Fluorescein Strip Diagnostic Use
Fluorescein strips are used to detect corneal and conjunctival epithelial defects by staining areas where intercellular junctions are disrupted, and should be applied as saline-moistened strips to the inferior tarsal conjunctiva, then examined with a biomicroscope using cobalt blue filter after 1-2 minutes. 1
Application Technique
Proper strip preparation and application:
- Moisten the fluorescein strip with sterile saline before application 1, 2
- Apply the moistened strip to the inferior tarsal conjunctiva, avoiding direct corneal contact 2
- Avoid fluorescein-anesthetic combination drops, as anesthetics may affect test results 2
- Do not manipulate the eyelids before evaluation to prevent false-positive results 2
- Fluorescein staining should be performed before instillation of any other eyedrops 2
Examination Protocol
Visualization and timing:
- Examine the ocular surface through a biomicroscope using a cobalt blue filter 1, 2
- Wait approximately 1-2 minutes after application for optimal staining to develop 1, 2
- Use a yellow filter in conjunction with cobalt blue light for more intense visualization of staining 1, 2
- Staining is more easily visualized on the cornea than on the conjunctiva 1, 2
Clinical Interpretation
Normal versus pathologic findings:
- Mild fluorescein staining can be observed in normal eyes and may be more prominent in the morning 1, 2
- Exposure-zone punctate or blotchy fluorescein staining indicates dry eye disease 1, 2
- Diffuse corneal and conjunctival staining is commonly seen in viral keratoconjunctivitis and medicamentosa 1, 2
Location-specific patterns:
- Staining of the inferior cornea and bulbar conjunctiva typically indicates staphylococcal blepharitis, meibomian gland dysfunction, lagophthalmos, or exposure 1, 2
- Staining of the superior bulbar conjunctiva is typically seen in superior limbic keratoconjunctivitis 1
- Interpalpebral (exposure zone) corneal and bulbar conjunctival staining pattern is characteristic of dry eye disease 1, 2
Additional Diagnostic Applications
Beyond epithelial defect detection:
- Fluorescein is used for tear break-up time (TBUT) testing to assess tear film stability 2
- Recurrent tear break-up in the same area may indicate localized anterior basement-membrane abnormalities 2
- The dye stains areas where there is sufficient disruption of intercellular junctions to allow permeation into tissue 1