Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In addition, bone marrow transplant retinopathy can mimic radiation retinopathy, and it is not possible to distinguish the 2 retinopathies unless affected patients have a history of exposure to one (eg, radiation) and not the other (eg, bone marrow transplantation); the same predicament occurs with the coexistence of diabetic retinopathy and radiation retinopathy.(8) Diseases and treatment complications that mimic radiation retinopathy may be additive, with resultant worse radiation retinopathy than would have been the case without the systemic disease (eg, diabetes mellitus) or treatment (eg, chemotherapy).
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