Because of the proximity of the human eye when a cell phone is used, there has been concern about the effect of the radiofrequency radiation (RFR) on the visual system. Irlenbusch (2007) investigated the visual discrimination threshold to assess this potential impact of RFR, and found no effect of RFR exposure compared with sham exposure.

Authors
Irlenbusch L, Bartsch B, Cooper J, Herget I, et al.
Title
Influence of a 902.4MHz GSM signal on the human visual system: Investigation of the discrimination threshold.
Journal
Bioelectromagnetics 2007;28:648-654.
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Authors
Küçer N (2008): 
Title
Some ocular symptoms experienced by users of mobile phones.
Journal
Electromagn Biol Med. 27(2):205-9.