COLOUR BLINDNESS--- AN EYE DISEASES---

COLOUR BLINDNESS!!!
COLOR BLINDNESS IS AN INHERITED DEFECT OF VISION, RESULTING IN A PERSON'S INABILITY TO
DISTINGUISH BETWEEN SPECIFIC COLORS.
PARTIAL COLOR BLINDNESS IS MORE COMMON THAN TOTAL COLOR BLINDNESS, IN WHICH A PERSON SEES EVERYTHING AS SHADES OF GRAY
(GREY). THE MOST COMMON FORM OF PARTIAL
COLOR BLINDNESS LEADS TO INABILITY TO
DISTINGUISH BETWEEN RED AND GREEN AND RARELY BETWEEN BLUE AND YELLOW.COLOR BLINDNESS IS A FAIRLY COMMON CONDITION
WHICH OCCURS MORE IN MEN THAN WOMEN, BUT IT IS
RARELY A SERIOUS DISADVANTAGE TO THOSE AFFECTED.
APPROXIMATELY ONE IN 20 MEN AND ONE IN 200 WOMEN ARE AFFECTED .SOME STUDIES SUGGEST THAT ABOUT EIGHT PERCENT OF THE WORLD'S MALE POPULATION AND LESS THAN ONE PERCENT OF FEMALE
POPULATION ARE AFFECTED .MANY PEOPLE ARE UNAWARE THEY ARE COLOR BLIND UNTIL THEIR EYES HAVE BEEN TESTED .

THE RETINA COMPROMISES TWO TYPES OF PHOTORECEPTORS , RODS AND CONES. ALTHOUGH THE RODS ARE MORE NUMEROUS, SOME 120 MILLION, AND ARE MORE SENSITIVE THAN THE CONES, THEY ARE NOT HOW-EVER, SENSITIVE TO COLOR. RODS ARE RESPONSIBLE FOR VISION AT LOW LIGHT LEVELS
(SCOTOPIC VISION) AND THEY DO NOT MEDITATE COLOR VISION AND HAVE A LOW SPATIAL ACUITY THE SIX OR SEVEN MILLION CONES THAT PROVIDE THE EYE'S COLOR SENSITIVITY ARE MUCH MORE CONCENTRATED IN THE CENTRAL YELLOW SPOT KNOWN AS THE MACULA.

BEING ACTIVE AT HIGHER LIGHT LEVELS (PHOTOPIC VISION) CONES ARE CAPABLE OF COLOR VISION AND ARE RESPONSIBLE FOR HIGH SPATIAL ACUITY. IN SIMPLE TERMS IT MAY BE SAID THAT CONES REQUIRE BRIGHTER LIGHT TO FUNCTION THAN RODS.

RED ,GREEN AND HAVE THEIR CORRESPONDING WAVELENGTHS . RED WAVELENGTHS ARE LONGEST, FOLLOWED BY GREEN WAVELENGTHS (MEDIUM) AND BLUE COLOR IS MADE UP OF SHORTER WAVELENGTHS .

THEY ARE RED , BLUE AND GREEN CONES WHICH ARE SENSITIVE TO THOSE COLORS AND COMBINATIONS OF THEM. IF THE CONES DO NOT WORK PROPERLY OR IF THERE IS NO RIGHT COMBINATION, THE BRAIN DOES NOT GET THE RIGHT MESSAGE ABOUT THE COLORS YOU ARE SEEING.

THE VISIBLE COLORS FROM SHORTEST TO LONGEST WAVELENGTH ARE VIOLET, BLUE , GREEN , YELLOW , ORANGE AND RED.
THE VISIBLE RED LIGHT HAVING A WAVELENGTH OF ABOUT 650 NANOMETERS IS RESPONSIBLE FOR THE PRESENCE OF RED OR ORANGE COLOR AT SUNRISE AND SUNSET, BECAUSE THE WAVELENGTHS ASSOCIATED WITH THESE COLORS ARE LESS EFFICIENTLY SCATTERED BY THE ATMOSPHERE THAN THE SHORTER WAVELENGTH COLORS SUCH AS BLUE OR PURPLE.

THE VISIBLE GREEN LIGHT HAVING A WAVELENGTH OF ABOUT 510 NM MAKES THE GRASS APPEAR GREEN BECAUSE ALL THE COLORS IN THE VISIBLE PART OF SPECTRUM ARE ABSORBED INTO THE LEAVES OF THE GRASS APPEARS GREEN

THE VISIBLE BLUE LIGHT HAVING A WAVELENGTH OF ABOUT 475 NM ARE SCATTERED MORE EFFICIENTLY BY THE MOLECULES IN THE ATMOSPHERE WHICH CAUSE THE SKY TO APPEAR BLUE.

PEOPLE WHO ARE BORN BLIND DO NOT SEE IMAGES IN DREAMS, BUT HAVE DREAMS VIVID INVOLVING THEIR OTHER SENSES OF SOUND, SMELL, TOUCH AND EMOTION.

COLOR BLINDNESS CAUSED BY A DISEASE OF THE RETINA OR OPTIC NERVE IS PROGRESSIVE AND ASSOCIATED WITH A GENERAL DETERIORATION OF VISION, UNLIKE INHERITED VARIETY WHERE THE ABILITY TO SEE DETAIL IS UNAFFECTED AND THE CONDITION NEVER WORSEN.
S.S.VENKATESHWAR
BATHUBASTHI
ANDAMAN

PERAL FARMING____

PEARL FARMING----
Valuable pearls occur in the wild, but they are very rare. These are called Natural Pearls. They are formed inside the shell of certain mollusks: as a defense mechanism to a potentially threatening irritant such as a parasite inside its shell, injuring the mantle tissue. The mollusk creates a pearl sac to seal off the irritation. Pearls are grown artificially by implanting (nucleated) an irritant and then allow the mollusk to create a pearl sac, as a counter reaction by secreting nacre to surround the object or irritant. This develops into a Cultured Pearl. The whole process is called Pearl Farming.
These cultured pearls make up nearly 100% of the pearls sold today. In a Pearl Farm, several thousand oysters are nucleated and then cared for during this period. Around 2-5 years are required for a pearl to grow and develop. Pearl farms can be set up in rivers, lakes or oceans, depending on whether you want to grow Freshwater or Saltwater pearls. To grow properly, oysters and mollusks need clear, tranquil waters at a temperature of about 20-30º C (or about 68-86º F). Like any other form of farming, pearl farming can be as dependent on luck as it is on skill. An entire bed of oysters can be completely devastated by unpredictable

and uncontrollable factors, such as water pollution, severe storms, excessive heat or cold, disease and many other natural and man-made phenomena. Although pearl farmers attempt to control as many of these variables as possible, pearl farming can indeed be a risky business!

The First Step:- The first step in the pearl production process is to obtain oysters to be nucleated. In the early days of the cultured pearl industry, oysters were simply collected from the sea. Although some farmers continue using this method today, many use the more modern practice of breeding their own oysters. To do this, the pearl farmer collects oyster sperm and eggs from high-quality oysters already on the farm. The sperm are used to fertilize the eggs, and so create a new generation of oyster larvae. Over a period of a few months, the larvae develop into baby oysters. They are generally then moved into a separate "nursery" area of the farm. Here they are tended for around 1-2 years, until they have grown sufficiently large to be nucleated.
A pearl technician nucleating a pearl

Nucleating

The Process Of Nucleation In Pearl Farming:- The process of nucleation is a surgical procedure, whereby a foreign object is implanted into the oyster. This object causes irritation, which the oyster counteracts by secreting nacre to surround the object; this produces the pearl. Two basic methods of nucleation are used. Saltwater oysters are generally nucleated using a "bead", prepared from mother-of-pearl. First, the bead is surrounded by a small piece of mantle tissue taken from a donor oyster. The bead and tissue are then implanted into the oyster's gonad. The bead serves as a mold, or nucleus, around which the pearl develops. The resulting pearl will contain the bead at its center and will tend to develop in the same general shape as the original bead. The bead can be detected in the final pearl by x-rays.
Pearl inside and Oyester A newly opened freshwater mussel, showing the rows of cultured pearls inside

Freshwater mussels are generally grafted using a piece of mantle tissue only, without a bead. This small piece of mantle tissue is placed into an incision in the host mussel's mantle instead of the gonad. An average freshwater mussel will produce 24 to 32 pearls per culturing cycle.

Finally, The Pearls Are Harvested:-s.s.venkateshwar,Bathubasthi, Andaman