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Effie Zhu Rahman, Peter Lam, Kai Chu, Quianta Moore, Stephen C Pflugfelder; Corneal Sensitivity in Tear Dysfunction and its Correlation with Clinical Parameters and Blink Rate. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):306.
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Tear instability and ocular surface epithelial disease disrupt corneal barrier function, causing ocular irritation and altered corneal innervation. Previous studies comparing corneal sensitivity in normal and dry eyes did not differentiate between subsets of tear dysfunction. Our prospective, clinical case-controlled study compared corneal sensitivity in control and tear dysfunction subjects using contact and non-contact esthesiometers to evaluate correlations between corneal sensitivity, clinical parameters, and blink rate (BR).
We evaluated 43 subjects between 30-85 years old including 10 normal control subjects and 33 subjects with tear dysfunction: 10 with aqueous tear deficiency (ATD) [3 Sjögren syndrome (SS) and 7 non-SS], 12 with conjunctivochalasis (CC), and 11 with meibomian gland disease (MGD). Exclusion criteria included history of contact lens or eye drop use or past ocular surgery. Corneal sensitivity was measured by both Cochet-Bonnet (CB) and air jet esthesiometers (AJE). BR was measured by electromyelography. Severity of eye irritation symptoms (OSDI questionnaire), tear meniscus dimensions, tear break-up time (TBUT), corneal and conjunctival dye staining and Schirmer 1 test scores were measured. Mean between group differences were compared by ANOVA, and Pearson correlations were calculated.
When compared with mean threshold in controls (5.450mm), there was a significantly higher sensory threshold in the ATD group (3.6mm; P= 0.0026) using CB or AJE. AJE mean corneal sensitivity scores in MGD and CC were not significantly different from control. Reduced corneal sensitivity correlated with greater ocular surface staining, higher BR and greater irritation symptoms. Mean BRs were significantly higher in both ATD (37.18 blinks/min; P= 0.0011) and CC (27.44 blinks/min; P= 0.01) when compared with control (14 blinks/min), whereas BR in MGD (18 blinks/min; P = 0.2499) did not differ from control. BR positively correlated with corneal staining (R = +0.448; P = .005), conjunctival staining (R = +0.561; P= .0001), and OSDI score (R = +0.393; P= 0.018), and inversely correlated with TBUT (R = -0.424; P= 0.008).
In tear dysfunction conditions, reduced corneal sensitivity is associated with greater eye irritation symptoms, tear instability, ocular surface disease and BR. Rapid blinking in dry eye appears to exacerbate ocular surface disease and tear stability.
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