Retinal Image Magnification Calculator — Complete User Guide
Visual field angle↔actual size conversion, axial length influence correction, Goldmann stimulus field and fundus photography localization.
retinal magnificationvisual field angleGoldmannlesion sizeaxial length correction
Why Calculate Retinal Image Magnification?
The human eye can be simplified as a focal optical system. Objects at different eccentricities project to different sizes on the retina. Retinal image magnification calculation is essential for:
- Converting visual field measured angles to actual lesion sizes on fundus
- Comparing fundus photography and visual field examination results
- Calculating approximate size of fundus lesions
Key Formulas
Retinal Image Size (mm)
Retinal size = Visual field angle (°) × 0.3 mm/° × (24/axial length in mm)
Correction for Different Axial Lengths
For a standard eye (axial length 24mm), 1° visual field ≈ 0.3mm on retina
For eyes with different axial lengths, multiply by correction factor: 24/AL
Clinical Applications
- Goldmann visual field to fundus: Convert Goldmann stimulus size to actual retinal size
- Fundus photography: Estimate lesion size based on visual field defect
- Disease monitoring: Track lesion size changes over time
References
- Rubin GS. Visual Acuity and the Maturation of the Human Fovea. Invest Ophthalmol Vis Sci. 1986.
- Bengtsson B, Krakau CE. Correction of optical distortion in fundus photographs. Acta Ophthalmol. 1992.