La graduación de la lente bifocal subió una dioptría.

No. In this sentence, la graduación means the prescription/optical power of the lens, not a school graduation.

In Spain, graduación is commonly used when talking about glasses, contact lenses, or vision correction. So:

• la graduación de las gafas = the glasses prescription
• revisar la graduación = to check the prescription

This is a very common “false friend” for English speakers.

Spanish often uses a noun + de + noun structure where English might prefer a compound noun.

So:

• la graduación de la lente bifocal = the prescription/power of the bifocal lens

Compare:

• el color de la camisa = the color of the shirt
• la puerta del coche = the car door

Spanish usually avoids stacking nouns the way English does. English can say the bifocal lens prescription, but Spanish normally expresses that relationship with de.

In standard Spain Spanish, lente is normally feminine:

• la lente
• una lente

In some parts of Latin America, especially in everyday speech, you may also hear el lente. But for Spanish from Spain, la lente is the expected form.

Because it describes a singular noun:

• la lente bifocal = the bifocal lens

If the noun were plural, the adjective would usually be plural too:

• las lentes bifocales = the bifocal lenses

So the agreement is:

• singular noun → singular adjective
• plural noun → plural adjective

Yes. Subir can be used when a level, amount, number, or measurement goes up/increases.

Here it means the lens power or prescription increased:

• La graduación subió = The prescription went up / increased

This is a very natural use of subir in Spanish, just like:

• La temperatura subió = The temperature rose
• El precio subió = The price went up

So even though subir literally means to go up, it also works for numerical increases.

Because in this sentence, la graduación itself is the thing that increased.

Structure:

• La graduación ... subió una dioptría
• subject = la graduación
• verb = subió
• amount of increase = una dioptría

If you said le subió, that would introduce a person or thing affected by the increase, for example:

• Le subió la graduación = His/her prescription increased

But the original sentence simply states the change, without mentioning whose prescription it is.

Subió is the pretérito indefinido (simple past) of subir.

It refers to a completed change in the past:

• subió = it went up / it increased

The full conjugation in the preterite is:

• yo subí
• tú subiste
• él/ella/usted subió
• nosotros subimos
• vosotros subisteis
• ellos/ellas/ustedes subieron

Here subió agrees with la graduación, which is singular.

Because the increase was one diopter.

After numbers, Spanish uses:

• singular after uno/una
• plural after numbers greater than one

So:

• subió una dioptría = it increased by one diopter
• subió dos dioptrías = it increased by two diopters

This is completely normal number agreement.

In Spanish, it is very common to express the amount of change directly after verbs like subir and bajar:

• subió una dioptría
• bajó dos grados
• aumentó tres puntos

This means it went up by one diopter.

You may sometimes hear other structures in different contexts, but the direct expression of the amount is very natural and common here.

Yes. Aumentó would also be possible:

• La graduación de la lente bifocal aumentó una dioptría.

Both mean that the prescription/power increased by one diopter.

Very roughly:

• subió = went up
• aumentó = increased

Subió sounds a bit more like a rise upward; aumentó is a more neutral “increase.” In this sentence, both are natural.

It is understandable, but in real-life usage, many speakers would more often talk about:

• las gafas bifocales = bifocal glasses
• una lente bifocal = a bifocal lens
• el cristal bifocal = the bifocal lens/glass of the glasses (depending on region/context)

If the context is optometry, la lente bifocal is fine. Just be aware that everyday speech often refers to the whole glasses rather than a single lens.

Yes, it can. In context, graduación can refer to the corrective power associated with:

• a person’s vision correction generally
• a pair of glasses
• a contact lens
• one lens of the glasses

So la graduación de la lente bifocal is possible if you are specifically talking about that particular lens. Spanish allows that level of specificity.

The structure is:

• La graduación de la lente bifocal = subject
• subió = verb
• una dioptría = measure of how much it increased

So it works like:

[subject] + [verb] + [amount of change]

You can compare it with:

• El precio subió diez euros.
• La temperatura bajó dos grados.

This is a useful pattern to remember for talking about increases and decreases.

No. In Spanish, adjectives normally come after the noun, especially descriptive ones like bifocal:

• la lente bifocal ✅
• la bifocal lente ❌

Placing an adjective before the noun is only possible in certain cases and often changes tone or meaning, but with a technical adjective like bifocal, the normal position is after the noun.