The document summarizes the physiology of aqueous humour in the eye. It is produced by the ciliary body at a rate of around 2.5 μL/min and has a similar composition to plasma but with lower protein levels. It is replenished around every 100 minutes. Aqueous humour maintains intraocular pressure and provides nutrients to ocular tissues before draining through the trabecular meshwork. Increased pressure can lead to glaucoma, which involves damage to the optic nerve and visual field loss. Diagnosis involves measuring pressure, examining the optic nerve and drainage angle, and testing vision.

1. Ophthalmology
(Aqueous Humour)
By
Dr. Laraib Jameel Rph
Follow me on slideshare.net
https://www.slideshare.net/

2. Physiology of aqueous humour
• Aqueous humor is an optically clear, slightly alkaline ocular fluid
that is continuously formed (~ 2.5 μL/min in humans) from plasma
by epithelial cells of ciliary body.
• similar to plasma, but containing low protein concentrations.
• Three different processes diffusion, ultrafiltration and active
secretion contribute to the chemical composition and formation
of aqueous humor.
• It is estimated that the entire aqueous humor is replaced in
approximately 100 min
• ciliary body : The ciliary body is the tissue which covers the inner
part of the anterior segment of the eye coating. It is composed of
the ciliary muscle.
• On the surface of the ciliary body is the black ciliary epithelium,
which produces the aqueous humour,

3. Ciliary body

5. • aqueous humour fills both the anterior and
the posterior chambers of the eye.
• Aqueous humor produced and secreted into the posterior eye
segment passes through the pupil into the anterior chamber.
It is drained into the venous blood circulation
via the trabecular
meshwork and
the canal of Schlemm

7. • Composition
• Amino acids: transported by ciliary muscles
• 98% water
• Electrolytes
• Sodium = 142.09, Potassium = 2.2 - 4.0 ,Calcium = 1.8,
Magnesium = 1.1, Chloride = 131.6, HCO3- = 20.15,
Phosphate = 0.62
• Ascorbic acid
• Glutathione (Anti-Oxidant)
• Immunoglobulins= Ig G
• pH = 7.4

8. • FUNCTION:
• Maintains the intraocular pressure and inflates the globe of the eye.
• It is this hydrostatic pressure which keeps the eyeball in a roughly
spherical shape and keeps the walls of the eyeball tight.
• Provides nutrition (e.g. amino acids and glucose) for the avascular ocular
tissues; posterior cornea, trabecular meshwork, lens, and anterior
vitreous.
• May serve to transport ascorbate in the anterior segment to act as an
antioxidant agent.
• Presence of immunoglobulins indicate a role in immune response to
defend against pathogens.
• Provides inflation for expansion of the cornea and thus increased
protection against dust, wind, pollen grains and some pathogens.
• for refractive index.

9. • Drainage
• The drainage route for aqueous humour flow is first through
the posterior chamber, then the narrow space between the
posterior iris and the anterior lens (contributes to small resistance),
through the pupil to enter the anterior chamber. From there, the
aqueous humour exits the eye through the trabecular
meshwork into Schlemm's canal (a channel at the limbus, i.e., the
joining point of the cornea and sclera, which encircles the cornea[)
• It flows through 25–30 collector canals into the episcleral veins. The
greatest resistance to aqueous flow is provided by the trabecular
meshwork (esp. the juxtacanalicular part), and this is where most of
the aqueous outflow occurs. The internal wall of the canal is very
delicate and allows the fluid to filter due to high pressure of the
fluid within the eye.

10. Drainage

11. Aqueous humour
• Drainage:
• The secondary route is the uveoscleral drainage, and
is independent of the intraocular pressure, the
aqueous flows through here, but to a lesser extent
than through the trabecular meshwork (approx. 10%
of the total drainage whereas by trabecular
meshwork 90% of the total drainage).
• The fluid is normally 15 mmHg (0.6 inHg) above
atmospheric pressure, so when a syringe is injected the
fluid flows easily. If the fluid is leaking, due to collapse
and wilting of cornea, the hardness of the normal eye
is therefore corroborate

12. Maintenance of normal intraocular
pressure
• Definition: Intraocular pressure is determined by the production
and drainage of aqueous humour by the ciliary body and its
drainage via the trabecular meshwork and uveoscleral outflow.
• The eye is a closed ball filled with clear jelly (vitreous humor) in the
back behind the lens and clear fluid (aqueous humor) in the front,
between the iris and the cornea. Aqueous humor is created just
behind the iris and is in continuous circulation throughout the front
part of the eye before it drains out just in front of the iris where it
meets the cornea. This fluid helps keep the eye "inflated" just like
air inside a balloon.
• Pressure in the human eye, known as intraocular pressure, varies
throughout the day with "normal" pressure being anywhere
between 10 and 21 mmHg.

13. Intraocular pressure
• Measurements:
• We can measure pressure of the eye just like you can gauge
how full a balloon is by poking the balloon with your
finger. The less air or pressure in the balloon, the easier it
will be to poke and conversely, the more air or pressure in
the balloon, the stiffer the balloon will be and the harder it
will be to poke it.
• We measure pressure in the eye the same way; by gently
touching the cornea with special instruments to see how
hard it is to "poke." The unit of measurement is
millimeters of mercury, or mmHg.
• Intraocular pressure is measured with a tonometer as part
of a comprehensive eye examination.

14. Tonometer

15. IOP Can be determined by using this formula
Po=(F−U)/C+Pv
Where:
• Po is the IOP in millimeters of mercury (mmHg)
• F the rate of aqueous humour formation in microliters per
minute (μL/min)
• U the resorption of aqueous humour through the
uveoscleral route (in μL/min)
• C is the facility of outflow in microliters per minute per
millimeter of mercury (μL/min/mmHg)
• Pv the episcleral venous pressure in millimeters of mercury
(mmHg).

16. Classification
• Current consensus among ophthalmologists and
optometrists define normal intraocular pressure as
that between 10 mmHg and 20 mmHg. The average
value of intraocular pressure is 15.5 mmHg with
fluctuations of about 2.75 mmHg.
• Ocular hypertension (OHT) is defined by intraocular
pressure being higher than normal, in the absence
of optic nerve damage or visual field loss.
• Ocular hypotension, Hypotony, or ocular hypotony, is
typically defined as intraocular pressure equal to or
less than 5 mmHg. Such low intraocular pressure could
indicate fluid leakage and deflation of the eyeball.

17. Factors influencing
intraocular pressure
The normal level of IOP is essentially maintained by a dynamic
equilibrium between the formation and outflow of the aqueous
humour.
LOCAL FACTORS:
• 1. Rate of aqueous formation influences IOP levels such as
permeability of ciliary capillaries and osmotic pressure of the blood.
• 2. Increased episcleral venous pressure may result
in rise of IOP.
• 3. Resistance to aqueous outflow (drainage).
• 4. Dilatation of pupil in patients with narrow
anterior chamber angle may cause rise of IOP
owing to a relative obstruction of the aqeuous
drainage by the iris.

19. Factors influencing
intraocular pressure
GENERAL FACTORS:
• Heredity. It influences IOP, possibly by multifactorial modes.
• Age. The mean IOP increases after the age of 40 years, possibly due to reduced
facility of aqueous outflow.
• Postural variations. IOP increases when changing from the sitting to the supine
position.
• Blood pressure. As such it does not have longterm effect on IOP. However,
prevalence of glaucoma is marginally more in hypertensives than the
normotensives.
• Osmotic pressure of blood. An increase in plasma osmolarity (as occurs after
intravenous mannitol, oral glycerol or in patients with uraemia) is associated
with a fall in IOP, while a reduction in plasma osmolarity (as occurs with water
drinking provocative tests) is associated with a rise in IOP.
• General anaesthetics and many other drugs also influence IOP e.g., alcohol lowers
IOP, tobacco smoking, caffeine and steroids may cause rise in IOP.

20. Glaucoma
• Glaucoma is a progressive optic neuropathy where retinal
ganglion cells and their axons die causing a corresponding
visual field defect.
• An important risk factor is increased intraocular
pressure (pressure within the eye) either through increased
production or decreased outflow of aqueous humour.
• Increased resistance to outflow of aqueous humour may
occur due to an abnormal trabecular mesh work or to
obliteration of the meshwork due to injury or disease of the
iris.
• although it is a major risk factor. Uncontrolled glaucoma
typically leads to visual field loss and ultimately blindness.

21. Glaucoma
• Definition: Glaucoma is a group of eye
conditions that damage the optic nerve, the
health of which is vital for good vision. This
damage is often caused by an abnormally
high pressure in your eye. (IOP)
• Glaucoma is one of the leading causes of
blindness for people over the age of 60.

22. ‫سبز‬‫موتیا‬ Glaucoma
• Causes:
• Glaucoma is the result of damage to the optic nerve. As this nerve
gradually deteriorates, blind spots develop in your visual field.
• This nerve damage is usually related to increased pressure in the
eye.
• 1- Elevated eye pressure is due to a buildup of a fluid (aqueous
humor) that flows throughout the inside of your eye. This internal
fluid normally drains out through a tissue called the trabecular
meshwork at the angle where the iris and cornea meet. When fluid
is overproduced or the drainage system doesn't work properly, the
fluid can't flow out at its normal rate and eye pressure increases.
• 2- Genetics: Glaucoma tends to run in families. In some people,
scientists have identified genes related to high eye pressure and
optic nerve damage.

23. • Pathophysiology:
• The space between the clear front surface of the eye (the cornea) and the lens
inside the eye is filled with a clear fluid called the aqueous humor. This fluid
nourishes the inside of the anterior part of the eye. It also maintains the shape of
the eye by keeping the eyeball properly pressurized.
• The aqueous humor is constantly being produced by a structure called the ciliary
• body that surrounds the lens, and it drains from the eye through a mesh-like
channel called the trabecular meshwork that's located in the angle formed inside
the eye where the cornea and iris meet.
• If something causes this "drainage angle" to close down or the trabecular
meshwork to become clogged, the aqueous humor cannot drain from the eye
fast enough, and pressure inside the eye (IOP) increases.
• Glaucoma usually occurs when too much pressure inside the eye causes damage
to the optic nerve at the back of the eyeball, leading to permanent vision loss.
• Recent studies also have implicated low intracranial pressure (the pressure that
surrounds the brain) as one of the risks for glaucoma

25. Types of glaucoma
Open-angle glaucoma
• Open-angle glaucoma is the most common form of the
disease. The drainage angle formed by the cornea and iris
remains open, but the trabecular meshwork is partially
blocked.
This causes pressure
in the eye to gradually
increase. This pressure
damages the optic nerve.
It happens so slowly that
you may lose vision before
you're even aware of a problem.

26. • Angle-closure glaucoma
• Angle-closure glaucoma, also called closed-angle glaucoma, occurs when the iris
bulges forward to narrow or block the drainage.
angle formed by the
cornea and iris. As a
result, fluid can't
circulate through the
eye and pressure
increases. Some
people have narrow
drainage angles,
putting them at
increased risk of
angle-closure
glaucoma.

27. • Normal-tension glaucoma
• In normal-tension glaucoma , optic nerve becomes damaged even though
eye pressure is within the normal range. No one knows the exact reason
for this. You may have a sensitive optic nerve, or you may have less blood
being supplied to your optic nerve. This limited blood flow could be
caused by atherosclerosis — the buildup of fatty deposits (plaque) in the
arteries or other conditions that impair circulation.
• Pigmentary glaucoma
• In pigmentary glaucoma, pigment granules from your iris build up in the
drainage channels, slowing or blocking fluid exiting your eye. Activities
such as jogging sometimes stir up the pigment granules, depositing them
on the trabecular meshwork and causing intermittent pressure elevations.
• Primary glaucoma - this means that the cause is unknown.
• Secondary glaucoma - the condition has a known cause, such as
a tumor, diabetes, an advanced cataract, or inflammation.

28. • Sign & Symptoms:
• The most common type of glaucoma has no early warning signs
and can only be detected during a comprehensive eye exam. If
undetected and untreated, glaucoma first causes peripheral vision
loss and eventually can lead to blindness.
• By the time you notice vision loss from glaucoma, it's too late. The
lost vision cannot be restored, and it's very likely you may
experience additional vision loss, even after glaucoma treatment
begins.
• the signs and symptoms of glaucoma vary depending on the type
and stage of your condition. For example:
• Open-angle glaucoma
• Patchy blind spots in your side (peripheral) or central vision,
frequently in both eyes
• Tunnel vision in the advanced stages

29. • Symptoms of Acute angle-closure glaucoma
• Severe headache
• Eye pain
• Nausea and vomiting- due to occulocardiac reflex
• Blurred vision
• Halos around lights
• Eye redness
• The oculocardiac reflex is one of several trigeminal
nerve reflexes. Noxious stimulation of trigeminal nerve
afferents activates the paratrigeminal nuclei in the
medulla with secondary stimulation of the vagus nerve.

30. Glaucoma
• Risk factors
• Having high internal eye pressure (intraocular pressure)
• Being over age 60
• Being black, Asian or Hispanic
• Having a family history of glaucoma
• Having certain medical conditions, such as diabetes, heart
disease, high blood pressure and sickle cell anemia
• Having corneas that are thin in the center
• Being extremely nearsighted or farsighted
• Having had an eye injury or certain types of eye surgery
• Taking corticosteroid medications, especially eyedrops, for
a long time

31. • Diagnosis:
• doctor will review medical history and conduct a
comprehensive eye examination.
• He or she may perform several tests, including:
• Measuring intraocular pressure (tonometry)
• Testing for optic nerve damage with a dilated eye
examination and imaging tests (CT-Scan)
• Checking for areas of vision loss (visual field test)
• can detect central and peripheral vision problems caused
by glaucoma, stroke and other eye or brain problems.
• Measuring corneal thickness (pachymetry)
• Inspecting the drainage angle (gonioscopy)

32. Pachymetry
• The instrument used for this purpose is known as a pachymeter.
• It can be done using either ultrasonic or optical methods
• This devices that display the thickness of the cornea, usually in
micrometres, when the ultrasonic transducer touches the cornea.
• Using this technology
the user can capture an
ultra-high definition
echogram of the cornea,
somewhat like a corneal A-scan.
• Pachymetry using the
corneal waveform process allows
the user to more accurately
measure the corneal thickness,
and measure structures within the cornea such as micro bubbles.

33. Gonioscopy
• Gonioscopy is an eye examination to look at the front part of your eye (anterior
chamber) between the cornea and the iris.
• Gonioscopy is a painless examination to see whether the area where fluid drains
out of your eye (called the drainage angle) is open or closed. It is often done
during a regular eye examination, depending on your age and whether you are at
high risk for glaucoma.
• Process
• cleaning and sterilising the front (curved) surface of the goniolens
• applying lubricating fluid to the front surface if appropriate
• anaesthetising the patient's cornea with topical anaesthetic
• preparing the slit lamp for viewing through the goniolens
• gently moving the patient's eyelids away from the cornea
• slowly applying the goniolens to the ocular surface, forming suction
• fine-tuning the slit lamp to optimise the view
• interpreting the gonioscopic image
• swivelling the goniolens to view each section of the iridocorneal angle
• when satisfied, very carefully breaking suction via the eyelids

35. • Treatment
• The damage caused by glaucoma can't be reversed. Glaucoma is treated
by lowering your eye pressure (intraocular pressure). Depending on your
situation, your options may include prescription eyedrops, oral
medications, laser treatment, surgery or a combination of any of these.
• Eyedrops
• Glaucoma treatment often starts with prescription eyedrops. These can
help decrease eye pressure by improving how fluid drains from your eye
or by decreasing the amount of fluid your eye makes.
• Prostaglandins. These increase the outflow of the fluid in your eye
(aqueous humor), thereby reducing your eye pressure. Medicines in this
category include latanoprost (Xalatan), travoprost (Travatan Z), tafluprost
(Zioptan), bimatoprost (Lumigan) and latanoprostene bunod (Vyzulta).
• Possible side effects include mild reddening and stinging of the eyes,
darkening of the iris, darkening of the pigment of the eyelashes or eyelid
skin, and blurred vision. This class of drug is prescribed for once-a-day use.

36. • Beta blockers. These reduce the production of fluid in your eye, thereby
lowering the pressure in your eye (intraocular pressure). Examples include
timolol (Betimol, Istalol, Timoptic) and betaxolol (Betoptic).
• Possible side effects include difficulty breathing, slowed heart rate, lower
blood pressure, impotence and fatigue. This class of drug can be
prescribed for once- or twice-daily use depending on your condition.
• Alpha-adrenergic agonists. These reduce the production of aqueous
humor and increase outflow of the fluid in your eye. Examples include
apraclonidine (Iopidine) and brimonidine (Alphagan P, Qoliana).
• Possible side effects include an irregular heart rate, high blood pressure,
fatigue, red, itchy or swollen eyes, and dry mouth. This class of drug is
usually prescribed for twice-daily use but sometimes can be prescribed for
use three times a day.

37. • Carbonic anhydrase inhibitors. These medicines reduce
the production of fluid in your eye. Examples include
dorzolamide (Trusopt) and brinzolamide (Azopt). Possible
side effects include a metallic taste, frequent urination, and
tingling in the fingers and toes. This class of drug is usually
prescribed for twice-daily use but sometimes can be
prescribed for use three times a day.
• Rho kinase inhibitor. This medicine lowers eye pressure by
suppressing the rho kinase enzymes responsible for fluid
increase. It is available as netarsudil (Rhopressa) and is
prescribed for once-a-day use. Possible side effects include
eye redness, eye discomfort and deposits forming on the
cornea.

38. • Miotic or cholinergic agents. These increase the outflow of fluid
from your eye. An example is pilocarpine (Isopto Carpine).
• Side effects include headache, eye ache, smaller pupils, possible
blurred or dim vision, and nearsightedness. This class of medicine is
usually prescribed to be used up to four times a day. Because of
potential side effects and the need for frequent daily use, these
medications are not prescribed very often anymore.
• Because some of the eyedrop medicine is absorbed into your
bloodstream, you may experience some side effects unrelated to
your eyes. To minimize this absorption, close your eyes for one to
two minutes after putting the drops in. You may also press lightly at
the corner of your eyes near your nose to close the tear duct for
one or two minutes. Wipe off any unused drops from your eyelid.

39. • Surgery and other therapies
• Other treatment options include laser therapy and
various surgical procedures. The following techniques
are intended to improve the drainage of fluid within
the eye, thereby lowering pressure:
• Laser therapy. Laser trabeculoplasty is an option if you
have open-angle glaucoma. It's done in your doctor's
office. Your doctor uses a small laser beam to open
clogged channels in the trabecular meshwork. It may
take a few weeks before the full effect of this
procedure becomes apparent.

40. • Filtering surgery. With a surgical procedure called a
trabeculectomy, your surgeon
creates an
opening in the white of the
eye (sclera) and removes
part of the trabecular meshwork.
Drainage tubes. In this
procedure, your eye
surgeon inserts a small
tube shunt in your eye to
drain away excess fluid to
lower your eye pressure.

41. Anatomy & physiology of Lens
• Definition Lens is a unique transparent, biconvex, avascular intraocular
structure along with the cornea, helps to refract (To change the
direction) light to be focused on the retina.
• Topography (A precise description of place)
The center of the anterior surface is called anterior pole and it is situated
3mm away from the posterior (endothelial) surface of cornea. The center
of the posterior surface is called posterior pole. The distance between
these poles is measured as lens thickness. The thickness of lens is 3mm at
birth, which increases to 6mm in older age.
• The marginal circumferences of the lens, where anterior and posterior
surface meet, are known as equator. The equatorial diameter of lens is 6.5
mm at birth, which reaches to 9-10 mm in adult life.
• Synonym: aquula (Latin, a little stream, of aqua, water) or crystalline
lens.
• Location:
The Lens is situated behind the iris and in front of the vitreous.

44. • Structure:
• The lens is part of the anterior segment of the human eye.
• In front of the lens is the iris, which regulates the amount
of light entering into the eye.
• The lens is suspended in place by the suspensory ligament
of the lens, a ring of fibrous tissue that attaches to the lens
at its equator and connects it to the ciliary body.
• Posterior to the lens is the vitreous body, which, along with
the aqueous humor on the anterior surface, bathes the
lens.
• The lens has an biconvex shape.
• The anterior surface is less curved than the posterior.

45. • Microanatomy
• The lens has three main parts: the lens capsule, the lens epithelium,
and the lens fibers.
• Lens capsule is the smooth, transparent outermost layer of the
lens,
• while the lens fibers are long, thin, transparent cells that form the
bulk of the lens.
• Capsule is synthesized by the lens epithelium
• The capsule is very elastic and so allows the lens to assume a more
globular shape when not under the tension of the zonular
fibers (also called suspensory ligaments)
• The capsule varies from 2 to 28 micrometres in thickness, being
thickest near the equator and thinnest near the posterior pole.

46. • 2- lens epithelium
• The lens epithelium, located in the anterior portion of the
lens between the lens capsule and the lens fibers, is
a simple cuboidal epithelium. The cells of the lens
epithelium regulate most of the homeostatic functions of
the lens. As ions, nutrients, and liquid enter the lens from
the aqueous humor, Na+/K+-ATPase pumps in the lens
epithelial cells pump ions out of the lens to maintain
appropriate lens osmotic concentration,
• Lens fibers
• The lens fibers form the bulk of the lens. They are long,
thin, transparent cells, firmly packed, with diameters
typically 4–7 micrometres and lengths of up to 12 mm long

48. • Blood supply & innervation:
• The lens has no blood supply or innervation after fetal development, and
it depends entirely on the aqueous humor to meet its metabolic
requirements and to carry off its wastes.
• Refractive power: (refractive=change direction as result of entering in
mdium fom another medium)
The diopteric power of human eye is approximately 58 diopters. The
refractive power of crystalline lens is about 15 diopters. Though lens has
less refractive power than cornea, it has the ability to change its shape
with the help of cilliary muscle, by which it can change its diopteric power,
allowing the distant and near vision. However this property changes with
age. Lens has a refractive index of 1.39 (1.36 in periphery and 1.40
centrally - a property which is termed as grading refractive index)
• Optical power (also referred to as dioptric power, refractive
power, focusing power, or convergence power) is the degree to which
a lens, mirror, or other optical system converges or diverges light

49. • Function:
• Accomodation: The lens is flexible and its curvature is controlled
by ciliary muscles through the zonules (ligaments). By changing the
curvature of the lens, one can focus the eye on objects at different
distances from it. This process is called accommodation.
• The inherent elastic property of the lens allows it to become more or less
spherical depending on the amount of tension exerted by the zonular
fibers on the lens capsule. Zonular tension is controlled by the action of
the parasympathetically innervated ciliary muscle
• When cilliary muscles contracts, relaxation of zonular tension occurs. The
lens then assumes a more spherical shape, resulting in increased dioptric
power which helps to bring nearer objects into focus.
• Ciliary muscle relaxation causes the zonular tension to increase. As a
result, lens flattens, which helps in bringing more distant objects into
view.

50. Crystallins and transparency
• Crystallins are water-soluble proteins that
compose over 90% of the protein within the lens.
• The three main crystallin types found in the
human eye are α-, β-, and γ-crystallins.
• Crystallins tend to form soluble, high-molecular
weight aggregates that pack tightly in lens
fibers,
• thus increasing the index of refraction of the lens
while maintaining its transparency.

51. Cataract eye
• Definition: cataract is a clouding of the normally
clear lens of your eye
• C= clear C= clouding C= cataract
• cloudy lenses is a bit like looking fogged-up window
• cataracts can make it more difficult to read, drive a car (especially at night) or
recognize face.

52. Types of cataracts
• Types of cataracts include:
• A subcapsular cataract occurs at the back of the lens. right in the path of
light. People with diabetes or those taking high doses of steroid
medications have a greater risk of developing a subcapsular cataract.
• A nuclear cataract forms deep in the central zone (nucleus) of the lens.
Nuclear cataracts usually are associated with aging. But with time, the lens
gradually turns more densely yellow. As the cataract slowly progresses,
the lens may even turn brown. Advanced yellowing or browning of the
lens can lead to difficulty distinguishing between shades of color
• A cortical cataract it effects edges of lens, is characterized by white,
wedge-like opacities that start in the lens and work their way to the center
in a streak fashion. This type of cataract occurs in the lens cortex, which is
the part of the lens that surrounds the central nucleus.

54. Cataract
• Mechanism:
• The lens focuses light that passes into your eye, producing clear, sharp
images on the retina the light-sensitive membrane in the eye that
functions like the film in a camera.
• As you age, the lenses in your eyes become less flexible, less transparent
and thicker.
• Age-related and other medical conditions The lens is mostly made of
water and protein. The protein is arranged in a precise way that keeps
the lens clear and lets light pass through it.
• But as we age, some of the protein may clump together and start to cloud
a small area of the lens. This is a cataract, and over time, it may grow
larger and cloud more of the lens, making it harder to see.
• As the cataract continues to develop, the clouding becomes denser and
involves a bigger part of the lens. A cataract scatters and blocks the light
as it passes through the lens, preventing a sharply defined image from
reaching your retina. As a result, your vision becomes blurred.

55. • Causes:
• Age: Age is the most common cause, Lens proteins denature and degrade over
time, and this process is accelerated by diseases such as diabetes
mellitus and hypertension.
• Trauma: Blunt trauma causes swelling, thickening, and whitening of the lens fibers.
While the swelling normally resolves with time, the white color may remain. In
severe blunt trauma, or in injuries that penetrate the eye, the capsule in which the
lens sits can be damaged. This damage allows fluid from other parts of the eye to
rapidly enter the lens leading to swelling and then whitening
• Radiation
• Cataracts can arise as an effect of exposure to various types of radiation. X-rays,
one form of ionizing radiation, may damage the DNA of lens cells. Ultraviolet light,
specifically UVB, has also been shown to cause cataracts, and some evidence
indicates sunglasses worn at an early age can slow its development in later life.
The protein coagulation caused by electric and heat injuries whitens the lens.This
same process is what makes the clear albumen of an egg become white and
opaque during cooking.

56. • Genetics: The genetic component is strong in the
development of cataracts. The presence of cataracts in
childhood or early life can occasionally be due to a
particular syndrome. Examples of chromosome
abnormalities associated with cataracts include 1q21.1
deletion syndrome
• 1q21.1 deletion syndrome
• is a syndrome caused by the deletion of a small
segment of chromosome 22. While the symptoms can
vary, they often include congenital heart problems,
specific facial features, frequent infections,
developmental delay, learning problems

57. 1q21.1 deletion syndrome

58. • Skin diseases
• The skin and the lens have the same embryological origin and so can be affected
by similar diseases.Those with atopic dermatitis and eczema occasionally develop
shield ulcer cataracts. Ichthyosis
• Smoking and alcohol
• Cigarette smoking has been shown to double the rate of nuclear sclerotic cataracts
and triple the rate of posterior subcapsular cataracts. Evidence is conflicting over
the effect of alcohol. Some surveys have shown a link, but others which followed
people over longer terms have not.
• Post-operative
• Nearly every person who undergoes a vitrectomy without ever having had cataract
surgery—will experience progression of nuclear sclerosis after the operation. This
may be because the native vitreous humor is different from the solutions used to
replace the vitreous. This may also be because the native vitreous humour
contains ascorbic acid which helps neutralize oxidative damage to the lens and
because conventional vitreous substitutes do not contain ascorbic acid.

59. • Medications
• Some medications, such as systemic, topical,
or inhaled corticosteroids, may increase the
risk of cataract development. Corticosteroids
most commonly cause posterior subcapsular
cataracts.

60. • Sign & Symptoms:
• Your vision is cloudy or blurry
• Colors look faded
• You can’t see well at night
• Lamps, sunlight, or headlights seem too bright
• You see a halo around lights
• You see double (this sometimes goes away as the
cataract gets bigger)
• You have to change the prescription for your
glasses often

61. • Risk factors
• Increasing age
• Diabetes
• Excessive exposure to sunlight
• Smoking
• Obesity
• Previous eye injury or inflammation
• Previous eye surgery
• Prolonged use of corticosteroid medications
• Drinking excessive amounts of alcohol
• Diagnosis: An eye doctor can check for cataracts as part of a dilated
eye exam. The exam is simple and painless your doctor will give
you some eye drops to dilate (widen) your pupil and then check
your eyes for cataracts and other eye problems.

62. • Treatment:
• When symptoms begin to appear, you may be able to improve your vision for a
while using new glasses, strong bifocals, magnification, appropriate lighting or
other visual aids.
• Think about surgery when your cataracts have progressed enough to seriously
impair your vision and affect your daily life.
• Many people consider poor vision an inevitable fact of aging, but cataract surgery
is a simple, relatively painless procedure to regain vision.
• During surgery, the surgeon will
remove your clouded lens and in
most cases replace it with a clear,
plastic intraocular lens (IOL).
IOL blocks both ultraviolet radiation
and high-energy visible blue light,
which research indicates may damage
the retina.

63. intraocular lens