The possible role of tear fluid thyroxine in keratoconus development

Kahán, I.L.; Varsányi-Nagy, M; Tóth, Miklós; Nadrai, A

doi:10.1016/0014-4835(90)90134-g

Cited by 30 publications

(23 citation statements)

References 11 publications

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“…A major disadvantage of these techniques is that the recorded geometrical deformation parameters are strongly dependent on the IOP and corneal thickness and do not represent a real mechanical tissue properties. Further factors that impede an accurate measurement of in vivo corneal biomechanics is the relatively high inter-individual variability due to age [29], smoking habits [30]–[32], and the hormonal status of estrogens [15], [33], [34] and thyroid hormones [35], [36]. Ex vivo techniques are therefore still preferred when corneal stiffness needs to be quantified.…”

Section: Discussionmentioning

confidence: 99%

A Constant-Force Technique to Measure Corneal Biomechanical Changes after Collagen Cross-Linking

et al. 2014

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PurposeTo introduce a constant-force technique for the analysis of corneal biomechanical changes induced after collagen cross-linking (CXL) that is better adapted to the natural loading in the eye than previous methods.MethodsFor the biomechanical testing, a total of 50 freshly enucleated eyes were obtained and subdivided in groups of 5 eyes each. A Zwicki-Line Testing Machine was used to analyze the strain of 11 mm long and 5 mm wide porcine corneal strips, with and without CXL. Before material testing, the corneal tissues were pre-stressed with 0.02 N until force stabilization. Standard strip extensiometry was performed as control technique. For the constant-force technique, tissue elongation (Δ strain, %) was analyzed for 180 seconds while different constant forces (0.25 N, 0.5 N, 1 N, 5 N) were applied.ResultsUsing a constant force of 0.5 N, we observed a significant difference in Δstrain between 0.26±0.01% in controls and 0.12±0.03% in the CXL-treated group (p = 0.003) over baseline. Similarly, using a constant force of 1 N, Δstrain was 0.31±0.03% in controls and 0.19±0.02% after CXL treatment (p = 0.008). No significant differences were observed between CXL-treated groups and controls with 0.25 N or 5 N constant forces. Standard stress-strain extensiometry failed to show significant differences between CXL-treated groups and controls at all percentages of strains tested.ConclusionWe propose a constant-force technique to measure corneal biomechanics in a more physiologic way. When compared to standard stress-strain extensiometry, the constant-force technique provides less variability and thus reaches significant results with a lower sample number.

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Section: Discussionmentioning

confidence: 99%

A Constant-Force Technique to Measure Corneal Biomechanical Changes after Collagen Cross-Linking

et al. 2014

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“…Several possible mechanisms have been suggested by which excessive levels of thyroxin in tears may affect corneal metabolism and ultimately structural integrity. 29 …”

Section: Autoimmune Diseasesmentioning

confidence: 97%

“…28 These observations suggest that KC may, in some way, be associated with abnormalities of thyroxin production or availability. 29 Accordingly, thyroid extracts were recommended for the treatment of KC. 27 Kahan et al have shown an excess of thyroxin in tears of patients with KC, especially during the progressive phase of corneal reshaping, as compared with that of normal subjects without corneal disease.…”

Section: Autoimmune Diseasesmentioning

confidence: 99%

The Association of Keratoconus With Immune Disorders

Nemet

Vinker

Bahar

et al. 2010

Cornea

139

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“…Previous studies investigated the association between thyroid gland dysfunction and keratoconus, suggesting a positive correlation. [6][7][8][9] In 1936, Appelbaum 6 described a series of patients with keratoconus in whom there was a high prevalence of hypothyroidism symptoms, whereas King 7 reported keratoconus after thyroidectomy. In 1990, Kahán et al 8 reported a possible role of tear fluid thyroxine (T4) in keratoconus development.…”

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confidence: 99%

Association Between Keratoconus and Thyroid Gland Dysfunction: A Cross-Sectional Case–Control Study

Elmassry¹,

Doheim²,

Iqbal³

et al. 2020

J Refract Surg

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K eratoconus is a corneal ectatic disorder that starts at puberty and decreases the radius of curvature of the central cornea. 1 Kennedy et al. 2 reported that the incidence rate is 1 per 50,000 among the population. Moreover, the pathophysiological processes underlying keratoconus have not been fully explained and proposed mechanisms including oxidative dam-age, proteolytic degradation in the corneal stroma, epithelial mechanical injury, immunological factors, and genetic factors have been suggested. [1][2][3][4] reported an incidence of keratoconus in 3.5% to 8% of patients with Down syndrome. Furthermore, hormonal imbalances affect the corneal metabolism and may be associated with keratoconus. Likewise, thyroid gland ABSTRACT PURPOSE: To examine the clinical association between thyroid gland dysfunction and keratoconus. METHODS:This was a cross-sectional case-control study conducted between May 2018 and July 2019. After performing Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) examination, flat, steep, and maximum simulated keratometric readings were recorded for each patient. Serum concentrations of free triiodothyronine, free thyroxine, and thyroidstimulating hormone were measured. Further examinations by an endocrinologist were indicated for patients with positive laboratory results to confirm thyroid gland dysfunction. RESULTS:One hundred eighty-seven patients with bilateral keratoconus and 187 sex-and age-matched healthy controls without keratoconus were analyzed. Mean age was 26.4 ± 8.2 years for the patients with keratoconus and 27.1 ± 9.4 years for the control patients, with no significant difference. The results showed that thyroid gland dysfunction prevalence was 10 of 187 patients with keratoconus (5.3%) and 2 of 187 control patients (1.1%), and the difference was statistically significant (P = .036). For the patients with keratoconus and thyroid gland dysfunction, 8 were women and 2 were men. Additionally, 6 patients (2 men and 4 women) had hyperthyrosis and 4 women had hypothyrosis. For controls, the two patients had hypothyrosis. CONCLUSIONS:This study showed that there is a possible association between keratoconus and thyroid gland dysfunction, but more studies are needed to build upon these results.[J Refract Surg. 2020;36(4):253-257.] (AT). © 2020 El-Massry, Doheim, Iqbal, et al.; licensee SLACK Incorporated. This is an Open Access article distributed under the terms of the Creative Commons . This license allows users to copy and distribute, to remix, transform, and build upon the article non-commercially, provided the author is attributed and the new work is non-commercial.

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The possible role of tear fluid thyroxine in keratoconus development

Cited by 30 publications

References 11 publications

A Constant-Force Technique to Measure Corneal Biomechanical Changes after Collagen Cross-Linking

A Constant-Force Technique to Measure Corneal Biomechanical Changes after Collagen Cross-Linking

The Association of Keratoconus With Immune Disorders

Association Between Keratoconus and Thyroid Gland Dysfunction: A Cross-Sectional Case–Control Study

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