Ocular refractive and biometric characteristics in patients with thalassaemia major

Abstract

Background: Thalassaemia major is associated with characteristic findings in craniofacial bony structures and thereby may render abnormal bony orbit and subsequently distinctive ocular biometry. The purpose of the present study was to evaluate the ocular refractive and biometric characteristics in patients with thalassaemia major.

Methods: This case-controlled study comprised 94 eyes of 47 patients with thalassaemia major and 88 eyes of 44 age- and sex-matched healthy control subjects. All participants had a complete ocular examination including slitlamp biomicroscopy, fundoscopy, ocular biometry, keratometry, refraction and analysis using Fourier transformation.

Results: There were no significant differences in spherical equivalent (p = 0.66) and total astigmatism (p = 0.83) between groups. Mean uncorrected vision and visual acuities (logMar) were similar (p = 0.32 and p = 0.71, respectively). Compared with controls, thalassaemic patients had a shorter axial length (23.01 ± 0.12 [SEM] mm versus 23.46 ± 0.12 mm, p = 0.035), thicker crystalline lens (4.01 ± 0.11 mm versus 3.87 ± 0.1 mm, p = 0.046) and steeper average keratometry (44.02 ± 0.24 D versus 43.44 ± 0.24, p = 0.03). Fifty-seven per cent of thalassaemic patients had against-the-rule astigmatism (total), while 64.6 per cent of controls showed a with-the-rule pattern (p < 0.05). These patterns were also found for corneal astigmatism. The magnitudes of total, corneal and lenticular astigmatism were similar among groups. Regression analysis showed significant correlation between corneal (J0 and J45) and total (J0 and J45) astigmatism. The correlations were less prominent between lenticular and total J0 and J45. The mean intraocular pressure was 14.68 ± 0.27 mmHg and 13.3 ± 0.26 mmHg in the thalassaemia and control groups, respectively (p < 0.001). Six eyes (12.8 per cent) of four patients in the thalassaemia group had posterior subcapsular cataract, while the condition had not been observed in controls (p = 0.049).

Conclusions: Shorter axial length, thicker lens, steeper corneal curvature and more against-the-rule pattern were characteristic findings in patients with thalassaemia major.