Eye Diseases and Pharmacology

Ocular Anatomy and Drug Delivery

• Conjunctiva, AMD, diabetic retinopathy, and retinoblastoma represent conditions with varying effects on drug absorption, notably less impactful compared to the cornea.
• Certain macromolecular nanomedicines, peptides, and oligonucleotides can penetrate deeply into the eye through conjunctiva.
• Blood-ocular barriers, which include the blood-aqueous barrier (BAB) and blood-retinal barrier (BRB), limit the passage of xenobiotic compounds into the bloodstream.

Ocular Formulations and Administration

• Ocular formulations can be delivered via topical, intraocular, and periocular routes, or through ocular devices.
• Dosage forms include liquid, semi-solid (ointments and gels), solid (powders and inserts), or mixed (in situ gels).
• Most marketed ocular products (over 95%) are in liquid form.

Challenges in Ocular Drug Delivery

• Significant challenges include precorneal, corneal, and blood-corneal barriers that impede effective drug penetration.
• Prolonging drug residence time and ensuring proper ocular permeation have been ongoing scientific pursuits.

Nanotechnology and Ocular Drug Delivery

• Nanotechnology is becoming increasingly appealing for ocular drug delivery due to its ability to encapsulate both hydrophilic and lipophilic drugs.
• Advantages of nanocarriers include enhanced ocular permeability, increased drug stability, sustained residence time, and improved bioavailability.

Characterization Approaches

• Various in vitro, ex vivo, and in vivo characterization techniques help predict the performance of nanocarriers in drug delivery.
• Common in vivo models include rodents (rabbit, rat, mouse), while in vitro models utilize epithelial cells, reconstructed corneas, or excised corneas along with permeation chambers (Franz-type diffusion cell).

Ocular Retention and Bioavailability

• Ocular retention is critical as it minimizes dosing frequency and enhances bioavailability of ophthalmic drugs.

Safety and Irritation Metrics

• Ocular preparations with osmolality lower than 100 mOsm/kg or greater than 640 mOsm/kg are considered irritants.
• The normal range for osmolality in open eyes is between 231 to 446 mOsm/kg, restored shortly (within minutes) after administration of non-isotonic solutions.

This quiz covers various eye diseases such as age-related macular degeneration, diabetic retinopathy, and retinoblastoma, as well as the absorption of medications in the eye.