Loop memory of posterior chamber intraocular lenses of various sizes, designs, and loop materials

Area of Science:

• Ophthalmology
• Biomaterials Science
• Medical Device Engineering

Background:

• Looped intraocular lenses (IOLs) are crucial for stable ocular fixation.
• IOL loop performance relies on material rigidity and elastic memory.
• Understanding loop memory is key to optimizing IOL design for long-term stability.

Purpose of the Study:

• To evaluate the loop memory of 30 posterior chamber IOLs made from polypropylene (PP) and poly(methyl methacrylate) (PMMA).
• To compare the influence of loop material, diameter, style, and design on IOL fixation stability.
• To determine optimal IOL characteristics for sustained centripetal pressure on the capsular bag.

Main Methods:

• 30 posterior chamber IOLs (PP and PMMA loops) were compressed in 9.5 mm wells in 37°C water for one month.
• Lenses were then allowed to re-expand on an open plate for one month.
• Loop memory was quantified by measuring diameter changes during compression and re-expansion phases.

Main Results:

• Shorter IOLs (12.0–12.5 mm) exhibited better loop memory compared to longer IOLs (13.5–14.0 mm).
• PP loops showed greater and longer expansion than comparable PMMA loops.
• One-piece, all-PMMA IOLs demonstrated the best loop memory, indicating superior design and material properties.

Conclusions:

• IOL loop material (PP vs. PMMA) and design significantly impact long-term fixation stability.
• One-piece, all-PMMA IOLs offer excellent loop memory, enabling reduced total diameter to 12.0 mm.
• Optimized IOL design can ensure sustained capsular bag pressure for stable intraocular fixation.