My relative experiences visual hallucinations when her eyes are closed and sees light streaks or flashes (photopsia) when her eyes are open; what could be causing this?

Visual Hallucinations and Photopsias: Differential Diagnosis and Management

Your relative needs urgent ophthalmologic evaluation within 24 hours to rule out posterior vitreous detachment with retinal tears, which occurs in 8-22% of patients presenting with flashes and can lead to permanent vision loss if untreated. 1

Immediate Triage: Rule Out Vision-Threatening Emergencies

The combination of flashes (photopsias) when eyes are open and visual phenomena when eyes are closed requires systematic evaluation to distinguish benign from sight-threatening causes.

High-Risk Features Requiring Same-Day Ophthalmology Referral

Flashes and light streaks when eyes are open strongly suggest posterior vitreous detachment (PVD), which carries a 14% risk of retinal tear. 2 The following features dramatically increase this risk:

• Subjective visual reduction increases retinal tear risk 5-fold (LR 5.0) 2
• More than 10 new floaters increases risk 8-36 fold 2
• Vitreous hemorrhage increases retinal tear likelihood 10-fold (LR 10) 2
• Flashes described as quick, lightning-like, white, and temporally located (96% of PVD cases) 3
• Symptoms triggered by head or eye movements (60% of PVD) 3

Critical Examination Findings

The ophthalmologist must perform indirect ophthalmoscopy with scleral indentation to detect retinal breaks, as patients initially diagnosed with uncomplicated PVD have a 3.4% chance of developing retinal tears within 6 weeks. 2 Absence of vitreous pigment on slit-lamp examination reduces retinal tear likelihood by 77% (LR 0.23). 2

Differential Diagnosis Based on Clinical Pattern

Pattern 1: Flashes/Light Streaks With Eyes Open

Posterior vitreous detachment accounts for 39.7% of photopsias in vitreoretinal patients. 3 The vitreous separates from the retina between ages 45-65, earlier in myopia and trauma. 1

Key distinguishing features of PVD photopsias: 3

• Quick duration (96%)
• Lightning/flash morphology (96%)
• White color (87%)
• Temporal location (86%)
• Preferentially seen in dark environments (90%)
• Associated with new floaters (85%)

Retinal detachment presents similarly but with more non-temporal photopsias (40% vs 14%, p=0.01). 3

Alternative causes of photopsias when PVD is excluded:

• Migraine aura (6.5% of photopsias): Often misinterpreted as monocular by patients, typically zig-zag patterns, scintillating scotomas, lasting 5-60 minutes 1, 4
• Neovascular AMD (7.9%): Centrally located (83%), quick and repetitive (79%), seen in both light and dark, no inciting stimuli (84%), more likely non-white (40%) 3
• Vertebrobasilar insufficiency (2.8%): Bilateral simultaneous photopsias, associated with vertigo, diplopia, or syncope 3

Pattern 2: Visual Phenomena With Eyes Closed

Charles Bonnet Syndrome (CBS) is the most likely diagnosis for visual hallucinations with eyes closed in patients with any degree of vision impairment. 1

CBS diagnostic criteria (all four must be present): 1, 5

1. Recurrent, vivid visual hallucinations
2. Preserved insight that images are not real (critical distinguishing feature)
3. No other neurological or medical diagnosis explaining hallucinations
4. Some degree of vision loss (reduced acuity, contrast sensitivity, or visual field)

CBS affects 15-60% of visually impaired patients depending on population studied. 1 The hallucinations result from cortical-release phenomena due to lack of afferent visual input. 1

Red Flags Requiring Neuropsychiatric Evaluation

The following atypical features indicate alternative diagnoses requiring brain MRI and neurological workup: 1, 5

• Lack of insight into unreality of hallucinations despite CBS education
• Hallucinations that interact with the patient
• Associated neurological signs: weakness, numbness, cognitive decline, parkinsonism
• Medication-induced: anticholinergics, dopaminergic agents, propranolol (causes visual disturbances and hallucinations per FDA labeling), steroids 6, 7

Alternative diagnoses to consider:

• Parkinson's disease: Visual hallucinations occur in 80% of patients 5
• Dementia with Lewy Bodies: Visual hallucinations are a core diagnostic criterion 1, 5
• Alzheimer's disease, psychiatric disorders, medication side effects 1

Management Algorithm

Step 1: Urgent Ophthalmology Referral (Within 24 Hours)

All patients with new-onset flashes and light streaks require same-day ophthalmologic examination to detect retinal tears, as 95% of retinal detachments can be successfully repaired if caught early, with better visual outcomes when treated before macular involvement. 1

Step 2: If Retinal Pathology Excluded and CBS Diagnosed

Education is therapeutic and first-line treatment. 1, 7 Explaining that CBS hallucinations are common in visually impaired people leads to significant relief and decreased anxiety. 1

Recommend self-management techniques: 1, 7

• Eye movements
• Changing lighting conditions
• Distraction techniques

Refer to vision rehabilitation services to optimize remaining vision through lighting modifications, magnification, contrast enhancement, and provide psychological support groups. 7 Psychological therapies and support groups provide moderate-quality evidence for improving vision-related quality of life and depression. 1

Step 3: Screen for Depression and Anxiety

Vision loss significantly increases risk of mental health deterioration. 7 Professional psychiatric assessment is mandatory for patients reporting severe mood changes, interference with daily life, or suicidal ideation. 1, 7

Step 4: Pharmacological Treatment (Reserved for Severe Distress)

Pharmacological treatment is NOT first-line for CBS. 7 There is no significant evidence of efficacy for any pharmacological agent in typical CBS. 1 Do not prescribe antipsychotics reflexively, as typical CBS patients maintain insight and hallucinations are benign. 7, 8

If severe distress persists despite education and non-pharmacological measures, atypical antipsychotics (risperidone, olanzapine, quetiapine) have been used in case reports with limited evidence. 7

Common Pitfalls to Avoid

• Never dismiss flashes as benign without ophthalmologic examination - retinal tears develop in 8-22% of acute PVD cases 1
• Do not assume visual phenomena are monocular based on patient report alone - migraine aura is often misinterpreted as monocular 1
• Do not overlook medication review - propranolol, anticholinergics, dopaminergic agents, and steroids can cause visual hallucinations 7, 6
• Do not ignore the psychological impact of vision loss - address through rehabilitation and support services 7
• Ensure follow-up within 6 weeks even if initial examination is normal, as 3.4% develop delayed retinal tears 2