Introduction: Ocular drug delivery systems address unique challenges of delivering therapeutics to the eye, balancing anatomy, physiology, and formulation science. B.Pharm students must understand corneal and conjunctival barriers, tear turnover, limited ocular bioavailability, and routes such as topical, periocular, and intravitreal. Key topics include formulation types (solutions, suspensions, gels, ointments, inserts, implants), sustained-release systems, mucoadhesive polymers, nanoparticles, liposomes, prodrugs, sterilization, preservative safety, pharmacokinetics, and patient compliance. Practical challenges include enhancing corneal permeability, prolonging residence time, avoiding toxicity, and ensuring sterility and stability. This overview prepares you for applied questions and formulation strategies. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary anatomical barrier that limits drug penetration from topical eye drops into the anterior chamber?
- Conjunctival blood vessels
- Corneal epithelium
- Tear film lipid layer
- Sclera thickness
Correct Answer: Corneal epithelium
Q2. Which property most directly increases corneal permeability of a small drug molecule?
- High molecular weight
- High lipophilicity
- High ionization at tear pH
- Strong P-glycoprotein substrate activity
Correct Answer: High lipophilicity
Q3. Which route provides the highest intraocular drug concentrations for posterior segment diseases?
- Topical administration
- Systemic oral administration
- Intravitreal injection
- Periocular (subconjunctival) injection
Correct Answer: Intravitreal injection
Q4. Which formulation approach is commonly used to prolong precorneal residence time?
- Use of low-viscosity solutions
- Inclusion of mucoadhesive polymers
- Decreasing osmolarity drastically
- Adding large amounts of surfactant
Correct Answer: Inclusion of mucoadhesive polymers
Q5. Which polymer is widely used as a mucoadhesive in ocular gels?
- Polyvinylpyrrolidone (PVP)
- Carbopol (Carbomer)
- Polyethylene glycol 400 (PEG 400)
- Poloxamer 407 at low concentration
Correct Answer: Carbopol (Carbomer)
Q6. What is the main disadvantage of using benzalkonium chloride (BAK) as a preservative in chronic ocular therapy?
- It increases drug solubility excessively
- It causes corneal epithelial toxicity with long-term use
- It enhances intraocular penetration dramatically
- It prevents sterilization of multi-dose bottles
Correct Answer: It causes corneal epithelial toxicity with long-term use
Q7. Which release mechanism is typical for non-biodegradable ocular implants?
- Enzymatic degradation
- Diffusion-controlled release through polymer matrix
- Immediate bolus release then no further release
- Osmotically-driven pulsatile release only
Correct Answer: Diffusion-controlled release through polymer matrix
Q8. Which technique is most appropriate for sterilizing heat-sensitive ocular nanoparticles in solution?
- Autoclaving at 121°C
- Gamma irradiation without validation
- Sterile filtration through 0.22 μm filter
- Dry heat sterilization at 160°C
Correct Answer: Sterile filtration through 0.22 μm filter
Q9. A prodrug approach for ocular delivery is mainly used to:
- Increase formulation viscosity
- Mask bitter taste of eye drops
- Enhance corneal permeability or reduce irritation
- Reduce drug half-life in tear fluid
Correct Answer: Enhance corneal permeability or reduce irritation
Q10. Which in vivo test measures tear production relevant for ocular formulations?
- Tonometry
- Schirmer’s test
- Optical coherence tomography (OCT)
- Electroretinography (ERG)
Correct Answer: Schirmer’s test
Q11. What role do cyclodextrins play in ocular drug formulations?
- Act as preservatives
- Form inclusion complexes to increase solubility and reduce irritation
- Decrease corneal permeability
- Function as mucoadhesive polymers
Correct Answer: Form inclusion complexes to increase solubility and reduce irritation
Q12. Which parameter is most used to quantify ocular bioavailability after topical dosing?
- Maximum tolerable volume instilled
- Area under the concentration–time curve (AUC) in ocular tissues
- Surface tension of the formulation
- Viscosity index at shear 10 s−1
Correct Answer: Area under the concentration–time curve (AUC) in ocular tissues
Q13. Which efflux transporter expressed in corneal epithelium can reduce ocular drug absorption?
- GLUT1
- P-glycoprotein (P-gp)
- Na+/K+-ATPase
- Carbonic anhydrase
Correct Answer: P-glycoprotein (P-gp)
Q14. Gel-forming in situ systems for the eye typically undergo sol-to-gel transition triggered by:
- Elevated temperature or ionic changes in tears
- Decrease in ambient humidity
- Exposure to UV light only
- Mechanical shear from blinking exclusively
Correct Answer: Elevated temperature or ionic changes in tears
Q15. Which ocular diagnostic method can quantify drug penetration using fluorescent probes?
- Fluorophotometry
- Confocal Raman spectroscopy only
- Magnetic resonance imaging (MRI) routinely
- Standard slit-lamp microscopy
Correct Answer: Fluorophotometry
Q16. For sustained posterior-segment delivery, biodegradable intravitreal implants commonly use which polymer?
- Polylactic-co-glycolic acid (PLGA)
- Sodium chloride
- Ethylcellulose at high melting point
- Polyvinyl alcohol (PVA) non-degradable alone
Correct Answer: Polylactic-co-glycolic acid (PLGA)
Q17. Which factor does NOT typically reduce ocular residence time of an instilled drop?
- High tear turnover
- Reflex lacrimation
- Increased formulation viscosity
- Blinking frequency
Correct Answer: Increased formulation viscosity
Q18. An advantage of contact lens-mediated drug delivery is:
- Immediate drug elimination by tears
- Prolonged drug residence and controlled release to cornea
- Inability to control release kinetics
- Higher risk of systemic absorption than oral dosing
Correct Answer: Prolonged drug residence and controlled release to cornea
Q19. Which preservative-free packaging strategy is preferred for chronic multi-dose ocular therapy?
- Single-dose units only
- Multi-dose pump bottles with anti-microbial valves
- Glass bottles without closure
- Adding extra BAK to multi-dose vials
Correct Answer: Multi-dose pump bottles with anti-microbial valves
Q20. Which ocular barrier plays a greater role in systemic absorption after topical instillation?
- Corneal stroma
- Conjunctival epithelium and conjunctival blood vessels
- Retinal pigment epithelium
- Lacrimal gland ducts
Correct Answer: Conjunctival epithelium and conjunctival blood vessels
Q21. Nanoparticle systems enhance ocular delivery mainly by:
- Increasing tear protease activity
- Providing controlled release and improved corneal contact
- Causing membrane disruption indiscriminately
- Decreasing drug stability in formulation
Correct Answer: Providing controlled release and improved corneal contact
Q22. Which in vitro test can model corneal permeability for formulation screening?
- Parallel artificial membrane permeability assay (PAMPA)
- Franz diffusion cell with excised cornea
- ELISA for tear proteins
- Mass spectrometry without membrane
Correct Answer: Franz diffusion cell with excised cornea
Q23. What is a common disadvantage of ocular ointments compared to drops?
- Lower contact time
- Cause blurred vision and reduced patient acceptance
- No capability to incorporate lipophilic drugs
- They are always non-sterile
Correct Answer: Cause blurred vision and reduced patient acceptance
Q24. Which physicochemical factor of a drug reduces corneal penetration when increased?
- Lipophilicity
- Degree of ionization (highly ionized form)
- Appropriate molecular weight under 500 Da
- Neutral charge at tear pH
Correct Answer: Degree of ionization (highly ionized form)
Q25. Which strategy can minimize systemic absorption from topical ocular drugs?
- Use of higher instilled volumes repeatedly
- Punctal occlusion after instillation
- Increasing formulation pH to extreme values
- Apply pressure to the eyelid margin away from puncta
Correct Answer: Punctal occlusion after instillation
Q26. Liposomes in ocular delivery are primarily used because they:
- Always produce immediate clearance by tears
- Improve drug solubility, protect labile drugs, and can enhance corneal retention
- Cannot encapsulate hydrophilic drugs
- Are non-biocompatible in ocular tissues
Correct Answer: Improve drug solubility, protect labile drugs, and can enhance corneal retention
Q27. Which regulatory concern is critical for sterile ocular preparations?
- Particle size of active ingredient only
- Adequate sterility assurance level and validated aseptic processing
- Color matching to marketed products
- Presence of preservatives at any concentration
Correct Answer: Adequate sterility assurance level and validated aseptic processing
Q28. Which excipient can act as a penetration enhancer for ocular delivery?
- Sodium chloride at isotonic levels only
- EDTA and some surfactants at controlled concentrations
- High concentrations of sugar alcohols exclusively
- Silicone oil in aqueous drops
Correct Answer: EDTA and some surfactants at controlled concentrations
Q29. In ocular pharmacokinetics, which term describes the fraction of applied dose reaching the target tissue?
- Residence time
- Bioavailability
- Osmolarity
- Viscosity index
Correct Answer: Bioavailability
Q30. Which animal model is frequently used for preclinical ocular toxicity and absorption studies?
- Canine only for systemic absorption
- Rabbit due to large cornea and ease of sampling
- Drosophila for corneal permeability
- Fish exclusively for human ocular predictions
Correct Answer: Rabbit due to large cornea and ease of sampling
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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