Az optometrista a látásvizsgálaton kérdez.

Hungarian has two forms of the definite article:

• a before most consonant sounds
• az before vowel sounds

Because optometrista begins with a vowel sound, Hungarian uses az.

So:

• a tanár = the teacher
• az optometrista = the optometrist

This is similar to a/an in English, but note that a/az in Hungarian means the, not a/an.

It is built from smaller parts:

• látás = vision / sight
• vizsgálat = examination / test
• látásvizsgálat = vision test / eye test
• látásvizsgálaton = at/on/during the vision test

So this is a compound noun plus a case ending.

Hungarian often packs into one word what English expresses with several words.

The ending -on is one form of the superessive case, which often means on, upon, or sometimes at depending on the expression.

Here, a látásvizsgálaton is best understood as:

• at the vision test
• or during the vision test

Even though the basic case meaning is often taught as on, in real Hungarian it frequently matches English at or during.

For example:

• az asztalon = on the table
• az órán = in class / during class
• a látásvizsgálaton = at the eye test / during the eye test

That a is the definite article the.

So:

• a látásvizsgálaton = at the vision test

Hungarian uses the definite article quite regularly, including in places where English might also use the. Here it refers to a specific examination situation, not just any vision test in general.

Hungarian word order is more flexible than English word order. It is not random, but it is strongly influenced by topic and focus.

In this sentence:

• Az optometrista is the topic: what the sentence is about
• a látásvizsgálaton gives the setting
• kérdez comes at the end as the verb

This is a very natural neutral order.

English usually requires a more fixed order like Subject + Verb + Place/Time, but Hungarian often allows elements before the verb more freely.

So this sentence sounds natural as:

• Az optometrista a látásvizsgálaton kérdez.

A different word order could change the emphasis.

In Hungarian, kérdez can mean simply asks or asks questions without stating the object explicitly.

So the sentence does not need to say exactly what is being asked. The meaning is just that the optometrist is asking questions in that situation.

If you wanted to add an object, you could, for example:

• Az optometrista kérdéseket kérdez.
  This is grammatically possible, but awkward and unnatural because it is repetitive.

More natural would be something like:

• Az optometrista kérdez a tünetekről. = The optometrist asks about the symptoms.

So in your sentence, the object is simply left unstated because it is not important.

Hungarian usually does not need subject pronouns like he, she, or it when the subject is already clear.

Here the subject is explicitly stated:

• Az optometrista = the optometrist

So there is no need to add a pronoun.

Also, Hungarian verbs show person and number:

• kérdez = he/she/it asks

Because the subject noun is present, everything is clear without any extra pronoun.

Kérdez is the third person singular present tense form of the verb kérdezni (to ask).

So:

• kérdezek = I ask
• kérdezel = you ask
• kérdez = he/she asks

Since az optometrista is singular, the verb must also be singular: kérdez.

Hungarian verbs change according to the subject, so you do not need a separate word like does.

Yes, literally the case ending is the one often translated as on, but you should not translate it too mechanically.

In this sentence, the natural English idea is:

• at the vision test
• during the vision test

Hungarian case endings often cover a range of meanings that do not match one single English preposition exactly. So the best approach is:

• learn the basic meaning of -on/-en/-ön
• then learn common expressions as whole phrases

Here, a látásvizsgálaton is one of those phrases where English prefers at or during.

The superessive case has several forms:

• -on
• -en
• -ön

The choice depends partly on vowel harmony and partly on the shape of the word. Unfortunately, this is not always completely predictable just from English-style rules, so some forms need to be learned with the noun.

For látásvizsgálat, the correct form is:

• látásvizsgálaton

Other examples:

• asztal → asztalon
• szék → széken
• föld → földön

So the important thing here is to learn the full form látásvizsgálaton as the correct case form of látásvizsgálat.

Not in the same way.

• Az optometrista means the optometrist
• a látásvizsgálaton means at the vision test

If you removed the articles, the sentence would sound unnatural or incomplete in standard Hungarian.

Hungarian articles are used differently from English in some contexts, but in this sentence they are definitely expected. The sentence is referring to a specific person and a specific situation, so the definite articles are natural and correct.