Abstract
Purpose :
Targeting the fovea and the unpredictable direction of the enlarging bleb with respect to the injection point are persistent problems during subretinal injection. Understanding the biomechanical properties of the retina in each quadrant is important to optimise a range of surgical procedures including epiretinal membrane peeling and subretinal injections particularly with respect to the orientation of retinal blood vessels and the foveal centre. We aimed to test the hypothesis that blood vessels play the major role in resisting mechanical deformation. We performed tensile tests to determine the biomechanical properties of the retina in the different quadrants of the eye.
Methods :
A total of 130 retinal strips, dissected from the eyes of six-month old pigs, underwent tensile testing. Strips, both vertical and horizontal, were extracted from each quadrant (n=10 for each group). Their thickness was measured using inverted light microscopy. Testing was executed at ambient temperature using a strain rate of 9 mm/min with samples under a balanced salt solution. The tangent modulus, tensile strength, yield strain and yield stress were determined and statistical analysis performed using the unpaired t-test.
Results :
We found a significant difference (p<0.05) in tensile strength (p=0.0006) and transition modulus (p=0.0008) between the blood vessel group (2.3 ± 0.5 kPa, 5.2 ± 1.5 kPa) and the temporal horizontal group without blood vessels (1.4 ± 0.4 kPa, 2.7 ± 1.1 kPa). Furthermore, a significant difference in tensile strength was also identified between the inferior horizontal and inferior vertical group (p=0.003) and between the nasal horizontal and nasal vertical group (p=0.042).
Conclusions :
The results obtained showed that blood vessels significantly impact the strength and stiffness of the retina. Moreover, the orientation of collagen fibres in the retina might explain why strips without blood vessels are stronger in a specific direction. This information could help improve subretinal injection techniques in the future.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.