Retinoscopy is a valuable tool for eye doctors to diagnose and manage refractive errors and other eye conditions. It is a safe, non-invasive, and relatively quick procedure that provides important information about the health of the eye. If you have any concerns about your vision, be sure to consult with an eye doctor who can perform a retinoscopy exam and provide the appropriate treatment.

1. Prepared by: Qurat-ul-Ain
RETINOSCOPY
Theory and Calculations
By Qurat-ul-Ain

2. Prepared by: Qurat-ul-Ain
Preamble
• What is retinoscopy?
• What are the types of retinoscopy?
• What is the principle of retinoscopy?
• How we perform retinoscopy?
• What are the techniques to perform retinoscopy?
• What is working distance and how we calculate it?
• How to do calculation to find accurate spectacle numbers?

3. Prepared by: Qurat-ul-Ain
Retinoscopy
• It is a technique to objectively determine the refractive state of the
eye and need for glasses.
• There are two types of retinoscopy:
1. Reflecting mirror (plane mirror, Priestley-smith’s)
2. Self-illuminating (spot, streak)

4. Prepared by: Qurat-ul-Ain
Streak Retinoscopy
Projecting System
• To illuminates the retina, it
consists of:
1. Light source
2. Condensing lens (a pair of
convex lenses)
3. Plane mirror (diverging effect)
or Concave mirror ( converging
effect)
4. Focusing sleeve
5. Current source
Observation System
• To allow the observer to see the
retinal reflex of the patient.

5. Prepared by: Qurat-ul-Ain
Projecting System
• Copeland
1. Sleeve up/bulb up  Plane mirror
effect
2. Sleeve down/bulb down 
Concave mirror effect
3. Lens is fixed and Bulb is mobile.
• Welch Allyn
1. Sleeve up/ Lens up  Concave
mirror effect
2. Sleeve down/ Lens down  Plane
mirror effect
3. Lens is mobile and Bulb is fixed.

6. Prepared by: Qurat-ul-Ain
Principle of retinoscope
• Retinoscope works on the Focault’s principle, where a knife edge
(peephole of retinoscope)place on the principle axis of an optical
system (patient eye reflex), intercepts a bundle of rays coming out of
the patient’s eye. Depending on the position of the peephole of the
retinoscope, various distributions of reflex can be observed in the
reflex of the patient’s eye.
• In retinoscopy we find the lens that places the “far point” at infinity.

7. Prepared by: Qurat-ul-Ain
Stages of Retinoscopy
Illumination stage  Light is directed into the patient’s eye to
illuminate the retina.
Reflex stage  the image of the illuminated retina is formed at the
patient’s far point.
Projection stage  the image at the far point is located by moving the
illumination across the fundus and noting the behavior of the
luminous reflex seen by the observer in the patient’s pupil.

8. Prepared by: Qurat-ul-Ain
How we perform retinoscopy?
• The target given to the patient should be 20/200 or 6/60 in Snellen
chart to relax accommodation during retinoscopy.
• Working distance (W.D) should be maintained at arm’s length
(66cm/50cm)
• The examiner should stay as close to the visual axis as possible but
avoid to obstruct the patient’s view to a target.
• Examine four primary meridians: 90, 180, 45, 135

9. Prepared by: Qurat-ul-Ain
• Three possible reflex may be observed:
1. With motion = the patient is hyperopic, emmetropia or myopic
less than the dioptric value of working distance.
2. Against motion = patient’s myopia is greater than the dioptric
value of working distance.
3. Neutrality = patient’s myopia is equivalent to the dioptric value of
working distance.

10. Prepared by: Qurat-ul-Ain
Working distance
• The distance between the patient’s eye and the observer while
performing retinoscopy is called working distance.
• Normally 66cm = 1.50D and 50cm = 2.00D
• Some clinicians use working distance lens (WDL) to compensate the
working distance and get instant identification of myopia, hyperopia
and astigmatism.

11. Prepared by: Qurat-ul-Ain
Calculation Rules
• Take the smallest number as a sphere between positive numbers
e.g., +2.00 and +3.00. In this case take +2.00 as a spherical to deduct
working distance.
• Take largest number in different sign conventions, for e.g., -5.00 and
+3.00. In this case take +3.00 as a spherical to deduct working
distance.
• Again take largest number as a sphere in negative numbers, for e.g.,
-5.00 and -3.00. In this case take -3.00 as a spherical to deduct
working distance.

12. Prepared by: Qurat-ul-Ain
• Add working distance algebraically.
• Note that working distance is always present with minus (-) sign,
e.g., -1.50, -2.00
• The difference between the two number of retinoscopy gives
cylindrical value.
• Choose the axis of a spherical reading.
• Sign of the cylindrical number is according to the movement from
spherical number to the other number.

13. Prepared by: Qurat-ul-Ain
Characteristics of a moving reflex:
• Speed
Slow moving  large refractive error
Fast moving  Small refractive error
• Brilliance
Dull reflex  large errors
Bright reflex  small errors
• Width
Narrow  away from neutral
Broad  approach the neutrality

14. Prepared by: Qurat-ul-Ain
+2.50
-1.00
W.D = 66cm = 1.50D
+2.50 + (-1.50)
+2.50 – 1.50
+1.00 DS
Final prescription:
+1.00DS/ -3.50  90
-5.00 -3.00
120 30
W.D = 66cm = 1.50D
-3.00 + (-1.50)
-3.00 – 1.50
-4.50 DS
Final prescription:
-4.50 DS/ -2.00  120
PRACTICE

15. Prepared by: Qurat-ul-Ain
-2.00 +2.00
110 20
+1.00 -1.00
130 40
W.D = 66cm = 1.50D
+1.00 + (-1.50)
+1.00 – 1.50
-0.50 DS
Final prescription:
-0.50DS/ -2.00  40
W.D = 66cm = 1.50D
+2.00 + (-1.50)
+2.00 – 1.50
+0.50 DS
Final prescription:
+0.50DS/ -4.00  110

16. Prepared by: Qurat-ul-Ain
-0.50 +2.50
130 40
-6.00 +3.00
140 50
W.D = 66cm = 1.50D
+3.00 + (-1.50)
+3.00 – 1.50
+1.50 DS
Final prescription:
+1.50DS/ -9.00  140
W.D = 66cm = 1.50D
+2.50 + (-1.50)
+2.50 – 1.50
+1.00 DS
Final prescription:
+1.00DS/ -3.00  130

17. Prepared by: Qurat-ul-Ain
+0.50 -1.00
145 55
-3.50 -2.50
170 80
W.D = 66cm = 1.50D
-2.50 + (-1.50)
-2.50 – 1.50
-4.00 DS
Final prescription:
-4.00DS/ -1.00  170
W.D = 66cm = 1.50D
+0.50 + (-1.50)
+0.50 – 1.50
-1.00 DS
Final prescription:
-1.00DS/ -1.50  55

18. Prepared by: Qurat-ul-Ain
0.00 -1.50
120 30
W.D = 66cm = 1.50D
0.00 + (-1.50)
0.00 – 1.50
-1.50 DS
Final prescription:
-1.50DS/ -1.50  30
W.D = 66cm = 1.50D
+1.50 + (-1.50)
+1.50 – 1.50
0.00
Final prescription:
0.00DS/ -3.00  90
+1.50
-1.50

19. Prepared by: Qurat-ul-Ain
-0.50 +0.50
125 35
0.00 +0.50
130 40
W.D = 66cm = 1.50D
+0.50 + (-1.50)
+0.50 – 1.50
-1.00 DS
Final prescription:
-1.00DS/ +0.50  130
W.D = 66cm = 1.50D
+0.50 + (-1.50)
+0.50 – 1.50
-1.00 DS
Final prescription:
-1.00DS/ -1.00  125

20. Prepared by: Qurat-ul-Ain
-2.00 +2.00
150 60
W.D = 66cm = 1.50D
+2.00 + (-1.50)
+2.00 – 1.50
+0.50 DS
Final prescription:
+0.50DS/ -4.00  150
W.D = 66cm = 1.50D
0.00 + (-1.50)
0.00 – 1.50
-1.50
Final prescription:
-1.50DS
0.00
0.00

21. Prepared by: Qurat-ul-Ain
-2.00 +2.00
150 60
W.D = 66cm = 1.50D
+2.00 + (-1.50)
+2.00 – 1.50
+0.50 DS
Final prescription:
+0.50DS/ -4.00  150
W.D = 66cm = 1.50D
+1.50 + (-1.50)
+1.50 – 1.50
0.00
Final prescription:
Nil
(no need of glasses)
+1.50
+1.50

22. Prepared by: Qurat-ul-Ain