Ocular changes after intravitreal injection of methanol, formaldehyde, or formate in rabbits

We evaluated the effects of intravitreal injection of methanol, formaldehyde, or formate on rabbit eyes. One hundred microl of 1% methanol, 1% or 0.1% formaldehyde, or 1% formate was injected in the vitreous cavity of the right eyes of rabbits. The eyes were examined by biomicroscopy and ophthalmoscopy weekly. One month after injection, the eyes were enucleated and examined histologically. One week after treatment the animals that received 0.1% formaldehyde showed retinal vessel dilation, and the rabbits that received 1% formaldehyde showed mild posterior subcapsular cataract and retinal vessel dilation and haemorrhages. One month after treatment, the animals that received 0.1% or 1% formaldehyde developed mild posterior subcapsular cataract and retinal lesions. Animals that received 1% methanol or 1% formate showed nearly normal optical media and fundi. Histologically disorganized retina and optic nerve were seen in eyes that received 0.1% or 1% formaldehyde. Eyes that received 1% methanol or 1% formate appeared histologically normal. Our findings indicate that intravitreal injection of formaldehyde causes retinal and optic nerve damage, while methanol and formate are not or less toxic to ocular tissues.