Did Grand Theft Auto Sin City Lance really betray Tommy because of an eye disease?

The reason why Lance and Tommy are together is for profit: Lance and Tommy cooperated in investigating Diaz before hitting Diaz. At the beginning of the new gang, Tommy needed Lance to gather people who belonged to the Vance family before (Ken was responsible for Tommy's legal inheritance of Diaz's mansion, and Eli Carrington was responsible for providing Tommy with information about the city's real estate, not to mention Tommy). When the gang reached a certain scale, Lance began to have friction because of the uneven distribution of Tommy's stolen goods (see the phone call in the middle and late game), so Lance and Tommy finally broke up for profit. At this time, Sonny extended an olive branch to Tommy (presumably to let Lance control the evil business), which led Lance to make up his mind to break with Tommy.