A RARE but severe form of corneal ulcer which may eventually lead to blindness appears to have claimed its second victim, raising fears of more to come. This comes within weeks of the diagnosis of Hong Kong's first case of acanthamoeba keratitis, a condition that mainly affects contact lens wearers. Doctors are awaiting results of the latest test to determine whether a free-living amoeba is the cause of redness, irritation and a drop in vision in a patient, according to Professor Arthur Li Kwok-cheung, medical dean of the Chinese University. Dr Dennis Lam, a lecturer in ophthalmology, who diagnosed the first case, called on contact lens wearers to handle their lenses properly. He said the public could be worried by the possible new case but said the disease, although a very serious form of cornea infection, was preventable. The first patient, who has been wearing soft contact lens for 10 years, is believed to have contracted the disease when she mistakenly used saline solution to disinfect her lenses. A minor cut near her eye is suspected to have lowered her resistance. ''What is important is proper care and proper after-care,'' Dr Lam said. ''If a wearer has a full understanding of the instructions, knows and follows the disinfecting procedure, stores the lenses in a clean environment, he should be very safe.''