Researchers have been using grading systems to describe and quantify corneal staining over many years, the world over. Although an effective tool, it is important to remember that these grading systems are intended to be used in conjunction with professional judgement and experience rather than as a stand-alone clinical tool and are therefore only as reliable and effective as the practitioner is consistent.1
Commonly used grading scales document extent and severity of corneal staining and follow the global five step graded (0-4) scale:1
- Grade 0 = no staining, not clinically significant and no treatment required;
- Grade 1 = trace staining, not clinically significant and no treatment required;
- Grade 2 = mild staining, note in record and watch progression;
- Grade 3 = moderate staining, therapeutic intervention recommended;
- Grade 4 = severe staining, treatment required.
||Classification by zone
One of the more sophisticated classification systems assesses the type, depth and surface area/extent of staining in each of the corneal zones whereby staining in each zone is "counted" (i.e. 100% staining per zone).2 The surface area percentage staining range is intended as a guide rather than a fixed cut off point.
This 4-step graded process considers the corneal surface in five zones:2
Spot the difference
It is important to be aware of variations to the zonal classification method such as; 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. Some of these variations can fall short of a comprehensive evaluation so it is important to note the method being used when considering all study findings in relation to corneal staining. To this end, photographic (CCLRU) and pictorial (Efron) grading scales are being used in clinical research in an effort to minimise investigator bias.3
The categories of Grade 3 (moderate) and Grade 4 (severe) on scales like the Efron and CCLRU grading scales are recognised as clinically significant and therapeutic intervention is recommended.4
With mild to moderate staining (grade 0, 1 or 2) no action is generally required but continued monitoring is advisable. Goals of acute treatment for clinically significant staining (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.4
- Efron N. Grading Scales for contact lens complications. Appendix A. In: Contact lens Complications, Second Edition. Butterworth-Heinemann, Oxford 2004 pp. 239-243.
- Terry RL et al. CCLRU standards for success of daily and extended wear contact lenses. Optometry and Vision Science. March 1993
- Nichols K et al. Corneal Staining in Hydrogel Lens Wearers. Optometry and Vision Science, 2002; 79,1; 20-30
- 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.
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