Mario Angi

Inheritance of Astigmatism: Evidence for a Major Autosomal Dominant Locus

Although astigmatism is a frequent refractive error, its mode of inheritance remains uncertain. Complex segregation analysis was performed, by the POINTER and COMDS programs, with data from a geographically well-defined sample of 125 nuclear families of individuals affected by astigmatism. POINTER could not distinguish between alternative genetic models, and only the hypothesis of no familial transmission could be rejected. After inclusion of the severity parameter, COMDS results defined a genetic model for corneal astigmatism and provided evidence for single-major-locus inheritance. These results suggest that genetic linkage studies could be implemented and that they should be limited to multiplex families with severely affected individuals.

Heritability of myopic refractive errors in identical and fraternal twins.

The existence of a visual feedback control of eye growth in humans is controversal, 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 eye-loplegic 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.

Results of photorefractometric screening for amblyogenic defects in children aged 20 months

This report evaluates the validity of a preventive programme in a population which underwent refractometric screening at the ages of 20 months and 4 years. In 1987, 1,046 children born in 1985 in the territory of the Veneto National Health Unit No. 19 were invited to undergo screening for amblyogenic factors such as meridional hyperopia greater than or equal to +2.50 diopters (D), myopia less than or equal to -2.50 D, anisometropia greater than or equal to 2 D, opacity of the dioptric media and strabismus. The test method was non-cycloplegic photorefractometry (PhR). Seven hundred and ninety-five children were tested (76%); positive cases underwent subsequent cycloplegic autorefractometry (AR) and corrective lenses were prescribed as necessary. In 1989, an eye test was performed on 653 children who had taken part in the previous PhR screening and on 350 similar children who had not: the test included evaluation of visual acuity, stereopsis and AR. An eye with a corrected visual acuity of less than 0.7 was considered amblyopic. PhR demonstrated a sensitivity of 80%, a specificity of 96% and a positive prediction rating of 46% in the identification of amblyogenic factors. The prevalence of amblyopia at 4 years of age in the group which had undergone previous screening was 1.07% vs. 2.57% in the group which had not (P: not significant). The progress of the myopia was studied in a group with full optical correction used continuously (Group A) and in a control group under-corrected by at least 1.5 D (Group B).(ABSTRACT TRUNCATED AT 250 WORDS)

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 (TO) 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 TO, 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 testP<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 ≥ 0.75 D with respect to refractometric values and/or were worn part-time). When the spherical cycloplegic values at TO 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.

Changes in myopia, visual acuity, and psychological distress after biofeedback visual training

The effects of auditory biofeedback training on myopia, visual acuity (VA), and psychological distress were evaluated in a controlled prospective study involving 55 mildly myopic (≤-3.5 D) high school students. These myopes were divided into 2 groups, matched for age and dioptric defect: 33 were treated with visual training and 22 were not; 27 emmetropic subjects formed a further control group. Subjects were evaluated at the baseline (TO), at 10 weeks after the end of the treatment (T1), and after an interval of 12 months (T2) from the baseline for: (1) manifest and cycloplegic refraction, and the difference between them (cycloplegic tonus); (2) VA measured with a conventional optotype in all subjects, and also with a computer-generated optotype in the treated group; and (3) psychometric values and personality profile. At T2, myopia had significantly worsened both in the treated and in the control myopes; VA in the treated myopes appeared significantly improved when measured by the conventional optotype, but unchanged when measured by computer. Psychometric scores improved significantly in the treated myopes and in the emmetropic controls. Objectively the autorefractometer showed that 38% of the myopes had voluntary control of positive accommodation, i.e., the ability to increase spherical defect; no voluntary control of negative accommodation was observed. An increase in VA was associated with a significant increase in the foveation time (i.e., the period of time when the target is imaged on the fovea and the eye is motionless), and was partly attributable to a learning effect. In conclusion, biofeedback visual training had a positive effect on psychological distress and subjective VA improvement, but failed to reduce the existing myopia or delay its evolution.

Visuospatial attention in myopia

Four experiments were conducted to ascertain whether myopia is associated with deficits of visuospatial attention. In myopic and emmetropic control subjects, we studied: (1) automatic and voluntary orienting of attention, (2) focusing of attention and (3) performance on a visual search task. The results indicated that automatic orienting was defective in myopics and their performance in visual search was less efficient than that of controls. By contrast, myopics showed no deficits in voluntary orienting and in focusing.

PowerRefractor versus Canon R-50 Autorefraction to assess refractive error in children: a community-based study in ecuador.

Purpose. To compare the agreement of the PowerRefractor with Canon R-50 autorefraction for measuring refractive error in a community of Ecuadorian children. Methods. We examined 1564 children aged 5 to 6 years from two ethnically and geographically similar regions of the Ecuadorian highlands. Results of a refraction obtained without cycloplegia with the PowerRefractor and with the Canon R-50 autorefractor (NCAR) were compared with the gold-standard examination, cycloplegic autorefraction (CAR) with the Canon R-50 autorefractor. Power vectors were used to analyze refractive error. Bland-Altman limits of agreement were obtained. Results. Although the mean difference in the spherical equivalent refractive error between the PowerRefractor and CAR was small (−0.03 D ± 0.05 D), the 95% limits of agreement were wide (±2.03 D). On the other hand, NCAR showed a greater bias (0.97 D ± 0.04 D) and smaller limits of agreement (±1.49 D). The limits of agreement of the PowerRefractor were also wider than NCAR for measuring astigmatism. When the mean difference was stratified by the subgroups of refractive error vectors, the PowerRefractor was found to have poorer limits of agreement than NCAR for hyperopic defects. Conclusion. The PowerRefractor is accurate, but not as precise for measuring refractive error as compared to the Canon R-50 autorefractor, especially for high hyperopia.