[Physiologic principles of studying visual functions]. / Physiologische Grundlagen der Untersuchung visueller Funktionen.

The retinal coding system for visual information comprises three important steps: 1) hyper- and depolarization of the sensory cells as the active basis for perception of light and dark; 2) reaction solely to changes in the bipolar cell on/off system, as a consequence of the action of the horizontal cells with the receptive fields, as a basis for adaptation to brightness and glare; and 3), under the influence of the amacrine cells, important time-space functions as a basis for visual perception of movement. The signal form, which changes over from analog to digital in the ganglion cell system, also results from this last step. therefore, both latencies and amplitudes (VEP) are important criteria for long signal response paths. Taking the examples of "statistical perimetry", visual acuity testing, and examination of contrast sensitivity, clinically relevant methodological problems from signal detection theory are illustrated: there are no "certain" measured values. This uncertainty and the age-dependence of normal values make it difficult to identify pathologic conditions, though trend analyses can help. As the sizes of the retinal areas examined by these methods differ so widely, correlations between the various examination methods are theoretically possible; but one method can never be substituted by another. In routine practice, to detect pathology early, one will sometimes deviate from the prescribed examination method (vision tests with low contrast for visual acuity).

[Haemodynamics in retinal branch vein obstruction (author's transl)]. / Zur Hämodynamik der retinalen Venenastthrombose (Eine fluoreszenzangiographische Studie).

A branch vein obstruction in a 44-years-old woman recovered with in 7 months without any clinical residuals. The evaluation of fluorescein angiograms performed during thrombosis and after recovery showed significantly reduced retinal circulation times in around the thrombosis. The results indicate an increased blood flow ranging between 50 and 200% around the obstructed area of the retina. The haemodynamic situation of the retinal circulation during branch vein obstruction and its therapeutic consequences (photocoagulation) are discussed.

[Th clinical picture of retinal thrombosis (author's transl)]. / Die retinalen Thrombosen das klinische Bild

Besides the acute arterial occlusion and simple venous thrombosis, the clinical symptomatology may include signs of chronic arterial insufficiency, i.e. progressive blurring of vision, absolute visual field defects, cotton wool exudates, capillary occlusion and increased retinal circulation time. The poor visual prognosis is caused by progressive macular degeneration. In the case of acute arterial thrombosis, fragmentation of the blood column and absence of arterial pulsation are indicative of pronounced retinal ischemia. The ophthalmoscopic aspect of a visible embolus may be a hint for the prognosis of eventual recanalisation.

Visible changes of the lens with age.

Slit lamp photographs taken along the optical axis of human eyes were examined with a microdensitometer. This showed an increasing opacity in the lens nucleus, an increased opacity and thickness of the cortex and the anterior lens capsule with age. However, the opacity and width of the anterior disjunction zones decreases with age. Patients with clear lenses but who had chronic uveitis, retinal detachment and glaucoma treated with medication, showed large deviations in the behavior of the disjunction zone as compared with other lenses of the same age. In incipient cataract in the aged, the fogging in the lens cortex is greatest when vestiges of the disjunction zone still remain. The cortex is less affected if the disfunction zone is absent.

[Planimetric evaluation of kinetic perimetry with the Goldman perimeter (author's transl)]. / Zur Bedeutung der planimetrischen Evaluation der kinetishcen Perimetrie mit dem Goldmann-Perimeter.

Kinetic perimetry was performed on 12 normal subjects. The perimetric results obtained with a Goldmann perimeter by 12 different investigators were statistically analyzed. Planimetry of areas outlined by a given isopter was done in order to reduce the amount of data. This led to a reduction in standard deviations of almost 50 percent. The statistical significance of field changes depends on individual variation and frequency of testing. If standard deviations are calculated in dB, variation becomes independent of given isopters. However, standard deviation may be increased by a factor of almost 2 as a result of the influence, of the investigator. Therefore, a standardization of test procedures by automatization seems meaningful, although standard deviations will not necessarily be lower with computerized perimetric methods.

[The hemodynamics of the uveal and retinal circulation and its clinical diagnosis (author's transl)]. / Hämodynamik des uvealen und des retinalen Kreislaufs und die diagnostischen Möglichkeiten.

Diagnosis and therapy of retinal and uveal circulatory disorders should be based mainly on two pathophysiologic principles: (1) an autoregulation is effective in the retinal circulation only but absent in the choroidal circulation and (2) circulatory disorders may be caused not only be a reduced but also by an increased blood flow. The clinical evaluation of an individual retinal circulatory disorder depends on the interpretation of the dynamics of visual disturbances, detection of vascular type or fiber bundle defects in the visual field, repeated estimation of blood flow velocity by direct ophthalmoscopy or fluorescence angiography, and detection of specific fundus signs such as focal ischemia (cotton wool spots) or development of a collateral circulation and true neovascularization. For the indirect assessment of disturbances of the choroidal circulation certain subjective symptoms, alterations of the pigment epithelium, and edema and focal defects of the choriocapillaries are of importance. The stereobiomicroscopy of the fundus with a slitlamp and fluorescence angiographic studies of the sectorial distribution of the choroidal filling are valuable diagnostic aids.

[Reproducibility of perimetric study results]. / Die Reproduzierbarkeit perimetrischer Untersuchungsergebnisse.

Theoretical and experimental aspects of the reproducibility of visual fields in static automated perimetry are described. Special emphasis was placed on factors which could potentially influence reproducibility, such as cooperation, the patient's age and the size of his/her pupils, learning and fatigue effects, the depth of scotomas and the influence of drugs.

[Quantification of senile cataract in split-lamp images of the Zeiss SLC measurement system]. / Quantifizierung der senilen Katarakt im Spaltlampenbild des Zeiss SLC Messsystems.

The Zeiss SLC measuring system for examining the anterior segment in slit light permits direct digital image storage and analysis. For long-term studies the reproducibility of individual images can be improved. Furthermore, the data can be quickly processed to yield indices which can be used to characterize the cataract: 1) the integral of an axial densitogram as a criterion of average lens opacity, and 2) the difference between the linear regressions of the densitograms of the anterior and posterior lens halves as a criterion of cataract form (e.g., nuclear vs. cortical cataract).

Quantification of choroidal blood-flow parameters using indocyanine green video-fluorescence angiography and statistical picture analysis.

A method for indocyanine green video-fluorescence angiography of the human choroid is described using a 30 degrees fundus camera (C. Zeiss) with external light supply, a low-light-level TV camera, and a video recorder. Bloodflow parameters for the choroid were obtained from the video recording using a picture-analysis system (IBAS, Kontron). These included: the mean time for arterial, capillary and venous filling and a parameter corresponding to the amount of perfused capillaries in the choroid. Angiograms were performed on normal, healthy subjects at normal and increased intraocular pressures and on patients with dry senile macular degeneration. Examples of the results are shown and discussed.

[The disjunction zone in the slit-image-photograph of the human lens in eye diseases (author's transl)]. / Der Abspaltungsstreifen in der Spaltlampenphotographie der Linse bei Augenerkrankungen

Standardised slit-image-photographs of the clear human lens in 78 eyes with wide angle glaucoma, 29 eyes with uveitis and 35 eyes after an operation of a retinal detachment were evaluated by microdensitometry and compared with clear lenses of 178 eyes without eye diseases. Most significant alterations were observed in the anterior disjunction zone. Its thickness was increased in all these diseases with the exception of the glaucoma eyes treated with derivates of phenylephrine and/or cholinesteraseinhibitors. Under these conditions the disjunction zone disappeared. The alterations of the lens cortex and of the nucleus of the lens with respect to the thickness and its density were mostly accelerations of the normal aging process and only glaucoma eyes were partly in contrast to this process. Thickening of the anterior disjunction zone may be combined with a thickening of the whole lens and vice versa.

Correlations between intraocular pressure, visual field and visual acuity, based on 11 years of observations of treated chronic glaucomas.

In a retrospective study of 114 patients under treatment for chronic glaucoma (81 without and 33 with visual field defect) over an 11-year period of observation, a highly significant correlation between intraocular pressure and progression of visual field defects could be demonstrated. This correlation could be shown for the visual field outer boundary in 81 eyes with ocular hypertension and for typical visual field defects in 33 eyes with chronic glaucoma. The relationship was, however, only significant when both the standard deviation of the annual intraocular pressure and the influence of cataract development upon visual acuity were considered. Quantitative analysis of the results of Goldmann perimetry was by planimetry and took into account only changes during the 11-year observation period.

[The Pola-test in asthenopia (author's transl)]. / Der POla-Test bei asthenopischen Beschwerden. Ein Versuch zur Indikationsstellung für eine Behandlung.

Seventy-three patients with asthenopia and 43 control subjects were examined with the Pola-Test. The two populations showed a significantly different frequency of pathologic results on the four test patterns. The so-called "stereo test" seems to be the most important test pattern. Patients with a pathologic stereo pattern reported asthenopic symptoms significantly more frequently than the control subjects who were questioned for similar symptoms. However, since 30% of the asthenopic patients showed normal results on the four Pola-Test patterns, the indication for treatment can be based only on a combined evaluation of binocular tests and asthenopic symptoms. In asthenopia visual and conjunctival symptoms are more prominent than headache. At times they may be masked by psychogenic factors. In a double-blind study on 12 asthenopic patients symptoms improved significantly during treatment with prisms.

Influence of intraocular lenses on ultrasound axial length measurement: in vitro and in vivo studies.

Refraction affects ultrasound as it passes obliquely through tissues or materials with different propagation speeds. Therefore, axial length measurements could theoretically be affected after implantation of an intraocular lens which has a propagation speed that exceeds those of the ocular humors by a factor of 1.8 (2718 m X s-1 vs. 1532 m X s-1). The in vitro studies we report clearly demonstrate that ultrasound axial length measurements were not affected significantly by inclining the IOL up to 25 degrees or varying the transducer-lens distance from 0 to 25 mm. However, length measurements were found to be directly proportional to the lens power. A 27-diopter lens induced a 0.032-mm increase in the apparent axial length for a lens-reflector plate distance of 20 mm (P less than 0.05). In vivo the retina's curvature counterbalances this apparent increase: axial lengths measured in 26 patients were virtually the same after IOL implantation. From these data we conclude that axial lengths can be accurately measured by ultrasound after IOL implantation if the different propagation speeds are considered for calculation.