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Baghdad University College of Medicine Ophthalmology Department

This document from Baghdad University's College of Medicine Ophthalmology Department discusses refraction, which measures refractive errors like myopia and hyperopia. It defines objective refraction techniques like retinoscopy, which uses light behavior to determine refractive errors, and autorefraction, while subjective refraction refines these results by having patients view lenses. The document also describes how to perform and interpret retinoscopy tests to diagnose refractive errors and astigmatism.

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Mariam Qais
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249 views20 pages

Baghdad University College of Medicine Ophthalmology Department

This document from Baghdad University's College of Medicine Ophthalmology Department discusses refraction, which measures refractive errors like myopia and hyperopia. It defines objective refraction techniques like retinoscopy, which uses light behavior to determine refractive errors, and autorefraction, while subjective refraction refines these results by having patients view lenses. The document also describes how to perform and interpret retinoscopy tests to diagnose refractive errors and astigmatism.

Uploaded by

Mariam Qais
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Baghdad University

College of Medicine
Ophthalmology Department
Objectives

By the end of this session the students will be able to:
 Define refraction and describe the tools for measure
it
 Describe objective and subjective refraction
 Observe and imitate refraction by retinoscopy and
autorefractor in ophthalmology department
Definition

Refraction is the process by which refractive errors are
measured.
It is used to determine the presence and degree of
myopia, hypermetropia and astigmatism.
Types of refraction

1- Objective refraction, the patient is not required to
speak, ideal for children.
2- Subjective refraction, in which patient contribution is
required, its usually used to refine and fine tune
objective refraction.
Objective refraction

 1-By retinoscop: it is a very sensitive tool in the hand
of the experienced practitioner, however it`s hard to
master and is time consuming.
Retinoscopy

 Uses a beam of light directed on the patient retina
and looking for the behavior of the red reflex while
moving the retinoscope along the pupil.
 Three reflex patterns:
 The reflex moves with the direction of the
retinoscope ,we add +ve lenses until it is neutralized.
 The reflex moves against the direction of the
retinoscope, we add –ve lenses until it is neutralized.
Retinoscopy(cont.)

 The reflex is neutral and fills the pupil.
Retinoscopy(cont.)

 Shape of the reflex:
Retinoscopy(cont.)

3 basic reflex patterns:
With movement

 Emmetropia
 Hypermetropia
 Myopia < working distance

e.g. the patient has a with movement reflex on retinoscopy and was
neutralized with +0.5 D sphere lens and the working distance was 1 metre.
Substract the working the distance from the lens resulting in -0.5 D sphere
refraction i.e myopia
If with movement reflex is neutralized with +1.0 D sphere lens and the
working distance was 1 metre then the resulting refraction will be
emmetropia +1-1=0
Against movement

Myopia>
working
distance
Retinoscopy(cont.)

 After determining the type of refractive error the
examiner will place plus or minus lenses in front of
the eye of the patient until the reflex is neutralized.
 We still have to subtract the working distance and
here is why:
Retinoscopy(cont.)

The patient should look at the chart and be instructed not to look at the
light of the retinoscope to abolish accommodation. If we use cycloplegic
eye drops no need to look far away.
Retinoscopy(cont.)

 Astigmatism can also be measured by this technique,
using the same principle buy moving the light in the
desired meridians.
Auto refractometer

 This device compensates for the lack of experience of
young practitioners, how ever it is less acurate.
Subjective refraction

 It is used to perfect the results of retinoscopy.
 Lenses are placed in special glasses frame called a
phoropter while the patient is being examined for
VA.
Subjective refraction

Subjective refraction

Phoropter


Retinoscopy simulator

https://www.eyedocs.co.uk/ophthalmology-
articles/optics-refraction/1508-retinoscopy-
simulator

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