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Measuring Refractive State in Alert Animals

Photorefractor

The infrared eccentric Photorefractor was originally developed by Prof. Frank Schaeffel at the University of Tübingen (Germany), and is being used by numerous labs world-wide. Based on the analysis of retinal reflection of an eccentrically placed IR light field, the Photorefractor automatically and conveniently measures the eye's refracative state in alert small laboratory animals.

The Photorefractor is a practical, fast, automated, and objective instrument for measuring the refractive state of the eyes in small alert laboratory animals. The main field of application of this survey method is myopia research.

Myopia Research


  • Mechanisms of eye growth
  • Interaction between myopia and other diseases
  • Influence of external stimuli on the development of myopia
  • Pharmacology of myopia prevention
Measuring Refractive State

Background: Myopia, Eye Growth, and the Refractive State

In myopia, the image is focused in front of the retina.

Myopia, also known as short-sightedness, or near-sightedness, is a common disease where close obejcts can still be seen clearly, but distant objects appear blurry. In myopia, the eye is too long, and the optics of the eye focuses the image in front of the retina. High myopia can be dangerous, because the retina can detach due to the long eye ball, and is a leading cause of blindness. The degree or severity of myopia can be described as the refractive state of the eye.

The refactive state can be measured with an eccentric Photorefractor. The fundus is observed through the pupil while an eccentrically placed light source illuminates the eye. The pupil reflects the light source back to the observer (e.g., a camera), similar to the red-eye effect known from photography. Depending on the amount of defocus, this reflection is not filling the pupil evenly, but it is displaced laterally. The asymmetry of the reflection is directly correllated with the strength of the refractive error.

Striatech's Photorefractor is designed to measure the refractive state in alert small laboratory animals. It is fully integrated (camera, light source, and provided analysis software) to obtain results quickly and automatically, even in alert and moving animals. Building upon the successful approach and design of Prof. Frank Schaeffel (University of Tübingen, Germany), it can be used with all common small animal models of myopia research: mice, rats, Guinea pigs, and chicken.

Photorefractor vs. Keratometer: Both methods are indirect measurements to monitor eye growth. The Keratometer measures the radius of the corneal curvature, but all changes between the ocular surface and the retina remain unknown. The Photorefractor measures the refractive state, but cannot reveal the contribution of the corneal curvature.

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Photorefractor vs. Keratometer: Both methods are indirect measurements to monitor eye growth. The Keratometer measures the radius of the corneal curvature, but all changes between the ocular surface and the retina remain unknown. The Photorefractor measures the refractive state, but cannot reveal the contribution of the corneal curvature.

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