Cant you just listen to the people on the forum...you buy things your told not to, it seems you dont understand our answers. What were your water levels, and if I recall correctly you had not even cycled your tank!!!
I dont know why your harlequin died but as far as having no eye is concerned most other fish would regard any dead fish as a free lunch and the eye would be one of the first things to be eaten as its soft--yuck!!!!
Then learn to type. Go back to school. Did you do research on your fish before you got it? Was your tank cycled? Do you know what type of food to feed it?