What causes seeing halos around lights at night while driving?

Seeing Halos While Driving at Night: Causes and Evaluation

Seeing halos around lights while driving at night is most commonly caused by corneal issues, cataracts, or angle-closure glaucoma, requiring prompt ophthalmologic evaluation to prevent potential vision loss.

Common Causes of Halos Around Lights

Primary Angle-Closure Disease

• Halos around lights are a classic symptom of angle-closure, particularly during an acute angle-closure crisis 1
• Often accompanied by blurred vision, eye pain, headache, eye redness, and potentially nausea and vomiting 2
• Pressure-induced corneal edema is experienced as blurred vision and halos around lights 2
• Requires immediate medical attention as untreated angle-closure can lead to permanent vision loss 1, 2

Cataracts

• Different types of cataracts can cause halos around lights, particularly when driving at night 3
• Posterior subcapsular cataracts (PSC) commonly cause glare and poor vision in bright light conditions, affecting near vision more than distance vision 3
• Cortical cataracts frequently cause glare symptoms, appearing as opaque spokes or oil droplets in the lens 3
• Nuclear cataracts progress slowly and affect distance vision more than near vision 3

Post-Refractive Surgery Effects

• Quality of vision under low-light conditions can be reduced after LASIK surgery 1
• Smaller treatment-zone sizes, especially in high refractive corrections, may increase the likelihood of visually disturbing halo formation in low-light conditions 1
• Rainbow glare specifically associated with femtosecond laser procedures can cause halos 1

Other Causes

• Corneal edema from various causes can lead to halos around lights 4, 5
• Medication side effects, such as amiodarone keratopathy, can cause halos and glare 5
• Anterior uveitis with elevated intraocular pressure can present with halos around lights 6

Evaluation Algorithm

Initial Assessment

1. Determine urgency based on associated symptoms:

   • Presence of pain, redness, nausea, or sudden vision loss suggests acute angle-closure requiring emergency evaluation 1, 2
   • Gradual onset with no pain suggests cataracts or refractive issues 3

2. Key history elements to obtain:

   • Duration and progression of symptoms 1
   • History of refractive surgery 1
   • Current medications, particularly those affecting the eye 5
   • Family history of glaucoma 2
   • Presence of risk factors for angle-closure (hyperopia, Asian descent, age over 50, female gender) 2

3. Physical examination focus:

   • Visual acuity assessment 1
   • Pupil examination (may be mid-dilated in acute angle-closure) 1
   • Slit-lamp examination to assess:
     • Corneal edema 1, 2
     • Lens opacities 3
     • Anterior chamber depth 1, 2
     • Signs of inflammation 6
   • Intraocular pressure measurement 1
   • Gonioscopy to assess angle structures 1

Management Based on Cause

For Acute Angle-Closure

• Immediate medical therapy to lower IOP including topical beta-blockers, alpha2-agonists, carbonic anhydrase inhibitors, and oral/IV hyperosmotic agents 2
• Definitive treatment with laser peripheral iridotomy once IOP is controlled 2
• Treatment of the fellow eye to prevent angle-closure 2

For Cataracts

• Regular monitoring for progression 3
• Consideration of cataract surgery when visual function is significantly affected 3
• Glare testing is particularly useful for evaluating the functional impact of cortical and posterior subcapsular cataracts 3

For Post-Refractive Surgery Halos

• Evaluation for possible irregular astigmatism or corneal ectasia 1
• Management of dry eye disease which may contribute to visual symptoms 1
• Consideration of enhancement procedures in select cases 1

Important Considerations and Pitfalls

• Delayed diagnosis of acute angle-closure can lead to permanent vision loss, with 18% of eyes becoming blind within 4-10 years following an untreated acute angle-closure crisis 2
• Halos while driving represent a significant safety concern, as they can impair a driver's ability to safely operate a vehicle, particularly at night 7
• Cataract-induced disability glare increases with age and is a specific functional risk factor for driving difficulty 7
• Simple devices (halometers) can be used to quantify the effect of halos on vision, which may be helpful in monitoring progression and determining when intervention is necessary 8