A Cochrane review [Abstract] 2 included 5 studies comparing laser photocoagulation with currently available lasers to no (or deferred) treatment. Treatment with laser reduced the risk of severe visual loss by over 50% but there was little difference in terms of loss of 15 or more letters of visual acuity (best-corrected visual acuity = BCVA) (table T1). There was a beneficial effect on progression of diabetic retinopathy with treated eyes experiencing a 50% reduction in risk of progression of diabetic retinopathy (tableT1) and a similar reduction in risk of vitreous haemorrhage.
Comment: The quality of evidence is downgraded by study limitations (lack of allocation concealment).
| Outcome: Follow-up: 12 months | Relative effect (95% CI) | Assumed risk- Control - No treatment or deferred treatment | Risk with intervetnionb - Laser photocoagulation (95% CI) | No of participants (studies) |
|---|---|---|---|---|
| Loss of 15 or more letters | RR 0.99 (0.89 to 1.11) | Low risk (non-proliferative DR): 100 per 1000 | Low risk: 99 per 1000 (89 to 111) | 8926 (2) |
| High risk (proliferative DR): 250 per 1000 | High risk: 248 per 1000 (223 to 278) | |||
| Severe visual loss (BCVA < 6/60) | RR 0.46 (0.24 to 0.86) | Low risk: 10 per 1000 | Low risk: 5 per 1000 (2 to 9) | 9276 (4) |
| High risk: 50 per 1000 | High risk: 23 per 1000 (12 to 43) | |||
| Progression of diabetic retinopathy | RR 0.49 (0.37 to 0.64) | Low risk: 100 per 1000 | Low risk: 49 per 1000 (37 to 64) | 8331 (4) |
| High risk: 400 per 1000 | High risk: 196 per 1000(148 to 256) |
A topic in Clinical Evidence 1 summarizes the results of 6 RCTs comparing different regimens of laser photocoagulation with no treatment or deferred treatment in eyes with different grades of diabetic retinopathy. Laser photocoagulation reduced the risk of moderate visual loss compared with no treatment after 5 years (RRs 0.10 to 0.77, NNTs 2-9 in different trials.
A topic in Clinical Evidence 1 summarizes the resultsof 3 RCTs comparing argon laser photocoagulation with no treatment in eyes with maculopathy. A large trial (n=2244) found that laser photocoagulation reduced the risk of moderate visual loss compared with no treatment after 3 years (RR 0.50, 95% CI 0.47 to 0.53, NNT 8 eyes). Subgroup analysis found that focal laser treatment was significantly more effective in eyes with clinically significant macular oedema. One trial (160 eyes) found that in eyes with clinically significant macular oedema grid laser photocoagulation reduced loss of visual acquity at 12 months compared with no treatment (RR 0.84, NNT 4 eyes) and at 24 months (RR 0.78, 95% CI 0.10 to 0.96, NNT 3 eyes).
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