Over the past 150+ years, dozens of human eye models have been proposed to support research and development in vision science, ophthalmic optics, and biomedical imaging. Each model reflects different assumptions about wavelength range, pupil size, accommodation state, and field of view.
This article presents practical human eye models built using standard glass catalog data, suitable for optical simulation and system design. These models are intentionally flexible—you are encouraged to modify wavelengths, pupil size, and field weighting to match your specific application.
There is no single “best” eye model. The right model depends on what you are trying to predict.
Simplifying the Human Eye in Optical Models
In optical design software such as Zemax OpticStudio, the eye is often simplified to:
A small number of refractive surfaces (cornea, lens)
A defined pupil (aperture stop)
A retinal surface acting as either:
An object, or
An image
The key modeling choice is whether to use a Sequential or Non-Sequential approach.
Sequential Eye Model
Sequential eye models are used when light propagation follows a defined surface order. They are computationally efficient and ideal for image formation analysis.
There are two common use cases.
1. Retina as the Object (External Viewing)
In applications such as:
- Ophthalmoscopes
- Fundus cameras
- Retinal imaging systems
The retina is treated as the object surface, and light propagates outward through the eye toward an external optical system.
This configuration is commonly referred to as an Eye_Retinal Object model.
Key features:
Retinal surface = object
External optics form an image of the fundus
Useful for analyzing:
Retinal image quality
Field coverage
Magnification and distortion
2. Retina as the Image (Eye Looking Out)
In applications such as:
- Spectacle lenses
- Head-mounted displays
- Visual instruments
The eye is looking out through an optical system, and the retina becomes the image surface.
Key features:
Retina = image plane
External optics form an image on the retina
Useful for:
Visual performance evaluation
Aberration analysis
MTF and field quality assessment
Accommodated Eye Model (250 mm Focus)
Also included is a model of an eye accommodated to 250 mm, corresponding to:
- 4 diopters of accommodation
- Referred to the cornea
This model is useful for:
- Near-vision system analysis
- Reading optics
- Instrumentation designed for close working distances
Non-Sequential Eye Models
Non-sequential models are preferred when:
- Light enters the eye from multiple paths
- Scattering, reflections, and efficiency matter
- Illumination uniformity must be evaluated
These models are especially useful for ophthalmic instruments that deliver light into the eye.
This model uses F, d, and C equally weighted wavelengths and a 6mm diameter stop to represent a moderately dilated pupil. The default retinal detector subtends about 50 degrees edge to edge at the pupil for wide field illumination of the fundus.
Choosing the Right Eye Model
There are many valid eye models because optical questions differ.
Use simple models when:
- You need fast insight
- First-order behavior is sufficient
Use more complex models when:
- Illumination efficiency matters
- Wide-field effects dominate
- Stray light or safety is critical
In practice, a simple model often provides answers just as valid as a more complex one, with far less computational effort.
Key Takeaways
- Eye models depend on application, not correctness
- Sequential models are ideal for imaging performance
- Non-sequential models are essential for illumination analysis
- Retina can be either an object or an image
- Accommodation state matters for near-vision modeling
- Simpler models are often sufficient
Human eye modeling is a tool, not a goal—choose the model that best answers your design question.