This is what we found on Wikipedia regarding the London Eye Same Day Entry Ticket:

The Oyster card is a payment method for public transport in London and some surrounding areas. A standard Oyster card is a blue credit-card-sized stored-value contactless smart card. It is promoted by Transport for London (TfL) and can be used as part of London's integrated transport network on travel modes including London Buses, London Underground, the Docklands Light Railway (DLR), London Overground, Tramlink, some river boat services, and most of the National Rail services within the London fare zones. Since its introduction in June 2003, more than 86 million cards have been used.

Oyster cards can hold period tickets, travel permits and, most commonly, credit for travel ("Pay as you go"), which must be added to the card before travel. Passengers touch it on an electronic reader when entering – and in some cases when leaving – the transport system in order to validate it, and where relevant, deduct funds from the stored credit. Cards may be "topped-up" by continuous payment authority, by online purchase, at credit card terminals or by cash; the latter two methods are available at stations and convenience stores. The card is designed to reduce the number of transactions at ticket offices and the number of paper tickets. Cash payment has not been accepted on London buses since 2014.

The card was first issued to the public on 30 June 2003, with a limited range of features; further functions were rolled out over time. By June 2012, over 43 million Oyster cards had been issued and more than 80% of all journeys on public transport in London were made using the card.

From September 2007 to 2010, the Oyster card functionality was tried as an experiment on Barclaycard contactless bank cards. Since 2014, the use of Oyster cards has been supplemented by contactless credit and debit cards as part of TfL's "Future Ticketing Programme". TfL was one of the first public transport providers in the world to accept payment by contactless bank cards (after, in Europe, the tramways and buses of Nice, which started accepting NFC bank cards and smartphones on 21 May 2010), the widespread adoption of contactless in London has been credited to this. TfL is now one of Europe's largest contactless merchants, with around 1 in 10 contactless transactions in the UK taking place on the TfL network in 2016.