Obtaining Good Quality Digital Images of the Retina

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Obtaining Good Quality Digital Images of the
Retina
1st Retinal Screen Limited

• A Guide for
• Diabetic Retinopathy Screeners

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• A national programme for diabetic retinopathy
  screening
• using digital fundus photography is being
  implemented
• under the auspices of the UKs National Screening
  
• Committee (NSC).
• NSC guidance includes detailed specifications on
  what constitutes a good image acceptable for
  diabetic retinopathy screening.
• The following presentation provides information
  on
• taking good retinal images and includes example
  images
• regarded as good, adequate or inadequate for
  screening
• purposes.

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National Screening Committee Guidance
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Definitions of Disc, Fovea and One Disc Diameter
1DD
The following image is a perfectly aligned
macular view of the right eye. The fovea lies at
the centre of the image and is marked by a
symbol.
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Definition of acceptable image qualityVersion 2,
Agreed by the National Screening Committee (NSC)
Grading and Quality Assurance Subcommittee, 9 May
2006

• Photographers should capture 2 x nominal 45º
  fields per eye (1 x fovea centred, 1 x disc
  centred).
• A combined assessment of field position and image
  quality should be made for each eye.
• Images must be utilised only if the grader is
  confident the quality is sufficient.
• All grading is to be performed by trained and
  accredited staff.

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A combined assessment of field position and image
quality is made in the software as follows
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Good Macula and Disc Images

• centre of fovea 1DD from centre of image
• vessels clearly visible within 1DD of centre of
  fovea
• vessels visible across gt90 of image

• centre of disc 1DD from centre of image
• fine vessels clearly visible on surface of disc
• vessels visible across gt90 of image

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Adequate Macula and Disc Images

• complete optic disc gt2DD from edge of image
• fine vessels visible on surface of disc

• centre of fovea gt2DD from edge of image
• vessels visible within 1DD of centre of fovea

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Inadequate (ungradable) Macula and Disc Images

• Failure to meet definition of adequate UNLESS
  referable diabetic retinopathy (R2, R3, M1,
  unstable treated proliferative diabetic
  retinopathy) visible anywhere in the eye

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Good Image Examples
Macula Centred View
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centre of fovea 1DD from centre of image
1 Disc Diameter
vessels clearly visible within 1DD of centre of
fovea and over 90 of the image
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Good Image Examples
Disc Centred View
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centre of disc 1DD from centre of image
1 Disc Diameter
fine vessels clearly visible on the optic disc
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Adequate Image Examples
Macula Centred View
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centre of fovea gt2DD from the edge of the image
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Adequate Image Examples
Disc Centred View
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complete optic disc gt2DD from the edge of the
image
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Inadequate Image Examples
Macula Centred View
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Centre of fovea lt 2DD from the edge of the image
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Vessels not visible within 1 DD of the fovea
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Centre of fovea lt 2DD from the edge of the image
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Vessels not visible within 1 DD of the fovea
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Image quality generally poor
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Inadequate Image Examples
Disc Centred View
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Vessels not visible on the optic disc
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Vessels not visible on the optic disc
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Complete optic disc lt 2DD from the edge of the
image
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Complete optic disc lt 2DD from the edge of the
image
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Image quality generally poor
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More Examples of Inadequate Images
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Too far in
Dirt on lens
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Too far out
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Too far out
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Pupil too small or not enough flash
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Cataract to dense
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Cataract too dense
Dirt on objective lens
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For more details on all aspects of the National
Programme for Diabetic Retinopathy Screening
visitwww.nscretinopathy.org.uk
1st Retinal Screen Limited