Ophthalmic preparation are Sterile product essentially free from foreign particle & meant for instillation into the eye in space between eye lid & eye balls.

or

Ophthalmic preparations are sterilized dosage forms designed to be instilled onto the external surface of the eye (topical), administered inside the eye (intraocular) or adjacent to it (periocular, e.g., juxtascleral or subtenon), or used in conjunction with an ophthalmic device (such as an intraocular lens).

Ophthalmic products include-
i) Eye drops
ii) Eye lotions
iii) Eye ointments
iv) Eye suspensions
v) Contact lens solutions

Characteristic of Eye/Ophthalmic Preparation

1. Clarity / foreign Particulate matter:-

• All the ophthalmic preparations  must free from foreign particles.
• Preparation must be clarified using Bacterial proof filler = 0.22 m
• Particle size in ophthalmic suspension – Ultrafine state of subdivision to minimize irritation (not more than 10 μm (micrometer)
• Preservative may absorb on filter paper during sterilization.
• A separate filter should use for different ophthalmic products to avoid the contamination.

Ophthalmic Suspension:- Large particle size – Favour retention in the cul-de-sac – Prolonged contact of drug, result into Larger duration of Action.

Disadvantage- Irritation

            Smaller particle size – more soluble – short duration of action

            So that optimal particle size – should <10 m

2. Viscosity:

• Various thickening agents are added in the ophthalmic preparation to prolong the contact time of the drug in the eye.
• Should be 15-25 cps.
• To prolong the contact time of drug in the eye using thickening agent
  • Polyvinyl agent (1-4%),
  • Polyethylene glycol
  • MC & CMC etc.
• Ophthalmic solution – Relatively brief contact time
• Thicking agent are not used in the formation of Eye lotion & drop

3. Tonicity:-

Ophthalmic products should be isotonic with lachrymal secretion to avoid irritation and discomfort.

• Eye can tolerate 0.5 to 2% of NaCl [Acceptable rane [0.7-1.5%]
• Preparation should be Isotonic with Lacrymal Secretion
• Tonicity Agent – NaCl, Boric Acid, KCl, dextrose, glycerine, Mannitol, PEG
• Occular tension is measured by – Tonometer

4. pH Buffers:-

Tears have the pH of 7.4. pH plays important role in therapeutic activity, solubility, stability and comfort to the patient. Eye can tolerate solution having wide range of pH provided they are not strongly buffered.

• pH =7.4, Boric Acid, Sodium citrate, Sodium Acid phosphates

5. Sterility:–

The most important properties of the ophthalmic preparation is that they must be sterile when prepared.

• All ophthalmic product must be sterile;
• Pyrogen free – not required

A very common gram negative bacteria named Pseudomonas aeruginosa which is generally present in the ophthalmic preparations. It may cause serious infection of cornea. It can cause total loss of eye sight within 24-48 hours.

6. Preservatives

• To maintain the sterility in multi-dose container containing ophthalmic preparation a suitable preservative is added. 

• Quaternary Ammonium Compounds:- Benzalkonium Chloride (Also have wetting property) – most commonly used (0.002 to 0.02%)
  • Incompatible with –
    • Nitrate,
    • Salicylates,
    • Anionic compounds
• Organic mercurials –
  • Phenylmercuric nitrate &
  • Phenylmercuric acetate         
  • 0.02% used instead of Benzalkonium chloride for Nitrate sylicylate incompatibility

• P-hydroxybenzoic acid:-
  • methyl paraben
  • Propyl paraben  (used to solubility of methyl paraben in H₂O)

• Aromatic Alcohol – Phenol

7. Anti-oxidants:-

1. Sodium thiosulfate (0.1- 0.2%)
2. Sodium metasulfate (0.05 – 0.5%)

8. Surface activity/wetting agent:-

The vehicles which are used in ophthalmic preparation must have good wetting ability to penetrate cornea and other tissues.

• Benzalkanium chloride, polysorbate (Non ionic); Free from surfactant – Toxicity                       
• Toxicity order: Anionic> Cationic> Non ionic

9. Container

• Glass container:
  • Sterile previously with Autoclave
  • Type –I / Borosillicate only
• Plastic container
  • Polyethylene, Sterile previously by Gamma Radiation or ethylene oxide
• Metal container
  • Aluminium – For ointment

Types of Ophthalmic Dosage Forms

1. Ophthalmic Solutions

• These are the most common dosage forms for delivering drugs to the eye. All ingredients are completely soluble uniformity.
• Ophthalmic Solutions has little physical interference with vision.
• Advantage:
  • Easy manufacturing and low cost as compared to other dosage design.
  • Ophthalmic solutions have potentially better/more dose uniformity.
  • More ocular bioavailability

• Disadvantage of solutions is their relatively brief contact time with the drug and the eye. Contact time can be increased by the inclusion of viscosity imparting agents like CMC.

2. Gel-Forming Solutions

• Ophthalmic solutions , which contain a polymer system that is a low-viscosity liquid in the container but gels on contact with the tear fluid. Such preparation increased contact time and can provide increased drug absorption and prolonged duration of therapeutic effect.
• Liquid-to-gel phase transition can be triggered by a change in temperature, pH, ionic strength, or presence of tear proteins, depending on the particular polymer system employed.

3. Ophthalmic Suspensions

Suspension dosage form offers the advantage of the ability to deliver a insoluble drug in an an aqueous solution.

• Suspensions are dispersions of finely divided, relatively insoluble drug substances in an aqueous vehicle containing suitable suspending and dispersing agents.
• Due to tendency of particles to be retained in the cul-de-sac, the contact time and duration of action of a suspension is more than that of an Ophthalmic solution.
• Particle size also plays an important part in the irritation potential of the dosing system. It has been recommended that particles be smaller than 10 microns to minimize irritation to the eye.

4. Ophthalmic Ointments

Ophthalmic ointments are primarily anhydrous and contain mineral oil and white petrolatum as the base ingredients.

• Yellow soft Paraffin:- ointment base
• Wool fat:- act as Emulsifier – help in absorption of active ingredient
• Liquid Paraffin – decrease Viscosity of base for easily expelled from tube.

Note: White soft paraffin – is not used in ointment base  because white soft paraffin is prepared Bleaching from yellow soft paraffin – Bleaching agent cause irritation to Eye.

Disadvantage:

• Ointments will interfere with vision, and so that they are used at bedtime instillation.
• drug content non uniformity
• not removed easily by tear fluid
• only bedtime administration

Advantage of Ointment: Longer contact time and greater total drug bioavailability but slower onset and time to peak absorption.

5. Ophthalmic Emulsions

An emulsion dosage form offers the advantage of the ability to deliver a poorly water-soluble drug in a solubilized form as an eyedrop. The drug is dissolved in a non-aqueous vehicle, such as castor oil, and emulsified with water, using a nonionic surfactant and, if needed, an emulsion stabilizer.

O/W emulsion is less irritating and better tolerated by the patient.

6. Ophthalmic Gels

Gel-forming polymers, such as carbomer, have been used to develop aqueous, semisolid dosage forms, which are packaged and administered the same as ointments.

Eg.: Carbomer gel of Pilocarpine administered at bed time has been shown to prolong the intraocular pressure lowering effect in patient for up to 24 hours

7. Ocular Inserts

Ocular inserts delivers the drug to eye by diffusional mechanism. Solid dosage form delivers an ophthalmic drug at a near constant known rate.

How to Use Eyedrops

1. Wash hands.
2. With one hand, gently pull lower eyelid down.
3. If dropper is separate, squeeze rubber bulb once while dropper is in bottle to bring liquid into dropper.
4. Holding dropper above eye, drop medicine inside lower lid while looking up; do not touch dropper to eye or fingers.
5. Release lower lid. Try to keep eye open and not blink for at least 30 seconds.
6. If dropper is separate, replace on bottle and tighten cap.

Contact Lens & Solution

There are basically four classes of lenses, and the identification of these classes is both by polymer type and lens characteristics: hard contact lenses, RGP contact lenses, soft hydrophilic contact lenses, and silicone-based flexible hydrophobic lenses.

Contact Lens Care Products

Wetting Solutions

These are lubricating and cushioning preparations designed to provide hydrophilic coating over the hydrophobic surface of PMMA, silicon, acrylate, and other rigid lens surfaces. Wetting solutions contains viscosity-imparting agent, a surfactant, and a preservative.

Soaking Solutions/ Storage solution

This solution serve in storage and hydration of hard or RGP lenses but, most importantly, in disinfection of such lenses. Soaking solutions contain chlorhexidine (gluconate), benzalkonium, or quaternary compounds. Soaking solutions are intended to be rinsed off lenses before insertion.

Cleaning Solutions

These solutions are used to remove surface contaminants— lipids, protein, organic salts, and the like. Cleaning is accomplished by the use of surfactants that preferably are nonionic or amphoteric.

Rewetting Solutions

Solutions intended to rewet hard or RGP lenses in situ are referred to as rewetting solutions or lubricating drops. Form normal tear film on lens.

Disinfecting Systems

Also Read… Evaluation of ophthalmic product

Evaluation of ophthalmic product