A spreadsheet-based algorithm for objective assessment of depth of focus from defocus curves

Area of Science:

• Ophthalmology
• Optical Engineering
• Biomedical Instrumentation

Background:

• Accurate depth of focus (DoF) calculation is crucial for evaluating intraocular lenses (IOLs).
• Current methods may involve subjective interpretation and significant manual workload.
• Reproducible and objective quantification of DoF is needed for clinical validation.

Purpose of the Study:

• To develop and clinically validate a spreadsheet-based algorithm for reproducible depth of focus (DoF) calculation.
• To incorporate rule-based continuity detection derived from defocus-curve topology.
• To minimize subjective interpretation and manual workload in DoF quantification.

Main Methods:

• A spreadsheet algorithm was developed to identify dioptric crossings of a logMAR threshold using linear interpolation.
• Defocus curves from 30 pseudophakic eyes with monofocal IOLs were analyzed (-4.0 to +1.5 D).
• Automated results were compared with manual measurements from two experienced operators, with logic for classifying curve profiles.

Main Results:

• The algorithm demonstrated high agreement with manual measurements (mean differences of -0.01 D and 0.00 D).
• Mean absolute error was less than 0.05 D, with narrow Bland-Altman limits of agreement.
• Depth of focus ranged from 1.10 to 3.17 D (mean 1.92 ± 0.47 D) in the studied pseudophakic eyes.

Conclusions:

• The proposed spreadsheet-based algorithm provides objective and reliable depth of focus quantification.
• The method effectively minimizes subjective interpretation and reduces manual workload.
• Topology-based continuity logic offers a structured approach for analyzing complex defocus curves.