Abstract:
To develop a severity scale for DME derived from eyes enrolled in the ETDRS and based on stereo photographic gradings of degree of retinal thickening (RT) at the center of the macula (RT_CM) and area of RT within 1 disc diameter (DD) of center (RT_1DD).
Mean baseline visual acuity (VA) scores were tabulated for eyes cross–classified by RT_CM and RT_1DD. Groups with similar VA scores were combined using cluster analysis and clinical judgment, producing an 8–step scale.
See table below. Mean VA Score at Baseline
Note: (1) all eyes with RT_1DD <0.5DA and any degree of RT_CM
>0 have similar VA; (2) eyes with the same degree of RT_CM
have decreasing VA as RT_1DD increases; (3) the cells combined
to form steps 5, 6, 7 and 8a are diagonal pairs, as might be
expected when two additive risk factors are cross classified.
The scale facilitates concurrent tracking of changes in morphology
and VA. For example, among 438 eyes assigned to deferral of
photocoagulation and in step 3 at baseline, 320 (73%) were in
step 3 or lower at 3 years and 8% of these eyes had moderate
(≥15 letter) VA loss (MVL), while of the 33 eyes (8%) that had
worsened to step 7 or 8 at 3 years 33% had MVL. Among 232 eyes
in step 8 at baseline, the 1/3 that improved to step 3 or better
at 3 years had a 22% MVL rate, while the 1/3 that remained in
steps 7 or 8 had a 63% MVL rate.<BR The scale
facilitates concurrent analyses of change in DME morphology
and VA. It may be useful in further analyses of ETDRS data and
in planning clinical trials.