How does an FSA (Flexible Spending Account) differ from an HSA (Health Savings Account)?

FSA and HSA accounts are both pre-tax accounts that can be used for LASIK.  FSA accounts are generally linked to traditional health plans and HSA accounts are generally linked to high-deductible plans.  HSA accounts have a perpetual carry-over so that money left over from one year can carry forward and be used to cover future year expenses.