The Western lensAnatomy, physiology, biomechanics
The eye, its blood supply and the visual brain
Sight runs from the retina, along the optic nerve, to the visual cortex at the back of the brain. All of it is living nerve tissue with a high demand for blood and oxygen, so in many degenerative eye conditions the question is supply as much as the tissue itself.
- The retina and macula
- The retina has one of the highest metabolic demands of any tissue in the body, and the macula at its center handles fine detail and color. When delivery of blood and oxygen falls behind that demand, the tissue is thought to become more vulnerable.
- Glaucoma beyond pressure
- Glaucoma damages the optic nerve. Eye pressure matters, but in normal-tension glaucoma the nerve is lost while pressure stays in the normal range, which turns attention to the blood supply at the head of the optic nerve. Pressure-lowering drops are never to be stopped on our account.
- Same symptom, different cause
- Optic neuritis is inflammation of the optic nerve, often with loss of its myelin coating and sometimes linked with MS. NAION is a failure of blood flow to the front of the optic nerve, sometimes called a stroke of the optic disc. Both can dim or blur sight, and they are planned differently. Sudden vision loss needs urgent medical care first.
- The visual cortex
- The signal from the eye is finally read at the back of the brain. Scalp acupuncture places needles in zones over that area, alongside the work aimed at the eye itself, an approach thought to support how the brain processes what the eye sends.
- When the nerves move the eyes
- Cranial nerves three, four and six move the eyes. A palsy of one of them can cause double vision, and visual field loss can follow a stroke, so some vision problems are read at the nerve and the brain rather than the eye itself.