Is keratoconus associated to thyroid diseases? Assessment of the corneal parameters in patients with congenital hypothyroidism

Abstract

Purpose: To investigate the association between keratoconus and congenital hypothyroidism (CH). Patients and methods: Patients were enrolled in this study and divided into two groups. The first group comprised 31 subjects (11M:20F) with the mean age of 15.2 ± 3.9 years. affected by CH, and the control group was composed by 19 healthy individuals (8M:11F) aged 14.3 ± 4.6 years. All patients underwent complete ophthalmologic examination with visual acuity assessment, refraction, slit lamp examination, and retinoscopy. Corneal parameters were measured using Scheimpflug camera (Pentacam® Oculus, Germany). The main outcome measures considered for evaluation were: average corneal curvature (K), central corneal thickness (CCT), anterior elevation and posterior elevation at the thinnest point, corneal volume (CV), anterior chamber depth (ACD), and anterior chamber volume (ACV). Additionally, data from Belin/Ambrosio Enhanced Ectasia Display (BAD) and the high order aberrations were evaluated. Kolmogorov-Smirnov test was used to verify the Gaussian distribution, the comparison between the controls and cases group was performed by Mann-Whitney nonparametric test. A p value less than 0.05 was considered to be statistically significant. The odds ratio was performed in order to quantify the relationship between the congenital hypothyroidism and abnormal values displayed on front BAD. Results: The significant difference in the refractive status between both groups was observed. As to examined corneal and anterior chamber parameters no statistical differences were detected. Conclusions: Congenital hypothyroidism diagnosed and treated since the early postnatal life doesn’t induce abnormalities of corneal parameters suggestive for keratoconus.

Association between Thyroid Function and Ocular Parameters

“…Previous studies mostly analysed corneal thickness in patients with TED [ 15 , 16 ] and hypothyroidism [ 7 , 17 , 18 , 19 , 20 , 21 ]. In a study that included 27 individuals with TED and 30 healthy individuals, Karabulut et al did not observe a significant difference in central corneal thickness between patients with TED and healthy individuals (with Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) being significantly increased and corneal hysteresis (CH) being significantly decreased in patients with TED) [ 15 ].…”

“…Furthermore, the authors did not observe a change in IOP, anterior chamber parameters, mean retinal thickness, or mean retinal nerve fibre layer (RNFL) in hypothyroidism [ 7 ]. Roszkowska et al tested the association between congenital hypothyroidism and keratoconus (characterised by the thinning and bulging of the cornea in a cone shape) [ 20 ]. In their study that included 31 subjects with congenital hypothyroidism and 19 healthy individuals, they observed no change in corneal parameters (central corneal thickness, corneal curvature, corneal volume and anterior elevation, and posterior elevation at the thinnest point) in diagnosed and treated congenital hypothyroidism [ 20 ].…”

“…Roszkowska et al tested the association between congenital hypothyroidism and keratoconus (characterised by the thinning and bulging of the cornea in a cone shape) [ 20 ]. In their study that included 31 subjects with congenital hypothyroidism and 19 healthy individuals, they observed no change in corneal parameters (central corneal thickness, corneal curvature, corneal volume and anterior elevation, and posterior elevation at the thinnest point) in diagnosed and treated congenital hypothyroidism [ 20 ]. A study that included 40 patients with euthyroid Hashimoto’s thyroiditis (HT) and 48 healthy controls found no difference in central corneal thickness, retinal thickness, and IOP between these two groups, while the levels of TPOAb negatively correlated with the retinal thickness [ 25 ].…”

“…Hypothyroidism did not affect anterior chamber parameters (anterior chamber volume, depth, and angle) [ 7 ]. A change in anterior chamber depth and volume was not observed in congenital hypothyroidism [ 20 ]. IOL power decreased in 64.3% of patients with Graves’ disease after treatment with methimazole, a thionamide antithyroid drug [ 36 ].…”

“…However, our study showed the presence of thicker corneas in patients with hyperthyroidism compared to healthy individuals. In patients with hypothyroidism, either no change [ 7 , 17 , 20 , 25 ], a decrease [ 18 ], or an increase [ 19 , 21 ] in corneal thickness compared to healthy individuals was observed. However, it should be noted that our study lacked ethnic diversity, since it included only Caucasians of Croatian origin.…”