refraction

1. Rajeshwori Ngakhushi

2.  retinoscope is actually an outgrowth of
the ophthalmoscope
 William Bowman(1861) noted the
changes in light and shadow that
occurred within the pupillary border
when he tilted his ophthalmoscope.

3.  early 1900s, various investigators began
utilizing the retinoscope to determine
the amplitude or status of
accommodation in non-verbal patients -
term dynamic retinoscope emerged
 Objective method of determining a
patient’s refractive error at nearpoint

4.  A.J. Cross is credited with
introducing the basic theory
and method for dynamic
retinoscopy
 Sheard, Nott, and Skeffington -
elaborated on the theory and
procedure

5. Goals
 to determine accommodative Response
 also helped determine the most
appropriate near prescription with
testing conditions
 Reveals the degree to which
accommodation is fluctuating when
attending to a near target & if the eyes
are balanced equally at near

6.  provide the information and insights
regarding the patient’s abilities and
level of visual processing at the
chosen distance

7. THE CROSS METHOD
 Andrew J. Cross( 1920)
 an alternative to cycloplegic refraction
 Method of adding plus lens power to
obtain a reversal

8.  Determining the correction in cases of
○Astigmatism
○Presbyopia
○Subnormal accommodation in
young patients

9. limitation
 A measurement of negative relative
accommodation
 Plus power recommended – patient
would not persist

10. SHEARDS’S METHOD
 Charles Sheard (1920)
 Introduced the concept of “ Lag
of accommodation”
 add plus lens power until
neutrality occurred

11. TAIT’S METHOD
 Tait(1953)
 Working distance = 33cm
 Fogging with a considerable amount
of plus lens power and then
approaches neutral by reducing the
plus lens power

12.  Found an average of approximately
+1.50 D more than sheard system ,
thus total lag of accommodation =
+2.25 D
 Close to +2.50D i.e Negative relative
accommodation.

13. LOW NEUTRAL AND HIGH NEUTRAL
METHODS
 Sheard ( low neutral method)
The end point is the least plus power
required for a neutral reflex to be
observed.
 Cross ( high neutral method)
Addition of plus power beyond neutrality
until a reversal occurs.

14. Monocular Estimate Method
(MEM) Retinoscopy
 attributed to Dr. Harold Haynes at the
Pacific University College of Optometry
 gives an estimated measure of the spatial
positioning of accommodation with
regard to convergence
 cognitive demand is moderate

15. Materials
 series of cards with a central
aperture mounted on a retinoscope
 cards can have printed letters, or words,
or pictures that range in size from 20/160
(6/120) to 20/30 (6/9)
 Arranged around the aperture

17. Procedure
 instructed to keep the targets clear
 sweeps the retinoscope beam
 observes the motion of the retinoscopic
reflex
 quickly interposes a trial lens at the
spectacle plane

18. Interpretation
 “lag of accommodation” is the amount
of plus lens that neutralizes the reflex
 has been found to accurately
measure the lag of accommodation
in an objective manner

19. limitation
 Plus lenses – relaxation of
accommodation – accommodative
response measured by this value found
to be 10% less
 No longer than one fifth of a second

20. Nott Dynamic
Retinoscopy
 developed by I. S. Nott in the 1920s
 main purpose is identical to the MEM
method
 cognitive demand is moderate

21. Materials
 reduced block of 20/20 (6/6) letters is
placed at 16 inches (40 cm) from the
patient

22. Procedure
 wears his compensating distance
lenses
 Directed to read the letters
 Performs retinoscopy by moving
farther from the plane of regard until
the motion is neutralized

24. Interpretation
 dioptric difference between these two
distances equals the lag of
accommodation
 can be valuable in evaluating the
stability of the accommodative
response

25.  Distance from the target to spectacle
plane = 40cm
 Distance from retinoscope to
spectacle plane = 50 cm
 Lag of accommodation
= 2.50D – 2.00D
= 0.50D

26. Bell Retinoscopy
 Developed by Drs. W.R. Henry and
R.J. Appel
 Evaluate the performance of the
accommodative system under moving
& real life conditions in free space
 cognitive demand is low

27. Materials
 Three dimensional viewing target
 a small, highly reflective bell dangling
from String – replaced with a Wolff
Wand(½ inch diameter, metal ball
mounted on the end of a rod)

28. Procedure
 wand is held by the
examiner
 moved closer to and
farther from the patient
- slower than 2
inches/sec

29.  retinoscope is positioned at a fixed
distance of 50 cm (20 inches)
 patient fixates the target and the
examiner notes the direction of the
reflex

30.  target is moved closer to the patient
there will be a point where the motion
changes from “with” to“against’’
 Target is again moved away from patient
until with motion is observed

31. Interpretation
 Distance between the retinoscope
and the target when the motion
change occurs is a physical measure
of the lag of accommodation
 “with” to “against” motion is observed
at 35 – 42 cm (14 - 17 inches)

32.  “against” to “with” at 37 - 45 cm. (15
-18inches)
 accommodative flexibility can be
assessed by observing how quickly or
sluggishly the reflex changes

33.  eye movement control can be assessed
by judging the extent to which the ball
can be fixated
 NPC can be determined by the normal
means

34.  eye-hand coordination can be evaluated
by asking the patient to touch the Wolff
Ball during the procedure
limitation
 patient converges - scoping more off-
axis

35. Stress Point Retinoscopy
 developed by Harmon and Kraskin
 evaluate the response of the entire
organism to stress
 in stress-point retnoscopy - looking at
the change in reflex quality

36.  Cognitive demand is moderate to
high
 reasoning behind stress-point
retinoscopy is that vision is intimately
related to the whole body and that a
physiological change in stress
occurring in the body can be
perceived through a change in the
retinal reflex

37.  Three things occur when near-point
stress is experienced
 Firstly - there is a change in the
individual's pulse
 Secondly - there is an inner canthal
twitch and
 lastly - change in the colour of the
retinal reflex is observed

38. Procedure
 Wolff ball is moved closer to the patient
- looks at which distance the reflex
"pops"
 initially brightened and then became dull
and finally brightened again - termed
"popping" of the reflex - about 4 inches
in front of the patient

39.  distance is noted and then different
lenses are placed binocularly and the
procedure is repeated
 ideal lens is the one which makes the
stress point as close to the subject as
possible

40.  more desirable to have the stress-point
closer to the patient - they are not
working under physiological stress
 For example; if the stress-point of a
subject is 40cm and they habitually read
at 30cm they would be under constant
near-point stress

41.  plus lenses move the stress-point closer
to the subject and minus lenses move it
away
 in children the stress-point should be
10cm closer to the subject than the
Harmon distance

42.  In adults the stresspoint should be 20 to
22.5cm from the face
 remote position of the stress point
indicates near point dysfunction

43. Book (Getman)
Retinoscopy
 developed at the Gesell Institute of
Child Development at Yale University
 developed to obtain information about
the visual processing of nonverbal
infants
 cognitive demand is high

44. Procedure
 patient is given reading material
 Retinoscope is performed as the
subject reads aloud
 information is gathered in real time
with a task that is close to their
normal work situation

45.  Getman and Kephart described the
following response levels with this
technique
A. Free reading level: Desirable, reflex
varies from neutral to with
B. Instructional level: more
demanding than the free reading
level, reflex is a varying fast against
motion

46.  C. Frustration level: Even though
the subject is “focused” on the page
he is not Interpreting the information
properly
slow against motion
 reflex color is bright and white when
the words are understood

47.  reflex color is more pink and dims
slightly if the patient is struggling to
comprehend a word or passage
 reflex color is dull and brick colored
when the patient has given up on
comprehending a word or reading
passage

48. Lag of accommodation
 Accommodative lag =
accommodative demand ( +2.50D at
40 cm) – accommodative response
 Lags are greater when closer test
distances are used

49.  Lag of accommodation exhibits a
slow but progressive increase to adult
levels
 Binocular accommodative system
normally respond with only +1.75D to
+2.00D of increased plus power

50. Lag of Accommodation
 Normal Lag: +0.50 or +0.75 diopters
 High Lag: +1.00 diopters or higher
 Lead : +0.25 diopters or less
50

51. Mean lags of
accommodation
 In various studies has varied from
about 0.25 to 0.75 D for the typical
test distance of 40cm

52. Rouse et al mean MEM lag of 0.34 D
Jackson and
Goss
Mean MEM lag of 0.23D
Tassinari Mean MEM lag of 0.35 D
Penisten et al a mean MEM lag of 0.77D

53.  Average latency for an
accommodative response is
370msec
 average total response time including
the latency and change in crystalline
lens power is about one second

54.  mean difference between MEM and
Nott was 0.0002D (SD = 0.28)
 Lags measured with Nott were lower
than the lags found with MEM in high
lag subjects

55. Lag > +0.75D/ High Lag
 Inadequate accommodative response:-
 as a result of :- near esophoria
poor negative vergences
accommodative insufficiency
uncorrected hyperopia
Patient is Overminused

56. Lag of accommodation <
+0.50D
 Overaccommodating
 As aresult of :- near exophoria
spasm of accommodation
Over Plus Correction
inadequate positive vergences

57.  Pilar Cacho et al reported that the
Nott method was a more appropriate
technique to assess lags of
accommodation in young adults
because it is the method that least
contaminates the results

58. Other methods
 Binocular cross cylinder
test
 Near duchrome test
Subjective methods

59. Accuracy of Dynamic
Retinoscopy
 When compared with the near bichrome
test and the near cross cylinder test,
dynamic retinoscopy gave the best
agreement for the accommodative
response as measured with an infrared
autorefractor.
59

61. Near retinoscopy and
dynamic retinoscopy
 Mohindra retinoscopy
 Fellow eye is patched
 Performs at near on infants
 Objective – measure refractive
condition at distance
 Correction factor is subtracted from
the neutralizing lens

62. Radical retinoscopy and
dynamic retinoscopy
 small pupil, cataract, or other media
opacity - observation of reflex is
difficult
 moves closer to patient
 WD – 20 cm

64. References
 Primary care of Optometry –
Theodore Grosvenor
 Optometry – Mark and Nicola
 Clinical refraction – Borish
 Previous presentations
 internet

65. THANK YOU !!!