Brief Answer:
Mostly irritation by contact lence.

Detailed Answer:
Hi XXXXXXX
Thanks for the query.I have read it&also seen the picture sent
*It's a clean eye swelling without any excessive discharge ,redness ,pain,itching or fever.
* Swelling of eye can be due to-
-Stress / irritation.to eye...untreated refractory error, forgein body in eye...may be contact lence in your case/trauma to eye or surrounding area/.over use etc...has dull ache,swelling /uneasiness / can affect vision too.
-Allergy of some drug,eatable,ointment or forgein body(dust,contact lence..in your case)/Generelised allergy .Here dominent symptom is ..itching&swelling of complete eye.
-Infection of eye or eye lid...accompanied by fever,pain,swelling& increased secretions in eye.
-Some systemic diseases like kidney ,heart or liver disease,low thyroid ..accompanied by all over swelling with pitting edema on leg.
* looking at the symptoms you have described..I doubt it to be due to irritation by contact lence itself
-Try removing the lence.
-Use ice pack for few seconds...repeat if needful
-Put steroid eye drops over the counter
twice a day
-Visit your opthalmologist for checking the contact lence& excluding any trauma caused by it.
I hope that helps.Any follow up query is welcome.
Thanks.

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