Раствор для линз уже открыт.

Because для normally requires the genitive case.

• линза = lens
• nominative plural: линзы
• genitive plural: линз

So для линз means for lenses.

This is a very common pattern in Russian:

• вода для детей = water for children
• чехол для телефона = case for a phone
• раствор для линз = solution for lenses

Открыт is the short form, while открытый is the full form.

In this sentence, Russian uses the short form because it works like a predicate after the noun, similar to saying that something is open / has been opened.

• Раствор открыт. = The solution is open / has been opened.
• Открытый раствор = an open/opened solution

So:

• full form (открытый) is more like an attributive adjective: it goes directly before a noun
• short form (открыт) is commonly used in statements like this one

It agrees with раствор, which is a masculine singular noun.

So the short-form endings are:

• masculine: открыт
• feminine: открыта
• neuter: открыто
• plural: открыты

Examples:

• Форма открыта. = The container/package is open.
• Окно открыто. = The window is open.
• Двери открыты. = The doors are open.

Since раствор is masculine, открыт is the correct form.

It can feel like either, depending on context.

In a sentence like Раствор для линз уже открыт, the idea is usually:

• it is already open
• or it has already been opened

Russian often focuses on the resulting state, not on making the same distinction English does between is open and has been opened.

So открыт here suggests a current state that resulted from someone opening it.

In Russian, the verb to be is usually omitted in the present tense.

So where English says:

• The solution is already open

Russian simply says:

• Раствор для линз уже открыт.

This is completely normal. Russian does use forms of быть in the past and future, but usually not in the present when linking a subject to a description.

Уже means already.

In this sentence, it shows that the opening has happened before now, or earlier than expected/relevant:

• Раствор для линз открыт. = The solution is open.
• Раствор для линз уже открыт. = The solution is already open.

So уже adds that sense of already rather than just stating the condition.

Because it naturally modifies the predicate открыт.

Russian word order is fairly flexible, but this placement is very natural:

• Раствор для линз уже открыт.

It keeps the sentence clear and neutral. Other word orders are possible, but they may sound more marked or emphasize something different.

For a learner, this is the safest neutral pattern to remember:

• subject
• extra description
• уже
• short-form predicate

Russian has no articles like a/an/the.

So раствор для линз can mean:

• lens solution
• a solution for lenses
• the solution for lenses

Which one is intended depends on context.

English speakers often want a one-to-one equivalent for the, but Russian simply does not mark that grammatically.

Yes, it is a normal and natural phrase.

Literally it means solution for lenses. In context, people will usually understand it as contact lens solution.

If someone wants to be more explicit, they might say:

• раствор для контактных линз = solution for contact lenses

But раствор для линз is very common in everyday use when the context is clear.

Historically and grammatically, it is often analyzed as a short-form passive participle from открыть (to open), but in many practical learning situations it behaves a lot like a short-form adjective.

What matters most for a learner is this:

• it agrees with the noun in gender and number
• it is used in predicate position
• it describes a state resulting from an action

So you do not need to worry too much about the label at first. The important pattern is:

• магазин открыт = the store is open
• дверь закрыта = the door is closed
• раствор уже открыт = the solution is already open / has already been opened

Usually, no—not in this sentence.

Открытый is the full form, and it is more natural when directly describing a noun:

• открытый флакон = an open bottle
• открытая дверь = an open door

But after the noun in a statement like The solution is already open, Russian strongly prefers the short form:

• Раствор для линз уже открыт.

So for this type of sentence, открыт is the natural choice.