Purpose: To investigate the relationship of lamina cribrosa displacement to corneal biomechanical properties and visual function after mitomycin C-augmented trabeculectomy.
Method: Eighty-one primary open-angle eyes were imaged before and after trabeculectomy using an enhanced depth spectral domain optical coherence tomography (SDOCT). Corneal biomechanical properties were measured with the ocular response analyzer before the surgery. The anterior lamina cribrosa (LC) was marked at several points in each of the six radial scans to evaluate LC displacement in response to intraocular pressure (IOP) reduction. A Humphrey visual field test (HVF) was performed before the surgery as well as 3 and 6 months, postoperatively.
Results: Factors associated with a deeper baseline anterior lamina cribrosa depth (ALD) were cup-disc ratio (P = 0.04), baseline IOP (P = 0.01), corneal hysteresis (P = 0.001), and corneal resistance factor (P = 0.001). After the surgery, the position of LC became more anterior (negative), posterior (positive), or remained unchanged. The mean LC displacement was - 42 μm (P = 0.001) and was positively correlated with the magnitude of IOP reduction (regression coefficient = 0.251, P = 0.02) and negatively correlated with age (regression coefficient = - 0.224, P = 0.04) as well as baseline cup-disk ratio (Regression coefficient = - 0.212, P = 0.05). Eyes with a larger negative LC displacement were more likely to experience an HVF improvement of more than a 3 dB gain in mean deviation (P = 0.002).
Conclusion: A larger IOP reduction and younger age was correlated with a larger negative LC displacement and improving HVF. The correlation between lower SDOCT cup-disc ratio and postoperative negative LC displacement was borderline (P = 0.05). Corneal biomechanics did not predict LC displacement.
Keywords: Corneal hysteresis; Glaucoma; Lamina cribrosa; Optic nerve head; Optical coherence tomography; Trabeculectomy; Visual field.