Color Vision and Eye movement

Transcript

2. Lectured by Dr Sadatinejad, Seyyed Mohsen,student of Medicine from Iran,Kashan 19/12/2012
3. Blind spot Although the cone pigments have maximum efficiency closer to violet, green, and yellow wavelengths, they are referred to as blue, green, and red pigments, respectively
4. Short-wave pigment Middle-wave pigment Long-wave pigment
5. A single photon of light can activate a rod, whereas several hundred photons are required to activate a cone. Types of photopigments: Blue,Green,Red(Yellow) photopigmment
6. Additive color mixing Subtractive color mixing
8. Primetric field
9. Ganglion cells Type 1: respond to a broad band of wavelengths. In other words, they receive input from all three types of cones, and they signal not specific color but general brightness. Type 2: code specific colors. Type 3: opponent color cells
10. Type 3: opponent color cells excitatory input from one type of cone receptor and an inhibitory input from another
11. ganglion cells → lateral geniculate nucleus → Neural pathways to V1: red–green pathway (signals of L- and M-cone responses) blue–yellow pathway (signals of S-cone and the sum of L- and M-cone responses) luminance pathway (signals of sum of L- and M-cone responses) → blobs , deep portion of layer 4C of V1 → V8 → sensation of color
12. Color Blinding (Daltonism)
14. No Red No Green No Blue
15. Trichromats Dichromats : 3 types : •Protanopia •Deuteranopia •Tritanopia. The prefixes "prot-," "deuter-," and "trit-" refer to defects of the red, green, and blue cone systems Monochromats
16. • Red-Green Color Blindness • Blue Weakness
18. Eye Special Movement
20.  1) Saccades ◦ If an image appears to the side, eye movements called saccades rotate both eyes so that the image now falls on the fovea. Likewise saccades are used to point the fovea at each word in this sentence.  2) Vergence ◦ If you look (i.e. direct the foveas) from a far object to a near one, vergence eye movements are generated; convergence when looked from far to near and divergence when looking from near to far.  3) Pursuit ◦ When an object that we are looking at moves, the image is kept still on the retina by means of a pursuit eye movement (e.g. tracking a ball or your moving finger).
21.  4) Vestibular ocular reflex (VOR) ◦ If we rotate our head, an eye movement very similar to pursuit is elicited whose function is also to keep the image still on the retina. it is generated by a different neural circuit, the VOR. The VOR does not need a visual stimulus.  5) Optokinetic Reflex (OKR) ◦ The VOR does not work well for slow prolonged movements. In this case vision, through the OKR, assists the VOR. The OKR is activated when the image of the world slips on a large portion of the retina and produces a sense of self motion If an image appears to the side, eye movements called saccades rotate both eyes so that the image now falls on the fovea. 6) Nystagmus 7)sacalic