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Above a certain luminance level (about 0.03 cd/m 2), the cone mechanism is involved in mediating vision; photopic vision. Below this level, the rod mechanism comes into play providing scotopic (night) vision. The range where two mechanisms are working together is called the mesopic range, as there is not an abrupt transition between the two ...
This is a red pigment seen at the back of the eye in animals that have a white background to their eye called Tapetum lucidum. The pigment is not noticeable under photopic and mesopic conditions. The principle that the wavelength sensitivity does not change during scotopic vision led to the ability to detect two functional cone classes in ...
Scanning laser ophthalmoscopy developed as a method to view a distinct layer of the living eye at the microscopic level. The use of confocal methods to diminish extra light by focusing detected light through a small pinhole made possible the imaging of individual layers of the retina with greater distinction than ever before. [4]
A Marcus Gunn pupil indicates an afferent defect, usually at the level of the retina or optic nerve. Moving a bright light from the unaffected eye to the affected eye would cause both eyes to dilate, because the ability to perceive the bright light is diminished. Specialty: Ophthalmology, Optometry
The pupil of the eye dilates in the dark to enhance night vision. Shown here is a pupil of an adult naturally dilated to 9 mm in diameter in mesopic light levels. The average human eye is not able to dilate to this extent without the use of mydriatics. Nocturnal mammals have rods with unique properties that make enhanced night vision possible.
Colour, where the retina is illuminated by white light and examined in full colour. Red free fundus photography utilizes a filter in order to better observe superficial lesions and some vascular abnormalities within the retina and surrounding tissue. A green filter ~540–570 nm is used to block out red wavelengths of light.
A red cone would excite the red/green ganglion cell and the green cone would inhibit the red/green ganglion cell. This is an opponent process. If the rate of firing of a red/green ganglion cell is increased, the brain would know that the light was red, if the rate was decreased, the brain would know that the color of the light was green. [44]
Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which ...