One of the potential long-term effects of radiation exposure is the development of cataracts. Cataracts are a deterministic effect of radiation exposure, meaning that there is a threshold dose below which you would not expect to see cataracts, and above which you would. The severity of the cataract would then increase with increasing exposure.
The International Commission on Radiological Protection (ICRP) has recently updated its estimate on the threshold dose, decreasing it to 500 mGy to the lens of the eye, and now recommends an equivalent dose limit for the lens of the eye of no more than 50 mSv in a single year, and no more than 100 mSv in a defined 5 year period.
For more information on radiation induced cataracts, visit the IAEA Cataract Study.