Retinoscope- Everything You Need to Know:

Retinoscopy vs Retinoscope

Refraction with Phoropter
Refraction with Phoropter

What is Retinoscopy:

  • Retinoscopy is a clinical procedure by which refractive error of eyes are identified objectively with the Retinoscope.

Retinoscope:

  • Retinoscope is an optical instrument used to estimate the refractive error of the eyes objectively.
  • Retinoscopy helps us to identify not only refractive error but also other ocular conditions. Like:
Ocular Media Opacities with Retinoscope
Ocular Media Opacities with Retinoscope

a. Media Opacities:

  • Corneal Opacity,
  • Vitreal Opacity,
  • Posterior Capsular Opacity (PCO)

b. Cataract:

  • Posterior Subcapsular Cataract (PSC)

c. Retinal Detachment (Rare):

  • Greyish Reflex.
New infeed Ad- mobile:

Principle of Retinoscope:

Principle of Streak Retinoscope
Principle of Streak Retinoscope

What is the Principle of Retinoscope?

  • Based on “Focault’s Principle” 
  • When light reflected from a mirror into the eye, the direction in which the light will travel across the pupillary area will depend upon the refractive state of the eye:

With movement:

  • Hypermetropia or Myopia less than Working Distance Power,

Against Movement:

  • Myopia.

Neutral:

  • Myopia (Equal to working Distance Power)

Same movement in both Meridian:

  • Emmetropia or Spherical Refractive Error.

Different Movement in Both Meridian:

  • Astigmatism.

Types of Retinoscope:

What are the types of Retinoscope?

1. Reflecting (mirror) retinoscopes:

  • Reflecting (mirror) retinoscopes are cheap and at one time were the most commonly employed.
  • However, presently these are rarely used.
  • A source of light is required when using mirror retinoscope, which is kept above and behind the head of the patient.

2. Self-illuminated retinoscopes:

  • Self-illuminated retinoscopes are costly but handy.
  • These have become more popular nowadays.
  • Two types of self-illuminated retinoscope available are:
  • A spot retinoscope.
  • A streak retinoscope.
  • The streak retinoscope is more popular, and most commonly used, as it is more sensitive than spot retinoscope in detecting astigmatism

Spot vs Streak Retinoscopy:

Spot vs Streak Retinoscope
Spot vs Streak Retinoscope

A. Spot self-illuminous retinoscope:

  • It provides a round shape illumination thus it’s called “Spot Retinoscope”
  • It consists of a bulb with a tiny, wired filament about 1-2 mm in size.
  • This is imaged by a convex lens of about 20 mm focal length to give a beam of light which is reflected by a mirror at 45°.

B. Streak Retinoscope:

  • In streak retinoscope the illumination is provided by a special bulb that has a straight filament, thus forming a ‘streak’ in its projection.

Note: In clinical Practice we mostly use Streak Retinoscope.  So we will cover details about Streak Retinoscope here.

Parts of Streak Retinoscope:

What are the parts of a Streak Retinoscope?

Power switch: 

  • To turn the retinoscope on and off.
  • To control the brightness of the light.
Parts of Streak Retinoscope
Parts of Streak Retinoscope

Small globe (light bulb):

  • It provides the light.

Electrical supply:

  • Batteries (disposable or rechargeable) in the retinoscope handle.
  • A power cord to connect the retinoscope to the main electricity.

Mirror:

  • It reflects light from the globe into the person’s eye.

Retinoscope aperture (viewing hole):

  • It allows the ret reflex to be seen.

Retinoscope sleeve:

  • It rotates the axis of the retinoscope’s light and changes the light beam from divergent to convergent light. 
New infeed Ad- mobile:

Characteristics of Ret Reflex of Streak Retinoscope:

What are the Characteristics of Ret Reflex Seen through Streak Retinoscope:

1. Brightness:

  • Gets brighter as we get closer to the neutral point.

2. Direction of movement: 

a. With movement:

  • Hypermetropia or myopia less than working distance power,

b. Against movement:

  • Myopia more than working distance power.

c. Neutral:

  • Myopia (equal to working distance power)

3. Speed:

  • Becomes faster at closer to neutralization. 
Brightness of Ret Reflex of Streak Retinoscope
Brightness of Ret Reflex of Streak Retinoscope

4. Thickness: 

  • Becomes wider when getting closer to neutralization.

Working Distance & Working Distance Power:

What is Working Distance in Retinoscopy?

  • Distance from which retinoscopy is performed or the distance between the spectacle plane to retinoscopy.

What is Working Distance Power in Retinoscopy?

  • Power used to subtract the working distance is called Working Distance Power.

Why do we need to subtract the working distance:

  • We do retinoscopy to identify the power of the patient at the spectacle plane.
  • But the position of a retinoscopy is away from spectacle plane that is normally 67 CM away from spectacle plane.
  • That means we identify the power of that patient at 67 CM not in the spectacle plane due to which we got 1.5D more power during retinoscopy.
  • So, to identify the power that is required in spectacle plane we need to subtract the distance from retinoscopic value.

Leave a Reply

Study Optometry Smartly with Smart Optometry Academy

Features

Most Recent Posts

  • All Post
  • Abroad Entrance
  • Binocular Vision
  • Blog
  • Clinical Refraction
  • Contact Lens
  • Courses Overview
  • Dispensing Optics
  • Dubai Health Authority (DHA)
  • HAAD
  • Instrumentation
  • MCQs Tests
  • Ocular Diseases
  • Optometry Tests
    •   Back
    • Retinoscopy/Refraction

Optometry Notes & MCQs

Get well organized notes for all Optometry Subjects

Category

Smart Optometry Academy

Study Optometry Smartly with Smart Optometry Academy

© 2024 Samir Sutradhar