BLINDNESS UNILATERAL; RETINAL VEIN OCCLUSION; ANTICOAGULANT THERAPY; COAGULATION TEST ABNORMAL; FACTOR V LEIDEN MUTATION; RETINAL VEIN THROMBOSIS; SUSPECTED COVID-19; This spontaneous report received from a health care professional by a Regulatory Authority, VAERS (Vaccine Adverse Event Reporting System) concerned a 23 year old male of an unspecified race and ethnicity. The patient's height and weight were not reported. The patient's past medical history included: keratoconus had surgery on 21-MAY-2021. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, intramuscular, batch number: Unknown, and expiry: Unknown) dose was not reported, 1 in total was administered to right arm on 24-MAY-2021 for an unspecified indication. Age at time of vaccination 23 years old. The batch number was not reported. The Company is unable to perform follow-up to request batch/lot numbers. No concomitant medications were reported. On 05-JAN-2022, the patient believed to have had mild case of COVID-19 (suspected covid-19) and mentioned that no testing was done to confirm. It was reported that on 09-MAR-2022, the patient had vision loss on right eye (blindness unilateral) and seen a retinal specialist and it was identified that the patient had central retinal vein thrombus and occlusion (retinal vein occlusion, retinal vein thrombosis). The patient was treated with ASA (acetylsalicylic acid) 81milligrams, and avastin intraorbit injections. It was reported that the patient was seen by a hematologist and coagulation workup (coagulation test) revealed Factor-V Leiden heterozygote (factor v leiden mutation), no other coagulation abnormalities or other thrombotic risk factors were identified and the patient was continued to be seen by retinal specialist and hematologist. It was mentioned that Xarelto was initiated immediately (anticoagulant therapy). On 09-MAR-2022, laboratory data included: Coagulation test (NR: not provided) abnormal. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from anticoagulant therapy, blindness unilateral, coagulation test abnormal, factor v leiden mutation, retinal vein occlusion, retinal vein thrombosis, and suspected covid-19. This report was serious (Other Medically Important Condition). This report was associated with a product quality complaint: 90000233672. The suspected product quality complaint has been confirmed to be the reported allegation could not be determined a manufacturing related root cause could not be identified. based on the PQC evaluation/investigation performed.  Additional information received was from the department on 06-JUN-2022. The following information was updated and incorporated into the case narrative: Product quality complaint investigation result.; Sender's Comments: V1: This follow up adds information about  Product quality complaint investigation result. This does not alter previous causality assessment of the reported events.   20220559684-COVID-19 VACCINE AD26.COV2.S- BLINDNESS UNILATERAL, RETINAL VEIN OCCLUSION. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s). Therefore, this event(s) is considered unassessable.