THE HUMAN EYE

 THE HUMAN EYE - 

                         IS OF THE MOST IMPORTANT AND SENSITIVE SENSE ORGANS. IT MAKE US SEE THE WONDERFUL WORLD AND THE AROUND US. ALL THE SENSE ORGANS, THE HUMAN EYE IS THE MOST IMPORTANT ONE AS IT MAKES THE AS ABLE TO SEE THE BEAUTIFUL , COLOURFUL WORLD AROUND US. 

  HUMAN EYE IS A LIKE CAMERA. ITS LENS SYSTEM PRODUCED AN IMAGE ON A LIGHT SENSITIVE  SCREEN KNOWN AS THE RETINA. LIGHT ENTERS EYE THROUGH A THIN MEMBRANE KNOWN AS THE CORNEA. IT PRODUCES THE TRANSPARENT BULGE ON THE FRONT SURFACE OF THE EYEBALL. THE EYEBALL IS MAINLY SPHERICAL IN SHAPE WITH A DIAMETER OF ABOUT 2.3 CM MOST OF THE REFRACTION RAYS ENTERING THE EYE TAKES PLACE FOR THE OUTER SURFACE OF THE CORNEA. THE CRYSTALLINE LENS MERELY GIVES THE FINER ADJUSTMENT OF FOCAL LENGTH NEEDED TO FOCUS OBJECTS AT DIFFERENT DISTANCES ON THE RETINA. IRIS IS A DARK MUSCULAR DIAPHRAGM. THE PUPIL CONTROL THE AMOUNT OF LIGHT ENTERING INTO THE EYE. THE EYE LENS PRODUCES THEM  AN INVERTED REAL IMAGE OF THE OBJECT ON THE RETINA. THE RETINA IS DELICATE MEMBRANE CONSISTING ENORMOUS NUMBER OF LIGHT SENSITIVE CELLS. THE LIGHT SENSITIVE CELLS GET ACTIVATED UPON AND PRODUCES ELECTRICAL SIGNALS. THESE SIGNALS ARE TRANSMITTED TO THE BRAIN VIA THE OPTIC NERVES THE BRAINS INTERPRETS THESE SIGNAL AND PROCESSES THE INFORMATION AS THAT PERCEIVE OBJECTS AS THEY ARE.                                                                                                                                                                   POWER OF ACCOMMODATION -                                                                                                                                         THE EYE LENS IS FORMED OF A FIBROUS, JELLY LIKE MATERIAL, LIKE MATERIAL. ITS CURVATURE CAN BE CHANGED TO SOME EXTENT BY THE CILIARY MUSCLE . THE MODIFICATION IN THE CURVATURE OF THE EYE LENS CAN THUS CHANGE ITS FOCAL LENGTH . WHEN THE MUSCLES GET RELAXED, THE LENS BECOME THIN . ITS FOCAL LENGTH INCREASES . THIS MAKES US A UNABLE TO SEE DISTANT CLEARLY. INCREASES THE CURVATURE OF THE EYE LENS. THE EYE THAN BECOMES THICKER . CONSEQUENTLY, THE FOCAL LENGTH OF THE EYE LENS. THEN THE FOCAL LENGTH OF LENS DECREASE . THIS MAKES ABLE TO SEE NEARBY OBJECTS CLEARLY . 

   THE ABILITY OF THE EYE LENS TO ADJUST ITS FOCAL LENGTH IS KNOWN AS ACCOMMODATION. THE FOCAL LENGTH  OF THE EYE LENS CAN NOT BE DECREASE BELOW DEFINITE MINIMUM . THE  IMAGE GET BLURRED OR FEEL STRAIN IN THE EYE. TO SEE AN OBJECT DISTINCTLY AND COMFORTABLY , YOU MUST HOLD IT AT ABOUT  25 CM FROM THE EYE . THE MINIMUM DISTANCE WHICH OBJECT CAN BE SEE MOST DISTINCTLY AND COMFORTABLY WITHOUT STRAIN , LAST DISTANCE OF DISTINCT VISION . IT IS ALSO KNOWN AS THE NEAR POINT OF THE EYE IT IS AT INFINITY  FOR A NORMAL EYE .

THE CRYSTALLINE LENS OF OLD AGE PEOPLE THAT IT BECOMES MILKY. THIS CONDITION IS KNOWN AS CATARACT. THIS CAUSE COMPLETE OR PARTIAL LOSS OF VISION. IT IS POSSIBLE TO RESTORE VISION THROUGH A CATARACT SURGERY.