A system has been developed to measure spherocylindrical spectacle lenses. The global pandemic limited access to regular eye exams. The system bypasses this limitation by providing at-home prescription measurements. The power and orientation of the spectacle lenses are obtained with a cell phone camera, a displayed or printed target, and a magnetic stripe card. The spatially varying magnification of the lenses is calculated by examining the image captured through the lens of the target at a fixed distance. This information is then used to calculate a clinical prescription, i.e., Sph/Cyl × Axis. The system is tested with 48 single-power spherocylindrical lenses with a range of −11.25 to +4.25 D for Sph, −5.25 to −0.25 D for Cyl, and a whole range of Axis. The results are plotted in comparison with these reference prescriptions provided by a commercially available lensmeter and show good agreement. The image processing and clinical prescription calculation are discussed here.
The SpectRx system has been developed to measure sphero-cylindrical spectacle lens power as an alternative to clinical lensmeters. This work was inspired by the ongoing global pandemic, which limited physical access to eye care facilities for regular eye exams. The SpectRx system aims to bypass this limitation by providing at-home prescription measurements. The power and orientation of the spectacle lenses are obtained by the use of readily available objects such as a cell phone camera, a displayed or printed target, and a fixed-dimension magnetic stripe card. The magnification of the lenses can be calculated by examining the image captured through the lens of the target at a fixed distance. The magnification may be spatially varying due to the cylinder component of the lens. Processing the pictures captured with a cell phone camera is done automatically with standard image processing algorithms. The processed images, in turn, are used to calculate a clinical prescription, i.e., Sph/Cyl×Axis. The SpectRx may expand access to quality eye care in not only the current pandemic situation but also in locations where eye care may not be easily accessible, such as some rural or remote areas. The image processing and clinical prescription calculation are discussed here.
A system for measuring the orientation and power of sphero-cylindrical lenses has been developed. The system attempts to minimize the need for specialized equipment and training and instead relies on the ubiquitous cell phone camera, a magnetic stripe card, and a target pattern. By capturing an image of the target through the lenses under test and analyzing the distortion in the resulting image, the orientation and powers on sphero-cylindrical lenses can be determined. In modern eye clinics, the measurement of sphero-cylindrical spectacle lenses is readily measured with a lensmeter. However, there are many examples where this measurement is not feasible. This may include remote or rural locations where access to eye care may not exist, or require impractical travel. Furthermore, the on-going global pandemic has often put restrictions on contact between the patient and the eye care provider. Telemedicine, which can connect patients to eye care providers, lacks physical access to the spectacles for measurement. The system developed in this effort overcomes this limitation by allowing remote measurement of the lenses with items found in most households. Such a system would be beneficial to often underserved populations and expand access to quality eye care.
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