January 24th
2010

Eye Anatomy  ⁄  Retina, Macula, Fovea, Foveola

As I told you, the Dynamic Fixation Method contains three difficulty levels. Last year we finished level one for beginners. Now we start intermediate study with level two. I will tell you various techniques for better eyesight. But first, here is some information about eye anatomy for understanding the visual techniques.

The retina is the inner layer of the eyeball, located between the choroid and the vitreous membrane. The retina contains photoreceptor cells, the rods and cones that transform light energy into a neural signal. Rods are more active in dim illumination, and cones are active in well-lit conditions.

Rods are extremely sensitive in poorly-lit conditions (scotopic vision), when cones are least responsive. In scotopic vision, the light-sensitive retina allows detection of objects at low levels of illumination. Its ability to recognize fine detail is poor, however, and color vision is absent; objects are seen in shades of gray.

Cone activity dominates in photopic vision, when the retina is responsive to a broader range of light wavelengths. Bright illumination is necessary for the sharp visual acuity and color discrimination of photopic vision. Cones are designated, depending on the wave-length that they absorb, as red (588nm), green (531nm), or blue (420nm).

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May 3rd
2009

Eye Anatomy  ⁄  Extraocular Muscles

The eyeball is situated in the orbit, the bony socket in the skull, and it rotates by means of the six extraocular muscles: lateral rectus, medial rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique.

right_eye_lateral_view

The first five muscles, except for the inferior oblique, begin in the back of the orbit near the top. These muscles then pass anteriorly, towards the eyeball, forming a divergent cone. The rectus muscles are directly fasten to the sclera. The superior oblique muscle passes along the superior-medial corner of the bony socket to the cartilaginous block, slips through the loop of the block and changes its course to cross the eye axis, then passes under the superior rectus muscle and fastens to the sclera at the superior-lateral quadrant of the eyeball.

The inferior oblique muscle begins from the inferior-medial corner of the orbit, passes across the eye axis under the inferior rectus muscle, and fastens to the sclera behind the tendon of the lateral rectus muscle.

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April 26th
2009

Eye Anatomy  ⁄  Eyeball Anatomy

The normal eye is a sphere with about a 24-millimeter diameter and has three layers. The outer layer is the fibrous tunic of eyeball, the middle is the vascular tunic of eyeball, and the inner is the nervous tunic of eyeball, called the retina.

eye_anatomy

The parts of the fibrous tunic are the sclera and the cornea. The sclera is smooth and durable. The back part of the sclera is the thinnest, especially around the optic nerve. The front part of the outer layer, called the cornea, is transparent.

The parts of the vascular tunic are the iris, the ciliary body, and the choroid.

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