What are the possible ocular and systemic causes of blurred vision?

Blurred Vision: Ocular and Systemic Causes

Blurred vision requires systematic evaluation for both sight-threatening ocular conditions (cataract, glaucoma, AMD, retinal detachment) and serious systemic diseases (diabetes, hypertension, neurologic disorders, giant cell arteritis), with comprehensive ophthalmologic examination being essential for diagnosis and preventing permanent vision loss.

Primary Ocular Causes

Cataract

• Cataract accounts for approximately 50% of low-vision cases in adults over 40 and is the leading cause of treatable blindness in African Americans, Hispanics, and individuals of European descent over age 40 1
• Smoking significantly increases cataract progression risk 1
• Early surgical intervention can restore vision and quality of life 1

Age-Related Macular Degeneration (AMD)

• AMD causes progressive central vision loss and is a leading cause of blindness in older adults 1
• Neovascular AMD should be treated immediately upon diagnosis with anti-VEGF therapy to prevent legal blindness and visual impairment 1
• Early symptoms may be subtle (blurred or distorted central vision), making comprehensive eye examination critical for early detection 1
• Smoking is a major modifiable risk factor for AMD progression 1

Glaucoma

• Acute angle-closure glaucoma presents with sudden blurred vision, severe eye pain, headache, nausea, halos around lights, and mid-dilated pupil requiring immediate treatment 1, 2, 3
• Treatment includes pilocarpine drops, acetazolamide, and mannitol to lower intraocular pressure emergently 3
• Primary open-angle glaucoma causes gradual, painless vision loss with peripheral visual field defects 1
• Risk factors include family history (2.5-3 fold increased risk), African descent, myopia, and systemic hypertension 1, 4

Refractive Errors

• Uncorrected refractive errors (myopia, hyperopia, astigmatism, presbyopia) are common reversible causes of blurred vision 1, 4
• Formal refraction and corrective lenses typically resolve symptoms 4

Retinal Detachment

• Presents with sudden curtain-like visual field defect, floaters, and flashes of light 3, 5
• Requires urgent surgical intervention to prevent permanent vision loss 3, 5
• Risk factors include high myopia, prior ocular trauma, and lattice degeneration 1

Vitreous Hemorrhage

• Causes sudden painless vision loss with floaters 5
• Common in diabetic retinopathy and retinal tears 5

Optic Nerve and Neurologic Causes

Optic Neuritis

• Presents with painful vision loss (pain worsens with eye movement), color desaturation, relative afferent pupillary defect, and may have normal visual acuity initially 1, 3, 6
• Often the initial manifestation of multiple sclerosis 1, 3
• MRI of orbits and brain with contrast is the primary imaging study to evaluate optic nerve enhancement and detect demyelinating brain lesions 1, 2
• Treatment requires high-dose corticosteroids 3

Giant Cell Arteritis (GCA)

• Must be excluded emergently in patients over 50 with vision changes, headache, scalp tenderness, or jaw claudication 2, 7, 3
• Check ESR, CRP, and platelet count immediately 2, 7, 3
• Initiate empiric corticosteroids before biopsy confirmation to prevent vision loss in the fellow eye 7, 3
• Temporal artery biopsy confirms diagnosis 3

Increased Intracranial Pressure

• Papilledema on fundoscopy indicates increased intracranial pressure from mass lesion, idiopathic intracranial hypertension, or cerebral venous thrombosis 2, 4
• Requires urgent neuroimaging (MRI brain with contrast preferred) 2
• Idiopathic intracranial hypertension is more common in young, overweight females 2

Retinal Artery Occlusion

• Causes sudden, painless, severe vision loss in patients with vascular risk factors 3, 5
• Central retinal artery occlusion shows cherry-red spot on fundoscopy 5
• Interventions aim to prevent vision loss in the other eye through cardiovascular risk factor management 3, 5

Cerebrovascular Accidents

• Posterior circulation strokes cause homonymous visual field defects 1, 5
• Confrontation visual fields can detect chiasmal tumors and stroke 1, 4

Systemic Disease Manifestations

Diabetes Mellitus

• Diabetic retinopathy causes progressive vision loss from macular edema, hemorrhages, and neovascularization 1
• Blurred vision can also result from fluctuating blood glucose affecting lens hydration 1
• Regular dilated fundus examinations are essential for early detection 1, 4

Hypertension

• Hypertensive retinopathy shows arteriolar narrowing, hemorrhages, and cotton-wool spots 1
• Severe hypertension can cause vision loss from retinal or optic nerve ischemia 1

Autoimmune and Inflammatory Diseases

• Anterior uveitis presents with photophobia, eye pain, ciliary flush, and blurred vision 1, 2, 4
• Associated with rheumatoid arthritis, inflammatory bowel disease, ankylosing spondylitis 1
• Requires urgent ophthalmology referral 2

Infectious Diseases

• Posterior segment infections (toxoplasmosis, tuberculosis, syphilis, HIV-related infections) cause chorioretinitis and vision loss 1
• Infectious keratitis presents with corneal infiltrate, pain, and photophobia 4

Neurologic Disorders

• Myasthenia gravis causes variable diplopia and ptosis with fatigable weakness 1, 4
• Multiple sclerosis commonly presents with optic neuritis 1, 3
• Horner's syndrome, midbrain tumors, and aneurysms affect pupillary function 1

Thyroid Disease (Graves' Disease)

• Causes proptosis, diplopia from extraocular muscle involvement, and compressive optic neuropathy 1
• External examination reveals lid retraction and periorbital edema 1, 4

Drug and Toxin Effects

• Hydroxychloroquine, tamoxifen, and phenothiazines cause retinal toxicity 1
• Heavy metals and various medications affect anterior segment structures 1

Critical Diagnostic Approach

Essential Examination Components

• Visual acuity testing at distance and near with current correction 4
• Pupillary examination for relative afferent pupillary defect, size, and reactivity 2, 4
• Confrontation visual fields to detect neurologic lesions 1, 4
• Fundoscopic examination (dilated) has 79% sensitivity and 82% specificity for detecting ocular disease and identifies papilledema, hemorrhages, and optic disc abnormalities 4
• Intraocular pressure measurement (defer if infection or trauma suspected) 4
• Slit-lamp biomicroscopy evaluates cornea, anterior chamber, lens, and anterior vitreous 4

Imaging Indications

• MRI brain with and without contrast is preferred for headache with blurred vision, suspected optic neuritis, or neurologic symptoms 1, 2
• CT head may substitute only if MRI unavailable but is less sensitive 2
• Orbital MRI provides superior soft-tissue resolution for intraocular masses and optic nerve pathology 1

Red Flags Requiring Urgent Referral

• Papilledema on fundoscopy (risk of permanent vision loss from increased intracranial pressure) 2, 4
• Acute angle-closure glaucoma (mid-dilated pupil, severe pain, very high IOP) 2, 3
• Sudden vision loss with vascular risk factors (possible retinal artery occlusion) 3, 5
• Age >50 with new headache and vision changes (rule out GCA and intracranial pathology) 2, 7, 3

Common Pitfalls to Avoid

• Do not rely solely on tonometry for glaucoma screening—comprehensive optic disc assessment and visual field testing are required 4
• Do not miss intermittent angle-closure glaucoma—patients reporting intermittent pain with spontaneous resolution require urgent gonioscopy, as this carries an 18% risk of permanent blindness 4
• Do not delay corticosteroids in suspected GCA—empiric treatment must begin before biopsy confirmation to prevent fellow-eye vision loss 7, 3
• Do not attribute persistent ocular symptoms despite treatment to ongoing structural disease—consider ocular neuropathic pain, especially with burning/shooting pain and photophobia out of proportion to findings 4