Diabetic Macular Edema: What is Focal and What is Diffuse

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Diabetic Macular Edema What is Focal and What is
Diffuse?

• Sponsored by the National Eye Institute,
• National Institutes of Health, U.S. Department of
  Health and Human Services.

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Intravitreal Triamcinolone vs. Laser for DME

• Participants
• Center involved DME (CST 250 um)
• Primary Outcome
• Laser treated eyes had greater VA outcomes
• Secondary Outcome
• CST paralleled VA results

Ophthalmology 2008 Sep115(9)1447-1459.e10
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Does the treatment intervention have the same
response across subgroups?
Focal DME

• Secondary analysis subgroup participants into
  categories that may have different natural course
• Focal vs. Diffuse DME

Diffuse DME
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Why Bother with Focal and Diffuse Diabetic
Macular Edema?

• Background
• Focal edema responds BEST to laser
• Diffuse edema has WORSE natural course
• Diffuse edema responds BEST to steroids
• Do we know what Focal or Diffuse DME is???

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DRCR.net Perspective on Focal vs. Diffuse DME Am
J Ophthalmol 2008146649-55

• Frequently used terms
• Attempt to differentiate 2 distinct types of DME,
  but

Do these terms have consistent definitions? NOT
REALLY!
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Multiple Sources of Confusion

• Many articles discuss Focal/Diffuse without
  providing any definition
• Many say Diffuse diffuse leakage Focal focal
  leakage
• Focal laser direct treatment of MAs
• Published definitions use 4 exam methods, singly
  or in combination
• Biomicroscopy, photos, FA, OCT

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Published Definitions Vary Widely in Specific
Criteria

• In general, definitions based on fundus photos
  mirror characteristics of definitions based on
  clinical exam alone

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Published Definitions Vary Widely in Specific
Criteria Exam/Photo

• Area component
• ? 2 DA retinal thickening diffuse
  (inconsistent cut points)
• Do we reliably quantitate area?
• Location component
• Foveal diffuse
• Require area location or only 1??
• Lipid
• Lipid focal
• Quantity (lots), Configuration (ring), or both

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Published Definitions Vary Widely in Specific
Criteria FA

• ETDRS classified proportion of FA leakage
  originating from MAs
• 67 leakage a/w MAs focal
• 33-66 intermediate
• lt33 leakage a/w MAs diffuse
• But, reproducibility of grading only fair since
  variable leakage patterns can occur within an eye
  and subjective assessment

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Published Definitions Focal vs. Diffuse Vary
Widely in Specific Criteria FA

• Area component
• No specified cut point/variation in cut point
• Location component
• Foveal or 4 quadrants
• Source of Leakage
• MAs imply focal
• Count total leakage sites
• Late leakage pattern
• CME implies diffuse

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Published Definitions Focal vs. Diffuse DME Vary
OCT

• Regional Map (low resolution)
• Line Scans (higher resolution)

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Published Definitions Focal vs. Diffuse DME Vary
OCT

• Regional Map (low resolution)
• False color map might be used to give a sense
  of focality
• Increased number of thickened subfields among
  the 9 subfields implies diffuse

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Published Definitions Focal vs. Diffuse DME Vary
OCT

• Regional Map (low resolution)
• False color map might be used to give a sense
  of focality
• Increased number of thickened subfields among
  the 9 subfields implies diffuse
• Line Scans (higher resolution)
• Thickened areas of lower reflectivity in outer
  retina without cysts implies diffuse
• Variable requirement for reduced reflectivity in
  inner retina too
• Others state cysts are present in most diffuse
  cases
• Concern OCT instrument technologic advancements
  will alter images and importance of any of these
  findings, e.g., no cystoid abnormalitiy on TD-OCT
  may have cystoid abnormality with SD-OCT

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How About Hybrid Definitions?

• Mix and match features from various exam methods
• No consensus
• Combine exam/FA
• Combine exam/FA/OCT

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Are Claims about Implications of Focal vs Diffuse
DME presently Substantiated?

• Probably not
• Claims do not originate from RCTs designed to
  answer this question
• ETDRS did not find beneficial effects of laser on
  avoidance of vision loss to be affected by source
  of FA leakage
• Claims based on qualitative cross study
  observations

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Focal and Diffuse DME Now What?

• Marked variation in defining entity
• Develop definitions that are
• Clinically applicable
• Reproducible
• Meaningful differentiate natural course or
  treatment response
• Work in progress test and report
• For now- be cautious when using focal/diffuse
  terms, provide clear definitions, and reognize
  concept MAY or MAY NOT be helpful in long run

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Thank You

• Clinical study sites working with the network
• Subjects who volunteer for our many trials
• The focal/diffuse working group within the network

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