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Анатомия на окото За да попадне светлината в окото, първо трябва да премине през роговицата - най-предната прозрачна част на зрителния орган. Тя осигурява шестдесет процента от диоптричната (пречупвателната) сила на окото. След пречупването на светлинните лъчи от роговицата те преминават през зеницата. Тя представлява отвор на ириса, променящ се според интензивността на светлината. Ирисът от своя страна придава цвета на окото. След зеницата светлината преминава през лещата, която има способността да променя пречупвателната си сила в зависимост от отдалечеността на наблюдавания предмет, като по този начин спомага, получаваният образ винаги да бъде на фокус. При нормалните очи след лещата светлината преминава през стъкловидното тяло - гелообразна структура, която изпълва окото отвътре и му придава сферична форма. Най-накрая образът от наблюдавания предмет попада върху ретината във фокусиран вид. Централната част на ретината, отговаряща за ясното виждане, се нарича макула. Ретината е изградена от милиони светлочувствителни клетки, най-вътрешната част от които, с дългите си нервни окончания, образуват снопа на зрителния нерв. Зрителният нерв предава зрителните дразнения към мозъка, където те се възприемат като образ.
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Human Eye: The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. Eyesight is not something to take for granted. It depends on many different parts working together to form ourvision. The basic parts of the eye are as follows: eyelids - help protect the eye conjunctiva - this is what lines the eyelid cornea - the clear covering on the front of the eye sclera - the white of the eye iris - the colored part of the eye that helps control the amount of light that enters pupil - the hole in the center of the iris that is dark lens - focuses the light onto the back of the eye retina - the layer of nerves in the back of the eye, made up of rods and cones macula - a section of the retina near the center that lets us see fine details optic nerve - sends an electrical signal to the brain How does all this work together? Light hits an object and bounces off. That reflected light enters the eye through the cornea. The cornea acts like a window and works with the lens to focus the light. The iris opens and closes, which adjusts the size of the pupil, to control how much light gets in. The light then hits the retina in the back of the eye, with its millions of light-sensing cells, the rods and cones. At this point, the light is changed into an electrical signal and sent through the optic nerve to the brain, which converts that signal into an image it can understand. It works very much like a camera and film. The eye's cornea and lens are like the lens of a camera, which focus on an object. The retina is like the film where the image is laid down and the brain develops the picture. People who have never had vision problems sometimes take their eyesight for granted. But it's important to do all we can to protect our vision. Eyesight depends of a complex series of interactions between the different parts of the eye. One way to protect our eyesight is by getting the periodic screenings and vision tests that we need. Just as your physical health requires routine exams from your family physician, so too does your eye health require an annual or bi annual exam to ensure your vision remains intact. Studies including a study published by the Global Campaign Report on Early Detection discovered that much of the population remains largely unaware of how important routine eye exams are to their health and well being. In many countries people at increased risk for vision loss are unaware of the risks of certain eye diseases, therefore fail to take advantage of early detection measures available from eye care professionals. Healthy sight is something to be cherished, maintained and protected.