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M. B. Abelson, G. W. Ousler, III, D. Welch, B. Nentwig; Symptomatic Break-Up Time (SBUT) in Dry Eye Patients with Normal vs. Low Corneal Sensitivity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4675.
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Studies have shown that approximately 70% of patients diagnosed with dry eye report ocular awareness followed by discomfort after Tear Film Break-Up Time (TFBUT). A test known as the Symptomatic Tear Film Break-Up Time (SBUT) or time to patient reported ocular discomfort while staring is a useful method for measuring this event. It is believed that SBUT is one of the mechanisms responsible for triggering the blink. A critical component in a patient’s ability to report ocular discomfort after TFBUT is the sensitivity of the cornea. Since corneal sensitivity has been shown to decrease in dry eye patients over time, this retrospective analysis was performed to evaluate SBUT in dry eye patients who have normal corneal sensitivity (≥55 mm) versus those who have low corneal sensitivity (<55 mm).
Fifty-one patients diagnosed with dry eye underwent the following examinations: corneal sensitivity as measured by a Cochet-Bonet esthesiometer, TFBUT using 5 micro-liters of non-preserved 2% sodium fluorescein, and SBUT. Subject eyes were then assigned to the normal corneal sensitivity group (≥55 mm) or the low corneal sensitivity group (<55 mm) and SBUT were compared.
Eighty-four eyes had normal corneal sensitivity with a mean score of 58.82 ± 2.13 while eighteen eyes had low corneal sensitivity with a mean score of 47.94 ± 3.09. TFBUT for each group was 2.44 ± 1.10 sec. and 2.21 ± 0.49 sec., respectively, and were not significantly different. SBUT for patients with normal corneal sensitivity was 6.37 ± 3.31 sec. while patients with low corneal sensitivity was 9.24 ± 6.78 sec. and were significantly different (p = 0.009).
The data show that dry eye patients with low corneal sensitivity have longer SBUT when compared to those with normal corneal sensitivity. Dry eye patients with low corneal sensitivity who take longer to report ocular discomfort after TFBUT may be at greater risk of ocular surface exposure during the blink cycle.
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