Does HFRS Cause Vision Changes? Eye Symptoms Explained

Sudden blurry vision can be frightening, especially when you are already dealing with a serious viral infection. In Hemorrhagic Fever with Renal Syndrome (HFRS)—particularly cases caused by the Puumala orthohantavirus, known as Nephropathia Epidemica—temporary nearsightedness (transient myopia) is a recognized symptom ^[1]. While this symptom occurs in a substantial minority of patients (about 35% in one study) and usually resolves without permanent damage, it is not something you should simply ignore or wait out ^[2]. Any sudden change in your vision should be evaluated promptly by your medical team to confirm the cause and rule out more serious complications.

Why Does Hantavirus Affect the Eyes?

Hantaviruses cause changes to the lining of your body’s blood vessels, leading to a phenomenon known as “capillary leak” ^[3]. This means fluid can temporarily leak out of your small blood vessels and into the surrounding tissues ^[4].

When this capillary leak occurs in the eyes, fluid accumulates in the internal structures of the eye—a condition called ciliochoroidal effusion ^[5]. This extra fluid physically pushes on the structures inside your eye, making the front chamber of your eye slightly shallower and changing the way your eye focuses light ^[5]. The structural shift is what causes you to become temporarily nearsighted and makes distant objects look blurry ^[5].

What to Expect in Uncomplicated Cases

When vision changes are caused by uncomplicated transient myopia from Puumala HFRS, they are generally temporary. Studies of patient populations have observed general trends, though individual experiences will vary:

• Timing: Blurred vision often appears during the acute phase of the illness (around day 5 in some studies) ^[2]. This sometimes happens shortly before kidney-related symptoms—like a drop in urine output (oliguria)—become obvious ^[2].
• Duration: The nearsightedness is typically short-lived. In one study, the blurriness lasted an average of two days, though your timeline may differ ^[2].
• Recovery: As the acute illness and associated fluid shifts resolve, your vision usually returns to normal. The structural changes in the eye are generally reversible, and uncomplicated transient myopia is not expected to cause permanent vision loss ^{[2] [5]}.

When to Be Concerned and Seek Immediate Care

Because HFRS can cause severe systemic issues—including acute kidney injury, blood pressure drops, and bleeding—you should always remain under close medical supervision ^[3]. Do not assume all blurred vision is harmless transient myopia.

In rare cases, the fluid buildup in the eye can cause a secondary complication called acute angle closure, which leads to a sudden, dangerous increase in eye pressure (elevated intraocular pressure) ^[5]. Untreated, this high pressure can threaten your vision ^[6].

Contact your treating team immediately if you experience vision changes. Seek emergency medical care if you experience your blurry vision alongside any of these warning signs:

• Severe eye pain or a feeling of intense pressure in the eye
• Significant redness in the eye
• Seeing “halos” or rings around lights
• Sudden partial or complete vision loss, a dark “curtain” or shadow over your vision, flashes of light, new floaters, or double vision
• Severe headache, persistent vomiting, confusion, severe weakness, or seizures, which could indicate serious systemic illness, shock, or neurological complications ^{[7] [8]}

Safety Steps You Can Take Now

• Do not drive, cycle in traffic, or operate machinery while your vision is blurred. Arrange transportation for your medical assessments.
• Contact your care team today to report the symptom, even if you do not have eye pain. A clinician may need to check your visual acuity, pupils, and eye pressure.
• Follow your team’s instructions regarding fluid intake and medications. Do not start using any eye drops or change how much fluid you are drinking without direct medical advice.