The Structure Of The Eye:
The eyes are complex sensory organs. They are designed to optimize vision under
conditions of varying light. Their location, on the outside of the face, makes
them susceptible to trauma, environmental chemicals and particles, and
infectious agents. The eyelids are the major protective mechanism for the eye.
The eye consists of the eyeball, the upper and lower eyelids, and the
conjunctivas. The eyeball consists of a clear, transparent dome at the front
(the cornea) that is surrounded by the white of the eyeball (the sclera). The
iris of the eye is the circular, colored portion within the eyeball and behind
the cornea, and the pupil is the central opening within the iris. Behind the
iris and pupil is the eye's lens.
The inner sides of the eyelids which touch the eyeball, are covered by a thin
membrane (the palpebral conjunctiva) that produces mucus to lubricate the eye.
This thin membrane folds back on itself and covers the visible sclera of the
eyeball. (This continuation of the palpebral conjunctiva is called the bulbar
conjunctiva.) The tissue between the skin of the eyelid and the palpebral
conjunctiva is filled with glands that secrete sebum, an oily substance that
provides additional lubrication for the eye. Tears are formed by the lacrimal
gland in the upper, outer corner of the eye and are collected and drained by
the lacrimal sac in the inner, lower corner of the eye.
Common Disorders Of The Eye:
Blepharitis: Blepharitis is a common condition that is caused by
inflammation of the eyelid. It results in red, scaly, and thickened eyelids and
typically some loss of the eyelashes. Blepharitis may be due to either
Staphylococcus epidermidis or Staphylococcus aureus (types of bacteria), or
seborrheic dermatitis (a type of skin inflammation of unknown cause), or a
mixture of the two. The most common complaints are itching and burning.
Blepharitis is initially treated by applying hot compresses to the affected
eye, followed by an eyelid scrub. If the condition persists, you should see the
doctor, who may prescribe antibiotics.
Lice: The eyelids can become infested with one of two different lice,
the crab louse (Phthirus pubis) or the head louse (Pediculus humanus capitis).
Lice in the eyelids cause symptoms and signs that are similar to those of
blepharitis (red, scaly, and thickened eyelids, usually with some loss of the
eyelashes). Petrolatum or a non-medicated ointment is applied to the eyelid and
suffocates the lice eggs. RID, NIX, A-2000 or any other preparation that is
designed for use in the hair should not be used near the eyes.
Contact dermatitis: Contact dermatitis is an inflammation of the skin
that causes swelling, scaling, or redness of the eyelid with intense itching.
This condition usually is triggered by the use of a new product (soap or
make-up) or exposure to a foreign substance. If both the upper and lower
eyelids are affected, the cause of the inflammation is likely to be an allergic
reaction. Antihistamines that are taken by mouth can be used to treat contact
dermatitis of the eyelid.
Foreign substance: Lint, dust, an eyelash or other foreign matter can
become stuck in the eye. When the substance cannot easily be removed either
with your finger, water, or an ophthalmic irrigant, a doctor should be seen.
Thermal damage: Thermal damage is a burn injury to eye itself. Exposure
to the sun's UV radiation during outdoor activities is an example of minor
ocular thermal damage. An eye lubricant can be applied to soothe the eye. If
there is no relief to the eye after 24 hours, a physician should be seen. An
injury to the eye, for example, from a welder's arc, warrants the immediate
attention of a doctor.
Conjunctivitis: Bacteria, virus, allergy, or inflammation- promoting
agents can cause inflammation of the palpebral and bulbar conjunctiva, also
known as conjunctivitis. The inflammation causes enlargement of the blood
vessels in the conjunctiva ("congestion") and causes the conjunctiva to become
red ("blood-shot"). Itchy eyes may or may not accompany the inflammation. The
congestion and itchiness can be treated with ocular decongestants, but the
underlying cause may need treatment as well.
Dry eye: Dry eye is characterized by a white or mildly reddened eye
combined with a sandy, gritty feeling. Unlike the name implies, dry eye is
accompanied by excessive tearing. Abnormalities of the tears or the lubricants
of the eye themselves are thought to reduce the effectiveness of the
lubrication. The resulting inadequate lubrication stimulates an increase in the
production of tears. Other factors thought to contribute to dry eye are aging
and some drugs such as antihistamines, antidepressants, or diuretics (water
pills). A different type of dry eye can occur when the flow of tears is reduced
because of inflammation and destruction of the lacrimal glands
(keratoconjunctivitis sicca). Although lubricants are effective for treating
dry eye, a physician also should be consulted.
Hordeolum: Commonly referred to as a sty, a hordeolum is an inflammation
of the glands within the eyelid. The primary sign of a hordeolum is a tender,
raised nodule on the eyelid. Sometimes, the eyelid is so swollen that the eye
appears to be completely shut. A hordeolum is usually caused by the same
bacteria that are linked to blepharitis. Treatment usually is with hot
compresses several times per day, but if the problem worsens or does not clear
within a week, a physician should be seen. Antibiotics may be necessary.
Chalazion: A chalazion looks similar to a hordeolum. A chalazion is a
raised nodule without the tenderness of a hordeolum. Like a hordeolum, it is
treated with hot compresses. If the chalazion persists, a physician should be
What common eye conditions usually require treatment by a doctor?
Trauma: Blunt trauma to the eye requires immediate evaluation by an
ophthalmologist or optometrist. Trauma to the eye can activate bleeding into
the eye from ruptured blood vessels or cause detachment of the retina. Both
situations can seriously impair vision.
Abrasion: An abrasion usually occurs when a fingernail or metallic
foreign object rubs across the cornea or conjunctiva. There is a risk of
bacterial or fungal contamination and infection following an eye abrasion.
Chemical exposure: Exposure of the eye to household cleaning solutions, fumes,
or an actual chemical splash requires immediate evaluation by a physician,
though initially it may be self- treated with water or an irrigant.
Keratitis: Keratitis is an inflammation of the cornea that may occur
alone or simultaneously with conjunctivitis. The symptoms of keratitis include
blurred vision, pain, and intolerance to light (photophobia).
Corneal swelling: Corneal swelling, or edema, is a condition in which fluid
accumulates in the cornea. The edema causes visual disturbances such as halos
or starbursts around lights. Reduced vision may or may not occur. Corneal
swelling can arise as a complication of contact lenses, surgical damage to the
cornea, or an inherited defect. Hyperosmotics are used to treat corneal
swelling, but additional treatment by a physician may be necessary.
Uveitis: Uveitis is an inflammation of the eye structures in the uveal
tract (the iris and other structures within the eye to which the iris
attaches). Uveitis may occur without an obvious cause or may be due to trauma
or an inflammatory disease in other parts of the body. Symptoms and signs of
uveitis are similar to those of conjunctivitis and keratitis.
Angle-Closure Glaucoma: This disorder usually is triggered after an eye
exam in which the pupils have been dilated. Angle- closure glaucoma is due to
an obstruction of the canal system that drains fluid from the inside of the
eye. As a result, fluid accumulates and the pressure within the eye increases.
Patients may have a tendency to develop angle-closure glaucoma because of an
anatomical defect in their eye. Common symptoms include an aching eyebrow or a
headache that leads to nausea and vomiting. Angle-closure glaucoma should be
suspected if symptoms develop after an agent is used to dilate the pupils for
an eye exam.
OTC Eye-Care Products
There are seven types of OTC eye-care products available. Each product contains
one or more active and inactive ingredients.
What Inactive Ingredients Are Contained In OTC
Eye Care Products?
Artificial tears: Lubricants--also called artificial tears--are
synthetic (man-made), water-based solutions that are used to lubricate the eye
and thicken tears. Artificial tears are formulated as solutions or drops. The
components in artificial tears that provide the lubrication include cellulose
ethers (hydroxymethylcellulose or HPMC), polyvinyl alcohol or PVA, povidone or
PVP and retinol solutions (containing vitamin A). Examples of artificial tears
include Akwa Tears (drops), Tears Naturale, and Refresh Tears. Artificial tears
usually are administered three times daily.
Ointments or Emollients: Ointments also are useful lubricants. These
products are not water-based and contain lubricating ingredients similar to
petroleum jelly. Examples of ointments include DuraTears Naturale, Lacri-Lube,
and Refresh PM. Their advantage over a water-based solution containing HPMC,
PVA or PVP is that they remain in the eye longer. Emollients usually are used
twice a day.
Eye washes: Eye washes--also known as ocular irrigants--are used to
cleanse and/or rinse debris from the eye. These products are balanced to the
proper acidity and electrolyte concentration so as to be non-irritating to the
eye. Washes are available as liquids, solutions or drops. These products may
contain boric acid with sodium borate, sodium phosphate, or sodium hydroxide to
maintain the proper acidity. Examples of washes include AK Rinse, Dacriose, and
Hyperosmotics: Hyperosmotics are used to treat corneal swelling.
Hyperosmotics draw water out of the cornea and thus reduce corneal swelling.
Most OTC hyperosmotics contain sodium chloride in various concentrations as
either a solution or an ointment. The 2% solution tends to cause less stinging
and burning than the 5% solution. An example of a hyperosmotic for corneal
swelling is Adsorbon a C.
Scrubs: Eyelid scrubs are useful for removing oils, debris, or loose
skin that can be associated with eyelid inflammation. Soap agents PEG-200
glycerol tallowate or PEG-80 glycerol cocoate provide the foaming action. An
example of this type of product is Eye-Scrub.
OTC products may contain lubricants alone or lubricants combined with
medications usually as medicated eye drops. The medicated eye drops may contain
decongestants or antihistamines.
Decongestants: Decongestants are used to shrink swollen blood vessels in
the congested (red) eye, for example, in conjunctivitis. Phenylephrine is the
most common decongestant for this purpose. Patients with angle-closure glaucoma
should cautiously use phenylephrine because it can cause an increase in
pressure within the eye. Rebound congestion, in which blood vessels become
dilated even with continued use of decongestants, is a common side effect of
phenylephrine. Therefore, if no improvement in redness or symptoms occurs
within 72 hours of use, phenylephrine should be discontinued. A frequent side
effect of phenylephrine is dilation of the pupils. If phenylephrine is
absorbed from the eye into the body, an increase in blood pressure may occur,
although this is rare. Nevertheless, patients with high blood pressure should
be cautious in using phenylephrine. Additionally, if phenylephrine is absorbed,
side effects may occur due to interactions with atropine, tricyclic
antidepressants (Imipramine) and monoamine oxidase inhibitors such as
phenelzine sulfate (Nardil) or tranylcypromine sulfate (Parnate), reserpine
(Hydropres), guanethidine (Ismelin), or methyldopa (Aldomet).
A second group of chemical decongestants are the imidazoles (naphazoline,
tetrahydrozoline, and oxymetazoline). Imidazoles are longer acting than
phenylephrine and have fewer side effects, including rebound congestion.
Caution still is recommended with imidazoles because of the potential for an
increase in blood pressure. Of the three imidazoles, oxymetazoline generally
appears to exhibit the least side effects. Naphazoline may dilate pupils more
in persons with lightly pigmented (blue or green) eye.
Examples of medicated eye drops containing decongestants are Naphcon, Prefrin,
and Opcon A.
Antihistamines: Ocular antihistamines are available OTC. These
antihistamines are combined with ocular decongestants for the treatment of
congestion (conjunctivitis), particularly when caused by allergy. Pheniramine
maleate and antazoline both block histamine receptors in the eye, and thus
provide relief from the symptoms of itchy, watery eyes. Antazoline may increase
pressure slightly in the eye (of concern to patients with glaucoma) whereas
pheniramine maleate has little effect on pressure. Common side effects of
antihistamines include burning, stinging, and discomfort in the eye. Important
side effects that may be associated with oral antihistamines have not been
reported with ocular antihistamines. Antihistamines should not be used in
patients at risk for developing angle-closure glaucoma. Examples of products
that combine an antihistamine and decongestant are Naphcon A and Ocuhist.
Most eye care products contain ingredients that have no therapeutic value. If an
individual has a known sensitivity to one or more of these ingredients, then
products containing them should be avoided:
Vehicles: An ophthalmic vehicle is added to a product to enhance drug action by
increasing the viscosity (thickness) of the product. Examples of ophthalmic
vehicles are Dextran 70, gelatin, glycerin, poloxamer 407, and propylene
Preservatives: Preservatives are included to destroy or limit growth of
bacteria that may be introduced into the product during repeated use. Examples
of ophthalmic preservatives are benzalkonium chloride (BAK), cetylpyridinium
chloride, chlorobutanol, methylparaben, sodium benzoate, and sorbic acid. To
avoid allergies, many ophthalmic products are preservative free.
Excipients: An excipient is a substance that is added to provide physical form
to the product, make it less irritating to the eye, or to preserve the
ingredients within the product. Useful ophthalmic excipients are antioxidants,
wetting agents, buffers, and tonicity adjusters.