Biomedical subjects
R D Binkhorst
Publications and source records attributed to R D Binkhorst.
The accuracy of ultrasonic measurement of the axial length of the eye.
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The cause of excessive astigmatism with intraocular lens implants.
Higher degrees of astigmatism are found after intraocular lens implantation than after routine cataract surgery. The cause is optical and is associated with the effectivity of lenses. The same amount of corneal astigmatism requires, in the spectacle correction, a cylinder that is smaller than, equal to, or larger than the corneal astigmatism, depending on whether the spherical equivalent of the refraction is a plus, zero, or minus sphere.
Intraocular lens power calculation.
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Pitfalls in the determination of intraocular lens power without ultrasound.
The rule is simple: An 18 diopter intraocular lens tends to restore the basic refraction. For each diopter of basic refraction to be corrected add or subtract 1.25 diopters. To determine the basic refraction a careful history and an examination of old glasses and past refraction records is necessary. When the basic refraction cannot be ascertained, capital errors may occur. Given the basic refraction, errors or several diopters are still apt to occur. Calculation of intraocular lens power based on K-readings and ultrasonic measurements is therefore always advisable and a must when there is doubt about the basic refraction.
The optical design of intraocular lens implants.
Intraocular lens implants have been around for more than 25 years. On the verge of a major breakthrough to ever widening popularity, there is, however, a general lack of understanding of the pertinent optical principles. A critical comparison is made between this new method and conventional methods of correcting aphakia. From this it appears that the visual needs of the patient are a decisive factor in the selection of the method of correction. Moreover, the full potential of intraocular lens implants can only be realized by appropriate selection of the power of the implant in each situation. To this end, ultrasonic measurement of the ocular axial length is indispensable. The use of standard power lens implants is inadequate. Formulas are presented to make an eye emmetropic or to give it any refractive error. Guidelines are given for the use of these formulas. Two methods for obtaining equal image size in unilateral antiphakia are described.
The diagnosis of pupillary block by intravenous injection of fluorescein.
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Anterior Chamber Depth in Aphakia.
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