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. 1999 Apr;83(4):495–500. doi: 10.1136/bjo.83.4.495

Head mounted video magnification devices for low vision rehabilitation: a comparison with existing technology

R HARPER 1, L CULHAM 1, C DICKINSON 1
PMCID: PMC1723014  PMID: 10434876

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Figure 1  .

Figure 1  

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Schematic diagram of the LVIS. A magnified intermediate image of each cathode ray tube (CRT) screen is formed by an aspheric triplet lens system. Light from the temple arm CRT is directed by the folding mirrors to the 50/50 beam splitter in front of the eye. The curved mirror images the exit pupil of the optical system in the plane of the subject's pupil and displays a 50° × 40° image of the CRT screen. A refractive correction, if necessary, can be inserted between the CRT and the aspheric triplet (redrawn after Massof et al 15).

Figure 2  .

Figure 2  

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Photograph of the LVIS. The two monochrome charge coupled device cameras mounted in front of the eyes provide an unmagnified binocular field of view for orientation and the third centre mounted zoom camera provides variable magnification. The control unit can be worn as a "belt pack" and consists of a series of switches (for example, to enhance contrast, change contrast polarity, or "toggle" between orientation and zoom cameras). The function of the switches must be learnt, since these cannot be seen when the unit is worn.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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