What causes abnormal corneal uptake of fluorescein (fluorescein dye)?

From the Guidelines

Abnormal corneal uptake of fluorescein is primarily caused by disruptions to the corneal epithelium, which normally forms a tight barrier preventing fluorescein penetration, as noted in the most recent study 1. The most common causes include epithelial defects such as corneal abrasions, ulcers, and erosions, where damaged or missing epithelial cells allow fluorescein to penetrate and bind to underlying stroma, creating visible staining. Some key points to consider are:

• Dry eye disease causes punctate epithelial erosions that appear as multiple tiny dots of fluorescein uptake, as seen in studies 1 and 1.
• Contact lens wear can lead to mechanical trauma, hypoxia, or solution toxicity that damages the epithelium.
• Infectious keratitis from bacteria, viruses, fungi, or parasites creates epithelial defects that stain with fluorescein, as discussed in 1 and 1.
• Chemical or thermal injuries disrupt epithelial integrity, while systemic conditions like vitamin A deficiency and certain autoimmune diseases can affect epithelial health.
• Surgical procedures like LASIK or PRK temporarily disrupt the epithelium, causing fluorescein uptake until healing occurs. The intensity and pattern of staining provide valuable diagnostic information about the nature and severity of corneal pathology, as highlighted in the study 1.

From the Research

Abnormal Corneal Uptake of Fluorescein

The abnormal corneal uptake of fluorescein can be caused by several factors, including:

• Disruptions of the epithelial barrier function, which can lead to the entry of fluorescein into the corneal epithelium 2
• The presence of monocarboxylate transporters (MCTs) in the corneal epithelium, which can mediate the transport of fluorescein across the epithelial cells 3
• A graded loss of the glycocalyx barrier, permitting transcellular entry of fluorescein into pre-shed cells 4
• Defective tight junctions, which can allow fluorescein to diffuse across the epithelial cells 4
• Solution-Induced Corneal Staining (SICS), which can involve the non-pathological uptake of cationic preservatives into epithelial membranes and secondary binding of the fluorescein anion 4

Conditions Associated with Abnormal Corneal Uptake of Fluorescein

Abnormal corneal uptake of fluorescein has been observed in several conditions, including:

• Keratoconjunctivitis sicca (KCS) 2
• Dry eye syndrome 5, 6
• Neurotrophic keratitis 6
• Corneal ulcers 5, 6
• Inflammatory diseases of the ocular surface 6