Corneal Hysteresis Is Correlated with Reduction in Axial Length After Trabeculectomy

Background: We sought to determine whether corneal biomechanical parameters are predictive of reduction in axial length after anti-metabolite trabeculectomy. Methods: Chinese subjects undergoing trabeculectomy with mitomycin C by a single experienced surgeon underwent the following measurements: Corneal hysteresis (CH, Ocular Response Analyzer, Reichert Ophthalmic Instruments), Goldmann intra-ocular pressure (IOP), central corneal thickness (CCT) and axial length (AL, IOLMaster, Carl Zeiss Meditec, Dublin, CA) were measured pre-operatively, and AL, CH and IOP were measured 1 day and 1 week post-operatively. Results: Mean age of 31 subjects was 52.0 +/- 15.2 years, and 15 (48.4%) were female. The mean pre-operative IOP of 21.4 +/- 9.3 mmHg was reduced to 8.2 +/- 4.6 mmHg 1 day and 11.0 +/- 4.4 mmHg 1 week post-operatively (p < 0.001). AL declined from 22.99 +/- 0.90 to 22.76 +/- 0.87 mm at 1 day and 22.74 +/- 0.9 mm at 1 week; 30/31 (%) eyes had a decline in AL (p < 0.001, sign test). In multivariate linear regression models including post-operative data from 1 day and 1 week, greater decline in Goldmann IOP (p < 0.0001, greater pre-op axial length (p < 0.001) and lower pre-operative CH (p = 0.03), were all associated with greater decline in post-operative axial length. Conclusions: Eyes with lesser ability of the ocular coat to absorb energy (lower CH) had significantly greater decrease in axial length after trabeculectomy-induced IOP-lowering.