The Retina – How It Works - Arohi Eye Hospital

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Retina is mainly responsible for converting the
incoming light into nerve signals, which is how
the eyes can see objects clearly under different
lighting conditions, day or night. The retina
also helps in recognizing colours by
differentiating between the different
wavelengths of light. And, do you know how you
can see even the minutest things such as a
strand of hair, or a speck of dust even a few
meters away? Yes, it is thanks to the retina. You
can thus imagine what one can go through if the
retina is damaged!

• How does the retina work?
• The retina is a plate shaped structure that is a
  quarter millimeters in thickness, and consists
  of three layers of nerve-cell bodies, which are
  separated by layers that contain the synapses
  made by the axons and dendrites of these cells.
  The retina consists of sensory neurons and
  intricate neural circuits, which respond to
  light and perform the primary functions of image

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• processing respectively. Then, an electrical
  message travels through the optic nerve to the
  brain, which further processes the visual
  perception.
• The retina has a number of photoreceptors at the
  back, which contain pigment molecules that are
  excited when light touches them. These
  photoreceptors are in touch with the epithelial
  layer of the eye, which provide a steady stream
  of retinal molecules. These molecules, when
  exposed to light, undergo a conformational
  change, and are recycled back into the pigment
  epithelium, which contain melanin granules that
  absorb stray photons, preventing them from
  creating a reflection on the photoreceptors,
  which makes the images appear blurred.
• There are two types of photoreceptors the rods
  used for low light vision, and the cones for
  daylight and bright coloured vision. Can you
  imagine that such a small human retina consists
  of 4-5 million cones, and 77-107 million rods?
  And, the brightest vision can be experienced
  when the light directly falls on the Macula
  region of the retina, which consists of a large
  number of small and tightly packed cones.
• Each photoreceptor cell consists of an outer
  photopigment segment, inner mitochondria
  segment, a nucleus, an inner fiber, and a
  synaptic terminal. The photoreceptor cell is
  connected to the ganglion cell layer through
  bipolar cells and the rods and cones provide
  input to these bipolar cells. These ganglion
  cells transmit the visual information from the
  retina to the brain.
• The most common retinal diseases
• There are various kinds of diseases and disorders
  that can harm the retina, which affect the
  vision, making it blurred or distorted. The most
  common retinal diseases include

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• Retinal tear or detachment This damage is
  caused when the vitreous moves away from the
  retina so much that it tears the retina. Fluid
  tends to pass through this retinal tear, thus
  lifting it off the back of the eye. With such a
  retinal detachment, the vision becomes blurred,
  and may also result in blindness.
• Macular hole This condition is caused due to
  the shrinkage or separation of the vitreous,
  causing sudden decrease in vision. The various
  reasons that can cause macular hole include
  diabetic eye disease, retinal detachment, eye
  injury, macular pucker, high amount of
  nearsightedness, or an inherited condition.
• Macular degeneration Macular degeneration
  occurs when parts of the macula get thinner with
  age, causing tiny clumps of proteins to grow on
  them. This disorder results in losing the
  central vision, which does not let the patient
  identify the fine details of an object. But, the
  peripheral/side vision remains normal. Macular
  degeneration may also occur when there is
  abnormal growth of blood vessels under the
  retina, causing blood or other fluid to leak
  from these vessels, thus causing macula
  scarring. This is a rare but serious type of
  macular degeneration, which brings vision loss
  much faster.
• Diabetic retinopathy This disorder affects
  those suffering from diabetes, as the high blood
  sugar levels often damage the blood vessels
  within the retina, causing them to swell and
  leak. And, if they completely close, blood flow
  is completely stopped!
• Retinal vein occlusion This disorder is caused
  when the veins that carry blood away from the
  retina get blocked due to hardened arteries
  which cause blood clots. The various factors
  that can cause retinal vein occlusion include
  diabetes, high blood pressure, atherosclerosis,
  and other eye conditions like macular edema,
  glaucoma, and vitreous hemorrhage.

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To stay away from all such disorders and damages,
it is important that you have regular visits to
an eye specialist. Arohi Eye Hospital is the
best retina specialist in Mumbai where you can
have your eyes examined by expert doctors to
determine early symptoms of any of the above or
other retinal diseases, so that the right
actions can be taken before the condition gets
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