Corneal elevation changes after forced eyelid closure in healthy participants and in patients with keratoconus

Abstract

Background

To assess pointwise corneal elevation changes after forced eyelid closure test (FECT) in the eyes of healthy subjects and in eyes with keratoconus.

Methods

Twenty‐nine subjects with keratoconus and 31 healthy volunteers were evaluated. Patients with keratoconus who had corneal hydrops, apical scarring, corneal thickness ≤ 400 μm, ocular surface disease, contact lens wear on the examination day and a history of corneal cross‐linking were excluded. Exclusion criteria for healthy participants were spherical error > +3.00 D and < −3.00 D, corneal astigmatism > 1.50 D, corneal curvature > 47 D, ocular allergy, clinical findings and family history of keratoconus. Pentacam was performed before and after 20-seconds of FECT and raw data were extracted from the built‐in software. Pointwise anterior and posterior elevation changes in the central 8-mm cornea were assessed using paired samples t‐test and heat maps were constructed to reflect mean changes and statistically significant data points. Statistical significance was assumed at p < 0.01.

Results

Age and gender were similar between healthy subjects (24.5 ± 1.6-years, 46.4 per cent female) and subjects with keratoconus (28.6 ± 9.2-years, 46.4 per cent female, p = 0.19, 0.61, respectively). Healthy eyes displayed posterior depression clustering in the inferotemporal and inferonasal areas (mean change: −4.5 ± 7.8 μm and −5.2 ± 9.8 μm, respectively, all p < 0.01). In contrast, keratoconus eyes exhibited a wider area of posterior elevation clustering in the inferior cornea (mean change: 8.1 ± 14.5 μm, all p < 0.01) with a small extension in the inferotemporal cornea (mean change: 12.1 ± 22.3 μm, all p < 0.01).

Conclusion

FECT elicits corneal elevation changes mainly in the inferior cornea with the change being more pronounced and wider in eyes with keratoconus.

Key words:

• biomechanics
• corneal elevation changes
• corneal tomography
• forced eyelid closure
• keratoconus
• Pentacam

Supporting information

Additional supporting information may be found in the online version of this article at the publisher’s website: http://onlinelibrary.wiley.com/doi//suppinfo.

Figure S1. Pointwise average differences (in μm) for anterior and posterior elevation maps in eyes of healthy subjects and in eyes with keratoconus. Warmer colours indicate posterior elevation while cooler colours indicate posterior depression from baseline. The inner and outer circles delineate the 5 and 8-mm central cornea, respectively. Upper row: anterior elevation, Lower row: posterior elevation, A, C: healthy subjects, B, D: keratoconus, N: nasal, T: temporal.