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

We evaluated the effects of intravitreal injection of methanol. formaldehyd e. or formate on rabbit eyes. One hundred mul of 1% methanol, 1% or 0.1% fo rmaldehyde, 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 h istologically. One week after treatment the animals that received 0.1% form aldehyde showed retinal vessel dilation, and the rabbits that received 1% f ormaldehyde showed mild posterior subcapsular cataract and retinal vessel d ilation and haemorrhages. One month after treatment, the animals that recei ved 0.1% or 1% formaldehyde developed mild posterior subcapsular cataract a nd retinal lesions. Animals that received 1% methanol or 1% formate showed nearly normal optical media and fundi. Histologically disorganized retina a nd optic nerve were seen in eyes that received 0.1% or 1% formaldehyde. Eye s that received 1% methanol or 1% formate appeared histologically normal. O ur findings indicate that intravitreal injection of formaldehyde causes ret inal and optic nerve damage, while methanol and formate are not or less tox ic to ocular tissues.