What is the differential diagnosis for colored flashing lights?

Differential Diagnosis for Colored Flashing Lights

The most critical immediate concern when a patient reports colored flashing lights is posterior vitreous detachment (PVD) with potential retinal tear, which occurs in 8-22% of patients presenting with acute photopsias and requires same-day ophthalmologic evaluation to prevent permanent vision loss. 1, 2

Urgent Ophthalmologic Causes (Require Same-Day Evaluation)

Posterior Vitreous Detachment with Retinal Tear

• Flashing lights are typically described as brief, occurring in the dark, and located in the peripheral/lateral visual field due to vitreous traction on the retina as it separates 1, 3
• Colored, small circular patterns flashing or multiplying in a temporal hemifield are characteristic of retinal pathology 4
• Associated symptoms include new floaters (especially a "shower"), peripheral visual field loss like a curtain, or decreased visual acuity - all red flags requiring emergency evaluation 2, 5
• Risk factors include age 45-65 years, myopia, recent eye trauma, or recent intraocular surgery 1, 5
• Critical: Even if initial examination is normal, 2-5% develop retinal breaks within 6 weeks, requiring follow-up within this window 1, 2, 5

Retinal Artery Occlusion (Ocular Stroke)

• Presents with sudden, painless vision loss rather than isolated flashing lights, but may have visual disturbances 1
• Requires immediate emergency department referral to certified stroke center within 4.5-hour window for potential tPA treatment 5

Neurologic Causes

Occipital Seizures (Occipital Epilepsy)

• Visual seizures consist of colored, small circular patterns flashing or multiplying, lasting seconds to 1-3 minutes (occasionally up to 20-150 minutes) 4
• Key distinguishing features: frequent occurrence (often multiple clusters daily/weekly), may progress to other seizure manifestations, and can trigger severe postictal headache 4
• Flashing lights or non-circular patterns are rare; achromatic flickering lights occur in some patients 4
• Often misdiagnosed as migraine, but differs markedly in duration, pattern, and characteristics 4

Migraine Visual Aura

• Classic migraine aura presents with linear, zigzag, achromatic or black-and-white patterns lasting over 4 minutes - distinctly different from the colored circular patterns of retinal pathology 4
• Typically progresses slowly across visual field (fortification spectra) rather than sudden flashing 4

Medication/Toxicity-Related Causes

Immune Checkpoint Inhibitor Ocular Toxicity

• Patients on immunotherapy should be counseled to report new onset of flashing lights, as ocular immune-related adverse events occur in <1% but require prompt ophthalmologic referral 1
• Associated symptoms include blurred vision, floaters, changes in color vision, eye redness, or photophobia 1

Essential Immediate Evaluation Steps

For any patient presenting with colored flashing lights, you must:

1. Assess visual acuity in each eye separately 2, 5
2. Ask specifically about: unilateral vs bilateral symptoms, new floaters (especially sudden "shower"), peripheral visual field loss, recent trauma, and timing/duration of flashes 1, 2, 6
3. Check for relative afferent pupillary defect 5
4. Refer immediately for same-day dilated fundoscopic examination with scleral depression by ophthalmology - this is non-negotiable for new-onset symptoms 1, 2, 5, 3

Critical Management Pitfalls to Avoid

• Never delay ophthalmologic referral for "observation" with new-onset flashing lights - 50% of untreated symptomatic retinal tears progress to detachment 3
• Do not reassure patients that normal initial examination rules out pathology - retinal breaks develop in 2-5% within 6 weeks even when first exam is normal 1, 2, 5
• Avoid misdiagnosing occipital seizures as migraine - colored circular flashing patterns lasting seconds to minutes occurring in clusters suggest seizures, not migraine 4
• Do not assume bilateral symptoms exclude serious pathology - while PVD is typically unilateral, bilateral presentations occur in 1-2% of cases 1

The presence of vitreous pigment on ophthalmologic examination has a negative likelihood ratio of 0.23 for ruling out retinal tear when absent, making urgent specialized examination essential rather than primary care assessment alone 2, 6