Screening models for drugs acting on the eye are essential tools in ocular pharmacology and drug delivery research for B. Pharm students. These models—ranging from in vitro cell cultures and ex vivo corneal/scleral tissues to in vivo animal studies—help evaluate permeability, irritation, toxicity, and pharmacokinetics of ophthalmic candidates. Key concepts include corneal permeability, tear film dynamics, Franz diffusion cell assays, organotypic cultures, ocular cell lines (e.g., HCE-T), and alternatives to the Draize test like BCOP and HET-CAM. Understanding advantages, limitations, endpoints, and regulatory expectations informs formulation optimization and IVIVC for ocular bioavailability. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which in vitro setup is commonly used to measure transcorneal drug permeability across excised corneal tissue?
- Franz diffusion cell
- Patch clamp apparatus
- Flow cytometer
- ELISA plate reader
Correct Answer: Franz diffusion cell
Q2. Which ocular cell line is widely used as a human corneal epithelial model for permeability and toxicity screening?
- HepG2
- HCE-T
- CHO
- HEK293
Correct Answer: HCE-T
Q3. Which assay measures cell viability by reduction of a tetrazolium salt to formazan and is used in ocular cytotoxicity screening?
- MTT assay
- Bradford assay
- Comet assay
- BCA assay
Correct Answer: MTT assay
Q4. The Draize eye irritation test is best described as:
- An in vitro corneal permeability assay
- An in vivo rabbit ocular irritation test
- A computer simulation for ocular PK
- An ex vivo scleral transport method
Correct Answer: An in vivo rabbit ocular irritation test
Q5. Which alternative test to the Draize assay uses isolated bovine corneas to assess ocular corrosivity?
- BCOP (Bovine Corneal Opacity and Permeability) assay
- HET-CAM assay
- Chorioallantoic membrane angiogenesis test
- Ussing chamber test
Correct Answer: BCOP (Bovine Corneal Opacity and Permeability) assay
Q6. In transcorneal permeability, which drug property most strongly favors passage through the corneal epithelium?
- High molecular weight
- High lipophilicity (moderate)
- Extreme hydrophilicity
- High degree of ionization at tear pH
Correct Answer: High lipophilicity (moderate)
Q7. Which parameter calculated from Franz cell experiments indicates drug permeation rate through corneal tissue?
- Partition coefficient (log P)
- Flux (J) or steady-state flux
- Minimal inhibitory concentration
- Zeta potential
Correct Answer: Flux (J) or steady-state flux
Q8. HET-CAM assay is performed on which biological structure to assess irritation potential?
- Hen’s egg chorioallantoic membrane
- Human corneal epithelial culture
- Bovine cornea
- Rabbit conjunctiva
Correct Answer: Hen’s egg chorioallantoic membrane
Q9. Which in vitro model better preserves tissue architecture and allows short-term study of ocular drug distribution using whole-eye segments?
- Monolayer cell culture
- Organotypic/ex vivo eye cup or corneal culture
- Suspension cell assay
- 2D transwell only with single cell type
Correct Answer: Organotypic/ex vivo eye cup or corneal culture
Q10. For predicting human ocular irritation with fewer animals, which organization encourages use of alternative in vitro tests?
- FDA only
- OECD (Organization for Economic Co-operation and Development)
- ISO exclusively
- Local university guidelines only
Correct Answer: OECD (Organization for Economic Co-operation and Development)
Q11. Which model measures epithelial barrier integrity by recording transepithelial electrical resistance (TEER)?
- Franz diffusion cell
- TEER measurement across cell monolayers
- Gel diffusion test
- Flow cytometry
Correct Answer: TEER measurement across cell monolayers
Q12. The Ussing chamber is primarily used to study which ocular parameter in excised tissues?
- Electrical properties and ion transport across epithelia
- Corneal thickness by OCT
- In vivo tear production
- Micron-sized particle size distribution
Correct Answer: Electrical properties and ion transport across epithelia
Q13. When developing in vitro–in vivo correlation (IVIVC) for ocular delivery, which factor is critical to replicate?
- Tear turnover and nasolacrimal drainage
- Blood pressure variations
- Gastric pH
- Hepatic metabolism only
Correct Answer: Tear turnover and nasolacrimal drainage
Q14. Which compound is commonly used to simulate tear fluid in in vitro ocular experiments?
- Simulated Tear Fluid (STF) containing salts and bicarbonate
- Normal saline with no electrolytes
- Pure water
- Phosphate-buffered saline without ions
Correct Answer: Simulated Tear Fluid (STF) containing salts and bicarbonate
Q15. In ocular drug screening, what is a major limitation of monolayer cell cultures compared with organotypic models?
- They are too expensive
- They lack full 3D tissue architecture and multiple cell types
- They always overpredict human toxicity
- They cannot be maintained for short-term studies
Correct Answer: They lack full 3D tissue architecture and multiple cell types
Q16. Which analytical technique is most commonly used to quantify drug concentrations in receiver fluid from permeability studies?
- HPLC (High-performance liquid chromatography)
- Light microscopy
- Gel electrophoresis
- Atomic force microscopy
Correct Answer: HPLC (High-performance liquid chromatography)
Q17. Which screening approach is preferred for assessing nanoparticle mucoadhesion and retention on ocular surface models?
- In vitro mucin binding and rheology studies with mucin-coated substrates
- Standard bacterial culture
- Systemic PK in rats without ocular dosing
- Gel electrophoresis of nanoparticles
Correct Answer: In vitro mucin binding and rheology studies with mucin-coated substrates
Q18. Which property of a drug reduces its transcorneal permeation through the stroma?
- High lipophilicity
- Polarity and high hydrophilicity
- Low molecular weight
- Unionized fraction at tear pH
Correct Answer: Polarity and high hydrophilicity
Q19. Which test evaluates ocular surface toxicity by measuring protein denaturation and membrane damage on the CAM model?
- BCOP assay
- HET-CAM assay
- MTT assay only
- Franz diffusion directly
Correct Answer: HET-CAM assay
Q20. When screening ocular prodrugs, which in vitro measure helps predict corneal esterase-mediated activation?
- Permeability across artificial membranes only
- Enzymatic conversion rate in corneal homogenates or cell lysates
- Colorimetric pH test
- Zeta potential of formulation
Correct Answer: Enzymatic conversion rate in corneal homogenates or cell lysates
Q21. Which experimental factor must be controlled when using excised cornea in Franz cell to avoid artifactual permeability measurements?
- Tissue thickness and viability, temperature, and donor age
- Ambient light color only
- Color of the donor animal fur
- Magnetic field around the lab
Correct Answer: Tissue thickness and viability, temperature, and donor age
Q22. Which in vitro method is suitable to study drug–tear film interactions and protein binding on the ocular surface?
- Tear protein binding assays and mucin interaction studies
- Western blot of hepatic proteins
- Blood coagulation tests
- Urine dipstick tests
Correct Answer: Tear protein binding assays and mucin interaction studies
Q23. In ocular screening, what is a primary reason for using ex vivo sclera rather than cornea for certain drugs?
- Sclera is more lipid-rich than cornea
- Sclera favors hydrophilic macromolecular or transscleral delivery to posterior segment
- Sclera has higher enzymatic activity for prodrug activation
- Sclera is transparent and used for optical studies
Correct Answer: Sclera favors hydrophilic macromolecular or transscleral delivery to posterior segment
Q24. Which endpoint in screening models indicates disruption of corneal epithelial tight junctions?
- Increase in TEER and decreased permeability
- Decrease in TEER and increased paracellular permeability
- Increased colony formation
- Higher mitochondrial respiration only
Correct Answer: Decrease in TEER and increased paracellular permeability
Q25. When evaluating ocular formulations, why is sterility testing crucial in screening models?
- Because microbial contamination can cause infection and confound toxicity/permeability data
- Because sterility increases drug lipophilicity
- Because sterility is irrelevant for in vitro tests
- Because sterility changes drug pKa
Correct Answer: Because microbial contamination can cause infection and confound toxicity/permeability data
Q26. Which technique can visualize drug distribution across ocular tissues in ex vivo sections without radiolabeling?
- Autoradiography only
- Mass spectrometry imaging (MSI) such as MALDI-MSI
- Standard light microscopy without staining
- ELISA of whole eye homogenate only
Correct Answer: Mass spectrometry imaging (MSI) such as MALDI-MSI
Q27. Which factor most directly affects corneal penetration of weakly basic drugs in the tear film environment?
- Drug’s pKa and percent unionized at tear pH
- Drug’s boiling point
- Ambient humidity only
- Color of formulation
Correct Answer: Drug’s pKa and percent unionized at tear pH
Q28. For high-throughput ocular screening of cytotoxicity, which format is commonly used?
- 96-well plate assays using ocular cell lines combined with viability dyes
- Single large Franz cell per compound
- Full animal studies for each compound
- In vivo human trials
Correct Answer: 96-well plate assays using ocular cell lines combined with viability dyes
Q29. Which statement about in vivo ocular models is true for B. Pharm students to consider?
- Animal models always exactly predict human ocular responses
- They provide integrated pharmacokinetics and pharmacodynamics but have species differences that limit direct extrapolation
- They are cheaper and faster than all in vitro models
- They eliminate the need for analytical quantification
Correct Answer: They provide integrated pharmacokinetics and pharmacodynamics but have species differences that limit direct extrapolation
Q30. Which screening strategy best supports early selection of promising ocular formulations before animal tests?
- Combine in vitro corneal cell assays (viability, TEER), ex vivo permeability (Franz cell), and irritation alternatives (BCOP/HET-CAM)
- Proceed directly to human volunteers
- Rely solely on computational predictions without experiments
- Use only systemic toxicity assays in liver cells
Correct Answer: Combine in vitro corneal cell assays (viability, TEER), ex vivo permeability (Franz cell), and irritation alternatives (BCOP/HET-CAM)
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.
Mail- Sachin@pharmacyfreak.com