The sclera: The protective outer layer of the eye, referred to as the“white of the eye” and it maintains the shape of the eye.The cornea: The front portion of the sclera, is transparent andallows light to enter the eye. The cornea is a powerful refractingsurface, providing much of the eyes focusing power.The choroid is the second layer of the eye and lies between thesclera and the retina. It contains the blood vessels that providenourishment to the outer layers of the retina.The iris is the part of the eye that gives it color. It consists ofmuscular tissue that responds to surrounding light, making thepupil, or circular opening in the center of the iris, larger or smallerdepending on the brightness of the light.
The lens is a transparent, biconvex structure, encased in a thintransparent covering. The function of the lens is to refract andfocus incoming light onto the retina.The retina is the innermost layer in the eye. It converts imagesinto electrical impulses that are sent along the optic nerve to thebrain where the images are interpreted.The macula is located in the back of the eye, in the center of theretina. This area produces the sharpest vision.
The inside of the eyeball is divided by the lens into two fluid-filledsections.The larger section at the back of the eye is filled with a colorlessgelatinous mass called the vitreous humor.The smaller section in the front contains a clear, water-likematerial called aqueous humor.The conjunctiva is a mucous membrane that begins at the edge ofthe cornea and lines the inside surface of the eyelids and sclera,which serves to lubricate the eye.
The eye is made of cells that arecalled Rods and Cones. Cone cellsare coned shaped and Rod cellsare rod shaped.Most highly concentrated on thefovea – an area of the retina thatlacks rods.Photoreceptors ofthe retina:rod cells - lightsensitive but donot distinguishcolors.cone cells - notas light sensitiveas rods butprovide colorvision
Light energy enters your eye, and the cornea andlens focus it onto the retina.b. The light stimulates the rods and cones, twotypes of cells found in your retina.c. The rods and cones send impulses to the opticnerve, which carries them to the visual area of thecortex.d. Your cortex interprets the image and you “see.”Physiology of Vision
Accommodation is thefocusing of light in the retina.Mammals focus by changingthe shape of the lens:-The lens is flattened fordistant objects.-The lens is rounded for nearobjects.Focusing Light
common disorders of the eye canbe self-treated• Blepharitis: Blepharitis is a common conditionthat is caused by inflammation of the eyelid.• applying hot compresses to the affected eye,followed by an eyelid scrub.• Treat with Antibiotic
• Lice: It is common in young school-agechildren.• ointment is applied to the eyelid.
• Contact dermatitis: is an inflammation ofthe skin that causes swelling, scaling, orredness of the eyelid with intense itching.• triggered by the use of a new product(soap or makeup) or exposure to aforeign substance.• Antihistamines that are taken by mouth.
• Superficial foreign bodies: Lint, dust, aneyelash, or other foreign matter canbecome stuck in the eye. When thesubstance cannot easily be removedeither with your finger, water, or an eyeirrigating solution
• Thermal damage: Thermal damage is a burninjury to the eye itself. Exposure to the sunsUV radiation during outdoor activities is anexample of minor ocular thermal damage.• An eye lubricant can be applied to soothe theeye.
• Conjunctivitis: Bacteria, viruses, fungi, allergicsubstances, or inflammation-promotingagents.• The inflammation causes enlargement of theblood vessels in the conjunctiva.• treated with ocular decongestants.
• Dry eye: Dry eye is characterized by a white ormildly reddened eye combined with a sandy,gritty, dry feeling.• eye drops.
• Hordeolum: Commonly referred to as a sty, isan inflammation of the glands within theeyelid, typically with infection.• Treatment usually is with hot compressesseveral times per day.
• Chalazion: A chalazion looks similar to ahordeolum. It is a raised nodule without thetenderness of a hordeolum and no infection.• it is treated with hot compresses.
types of OTC eye care products• Artificial tear drops: Lubricants (also calledartificial tears) ,water-based solutions that areused to lubricate the eye and thicken tears.• available in a preservative-free (PF) form.Artificial tears usually are used two to fivetimes a day as needed for relief of symptoms.
• Ointments or emollients: useful lubricants.These products are not water-based andcontain lubricating ingredients similar topetroleum jelly.• These ointments cause visual blurringimmediately after their use. Therefore, theyare often used only prior to sleep.
• Eye washes: Eye washes (also known as ocularirrigants) are used to cleanse and/or rinsedebris from the eye. These products arebalanced to the proper acidity and electrolyteconcentration so as to be non-irritating to theeye.
• Scrubs: Eyelid scrubs are useful forremoving oils, debris, or loose skin thatcan be associated with eyelidinflammation. Soap agents provide thefoaming action.
• Decongestants: used to shrink swollen bloodvessels in the congested (red) eye. for example, inconjunctivitis.• Patients at risk for angle-closure glaucoma shouldcautiously use phenylephrine because it cancause an attack of the disease• Phenylephrine has sideeffects with many drugs• imidazoles: longer acting than phenylephrine andhave fewer side effects
• Antihistamines: Ocular antihistamines areavailable OTC. These antihistamines arecombined with ocular decongestants for thetreatment of congestion (conjunctivitis),particularly when caused by allergy.• Pheniramine maleate and antazoline bothblock histamine receptors in the eye
• Newer allergy eye-drop preparations:Recently, new classes of eye drops for thetreatment of itching due to allergy havebecome available over the counter. Zaditor, anonsteroidal anti-inflammatory drop, is anexample of these.
inactive ingredients• Vehicles: is added to a product to enhancedrug action by increasing the viscosity(thickness) of the product.• Examples of ophthalmic vehicles are Dextran70, gelatin, glycerin, poloxamer 407, andpropylene glycol.
• Preservatives: included to destroy or limitgrowth of bacteria that may be introducedinto the product during repeated use.• Examples of ophthalmic preservatives arebenzalkonium chloride (BAK), cetylpyridiniumchloride, chlorobutanol, methylparaben,sodium benzoate, and sorbic acid.
• Excipients: substance that is added to providephysical form to the product, make it lessirritating to the eye, or to preserve theingredients within the product.• Useful ophthalmic excipients are antioxidants,wetting agents, buffers, and tonicity adjusters.
Contact lens• Corrective contact lensesare designed to improve vision, most commonlyby correcting refractive error.• Cosmetic contact lensesdesigned to change the appearance of the eye.• Therapeutic contact lensesSoft lenses are often used in the treatment andmanagement of non-refractive disorders of theeye. dry eyes, corneal abrasions and erosion,
care• Saline solution• Daily cleaner:Used to clean lenses on a daily basis. A fewdrops of cleaner are applied to the lens whileit rests in the palm of the hand.