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PubMed1999

Visual acuity after cycloplegia in children: implications for atropine penalization.

BACKGROUND: Atropinization of the sound eye is an alternative to patching in the treatment of amblyopia. Whether atropine treatment can induce a switch in fixation depends on the refractive error of the sound eye, visual acuity of the amblyopic eye, distance from the fixation target, and presence of any optical correction or penalization. General guidelines are needed on the basis of refractive error and visual acuity in the amblyopic eye to predict which patients may potentially benefit from atropine penalization. METHODS: Refractive error and visual acuity at distance (6 m) and/or at near (33 cm) were recorded in a normal eye of 126 consecutive children (mean age, 8.2 years), 30 to 60 minutes after receiving cyclopentolate 1%. Visual acuity was plotted versus refractive error at distance and at near, and best-fit curves were calculated. RESULTS: There was a consistent, reproducible relationship between refractive error and visual acuity after cycloplegia at both distance and near in healthy children. CONCLUSIONS: The results of this study can be used to quickly determine whether atropine penalization has the potential for success on the basis of a patient's visual acuity in the amblyopic eye and refractive error in the sound eye. When adequate hyperopia is present in the sound eye, one should consider testing for fixation preference or initiating a therapeutic trial of atropine. Those children with insufficient hyperopia in the sound eye relative to visual acuity in the amblyopic eye can be spared the time, expense, and potential side effects of atropine penalization.

Adolescent↗
PubMed2006

Long-term refractive change after intraocular lens implantation in childhood.

BACKGROUND: To determine refractive change occurring with age in children who had cataract removal with intraocular lens implantation and in whom the immediate postoperative refraction was targeted either to match the refractive error of the opposite eye in unilateral cases, or for only a small refractive error when surgery was bilateral. METHODS: Retrospective review of the refractive error over time in 36 eyes of 25 children who underwent cataract removal (11 bilateral) with insertion of an intraocular lens from 1987 to 1998 and who had at least 4 years follow-up, but no glaucoma. RESULTS: Mean age at surgery was 5.5 years (median 5.7 y, range 1.3-12 y), with a mean follow-up of 8 years (median 6 y, range 4-16 y). The average refraction followed a logarithmic decline with age. Although eyes with unilateral surgery had a slightly faster rate of change and lower final refraction than did eyes with bilateral surgery, this difference was not statistically significant. Variation from this trend was also observed in 3 patients. When the hyperopic refractive error created immediately after surgery was small, children usually became significantly myopic when older, often creating anisometropic myopia in unilateral cases. INTERPRETATION: When implanting intraocular lenses bilaterally one should aim for a significant but balanced hyperopic correction immediately postoperatively in young patients, anticipating that there will be emmetropization with aging. Parents should be warned that variations can occur.

Aging↗
PubMed2005

Patterns of spectacle use in young Australian school children: findings from a population-based study.

PURPOSE: To describe the patterns of spectacle use in a population-based sample of Australian Year 1 school children (mostly aged 6 years). METHODS: Logarithm of the minimum angle of resolution (logMAR) visual acuity was measured in both eyes before and after pinhole correction, and using spectacles if worn. Cycloplegic autorefraction (cyclopentolate) and detailed dilated fundus examination were performed. Visual impairment was defined as visual acuity <40 logMAR letters (ie, <20/40 Snellen equivalent). Myopia was defined as spherical equivalent (SE) refraction < or = -0.50 diopters (D), and hyperopia as SE refraction > or = +2.0D, deemed significant when > or = +3.0D. Astigmatism was defined as cylinder > or =1.0D and anisometropia as SE refraction difference between the two eyes at least 1.0D. RESULTS: One thousand seven hundred forty predominantly 6-year-old school children were examined during 2003 to 2004. Spectacle use was documented in 77 children (4.4% of sample). Uncorrected visual impairment was found in the worse eye of 71 children (4.1%) and refractive error accounted for the majority (69.0%). Astigmatism was the most common refractive error causing visual impairment, accounting for 46.5%. Hyperopia, with or without astigmatism, was the most frequent reason for spectacle use, documented in 40.3%. Spectacle use in the absence of significant refractive error, amblyogenic risk factors, or visual impairment was noted in 26 children (33.8% of spectacle wearers). The prescription of spectacles could have benefited a further 26 children (1.5% of sample), mostly for correction of astigmatism. CONCLUSION: This study documents a significant disparity between spectacle use and need. Astigmatism was the most common cause of visual impairment due to refractive error.

Child↗
PubMed2003

What are the visual benefits of eyelid squinting?

PURPOSE: We propose that eyelid squint can reduce the impact of several conditions known to cause eyestrain such as uncorrected refractive error, accommodative dysfunction, presbyopia, and glare. Clinicians commonly accept that squint improves visual acuity (VA) in the presence of refractive error, and even though the benefit of eyelid squint in bright light seems self-evident, data are not available to support either benefit. The purpose of this study was to measure the effect of eyelid squint on VA in the presence of refractive blur and on visual field sensitivity. METHODS: Nineteen subjects with optimal refractive correction were tested, with and without squinting, as follows: (1) distance VA with induced refractive errors of +0.50, +1.00, +2.00, +3.00, +1.00 -1.00 x 90, and +1.00 -1.00 x 180; (2) near VA with induced refractive errors of -1.00 x 90 and -1.00 x 180; and (3) central and peripheral threshold visual fields with a Humphrey Field Analyzer. Differences in visual acuity between squinting and nonsquinting were tested for significance with repeated-measures analysis of variance, and differences in visual fields were tested using mixed model analysis of variance with repeated measures. RESULTS: Eyelid squint significantly improved (p < 00.016) distance VA measurements for 1.00 to 3.00 D of induced myopia. The squint-induced VA improvement increased from 0.06 logarithm of the minimum angle of resolution for 1.00 D to 0.24 logarithm of the minimum angle of resolution for 3.00 D of myopia. Eyelid squint also significantly reduced visual field sensitivity below the horizontal meridian by an average of 1.4 dB, by 1.6 dB on the horizontal meridian, and with increasing reductions in the vertical field up to 11.6 dB for measurements 40 degrees above fixation. This pattern of decreased superior field sensitivity would decrease visual discomfort from overhead glare. CONCLUSIONS: The results provide empirical support that eyelid squint improves visual acuity for subjects with refractive error and reduces glare in the superior visual field.

Adult↗
PubMed2003

Clinical evaluation of an eccentric infrared photorefractor: the PowerRefractor.

PURPOSE: To evaluate the viability of the PowerRefractor as a screening tool for examining refractive errors in large samples of children. METHODS: The variability of the PowerRefractor was estimated using four patients. The refractive error was determined using cyclopentolate and tropicamide as cycloplegic agents and compared to that determined in a non-cycloplegic situation. In a second study, the data provided by the PowerRefractor were compared to results obtained by autorefractor or retinoscopy for 150 children aged from 6 months to 5 years. RESULTS: Variability study. Statistical analysis showed a statistically significant difference between cycloplegic and non-cycloplegic refraction for spherical and cylindrical refractive errors (p<0.0001 in all cases). There was no significant difference between the measurements made using tropicamide and cyclopentolate (p=0.33 and p=0.18, respectively). Comparison study. In 142 of 150 patients the difference between data obtained by the PowerRefractor and an autorefractor was within 1 D (spherical equivalent). However, there was a considerable difference between the data generated by the two methods in the remaining eight patients (up to 16 D). CONCLUSIONS: The PowerRefractor proved to be a reliable tool for estimating refractive errors in young children. The apparatus is easy to handle and the simultaneous examination of both eyes makes the PowerRefractor ideal for obtaining data on refractive errors in large samples.

Adolescent↗
PubMed2004

The Nepal longitudinal study: predicting myopia from the rate of increase in vitreous chamber depth.

Biometric data on 897 Tibetan children living in Kathmandu, Nepal were collected over the period 1992 to 2000 with regular visits every 2 years. Measurements included cycloplegic autorefraction, A-scan ultrasonography, and video phakometry. Children who had not been studied at least once at age 12 years or older were not included in these analyses. The other subjects were divided into two groups; myopic if the refractive error was ever <-0.50 D, and emmetropic/hyperopic if the refractive error was never <-0.50 D, the nonmyopic group. Using all children who had been examined with four or five observations over time, the change of vitreous chamber depth with age by group was determined using a mixed-model regression method. The increase in vitreous length was 0.070 mm/year for the emmetropic group and 0.165 mm/year for the myopic group, with the differences apparent before the onset of myopia. An independent group of 59 children in whom there were two vitreous chamber depth measures before the age of 12 years and one measure taken after 12 years of age were used to assess the rate of increase in vitreous chamber depth as a predictor of myopia. Two other methods were examined using the independent group; the ratio of axial length to corneal radius of curvature and refractive error at age 10 years. Predictors based on rate of increase in vitreous chamber depth and axial length/corneal radius of curvature had sensitivities of 75% and 45%, respectively, and refractive error at age 10 years as a predictor for those who will not become myopic had a sensitivity of 88%.

Adolescent↗
PubMed2003

Cycloplegic autorefraction results in pre-school children using the Nikon Retinomax Plus and the Welch Allyn SureSight.

PURPOSE: Early detection and treatment of amblyogenic conditions such as high refractive errors and anisometropia can help prevent the development of amblyopia. The traditional gold standard for the determination of refractive error in pre-school children is retinoscopy. Difficulties with retinoscopy in pre-school children have led to the development of autorefractors that can be free of operator bias and can be used by lay individuals. The Nikon Retinomax Plus handheld autorefractor has proven to be reliable for quick and accurate assessments of refractive errors in children. The Welch Allyn SureSight Vision Screener is a relatively new handheld autorefractor. The present study compares the results of measurements with the Retinomax Plus and the SureSight to the results of cycloplegic retinoscopy in pre-school children. METHODS: Thirty-five children ranging in age from 3 to 5 years old were subjects. Any subjects with strabismus, amblyopia, nystagmus, or ocular disease were excluded. Refractive error was assessed 30 min after the application of a cycloplegic spray. RESULTS: Both autorefractors showed moderate agreement with cycloplegic retinoscopy results for measurement of spherical equivalent and cylinder power. In addition, the SureSight and the Retinomax Plus sphere and cylinder results showed moderate agreement with each other. Although the mean differences of the spherical equivalents determined were minimal, the 95% confidence intervals were large, which limits the value of the data obtained from each instrument. CONCLUSIONS: Even though the Retinomax Plus and the SureSight appear to agree with each other and with the results of cycloplegic retinoscopy for determining sphere and cylinder power, interpretation of the data should be considered as screening only because the actual magnitude of sphere and cylinder may vary from the actual magnitude. These results suggest that either device may be useful only as screening tools for assessing refractive error in pre-school children.

Child, Preschool↗
PubMed1998

Prevalence of myopia between 3 months and 5 1/2 years in preterm infants with and without retinopathy of prematurity. Cryotherapy for Retinopathy of Prematurity Cooperative Group.

PURPOSE: The purpose of the study was to examine spherical equivalent refractive errors, especially myopia, at six ages between 3 months and 5 1/2 years post-term in preterm children with birth weights of less than 1251 g. DESIGN: A cohort study. PARTICIPANTS: There were a total of 827 participants in the multicenter study of cryotherapy for retinopathy of prematurity (ROP). Approximately one third of the eyes did not develop ROP, whereas two thirds developed mild-to-severe ROP. None of the eyes underwent cryotherapy. INTERVENTION: Refractive error was measured at 3 months, 1 year, and 5 1/2 years term due date at the five long-term follow-up centers. In most eyes, refractive error also was measured at 2, 3 1/2, and 4 1/2 years. MAIN OUTCOME MEASURE: Myopia was defined as 0.25 diopter (D) or greater with high myopia as 5 D or greater. RESULTS: The proportion of eyes with myopia in this preterm population was increased compared to published data on full-term children and was related to severity of both acute-phase and cicatricial-phase ROP. The percentage of eyes with myopia varied little across ages, ranging from 21.2% at 1 year to 15.7% at 4 1/2 years. The percentage of eyes with high myopia doubled from 1.8% to 3.9% between 3 months and 1 year and remained stable thereafter. The distribution of refractive errors in eyes with mild acute-phase ROP was similar to that of eyes with no ROP. In contrast, eyes with moderate or severe acute-phase ROP showed an increased prevalence of high myopia. The distribution of refractive errors changed between 3 months and 1 year with little change after 1 year. This pattern of refractive development differs from that of full-term infants. Birth weight, severity of ROP, and degree of myopia at 3 months predicted the presence of myopia and high myopia at 5 1/2 years of age. CONCLUSIONS: The distribution of refractive errors in preterm infants from age 3 months to 5 1/2 years varies with severity of acute-phase ROP and cicatricial disease. Changes in refractive error distribution occur primarily between 3 months and 1 year and involve a decrease in the proportion of eyes with hyperopia and an increase in the proportion with high degrees of myopia.

Acute Disease↗
PubMed1983

The Berkeley Orthokeratology Study, Part II: Efficacy and duration.

Relative efficacy of orthokeratology (OK) was evaluated by assessing changes in refractive error, visual acuity, and corneal curvature in 31 treated and 28 randomized control subjects who wore conventional rigid contact lenses. The duration of changes was studied by monitoring subjects after lens wear was discontinued. After an average of 444 days of contact lens wear the treatment group showed an overall mean reduction in spherical equivalent refractive error of 1.01 D compared with 0.54 D in the control group (p = 0.02). Both groups had considerable variation in refractive error change. Corresponding mean improvements in unaided visual acuity were -0.27 and -0.20 log of the minimum angle of resolution [log (MAR)]. Corneal curvature decreased in both comparison groups, but the actual diopter value was about one-half that of the refractive change. The changes in these characteristics tended to occur during the first 132 days of wear, and additional aggressive lens therapy during the remaining 241 days of treatment produced little additional change. The refractive error fluctuated considerably during the period of follow-up and these fluctuations tended to be larger in those subjects who had shown greater changes in refractive error. When the lenses were removed, ocular characteristics returned steadily toward baseline levels. Ninety-five days after discontinuing lens wear, the refractive error had returned 75 and 69% of the way to baseline levels for the treatment and control groups, respectively. Visual acuity and corneal curvature showed similar rebound after 95 days. We conclude that it is possible to reduce myopia about 1D; however, the change is not permanent. Results indicate that the level of vision during periods of nonlens wear would be unstable, making it difficult to predict what the quality of vision would be under a retainer lens wear program.

Clinical Trials as Topic↗
PubMed1986

The triple procedure. Refractive results. 1985 update.

A total of 77 triple procedures performed over a 6-year period were studied retrospectively and prospectively with the goal of producing refractive errors within 2 diopters (D) of emmetropia. Thirty-eight of 58 eyes achieved refractive errors within 2 D of emmetropia over the entire study; however, cases performed in the last 30 months achieved a mean refractive error close to emmetropia. Assuming that accurate axial length measurements were performed, the postoperative keratometry readings and, to a lesser degree, the "A" constant used in the regression formula had the greatest impact on the ultimate refractive error. Only a few cases had unacceptable refractive results possible due to inaccurate axial length measurement and/or incorrectly labeled intraocular lenses. The postoperative keratometry readings closely approximated the estimated preoperative readings that were used in the lens implant power calculation regression formula. With currently available techniques, the triple procedure appears to provide a useful modality for the correction of cases with a combined corneal opacity and a cataract.

Astigmatism↗
PubMed1993

Chromatic aberration and accommodation: their role in emmetropization in the chick.

The roles of chromatic aberration and accommodation as cues to emmetropization in the chick were investigated. Myopia was induced monocularly by lid suture for a period of 1-2 weeks from hatching, after which eyes were reopened and the recovery process followed. Monochromatic light (ML) rearing conditions and ciliary nerve section surgery were used to eliminate chromatic aberration and accommodative activity respectively. Control animals were reared in white light (WL). When accommodation was left intact, chickens reared under monochromatic light were able to recover normally. However, ciliary nerve section produced hyperopia, deepening of the anterior chamber and a tendency towards axial lens thinning, irrespective of the light conditions used. Hyperopic refractive errors peaked at 4 weeks (mean refractive errors: +5.7 D, +4.21 D for ML, WL groups respectively, 4 weeks), with the ML group still exhibiting significant hyperopia at 7 weeks. Ciliary nerve section did not prevent the myopic response to lid suture (mean refractive errors: -22.65 D; -25 D for ML, WL groups respectively, 1 week) nor the elimination of myopia when eyes were reopened. These data indicate that neither accommodation nor chromatic aberration are fundamental to the gross operation of the emmetropization process although they may be essential for the fine tuning of refraction.

Accommodation, Ocular↗
PubMed1994

Refractive status in the Beaver Dam Eye Study.

PURPOSE: To describe the prevalence of refractive errors in a population of adult Americans. METHODS: From 1988 to 1990, 4926 adults who were 43 to 84 years of age and living in Beaver Dam, Wisconsin at the time of the 1987-1988 census were examined. Refractions were performed according to a modification of the Early Treatment Diabetic Retinopathy Study protocol. Included in this study were 4533 people who had not undergone cataract surgery and who had a best corrected visual acuity better than 20/40 in at least one eye. Myopia was defined as a refractive error less than -0.50 diopters; hyperopia was defined as a refractive error greater than +0.50 diopters. RESULTS: Hyperopia was more frequent than myopia in the study group (age-adjusted of 49.0% and 26.2% in right eyes, respectively, P = 0.0001). The prevalence of hyperopia in the right eye increased with increasing age from 22.1% in those 43 to 54 years of age to 68.5% in those 75 years of age or older. The prevalence of myopia in the right eye decreased from 43.0% in those 43 to 54 years of age to 14.4% in those 75 years of age or older. There was significant relationship between education level and refractive error (age adjusted r = -0.32, P = 0.0001). Neither household income nor occupation was associated with refractive error in our data. CONCLUSION: These cross-sectional data indicate age-related differences in refractive status in an adult population and suggest that education is associated with myopia independent of age.

Adult↗
PubMed2002

Emmetropisation following preterm birth.

BACKGROUND/AIMS: Even in the absence of retinopathy of prematurity (ROP), premature birth signals increased risk for abnormal refractive development. The present study examined the relation between clinical risk factors and refractive development among preterm infants without ROP. METHODS: Cycloplegic refraction was measured at birth, term, 6, 12, and 48 months corrected age in a cohort of 59 preterm infants. Detailed perinatal history and cranial ultrasound data were collected. 40 full term (plus or minus 2 weeks) subjects were tested at birth, 6, and 12 months old. RESULTS: Myopia and anisometropia were associated with prematurity (p<0.05). More variation in astigmatic axis was found among preterm infants (p<0.05) and a trend for more astigmatism (p<0.1). Emmetropisation occurred in the preterm infants so that at term age they did not differ from the fullterm group in astigmatism or anisometropia. However, preterm infants remained more myopic (less hyperopic) than the fullterm group at term (p<0.05) and those infants born <1500 g remained more anisometropic than their peers until 6 months (p<0.05). Infants with abnormal cranial ultrasound were at risk for higher hyperopia (p<0.05). Other clinical risk factors were not associated with differences in refractive development. At 4 years of age 19% of the preterm group had clinically significant refractive errors. CONCLUSION: Preterm infants without ROP had high rates of refractive error. The early emmetropisation process differed from that of the fullterm group but neither clinical risk factors nor measures of early refractive error were predictive of refractive outcome at 4 years.

Anisometropia↗
PubMed1999

Prevalence of myopia and refractive changes in students from 3 to 17 years of age.

We investigated changes in the prevalence of myopia and mean changes in refractive errors in Japanese students from 3 to 17 years old from 1984 to 1996. Mass ophthalmologic surveys were performed annually during the course of the study. The age-specific frequency distribution of refractive errors remained similar for 6-year-old students (defined in this study as students in the first grade of primary school) during the 13-year period, but the distribution became gradually skewed toward myopia for 12-year-old students (defined in this study as students in the first grade of junior high school). Comparisons between 1984 and 1996 examinations showed a considerable increase in the incidence of myopia among those 7 years of age or older, and changes in mean refractive errors also demonstrated a greater shift toward myopia, especially in students older than 10 years, for whom the changes were statistically significant. In this 13-year period, the prevalence of myopia increased from 49.3% to 65.6% in 17-year-old students. In addition to the annual mass ophthalmologic examinations, we also performed a longitudinal 6-year study of 346 students who entered junior high school in 1989, 1990, or 1991. Among these students, the prevalence of myopia increased from 43.5% at 12 years of age to 66.0% at 17 years of age. These 346 students were divided into the following eight groups according to their refractive error (spherical power [D]) at 12 years of age: +1 D, 0 D, -1 D, -2 D, -3 D, -4 D, -5 D, and -6 D. Mean progressions of myopia in these students were as follows: for the +1 D group, -0.14 D/year; for the 0 D group, -0.25 D/year; for the -1 D group, -0.37 D/year; for the -2 D group, -0.40 D/year; for the -3 D group, -0.29 D/year; for the -4 D group, -0.25 D/year; for the -5 D group, -0.14 D/year; and for the -6 D group, -0.22 D/year. Boys and girls demonstrated a statistically significant difference in mean changes in refractive errors at the 6-year follow-up examination: the mean change in refractive error was -1.41 +/- 1.25 D for boys as compared with -1.03 +/- 1.07 D for girls (unpaired Student's t-test, P < 0.0001). Our results demonstrated an early age at onset for myopia and a recent increase in the proportion of myopic students. Further studies are needed to shed light on the extent to which myopia is caused by environmental factors, because it is through these factors that the prevalence rate may be affected.

Adolescent↗
PubMed1993

Comparison of cyclopentolate versus tropicamide cycloplegia in children.

This double masked study compares the cycloplegic effects of tropicamide 1% and cyclopentolate 1% in 20 nonstrabismic, nonamblyopic, hyperopic 6- to 12-year-old children with a mean refractive error = +1.48 +/- 1.10 diopters (D). Unlike previous studies which used only amplitude of accommodation to measure the depth of cycloplegia, this study compares refractive error as determined by retinoscopy, distance subjective refraction, and distance autorefraction (Canon R-1). In addition, we compare the amplitude of accommodation as measured by subjective push-up and objective autorefraction methods. There is no statistically significant difference between cyclopentolate and tropicamide for either cycloplegic retinoscopy or distance subjective refraction. Autorefraction measurement of refractive error shows a statistically significant but clinically unimportant bias (0.14 +/- 0.30 D) toward more hyperopia with cyclopentolate. Both drops reveal latent hyperopia, and the mean latencies are not statistically different between the two cycloplegic agents. Latent hyperopia is not systematically related to the degree of hyperopia after tropicamide, but this relation is significant after cyclopentolate. No differences were found between refractive results with either agent at 30 min compared to 60 min after drop instillation. When measured objectively with the autorefractor, accommodation is inhibited more effectively by cyclopentolate than by tropicamide. Our results suggest that although tropicamide is not as effective as cyclopentolate in inhibiting accommodation it is, nevertheless, a useful cycloplegic agent for measuring distance refractive error of low to moderate hyperopia in school-aged children.

Accommodation, Ocular↗
PubMed2004

Assessment of optic nerve head topographic parameters with a confocal scanning laser ophthalmoscope.

AIM: To assess the disc area, age, sex, laterality (side of the eyes) and refractive error dependent differences in optic nerve head topographic parameters in a normal population. METHODS: Optic nerve head topographic analysis of both eyes of 551 healthy Turkish subjects aged 11-75 years (1102 eyes) was performed using a confocal scanning laser ophthalmoscope, the Heidelberg Retinal Tomograph II (HRT II). The effects of disc size, sex, laterality (side of the eyes), age and refractive error on optic nerve head topographic parameters were assessed. Subjects were divided into three different age groups (<30 years, 30-60 years, >60 years) and three different disc area groups (<2.00 mm(2), 2.00-2.25 mm(2), >2.25 mm(2)). Disc area, topography standard deviation and a total of 12 topographic parameters were calculated by HRT II for each subject. Statistical analysis was performed using Student's t-test, multiple regression analysis, Tukey-HSD test, anova and Pearson's correlation coefficient. RESULTS: A total of 543 subjects (298 women and 245 men) were included in the study. The mean disc area of the subjects was 2.12 +/- 0.47 mm(2) (range 1.16-4.98 mm(2)). The mean refractive error of the subjects was -0.58 +/- 1.71 D (range -4.75 D to +4.25 D). The mean cup shape measure was -0.21 +/- 0.07 (95% confidence interval -0.07 to -0.35). The disc area was significantly correlated with all of the topographic parameters but two; namely, the cup shape measure and the height variation contour. Significant age-related differences were detected in four parameters (mean retinal nerve fibre layer [RNFL] thickness, disc area, cup-to-disc area ratio, cup area) and significant sex-related differences were detected three parameters (mean RNFL thickness, height variation contour, RNFL cross-sectional area). However, there were no significant differences in any of the parameters for laterality and refractive error. The parameter cup shape measure did not correlate with any of the five variables investigated. CONCLUSION: Cup shape measure was the only optic nerve head topographic parameter that was independent of age, sex, disc area, laterality and the refractive error. It seems to be a promising parameter in evaluation and comparison of the optic discs of normal subjects, with different disc area, age, sex, refraction error and laterality, as being independent of the main variation factors of the disc topography.

Adolescent↗
PubMed1999

Developmental visual system anomalies and the limits of emmetropization.

Optical defocus can within certain limits predictably alter ocular growth and refractive development in infant monkeys. However defocus, particularly unilateral defocus associated with anisometropia, can also promote abnormal sensory and motor development. We investigated the relationship between the effective operating range for emmetropization in infant monkeys and the refractive errors that produced amblyopia. Specifically, we examined the refractive-error histories of monkeys that did not demonstrate compensating ocular growth for imposed refractive errors and used operant psychophysical methods to measure contrast sensitivity functions for 17 infant monkeys that were reared with varying degrees of optically imposed anisometropia. Imposed anisometropias that were within the operating range of the monkey's emmetropization process were eliminated by differential interocular growth and did not produce amblyopia. On the other hand imposed anisometropias that failed to initiate compensating growth consistently produced amblyopia; the depth of the amblyopia varied directly with the magnitude of the imposed anisometropia. These results indicate that amblyopia and anisometropia are frequently associated because persistent anisometropia causes amblyopia. However, the failure of emmetropization in infants with refractive conditions that are known to promote sensory and motor anomalies indicates that factors other than optical defocus, presumably factors associated with the development of amblyopia and/or strabismus, can also influence early refractive development and in some cases cause anisometropia.

Amblyopia↗
PubMed2003

A population-based study of the refractive outcome in 10-year-old preterm and full-term children.

OBJECTIVE: To evaluate the refractive outcome in 10-year-old prematurely born children and in full-term control children. METHODS: Retinoscopy during cycloplegia was performed in 213 prematurely born children from a previous population-based study on the incidence of retinopathy of prematurity and in 217 children born at term. The spherical equivalent, astigmatism, anisometropia, and significant refractive errors (defined as hypermetropia >3 diopters [D], myopia < or =-1 D, astigmatism > or =1 D in 1 or both eyes, and/or anisometropia > or =1 D) were analyzed. RESULTS: Significant refractive errors were found in 29.6% of the prematurely born and in 7.8% of the full-term children. Prematurely born children had higher prevalences of hypermetropia of more than 3 D, myopia of -1 D or less, astigmatism of 1 D or more, and anisometropia of 1 D or more than those born at term. In the preterm group, the cryotreated children had the greatest risk of refractive errors (16 [64%] of 25 children), with higher prevalences of myopia (<0, < or =-1, or <-3 D), astigmatism (> or =1 D), and anisometropia (> or =1 D). CONCLUSIONS: Significant refractive errors were 4 times more common in 10-year-old prematurely born children than in full-term controls. Cryotreated children had the highest risk, but prematurity per se was also associated with refractive errors. Ophthalmological follow-up of prematurely born children should, therefore, also include children without retinopathy of prematurity in the neonatal period.

Child↗