Az optometrista ellenőrzi a látóteret és a látásélességet.

Both a and az mean the. Hungarian chooses between them based on the sound that follows:

• a before a consonant sound
• az before a vowel sound

Since optometrista begins with o, you need az: az optometrista.

Because the verb is in the 3rd person singular definite form.

Hungarian verbs often change depending on whether the direct object is definite or indefinite. Here the optometrist is checking specific things:

• a látóteret = the visual field
• a látásélességet = the visual acuity

Since the objects are definite, Hungarian uses the definite conjugation: ellenőrzi.

A useful comparison:

• ellenőriz valamit = checks something
• ellenőrzi a látóteret = checks the visual field

The dictionary form is ellenőrizni = to check / to examine / to inspect.

That -t marks the accusative case, which is usually used for the direct object.

In this sentence, the things being checked are the direct objects, so they take accusative endings:

• látótér → látóteret
• látásélesség → látásélességet

In English, word order usually shows the object. In Hungarian, case endings do a lot of that work.

Because Hungarian often uses a linking vowel before the accusative -t, and some nouns also change slightly in their stem when endings are added.

So:

• base form: látótér
• accusative: látóteret

This is something you often just have to learn with the noun. Not every word takes endings in exactly the same surface form.

Hungarian very often repeats the article before each noun in a list or pair:

• a látóteret és a látásélességet

This sounds completely natural and standard. Repeating the article helps make each noun feel clearly separate and definite.

English often does the same:

• the visual field and the visual acuity

They are both compound words.

látótér

• látó = seeing / visual
• tér = space / field

So látótér literally means something like visual field.

látásélesség

• látás = sight / vision
• élesség = sharpness

So látásélesség literally means sharpness of vision, i.e. visual acuity.

Hungarian builds many technical terms this way, especially in medical language.

No. Hungarian word order is more flexible than English word order and often depends on topic and emphasis.

This sentence has a very natural, straightforward order:

• Az optometrista = topic/subject
• ellenőrzi = verb
• a látóteret és a látásélességet = objects

So it feels like a neutral statement: The optometrist checks the visual field and visual acuity.

If you change the order, you may change the emphasis rather than the basic meaning.

No. Hungarian nouns do not have grammatical gender like he/she built into them.

So az optometrista can mean:

• a male optometrist
• a female optometrist

You only know the person’s sex if the context tells you.

Yes, very often.

Hungarian frequently leaves out subject pronouns, and even full subject nouns can be omitted if they are clear from context.

So after the subject has already been established, you might simply say:

• Ellenőrzi a látóteret és a látásélességet.

That means He/She is checking the visual field and visual acuity or checks the visual field and visual acuity, depending on context.

It can mean either one.

Hungarian present tense often covers both:

• checks
• is checking

So Az optometrista ellenőrzi... could mean:

• The optometrist checks...
• The optometrist is checking...

The context tells you which is meant.

A few helpful pronunciation points:

• ő is a long Hungarian vowel that does not exist in standard English.
• It is similar to a long ö sound, like in German or French rounded front vowels.
• Hungarian stress is usually on the first syllable of the word.

So:

• ellenőrzi is stressed at the start: EL-len-őr-zi
• optometrista is stressed on the first syllable: OP-to-me-tris-ta
• látóteret is stressed on the first syllable: LÁ-tó-te-ret
• látásélességet is also stressed on the first syllable: LÁ-tás-é-les-sé-get

Even in long words, the first syllable stress rule is very reliable in Hungarian.

Because és only means and. The definiteness is shown separately by the article a before the second noun:

• és = and
• a látásélességet = the visual acuity

So Hungarian keeps these parts separate:

• conjunction: és
• article: a
• noun with case ending: látásélességet

That is very typical of Hungarian sentence structure.