Optikeren måler synsstyrken og pupilafstanden.

Because optikeren is the definite singular form of optiker.

• en optiker = an optician
• optikeren = the optician

In Danish, the definite article is often attached to the end of the noun instead of appearing as a separate word. For many common-gender nouns, that ending is -en.

Danish usually puts the onto the noun itself.

So instead of separate words like in English:

• the optician
• the visual acuity
• the pupil distance

Danish uses:

• optikeren
• synsstyrken
• pupilafstanden

That means the definiteness is already built into the noun, so you do not add another separate word for the here.

Måler is the present tense of måle, meaning to measure.

• at måle = to measure
• måler = measures / is measuring

A very common Danish pattern is that the present tense ends in -r. Unlike English, Danish verbs do not change for different persons:

• jeg måler = I measure
• du måler = you measure
• optikeren måler = the optician measures

So -r here marks present tense, not a special form for he/she/it.

Because Danish forms compound nouns very often, much more than English does.

• synsstyrken = syns
  • styrke
    • -n
• pupilafstanden = pupil
  • afstand
    • -en

English often writes these ideas as two words or uses a phrase, but Danish commonly joins them into a single noun.

A useful rule: in Danish, if English has a noun + noun combination, Danish will often make it one word.

This happens because the compound includes a linking s.

The word is built from:

• syn = sight/vision
• linking -s-
• styrke = strength

So:

• syn + s + styrke → synsstyrke

Since styrke already begins with s, you get ss in spelling. This is normal in Danish compounds.

That is normal in Danish compounds. The first part of a compound is often just the basic dictionary form, not necessarily a plural.

So pupilafstand does not mean the distance of one pupil. It means pupillary distance, that is, the distance between the pupils.

English and Danish do not always build these technical terms in exactly the same way.

That depends on grammatical gender.

In Danish, singular nouns are mainly either:

• common gender → definite ending usually -en
• neuter gender → definite ending usually -et

Here:

• en optiker → optikeren
• en synsstyrke → synsstyrken
• en pupilafstand → pupilafstanden

All three are common-gender nouns, so they take -en.

A useful extra rule for compounds: the gender is determined by the last part of the compound. Since styrke and afstand are common-gender nouns, the full compounds are too.

No, this is the normal basic word order for a main clause:

• Optikeren = subject
• måler = verb
• synsstyrken og pupilafstanden = objects

So the pattern is:

subject + verb + object

This is very similar to English here.
More generally, Danish main clauses follow the verb-second rule, and this sentence fits that pattern naturally.

The å in måler is not like the English a in make. It is closer to the vowel in saw or British more.

So måler sounds roughly like MOH-ler, though actual Danish pronunciation is softer and more reduced than that English-style approximation.

A few helpful notes:

• å is a separate letter in Danish
• it often sounds like a broad aw/o sound
• the -er ending in Danish is usually weaker than in English

So if you say something roughly like MOH-luh, you are moving in the right direction.