Modern cataract surgery involves breaking up the lens into small pieces (phacoemulsification) and removing those pieces using suction. Sometimes, a piece of lens material falls into the back of the eye during cataract surgery. It is usually unsafe for the cataract surgeon to remove lens pieces that fall posteriorly into the eye. A retina surgeon can remove those pieces of lens if necessary. The lens is immunopriviledged. That means that your immune system never sees the inside of your lens. So when a piece of lens material drops into the eye, within a short time, your body mounts an immune response to that material just like it would a foreign body. Consequently, the eye can become inflamed and the intraocular pressure can rise.
About one percent of cataract surgeries result in retained lens fragments. Some lens fragments absorb and cause no trouble and others do not absorb and cause trouble. It is difficult to tell from an eye examination which fragments are good and which are bad. They all cause the patient to see floaters. In general, if they are not inciting an inflammatory response, causing macular edema or causing ocular hypertension, lens fragments can be safely observed. If, on the other hand, the lens fragments are causing elevated intraocular pressure or macular edema, they need to be removed or permanent vision loss is likely to occur.
The retina surgeon is comfortable doing surgery in the vitreous cavity where lens fragments settle. Vitrectomy involves removing the vitreous. At the same time, the lens fragments can be broken up and removed from the back of the eye. Once the lens fragments have been removed, the intraocular pressure usually normalizes right away and other problems, like inflammation, cystoid macular edema, and corneal edema, begin to resolve. Usually the vision begins to improve within a week or two.
This video shows how scleral depression is essential to removing all of the lens fragments from an eye, especially when there is time between the cataract surgery and the vitrectomy. This 77 year old man had high intraocular pressures. The posterior lens material looked like just cortex (which is usually tolerated). Examination of the peripheral retina – especially the inferior retina, showed nuclear fragments.
This video shows the removal of lens fragments from an eye with iris fixation of the intraocular lens. The patient regained normal vision within about 1 month of the surgery with no complications. Lens fragment surgery is sometimes necessary following cataract surgery if lens material enters the posterior pole – vitreous – of the eye during cataract extraction.