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Development of equipment for the determination of ocular aberrations using wave-front measurements by way of the Harmann-Shack Technique

Grant number: 00/06810-4
Support type:Research Grants - Innovative Research in Small Business - PIPE
Duration: November 01, 2000 - December 31, 2004
Field of knowledge:Engineering - Biomedical Engineering
Principal Investigator:Jarbas Caiado de Castro Neto
Grantee:Jarbas Caiado de Castro Neto
Company:Eyetec Equipamentos Oftalmicos Indústria, Comércio Importação e Exportação Ltda. - EPP
City: São Carlos


The objective of this project is to develop a computerized instrument for the precise measurement of ocular aberrations and associated refractive defects (astigmatism, myopia and hypermetropia). The more traditional method for refractive examinations is based on the use of various test lenses, the degrees of which vary by intervals of 0.25 diopters. This is a subjective test which leaves the patient to choose the best lens. The examination is carried out with optotypes situated a certain distance from the patient. This technique even today shows itself to be problematic when being used under certain circumstances and for certain patients. A few years ago, so-called auto refractors were developed and made available on the instrumental market. The basic objective was to eliminate the subjective element associated with previous methods. These instruments normally measure the ametropias, projecting discrete light points onto the retina. Through analysis of the reflection of these points the best corrective lens could be calculated. These techniques of conventional refractometry, nonetheless, offer no diagnosis, and therefore no treatment for irregular features of the refractory defect. The point to point refractory map generated by a front wave analyzer collects real data from the refractometer, without simplifying it through “regular” lenses (spherical, cylindrical or toric). Consequently, the information obtained is the most complete. Since the advent of refractive surgery by excimer laser, a new field of medicine has been opened up, in which the correction of the optical defects of the ocular system can be carried out in a parametricized manner for each eye. In this way, the correction of the refractory defects with excimer laser could include the correction of optical aberrations present in the “normal” eye. Another application for the precise diagnosis of the defects of refraction is the creation of irregular corrective lenses beginning with LCD or of deformative reflector mirrors. Such applications could permit the examination of intra-ocular structures by means of specific pieces of apparatus with microscopic resolution. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
LUIS ALBERTO CARVALHO; ANTONIO CARLOS ROMAO; MARCOS STEFANI; LUIZ ANTONIO CARVALHO; JARBAS CAIADO DE CASTRO; FÁTIMA YASUOKA; FRANCISCO SCANNAVINO JÚNIOR; JUSELINO DOS SANTOS; PAULO SCHOR; WALLACE CHAMON. Preliminary results of a high-resolution refractometer using the Hartmann-Shack wave-front sensor: part I. Arquivos Brasileiros de Oftalmologia, v. 66, n. 3, p. 261-268, Jun. 2003.
L. ALBERTO V. CARVALHO; J.C. CASTRO; L. ANTONIO V. CARVALHO. Measuring higher order optical aberrations of the human eye: techniques and applications. Brazilian Journal of Medical and Biological Research, v. 35, n. 11, p. 1395-1406, Nov. 2002.

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