What are the differentials for a patient presenting with blurred vision?

Differential Diagnosis for Blurred Vision

Blurred vision requires systematic evaluation of refractive, ocular surface, media, and posterior segment pathology, with refractive errors being the most common treatable cause in clinical practice. 1

Refractive Causes (Most Common)

Uncorrected or Incorrectly Corrected Refractive Errors

• Myopia (nearsightedness): Difficulty seeing distant objects clearly, with near vision typically preserved 1, 2
• Hyperopia (farsightedness): Difficulty with near vision, though distance vision may also be affected depending on accommodative ability 1, 3
• Astigmatism: Blurred or distorted vision at all distances due to irregular corneal or lenticular curvature 1, 2
• Presbyopia: Age-related loss of near vision beginning around age 40-45 years due to decreased lens flexibility and accommodation 1, 3
• Anisometropia: Unequal refractive errors between the two eyes causing visual imbalance 1, 2

Clinical Pearl: A pinhole test is highly effective for rapidly distinguishing optical refractive causes from other pathology—improvement with pinhole strongly suggests refractive error as the primary etiology 2

Fluctuating Refractive Errors

• Uncontrolled diabetes mellitus: Hyperglycemia causes lens swelling and hyperopic shifts; as glucose normalizes, refractive error changes significantly 4
  • Initial presentation often shows +2.5 D hyperopia with fasting glucose >400 mg/dL 4
  • After glucose control (FPG ~200 mg/dL), refractive error typically reduces to +0.75 D 4
  • Critical caveat: Delay prescribing glasses for 4-6 weeks after diabetes diagnosis until glucose stabilizes 4

Ocular Surface Disorders

Dry Eye Syndrome

• Symptoms: Intermittent blurred vision, often worse upon waking and improving later in the day; burning, foreign body sensation 1
• Mechanism: Tear film instability disrupts the optical surface 1
• Associated conditions: Sjögren's syndrome, meibomian gland dysfunction, medication-induced (antihistamines, antidepressants) 1

Corneal Pathology

• Corneal edema: Blurred vision with diurnal variation (worse upon waking, clearer later in day due to evaporation) 1
  • Causes include Fuchs dystrophy, elevated IOP, endothelial dysfunction, post-surgical complications 1
• Corneal opacification: Scarring from infection (herpes simplex keratitis), trauma, dystrophies, or band keratopathy 1

Lens and Media Opacities

Cataract

• Presentation: Gradual progressive blurred vision, glare disability (especially with oncoming headlights), reduced contrast sensitivity 1
• Examination findings: Lens opacity on slit-lamp biomicroscopy correlating with visual symptoms 1
• Functional impact: Visual acuity may be near-normal in dim lighting but drops significantly with glare testing 1

Posterior Capsule Opacification

• Context: Occurs after cataract surgery, causing gradual vision decline 1
• Incidence: 4-7% in various studies 1

Retinal and Macular Pathology

Age-Related Macular Degeneration (AMD)

• High-risk populations: Particularly in high hyperopia (25% of visual impairment cases) and emmetropia 5
• Presentation: Central vision loss, metamorphopsia, difficulty with reading and facial recognition 5

Myopic Macular Degeneration

• Critical association: The leading cause of visual impairment in high myopia (38.9% of cases) 5
• Risk stratification:
  • Myopia ≤-6 D: OR 3.4 for visual impairment 5
  • Myopia <-10 D: OR 22.0 for visual impairment 5

Diabetic Macular Edema and Retinopathy

• Symptoms: Blurred vision (8% report visual disturbance), maculopathy (5-11% depending on severity) 6
• Associated findings: Retinal hemorrhages, exudates, neovascularization 6

Retinal Vein Occlusion

• Presentation: Sudden or subacute unilateral vision loss with retinal hemorrhages 6

Vitreous Pathology

• Vitreous hemorrhage: Sudden vision loss with floaters, often in diabetic retinopathy or retinal tears 6
• Posterior vitreous detachment: Floaters and photopsias with variable vision changes 1

Optic Nerve Disorders

• Optic neuritis: Painful eye movements, decreased color vision, relative afferent pupillary defect 1
• Glaucoma: Peripheral vision loss initially, but can affect central vision in advanced disease 1, 7
• Optic nerve hypoplasia: Congenital condition with reduced visual acuity 7

Neurological Causes

• Cortical visual impairment: Bilateral vision loss with normal pupillary responses and fundus examination 1
• Migraine with aura: Transient visual disturbances with characteristic fortification spectra 1

Medication-Related

• Topical corticosteroids: Can cause elevated IOP leading to corneal edema 1
• Systemic medications: Various drugs affecting accommodation, tear production, or causing macular toxicity 1

Diagnostic Approach Algorithm

1. Initial screening: Pinhole test—if vision improves, refractive error is likely primary cause 2
2. Check for fluctuation: In diabetics, measure fasting glucose and defer final refraction until stable 4
3. Assess timing: Worse upon waking suggests corneal edema or dry eye 1
4. Evaluate for glare: Significant glare disability with relatively preserved acuity suggests cataract 1
5. Examine systematically: Slit-lamp for anterior segment, dilated fundus exam for posterior pathology 1
6. Consider age: Presbyopia begins age 40-45; AMD and cataract increase with age 1, 3, 5

Common pitfall: In newly diagnosed diabetes, prescribing glasses before glucose stabilization leads to incorrect prescriptions requiring frequent changes 4