What is the differential diagnosis (DD) of glare in the eye?

Differential Diagnosis of Glare in the Eye

The differential diagnosis of glare in the eye includes cataracts (particularly posterior subcapsular and cortical types), acute angle-closure glaucoma, corneal edema, refractive surgery complications (LASIK/irregular astigmatism), and advanced glaucoma with media opacities.

Primary Cataract-Related Causes

Cataracts are the most common cause of glare symptoms, with specific patterns depending on cataract type:

• Posterior subcapsular cataracts (PSC) cause the most severe glare symptoms, particularly in bright light conditions, with near vision typically more affected than distance vision due to miosis with accommodation 1
• Cortical cataracts commonly produce glare symptoms, appearing as opaque spokes or oil droplets, with patients frequently complaining of glare when driving at night 1
• Nuclear cataracts primarily affect distance vision and progress slowly, causing less prominent glare compared to PSC or cortical types 1
• Glare testing is particularly useful for evaluating cortical and posterior subcapsular cataracts, which significantly impact vision in bright light conditions 2, 1

Acute Angle-Closure Glaucoma

Halos around lights are a classic symptom of angle-closure, representing a true ophthalmologic emergency:

• Acute angle-closure crisis presents with halos around lights, blurred vision, eye pain, headache, eye redness, and potentially nausea and vomiting 3
• Pressure-induced corneal edema is experienced as blurred vision and halos around lights, requiring immediate ophthalmologic evaluation to prevent permanent vision loss 3
• Immediate medical therapy to lower IOP (topical beta-blockers, alpha2-agonists, carbonic anhydrase inhibitors, oral/IV hyperosmotic agents) is required, with definitive treatment via laser peripheral iridotomy once IOP is controlled 3

Advanced Glaucoma

Primary open-angle glaucoma, particularly in advanced stages, causes measurable disability glare:

• Patients with advanced-severe glaucoma have significantly worse disability glare than those with mild-moderate glaucoma 4
• Visual acuity reduction due to glare from mild-moderate to advanced-severe glaucoma (mean -3.4 letters) is of almost identical magnitude to that caused by media opacity 4
• The worse the glare symptoms or signs, the more variable the agreement between objective and subjective assessments 4

Post-Refractive Surgery Complications

Patients with a history of refractive surgery require specific evaluation:

• History of LASIK or other refractive surgery should prompt evaluation for irregular astigmatism or corneal ectasia 3
• Smaller treatment-zone sizes may increase the likelihood of visually disturbing halo formation in low-light conditions 3
• Higher-order aberrations (coma, spherical aberration, trefoil) cannot be fully corrected by spherocylindrical lenses and may contribute to glare symptoms 2

Corneal Pathology

Various corneal conditions produce glare through light scatter:

• Irregular corneal astigmatism from keratoconus, corneal ectasias, corneal epithelial basement membrane dystrophies, stromal dystrophies, and corneal scarring cause glare 2
• Postsurgical corneas may develop irregular astigmatism contributing to glare symptoms 2
• Ocular surface disease can cause significant reduction in visual acuity with glare testing, requiring correlation with slit-lamp biomicroscopy findings 2

Clinical Evaluation Algorithm

The initial assessment must determine urgency based on associated symptoms:

• Emergency evaluation required: Presence of pain, redness, nausea, or sudden vision loss suggests acute angle-closure 3
• Key history elements: Duration and progression of symptoms, history of refractive surgery, family history of glaucoma 3
• Physical examination focus: Visual acuity assessment, pupil examination, slit-lamp examination for corneal edema, lens opacities, and anterior chamber depth 3
• Gonioscopy is essential to exclude angle closure or secondary causes of IOP elevation 5

Objective Glare Testing

Disability glare is caused by scattered intraocular light (straylight) that reduces retinal image contrast:

• The Brightness Acuity Tester (BAT) has the highest accuracy (73%) for predicting outdoor Snellen acuity within one Snellen line 6
• Contrast sensitivity testing may reveal functional vision loss not detected by standard visual acuity testing alone 2, 1
• Glare testing determines the degree of visual impairment in the presence of light scatter, particularly useful when visual acuity appears normal in darkened examination rooms but drops significantly with glare source 2

Important Clinical Pitfalls

Colored filters do not reduce disability glare: In common environments where glare and target illumination have similar spectra, colored spectacle or intraocular lens filters reduce both proportionately and do not increase retinal image contrast or decrease disability glare 7

Visual acuity alone is insufficient: Some patients with cataract may have normal or near-normal visual acuity in darkened rooms but experience severe visual disability in bright scenarios 2