Abstract
Purpose :
At ARVO 2021, our team reported on the effect of differing tip shapes on IOL injectors. The study indicated resistance during insertion could be affected by shape, size, material, and surface roughness of the injector. The current study investigates the effect on insertion due purely to tip shapes using three parameters, bevel angle, slit length, and diameter of the nozzle .
Methods :
We prepared a sample that was scaled up from the actual injector.
The study evaluated a control sample consisting of a round polypropylene bar (6 mm in diameter). The treatment samples included:
(1) Slit length (3, 4, 5 mm *slit width 1.2 mm) (6 mm in diameter)
(2) Bevel angle (35, 45, 55°) (6 mm in diameter)
(3) Diameter of the nozzle (4 mm from the tip – 7.0, 7.5, 8.0 mm)
The following testing procedure was used:
A silicone sheet (thickness=0.4 mm) was used to simulate a cornea. After making an incision of 6.5±0.1 mm, the injector tip was inserted in the silicone at a speed of 2 mm/sec with a universal material testing machine (AGS-50NX). (1) and (3) were inserted for 4.6 mm depth to pass common use . (2) was inserted for 9 mm depth to pass the bevel root.
The maximum value of the resistance during insertion was measured 17 times for each master model injector. The resistance values were compared between control and treatment samples. P<0.05 was considered statistically significant.
Results :
The maximum value of insertion resistance (N) was significantly lower at all bevel angles compared to the control group as reported below:
Control group: 6.88 ±0.564 N
Bevel angle: 35 degree = 5.11 ±0.587 N (P < 0.05), 45° = 3.81 ±0.337 N (P < 0.05), 55° = 2.77 ±0.316 N (P < 0.05)
Slit length: 3 mm = 6.73 ±0.728 N (P = 0.25, t-test), 4 mm = 7.34 ±0.660 N (P < 0.05),
5 mm = 7.91 ±0.769 N (P < 0.05)
Diameter of the nozzle : 7 mm = 7.00 ±0.513 N (P = 0.26), 7.5 mm = 7.82 ±0.839 N (P < 0.05),
8 mm = 8.13 ±0.517 N (P < 0.05)
Conclusions :
The outcomes of this study suggest that the bevel angle had the greatest effect on the ease of injector insertion. With a sharp bevel tip, the bevel root angle is more obtuse, and sudden resistance on the injector is less likely, reducing the chances of the bevel root being stuck in the incision. Therefore, injectors with a sharp bevel tip experienced significantly lower resistance when the bevel root passed through the silicone sheet.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.