Correction Method for Optical Scaling of Fundoscopy Images: Development, Validation, and First Implementation

Investigative Ophthalmology & Visual Science, vol. 65, pp. 43

Abstract

Purpose: Although fundus photography is extensively used in ophthalmology, refraction prevents accurate distance measurement on fundus images, as the resulting scaling differs between subjects due to varying ocular anatomy. We propose a PARaxial Optical fundus Scaling (PAROS) method to correct for this variation using commonly available clinical data. Methods: The complete optics of the eye and fundus camera were modeled using ray transfer matrix formalism to obtain fundus image magnification. The subject's ocular geometry was personalized using biometry, spherical equivalent of refraction (RSE), keratometry, and/or corneal topography data. The PAROS method was validated using 41 different eye phantoms and subsequently evaluated in 44 healthy phakic subjects (of whom 11 had phakic intraocular lenses [pIOLs]), 29 pseudophakic subjects, and 21 patients with uveal melanoma. Results: Validation of the PAROS method showed small differences between model and actual image magnification (maximum 3.3%). Relative to the average eye, large differences in fundus magnification were observed, ranging from 0.79 to 1.48. Magnification was strongly inversely related to RSE (R2 = 0.67). In phakic subjects, magnification was directly proportional to axial length (R2 = 0.34). The inverse relation was seen in pIOL (R2 = 0.79) and pseudophakic (R2 = 0.12) subjects. RSE was a strong contributor to magnification differences (1%-83%). As this effect is not considered in the commonly used Bennett-Littmann method, statistically significant differences up to 40% (mean absolute 9%) were observed compared to the PAROS method (P < 0.001). Conclusions: The significant differences in fundus image scaling observed among subjects can be accurately accounted for with the PAROS method, enabling more accurate quantitative assessment of fundus photography.

Authors 10

1. Lennart J. Pors corresponding Aachen Department of Ophthalmology, Leiden University Medical Center Department of Radiation Oncology

   Leiden University Medical Center · ORCID

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0003-0907-6637

2. Corné Haasjes Aachen Department of Ophthalmology, Leiden University Medical Center Department of Radiation Oncology Department of Radiology, Leiden University Medical Center

   Leiden University Medical Center · ORCID

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands

   Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0003-0187-4116

3. Luc van Vught Aachen Department of Ophthalmology, Leiden University Medical Center Department of Radiology, Leiden University Medical Center

   Leiden University Medical Center · ORCID

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0001-8290-9071

4. Noor P. Hoes Aachen Department of Ophthalmology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0009-0005-2024-9676

5. Gregorius P. M. Luyten Aachen Department of Ophthalmology, Leiden University Medical Center

   Leiden University Medical Center · ORCID

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0003-3685-3868

6. Gwyneth A. van Rijn

   Amsterdam UMC Location University of Amsterdam · Noordwest Ziekenhuisgroep · Amsterdam University Medical Centers

   Affiliation as printed

   Department of Ophthalmology, Amsterdam University Medical Center, Amsterdam, the Netherlands

   Department of Ophthalmology, Northwest Clinics, Alkmaar, the Netherlands

   https://orcid.org/0000-0003-3835-1087

7. T. H. Khanh Vu Aachen Department of Ophthalmology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0003-1809-4001

8. Coen R. N. Rasch Aachen Department of Radiation Oncology

   Leiden University Medical Center

   Affiliation as printed

   Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0001-6950-3376

9. Nanda Horeweg Aachen Department of Ophthalmology, Leiden University Medical Center Department of Radiation Oncology

   Leiden University Medical Center · ORCID

   Affiliation as printed

   Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

   Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands

   https://orcid.org/0000-0002-8581-4753

10. Jan‐Willem M. Beenakker Aachen Department of Ophthalmology, Leiden University Medical Center Department of Radiation Oncology Department of Radiology, Leiden University Medical Center

    Leiden University Medical Center

    Affiliation as printed

    Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands

    Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands

    Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands

    https://orcid.org/0000-0003-0479-5587