What is the percentage of central retinal artery occlusion (CRAO) cases that resolve to normal vision without treatment versus with treatment using thrombolytics, such as tissue plasminogen activator (tPA)?

Visual Recovery Rates in Central Retinal Artery Occlusion

Without treatment, only 17.7% of CRAO patients achieve functional visual recovery (defined as improvement from 20/200 or worse to 20/100 or better), while early thrombolytic therapy within 4.5 hours increases this rate to approximately 39% for achieving 20/100 or better vision. 1, 2

Natural History Without Treatment

The prognosis for untreated CRAO is devastatingly poor:

• Only 17.7% (70 of 396 patients) achieve functional visual recovery without intervention, defined as improving from 20/200 or worse at presentation to 20/100 or better at follow-up 1
• Nearly 80% of untreated patients maintain visual acuity of "count fingers" or worse at final follow-up 1
• Spontaneous improvement occurs in less than 15% of cases according to historical data 3
• The natural history demonstrates minimal recovery to normal vision, with the vast majority experiencing permanent severe visual disability 1

Outcomes With Thrombolytic Treatment

Intravenous tPA (Within 4.5 Hours)

The evidence for IV thrombolysis shows modest but meaningful improvement over natural history:

• Visual acuity of ≥20/100 achieved in 39.0% of patients treated with IV tPA within 4.5 hours 2
• Visual improvement of ≥0.3 logMAR (approximately 3 lines) occurred in 74.3% of patients receiving IV tPA within 4.5 hours (95% CI: 60.9-86.0%) 2
• However, one small randomized trial showed only 25% (2 of 8 patients) achieved ≥3 line improvement at 1 week, with neither patient sustaining improvement at 6 months 4
• The critical caveat: both patients who improved in the randomized trial received tPA within 6 hours, suggesting the therapeutic window is extremely narrow 4

Intra-Arterial tPA (Within 12-24 Hours)

IAT shows variable results depending on timing:

• Visual acuity of ≥20/100 achieved in 21.9% of patients treated with IAT within 24 hours 2
• Visual improvement of ≥0.3 logMAR occurred in 60.0% of IAT patients within 24 hours (95% CI: 49.1-70.5%) 2
• In a focused series treating within 12 hours, 53% improved by ≥3 lines, with 27% improving from count fingers or worse to 20/80 or better 5
• The EAGLE trial, which treated patients at a mean of 13 hours (with only 4 of 41 patients treated within 6 hours), failed to show benefit and was stopped early 1

Critical Time Window Considerations

The therapeutic window for thrombolysis in CRAO appears to be substantially shorter than the 4.5-hour window used for cerebral stroke:

• Experimental evidence in primates shows retinal ganglion cells remain viable if occlusion lasts <97 minutes, but suffer irreversible damage after 240 minutes 1
• Clinical evidence suggests treatment within 6 hours is necessary for any meaningful benefit 4
• The failure of trials treating patients beyond 6 hours reinforces this narrow window 1, 3

Comparative Analysis: Treatment vs. No Treatment

The data demonstrates approximately a 2-fold improvement in achieving functional vision (20/100 or better) with early IV thrombolysis compared to natural history:

• Natural history: 17.7% achieve functional recovery 1
• IV tPA within 4.5 hours: 39.0% achieve ≥20/100 vision 2
• Absolute risk reduction: approximately 21%
• Number needed to treat: approximately 5 patients to achieve one additional functional visual recovery

Important Caveats

Recovery to truly "normal" vision (20/20 or better) remains exceedingly rare even with treatment:

• The definition of "functional recovery" in most studies is 20/100 or better, not normal 20/20 vision 1, 2
• Even among treatment responders, residual visual field defects are universal 3, 5
• Reocclusion after initial reperfusion is a documented problem, potentially requiring adjuvant anticoagulation 4
• The presence of a cilioretinal artery (15-25% of patients) can preserve some central vision regardless of treatment 1

Quality of Life Impact

The stakes of treatment decisions are substantial:

• Unilateral severe visual loss increases fall risk (OR 2.86) and functional dependence (OR 7.50) 1
• 39% of surveyed adults would accept stroke risk and 37% would accept mortality risk to triple their chances of recovering 20/100 vision in one eye when the other eye is sighted 1
• Over 80% would accept these risks if the unaffected eye is not sighted 1