# Dislocation force of scleral flange-fixated intraocular lens haptics

## TL;DR

This study measures how different materials and tools affect the force needed to dislodge intraocular lens haptics in eye surgery.

## Contribution

The study introduces a method to measure dislocation forces based on haptic material, flange size, and needle type in scleral tunnels.

## Key findings

- PVDF haptic flanges with a mushroom-like shape showed higher dislocation forces (1.58 ± 0.68 N) compared to PMMA haptics (0.70 ± 0.14 N) with conic shapes.
- Flange size correlated strongly with dislocation force (r = 0.92) when flanges were larger than 384 micrometres.
- Forceps-assisted PMMA flanges did not improve dislocation resistance compared to PVDF haptics.

## Abstract

To measure the dislocation forces in relation to haptic material, flange size and needle used.

Hanusch Hospital, Vienna, Austria.

Laboratory Investigation.

30 G (gauge) thin wall and 27 G standard needles were used for a 2 mm tangential scleral tunnel in combination with different PVDF (polyvinylidene fluoride) and PMMA (polymethylmethacrylate haptics). Flanges were created by heating 1 mm of the haptic end, non-forceps assisted in PVDF and forceps assisted in PMMA haptics. The dislocation force was measured in non-preserved cadaver sclera using a tensiometer device.

PVDF flanges achieved were of a mushroom-like shape and PMMA flanges were of a conic shape. For 30 G needle tunnels the dislocation forces for PVDF and PMMA haptic flanges were 1.58 ± 0.68 N (n = 10) and 0.70 ± 0.14 N (n = 9) (p = 0.003) respectively. For 27 G needle tunnels the dislocation forces for PVDF and PMMA haptic flanges were 0.31 ± 0.35 N (n = 3) and 0.0 N (n = 4), respectively. The flange size correlated with the occurring dislocation force in experiments with 30 G needle tunnels (r = 0.92), when flanges were bigger than 384 micrometres.

The highest dislocation forces were found for PVDF haptic flanges and their characteristic mushroom-like shape for 30 G thin wall needle scleral tunnels. Forceps assisted flange creation in PMMA haptics did not compensate the disadvantage of PMMA haptics with their characteristic conic shape flange.