Creating a Full-thickness Choroidal Incision: An Ex Vivo Analysis of Human and Porcine Tissue Contraction Dynamics.

Purpose: We hypothesized that the elastic nature of the choroid leads to tissue contraction following a full-thickness, sharp incision. Furthermore, we sought to quantify, measure, and compare tissue contraction in ex vivo porcine globes and human globes of various ages using predetermined variables.

Method: A full-thickness, ex vivo choroidal incision was performed in either pig ( n = 97) or human ( n = 30) specimens. Variables included trephine diameter (1.5, 2.0, or 2.5 mm) versus a straight surgical blade, and temperature (1.7 °-4.4° vs. 36.6°F). Central centripetal and surround centrifugal tissue contractions were measured. Mean percentage tissue contraction was assessed as a ratio of trephine diameter to final tissue contraction measured immediately following each incision using a standardized device.

Results: For trephination in pig specimens, centripetal contraction ranged from 38% to 50% with a mean of 44%. Centrifugal contraction was approximately 15%. Human choroidal contraction was 39% and 15%, respectively, with a statistically significant inverse relationship to age ( R 2 = 0.35, P ≤ 0.01). Asymmetric contraction was noted when incisions were closer to choroidal attachment sites to the sclera, such as near vortex ampullae. Linear incisions resulted in contraction that correlated with incision length ( R 2 = 0.35, P ≤ 0.001).

Conclusions: A full-thickness choroidal incision results in significant tissue contraction. For circular incisions, the centripetal contraction approaches 50% of the original incision size. For linear incisions, the contraction corresponds directly with incision length. In human specimens, there is less contraction with advancing age.

Translational Relevance: Our findings have clinical relevance for choroidal biopsy, traumatic injury, and choroidal translocation surgery.