La visión está un poco borrosa.

Because estar is normally used for a temporary state or condition, and blurry vision is usually understood as a condition someone is experiencing at the moment.

So:

• La visión está un poco borrosa = the vision is a bit blurry right now / at the moment.
• La visión es borrosa would sound more like a general, defining characteristic, which is much less natural here.

This is the same general contrast as:

• está cansado = he is tired
• es cansado = he is tiring / boring / exhausting by nature

So in this sentence, estar is the expected verb.

Because borrosa agrees with la visión, which is a feminine singular noun.

In Spanish, adjectives usually agree in gender and number with the noun they describe:

• la visión borrosa → feminine singular
• el texto borroso → masculine singular
• las imágenes borrosas → feminine plural
• los documentos borrosos → masculine plural

Since visión is feminine, the adjective must be borrosa.

Spanish often uses the definite article (el, la, los, las) where English would use a possessive like my.

So instead of saying:

• Mi visión está un poco borrosa

Spanish very naturally says:

• La visión está un poco borrosa

This often happens with body parts and personal conditions, especially when the owner is already obvious from the context.

That said, mi visión is not wrong. It just sounds a bit more explicit or contrastive. In many everyday situations, la visión sounds more natural.

They are related, but not always identical in use.

• visión = vision, the faculty or quality of seeing
• vista = sight, eyesight, or view

In many health-related contexts, both can work, but vista is often more common in everyday speech when talking about eyesight:

• Tengo la vista un poco borrosa.
  This is very natural in everyday Spanish.

• La visión está un poco borrosa.
  Also correct, and understandable, but it can sound slightly more formal or clinical depending on context.

So if you are speaking casually in Spain, vista is often the more common choice.

Un poco means a little / a bit, so it softens the statement.

Compare:

• La visión está borrosa. = The vision is blurry.
• La visión está un poco borrosa. = The vision is a little blurry.

Spanish very often uses un poco the same way English uses a bit. It can make the sentence sound more natural, less dramatic, or more precise.

You could also hear:

• algo borrosa = somewhat blurry
• bastante borrosa = quite blurry
• muy borrosa = very blurry

Grammatically, someone would understand you, but it is not the natural choice in this context.

Using ser here suggests a more permanent or inherent quality, while blurry vision is usually treated as a state. So Spanish prefers:

• La visión está un poco borrosa.

In health and symptom descriptions, estar is usually the safe choice for temporary conditions:

• Estoy mareado.
• Tengo la garganta irritada.
• La vista está cansada.

It is correct and understandable, but in everyday spoken Spanish in Spain, people would very often say:

• Tengo la vista un poco borrosa.
• Veo un poco borroso.

These are especially common in casual speech.

The differences are roughly:

• La visión está un poco borrosa.
  Correct, slightly more neutral or clinical.

• Tengo la vista un poco borrosa.
  Very natural everyday phrasing.

• Veo un poco borroso.
  Very natural and direct: I’m seeing things a bit blurry / blurry.

So your sentence is good, but it is useful to know the more colloquial alternatives.

The written accent shows where the stress falls: vi-SIÓN.

Without the accent, Spanish stress rules would make you read it differently. The accent is needed because the stress falls on the last syllable, and the word ends in n.

So:

• visión → stress on -sión

This accent mark is part of the correct spelling and should always be written.

A simple pronunciation guide is:

• borrosa ≈ boh-RRO-sa

A few details:

• the rr is a strong rolled or trilled r
• the stress falls on RRO
• the b in normal Spanish speech is often softer than English b, especially between vowels

So the rhythm is:

• boh-RRO-sa

And visión is:

• bee-SYON in much of Spain, because sión sounds like syon
• more exactly: bi-SYON

Yes, but the standard and most natural order is:

• La visión está un poco borrosa.

You might also hear variations in special contexts, but they are less neutral:

• Está un poco borrosa la visión.
  Possible, but more marked or literary.

• La visión borrosa...
  This is a noun phrase, not a full sentence.

For a learner, the safest pattern is:

noun + estar + adverb + adjective

For example:

• La imagen está muy borrosa.
• La pantalla está un poco sucia.
• La vista está bastante cansada.