Original article
Corneal Sensitivity in Tear Dysfunction and its Correlation With Clinical Parameters and Blink Rate

https://doi.org/10.1016/j.ajo.2015.08.005Get rights and content

Purpose

To compare corneal sensitivity in tear dysfunction due to a variety of causes using contact and noncontact esthesiometers and to evaluate correlations between corneal sensitivity, blink rate, and clinical parameters.

Design

Comparative observational case series.

Methods

Ten normal and 33 subjects with tear dysfunction (meibomian gland disease [n = 11], aqueous tear deficiency [n = 10]—without (n = 7) and with (n = 3) Sjögren syndrome (SS)—and conjunctivochalasis [n = 12]) were evaluated. Corneal sensitivity was measured with Cochet-Bonnet and air jet esthesiometers and blink rate by electromyography. Eye irritation symptoms, tear meniscus height, tear break-up time (TBUT), and corneal and conjunctival dye staining were measured. Between-group means were compared and correlations calculated.

Results

Compared with control (Cochet-Bonnet 5.45 mm, air esthesiometer 3.62 mg), mean sensory thresholds were significantly higher in aqueous tear deficiency using either Cochet-Bonnet (3.6 mm; P = .003) or air (11.7 mg; P = .046) esthesiometers, but were not significantly different in the other groups. Reduced corneal sensitivity significantly correlated with more rapid TBUT and blink rate and greater irritation and ocular surface dye staining with 1 or both esthesiometers. Mean blink rates were significantly higher in both aqueous tear deficiency and conjunctivochalasis compared with control. Among all subjects, blink rate positively correlated with ocular surface staining and irritation and inversely correlated with TBUT.

Conclusion

Among conditions causing tear dysfunction, reduced corneal sensitivity is associated with greater irritation, tear instability, ocular surface disease, and blink rate. Rapid blinking is associated with worse ocular surface disease and tear stability.

Section snippets

Study Oversight

The institutional review board (IRB) at Baylor College of Medicine approved the study protocol to conduct clinical assessments in a prospective manner in which normal, non–dry eye subjects and those with tear dysfunction were enrolled for research participation after written informed consent. No retrospective IRB approval was necessary. Our study complies with the Health Insurance Portability and Accountability Act.

Study Design

Data for this comparative observational case series were collected from April 1,

Study Population

The demographic features for control and tear dysfunction subjects are presented in Table 2. Age ranged from 30 to 85 years (61.82 ± 12.77 [mean ± standard deviation]) in the 33 tear dysfunction subjects and from 25 to 79 years (47.4 ± 21.69 [mean ± standard deviation]) in the 10 control subjects. There was a statistically significant difference in age between all tear dysfunction (61.82 years) and control (47.4 years) subjects (P = .006), and between conjunctivochalasis (66.92 years) and

Discussion

In this study, we found corneal sensitivity to be reduced in the aqueous tear deficiency subset. Reduced corneal sensitivity was associated with greater eye irritation symptoms, tear instability, ocular surface disease, and blink rate. Previously published studies that evaluated corneal sensitivity in patients with dry eye have reported conflicting results (Supplemental Table, available at AJO.com).2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 17, 19 Eleven studies have shown subjects with dry eye

Effie Z. Rahman received her BA in Biochemistry/Cell Biology, Psychology, and Ecology/Evolutionary Biology at Rice University. She is currently a fourth year medical student at Baylor College of Medicine with plans to pursue a career in academic ophthalmology.

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      These contradictory findings could stem from differences in the model of the Belmonte aesthesiometer used and the considerable heterogeneity of DED patients. In line with this, another study reported reduced corneal mechanical sensitivity by both contact and non-contact aesthesiometry in aqueous-deficient DED but not in meibomian gland dysfunction DED patients(Rahman et al., 2015). A large, more recent study showed heterogeneity in corneal mechanical sensitivity in DED patients(Galor et al., 2021): 13% of cases had reduced mechanical thresholds (hyperesthesia) that were associated with worse symptoms and 10% of cases had increased mechanical thresholds (hypoesthesia) that were associated with worse corneal epitheliopathy.

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    Effie Z. Rahman received her BA in Biochemistry/Cell Biology, Psychology, and Ecology/Evolutionary Biology at Rice University. She is currently a fourth year medical student at Baylor College of Medicine with plans to pursue a career in academic ophthalmology.

    Peter K. Lam, MD, received his medical degree from Baylor College of Medicine, Houston, Texas. He currently serves as a resident in the Transitional Year Department at UCLA-Harbor Medical Center, Torrance, California. After his internship, Dr. Lam will continue to pursue his ophthalmology residency at Louisiana State University, Shreveport, Louisiana.

    Supplemental Material available at AJO.com.

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