158 Calle Ignacio Carrera Pinto
01. Construcción de monolito
The ETDRS introduced the term clinically significant macular oedema (CSMO)(Box 2.3) [86]. The study demonstrated that macular laser treatment reduced the risk of moderate visual loss (defined as loss of ≥15 letters on the ETDRS chart, equivalent
Box 2.2 Severe non-proliferative diabetic retinopathy (NPDR) as defined in the Early Treatment of Diabetic Retinopathy Study (ETDRS) [86]
• Severe NPDR, any one of the following:
1. 4 quadrants of haemorrhages and microaneurysms (HMa) ≥ standard photograph 2A
2. 2 quadrants of venous changes ≥ standard photograph 6A 3. 1 quadrant of intraretinal microvascular abnormalities (IRMA) ≥
standard photograph 8A
29 to a doubling of the visual angle) by up to 50% in subjects with CSMO [15]. Macular laser reduced retinal thickening and was associated with an increase in moderate visual gain. On the basis of results from the ETDRS, CSMO is the accepted threshold for macular laser treatment. The ETDRS used clinical examination to grade CSMO in clinical sites but stereoscopic photographs can be used and formed the protocol for grading at the Wisconsin Reading Centre.
Diabetic maculopathy has been classified using the terms focal, diffuse, ischaemic and mixed. Unfortunately these terms are often used without clear definitions. Published definitions for focal and diffuse maculopathy are based on features observed on clinical examination, colour photographs, fluorescein angiography (FA) and optical coherence tomography (OCT), either alone or in combination
[89,90,91,92]. Because of the large number of definitions and their inconsistent use, evaluation of published data on prevalence, prognosis and response to treatment of focal and diffuse maculopathy is challenging. Evidence from the ETDRS, which defined these terms according to the source of fluorescein leakage, did not support the concept that classification into focal and diffuse maculopathy is predictive of outcome after laser treatment [89]. Further confusion arises because the term ‘focal’ is used to describe a technique of applying laser directly to
microaneurysms when treating diabetic maculopathy [89]. Some authors have advocated that the use of these terms should be discouraged and replaced by a new vocabulary the features of which correlate with clinical outcomes [93].
Box 2.3 Clinically significant macular oedema (CSMO) as defined in the Early Treatment of Diabetic Retinopathy Study (ETDRS) [86]
1. Retinal oedema within 500μm of the centre of the fovea, or 2. Hard exudates within 500μm of the centre of the fovea if
associated with adjacent oedema, or
3. Retinal oedema ≥ 1 disc diameter (1500μm) within 1 disc diameter of the centre of the fovea
30
2.7 Liverpool Diabetic Eye Study grading
The LDES is a large cohort study of subjects in a newly established DR screening programme [9]. The LDES grading scheme is a simplified version of the ETDRS grading system described above [86]. Colour fundus photographs of 3 overlapping 45 degree fields are graded. Retinopathy and maculopathy are classified separately. Modifications of the ETDRS system were made following discussions with the
Wisconsin Fundus Photograph Reading Centre, Madison (Professor Simon Harding, personal communication). It was thought that the ETDRS system was too detailed and complex for use in routine clinical care. Therefore modifications were made to simplify the ETDRS system. Alterations were also made to reflect data from the ETDRS on photographic risk factors for progression to PDR and CSMO [70]. Greater weighting was given to venous changes and intra-retinal microvascular
abnormalities (IRMA). Reduced weighting was given to CWS. Additionally,
presence of exudates outside the macula was excluded from the LDES system and no distinction was made between small haemorrhages and microaneurysms.
The LDES grading scheme includes 10 levels for retinopathy and 6 for maculopathy (plus the option of ‘ungradeable’ for either category). Level of retinopathy is determined for each eye and a grade assigned based on the worse eye. Similarly, each eye is graded for maculopathy and the grade of the worse eye assigned to that subject. The macula is defined as a circular zone centered on the fovea, whose radius is the distance from the centre of the fovea to the temporal margin of the optic disc. In the LDES, retinal thickening is not determined directly for classification of maculopathy (this would require the use of clinical examination or stereoscopic photos). A grading system based on the presence of exudates is used. Levels of retinopathy and maculopathy in the LDES are shown in Table 2.2.
31 Table 2.2 Levels of retinopathy and maculopathy in the Liverpool Diabetic Eye Study [94]
Level Definition Retinopathy
10 No retinopathy 12 Questionable
20 Haemorrhages or microaneurysms < ETDRS standard photograph 2A † 30 Haemorrhages or microaneurysms > ETDRS standard photograph 2A,
and/or 1-6 cotton wool spots
40 Haemorrhages/ microaneurysms > ETDRS STD 2A and/or > 6 cotton wool spots; and/or 1 quadrant venous changes; and/or IRMA < ETDRS STD 8A
50 IRMA > ETDRS STD 8A
and/or 2 or more quadrants venous changes
and/or pre-retinal haemorrhage in absence of proliferation 60 Fibrovascular proliferation and/or proliferative retinopathy 70 Diabetic Retinopathy Study high risk characteristics
71 Tractional retinal detachment 72 No fundal view due to vitreous blood
90 Ungradeable due to any other reason e.g. media opacity
Maculopathy
0 No maculopathy
1 Questionable: < 50% certainty of presence of exudate 2 Exudate >1 disc diameter (DD) from fixation
3 Circinate ring of exudates within macula >1 disc area in size but not within 1 DD of fixation 4 Exudates within 1 disc diameter of fixation
and/or presence of clinically significant macular oedema
8 Exudates due to other diseases e.g. vein occlusion, choroidal neovascularisation 90 Ungradeable
† Definition of any diabetic retinopathy: ≥ 1 haemorrhages of microaneusyms (HMa) in either eye. Flame shaped haemorrhages associated with hypertension are discounted.
ETDRS STD = Early Treatment of Diabetic Retinopathy Study Standard Photograph IRMA = Intraretinal Microvascular Abnormalities