FREQUENTLY ASKED QUESTIONS
  1. What is corneal staining?
  2. When is corneal staining considered normal?
  3. How prevalent is corneal staining?
  4. Is corneal staining more common in contact lens wearers?
  5. What are the causes of corneal staining?
  6. What are the symptoms of corneal staining?
  7. Is corneal staining evaluated during a routine examination?
  8. How do you evaluate clinically significant corneal staining?
  9. There are so many different grading scales - which one should I use?
  10. What grade of corneal staining severity is considered clinically significant?
  11. What are the implications of moderate or severe clinically significant staining?
  12. Can corneal staining lead to infectious keratitis?
  13. What are the recommendations for the clinical management of corneal staining?
  14. Why has corneal staining become a hot topic for industry discussion?
  15. What variations of the traditional classification methods fall short of a comprehensive evaluation?
  16. Why has the Andrasko grid caused such industry controversy?
  17. Why has the methodology behind the Andrasko grid been criticised?
  18. Does Andrasko's grid establish a link between transient corneal staining and the risk of infection?
  19. What is a limitation of the Andrasko study grids 'percentage area' measurements?
  20. Why is it important to validate the scoring method?
  21. What is the impact of discounting type, pattern and distribution?
  22. Why is two hours of contact lens wear not predictive of long-term success?
  23. Why is it important to perform a statistical analysis?
  24. What are the advantages of biocompatibility-based tests over corneal staining?
  25. What are considered biocompatibility-based tests?
  26. Is cytotoxicity another measure for corneal staining?
  27. Do all contact lens solutions undergo cytotoxicity testing before they are marketed?

  1. What is corneal staining?
  2. Corneal staining is an important component of the routine contact lens examination. Sodium fluorescein dye applied to the ocular surface is used to stain devitalised corneal cells and highlight damage or disease.1,2
  3. When is corneal staining considered normal?
  4. Corneal staining occurs as a consequence of a natural process and so, to some degree, occurs in everyone from time to time due to continuous physiological regeneration of the corneal cell membrane.3
  5. How prevalent is corneal staining?
  6. Studies have estimated this to be 4% to 79% of the general, non contact lens wearing population and up to 56% of the contact lens wearing population.4,5,6,7,8,9
  7. Is corneal staining more common in contact lens wearers?
  8. Corneal staining is a common observation in contact lens wearers, although often low level and clinically insignificant.1
  9. What are the causes of corneal staining?
  10. Corneal staining can result as one of six causes: mechanical, exposure, metabolic, toxic, allergic and infectious.3
  11. What are the symptoms of corneal staining
  12. Corneal staining is generally asymptomatic.10
  13. Is corneal staining evaluated during a routine examination?
  14. As corneal staining is rarely manifested through symptoms, routine evaluation is important. Routine evaluation also helps practitioners familiarise themselves with the incidence of low level staining and become familiar with what is normal and abnormal staining.3,11
  15. How do you evaluate clinically significant corneal staining?
  16. Grading schemes, scales and standards have been helping practitioners for many years determine acceptable levels of corneal staining and definitions of clinical significance.11 Such grading scales are intended to be used in conjunction with professional judgement and experience rather than as a stand-alone clinical tool.12
  17. There are so many different grading scales - which one should I use?
  18. Commonly used grading scales document extent and severity of corneal staining and follow the global five step graded (0-4) scale. The grading scale developed by Efron is globally recognised and has been used over many years.12 The corneal surface can be further evaluated (as developed by CCLRU) by considering type, depth and surface area/extent of staining in five zones:12
    • Central
    • Superior
    • Inferior
    • Nasal
    • Temporal
  19. What grade of corneal staining severity is considered clinically significant?
  20. According to traditional grading scales, such as those developed by Efron and CCLRU, Grade 3 (moderate) and Grade 4 (severe) are recognised as clinically significant and therapeutic intervention is recommended.12,13
  21. What are the implications of moderate or severe clinically significant staining?
  22. Moderate and severe levels of clinically significant corneal staining are generally asymptomatic and reversible with correct clinical management and patient compliance.3
  23. Can corneal staining lead to infectious keratitis?
  24. There is no evidence to show a link between solution-related transient micropunctate corneal staining and infectious keratitis and various researchers have spoken out against these theories:
    • “no evidence has yet appeared to establish any such association (with microbial keratitis) for any type of staining, whether solution related or not.”3
    • Professor Holden stated “…we are disturbed that some have drawn conclusions between solution induced corneal staining and microbial keratitis.”13
  25. What are the recommendations for the clinical management of corneal staining?
  26. With mild to moderate severity staining (grade 0, 1 or 2) no action is generally required but continued monitoring is advisable. Goals of acute treatment for clinically significant staining severity (grade 3 or 4) focus on decreasing any subjective patient discomfort and the risk of abrasion and/or secondary infection. It is important that practitioners follow their professional judgement and determine their comfort level in the clinical management and treatment of corneal staining.3
  27. Why has corneal staining become a hot topic for industry discussion?
  28. A number of variations and adaptations to traditional zonal classification methods fall short of a comprehensive evaluation and have given rise to an industry wide discussion on corneal staining evaluation methods.1
  29. What variations of the traditional classification methods fall short of a comprehensive evaluation?
  30. Examples include; the computer assisted analysis developed by Pritchard & Young as well as Begley, Jones' zonal staining score, Nichols' cumulative corneal 0-4 grading and Andrasko's average of the 5 zone staining area.1
  31. Why has the Andrasko grid caused such industry controversy?
  32. The colour-coded corneal staining grid developed by optometrists, Dr. Gary Andrasko, and Dr. Kelly Ryen with support from Alcon has borne much industry discussion and debate; specifically around the importance and clinical relevance of statistically significant differences in graded staining.14
  33. Why has the methodology behind the Andrasko grid been criticised?
  34. The methodology behind the Andrasko grid has been met with the following criticisms;
    • There is no statistical analysis of the data14
    • Type, pattern and distribution are discounted as measures15
    • The only measure is area which is estimated and not measured15
    • The scoring method is a variation of other grading scales and it is not scientifically validated2
    • The time measure of two-hours is not predictive of long term success14
    • Staining “codes” are arbitrary - not based on science or on validated clinical measures1,2
  35. Does Andrasko’s grid establish a link between transient corneal staining and the risk of infection?
  36. Findings presented in Andrasko’s grid demonstrates superficial, transient corneal staining; however no link has been established to show that corneal staining is a risk factor for lens related corneal infection.16
  37. What is a limitation of the Andrasko study grids ‘percentage area’ measurements?
  38. The percentage area of staining was approximated and no precise measurements have been taken.14
  39. Why is it important to validate the scoring method?
  40. Scientific validation of a scoring method ensures a robust clinical trial methodology and fundamental to confirming a clinical outcome.13
  41. What is the impact of discounting type, pattern and distribution?
  42. Discounting the type, pattern and distribution measures of corneal staining may result in a score which indicates a higher or lower risk for infection than is really the case.15
  43. Why is two hours of contact lens wear not predictive of long-term success?
  44. Evidence suggests that 3 months is a more reliable time scale to assess corneal staining due to contact lens wearing.13
  45. Why is it important to perform a statistical analysis?
  46. To validate clinical findings and ensure anomalies and exceptional results do not alter the conclusions.13
  47. What are the advantages of biocompatibility-based tests over corneal staining?
  48. Biocompatibility-based testing provides a deeper level evaluation than corneal staining.
  49. What are considered biocompatibility-based tests?
  50. Biocompatibility-based tests include:
    1. AlmarBlue - a metabolic dye that measures the respiratory activity of cells17
    2. Sodium-fluorescein permeability assay - higher sodium-fluorescein permeability is related to breaks/disruption in the tight junctions between cells, suggesting damaged or compromised cells18
    3. Confocal microscopy - looks at deeper levels of the corneal epithelium that are not visible through a slit lamp or even a scanning electron microscope.19
  51. Is cytotoxicity another measure for corneal staining?
  52. Cytotoxicity is not a method of evaluating eye health but instead a pre-clinical evaluation of solution toxicity. Cytotoxicity assays conducted in vitro or in animals assess the effect of different compounds on cells from different tissues (biocompatibility) of contact lens solutions before moving to human clinical testing to determine if a cytotoxic component exists.15
  53. Do all contact lens solutions undergo cytotoxicity testing before they are marketed?
  54. All products are required to undergo in vitro cytotoxicity testing as part of the regulatory guidance from governing authorities such as the European Medicines Agency and other global standards organisations.20
References
  1. Nichols K. et al. Corneal Staining in Hydrogel Lens Wearers. Optometry and Vision Science, 2002; 79,1; 20-30
  2. Ward K. Superficial Punctate Fluorescein Staining of the Ocular Surface. Optometry and Vision Science; 2008; 85:1, 8-16
  3. Snyder C. Solution Interaction with the Ocular Surface: The Significance in Making the Grade. Clinical & Refractive Optometry, 2005; 16:5, 134-140. Copyright Mediconcept 2005.
  4. Norn MS. Micropunctate fluorescein vital staining of the cornea. Acta Ophthalmol 1970;48: 108–18.
  5. Schwallie JD, McKenney CD, Long WD, McNeil A. Corneal staining patterns in normal non-contact lens wearers. Optom Vis Sci 1997;74:92–8.
  6. Korb DR, Korb JM. Corneal staining prior to contact lens wearing. J Am Optom Assoc 1970;41: 228–32.
  7. Caffery BE, Josephson JE. Corneal staining after sequential instillations of fluorescein over 30 days. Optom Vis Sci 1991;68: 467–9.
  8. Josephson JE, Caffery BE. Corneal staining characteristics after sequential instillations of fluorescein. Optom Vis Sci 1992;69: 570–3.
  9. Dundas M, Walker A, Woods RL. Clinical grading of corneal staining of non-contact lens wearers. Ophthalmic Physiol Opt 2001;21: 30–5.
  10. Carnt NT et al. Corneal Staining: The IER Matrix Study. Contact Lens Spectrum, September 2007
  11. Efron N. Grading Scales for contact lens complications. Appendix A. In: Contact lens Complications, Second Edition. Butterworth-Heinemann, Oxford 2004 pp. 239-243.
  12. Terry RL et al. CCLRU standards for success of daily and extended wear contact lenses. Optom Vis Sci. March 1993
  13. IER Matrix Study establishes ‘real world’ silicon hydrogel solution guide. IER Press Release on Carnt NT et al. Corneal Staining: The IER Matrix Study. Contact Lens Spectrum, September 2007
  14. Dillehay SM & Cutter G. A Statistical Analysis of the Staining Grid. Contact Lens Spectrum, November 2007
  15. www.staininggrid.com. Accessed January 2008
  16. Levy B & Orsborn G. Clinical Risks: Myths and Truths. Interpreting the evidence-based data about contact lens care. Contact Lens Spectrum, January 2008.
  17. McCanna D et al. Use of a human corneal epithelial cell line for screening the safety of contact lens care solutions in vitro. Eye & Contact Lens, 2008; 34;1: 6-12
  18. Tchao R et al. Comparison of contact lens multipurpose solutions by in vitro sodium fluorescein permeability assay. The CLAO Journal, 2002; 28:3:151-156
  19. Bantseev V, McCanna D, Driot J-Y, Ward K, Sivak, J: Biocompatibility of Contact Lens Solutions Using Confocal Laser Scanning Microscopy and the In Vitro Bovine Cornea. Eye and Contact Lens, 33 (6, Part 1 of 2):308-316
  20. Mowrey-McKee M et al. Comparative cytotoxicity potential of soft contact lens care regimens, The CLAO Journal, 2002; 28(3): 160-164
www.truthaboutstaininggrid.com is intended as a scientific resource for eye care practitioners developed by Bausch & Lomb