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Abstract

Purpose
This study investigates the effect of fluorescein sodium (NaFl) volume on the regularity of the anterior eye surface using the Medmont corneal topographer measurements.

Method
The simulated keratometry values (flat = Kf; steep = Ks), Inferior Superior Index (ISI), Surface Asymmetry Index (SAI), and Surface Regularity Index (SRI) measurements, using the E300 corneal topographer (Medmont International Pty Ltd., Victoria, Australia), were taken three times under three different conditions: baseline (without NaFl), including a single dose NaFl, and a double dose NaFl. Of the 57 participants (males n=23, females n=34) only the right eye was included. Mean age (± SD) was 35.1±15.2 years (range 19 to 65 years); grouped by age (<40 years [n=34] versus ≥40 years [n=23]). There was no history of ocular diseases, contact lens wear, or previously diagnosed dry eye.

Results
At baseline, there were no significant differences between the three consecutive measures of Kf (p=0.30), Ks (p=0.71), ISI (p=0.10), SAI (p=0.53) and SRI (p=0.34). This was comparable to any amount of NaFl (p>0.05). Median ISI values following the addition of 1 or 2 doses NaFl significantly decreased compared to baseline (both z=3.2, effect size 0.43; p=0.001), irrespective of age group (p=0.74). No significant differences between the three conditions for any other parameter (p>0.05) were found. The intraclass correlation coefficient (ICC) improved for Kf (0.99), Ks (0.99) and SRI (0.60) with one dose of NaFl, compared to baseline or 2 doses of NaFl. For IS and SAI, ICC was most reliable without NaFl (0.85 and 0.77 respectively).

Conclusion
One drop NaFl increases reliability in corneal topography and regularity measurements using the E300 topographer. Corneal asymmetry measurements (IS and SAI) are more reliable without any ocular dye. It is possible that the addition of NaFl enhances tear film reflection during topography measurements, but the addition of a liquid solution decreases symmetry.

Publication Type:	Article
Additional Information:	© Elsevier 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Subjects:	R Medicine > RE Ophthalmology
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences

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