The concept of vital staining using fluorescein dates all the way back to 1886.1 For over a century, this organic compound has been utilized in ophthalmology and optometry for a variety of diagnostic procedures, including contact lens assessment, retinal angiography, and applanation tonometry.
In the realm of the ocular surface, fluorescein proves invaluable in identifying corneal perforations, corneal abrasions, and keratitis.1,2 It also plays a crucial role in determining the presence and severity of dry eye disease (DED).
Dr. Nichols, who has been utilizing pattern recognition with fluorescein for decades to identify dry eye disease, spot masqueraders, and help guide therapy, explained that fluorescein serves two purposes. First, it integrates itself into the tear film and provides a way to view the tears and assess breakup time.
Then, as it starts to dissipate, it highlights any defects of the corneal epithelium by filling in the gaps of missing cells, allowing the clinician to grade the ocular surface damage. Therefore, it is an indispensable tool in the optometrist’s arsenal.
Embracing fluorescein as part of the comprehensive exam
Both optometrists agree that fluorescein staining should be integrated into comprehensive examinations. According to Dr. Nichols, “I'm a purist, so I'd like to say that it should be involved in a routine eye exam, so you can decide whether or not there's a trigger for the patient to come back for an ocular surface exam. I would always recommend using fluorescein strips in all scenarios.”
For those concerned with its interference in taking eye pressure, she emphasized that pressure can be taken prior, by an alternative method, or post-staining using an anesthetic drop.
Back to basics: Step-by-step guide to instilling fluorescein
- Check the expiration date of the fluorescein strip.
- Open the strip, making sure not to touch the orange portion.
- Wet the orange portion of the strip with sterile saline without touching the tip of the bottle to the strip.
- Have the patient look up to the ceiling to ensure the cornea is as far from the bottom lid as possible.
- Gently move the lower eyelid down.
- Place the orange portion of the strip on the bulbar conjunctiva allowing the strip to release the fluorescein dye.
- Instruct the patient to blink several times to spread the dye evenly throughout the eye.
Pro tips for fluorescein instillation and assessment
Dr. Nichols stresses the importance of avoiding fluorescein drops with numbing medications and always opting for strips moistened with saline only, as fluorescein with an added analgesic makes it impossible to see patterns and accurately analyze the corneal and conjunctival health.
She also advises to make certain to get enough fluorescein in the eye, so it can work its “magic.” In addition, do not neglect to look at the conjunctiva. Addressing the debate on placement, Dr. Nichols weighed in, saying both superior and inferior are acceptable.
Once the fluorescein has been properly instilled, head to the slip lamp and use a Wratten filter in conjunction with the cobalt blue filter. With this yellow filter, the green color becomes more iridescent allowing you to see fine punctate staining as well as staining on the conjunctiva.
Note: Wratten filters can be acquired from any rigid contact lens distributor, so ask your company rep, and they will bring one to your office or will sell it at a modest price. They are also frequently available at conferences and meetings. Or, they can be purchased on Amazon or photography equipment websites.
Dry eye disease assessment
To assess patients for DED, Dr. Nichols recommends:
- Providing a survey and/or asking DED-focused questions
- Conducting a slit lamp exam with white light
- Performing fluorescein tear film breakup time
- Conducting corneal staining using a Wratten filter
- Assessing and expressing the meibomian glands
Utilizing pattern recognition in DED management
Fluorescein staining patterns can reveal keratoconjunctivitis sicca (KCS), Sjögren's syndrome, the range of keratitis (from infectious to neurotrophic keratitis [NK]), the severity of DED, and much more.
In most instances, upon viewing the ocular surface under staining, doctors assign a grade from 1 to 4, with 4 being the most severe. If they choose to go a step further, optometrists can grade the defects in each region of the cornea, isolating the superior, inferior, nasal, central, and temporal areas.
What fluorescein staining patterns are associated with dry eye disease?
Dr. Nichols states that you should expect to see the most staining inferiorly; this is due to exposure and proximity to the meibomian glands. Nasal and temporal staining are the next most common, followed by central. Do not forget to examine the superior cornea, which can often offer hints towards other masquerading eye conditions.
Lateral and central staining may drive a diagnostic code of punctate keratitis. Significant staining could point to Sjögren's syndrome. Any central corneal staining is an indication that there is an inflammatory reaction going on in the cornea that should be addressed.
With allergic conjunctivitis or bacterial conjunctivitis, expect to see a more diffuse staining pattern. If you see inferior corneal staining, the Korb-Blackie lid leak test can determine whether an insufficient lid seal is a component.
Taking contacts into consideration
In patients who regularly wear contact lenses, the cornea is somewhat protected by the lens. Therefore, staining patterns tend to be more nasal and temporal.
The importance of corneal sensitivity testing
Dr. Nichols underscores that in patients with extensive staining who do not report any associated symptoms, corneal sensitivity testing should be performed to deduce whether NK may be the culprit. This is especially important in individuals with diabetes and/or a history of herpes, stromal, or epithelial keratitis.
The future of fluorescein
As for her hopes for technological advances, Dr. Nichols stated, “I ultimately can imagine that a patient could have a scan of their cornea that would tell the clinician what grade of staining or damage there was on the ocular surface. That would be fantastic.”
However, until an imaging platform is capable of capturing individual cell loss, fluorescein will remain a vital element in assessing dry eye disease.
