Abstract
Purpose :
Hypothyroidism could be associated with keratoconus and may be one of its causing factors. Our aim was to determine the potential impact of blood thyroid hormone levels on corneal topography, tomography and biomechanics.
Methods :
757 eyes (376 left eyes, 500 males) were included in our study. Patients were classified as euthyroid (n=563) or hypothyroid (n=194) based on blood thyroid hormone status (TSH, FT3, FT4). We further subdivided hypothyroid patients in those with (n=122) and without (n=72) medication. Patients were examined using TMS-5 topographer (Tomey, Tennenlohe, Germany)(keratoconus index: KCI; keratoconus severity index: KSI; keratoconus prediction index: KPI), Pentacam HR tomographer (Oculus Optikgeräte GmbH, Wetzlar, Germany)(keratoconus index: KI; central keratoconus index: CKI) and Ocular Response Analyzer (ORA, Reichert Ophthalmic Instruments, Buffalo, NY) (corneal resistance factor: CFR; corneal hysteresis: CH; keratoconus match index: KMI).
Results :
Using Mann-Whitney U test, KCI, KSI, KPI of TMS-5 and KI, CKI of Pentacam were significantly lower in hypothyroid patients with medication compared to euthyoids or hypothyroid patients without medication (p<0.001 for all). In addition, KMI, CH and CRF of ORA were significantly greater in hypothyreosis patients with medication compared to euthyroids or hypothyroid patients without medication (p<0.001 for all). Using a generalised linear model, KMI depended on blood FT3 level (p=0.029), however, other parameters of TMS-5, Pentacam or ORA were not affected significantly by blood TSH, FT3 or FT4 levels (p>0.136).
Conclusions :
Blood TSH, FT3 and FT4 levels may affect keratoconus specific indices of corneal topography and tomography, and corneal biomechanical properties. Unlike in keratoconus, an abnormally increased KMI index of ORA may be indicative for reduced FT3 blood level and hypothyreosis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.