L5 Flashcards
(26 cards)
What is retinoscopy?
An objective method of determining the refractive error by analyzing the movement and shape of light reflected from the patient’s retina.
Why is retinoscopy important?
It is the main way of assessing refractive error in infants, small children, illiterates, uncooperative patients, and those with communication problems; it can also help assess the clarity of the ocular media.
What are the two basic methods of retinoscopy?
Static retinoscopy (accommodation controlled) and dynamic retinoscopy (accommodation active).
How is accommodation controlled during static retinoscopy?
By having the patient view a distant target (6 meters) or using cycloplegic drugs.
What are the four main components of a retinoscope?
A light source, a moveable condensing lens, a semi-silvered mirror, and a sighthole.
What are the two main types of retinoscopes?
Spot retinoscope (circular light patch) and streak retinoscope (slit of light, rotatable).
What is the function of the retinoscope collar?
Moving the collar changes the distance between the light source and lens, altering the beam to be convergent, divergent, or parallel.
What is the ‘plane mirror mode’ in retinoscopy?
Collar down, producing divergent rays.
What is the ‘concave mirror mode’ in retinoscopy?
Collar up, producing convergent rays.
What is the purpose of the sighthole in a retinoscope?
It allows the examiner to see the reflex in the patient’s pupil.
What is the principle of retinoscopy?
A cone of light is shone into the eye, creating a patch of light on the retina; the reflected light (reflex) is analyzed to determine the refractive error.
What is the far point of the eye?
The position of an object such that its image is focused on the retina when the eye is not accommodating.
Where is the far point in emmetropia?
At infinity.
Where is the far point in myopia?
A finite distance in front of the eye.
Where is the far point in hyperopia?
A virtual point behind the eye.
What is the facial light patch in retinoscopy?
Light falling on the outer parts of the eye, used as a reference for reflex movement.
How is reflex movement interpreted in myopia?
The reflex moves in the opposite direction to the facial light patch (‘against’ movement).
How is reflex movement interpreted in hyperopia?
The reflex moves in the same direction as the facial light patch (‘with’ movement).
What does ‘with’ movement indicate in retinoscopy?
‘With’ movement indicates hyperopia or low myopia.
What does ‘against’ movement indicate in retinoscopy?
‘Against’ movement indicates myopia.
What does ‘neutral’ mean in retinoscopy?
‘Neutral’ means the far point coincides with the retinoscope.
How is the far point manipulated during retinoscopy?
The far point is manipulated by adding trial lenses to create an artificial far point, or by varying the working distance.
How is accommodation controlled during retinoscopy?
By fogging the fixing eye with a plus lens to prevent accommodation.
What does a slow, dull, and small reflex indicate?
The reflex is far from neutral; a greater lens power is needed.
