האישון קטן, אבל חדות הראייה טובה.

Because this is a present-tense nominal sentence. In Hebrew, when you say that something is something in the present, you usually do not use a separate word for is.

So:

• האישון קטן = the pupil is small
• חדות הראייה טובה = the visual acuity is good

In past or future, Hebrew does use forms of to be, but in the present, they are normally omitted.

ה־ is the Hebrew definite article, meaning the.

So:

• אישון = pupil
• האישון = the pupil

and

• ראייה = vision / seeing
• הראייה = the vision

Hebrew adds the article directly to the beginning of the word, instead of using a separate word like English the.

Because אישון is a masculine singular noun, and adjectives in Hebrew must agree with the noun they describe in gender and number.

So:

• אישון is masculine singular
• therefore the adjective is קטן = masculine singular small

If the noun were feminine singular, you would expect קטנה instead.

Because טובה agrees with חדות, and חדות is a feminine singular noun.

That is the key point: the adjective is not agreeing with הראייה directly. It is agreeing with the head noun חדות.

So:

• חדות = feminine singular
• therefore the adjective is טובה

This is true even though the whole phrase is חדות הראייה.

Not here. In this sentence, חדות is a singular abstract noun meaning something like sharpness or acuity.

Although ־ות is often a plural ending in Hebrew, it can also appear in singular abstract nouns.

So חדות here is singular, not plural.

That is why the adjective is singular feminine:

• חדות ... טובה
• not חדות ... טובות

This is a very common thing for learners to notice, so your instinct is understandable.

They form a construct chain (in Hebrew grammar, often called סמיכות).

So חדות הראייה literally means:

• the sharpness of the vision
• or more naturally, visual acuity

In a construct chain:

1. the first noun is the head noun
2. the second noun tells you what kind or whose or of what

Here:

• חדות = acuity / sharpness
• הראייה = the vision

Together: the acuity of the vision

Because in a Hebrew construct chain, the definiteness is usually marked on the second noun, not the first.

So:

• חדות הראייה is definite because הראייה is definite
• you do not normally say החדות הראייה

This is one of the important rules of construct phrases in Hebrew: the whole phrase can be definite even if the first noun has no ה־.

Grammatically, טובה describes חדות, not הראייה.

That matters because in a construct chain, the adjective agrees with the head noun—the first noun in the chain.

So in:

• חדות הראייה טובה

the structure is:

• חדות הראייה = the visual acuity
• טובה = good

The adjective comes after the whole construct phrase, but it still agrees with חדות.

Because Hebrew adjectives normally come after the noun they describe, and when the noun is part of a construct chain, the adjective comes after the entire chain.

So Hebrew does this:

• חדות הראייה טובה

not:

• חדות טובה הראייה

That second version would sound wrong.

A good way to think about it is that חדות הראייה behaves as one unit, and then the adjective is added after that unit.

It is pronounced roughly ha-re-iyá or ha-re'iyá, with the stress on the last syllable.

A few helpful points:

• ה־ = ha-
• the א creates a slight break between vowels
• the stress is final: -yá

So the full sentence is pronounced approximately:

ha-i-SHON ka-TAN, a-VAL kha-DUT ha-re-i-YA to-VA

Exact pronunciation varies a bit by speaker, but that is a good learner-friendly approximation.

אבל means but.

It connects the two parts of the sentence:

• האישון קטן
• חדות הראייה טובה

So the meaning is:

• The pupil is small, but the visual acuity is good.

Yes, the comma is normal. In Hebrew, as in English, a comma is commonly used before אבל when it joins two full clauses.

It is a very common Hebrew pattern:

• definite noun + adjective
• but + noun phrase + adjective

More specifically, both halves are nominal clauses:

• האישון קטן
• חדות הראייה טובה

This pattern is extremely common in Hebrew, especially in descriptions, medical language, everyday observations, and written explanations. It is worth getting very comfortable with, because you will see it often.