Review of anatomy & physiology of the Retina
description
Transcript of Review of anatomy & physiology of the Retina
![Page 1: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/1.jpg)
Review of anatomy & physiology of the
Retina
Dr. Ayesha Abdullah14.12.2012
![Page 2: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/2.jpg)
Learning outcomes
By the end of this lecture the students would be able to;
• Correlate the structural organization of the retina with its functions and development.
• Identify structural landmarks on retinal photographs.
• Name the investigations commonly employed for the assessment of retinal disorders.
![Page 3: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/3.jpg)
Some questions • How do we see?• What are the similarities and differences between a camera and the
eye?• Name part of the nervous system that can be visualized without any
invasive procedure? • Why is the optic disc referred to as the blind spot?• Have you noticed tiny bright moving dots when looking into the
blue sky?• If the photoreceptor had been anteriorly placed, what would have
happened?• How do we know its day/ night?• How does the brain regulate circadian rhythms?
![Page 4: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/4.jpg)
Camera and the eye
![Page 5: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/5.jpg)
• Unlike the image from a camera the resolution of the retinal image is not uniform.
• Why?• What is the result?• There are about 100 times more photoreceptors than the Ganglion cells.• Retina compresses images as unlike the camera.
![Page 6: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/6.jpg)
Anatomical landmarks of the retina
![Page 7: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/7.jpg)
![Page 8: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/8.jpg)
![Page 9: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/9.jpg)
Normal dimensionsAnatomical characteristics Clinically Observable
characteristics Optic disc Place where the optic nerve fibers leave
the retina. It is devoid of rods and cones hence the blind spot. Contains the central retinal artery and vein
It’s a pale disc like structure with vessels emerging out of its center called the cup. Its about 1.5 mm in size.
Macula It is the area where the ganglion cells are two layered. Contains the xanthophyl pigment giving it the pigmented look.
It is about 5.5 mm in diameter (3.5 disc diameter/ 180 of visual angle). Roughly the area between the arterial arcades.
Fovea
Foveola
A depression in the inner retinal surface. It contains cones only.The inner nuclear layer and the ganglion cell layer is absent.
A concave central retinal depression about the same size as the disc (1.5mm)
Parafovea The thickest part of the retina Area surrounding the fovea
![Page 10: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/10.jpg)
![Page 11: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/11.jpg)
![Page 12: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/12.jpg)
![Page 13: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/13.jpg)
![Page 14: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/14.jpg)
Histological structure of the retina
![Page 15: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/15.jpg)
![Page 16: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/16.jpg)
![Page 17: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/17.jpg)
Development of the retina
![Page 18: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/18.jpg)
Functions of the retina
• Light perception• Brightness appreciation• Contrast sensitivity • Two point discrimination and appreciation of
details• Colour perception• Light and dark adaptation • Circadian rhythms & hormonal balance
![Page 19: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/19.jpg)
Some important facts• There are about 150 million receptors and only 1 million optic nerve fibers,
there must be convergence and thus mixing of signals• The horizontal action of the horizontal and amacrine cells can allow one area
of the retina to control another (e.g., one stimulus inhibiting another). This inhibition is key to the sum of messages sent to the higher centers of the brain.
• The response of cones to various wavelengths of light is called their spectral sensitivity
• There are blue, green, and red cones but more accurately short, medium, and long wavelength sensitive cone subgroups- trichromatic vision
• The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron
• The receptive field of a Ganglion cell in the retina of the eye is composed of input from all of the photoreceptors which synapse with it, and a group of ganglion cells in turn forms the receptive field for a cell in the brain. This process is called convergence.
![Page 20: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/20.jpg)
vitreous
RPE
![Page 21: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/21.jpg)
![Page 22: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/22.jpg)
![Page 23: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/23.jpg)
Rods & Cones
• Rod System– Achromatic– High convergence– High light sensitivity– Low visual acuity
• Cone System– Chromatic– Low convergence– Low light sensitivity– High visual acuity
![Page 24: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/24.jpg)
Direction of visual impulse
Direction of light
![Page 25: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/25.jpg)
![Page 26: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/26.jpg)
Investigations for retinal structural and functional assessment
• Clinical assessment- Ophthalmoscopy
![Page 27: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/27.jpg)
Ophthalmic investigations
• Ultrasound –B & A scans• Ocular coherence tomography (OCT)• Angiography • Elctroretinogram • Elctro-oculogram
![Page 28: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/28.jpg)
![Page 29: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/29.jpg)
OCT
![Page 30: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/30.jpg)
Angiography
![Page 31: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/31.jpg)
Electroretinogram
![Page 32: Review of anatomy & physiology of the Retina](https://reader036.fdocuments.us/reader036/viewer/2022081505/568164d8550346895dd71d02/html5/thumbnails/32.jpg)
Homework
• What is the blood supply of the inner and outer retinal layers?
• What makes the inner and outer retinal blood barriers and what is their significance?
• E mail me at, the answer should not more than 04 lines.