What does experiencing rainbow-colored halos around a white LED light suggest and what is the recommended evaluation?

Evaluation of Rainbow-Colored Halos Around LED Lights

Rainbow-colored halos around white LED lights most commonly indicate acute angle-closure glaucoma requiring emergency evaluation, though they can also result from corneal edema, cataracts, or prior refractive surgery—immediate assessment of intraocular pressure, pupil reactivity, and associated symptoms is essential to rule out sight-threatening conditions. 1, 2

Urgent vs. Non-Urgent Differentiation

The initial assessment must determine whether this represents an ophthalmologic emergency based on accompanying symptoms:

Red Flag Symptoms Requiring Emergency Evaluation

• Severe eye pain, headache, nausea, or vomiting suggest acute angle-closure crisis and require immediate ophthalmologic evaluation 1, 2, 3
• Mid-dilated, poorly reactive pupil with halos is pathognomonic for acute angle-closure 2, 3
• Eye redness with sudden vision loss indicates possible acute angle-closure or retinal artery occlusion 1, 2
• Transient episodes that self-resolve represent intermittent angle closure—a critical warning sign with 50% risk of acute attack within 5 years if untreated 2, 3

Non-Emergent Presentations

• Isolated halos without pain, redness, or vision loss suggest cataracts, corneal irregularities, or refractive surgery effects 1
• Bilateral chronic symptoms are more consistent with lens opacities or corneal changes 1

Critical History Elements

Obtain the following specific details to guide evaluation:

• Duration and pattern: Sudden onset versus gradual progression; constant versus intermittent episodes 1, 2
• Associated symptoms: Eye pain intensity, headache location, nausea/vomiting, vision changes 2, 3
• Prior refractive surgery: LASIK or other procedures, particularly with smaller treatment zones that increase halo formation in low-light conditions 1, 4
• Family history of glaucoma or personal history of hyperopia/narrow angles 2, 3
• Medication history: Recent pupil dilation or anticholinergic medications that could precipitate angle closure 2

Physical Examination Priorities

The examination must focus on identifying sight-threatening pathology:

Immediate Measurements

• Intraocular pressure (IOP): Markedly elevated IOP >40 mmHg confirms acute angle-closure crisis 2, 3
• Visual acuity: Sudden decrease suggests corneal edema from elevated pressure 2
• Pupil examination: Mid-dilated, poorly reactive, or oval pupil indicates acute angle-closure 2, 3

Slit-Lamp Examination

• Corneal edema: "Steamy" or hazy cornea from pressure-induced edema causes halos and confirms acute angle-closure 1, 2
• Anterior chamber depth: Shallow chamber on slit-lamp suggests anatomic predisposition to angle closure 2, 3
• Lens opacities: Posterior subcapsular cataracts commonly cause glare and halos, particularly with night driving 1
• Conjunctival/episcleral injection: Vascular congestion from elevated IOP 2

Additional Testing When Indicated

• Gonioscopy: Essential to confirm iridotrabecular contact in suspected angle closure 3
• Fundoscopy: "Boxcar" segmentation of retinal vessels indicates severe ischemia from acute angle-closure 2

Management Algorithm

If Acute Angle-Closure Crisis Suspected (IOP >40 mmHg, mid-dilated pupil, corneal edema):

Immediate medical therapy to lower IOP before definitive treatment 1, 2, 3:

• Topical beta-blockers (timolol 0.5%)
• Topical alpha-2 agonists (apraclonidine or brimonidine)
• Topical carbonic anhydrase inhibitors (dorzolamide)
• Oral or IV hyperosmotic agents (mannitol or glycerol)

Definitive treatment once IOP controlled 1, 3:

• Laser peripheral iridotomy (LPI) in affected eye
• Prophylactic LPI in fellow eye to prevent bilateral attacks

If Intermittent Angle Closure (transient symptoms, normal exam at presentation):

• Urgent ophthalmology referral within 24-48 hours for gonioscopy and prophylactic LPI in both eyes 2, 3
• Do not dismiss transient symptoms as benign—these represent warning episodes before potentially blinding acute attacks 2, 3

If Non-Emergent Presentation (normal IOP, reactive pupils, no pain):

Evaluate for cataracts 1:

• Posterior subcapsular opacities cause characteristic halos with bright lights
• Regular monitoring for progression; consider surgery when visual function significantly affected

Assess for refractive surgery complications 1, 4:

• History of LASIK with smaller treatment zones increases halo formation
• Evaluate for irregular astigmatism or corneal ectasia
• Rainbow glare specifically reported after IntraLASIK procedures, though typically clinically inconsequential

Consider corneal pathology 1:

• Corneal edema from various causes (endothelial dysfunction, prior surgery) produces halos
• Slit-lamp examination reveals corneal clarity and endothelial status

Critical Pitfalls to Avoid

• Never dilate pupils in patients with suspected narrow angles or intermittent angle-closure symptoms until after LPI is performed—dilation can precipitate acute crisis 2
• Do not delay treatment waiting for ophthalmology consultation if acute angle-closure is suspected; 18% of untreated eyes become blind within 4-10 years 2
• Do not dismiss transient symptoms even if the patient is asymptomatic at presentation—intermittent episodes are warning signs before potentially blinding acute attacks 2, 3
• Recognize that nausea/vomiting are not universal in acute angle-closure; absence of systemic symptoms does not exclude the diagnosis 2

Prognosis

Without treatment for acute angle-closure, the natural history is devastating: 48% develop glaucomatous optic neuropathy and 58% have visual acuity worse than 20/40 within 4-10 years 2. Immediate recognition and treatment are essential to prevent permanent vision loss.