Die oogkaart is duideliker, behalwe dat ek nog dowwe visie het.

Afrikaans usually writes compound nouns as one word.
So:

• oog = eye
• kaart = chart/card

Together, oogkaart means eye chart.

Die is the Afrikaans definite article, so here it means the.

A useful thing for learners: Afrikaans uses die for:

• singular nouns
• plural nouns
• all grammatical genders

So it is much simpler than English in that sense.

Duidelik means clear.
Duideliker is the comparative form, meaning clearer.

Afrikaans often forms the comparative by adding -er:

• groot → groter
• duidelik → duideliker

So Die oogkaart is duideliker means the eye chart is clearer.

The comparison point is just understood from context. The sentence says the chart is clearer, but it does not spell out clearer than what.

If you wanted to include that idea explicitly, Afrikaans would normally use as:

• duideliker as voorheen = clearer than before
• duideliker as gister = clearer than yesterday

So in this sentence, the than part is simply left unstated.

Behalwe dat means except that.

It is used when behalwe is followed by a full clause, not just a noun.

Compare:

• behalwe die pyn = except the pain
• behalwe dat ek pyn het = except that I have pain

So here, behalwe dat ek nog dowwe visie het means except that I still have blurry vision.

Because dat introduces a subordinate clause.

In Afrikaans, when you have a subordinate clause introduced by a word like dat, the finite verb usually goes to the end.

Compare:

• Main clause: Ek het nog dowwe visie.
• After dat: dat ek nog dowwe visie het

That final het is very normal Afrikaans subordinate-clause word order.

Here nog means still.

It shows that the blurry vision continues:

• ek het nog dowwe visie = I still have blurry vision

Nog is a very common word and can have other meanings in other contexts, such as yet, more, or another, so context is important.

The basic adjective is dof. But when this adjective comes before a noun, Afrikaans often uses a changed or inflected form.

So:

• My visie is dof. = My vision is blurry/dim.
• Ek het dowwe visie. = I have blurry vision.

So dof is the basic form, while dowwe is the form used before the noun visie.

Visie can mean vision or eyesight, and it works well here.

Another common word is sig, which often sounds a bit more everyday for sight/vision. So learners may also come across:

• dowwe visie
• dowwe sig

Both are understandable. Visie can sound slightly more formal or medical depending on context.

The comma separates the main clause from the exception that follows.

Main idea:

• Die oogkaart is duideliker

Exception/additional qualification:

• behalwe dat ek nog dowwe visie het

So the comma helps the reader see that the sentence first makes a statement and then adds a limitation or exception to it.