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Questions and Answers
What is retinoscopy?
The use of a retinoscope to measure a patient's refractive error.
Which type of retinoscope produces a line or streak of light?
When using a retinoscope, what does the ret reflex look like?
Plus lenses neutralise an 'against' movement during retinoscopy.
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What type of lenses can you find in a trial lens set?
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How should the external surface of a retinoscope be cleaned?
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The brightness of the streak in a retinoscope should remain constant when the brightness control is turned.
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A trial lens set can include up to ____ lenses.
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What component is used to adjust the pupillary distance in a trial frame?
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Study Notes
Retinoscopy
- Purpose: To measure an eye's refractive error using a retinoscope.
- Objective method: Patients don't need to describe their vision, unlike subjective refraction methods.
- Retinoscopic Reflex: Red light reflected from the retina observed through the retinoscope.
- Movement: The ret reflex's movement indicates the refractive error.
- Trial Lenses: Used to measure the amount of movement, estimating accurate refractive errors.
Types of Retinoscopes
-
Streak retinoscope:
- Produces a line or 'streak' of light.
- Adjustable:
- Rotate the sleeve to change the axis position.
- Move the sleeve up/down to adjust the width of the streak.
- Change the light from convergent to divergent by moving the sleeve.
-
Spot Retinoscope:
- Produces a spot of light.
- Adjustable:
- Move the sleeve up/down to change the spot's size.
- Change the light from convergent to divergent by moving the sleeve.
- No need to rotate the spot for different axis directions.
Neutralising the Reflex
- Plus lenses: Neutralise a 'with' movement of the ret reflex.
- Minus lenses: Neutralise an 'against' movement of the ret reflex.
Trial Lens Set
- Purpose: To measure refractive errors.
-
Components: Can include up to 266 lenses:
- Spherical lenses: 0.12 D, 0.25 D, 0.50 D, 1.00 D in a range of positive and negative powers.
- Cylindrical lenses: Various powers, mostly in 0.25 D steps, including positive and negative values.
- Accessory lenses: Used for special tests, including prisms, filters, occluders, and pinhole lenses.
General Care
Retinoscope
- Cleaning: Wipe the external surface with a mild detergent solution, 70% isopropyl alcohol, or 10% bleach solution (consult manufacturer's manual).
- Note: Do not saturate the cleaning cloth, as liquid entering the retinoscope can damage internal components.
- Optical Surfaces: Avoid wiping the optical surfaces.
- Lens Cleaning: Wipe lenses with a dry lens-cleaning cloth.
-
Periodic Checks: Ensure the following functions correctly:
- Uniform brightness when turned on.
- Brightness control adjusts the streak's intensity.
- Sleeve slides freely, changing the streak's length.
- Streak rotates when the sleeve is turned.
Trial lens set
- Cleaning: Wipe lenses with a lens-cleaning cloth if stained or smudged.
- Storage: Keep lenses in the case after use.
- Cleaning: Wipe the trial frame's nose rest with an alcohol wipe after each patient.
Components
Retinoscope
- Head
- Neck
- Forehead rest
- Viewing hole/adjustable aperture
- Adjustable vergence sleeve
- Streak rotator
- Light brightness adjustment
- Peephole
- Concave effect
- Mirror
- Condensing lens
- Bulb
- Sleeve (bulb) down - plane effect
- Sleeve (bulb) up - converging effect
- Handle/battery compartment
Trial Frame
- Pupillary distance adjustment
- Side length adjustment
- Fore and aft adjustment
- Nose pad
- Lens cells
- Lens spring clips
- Side angle adjustment
- Cylinder axis adjustment
- Height adjustment
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