Heritability of myopic refractive errors in identical and fraternal twins.

The existence of a visual feedback control of eye growth in humans is controversial, as the contributions of genetic and environmental factors are still unknown. To evaluate the heritability of refractive defects, we measured ocular refraction in 19 monozygote and 20 dizygote twin pairs (mean age 5 years). Monozygosity was ascertained by a common chorion, similarity of somatic traits, and identical dermatogliphes and was confirmed in myopes by blood marker diagnosis. Ocular refractive defects and axial length were evaluated by cycloplegic autorefractometry and biometry. By comparing identical and fraternal twins heritability of refractive defects was estimated to be 0.08-0.14; this low value indicates that the observed variability in refractive errors is nongenetic in origin. Three monozygote pairs were anisomyopic; differences between eyes in identical twins were related to the increased axial length of myopic eyes. In one eye, myopia was attributed to visual deprivation induced by a congenital cataract, while in five eyes it was correlated directly to the degree of astigmatic defects. The discordant axial length observed in monozygote twins is nongenetic. In agreement with previous findings reported in the literature, it is proposed that visual impoverishment of retinal images may play an early regulatory role in postnatal eye growth.

The binocular videorefractoscope for visual screening in infancy.

Photorefraction is a promising technique for screening infants for amblyopiogenic defects, but currently used instruments often produce images that are difficult to interpret due to inaccurate control of the subject's fixation, to the narrow range (+/- 4 D) of the measurable error, to ill-defined crescent borders, and to chromatic aberration. A charge-coupled device (CCD) camera with near-infrared sensitivity connected to a computer with an image grabber for real-time equalization was devised to overcome the aforementioned problems. This binocular videorefractoscope (VRB) enables a dynamic and nondissociating refractive status and an ocular motility testing. Fixation and accommodative response are observed on-line and the strabismic angle is measured off-line. Arrays of infrared-emitting diodes with a variable eccentricity and position reveal sphere and/or cylinder errors (+/- 10 D; null interval, +0.00 to -2 in an 8-mm pupil diameter) as well as squint (> 5 prism diopters) and dioptric media opacities. The VRB was tested during noncycloplegic screening for amblyopiogenic defects in 212 3-year-old children. The findings were compared with the results of manifest and cycloplegic autorefractometry in a blind study. The VRB revealed a sensitivity of 81% and a specificity of 97%. In conclusion, the VRB can give a fast, noninvasive, and reliable evaluation of amblyopiogenic factors in infants.

Personality, psychophysical stress and myopia progression. A prospective study on 57 university students.

Personality profile, psychophysical stress and cycloplegic refraction were evaluated at the baseline (T0) and after 12 months (T1) in 57 university students comprising 39 myopes and 18 emmetropes/hyperopes (controls) whose age, sex distribution and academic results were comparable. At T0, a tendency toward a higher degree of anxiety, somatization and inadequacy was found in myopes in comparison with controls; however, only the anxiety state was different (Wilcoxon signed-rank test P < 0.001). Personality profiles, psychophysical stress and blood levels of cortisol, ACTH, GH, prolactin were similar in myopes and controls. The myopes were classified at T1 as either well-corrected (if their lenses corresponded to refractometer values of +/- 0.50 D and were worn full-time) or undercorrected (if their lenses were > or = 0.75 D with respect to refractometric values and/or were worn part-time). When the spherical cycloplegic values at T0 and T1 were compared, a myopic shift was revealed only in the undercorrected myopes (P < 0.001 in both eyes). These findings suggest that personality profile and psychophysical stress do not play a primary pathogenetic role in myopia. Undercorrection seems to accelerate the progression of myopia.

The clinical significance of the reduced capillary resistance factor in the diabetic patient.

A statistical survey in a group of 235 subjects (174 diabetic patients and 61 nondiabetic control subjects) was conducted to evaluate the incidence of reduced capillary resistance factor in respect to diabetic disease, to its duration, and to the severity of retinopathy. To evaluate the capillary resistance we used a cupping-glass method (Parrot's angiosterrometer test). The incidence of reduced capillary resistance proved to increase in frequency with diabetes, with its duration, and with the severity of retinopathy. Thus, reduced capillary resistance represents a negative prognostic element for retinopathy.

[Fluorescein fundus angiography of the iris (author's transl)]. / Rückwärtige Fluoreszenzangiographie der Iris.

A special method of examining hemodynamic and hydrodynamic conditions of the iris and the ciliary body is described. The process is based on the injection of fluorescein solution into the vortex vein of a rabbit.

[Paradoxical effect of buphenine on intraocular pressure in aphakic eyes (author's transl)]. / Die paradoxe Wirkung von Buphenin auf den intraokularen Druck in aphaken Augen.

The effect of topical administration of Buphenine was studied in a group of aphakic patients (53 eyes). The action of the drug was paradoxical: it induced an increase, often remarkable, in intraocular pressure in more than 70% of the eyes thus treated. The cause of the elevated IOP is discussed.