## 4 Discussion  
Ex vivo studies on corneal biomechanical properties have, so far, involved inflation tests with cornea buttons (artificial anterior chambers) or whole eye globes [29; 30; 31; 32]. Different approaches have been used previously to monitor the dynamic response of the cornea [2; 8; 9; 10; 29; 33]. In this study, ex vivo inflation test using air-puff non-contact indentation was applied to assess the reaction of porcine eye globes to rapid stimulus. The porcine eye model and the IOP control system provided well-defined experimental conditions that are close to in vivo tests but might be extremely hard to achieve in the in vivo experiment. Figure 7: Impact of the IOP on corneal velocity for Type 1 air-puff stimuli. (**A**) Time-dependence of corneal velocity profiles for various IOP levels (10–30 mmHg). (**B**) The velocity peak during loading (CVL) and recovery (CVR) phases for various IOP. (**C**) Time between (\(\Delta\)tv) velocity extrema for various IOP. Circles indicate outliers, and asterisks depict extreme outliers. The measurements of corneal deformation with air-puff SS-OCT offer several advantages over existing technology that combines air puff stimulation and Scheimpflug imaging (Corvis ST). The high acquisition speed of our system is at least one order of magnitude higher than the frame rate of Scheimpflug camera. However, our data acquisition is confined to a single apical location. Moreover, the axial resolution of OCT images is higher than that in Scheimpflug imaging, which is directly associated with the inherent precision of corneal surface segmentation. Despite differences between OCT- and Scheimpflug-based assessment of air-puff induced deformation, both approaches implement methodologies to correct observed effects for whole eye globe retraction. We completed hardware modifications with respect to other reports on air-puff SS-OCT to enable more precise assessment of corneal reaction to air-puff stimulus. In particular, an additional optical beam, illuminating the back of the eye, was introduced, forming the dual-sample-arm OCT system. Although the presented design cannot be easily implemented in in vivo experiments, such a cost-efficient hardware change enables easy depth multiplexing, and the measurement with this configuration corresponds to operation of two perfectly synchronized OCT set-ups. Therefore, this approach allows for simultaneous monitoring of both the deformation of the corneal apex and backward movement of the sclera in the posterior pole of the eye globe. As a result, we were able to correct the observed effects for eye retraction. We investigated the behavior of the porcine corneas under different dynamic mechanical stimuli for different IOP levels. This allowed us to determine the relation between the biomarkers extracted from time-dependent corneal deformation and the IOP. The experiments performed in this report were motivated by the quest for a softer and more tolerable mechanical stimulation used in clinical non-contact tonometers. The study comprised three levels (types) of air-puff pressure that were easily set by the puff driver. Therefore, different loading rates can be achieved. However, it must be emphasized here that modifying a single parameter represents a more scientifically sound approach. Thus, the ideal case would include a full control of both amplitude and duration of the air puff to decouple both effects, but it is difficult to obtain experimentally without complex solutions [12]. Corneal deformation is a complex interplay between geometric and biomechanical parameters of the ocular tissues as well as the external factors such as IOP. We do not consider the effects to be associated with the IOP loading rate as the IOP was changed stepwise [33]. The pilot experiments shown in Figure 2 revealed that corneal and scleral displacements are influenced by the number of air-puff tests, and the effects cannot be simply explained by the associated CCT changes. This effect necessitated the implementation of a pre-conditioning stage.