In a motor vehicle accident case, is there any evidence that injuries to the eye impaired the ability to identify the accident scene?

In the instant case, there was no evidence in the record, either from Barrientos himself or from experts, that Barrientos's injuries impaired his ability to observe. Nor was there evidence of studies on eyewitness identification which would support the proposed instructions even if they were not argumentative. An instruction should not be given where no evidence exists on the issue. (People v. Wittig (1984) 158 Cal.App.3d 124, 131, 204 Cal.Rptr. 378.)