Eyecare clinicians and scientists have come a long way in diagnosing and understanding ocular surface disease (OSD). Sophisticated technologies to guide restoration of the environmental balance of the ocular surface abound, with ever-greater expectations for subjective and objective clinical success.

However, what if you could have only one thing in your office—besides your slit lamp—to make an early diagnosis of OSD and monitor treatments for it? My wish would be for a box of sodium fluorescein (NaFl) strips to examine critically the conjunctiva and cornea with this versatile vital dye.

In the mid-1980s, it was noted that the conjunctiva will exhibit changes before the cornea in dry eye disease (Gilbrand, 1985). One study noted that conjunctival staining with fluorescein sodium seems to be more sensitive for the detection of conjunctival damage than lissamine green (Cox and Nichols, 2015).

Another study indicated that fluorescein staining in conjunction with a yellow filter has the advantage of simultaneous observation of both corneal and conjunctival damage in patients who have dry eye without the need for additional vital staining (Eom et al, 2015). That said, lissamine green in solution is a superb dye for assessing conjunctival staining.

NaFl staining, and its clinical interpretation, takes a bit of practice and finesse. There are temporal characteristics of NaFl applied in the tear meniscus. The fluorescence intensity of fluorescein in a clinical setting varies with time such that both the onset and duration of maximum brightness are dependent on the concentration (Markoulli et al, 2017).

Fluorescein dye can undergo a phenomenon known as concentration quenching; fluorescence intensity increases with concentration up to a maximum point, after which the fluorescence intensity decreases (Nichols et al, 2012). Thus, both high and very low concentrations of fluorescein dye can appear very dark or black, creating confusion for the observer.

Each practitioner will develop his or her own specific consistency in NaFl testing and timing, creating a personal results gauge of sorts. Note, however, that there are numerous grading scales available for vital dye staining of the conjunctiva and cornea that record metrics such as dye intensity and area of positive surface staining (Begley et al, 2019).

NaFl has added value in that it can highlight corneal dystrophies (for example, corneal valence, which is a scalloped line of tear film thinning that is readily evident with fluorescein and the cobalt blue filter at the slit lamp) (Shahinian, 1984; Mansoor et al, 2020).

NaFl can also assist in gauging the tear flow of the nasolacrimal system. For instance, the Fluorescein Dye Disappearance Test is a noninvasive, relatively objective, and quantitative test for identifying disorders of the lacrimal drainage system (American Academy of Ophthalmology, 2022). Fluorescein profilometry allows clinicians to follow dynamic changes in the tear film on the entire ocular surface by observing the fluorescein decay rate over time (Garaszczuk and Iskander, 2017). Additionally, it is used for a qualitative assessment of the tear film dynamics (Garaszczuk and Iskander, 2017).

I delight in the array of gizmos and gadgets available to elevate our practices, patient engagement education, and treatment compliance—as long as the pocket of my practitioner’s coat is full of NaFl strips. CLS

References

1. Gilbard JP. Tear film osmolarity and keratoconjunctivitis sicca. CLAO J. 1985 Jul-Sep;11:243-250.
2. Cox SM, Nichols JJ. Association Between Meibomian Gland Testing and Ocular Surface Sensitivity. Cornea. 2015 Oct;34:1187-1192.
3. Eom Y, Lee JS, Keun Lee H, Myung Kim H, Suk Song J. Comparison of conjunctival staining between lissamine green and yellow filtered fluorescein sodium. Can J Ophthalmol. 2015 Aug;50:273-277.
4. Markoulli M, Isa NA, Papas EB. Temporal Characteristics of Sodium Fluorescein in the Tear Meniscus. Optom Vis Sci. 2017 Feb;94:166-173.
5. Nichols JJ, King-Smith PE, Hinei EA, Thangavelu M, Nichols KK. The use of fluorescent quenching in studying the contribution of evaporation to tear thinning. Invest Ophthalmol Vis Sci. 2012 Aug 20;53:5426-5432.
6. Begley C, Caffery B, Chalmers R, Situ P, Simpson T, Nelson JD. Review and analysis of grading scales for ocular surface staining. Ocul Surf. 2019 Apr;17:208-220.
7. Shahinian L Jr. Corneal valance: a tear film pattern in map-dot-fingerprint corneal dystrophy. Ann Ophthalmol. 1984 Jun;16:567:570-571.
8. Mansoor H, Tan HC, Lin MT, Mehta JS, Liu YC. Diabetic Corneal Neuropathy. J Clin Med. 2020 Dec 6;9:3956.
9. American Academy of Ophthalmology. Fluorescein dye disappearance. Available at aao.org/image/fluorescein-dye-disappearance . Accessed June 2, 2022.
10. Garaszczuk IK, Iskander DR. Qualitative assessment of tear dynamics with fluorescein profilometry. Cont Lens Anterior Eye. 2017 Aug;40:208-212.