retinoscopy 1,2&3 Flashcards
(23 cards)
the primary goal of retinoscopy?
The goal of retinoscopy is to estimate the refractive error of the eye by observing the movement of the light reflex in the pupil.
Why is retinoscopy important in optometry?
It is an objective method to estimate refractive error, especially in patients who cannot communicate well (e.g., children, illiterate patients, or uncooperative individuals).
It helps assess the clarity of the ocular media and provides a measure of accommodation.
What does the “retinoscopic reflex” look like?
The retinoscopic reflex is a red or orange color observed in the patient’s pupil, which moves depending on the refractive error.
What does the “with” and “against” movements of the reflex indicate?
A “with” movement indicates myopia, where the light rays are converging as they exit the patient’s eye.
An “against” movement indicates hyperopia, where the light rays are diverging as they exit the patient’s eye
What does neutralisation in retinoscopy mean?
: Neutralisation is achieved when the retinoscopic reflex shows no movement, meaning the far point of the patient’s eye coincides with the mirror of the retinoscope.
what lenses for “with” and “against” movements
The examiner should add a positive lens to neutralize the with movement.
The examiner should add a negative lens to neutralize the against movement.
What is the “reversal point” in retinoscopy?
The “reversal point” occurs when the reflex changes direction, which happens when the lens power is overcorrected by approximately +0.25D.
types of retinoscopes?
Spot Retinoscope: Provides a circular patch of light.
Streak Retinoscope: Provides a slit of light that can rotate around 360°.
What is the main difference between a divergent plane mirror and a convergent concave mirror in a retinoscope?
Divergent plane mirror creates divergent light rays, leading to the reflex moving in the opposite direction.
Convergent concave mirror creates convergent light rays, leading to the reflex moving in the same direction.
How does the far point plane (FPP) relate to retinoscopy?
The FPP is the point where the light from the patient’s retina focuses, and the examiner manipulates this plane to coincide with the retinoscope’s mirror to achieve neutralisation of the reflex.
How does cycloplegia affect retinoscopy results?
Cycloplegia (using drugs like cyclopentolate) relaxes the patient’s accommodation, revealing latent hyperopia that would otherwise be masked during normal retinoscopy.
What is the Mohindra technique in retinoscopy?
The Mohindra technique is a near retinoscopy method, often used for children, where the examiner works at a 50cm working distance and neutralises the reflex to estimate the refractive error.
What are the potential challenges when performing retinoscopy on patients with large pupils?
Large pupils can cause spherical aberration, leading to a with movement in the center of the pupil and an against movement at the periphery. The examiner should focus on the center of the pupil.
How can keratoconus affect the retinoscopy reflex?
In keratoconus, the cornea has an irregular shape, causing the reflex to appear distorted, such as swirling or split reflexes. The examiner should use a larger lens step and possibly increase the room light to reduce pupil size.
What is dynamic retinoscopy used for?
Dynamic retinoscopy is used to assess the accommodative state of the eye during near vision, helping to identify accommodative lag or excessive accommodation.
What is the process for performing retinoscopy in astigmatism?
Identify the principal meridians of the eye.
Neutralise the reflex in each meridian separately using spherical and cylindrical lenses.
Ensure that the axis of the cylinder is refined to the correct meridian.
How do you correct astigmatism during retinoscopy?
The spherical lenses are used to correct one meridian, and cylindrical lenses are added to correct the second meridian. If the cylinder axis is incorrect, the reflex will move in a different meridian, and the axis needs to be adjusted.
How can the bracketing technique be used in retinoscopy?
he bracketing technique involves adding high positive and negative lenses to refine the neutralisation point and accurately estimate the refractive error, especially when reflexes are far from neutral.
How do you handle working distance errors in retinoscopy?
The working distance needs to be corrected by using a working distance lens. The correction for working distance is calculated using the formula: F sp=F rev−W
F sp = spectacle lens power
F rev = reversal lens power
W = 1/working distance
(usually 1.5)
What does a “slow and dull” with movement reflex indicate in retinoscopy?
A “slow and dull” with movement reflex suggests that a high positive lens is required to neutralise the reflex.
What should be done when you observe no movement in the retinoscope reflex?
No movement means that the neutralization point has been reached. If the reflex is bright, the neutralisation is close, but if dull, the reflex is far from neutral.
In an exam, if you are performing retinoscopy and notice the reflex moves with and against at different meridians, what does this suggest?
This suggests the presence of astigmatism, and you should proceed to neutralise each meridian with the appropriate spherical and cylindrical lenses.
Which method of retinoscopy is used in children that cannot fixate distant target?
Mohindra Technique
