Robotic Retinal Surgery’s Impact on Scleral Forces

Robotic assistance is common in ophthalmic surgery and, although it may offer many advantages, it can also bring some challenges. Specifically, the incompatibility of force feedback in robots without sensors. Force sensors potentially have several applications within instruments that, researchers say, could improve the safety of using robotics in clinical environments. . 

A recent study mapped the force interaction between the sclera and instrument tool-shaft using force sensing devices, which then verified changes in force pattern using robotic assistance. The study also tested how a robotic force control could potentially address interaction between the sclera and instrument—essentially, could the force control prevent unwanted force increases on the sclera? The study says it can. 

The study “compared forces during intraocular tasks between manual, robot-assisted manipulation with no force control (RA-NFC), and robot-assisted manipulation with force control (RA-FC).”

To demonstrate their findings, the study authors report the “mean forces using manual manipulations were 115 mN ± 51 mN. Using robotic assistance, mean forces were 118 mN ± 49 mN. Using an active force control method, overall mean forces reduced to 69 mN ± 15 mN, with a statistical difference compared with other methods (P <.001). Comparing intraocular directions, superior sectors required higher forces and the force control method reduced differences in forces between users and retained the same force pattern between them.”  

The researchers found no difference in overall forces between the right (91 mN ± 29 mN) and left eye (93 mN ± 33 mN), (P =.255). A difference was observed using manual manipulations on left eyes between users (surgeon A 111 mN ± 41 mN; surgeon B 196 mN ± 67 mN; P =.001). However, after implementing an active robotic force control, the observed difference in force average between users was similar. Additionally, force patterns in different directions were similar between users, despite differences in mean values. 

Difference in overall forces between surgeon A (90 mN ± 31 mN) and surgeon B (109 mN ± 32 mN) were observed. This difference was verified mainly on free-hand manipulations (111 mN ± 38 mN vs. 140 mN ± 42 mN, P =.001). Although with smaller standard deviations, the use of robotic assistance with force control also has differences (68 mN ± 24 mN vs. 77 mN ± 22 mN, P =.001). The force pattern for different directions, however, was similar using robotic assistance.

“Despite a growing market and numerous technology possibilities, this force assessment might be crucial to verify the relevance of force interaction as a factor in robotic implementation and to emphasize the importance of instrument surgical awareness toward a progressive safety use of robotic assistance,” according to the researchers. 

While the study notes that robotic systems can be useful in micrometric environments that require accuracy and security, investigators noted there are still concerns around safety because increased forces were observed with the introduction of robotic assistance. 

Reference

Urias MG, Patel N, Ebrahimi A, Iordachita I, Gehlbach PL. Robotic retinal surgery impacts on scleral forces: in vivo study. Trans Vis Sci Tech. Published online September 1, 2020. doi: 10.1167/tvst.9.10.2