The power of an intraocular lens can be calculated before surgery to make the eye emmetropic or ametropic. The physiological mechanism of accommodation however, cannot be restored with an inelastic lens. An increased depth of focus in the implanted eye can be predicted through optical principles alone, if the postoperative ametropia of the implanted eye is a simple myopic astigmatism. This increased depth of focus without accommodation was tested in artificial ametropia and found to be used in nature by the seal. To increase the precision of intraocular lens calculation the average change in corneal power induced at surgery is used to predict the postoperative corneal power. By controlled suture release in the postoperative phase, the amount of induced corneal astigmatism is adjusted to obtain a simple myopic astigmatism. Patients with an intraocular lens and a simple myopic astigmatism as a residual ametropia, are spectacle independent most of the time. They need their glasses only for driving or prolonged reading. The methods used to calculate the postoperative cornea, the postoperative anterior chamber depth and the intraocular lens are described with the corresponding calculator programs for the HP 41C calculator. Clinical results and measurements of the depth of focus are shown in a series of 50 successive implant cases.

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Under stimulation with pattern reversal the visual-evoked potentials in glaucoma patients are shown to be delayed compared to a group of normals. This latency increase is due neither to age nor reduction in visual acuity. The glaucomatous lesion in the optic nerve can in some cases be demonstrated in the absence of visual field defect. The electrophysiological delays are similar to those measured in mild cases of neuritis in multiple sclerosis.

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The error in prediction of emmetropic intraocular lens power or postoperative refractive error after lens implantation was analyzed in three groups of eyes after posterior chamber lens implantation. Regression line calculation with the SRK equation or with a group-specific regression was compared with theoretical calculations in unselected, long myopic and short hyperopic eyes. The cut-off length was below 22.0 mm for the short eyes and above 25.9 mm for the long eyes. In the unselected and hyperopic group, there was only a small difference in mean error and error variance when the three calculation methods were compared. In the high myopic group, the range of error increased in all methods. The worst results were obtained with the standard SRK equation because the slope of the regression line in myopic eyes differs from the classical regression line calculated on an average population of implants. Lens calculation in high myopic eyes should therefore be performed with a specific regression line or by theoretical calculation.