Does My Toddler Have Epilepsy?

My son is 20 months old and I have noticed that he has episodes were he stands stiff, his eyes flick back and he shudders his arms and grits his teeth, this only lasts a second or two and he stays on his feet. My mams friend who has a child with epilepsy saw this for the first time and says she thinks it is absenses. He had a troubled birth and a ventouse delivery, then had low blood sugar so was in special care as a baby. There is no family history of epilepsy and I am worried about the absenses developing into something worse, can a doctor diagnose this without seeing it?? Any help please!