INSIGHT EYE CARE

1. 2. 3. 4. 5. 6. 7. https://youtu.be/UqPSX6YDduE

Identification of a lens - Convex lens - 1.  It is thick in the center and thin at margins.  2.  Convex lens is a magnifying lens, objects appear bigger in size.  3.  If we move a lens the image moves in opposite direction.  4.  It is denoted by PLUS(+)  sign 5.  It is used to correct hypermetropia and presbyopia.  Concave lens - 1.  It is thin in the center and thick at margins.  2.  It is a minifying lens, objects appear smaller in size.  3.  If we move a lens the image moves in same direction.  4.  It is denoted by MINUS(-)  sign.  5.  It is used to correct myopia.   ------------------------------------------------------------------------------- Both convex and concave lenses are of two types : 1. Spherical lens - i. Movement of images can be seen in all direction.  ii. If we rotate a lens, there is no distortion of image...

Optical Axis A line passing through centre of cornea,  centre of lens and posterior pole of retina is the optical axis of eyeball. (ONA)  Visual Axis A line joining point of taxation with phobia and passing through nodal point of eyeball is called visual axis. Nodal point of eyeball is just anterior to posterior capsule of lens.  Fixation point is the point which is being seen with phobia at any particular moment. (VNF)  Pupillary Axis This is a straight line that passes through centre of pupil. (OPA)  Fixation Axis This is a straight line that joins centre of rotation of eyeball with fixation point. (VC)  ------------------------------------------------------------------------------- ANGLES - 1. Angle Alpha -  Is the angle formed between optical axis and visual axis that is angle (ONV)   2. Angle Kappa -   Is the angle formed between visual axis and pupillary axis. (OPV)  ...

Reflection of light - When a ray of light strikes a polished surface, it bounces back in a particular direction. This is known as reflection of light.  Laws of Reflection - The laws of reflection can be summarized as : 1. The incident ray,  the reflected ray and the normal at the point of incidence, all lies in the same plane.  2. The angle of incidence is equal to the angle of reflection.   Refraction of light  - When a ray of light passes from one medium (say air)  to another medium (say glass)  of different optical density, it deviates from its original path. This is called refraction.  Laws of Refraction - 1. The incident ray and the refracted ray are on the opposite sides of the normal at the point of incidence and all three lie in the same plane.  2. The ratio of sine of angle of incidence to the Sine of angle of refraction is constant.  This is known as snell's law.  Sine ang...

                    Human Eyeball Structure Eyeball parts name- Cornea Conjunctiva Iris Pupil Crystalline lens (natural lens)  Zonules (suspensory ligament)  Ciliary body Limbus Canal of Schlemm Ora serrata Sclera Choroid Retina Macula lutia (fovea)  Optic disc Optic nerve  Dimensions of adult Eyeball- Anteroposterior diameter.               24mm Horizontal diameter.                         23.5mm Vertical diameter.                               23mm Circumference.                                    75mm Volume.                              ...