À force de passer chez l’opticien, Paul finit par choisir des lunettes plus légères.

À force de + infinitive means something like by repeatedly doing, through doing something over and over, or as a result of doing something so much.

In this sentence, À force de passer chez l’opticien suggests that Paul kept going to the optician repeatedly, and this repeated action eventually led to the result in the main clause.

It often implies persistence, repetition, or even a kind of accumulated effect.

Examples:

• À force d’essayer, elle a réussi.
  By trying again and again, she succeeded.
• À force de discuter, ils ont trouvé une solution.
  After discussing it over and over, they found a solution.

Because à force de is followed by an infinitive.

So the pattern is:

à force de + infinitive

Here:

• passer = to go / to stop by / to visit
• de passer = of going / by going repeatedly

You do not say à force il passe in this structure. The infinitive is required after de.

Here, passer chez l’opticien means to go to the optician’s place, often with the sense of stopping by, dropping in, or going there repeatedly.

The verb passer can have several meanings in French, and one common one is to stop by or to go by someone’s place.

So:

• passer chez le médecin = to go by the doctor’s / stop in at the doctor’s
• passer chez un ami = to stop by a friend’s place

In this sentence, it does not mean simply to pass in front of the optician’s shop. It means he keeps going there.

Chez is often used before a person, profession, or the place associated with that person.

So:

• chez le médecin = at the doctor’s / to the doctor’s
• chez le boulanger = at the baker’s / to the baker’s
• chez l’opticien = at the optician’s / to the optician’s

French uses chez where English often uses to or at plus a profession.

So even though opticien is a person or profession, chez l’opticien can refer to the shop or place where that person works.

Finir par + infinitive means to end up doing something or to finally do something after some delay, hesitation, or process.

So:

• Paul finit par choisir... = Paul ends up choosing... / Paul finally chooses...

This expression often suggests that the action was not immediate. Something happened first—here, repeated visits to the optician—and only after that did the final action occur.

Examples:

• Il finit par comprendre.
  He finally understands / He ends up understanding.
• Nous avons fini par accepter.
  We finally accepted / We ended up accepting.

Because finir par is a fixed expression.

You should learn it as a whole pattern:

finir par + infinitive

It does not literally translate word for word in a natural way. The par is just part of the construction.

Compare:

• Il finit son travail. = He finishes his work.
  Here finir means simply to finish something.
• Il finit par partir. = He ends up leaving / He finally leaves.
  Here finir par means to eventually do something.

So in your sentence, finit par choisir is not the same as simply finit choisir, which would not be correct.

Because after finir par, the next verb stays in the infinitive.

Pattern:

• finir par + infinitive

So:

• finit par choisir
• finit par comprendre
• finit par accepter

This is very common in French: one conjugated verb is followed by another verb in the infinitive.

In French, lunettes is normally plural when it means glasses or eyeglasses, just like glasses in English is usually plural.

So:

• des lunettes = glasses
• une lunette usually means something different, such as a lens, a spyglass, or part of a device depending on context

If you mean the thing you wear on your face to see better, French normally uses the plural: les lunettes.

Because légères agrees with lunettes, which is:

• plural
• feminine

So the adjective must also be:

• plural
• feminine

Forms of léger:

• léger = masculine singular
• légère = feminine singular
• légers = masculine plural
• légères = feminine plural

Since lunettes is feminine plural, we get plus légères.

Yes. Plus légères means lighter.

This is the comparative form:

• léger / légère = light
• plus léger / plus légère = lighter

French does not always need to state the second half of the comparison explicitly. The comparison can be understood from context.

So des lunettes plus légères means:

• lighter glasses
• glasses that are lighter than the ones he had before, or lighter than other options

The comparison target is implied rather than stated.

The part À force de passer chez l’opticien is an introductory phrase that sets up the cause or background for what follows.

The comma helps separate that introductory element from the main clause:

• À force de passer chez l’opticien,
• Paul finit par choisir des lunettes plus légères.

In English, you would often do the same with an introductory phrase.

The comma is mainly about clarity and rhythm. It is very natural here.

Yes, several rephrasings are possible, though they may sound slightly different in tone or emphasis.

For example:

• Après être passé plusieurs fois chez l’opticien, Paul a fini par choisir des lunettes plus légères.
  After going to the optician several times, Paul finally chose lighter glasses.
• À force d’aller chez l’opticien, Paul a fini par choisir des lunettes plus légères.
  By going to the optician again and again, Paul ended up choosing lighter glasses.

Your original sentence is quite natural and elegant because à force de nicely conveys repetition leading to a result.

Yes, finit is present tense.

French often uses the present tense to state something generally, vividly, or as part of a narrative-style sentence. Depending on context, it may describe:

• a general truth,
• a habitual pattern,
• or a narrated event in a lively way.

So Paul finit par choisir is grammatically present, but in some contexts English might naturally translate it with ended up choosing if the overall situation is understood as past.

If you wanted an explicitly past version in French, you could say:

• Paul a fini par choisir des lunettes plus légères.

That would clearly place the event in the past.