what do you want to know about eyes? which eyes do you want discuss?

http://users.rcn.com/jkimball.ma.ultran … ision.html

Hi everyone

I just wanted to ask a question regarding how the rods and cone cells pick up light. Is it right that the light has to pass the ganglion and bipolar cells then it reaches the cones and rod cells? then then impulse is triggered and sent through to the bipolar and ganglion cells and from there it leaves through the optic nerves?
The reason why I ask this is because i had question on it and i didn’t understand, the question gave a picture of the rods and cone cells and asked me to draw an arrow to show which way the light was travelling in and i did it from the cone cell going down to the optic nerves and it was marked wrong
I would appreciate if someone could explain

Yes that is correct. You did mark it wrong at the paper. If light were to travel directly to the cone and rods, wit would be too powerful and you would see nothing but a bright light(immagine sitting next to the sun). So evolution invented this system, that light has to cross all the other layers of the retina..

I have heard that there is a link between diabetes and blindness. Can anyone explain this?

What makes the eye the color it is?

Too much glucose in the blood damages the body.

Are you reffering to melanine?

It is iris that gives eye its color

The colored part of the eye is called the iris. It controls light levels inside the eye similar to the aperture on a camera. The round opening in the center of the iris is called the pupil. The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size.

The sphincter muscle lies around the very edge of the pupil. In bright light, the sphincter contracts, causing the pupil to constrict. The dilator muscle runs radially through the iris, like spokes on a wheel. This muscle dilates the eye in dim lighting.

The iris is flat and divides the front of the eye (anterior chamber) from the back of the eye (posterior chamber). Its color comes from microscopic pigment cells called melanin. The color, texture, and patterns of each person’s iris are as unique as a fingerprint.

As Poison had said too much glucose leads to damage in the retina, the technical name is diabetic retinopathy which refers to the process. Too much glucose cause thickening in the vessels and the arterioles. This cause microaneurysms in the capillary walls arond the eyes. The walls of the microaneurysm are weak, so eventually fluids may leak out, causing hemorrhages. Sometimes the capillaries may be blocked in the vessels, so new ones are formed to compensate. Again, these vessels are weak and may tear. If a macula is involved, then it can cause blindness.

Hope that helps.