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Published on: March 3, 2023
Equivalent refractive index of the human lens upon accommodative response
Erik A Hermans1, Michiel Dubbelman, Rob Van der Heijde
1Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands. ea.hermans@vumc.nl
Summary
The human lens equivalent refractive index does not change with accommodation, contrary to Gullstrand's 1909 hypothesis. This study found a constant refractive index, even when accounting for accommodative lag.
Area of Science:
- Ophthalmology
- Optics
- Human Physiology
Background:
- Gullstrand (1909) proposed that the human lens's equivalent refractive index increases during accommodation.
- Understanding lens optics is crucial for visual function and ophthalmic interventions.
Purpose of the Study:
- To experimentally test Gullstrand's hypothesis regarding the human lens equivalent refractive index and accommodation.
- To investigate changes in lens refractive index during the accommodative process.
Main Methods:
- Scheimpflug photography and aberrometry were used to measure lens and corneal shape and refractive error during accommodation.
- Axial length was measured using an IOL-master.
- A two-compartment lens model (nucleus and cortex) was constructed to analyze optical properties.
Main Results:
- No significant change in the equivalent refractive index of the lens was observed with accommodation in five subjects.
- The mean equivalent refractive index was 1.435 +/- 0.008.
- Accommodative lag was observed, and a two-compartment model with constant refractive indices (nucleus: 1.406, cortex: 1.381) could simulate the lens's optical power.
Conclusions:
- The study refutes Gullstrand's hypothesis, finding no increase in equivalent refractive index with accommodation when accommodative lag is considered.
- The accommodative process can be simulated using a two-compartment lens model with fixed refractive indices.
- This finding has implications for understanding ocular optics and developing accurate refractive models.
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