![]() ![]() Pupillography may be the only reliable method of diagnosis for dilation lag in bilateral Horner's syndrome (where the relative anisocoria is obscured by bilaterality). Infrared light provides optimal visualization of the dilation dynamics, and pupillography can accurately measure the dilation speed and difference in dilation between the pupils. The dilation of the pupil in the Horner's syndrome can take up to 15-20 seconds (i.e., dilation lag) compared to 5 seconds in normal individuals. Dilation lag is a characteristic feature of oculosympathetic denervation (i.e., the Horner's syndrome). ![]() Dilation LagĪdditionally, pupillography can be used to measure dilation lag, which refers to the delayed relaxation-dilation of the pupil when the light is withdrawn. Pupillographic investigation of RAPD may also help assess for less common afferent pupillary pathway lesions in the midbrain and tectum (e.g., tectal RAPD). In a patient with head trauma, the RAPD may be the only sign of traumatic optic nerve injury and pupillography might be useful to assess the afferent pupillary pathway in a comatose trauma patient. The RAPD is seen in many different ocular diseases that can affect the afferent pupillary pathway (e.g., diffuse retinopathy, optic neuropathy, optic tract lesions and pretectal lesions). Pupillography also provides a standardized, quantifiable, and reproducible way of measuring the relative afferent pupillary defect (RAPD) compared to the conventional swinging flashlight test performed by a clinician. Relative afferent pupillary defect (RAPD) In fact, it has already been shown to correlate with measurements of visual acuity but is currently limited to use in research settings due to the small amplitude of pupillary responses and the need for repeated measurements However, the secondary reflex has a longer latency, and thus may have potential use as an objective indicator of visual acuity. Both reflexes are mediated by the same retino-cortical pathway, the afferent arm of which is also involved in visual perception. ![]() chromatic and achromatic gratings, coherent motion set) has also been documented. While the classic pupillary light reflex is luminance-driven, a secondary reflex involving pupillary constriction to isoluminous stimuli (e.g. Pupillography might be used to give an approximation of visual acuity in settings where patients cannot (e.g., nonverbal) or will not (e.g., nonorganic) provide the information using subjective assessments. Because of this double decussation, first in the chiasm and then in the pretectal and Edinger-Westphal nuclei, the direct pupil response in the left eye is equivalent to the indirect consensual response in the right eye. CN III acts on the iris sphincter muscles, causing both pupils to contract. These impulses stimulate the pretectal nuclei which then stimulate both Edinger Westphal nuclei of CN III. Light stimulating the left retina generates impulses that travel down the left optic nerve and divide at the optic chiasm, where some impulses continue down the left optic tract and others cross over to the right optic tract. The solid line represents the afferent pupillary pathway and the dotted line represents the efferent pupillary pathway. Pupillary afferent and efferent pathways. It is also useful for obtaining exact measurements of the pupil during preparation for certain ophthalmic procedures. Thus, pupillography is a useful tool for studying, identifying, and treating the underlying stimuli and causes of certain pupillary reactions. This pupil pathway (afferent and efferent) can be affected by a diverse set of stimuli including changes in retinal luminance, sudden changes in stimulus motion, and emotional and cognitive factors. The pupillary afferent pathway starts at the retina, travels through the optic nerve, then goes through the optic chiasm and optic tract to reach the pretectal nucleus, where it communicates anteriorly with the Edinger Westphal nucleus that is in charge of the efferent pupillary pathway ( Figure 1). Infrared video camera and using computer software to analyze the images ( Video 1). Pupillography is a formal method of recording and measuring reactions of the pupil often by using an
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |