RESUMO
The article reviews some of the basic optics of astigmatism and the correction of astigmatism with cylindric lenses. A simple model of the conoid of Sturm is demonstrated, and an ideal position for the conoid is postulated. The orientation of the conoid shows that leaving patients with some simple myopic "against-the-rule" astigmatism is beneficial to near work, whereas "with-the-rule" astigmatism is beneficial for distant viewing. Surgeons should be less aggressive with patients with with-the-rule and against-the-rule astigmatism and more aggressive with oblique astigmatism. The toric intraocular lens (IOL) should be positioned on axis or, if slightly off axis, err on the side away from the vertical or horizontal meridian so that the resultant cylinder is more vertical or horizontal. Clinically significant rotation of the toric IOL occurs in a few cases, but these can be easily rerotated. Rerotation should be done between the first and second weeks after primary implantation.
Assuntos
Astigmatismo/cirurgia , Implante de Lente Intraocular , Lentes Intraoculares , Óptica e Fotônica , Astigmatismo/complicações , Catarata/complicações , Extração de Catarata , Humanos , Desenho de PróteseRESUMO
An intraocular lens with a given cylindrical power will correct a variable amount of cylinder at the spectacle plane. This variability depends not only on the vertex distance but also on the degree of ametropia. The amount of spectacle cylinder corrected will be more for myopes and less for hyperopes. Anterior corneal cylinder (as determined by the keratometer) is a more reliable way of estimating the cylinder needed at the intraocular lens plane.
Assuntos
Astigmatismo/terapia , Lentes Intraoculares , Astigmatismo/fisiopatologia , Óculos , Humanos , Matemática , Pessoa de Meia-Idade , Óptica e Fotônica , Refração Ocular/fisiologiaRESUMO
After having a radial keratotomy, a physician developed binocular diplopia. The differential diagnosis and management of symptoms by appropriate spectacles is described.
