Purpose: To describe the Oxford Scheme for grading ocular surface staining in dry eye and to discuss optimization of stain detection using various dyes and filters. Also, to propose a sequence of testing for dry eye diagnosis.
Methods: The grading of corneal and conjunctival staining is described, using the Oxford Scheme, including biomicroscopy, optical filters, illumination conditions, and the characteristics of and instillation techniques used for, selected clinical dyes.
Results: A series of panels, labeled A–E, in order of increasing severity, reproducing the staining patterns encountered in dry eye, are used as a guide to grade the degree of staining seen in the patient. The amount of staining seen in each panel, represented by punctate dots, increases by 0.5 of the log of the number of dots between panels B to E. The use of the vital dyes fluorescein, lissamine green, and rose Bengal is described; fluorescein and lissamine green, used in conjunction with appropriate absorption filters, are recommended for use in clinical trials. The placement of staining in relation to the sequence of other diagnostic tests is discussed.
Conclusions: The monitoring and assessment of corneal and conjunctival staining can be greatly enhanced by the use of a grading scale, controlled instillation of dyes, and standard evaluation techniques. This is of particular benefit in clinical trials, where ocular surface staining is commonly employed as an outcome measure
Grading staining of the ocular surface after instillation of vital dyes is a critical component of dry eye diagnosis. Pflüger was the first to describe vital staining of the cornea and conjunctiva in 1882, 1 and Fromm and Groenouw (cited by Joyce) reported the use of fluorescein to stain damaged corneal epithelium in 1891. 2 Staining of the ocular surface with various dyes is used to characterize disease, assess its severity, and monitor the clinical response to therapy. It is also used as an outcome measure in clinical trials. For any of these purposes, but particularly for clinical trials, it is essential to standardize the procedures used. This paper describes a standardized approach to the grading of ocular surface dye staining in dry eye, using the Oxford grading system. 3,4 Much of the paper deals with the details of dye selection and instillation. The approaches proposed are equally relevant to other grading systems. 5–7
Because of the invasive nature of some of the tests performed in the diagnosis of dry eye, it is important to perform them in a sequence that minimizes their interaction and limits the extent to which one test influences the outcome of the tests that follow. The sequence described here assumes that most or all tests are performed at the same visit for reasons of convenience and, in the clinical trial setting, to achieve compliance. However, instances may arise when, for operational reasons, tests would be conducted at separate clinic visits.