Comparison of Modified ETDRS and Mild Macular Grid Laser Photocoagulation Strategies for Diabetic Macular Edema

1

• Comparison of Modified ETDRS and Mild Macular
  Grid Laser Photocoagulation Strategies for
  Diabetic Macular Edema
• Sponsored by the National Eye Institute,
• National Institutes of Health, U.S. Department of
  Health and Human Services

2
Objective

• Compare two laser photocoagulation techniques
• Modified ETDRS focal photocoagulation (mETDRS) to
  areas of edema
• Direct treatment to microaneurysms
• Grid to diffuse leakage
• Mild macular grid (MMG) laser technique
• small mild burns throughout macula
• in areas with and without edema
• no direct treatment of microaneurysms

3
Background

• Presumed mechanism of focal photocoagulation
  include
• Closure of microaneurysms
• Reduced blood flow leading to auto-regulation and
  reduced edema
• Improved oxygenation leading to auto-regulation
  and reduced edema
• Stimulation of biochemical processes in RPE
• Would light widespread laser (mild macular grid,
  MMG) to the macula be effective?
• Pilot clinical trial

4
Study Design
Randomized Clinical Trial (Pilot Study)

• Major Eligibility Criteria Assessed
• gt18 years old
• Type 1 or type 2 diabetes
• Study eye meets the following criteria (subjects
  allowed 2 study eyes)
• Best corrected electronic ETDRS visual acuity
  score of 19
• Definite retinal thickening on clinical exam due
  to previously untreated DME
• Retinal thickness measured on OCT of 250 µm or
  more in the central subfield or 300 µm or more in
  at least 1 of the 4 inner subfields
• Had no prior laser or other treatment for DME.

• Subjects with 2 study eyes 1 eye was randomly
  assigned to receive 1 treatment and 1 eye was
  assigned to receive the other.

mETDRS N162 Eyes
MMG N161
5
Mild Macular Grid
40 minutes post laser treatment
6 weeks post laser treatment
6
Follow-up and Treatment Schedule

• Measurements by certified Evaluator
• Best-corrected electronic ETDRS visual acuity
• OCT-measured retinal thickness
• Macular laser photocoagulation was repeated if
  DME persisted and such treatment was warranted in
  the opinion of the investigator, according to the
  treatment guidelines.

3.5 Month 2 Weeks
. . .
8 Month 4 Weeks
. . .
Primary outcome Change in OCT Secondary
Outcome Change in visual acuity (Method
Repeated measures least squares regression models)
12 Month 4 Weeks
7
Baseline Demographics and Clinical Characteristics
Subject Characteristics mETDRS Group (N162 eyes) MMG Group (N161 eyes)
Gender Women - N() 38 43
Age (yrs) - MeanSD 5811 5911
Race - N()
White 63 64
African-American 18 19
Hispanic or Latino 10 8
Asian 5 4
Other 4 4
8
Baseline Demographics and Clinical Characteristics
mETDRS Group (N162 eyes) MMG Group (N161 eyes)
Diabetes Type - N()
Type 1 7 6
Type 2 93 94
Duration of Diabetes (years) - MeanSD 149 138
HbA1c () - MeanSD 8.21.9 8.22.1
9
Baseline Demographics and Clinical
Characteristics Cont.
Ocular Characteristics mETDRS Group (N162 eyes) MMG Group (N161 eyes)
E-ETDRS Visual Acuity (letter score) - N()
gt 84 20/20 or better 27 20
83-69 lt 20/20 to 20/40 47 57
68-49 lt 20/40 to 20/100 22 17
48-34 lt 20/100 to 20/200 4 4
33-19 lt 20/200-20/400 0 2
MeanSD - letters 7412 7314
10
Baseline Demographics and Clinical
Characteristics Cont.
OCT mETDRS Group (N162 eyes) MMG Group (N161 eyes)

Central Subfield Thickness (microns) MeanSD 335128 346118
Maximum retinal thickening of central and inner subfields (microns, see text) MeanSD 148122 163111
Number of eyes with at least 1 unthickened subfield - N() 60 55
11
Mean Central Subfield Thickness
12
Percent Edema Resolved for Central Subfield
Thickness
P0.56
P0.23
P0.29
13
Percent of Edema Resolved for Weighted Inner Zone
Thickness
P0.07
P0.02
P0.57
Note Weighted inner zone thickness is a weighted
average of the thickness in the central and 4
inner subfields
14
Percent of Edema Resolved for Maximum Retinal
Thickening
P0.93
P0.26
P0.57
Note Maximum thickening is the maximum amount of
excess thickness of the central and 4 inner
subfields
15
Percent of Edema Resolved for Retinal Volume
P0.01
P0.12
P0.31
Note Retinal volume is a weighted average of the
thickness in the central, 4 inner and 4 outer
subfields converted to mm3
16
Percent with 10 Letter Improvement in Visual
Acuity
17
Percent with 10 Letter Worsening in Visual
Acuity
18
Summary

• Maximum retinal thickening in the inner zone
  (within 1500 microns of macular center), central
  subfield thickness, weighted inner zone thickness
  and retinal volume decreased in both groups
• MMG less effective than mETDRS in reducing
  retinal thickening
• Visual acuity similar in both groups