Potential methods of refraction for rural areas in the developing world'

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Potential methods of refraction for rural areas
in the developing world. A S Carlson Andries J
Burger, Juliana Esterhuizen, Nadia P Herbst, C
Herman Smit. Irene de Lange, Michelle A S de
Oliveira, Lynette H de Smedt, Elzana Engelbrecht,
Denise M Meyer, Tanya Shephard, Marilé
Terreblanche, Sarel J van der Westhuizen. Optomet
ric Science Research Group, Department of
Optometry, University of Johannesburg, South
Africa. acarlson_at_uj..ac.za
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• Aim of study.
• To examine different functional methods of
  refraction in
• rural areas.
• 3 separate pilot studies with 2 different
  samples.
• One study compared duochrome measurements with
  stigmatized subjective refractions ( using the
  Adspec)
• The other using Scheiners disc for measurements
  with stigmatized subjective refraction (using the
  Adspec)
• The other compared Focometer and Adspec
  measurements with subjective refraction
  (Astigmatic measurements using the Adspec and
  Focometer)

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Duochrome
Scheinerdisk
Stigmatic refractions
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Sunburst dial
90
60
120
30
150
180
0
330
210
240
300
270
Astigmatic refractions
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• Method
• For the duochrome and Scheiners Disk study,
  measurements were taken from 50 right eyes of
  subjects.
• Ages ranged between 19 and 28 years.
• 45 females and 5 males (Scheiners disc)
• 37 females and 13 males (Duochrome)
• Uncompensated and compensated VAs were measured
  in Snellen acuity and then converted to decimals.
• All subjective refractions were converted to
  NES
• For the Focometer and Adspec study, measurements
  were taken from 40 left eyes of subjects.
• Ages ranging from 18 to 30 years
• 32 Females and 8 males
• Uncompensated and compensated VAs were measured
  in Snellen acuity and then converted to decimals.
• All prescriptions remained in Sph Cyl axis

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Results(Stigmatic)Scheiners
discandDuochrome
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Visual acuity
frequency
frequency
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Visual acuity
Visual acuity
frequency
frequency
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• Scheiners disk
• Reduction in VA (9)
• 5 from 1 to 0.8
• 1 from 1 to 0.5
• 1 from 1 to 0.6
• 1 from 0.8 to 0.67
• 1 from 0.67 to 0.5
• Unchanged (22)
• 20 _at_ 1. (6/6)
• 2 _at_ (0.8)
• Improvements (19)
• 0.1 to 1 (3)
• 0.1 to 0.67 (1)
• 0.1 to 0.5 (1)
• 0.16 to 0.8 (2)
• 0.25 to 0.3 (1)
• 0.67 to 0.8 (1)
• 0.3 to 0.5 (1)

• Duochrome
• Reduction in VA (3)
• 2 from 1 to 0.8
• 1 from to 1 to 0.2
• Unchanged (23)
• 23 _at_ 1. (6/6)
• Improvements (24)
• 0.1 to 1 (6)
• 0.1 to 0.8 (1)
• 0.1 to 0.7 (1)
• 0.2 to 1 (1)
• 0.2 to 0.8 (1)
• 0.3 to 1 (2)
• 0.5 to 0.7 (1)
• 0.5 to 1 (3)

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Duochrome
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• Results.
• Scheiners disc
• Difference in means 0.0075
• Standard deviation 0.78 D
• Hypothesis test using Student t-test
• Dont reject
• Duochrome.
• Difference in means 0.63D
• Standard deviation 1.17 D
  
  Hypothesis
  test using the Student t- test
• Reject

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Results (Astigmatic) Focometer and
Adspecs
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Uncompensated
Visual acuity
Frequency
Frequency
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Uncompensated
Visual acuity
Frequency
Frequency
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Focometer Reduction ( 3)
1 from 1 to 0.5, 1 from 0.8 to 0.5 1 from0.4 to
0.12 No change (12) 11 _at_ 1.0 (6//6) 1 same at
0.8 Improvements (25). 5 from 0.05 to 1, 4 from
0.1 to 1, 1 from 0.125 to 1 1 from 0.16 to 1 1
from 0.2 to 1, 2 from 0.8 to 1 1 from 09 to 1.
1 from 0.125 to 0.8 1 from 0.32 to 0.8 2 from
0.05 to 0.8. 1 from 0.05 to 0.67, 2 from 0.1 to
0.67, 2 from 0.125 to 0.4
Adspec Reduction (4) From 1.0 to
0.5 No change (5) 6 _at_ 1.0 1 _at_ 0.8 Improvement
(31) 20 improved to 1.0 4 improved to 0.8 3
improved to 0.67 3 improved to 0.5 1 improved to
0.4 1 improved from 0.05 to 0.125
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Results

• Clinical mean of measurements
• 
  
• Subjective refraction -1.70 / - 0.11 x 118
• Adspec - 1.33 / - 0.20 x
  122
• ( Adspec - Subjective) 0.38 / - 0.10 x 125
• Focometer - 1.55 / - 0.12 x
  78
• (Foc - Subjective) 0.23 / - 0.15 x
  55
• Hypothesis test on the mean difference using
  Student-t test shows
• Adspecs Reject
• Focometer Dont reject

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Discussion

• Both instruments overplussed the stigmatic
  component.
• We could compensate by adding -0.25 D to Adspec
  measurements.
• Maybe the subjective refraction was suspect (more
  negative)
• Maybe the instructions need to be explained more
  clearly.
• Further studies with larger samples be
  undertaken.

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Finis
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