Aqueous Humour

Ophthalmology

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

4. aqueous humour fills both the anterior and the posterior chambers of the eye. Aqueous humor produced and secreted into the posterior eye segmen t 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

5. 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

6. 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.

7. 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.

8. Drainage

9. 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

10. M aintenance 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.

11. 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 .

12. Tonometer  

13. 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 ( μ L/min) U the resorption of aqueous humour through the uveoscleral route (in μ L/min) C is the facility of outflow in microliters per minute per millimeter of mercury ( μ L/min/mmHg) Pv the episcleral venous pressure in millimeters of mercury (mmHg).

14. 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.

15. F actors 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.

16. 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 .

17. 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 .

18. 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.

19. سبز موتیا Glaucoma Causes: Glaucoma is the result of damage to the optic nerve . As this nerve gradually deteriorates, blind spots develop in your visual field . T his 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.

20. 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

21. 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.

22. 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.

23. 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.

24. 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

25. 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.

26. 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

27. 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 )

28. P achymetry 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.

29. 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

30. 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.

31. 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.

32. 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 .

33. 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.

34. 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.

35. 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 .

36. 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.

37. 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.

38. Microanatomy The lens has three main parts : the lens capsule, the lens epithelium, and the lens fibers. L ens 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 .

39. 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

40. 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

41. 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 .  

42. 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 .

43. 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.

44. 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.

45. C ataract 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.

46. 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.

47. 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 

48.  1q21.1 deletion syndrome

49. 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.

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

51. 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

52. 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.

53. 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.

54. intraocular lens