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.

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.

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