I suppose that it is possible to be allergic to almost anything. There are many brands and models of intraocular lenses used in cataract surgery today. Most of these IOLs are made of one of about four different materials (silicone, hydrophobic acrylic, hydrophilic acrylic, and PMMA).
Your ophthalmologist (eye doctor) will review your known allergies with you during your comprehensive medical eye examination and will avoid using intraocular lenses made of materials that you might be allergic to. In practice, however, I am not aware of any case of allergy to the material in any intraocular lens.