What are the possible causes and treatments for blurred vision at night, especially in older adults or those with a history of eye diseases, diabetes, or other conditions that could affect vision?

Blurred Vision at Night: Causes and Management

Blurred vision at night in adults, particularly those with diabetes or pre-existing eye disease, requires urgent ophthalmologic evaluation to rule out diabetic retinopathy, cataracts, or other sight-threatening conditions that may be asymptomatic despite progressive disease.

Primary Differential Diagnosis

Diabetic-Related Causes

• Diabetic retinopathy is the most frequent cause of new blindness in adults aged 20-74 years and can present with blurred vision, including night vision disturbances 1
• Acute hyperglycemia can cause blurred vision as the first and only presenting symptom of uncontrolled diabetes, even before classic diabetic symptoms appear 2
• Diabetic keratopathy with acute corneal edema can cause sudden vision changes when blood sugar is poorly controlled 3
• Cataracts occur earlier and more frequently in diabetic patients and are a major cause of visual impairment, responsible for vision loss in 33% of older-onset diabetic patients 4, 5

Non-Diabetic Causes in Older Adults

• Age-related cataracts are 1.5 times more likely in elderly diabetic persons compared to age-matched non-diabetic persons 4
• Glaucoma occurs earlier and more frequently in people with diabetes 1
• Dry eye syndrome and other comorbid ocular conditions contribute to vision loss synergistically with diabetes 4

Immediate Action Required

Prompt referral to an ophthalmologist is mandatory for any patient with diabetes presenting with vision changes, as sight-threatening disease may be asymptomatic and delayed treatment significantly worsens outcomes 6, 1.

Specific Referral Criteria

• Any level of macular edema 1, 6
• Severe nonproliferative diabetic retinopathy (NPDR) 1, 6
• Any proliferative diabetic retinopathy (PDR) 1, 6
• Visual symptoms in diabetic patients regardless of known retinopathy status 6

Screening Recommendations

For Type 2 Diabetes (Most Relevant for Older Adults)

• Initial dilated comprehensive eye examination by ophthalmologist or optometrist should occur at the time of diabetes diagnosis 1, 7
• Annual follow-up examinations are required if any level of retinopathy is present 1
• Screening every 1-2 years may be considered only if there is no evidence of retinopathy for one or more annual exams AND glycemia is well controlled 1, 7

For Type 1 Diabetes

• Initial examination within 5 years after diabetes onset 1, 7
• Annual examinations thereafter 1

Risk Factor Optimization (Grade A Recommendations)

Glycemic Control

• Target hemoglobin A1c <7% to prevent and delay diabetic retinopathy progression 7, 6
• Intensive glycemic control prevents retinopathy in 29-37% of patients compared to standard care 6
• Check glycosylated hemoglobin immediately in patients presenting with blurred vision to identify uncontrolled diabetes 2

Blood Pressure Control

• Target blood pressure <130/80 mmHg to reduce retinopathy risk and progression 7, 6
• Hypertension significantly increases risk of macular hemorrhage and must be aggressively controlled 6
• Blood pressure optimization is a Grade A recommendation for preventing diabetic retinopathy 7

Lipid Control

• Target LDL <100 mg/dL for high cardiovascular risk patients 7
• Optimizing serum lipid control is a Grade A recommendation for reducing retinopathy risk 7, 1

Treatment Considerations

For Confirmed Diabetic Retinopathy

• Intravitreal anti-VEGF injections (ranibizumab or aflibercept) are first-line treatment for diabetic macular edema, administered monthly initially 6
• Laser photocoagulation remains indicated for high-risk PDR and clinically significant macular edema 1, 6
• Anti-VEGF therapy improves retinopathy severity scores by 2+ steps in 29-37% of patients versus 8-16% with laser alone 6

Cardiovascular Protection

• Aspirin therapy for cardioprotection should NOT be discontinued, as it does not increase retinal hemorrhage risk in diabetic retinopathy patients 1, 7, 6
• Aspirin is indicated for cardiovascular protection in diabetic patients with 10-year CV risk >10% 7

Critical Clinical Pitfalls

• Do not delay referral until symptoms worsen - patients with sight-threatening disease may be completely asymptomatic 6, 1
• Do not assume vision changes are benign refractive errors - blurred vision may be the only presenting symptom of uncontrolled diabetes before classic symptoms appear 2
• Do not overlook systemic disease - sudden corneal opacity without obvious trauma should prompt evaluation for poorly controlled diabetes 3
• Do not wait for annual screening - any new visual symptoms in diabetic patients require immediate ophthalmologic evaluation 6

Special Population: Pregnancy

• Pregnant diabetic patients require eye examination in the first trimester with close follow-up throughout pregnancy and for 1 year postpartum, as pregnancy accelerates retinopathy progression 1, 6