Что касается контактных линз, то нужен раствор для линз.

It means as for ..., regarding ..., or when it comes to ....

So:

• Что касается контактных линз, ... = As for contact lenses, ...

Literally, что касается comes from the verb касаться (to concern, to touch on), so the phrase originally has the sense of what concerns ... But in normal Russian, learners should usually understand it as a set expression meaning as for / regarding.

It is a very common topic-shifting phrase, especially in neutral or slightly formal speech.

Because что касается requires the genitive case.

The dictionary form is:

• контактные линзы = contact lenses

But after что касается, it becomes:

• контактных линз = of contact lenses / regarding contact lenses

So the pattern is:

• что касается + genitive

Examples:

• Что касается работы... = As for work...
• Что касается денег... = As for money...
• Что касается контактных линз... = As for contact lenses...

In the pattern Что касается X, то Y, the word то helps mark the main statement that follows the topic.

So the structure is roughly:

• Что касается X, то Y
• As for X, Y

In English, we usually do not need a separate word like то, so it may feel unnecessary. In Russian, it is very common in this construction.

Here it separates:

• the topic: Что касается контактных линз
• the comment/main point: нужен раствор для линз

You will often see both versions:

• Что касается контактных линз, нужен раствор для линз.
• Что касается контактных линз, то нужен раствор для линз.

The version with то sounds especially clear and structured.

Because нужен agrees with the thing that is needed: раствор.

• раствор is masculine singular
• so the predicate is нужен

Compare:

• нужен раствор = solution is needed / a solution is needed
• нужна салфетка = a wipe is needed
• нужно лекарство = medicine is needed (neuter)
• нужны линзы = lenses are needed (plural)

So in this sentence, the important grammatical subject is really:

• раствор → masculine singular
• therefore нужен

Not exactly. It is the short form of the adjective нужный (needed, necessary), but in sentences like this it functions much like is needed.

So:

• нужный = full adjective form, like necessary/needed
• нужен / нужна / нужно / нужны = short forms used in predicate position

Examples:

• Мне нужен врач. = I need a doctor.
• Нужна помощь. = Help is needed.
• Нужно время. = Time is needed.

For learners, it is usually easiest to understand нужен/нужна/нужно/нужны as meaning is needed / are needed.

Russian often leaves this unspecified if it is clear from context or not important.

So нужен раствор для линз literally means something like:

• a lens solution is needed
• solution for lenses is needed

Depending on context, it could imply:

• I need lens solution
• we need lens solution
• you need lens solution
• or just a general statement about what is necessary

Russian often focuses on what is needed, not explicitly who needs it, unless that information matters.

If you wanted to say I need solution for lenses, you could say:

• Мне нужен раствор для линз.

Here:

• мне = to me / for me, which is how Russian expresses I need

Because раствор by itself just means solution and is too general.

• раствор can mean a liquid solution of many kinds
• раствор для линз specifically means solution for lenses, i.e. contact lens solution

The phrase для линз tells us what the solution is for.

This is a very common Russian structure:

• крем для рук = hand cream
• очки для чтения = reading glasses
• салфетки для лица = facial wipes
• раствор для линз = lens solution

Because the two parts are doing different jobs.

1. Что касается контактных линз
   This sets the topic: as for contact lenses

2. раствор для линз
   This names the needed item: solution for lenses

So the repetition is natural. English might also repeat the word:

• As for contact lenses, lens solution is needed.

Russian could also say:

• Что касается контактных линз, то нужен раствор для контактных линз.

But that sounds a bit more repetitive than necessary, because once линз is already mentioned, раствор для линз is usually enough.

Because Что касается контактных линз is an introductory/topic-setting part of the sentence, and it is separated from the main statement.

So the punctuation reflects the structure:

• Что касается контактных линз, то = As for contact lenses,
• нужен раствор для линз. = the main statement

The comma is standard in this kind of construction.

It is natural, but Что касается ... sounds somewhat structured, neutral, or slightly formal. It is very common in explanations, discussions, customer service, written language, and careful speech.

This sentence feels like something you might hear in a shop, pharmacy, or consultation:

• Что касается контактных линз, то нужен раствор для линз.

In more casual speech, people might say something simpler, for example:

• Для контактных линз нужен раствор.
• Если речь о контактных линзах, нужен раствор.

But the original sentence is perfectly normal and correct.

The basic structure is:

• Что касается контактных линз, то нужен раствор для линз.

This is:

1. topic
2. main statement

Russian word order is flexible, but this order is good because it first introduces the topic and then gives the information about it.

A simpler version with different structure would be:

• Для контактных линз нужен раствор.

That means essentially the same thing, but it no longer uses the explicit as for ... topic structure.

So the original order is especially useful when the speaker is discussing several topics and moving from one to another.