https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1475-1313.2005.00298.x

Myopia and associated pathological complications.

Low literacy is termed ‘developmental dyslexia’ when reading is significantly behind that expected from the intelligence quotient (IQ) in the presence of other symptoms —incoordination, left ‐right confusions, poor sequencing —that characterize it as a neurological syndrome. 5‐10% of children, particularly boys, are found to be dyslexic. Reading requires the acquisition of good orthographic skills for recognising the visual form of words which allows one to access their meaning directly. It also requires the development of good phonological skills for sounding out unfamiliar words using knowledge of letter sound conversion rules. In the dyslexic brain, temporoparietal language areas on the two sides are symmetrical without the normal left-sided advantage. Also brain ‘warts’ (ectopias) are found, particularly clustered round the left temporoparietal language areas. The visual magnocellular system is responsible for timing visual events when reading. It therefore signals any visual motion that occurs if unintended movements lead to images moving off the fovea (‘retinal slip’). These signals are then used to bring the eyes back on target. Thus, sensitivity to visual motion seems to help determine how well orthographic skill can develop in both good and bad readers. In dyslexics, the development of the visual magnocellular system is impaired: development of the magnocellular layers of the dyslexic lateral geniculate nucleus (LGN) is abnormal; their motion sensitivity is reduced; many dyslexics show unsteady binocular fixation; hence poor visual localization, particularly on the left side (left neglect). Dyslexics’ binocular instability and visual perceptual instability, therefore, can cause the letters they are trying to read to appear to move around and cross over each other. Hence, blanking one eye (monocular occlusion) can improve reading. Thus, good magnocellular function is essential for high motion sensitivity and stable binocular fixation, hence proper development of orthographic skills. Many dyslexics also have auditory:phonological problems. Distinguishing letter sounds

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The magnocellular theory of developmental dyslexia.

Choroidal and scleral mechanisms of compensation for spectacle lenses in chicks

Purpose The purpose of the Correction of Myopia Evaluation Trial (COMET) was to evaluate the effect of progressive addition lenses (PALs) compared with single vision lenses (SVLs) on the progression of juvenile-onset myopia. Methods COMET enrolled 469 children (ages 6-11 years) with myopia between -1.25 and -4.50 D spherical equivalent. The children were recruited at four colleges of optometry in the United States and were ethnically diverse. They were randomly assigned to receive either PALs with a +2.00 addition (n = 235) or SVLs (n = 234), the conventional spectacle treatment for myopia, and were followed for 3 years. The primary outcome measure was progression of myopia, as determined by autorefraction after cycloplegia with 2 drops of 1% tropicamide at each annual visit. The secondary outcome measure was change in axial length of the eyes, as assessed by A-scan ultrasonography. Child-based analyses (i.e., the mean of the two eyes) were used. Results were adjusted for important covariates, by using multiple linear regression. Results Of the 469 children (mean age at baseline, 9.3 +/- 1.3 years), 462 (98.5%) completed the 3-year visit. Mean (+/-SE) 3-year increases in myopia (spherical equivalent) were -1.28 +/- 0.06 D in the PAL group and -1.48 +/- 0.06 D in the SVL group. The 3-year difference in progression of 0.20 +/- 0.08 D between the two groups was statistically significant (P = 0.004). The treatment effect was observed primarily in the first year. The number of prescription changes differed significantly by treatment group only in the first year. At 6 months, 17% of the PAL group versus 30% of the SVL group needed a prescription change (P = 0.0007), and, at 1 year, 43% of the PAL group versus 59% of the SVL group required a prescription change (P = 0.002). Interaction analyses identified a significantly larger treatment effect of PALs in children with lower versus higher baseline accommodative response at near (P = 0.03) and with lower versus higher baseline myopia (P = 0.04). Mean (+/- SE) increases in the axial length of eyes of children in the PAL and SVL groups, respectively, were: 0.64 +/- 0.02 mm and 0.75 +/- 0.02 mm, with a statistically significant 3-year mean difference of 0.11 +/- 0.03 mm (P = 0.0002). Mean changes in axial length correlated with those in refractive error (r = 0.86 for PAL and 0.89 for SVL). Conclusions Use of PALs compared with SVLs slowed the progression of myopia in COMET children by a small, statistically significant amount only during the first year. The size of the treatment effect remained similar and significant for the next 2 years. The results provide some support for the COMET rationale-that is, a role for defocus in progression of myopia. The small magnitude of the effect does not warrant a change in clinical practice.

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A Randomized Clinical Trial of Progressive Addition Lenses versus Single Vision Lenses on the Progression of Myopia in Children

Cybersickness is an affliction common to users of virtual environments. Similar in symptoms to motion sickness, cybersickness can result in nausea, headaches, and dizziness. With these systems becoming readily available to the general public, reports of cybersickness have increased and there is a growing concern about the safety of these systems. This review presents the current state of research methods, theories, and known aspects associated with cybersickness. Current measurements of incidence of cybersickness are questionnaires, postural sway, and physiological state. Varying effects due to display and rendering modes, such as visual display type and stereoscopic or monoscopic rendering, are compared. The known and suspected application aspects that induce cybersickness are discussed. There are numerous potential contributing application design aspects, many of which have had limited study, but field of view and navigation are strongly correlated with cybersickness. The effect of visual displays is not well understood, and application design may be of greater importance.

Review on cybersickness in applications and visual displays

Patient records of young myopes were collected from three optometry practices. An index of the age at which increases of myopia in young people cease was derived using four different graphical and statistical methods. The results suggest that myopia stops increasing earlier in females than in males. There is, however, a great deal of individual variability in cessation age. Some implications for clinical practice and clinical research are discussed.

Progression of myopia in youth: age of cessation

Relatively few studies have reported on the repeatability of heterophoria (phoria) measurement procedures. The purpose of this study was to assess the inter-examiner repeatability of seven clinical tests of phoria measurement, using correlational and mean difference analyses. Two experienced optometrists performed each of the 7 phoria tests on 72 healthy adult subjects. Subjects ranged in age from 22 to 40 years, had visual acuity correctable to 20/20 in each eye, had no strabismus or amblyopia, and had normal eye health. The seven phoria tests used were: (1) the estimated cover test, (2) the prism-neutralized objective cover test, (3) the prism-neutralized cover test with subjective reporting of target movement, (4) the von Graefe phorometry with continuous target presentation, (5) the von Graefe phorometry with flashed target presentation, (6) the Thorington method, and (7) the modified Thorington method. All tests were performed in the same way by both examiners in random sequence, using standard clinical procedures. Inter-examiner correlations were determined for each test, as well as the mean and standard deviation of the differences between each examiner measurement (in prism diopters) on each subject. The modified Thorington method had the smallest mean difference and standard deviation of all tests and, thus, may be considered the most repeatable. This test also had the highest inter-examiner correlation. The prism-neutralized cover test with subjective reporting of target movement had the second highest correlation and the second lowest 95% limits of agreement, but had the largest mean difference of all tests, von Graefe phorometry methods were the least repeatable of the phoria tests.

Inter-examiner Repeatability of Heterophoria Tests

The purpose of this paper is to review the available evidence concerning the role of the cornea in achieving and maintaining emmetropia, as well as its role in the development and progression of myopia. The role of the cornea in emmetropization is most evident at the two extremes of life. During infancy, when the axial length increases rapidly, both the cornea and the lens become flatter, moving the refractive state of the eye toward emmetropia; during the later years of life, when the axial length remains constant or even shortens, the cornea appears to steepen somewhat. When myopia develops, in some cases the cornea may undergo a "paradoxical" steepening, which accelerates, rather than retards, the development of myopia. The effect of the cornea on the development and progression of myopia is evident when the ratio of axial length to corneal radius--the AL/CR ratio--is considered. Recent studies suggest that a high AL/CR ratio, which has a value of approximately 3.0 in the emmetropic eye, is a risk factor for youth-onset myopia. Several studies have shown that myopic eyes have greater mean corneal powers than emmetropic eyes; this may be mostly due to greater corneal powers being a risk factor for youth-onset myopia.

Role of the cornea in emmetropia and myopia.

Many methods of heterophoria measurement are available clinically. This paper reviews several studies which have examined the reliability of phoria measurements, and have compared various tests of phoria measurement. Different methods of data analysis make comparison of studies difficult. Two studies indicated 95% limits of agreement of 2 to 4 delta for reliability of modified Thorington, von Graefe, and Maddox rod phoria tests. Studies using correlational analysis to compare different measurement methods have found a high degree of association of the results of these methods. Studies using statistical methods assessing the agreement of test results found a high level of agreement among some tests and a low level of agreement among some tests. Some of the various phoria measurement methods differ in the technique used for dissociation, in the ability to control accommodation adequately, in the level of proximal convergence induced, or in the method by which the phoria is quantified. These differences can result in different phoria measurements on the same patient.

Reliability of and comparisons among methods of measuring dissociated phoria.

Longitudinal records obtained from three optometry practices in the central United States were used to assess the effect of bifocal lenses on the rate of childhood myopia progression. Rates in D/year were derived by linear regression for age spans between 6 and 15 years of age. Records were available for 52 persons who wore single vision lenses (SV group) during this entire age span, and 60 persons who wore bifocal lenses (BF group) during the complete period of observation. The mean rates of myopia progression were -0.44 D/year for the SV group, and -0.37 D/year for the BF group (difference not statistically significant). When rates were determined as a function of nearpoint phoria and near binocular cross cylinder net, the BF group had rates of myopia increase which were lower in magnitude than the SV group in children with nearpoint esophoria and of higher cross cylinder net.

David A. Goss

Papers

Progression of myopia in youth: age of cessation

Inter-examiner Repeatability of Heterophoria Tests

Role of the cornea in emmetropia and myopia.

Reliability of and comparisons among methods of measuring dissociated phoria.

Effect of bifocal lenses on the rate of childhood myopia progression.