Sir,

Corneas of diabetic patients exhibit remarkable abnormalities of nerves, basement membranes, and cellular layers.1 Confocal microscopy has become a popular technique to observe the structure of cornea in vivo in several disease states afflicting the cornea including diabetes mellitus.2, 3 Among the less common observations in the corneas of diabetic patients are the faint vertical lines at the level of Descemet's membrane and endothelium, initially described by Waite and Beetham4 and Henkind and Wise.5 The purpose of this paper was to report the characteristics and incidence of Waite–Beetham lines in the corneas of diabetic patients.

Case report

The study was carried out with approval from the Institutional Review Board. Clinical evaluation and data collection of all patients was performed by a single ophthalmologist (MI). In vivo confocal microscopy were performed using Confoscan 3.0 (Vigonza, Italy) attached to an immersion lens (Achroplan × 40/0.75W, Zeiss, Germany). The presence of vertical lines at the level of Descemet's membrane and endothelial cell counts were evaluated by a single observer (MCM) who was masked to the patients' identities and disease status throughout the evaluation.

Thirty-five corneas of 35 type II diabetic patients (17 men and 18 women) with a mean age of 54.5±8.5 years and 24 corneas of 24 age-matched nondiabetic subjects (11 men and 13 women) with a mean age of 58.4±10.0 years were included in the analysis. Slit-lamp evaluation revealed very thin vertical lines at the Descemet's membrane in 13 (37.1%) diabetic patients and two (8.3%) normal subjects (t-test, P=0.005). Faint vertical lines at the level of Descemet's membrane (Figure 1a) were detected with the in vivo confocal microscope in 23 of 35 corneas (65.7%) compared to four of 24 corneas of control subjects (16.7%) (t-test, P<0.001). The lines were mostly vertical with occasional oblique or horizontal orientations. They were most prominent at the level of Descemet's membrane and the neighbouring posterior stroma (Figure 1b). Waite–Beetham lines observed clinically in 13 diabetic and two control subjects were also detected with the confocal microscope.

Figure 1
figure 1

Faint (a) and prominent (b) vertical lines at the level of Descemet's membrane and the neighbouring posterior stroma of diabetic patients.

Full size image

The mean age of diabetic patients who had the Waite–Beetham lines (59.5±9.7 years) was not significantly different from the mean age of diabetic patients who did not have them (56.3±10.8 years) (Mann–Whitney U-test, P=0.404). In addition, there was also no statistically significant difference between the mean ages of 23 diabetic patients (59.5±9.7 years) and four control (62.0±8.6 years) subjects who demonstrated evidence of the Waite–Beetham lines (Mann–Whitney U-test, P=0.733).

The mean endothelium cell count of diabetic patients (2678.0±507.6 cells/mm2) was not significantly different from that of normal subjects (2631.8±417.0 cells/mm2) (t-test, P=0.714). In addition, the mean endothelium cell count of diabetic patients who had Waite–Beetham lines (2713.1±542.0 cells/mm2) appeared similar to that of diabetic patients who did not have them (2611.0±449.0 cells/mm2) (Mann–Whitney U-test, P=0.322).

Comment

Folds at the level of endothelium and Descemet's membrane may be observed in the setting of contact lens-induced hypoxia in association with other signs of corneal hypoxia such as epithelial microcysts and oedema.6 Although they may be regarded as a sign of corneal hypoxia, a recent study by O'Donnell et al6 have observed such lines in the corneas of four out of 40 diabetic contact lens users with a mean age of 34.0±13.0 years and none of the age-matched nondiabetic contact lens users and have suggested that these folds are not indicative of hypoxia in all cases. Our results additionally suggest that these folds are not associated with loss of endothelial cells. However, ageing may be a risk factor in the development of the Waite–Beetham lines as they were detected in 16.7% of our normal subjects (mean age=57.4 years) as well. In conclusion, the results of our study suggest that Waite–Beetham lines may be more common in the corneas of diabetic patients than can be clinically appreciated and may represent accelerated tissue ageing. The inciting stimulus for the development of Waite–Beetham lines, be it either metabolic or mechanical, continues to remain elusive.