الفهرس 
What is nanotechnology?Only 14 pages are availabe for public view
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Abstract
A nanometer is a unit of measure which is equivalent to
one billionth of a meter. A billion (10-9) is a thousand times
bigger than a million. Materials in the nanometer scale may
exhibit physical properties distinctively different from that of
bulk. They exhibit some remarkable specific properties.
Nanomaterials may be of one, two or three dimensions in
structure.
Nanotechnology is a new discipline of science and
engineering that has led to innovative approaches in many areas
of medicine. Its applications in the screening, diagnosis, and
treatment of disease are collectively referred to as nanomedicine.
The aim of nanomedicine is the comprehensive monitoring and
control of human biological systems at the molecular level, using
engineered nanodevices and nanostructures to achieve medical
benefit as diagnostic tools, drug delivery, surgery, regenerative
medicine, bacterial elimination and many others which are being
intensively researched.
Nanotechnology has many innovative applications in
ophthalmology
Corneal NV accompanies the most common causes of
corneal infectious blindness diseases. Nanoparticles could be used
as a vehicle to deliver VEGF intraceptors intrastromally. These
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intraceptors can suppress VEGF secretion in human corneal
epithelial cells.
Also nanomaterials include biodendrimers which are
promising new alternative tissues which can be applied to fullthickness
corneal lacerations,unstable (LASIK) flaps and closure
of leaky cataract surgical incisions to create a watertight seal .
Recent advances in the development of femtosecond laser
sources have been useful in many ophthalmic surgeries like
LASIK and cataract. Nanocomposites have been used as a
material for intraocular lens synthesis.
Nanoparticles proved to be an efficient vehicle for drug
delivery in attempt to pass ocular barriers to reach different eye
structures and increase the residence time of topically applied
molecules aiming for eye structures in the anterior segment of the
eye. Also drug delivery to the posterior segment has a special
importance for its great benefit at minimizing the frequency of
intraocular injections and following potential undesired side
effects needed to treat retinal disorders especially those associated
with neovascularization. Nanoparticles open a new strategy to
improve non-viral gene transfer which proved to help treatment of
many retinal degenerative diseases.
Nanotechnology is emerging to help solving challenges
faced in detection and treatment of ocular tumors. Nanomaterials
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are useful for chemotherapy targeted drug delivery, thermal
ablation of cancer cells and improve imaging quality of imaging
modalities for early detection of cancer. Regenerative medicine
will have promising solutions through nanotechnology which
allows controlling of features down to the submicron level .Thus
improving cell survival and differentiation and improving chances
for retinal regenerative diseases such as Retinitis pigmentosa.
Interestingly, pharmaceutical sciences are using
nanoparticles to reduce toxicity and side effects of drugs however
carrier systems themselves may impose risks to the patient. For
nanoparticles size opens the potential for crossing the various
biological barriers within the body. Nanoparticles can enter the
body through inhalation, skin and ingestion. Possible mechanisms
of toxicity include production of reactive oxygen species, effect
of physical parameters and surface chemistry. Moreover,
variations in size and shape can have dramatic and unpredictable
effects which make separate researches on each nanoparticle type
essential. Many studies proved no toxic effect of most
nanoparticles vehicles on eye structures. However they are
injurious to other body organs like the liver and the kidney. The
issue of nanomaterial toxicity remains controversial and requires
more study