6. artificial tear substitutes

most common causes of dry eye

environment, age, allergy

What is a TearLab osmometer?

uses electrical impedance to measure tear osmolarity in milimoles per mililitre

What osmolarity values is indicative of dry eye?

values greater than 308mOsmsL

What is InflammaDry (RPS)?

measures the level of a matrix metalloprotinase MMP-9 (i.e. a proteolytic enzyme) in nanograms per milliliter that can be produced in dry eye

What levels of a matrix metalloprotinase are indicative of dry eye?

values ≥ 40ng/mL

What age range is dry eye most common?

>50

When should dry eye be reffered?

Severe/recurrent/persistent cases

Aqueous Deficiencies:

Adequate production and drainage of the aqueous layer is necessary for the maintenance of

1. tear nutrients (e.g oxygen and electrolyte supply to the cornea) and antibacterial agents (i.e. lysozyme produced by the major and accessory lacrimal glands)

2. moist conditions on the eye surface (evaporation reduces surface temperature)

3. the mechanical flushing action of tear movement

how can aqeuous deficiencies cause dry?

Aqueous deficiencies may be partial or absolute but invariably produce marked symptoms of soreness or burning. The osmolarity of the aqueous increases in dry eye and the resulting hypertonocity leads to ocular damage.

how do mucus defiencies cause dry eye?

Mucus-secreting cells create a mucin layer which coats the cornea and protects its surface. An unstable tear film will result from deficiencies in secretion of the soluble surfactant mucin even if there is sufficient aqueous (surfactants are surface-acting agents that reduce surface tension). A reduction in goblet cell density will alter the integrity of the mucous layer and lead to abnormal TBUTs.

how do lipid defiencies cause dry eye?

The lipid layer reduces the evaporation of aqueous. Meibomian gland secretions can be diminished by hydrolysis due to the secretion of the enzyme lipase by certain bacteria. A characteristic of lipid abnormality is a decrease in the rate of spreading of the tear film which results in a rapid TBUT. Lipid abnormality has been associated with chronic blepharitis.

how can reduced lid movement lead to dry eye?

The shear forces associated with lid-globe contact during blinking is important with respect to mucus distribution. Restricted lid movement can, therefore, lead to serious tear deficiency and exposure keratitis

What is Epitheliopathy?

An irregular corneal epithelium (due, for example, to corneal lesions or altered corneal neural/physiological integrity as in keratoconus) can produce a thin and unstable tear film.

what systemic medications can cause dry eye

e.g. CNS acting drugs and beta-blockers for heart conditions

what secondary systemic or dermalogical diseases can cause dry eye

Autoimmune connective tissues disorders such as rheumatoid arthritis are of particular note

Dermatological conditions that may be associated with dry eye are: acne rosacea, seborrhoeic dermatitis and psoriasis and Sjögen's syndrome

What are the main vehicles for ocular lubricants?

multidose, single dose and gels

How is Acetylcysteine classified?

Is a mucolytic and a POM medicine (under the 'Additional Supply' legal category)

How does acetylcysteine work?

stings a great deal and is thought to act by uncoupling disulphide linkages in mucus which reduces mucus viscosity. it can help resolve filamentary. keratitis

What are carbomers?

semi-solid formulations (e.g. Carbomer 940 & Carbomer 974) of high molecular weight polymers of acrylic acid

What are the properties of carbomers that make them good tear substitutes?

• Drop frequency can be reduced from 20x to ~4x per day,

• Reduce natural elimination of tears

• Retention time is reported to be ~ 7x > than that for polyvinyl alcohol,

• Protective effect during sleep

• Reduced risk of allergy to benzalkonium chloride has been reported

What is carmellose sodium?

a high-molecular weight formulation of methylcellulose which makes it unlikely to penetrate the healthy cornea and provides sustained contact (up to 22mins).

What is Hydroxyethylcellulose?

A substituted cellulose ether - these are colloids which dissolve in water to produce colourless solutions of varying viscosity and have emollient and cohesive properties.

What is Hydroxyethylcellulose used for other than artificial tear and how do they work ?

the wetting of contact lenses and to prolong contact time of ocular drugs.

A substituted cellulose ether – these are colloids which dissolve in water to produce colourless solutions of varying viscosity and have emollient and cohesive properties.

How is the Minims of Hydroxyethylcellulose formulated?

hyetellose 0.44% w/w BP and sodium chloride EP 0.35% w/w.

What is Hypromellose?

traditional choice of treatment for tear deficiency. Full name is hydroxypropyl methylcellulose (HPMC) and is classed as a cellulose ether. most widely used

What is liquid paraffin and when is it used?

May be used to lubricate the eye surface, especially in cases of recurrent corneal epithelial erosion. May cause 'blurry' vision and are best suited for application before sleep; should not be used during contact lens wear

What are Macrogols?

use a novel pH-sensitive hydroxypropyl-guar polymer component that becomes more viscous when exposed to the pH of the ocular surface.

What is Paraffin, yellow soft?

Bland ointment formulations are semisolid preparations of petrolatum and mineral oil which may also have lanolin added.

How does Paraffin, yellow soft work?

The preparations melt at eye temperature and are retained for longer periods than other tear preparations.

What is problem with paraffin, yellow soft?

Blurred vision so only used at night

What does Polyvinyl alcohol do?

Increases the persistence of the tear film and is useful when surface mucin is reduced.

What are 'comfort drops' classified as?

medical device

What is minims artificial tears made up of?

a combination of sodium chloride and hyetellose

What is Sodium hyaluronate?

A viscoelastic high-molecular weight polysaccaride polymer

What does Sodium hyaluronate do?

• Increases goblet cell density and reduces inflammation of the ocular surface in dry eye

• The viscoelastic properties lubricates and protects the ocular surface

• It also improves tear film stability and corneal wettability.

What is Soy bean oil?

a natural oil eye drop emulsion indicated for use in the treatment of dry eyes and reducing tear evaporation

Which tear substitutes are most widely used?

hypromellose (38%) followed by carbomers (29%).

give 7 Alternatives to Artificial Tear Substitutes:

1. Change ocular environment (adjust heating, ventilation, humidity).

2. Dietary manipulation (Omega-3/-6 fatty acids).

3. Punctal occlusion.

4. Hot compresses e.g. the EyeBag.

5. Corticosteroids (short 2-week courses).

6. NSAIDs (reduce formation of endogenous prostaglandins).

7. Hormone supplements (e.g., androgens, not generally used).

what are the 5 examples of preparations for dry eye symptom

• povidone

• theratears

• actmist spray

• rohto drops

• thealoz duo

what is Povidone a mixture of and how does it work?

Polyvinyl pyrrolidine, a mixture of linear synthetic polymers

functions as a non-ionic surfactant and in a concentration of 3-5% increases the viscosity of solutions.

Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid. Surfactants may act as detergents (which help emulsify lipids and some organic deposits) or wetting agents

how does TheraTears work?

A low osmolarity preparation: dry eye and consequent corneal epithelium damage can be linked with hyperosmolarity of the tear film.

how does Actmist spray work?

A liposomal spray that is directed onto the closed lids and is thought to act by increasing local humidity around the lids.

how does Rohto lubricating eye drops work?

-contains a bi-polymer formed from two naturally occurring polysaccarides: hyaluronic acid and tamarind seed polysaccaride

how does Thealoz Duo work?

a natural disaccharide that preserves epithelial cell life in dry conditions. Available as a preservative-free preparation and combined with hyaluronic acid.