foveal suppresion of left eye: Levoversion of right eye, levoversion of left eye but NO RE-FIXATION.
