1 / 12

Physiological-clinical importance of the eye.

Prof. James Ker explores the intricate visual system, from image capture in the retina to neural pathways, clinical implications, and systemic diseases affecting the eye. Learn about the physiology and clinical relevance of the eye.

lave
Download Presentation

Physiological-clinical importance of the eye.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physiological-clinical importance of the eye. Prof James Ker MBChB, MMED, MRCP, FRCP, PhD, FESC, FACC, L.Akad.SA 2012

  2. Physiological purpose of the visual system: • The visual system provides a supremely efficient means for the rapid assimilation of information from the environment to aid in the guidance of behavior.

  3. The act of seeing: • Begins with the capture of images focused by the cornea and lens upon the retina. • Retina—a light sensitive membrane in the back of the eye. Actually a part of the brain, banished to the periphery to serve as a transducer for the conversion of patterns of light energy into neuronal signals.

  4. Light is absorbed by photopigment in 2 types of receptore: Rods and cones. • 100 million rods • 5 million cones • The rods operate in dim conditions and the cones under daylight conditions

  5. The cones is specialized for color perception and high spatial resolution. • The majority of cones are located in the macula, the portion of the retina serving the central 10 degrees of vision.

  6. The fovea: • This is a small pit in the middle of the macula, packed exclusively with cones and provides the best visual acuity. • Photoreceptors hyperpolarize in response to light and activates bipolar, amacrine and horizontal cells in the inner nuclear layer.

  7. The flow of sensory information converges upon a final common pathway: the ganglion cells. • The ganglion cells translate these into action potentials that propagates along the primary optic pathway to visual centers in the brain.

  8. There are a million ganglion cells in each retina and thus a million fibers in each optic nerve. • The majority of fibers synapse upon cells in the lateral geniculate body, a thalamic relay station. Cells from the lateral geniculate body then projects to the visual cortex.

  9. This massive retinogeniculocortical sensory pathway provides the neural pathway for visual perception. • The lateral geniculate body is the main target of the retina, however some gangion cells project to other subcortical visual nuclei , involved in different functions.

  10. These include: • Pupillary reflexes • Circadian rhythms • Visual orientation and eye movements

  11. Clinical importance: • Primary disease processes affecting the eye • Systemic disease assessment: Hypertension and diabetes, vasculitis • Hypertension: hard/soft exudates • Cardiac disease: Infective endocarditis • Roth Spots • Hypercholesterolemia • Arcus cornealis; Hollenhorst plaque • Brainstem disorders • Skew deviation • Drug intoxications • Morphine: miosis • Optic neuritis: Toxins (ethambutol, methanol) • Pallor of disc • Optic neuritis due to MS

  12. Intracranial hypertension • Papilloedema • Without hypertension: Hypercarbia • Primary metabolic disorders, such as Wilson`s disease: Kayser-Fleischer ring • Copper deposition around eyes • Circadian rhythm implications for the blind • Endocrinopathy: hormone disturbances: cortisol & GH

More Related