Optikko sanoi, että näöntarkastus kestää vain vartin.

Että means that and introduces a reported clause:

• Optikko sanoi = the optician said
• että näöntarkastus kestää vain vartin = that the eye exam only takes fifteen minutes

It is a very common conjunction after verbs like sanoa for reporting what someone said.

The basic form is sanoa = to say.

Sanoi is the 3rd person singular past tense, so it means said.

A useful pattern:

• sanoa = to say
• hän sanoo = he/she says
• hän sanoi = he/she said

Here the subject is optikko, so Finnish does not need a separate word for he/she.

Finnish does not always shift tenses backward in reported speech the way English often does.

So after sanoi, Finnish can still use the present tense if the statement is:

• generally true
• still valid now
• about a scheduled or expected situation

So:

• Optikko sanoi, että näöntarkastus kestää vain vartin = The optician said that the eye exam takes only fifteen minutes

If you were talking about one specific exam that already happened, kesti could be possible in a different context.

Vartti is the dictionary form and means quarter or fifteen minutes.

In this sentence, vartin is used because Finnish normally marks an exact duration with a form that looks like the genitive after kestää:

• kestää tunnin = lasts an hour
• kestää päivän = lasts a day
• kestää vartin = lasts fifteen minutes

So vartin means for fifteen minutes or fifteen minutes long.

Yes, originally vartti means a quarter, but in time expressions it usually means a quarter of an hour, so 15 minutes.

So vain vartin means:

• only a quarter of an hour
• only fifteen minutes

A more explicit alternative would be vain viisitoista minuuttia, but vartin is very natural and common.

Yes, it is one compound word, and Finnish uses compounds very often.

It is made from:

• näön = of vision / of sight
• tarkastus = inspection, check, examination

So näöntarkastus literally means something like vision check or sight examination.

In natural English, this is usually eye exam, eye test, or vision test, depending on context.

The basic word is näkö = sight, vision.

In this compound, it appears as näön, which is the genitive form. Finnish often uses this kind of linking form in compounds.

So:

• näkö = vision
• näön = of vision
• näöntarkastus = vision examination

This is a normal Finnish pattern, although compounds are not all built in exactly the same way.

Finnish does not have articles.

So:

• optikko can mean an optician or the optician
• näöntarkastus can mean an eye exam or the eye exam

The exact meaning comes from context, not from a separate word like the or a.

Vain means only or just.

Here it goes before vartin, so it limits the duration:

• kestää vain vartin = takes only fifteen minutes

That placement is important. It tells you that the fifteen minutes part is what is being emphasized as small or short.

Yes, but moving it changes the focus.

Compare:

• näöntarkastus kestää vain vartin = the exam takes only fifteen minutes
• vain näöntarkastus kestää vartin = only the eye exam takes fifteen minutes

So in the original sentence, vain is placed where it most naturally means only fifteen minutes.

The original word order is the most neutral and natural one:

• Optikko sanoi, että näöntarkastus kestää vain vartin.

Finnish word order is somewhat flexible because endings carry a lot of grammatical information, but changing the order usually changes the emphasis.

So while other orders may be possible in special contexts, this version is the normal one for a plain statement.