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Meridian-Dependent Geometric Planning for Pars Plana Scleral Fixation: An Orientation-Adjusted Analytical Model
Goran Marić1, Danny A Mammo2, Damir Godec3
1Department of Ophthalmology, University Hospital Center Sestre Milosrdnice, Vinogradska Cesta 29, 10000 Zagreb, Croatia.
Diagnostics (Basel, Switzerland)
|July 15, 2026
Summary
This study introduces a geometric framework for planning secondary intraocular lens (IOL) scleral fixation, accounting for corneal shape. An orientation-dependent model improves fixation accuracy compared to fixed-distance methods.
Area of Science:
- Ophthalmology
- Geometric optics
- Surgical planning
Background:
- Secondary intraocular lens (IOL) implantation requires precise scleral fixation.
- Current methods may not fully account for corneal geometric variations.
- Limitations exist in fixed limbus-distance marking strategies.
Purpose of the Study:
- To develop a geometric framework for scleral fixation planning in secondary IOL implantation.
- To analyze limitations of fixed limbus-distance marking.
- To incorporate corneal ellipticity and meridional orientation into planning.
Main Methods:
- Modeled limbal boundary as an ellipse using white-to-white (WTW) diameters.
- Defined target scleral locus relative to an anatomical center.
- Determined fixation points using an orientation-dependent limbal offset model.
Main Results:
- A constant limbus-distance strategy leads to meridional deviations with elliptical corneas.
- The orientation-dependent model maintains fixation points on a consistent locus.
- Maximal deviation from the intended locus was approximately 0.58 mm with constant distance strategy.
Conclusions:
- Scleral fixation planning is a geometric problem influenced by limbal ellipticity and orientation.
- An orientation-dependent model offers reproducible, technique-independent fixation planning.
- This approach reduces reliance on fixed-distance heuristics for improved accuracy.
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