Pyn verminder deurdat die lenssterkte astigmatisme regstel.

In this sentence, deurdat introduces the reason or mechanism for something happening. A natural English equivalent is because, by the fact that, or through the fact that.

So:

• Pyn verminder = Pain decreases / Pain is reduced
• deurdat die lenssterkte astigmatisme regstel = because the lens power corrects astigmatism

Compared with omdat, deurdat often sounds a bit more like because of the way that or through the process that, so it can emphasize the means or mechanism more strongly.

Because deurdat introduces a subordinate clause, and in Afrikaans subordinate clauses the finite verb usually goes to the end.

So the structure is:

• Main clause: Pyn verminder
• Subordinate clause: deurdat die lenssterkte astigmatisme regstel

That final position of regstel is normal after conjunctions like omdat, dat, terwyl, as, and deurdat.

Regstel is a separable verb in Afrikaans, similar to some Dutch and German verbs.

In a main clause, it often splits:

• Die lenssterkte stel astigmatisme reg.

But in a subordinate clause, it usually stays together at the end:

• ... deurdat die lenssterkte astigmatisme regstel.

So this sentence shows the form you expect in a subordinate clause.

Verminder means to reduce, to lessen, or to decrease.

In this sentence it is used intransitively:

• Pyn verminder = Pain decreases / Pain lessens

But it can also be used transitively in other contexts:

• Die medikasie verminder die pyn. = The medication reduces the pain.

So the verb can work both ways depending on the sentence.

Afrikaans often leaves out the article when talking about something in a general sense, especially with abstract or uncountable nouns.

So:

• Pyn verminder = Pain decreases

This is similar to English, where you can also say Pain decreases without the.

If you wanted to refer to a specific pain, you might say:

• Die pyn verminder. = The pain decreases.

Here, die lenssterkte refers to a specific lens power, so the definite article die is used.

• die lenssterkte = the lens power / the prescription strength

But astigmatisme is being used more like a general medical condition or concept, so Afrikaans can leave the article out:

• astigmatisme regstel = correct astigmatism

This is much like English, where we also often say correct astigmatism, not necessarily correct the astigmatism.

Lenssterkte is a compound noun:

• lens = lens
• sterkte = strength / power

So lenssterkte literally means lens strength, and in context it means the power of the lens or the prescription strength.

Afrikaans makes heavy use of compound nouns, just like Dutch and German. Instead of writing several separate words, Afrikaans often combines them into one.

Yes, it is very close. Astigmatisme is the Afrikaans word for astigmatism.

A lot of scientific and medical vocabulary in Afrikaans looks familiar to English speakers, although the spelling may differ slightly.

It is active in form, but the subject is not a person. The noun pyn is the subject, and verminder describes what happens to it:

• Pyn verminder = Pain decreases

This is not passive like Pain is reduced, although that may be the most natural English translation in some contexts.

So literally, the Afrikaans sentence is closer to:

• Pain decreases because the lens power corrects astigmatism.

Yes, omdat would also be possible in many contexts:

• Pyn verminder omdat die lenssterkte astigmatisme regstel.

That would simply mean Pain decreases because the lens power corrects astigmatism.

Using deurdat can suggest a slightly more specific sense of through the fact that or by the process that, so it may sound a bit more explanatory or technical.

The sentence has this structure:

• Pyn = subject
• verminder = verb
• deurdat ... regstel = subordinate clause explaining why

So:

• Main clause: Pyn verminder
• Subordinate clause: deurdat die lenssterkte astigmatisme regstel

Inside the subordinate clause:

• die lenssterkte = subject
• astigmatisme = object
• regstel = verb at the end

That final verb placement is one of the most important things for learners to notice here.