[Music] prison reflex test pbrt first described by krimsky has become universally accepted as a practical method of estimating the size of the angle of screen in patient with a blind or deeply unlikely eye with or without centric fixation required instruments prism bar or loose prisms pen torch optical principle the optical principle is different to the prism reflection test as the prism is placed before the fixing eye and the fixing eye moves to overcome the prism and maintain fixation in the primary position because of firing's law each eye will make a conjugate movement of the same
amount if an increasing prism strength is placed before the fixing eye this will centralize the corneal reflection of the deviating eye procedure to perform the test patient is asked to fixate on a point light and prisms of increasing strength with effects toward the direction of manifest screen are placed in front of the normal fixating eye till the corneal reflex is centered in the squinting eye the power of prism required to center the light reflex in the squinting eye equals the amount of screen in prism diapers to avoid errors from parallax the examiner must observe the
corneal reflex with one eye by sitting directly in front of the deviating eye while keeping his other eye closed recording pbrt with without glasses 35 prism base out fixing right advantages of krimsky test since the test requires only that the patient fixate the light being entirely objective otherwise it is useful in testing small children it is quicker to perform than the prism cover test it can be used in patients in whom the deviating eye has a low visual activity or has lost central fixation limitations of the krimsky test since the angle kappa is included in
the measurement the test is inaccurate it is impossible to perform the test for distance fixation since the position of the examiner's head requires to obtain an accurate observation prevent the patient from seeing the fixation light [Music] so [Music] me [Music] kindly subscribe the channel and press the bell icon thank you for watching
