Safety experts said this week there was no evidence that interactive whiteboards and projectors were damaging teachers' eyesight.
Although there are around 200,000 whiteboards in schools in England and thousands in Wales, the Health and Safety Executive said it found no cases where the technology had affected teachers' vision.
It said any theoretical risk was low but teachers' unions have called on the Government to give school staff clearer health and safety guidance on the equipment amid concerns that exposure could damage their eyes.
The Times revealed details of research carried out when workers from Selectasize Visual Aids complained that they had been "seeing stars" after installing the interactive boards in schools.
The National Radiological Protection Board said it was unlikely that children or teachers would be at risk from the boards, provided they followed basic safety guidelines.
Steve Walker, principal specialist inspector, told the HSE that if a person looked directly into the projector's beam for more than 20 seconds they could damage their retina.
There was a possibility that teachers' eyesight could be affected when they were not staring directly at the projector. "There remains a possibility that a viewer's peripheral retina could be overexposed even when he or she is not staring at the projector's apparent source," he said.
Neither the HSE nor the British Educational Communications and Technology Agency, which has issued safety guidance on the boards, said they had any proof the technology had affected teachers' eyesight.
Mark Wallbank, assistant director of procurement at Becta, said that interactive whiteboards had been used in schools since the late 1990s and data projectors for several years longer.
"If teachers had been affected we would have heard about it by now," he said.
Mr Wallbank said teachers had to use common sense about how often they employed technology as they faced other risks, such as developing repetitive strain injury from typing on laptops.
Russell Ingelby, chairman of the Association for ICT in Education which represents ICT teachers, said teachers were probably in greater danger of injuring themselves by tripping over the projectors' cables.
The National Union of Teachers and Secondary Heads Association said that too few staff appeared aware of the basic safety precautions, and urged the DfES to make them clearer.
Becta acknowledged that, although suppliers provided health and safety advice with the boards, there were no systems in place to ensure that guidance reached teaching staff.