Many people who have a stem cell or bone marrow transplant have total body irradiation [TBI] as well as chemotherapy to wipe out their own marrow in preparation for their donor's bone marrow. TBI involves doses of radiation, often given over several days, to the whole body. Lead shields are used to protect some important fragile organs like the lungs. But other tissues like the eye unavoidably receive some radiation during TBI. This radiation can have the long-term side effect of causing cataracts (misting or clouding of the lens of the eye) many months or years after treatment.
 
People usually  notice the cataracts themselves. They find  that their eyesight gets worse or that bright lights begin to dazzle them. But sometimes cataracts start to develop without the person noticing and can only be picked up by examination by an optician or a doctor who specialises in eye diseases (ophthalmologist). This is why you need regular eye check ups if you have had TBI as part of a stem cell or bone marrow transplant.

Once they have developed, most cataracts just need to be checked at intervals. However, if they are causing a lot of problems with reading, driving or getting about they will usually need to be removed. This involves a small operation to replace the lens, which is usually done under local anaesthetic, as an outpatient or day patient.