The primary objective of the study is to characterize the clinical phenotype(s) of DUPIXENT®-associated conjunctivitis events.

The secondary objectives of the study are to characterize the course of conjunctivitis events during the observation period and collect and assess data on treatment for conjunctivitis events and its effectiveness.

Key Inclusion Criteria:

• Treatment with DUPIXENT® for AD (per the current US Prescribing Information) should be ongoing, and have been initiated at least 8 weeks prior to study enrollment. NOTE: A single missed dose in the 8 weeks prior to enrollment is allowed.
• Patients with protocol-specified conjunctivitis events must present with active bilateral conjunctivitis (with or without cornea or eyelid involvement) diagnosed by the ophthalmologist (investigator) which meets all of the following criteria:
• Developed (or significantly worsened) while receiving treatment with DUPIXENT® for AD
• Is clinically significant (eg, moderate-to-severe, extensive, persistent, etc) as determined by the investigator
• There is a suspected causal relationship between DUPIXENT® and conjunctivitis because:
• Conjunctivitis is a new-onset condition or an unusual worsening of a preexisting condition (eg, significantly more severe, more extensive, or more protracted than ever before) AND
• No alternative explanation is more plausible, in the opinion of the investigator
• Reference patients must have AD treated with current ongoing treatment with DUPIXENT® for equal or longer duration as compared to group 1, with no clinical signs of ocular inflammation noted during the entire DUPIXENT® treatment

Key Exclusion Criteria:

• Any known medical, social, or personal limitations that are likely to restrict the patient's ability to undergo study visits and complete study procedures (as assessed by the investigator), including hypersensitivity or other contraindications to the anesthetic eye drops used during the ophthalmological examination.

NOTE: Other protocol defined inclusion/exclusion criteria apply.

This study will enroll DUPIXENT®-treated patients with protocol-specified conjunctivitis events as well as reference patients with no clinical signs of conjunctivitis. Study participants will be recruited from patients being treated with DUPIXENT® for AD according to US Prescribing Information in the real-world setting, who develop conjunctivitis on treatment. These patients will be recruited with the help of a referral network of dermatologists and other physicians who treat patients with moderate-to-severe AD.