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Oliver Findl 1,2 , Nino Hirnschall 1,2 , Alja Crnej 2 1 VIROS Vienna Institute for Research in Ocular Surgery, Hanu - PowerPoint PPT Presentation


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Effect of Fluorescein dye staining of the tear film on Scheimpflug measurements of central corneal thickness. Oliver Findl 1,2 , Nino Hirnschall 1,2 , Alja Crnej 2 1 VIROS Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria

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Presentation Transcript
slide1

Effect of Fluorescein dye staining of the tear film on Scheimpflug measurements of central corneal thickness

Oliver Findl 1,2, Nino Hirnschall 1,2, Alja Crnej 2

1 VIROS Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria

2 Moorfields Eye Hospital, London, UK

Financial interest: none

OF is scientific advisor to Alcon, AMO, Croma & Carl Zeiss Meditec AG

background
Background
  • Fluorescein dye is commonly used in routine ophthalmic examination
    • staining epithelial defects of the cornea
    • break up time of the tear film
    • Goldmann applanation tonometry
  • Correct CCT measurement needed for:
    • corneal refractive surgery
    • diagnosis of corneal diseases (keratoconus)
    • to correct for systematic errors of IOP measurements using Goldmann applanation.
cct measurement devices
CCT measurement devices
  • Pentacam: rotating Scheimpflug photographic
    • measures the thickness from the image, which is created from the back-scattered light from the corneal tissue

=> Influenced by fluorescein eye drops?

  • ACMaster: partial coherence interferometry (PCI)
    • gold standard for CCT measurement
    • measures distances between surface interfaces with a different refractive index
methods
Methods
  • Prospective randomised controlled study
  • 30 eyes of 15 patients (8 female, 7 male)
methods1
Methods

3 x rotating Scheimpflug imaging + 3 x PCI measurement

Instilling 0.25% fluorescein +

0.5% proxymetacaine hydrochloride

Rotating Scheimpflug imaging + PCI measurement

Irrigation with 2ml BSS

Rotating Scheimpflug imaging + PCI

after 5min, 10min, 20min, 40min, 60min, (120min)

Rotating Scheimpflug imaging + PCI

slide6

With Fluorescein

Without Fluorescein

results
Results

Rotating Scheimpflug: 46.6µm difference

PCI: 1.6µm difference

results1
Results

CCT difference (PCI) in µm

CCT difference (Scheimpflug) in µm

results2
Results

Number of patients (%) with a fluorescein layer +5µm compared to baseline

Subjects with Fluorescein layer (%)

time after applying Fluorescein (min)

Fluorescein layer -> more than 5µm difference to the baseline measurement

results3
Results

Schirmer 2 results (sec)

time after applying Fluorescein (min)

conclusion
Conclusion
  • Scheimpflug imaging
    • Fluorescein dye causes intense back-scatter of light resulting in a measurement error
    • Irrigating the eye reduces this effect only insignificantly
  • PCI: is not influenced by altered or higher reflectivity
  • => Fluorescein eye drops MUST NOT be used prior to Scheimpflug imaging measurements