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PubMed2006

High prevalence of myopia in Japanese patients with idiopathic focal subretinal neovascularization.

PURPOSE: To determine whether myopia is more prevalent in Japanese patients with idiopathic focal subretinal neovascularization (IFSN) than in normal control subjects. METHODS: Forty-seven eyes of 46 patients with an initial diagnosis of IFSN and 291 eyes of 291 controls were studied. Refractive errors were measured with an autorefractometer, and the spherical equivalent of the refractive error was used for the statistical analyses. All patients had undergone fluorescein angiography (FA) to confirm the presence of the choroidal neovascularization. In addition, indocyanine green angiography (ICGA) had been performed to determine whether chorioretinal atrophy and breaks of Bruch's membrane, which are consistent with myopic retinopathy, were present. RESULTS: The mean age of the patients in the control group was not significantly different from that of patients in the IFSN group. The mean spherical equivalent of the refractive errors was -2.62 +/- 2.70 diopters (D) in the control group and -5.24 +/- 3.41 D in the IFSN group (P = 0.00005). The incidence of high myopia was significantly higher in the IFSN group (41.3%) than in the control group (12.0%, P < 0.0001). FA and ICGA showed no chorioretinal atrophy and lacquer cracks, thus confirming that patients with myopic retinopathy were excluded from the IFSN group. During the mean follow-up period (44.7 months), myopic retinopathy did not develop in any of the eyes in the IFSN group. CONCLUSION: Japanese patients with IFSN were highly myopic, suggesting that myopia may play a role in the development of choroidal neovascularization in IFSN patients.

Adolescent↗
PubMed1994

Dark focus of accommodation and vergence posture.

We evaluated the dark focus of accommodation and vergence posture in 20 boys and girls, 10 with and 10 without accommodative esotropia, before and after they wore glasses for at least 1 month. Refractive error was measured by Nidek Autorefractometer AR1600. We used two definitions of the dark focus, DFcus (Non-Cyclo R) and DFcus (Cyclo R). DFcus (Non-Cyclo R) = Dark R - Non-Cyclo R. DFcus (Cyclo R) = Dark R - Cyclo R. (Dark R: refractive state in the dark; Non-Cyclo R: non-cycloplegic refractive error; Cyclo R: cycloplegic refractive error.) Vergence posture was measured by prism cover test during distance fixation while uncorrected. DFcus (Cyclo R) was significantly greater in esotropic subjects than in non-esotropic subjects, although DFcus (Non-Cyclo R) did not differ significantly. A significant hyperopic shift in Dark R was observed after wearing glasses. DFcus (Cyclo R) was significantly decreased after wearing glasses, suggesting that wearing glasses is an important variable of the dark focus. Unlike the dark focus, the vergence posture did not change in either group after wearing glasses. The dissociation of the dark focus from vergence posture seems to be inconsistent with previous findings. It is postulated that change in dark vergence after wearing glasses is responsible for the results.

Accommodation, Ocular↗
PubMed2006

Central corneal thickness is not related to anterior scleral thickness or axial length.

PURPOSE: To examine the relationship between central corneal thickness (CCT), scleral thickness (ST), refractive error, and axial length. METHODS: One hundred forty eyes of 140 patients with no previous history of intraocular surgery were enrolled. Axial length, CCT, and ST were measured ultrasonically. Radial ultrasound biomicroscopy (UBM) images were obtained by a single examiner scanning the temporal corneoscleral limbus. ST was measured independently on the UBM images by two masked observers at scleral spur (ST1) and 2.0 and 3.0 mm posterior to it (ST2 and ST3). RESULTS: Mean patient age was 57.0+/-15.7 (SD) years, and mean refractive error was -1.3+/-5.0 diopters. Intraclass correlation coefficients >0.75 indicated excellent agreement between the two observers for all ST measurements. There was a positive and significant correlation between CCT and ST1 (r=0.27, P=0.001) but not between CCT and ST2 (r=0.02, P=0.8), ST3 (r=0.06, P=0.5), refractive error (r=0.08, P=0.3), or axial length (r=0.07, P=0.4). CONCLUSIONS: CCT correlates with ST only at the scleral spur and is unrelated to refractive error or axial length. This study does not support the hypothesis that a thin CCT is a surrogate marker for abnormal scleral or laminar thickness as an independent cause of increased glaucoma risk.

Body Weights and Measures↗
PubMed1994

Spectacle and contact lens wearing six years after radial keratotomy in the Prospective Evaluation of Radial Keratotomy Study.

BACKGROUND: Patients in the Prospective Evaluation of Radial Keratotomy (PERK) Study stated that a major reason for obtaining radial keratotomy was to see without dependence on corrective lenses. The authors examined lens-wearing patterns 6 years after surgery. METHODS: Of the 435 patients in the PERK Study, the authors analyzed the responses of 328 (75.4%) who elected to have surgery on both eyes, who completed a questionnaire at 6 years, and for whom visual acuity and cycloplegic refraction were available. RESULTS: Sixty-four percent (106/167) of patients younger than 40 years of age and 38% (64/161) of patients older than 40 years of age wore no lenses for distance or near vision. The proportion of time lenses were worn increased with age for those who wore them for close work only (from 18% younger than 40 years of age to 25% older than 40 years of age) and decreased with age for those who wore them for distance only (from 41% to 27%). The authors examined the visual acuity and refractive error criteria for patients to be free of distance lenses. Of the 359 patients who saw 20/20 or better uncorrected in one or both eyes, 77% (n = 198) wore no distance correction, whereas of the 53 patients who saw 20/25 to 20/40 in both eyes or their best eye, only 34% (n = 18) wore no distance correction. Of the 72 patients with a residual refractive error of +/- 0.50 diopters (D) in both eyes, 85% (n = 61) wore no distance correction, whereas of the 87 patients with +/- 1.00 D in both eyes, only 39% (n = 34) wore no distance correction. Of the 328 patients, 60% (n = 197) were highly satisfied with the results of surgery, and satisfaction was primarily predicted by having a visual acuity 20/20 or better in at least one eye and not wearing spectacles for distance vision. Before surgery, 57% of patients reported worrying about their eyesight and 47% reported restrictions in activities because of their eyes; these rates dropped to 31% and 9%, respectively, at 6 years. Of the 328 patients, 74% (n = 243) said their preoperative goals were completely met and 94% (n = 308) said they would have radial keratotomy again. CONCLUSION: The use of 20/40 uncorrected visual acuity and a residual refractive error of +/- 1.00 D were insensitive criteria for evaluating distance spectacle independence. The ability to function without lenses increased substantially only when patients had an uncorrected visual acuity of 20/20 or better in at least one eye, and a refractive error within +/- 0.50 D.

Adult↗
PubMed1990

Experimental studies of emmetropization in the chick.

The eyes of neonates grow from ametropia (refractive error) toward emmetropia. Whether or not this 'emmetropization' is visually guided is controversial. I describe experiments which demonstrate that in the chick refractive state is used to regulate the growth of the eye's vitreous chamber in order to achieve emmetropia from hyperopia or myopia that is induced by different visual deprivations. I discuss several studies that begin to examine the neural pathways that might be involved in the control of eye growth. Optic nerve section was used to examine the level of visual processing necessary for the control of eye growth. Eyes in which the optic nerve has been cut can still grow in the appropriate direction to correct induced hyperopia or myopia. Nevertheless, an intact optic nerve is necessary for normal refractions to be achieved; eyes with optic nerve section overshoot control levels and reverse the sign of the initial refractive error. These findings suggest that eye growth in chicks is controlled by an intraocular mechanism and possibly by a brain-mediated mechanism as well. The hypothesis that ocular accommodation is integral to the control of eye growth was also tested. Complete recovery from induced refractive errors was achieved even when accommodation had been abolished by lesions of the Edinger-Westphal nucleus. The elimination of accommodation did not prevent the ability of chick eyes to compensate for the defocus of spectacle lenses. These results suggest that accommodation is not necessary for the control of eye growth.

Accommodation, Ocular↗
PubMed1997

Ocular abnormalities in Down syndrome: an analysis of 140 Chinese children.

One hundred forty Chinese children with Down syndrome (DS) treated in the Child Assessment Centre of the Duchess of Kent Children's Hospital in Hong Kong between 1985 and 1996 underwent a detailed ophthalmologic evaluation, including test of visual acuity by behavioral testing or retinoscopy, determination of ocular motility, visual field examination, binocular examination for strabismus, determination of near point convergence and pupillary reflex, and/or slit lamp bimicroscopy and ophthalmoscopy to assess ocular health. Only 43 children (31%) had no ocular abnormalities. The overall incidence of ocular abnormalities was 69%, and included refractive error (58%), strabismus (20%), nystagmus (11%), blepharitis/conjunctivitis (7%), lens opacities (4%), and glaucoma (0.7%). No child had Brushfield spots or keratoconus. The incidence of refractive errors increased with increasing age and nearly doubled at school age. As compared with white children with DS, the Chinese children with DS exhibited a higher incidence of refractive error and a similar incidence of lens opacities but a lower incidence of strabismus, nystagmus, blepharitis, Brushfield spots, and keratoconus. Regular visual surveillance, especially of visual acuity, in children with DS as they mature is important in preventing amblyopia.

Adolescent↗
PubMed2005

Ametropia and ocular biometry in a U.K. university student population.

PURPOSE: The prevalence of myopia is known to vary with age, ethnicity, level of education, and socioeconomic status, with a high prevalence reported in university students and in people from East Asian countries. This study determines the prevalence of ametropia in a mixed ethnicity U.K. university student population and compares associated ocular biometric measures. METHODS: Refractive error and related ocular component data were collected on 373 first-year U.K. undergraduate students (mean age = 19.55 years +/- 2.99, range = 17-30 years) at the start of the academic year at Aston University, Birmingham, and the University of Bradford, West Yorkshire. The ethnic variation of the students was as follows: white 38.9%, British Asian 58.2%, Chinese 2.1%, and black 0.8%. Noncycloplegic refractive error was measured with an infrared open-field autorefractor, the Shin-Nippon NVision-K 5001 (Shin Nippon, Ryusyo Industrial Co. Ltd, Osaka, Japan). Myopia was defined as a mean spherical equivalent (MSE) less than or equal to -0.50 D. Hyperopia was defined as an MSE greater than or equal to +0.50 D. Axial length, corneal curvature, and anterior chamber depth were measured using the Zeiss IOLMaster (Carl Zeiss, Jena, GmBH). RESULTS: The analysis was carried out only for white and British Asian groups. The overall distribution of refractive error exhibited leptokurtosis, and prevalence levels were similar for white and British Asian (the predominant ethnic group) students across each ametropic group: myopia (50% vs. 53.4%), hyperopia (18.8% vs. 17.3%), and emmetropia (31.2% vs. 29.3%). There were no significant differences in the distribution of ametropia and biometric components between white and British Asian samples. CONCLUSION: The absence of a significant difference in refractive error and ocular components between white and British Asian students exposed to the same educational system is of interest. However, it is clear that a further study incorporating formal epidemiologic methods of analysis is required to address adequately the recent proposal that juvenile myopia develops principally from "myopiagenic" environments and is relatively independent of ethnicity.

Adolescent↗
PubMed2001

Effect of myopia on frequency-doubling perimetry.

PURPOSE: To examine the effect of myopia, occasionally associated with glaucomatous eyes, on the results obtained by frequency-doubling perimetry (FDP). METHODS: Sixty emmetropic or myopic normal volunteers (mean age, 26.2 +/- 0.35 years, mean +/- SEM; range, 19-34) with good visual acuity and without glaucoma were divided into three groups. The groups were emmetropia to low-myopia (mean refractive error, -1.16 +/- 0.23 D), intermediate-myopia (-4.95 +/- 0.17 D), and high-myopia (-8.12 +/- 0.36 D; n = 20 each). All subjects were tested on the FDP full-threshold C-20 program and the Humphrey Field Analyzer (HFA; Humphrey, Dublin, CA) full-threshold program on one randomly selected eye. FDP and the HFA test were conducted with the subjects wearing their full distance correction and with their distance correction with appropriate additional correction for near, respectively. The calculated mean sensitivity (MS), mean deviation (MD), pattern standard deviation (PSD), and test durations for FDP and the HFA test for the three groups were compared using one-way analysis of variance. The relationship between the refractive error and MS, MD, or PSD was also analyzed by simple regression analysis. RESULTS: The MS and MD for the fields determined by the HFA decreased significantly as the refractive errors increased, but there were no significant differences in the MS, MD, and PSD for FDP between the three groups. There were no significant differences in the test durations between the three groups for both FDP and HFA testing. The refractive error was correlated with both MS and MD only for the fields determined by the HFA. CONCLUSIONS: The results showed that lens-corrected myopia does not alter the visual fields obtained by FDP, and FDP can therefore be used regardless of the presence of myopia.

Adult↗
PubMed1999

Computer modeling of visual impairment caused by intraocular lens misalignment.

PURPOSE: To evaluate a computer program to modulate the visual impairment caused by intraocular lens (IOL) misalignment and visualize results obtained by numerical calculations. SETTING: Department of Ophthalmology, Medical Faculty of Charles University, Prague, Czech Republic. METHODS: The optic imagery of a Landolt circle was calculated using a ray-tracing computer program. Visual aberrations resulting from a decentered and/or tilted IOL were studied using this program and compared with theoretical calculations. RESULTS: The IOL decentration and/or tilt shifted the postoperative refractive errors toward myopia and astigmatism (oblique). The combination of IOL decentration and tilt produced a refractive error that depended on the relationship between the geometrical axes of the decentration and tilt. The refractive error can be enhanced or diminished depending on the relationship of these axes. CONCLUSIONS: These findings verify the results calculated by paraxial vergence equations. A ray-tracing program simulated the optic imagery for various kinds of IOL misalignment and IOL optic properties.

Astigmatism↗
PubMed2000

Laboratory, clinical, and kindergarten test of a new eccentric infrared photorefractor (PowerRefractor).

PURPOSE: Photorefraction is a convenient way to determine refractive state from a distance. It is, therefore, useful for measuring infants and noncooperative subjects. However, its reliability (or precision) and accuracy (or validity) has been questioned. In a study in subjects without cycloplegia, we have tested whether, after complete automatization, eccentric photorefraction at a 1-m distance can be as reliable as a common autorefractor. METHODS: In a laboratory study of 15 student subjects without the use of cycloplegia (30 eyes, refractive errors ranging from -6 D to +6 D), age 25 to 31 years, the photorefractive measurements were compared with spectacle prescriptions. In a clinical study, photorefraction, autorefraction, and subjective refraction were performed in 40 patients without cycloplegia (refractive errors ranging from -4 D to +4 D), most of them with various ocular pathologies. Subjective refractions were obtained by an experienced clinical ophthalmologist but were not accessible to the examiner who used the two refractors. Visual acuity was 20/20 or better except for five subjects. Ages ranged from 6 to 75 years. In the kindergarten screening study, 108 children aged 3 to 6 years were screened for refractive errors. RESULTS: In the laboratory study, it was found that the mean difference between spectacle prescription and PowerRefractor measurements was < 0.6 D for spheres and below 0.4 D for cylinders. In the clinical study, data were obtained by all three procedures in 78 eyes. The photorefractor and the autorefractor performed similarly for spheres (mean absolute dioptric difference between refractor and subjective measure: 0.593 D and 0.696 D) and cylinders (mean absolute dioptric differences: 0.399 D and 0.389 D). However, the photorefractor was superior with regard to the measurement of the magnitude and axis of astigmatism (mean weighted difference between objective and subjective axis 0.644 D and 0.769 D, respectively). In the kindergarten study, it was found that the PowerRefractor was very convenient to handle. The autorefractor measured more myopic refractions than the PowerRefractor (mean of the left eyes 0.11 +/- 1.1 D vs. 0.62 +/- 0.53 D, p < 0.001). There was no indication that the PowerRefractor failed to detect hyperopia, because all but one child with more than 2 D of hyperopia measured with autorefractor (n = 7) was also hyperopic with the PowerRefractor. Furthermore, presenting an interesting fixation target at a 3-m distance did not cause more hyperopic refractions, indicating that the camera of the PowerRefractor at a 1-m distance was not a significant stimulus to accommodation. CONCLUSIONS: The PowerRefractor was shown to have comparable or slightly better reliability and accuracy than a modern autorefractor; however, it has major advantages over current autorefractors in that it is faster, measures both eyes at once, and gives interpupillary distance, pupil size, and information on the alignment of the eyes at the same time.

Adolescent↗
PubMed2006

Quantitative in vivo retinal thickness measurement in chinese healthy subjects with retinal thickness analyzer.

PURPOSE: To measure the retinal thickness of the posterior pole in healthy Chinese subjects using a retinal thickness analyzer and to compare the retinal thicknesses between different age, gender, and refractive error groups. METHODS: Between February 2002 and September 2004, healthy Chinese subjects (age range, 21-50 years), underwent measurements of visual acuity, refractive error, intraocular pressure, and posterior pole retinal thickness with the RTA, as well as ophthalmoscopy and slit lamp examinations. Eleven retinal thickness parameters were directly derived from the reports of the RTA measurement. The average value of each parameter was compared between the male and female groups, the emmetropia and low-myopia groups, and the three age groups (21-30, 31-40, and 41-50 years). Linear regression analysis was also applied to determine the effect of age on 11 parameters. Some participants were also enrolled in the reproducibility assessment procedure. RESULTS: The 272 eyes of 272 subjects (mean age, 34.4 years) were included. The intraclass correlation coefficients of intravisit and intervisit reproducibility were 0.95 and 0.88, respectively. The average retinal thicknesses at the foveola and fovea are 147.6 and 160.0 microm, respectively. No significant difference was found in any of the parameters between the different gender groups, emmetropia and low-myopia groups, or age groups. Regression analysis revealed no significant negative linear correlation between any of the parameter values and age. CONCLUSIONS: The retinal thickness of macular region in the Chinese is a little lower than in Westerners, but not statistically significant. The Chinese retinal thickness was not gender or refractive error related.

Adult↗
PubMed1996

Baltimore Vision Screening Project.

PURPOSE: This study estimates the prevalence of common visual disorders (amblyopia, strabismus, refractive errors) in a group of inner-city school children. In addition, the study addresses the issue of access to care for vision-screening programs, specifically for children with recognized difficulties in obtaining routine medical care. METHODS: School children from an inner-city elementary school were enrolled into a prospective vision-screening program combining the identification arm (screening) and diagnostic/treatment arm (ophthalmic examination). The screening consisted of Snellen E optotypes presented at a 10-foot test distance. Each child failing the vision screening was examined by an ophthalmologist at the school using standard protocol. This allowed the authors to examine all children identified through the vision-screening program. RESULTS: Six-hundred eighty children were screened during the 1993 to 1994 school year. Eleven percent (76) failed the vision screening and were examined, 68 of whom failed the ophthalmic examination. The estimated prevalence of visual morbidity was as follows: amblyopia, 3.9%; strabismus, 3.1%, and refractive errors, 8.2%. CONCLUSION: Amblyopia, strasbismus, and refractive errors were found in relatively high frequencies for this population sample of inner city children. These findings underscore the necessity of comprehensive vision-screening programs that integrate follow-up care. Children with limited access to specialized eye care must be provided with a mechanism for obtaining these services.

Amblyopia↗
PubMed2004

Quality of vision following clinically successful penetrating keratoplasty.

PURPOSE: To evaluate visual function following clinically successful penetrating keratoplasty (PKP). SETTING: Department of Ophthalmology, Ege University, School of Medicine, Izmir, Turkey. METHODS: Patient group (PG) included 9 patients (12 eyes) who had clinically successful PKP in our department. The control group (CG) included 12 people (18 eyes) who had no ocular disease other than refractive errors. Those with a visual acuity level less than 20/25 were not included in the study. Contrast sensitivity levels and light threshold values of the central retina were measured; scanning-slit corneal topography-pachymetry and aberrometric analysis were performed. RESULTS: There were no statistical difference in terms of age (32.55 years +/- 9.25 (SD) in PG, 36.75 +/- 5.85 years in CG; P =.53), cylinder power in plus form (2.60 +/- 1.25 diopter (D) in PG, 2.79 D +/- 2.51 D in CG; P =.88), and spherical equivalent of refractive errors (-3.66 +/- 3.57 D in PG, -5.52 +/- 3.37 D in CG; P =.29) between the PG and CG. Cambridge low-contrast grating scores were 96.5 +/- 41.1 in grafted eyes and 148 +/- 27.7 in CG (P =.004). Central retinal light sensitivity was measured as 29.91 +/- 2.39 db in PG and 33.08 +/- 1.56 db in CG (P =.001). In corneal topographic analysis, mean kappa intercept was 0.69 +/- 0.37 mm in PG and 0.55 +/- 0.24 mm in CG (P =.20). Lower-order Zernike root mean squares (RMS) were 7.30 +/- 3.89 microm for PG and 8.58 +/- 3.46 microm for CG (P =.37). However, higher-order Zernike RMS were 2.15 +/- 0.78 in PG and 0.38 +/- 0.10 in CG, which is a statistically significant difference (P<.001). CONCLUSIONS: Even though the clinically successful PKP patients have correctable amount of spherocylindrical refractive errors with spectacle lenses, they still have reduced visual quality because of the significantly high amount of higher- order aberrations when compared with naturally occurring refractive errors.

Adult↗
PubMed2000

[Refraction and anterior chamber depth change after vitrectomy for pseudophakia].

PURPOSE: To evaluate the association between the vitreous and the refractive error in pseudophakia. METHODS: Vitrectomy was performed in 67 eyes of 61 patients who underwent cataract surgery. Vitrectomy was needed for epiretinal membrane in 30 eyes, macular edema in 22 eyes, macular hole in 3 eyes, lamelar macular hole in 2 eyes, vitreous opacity in 6 eyes, and vitreous hemorrhage in 4 eyes. Refraction was measured before the operation, and 1 month, 3 months, 6 months, and 12 months after operation. Anterior chamber depth was measured in 10 eyes before the operation, and 1 month, 3 months, and 6 months after operation. We evaluated the refractive error after vitrectomy in 49 eyes that had predicted refraction. RESULTS: The mean value of refractive change was -0.3 D 1 month postoperatively, and then gradually became positive. The variation of refraction (6-month postoperative refraction minus preoperative refraction) was negatively correlated with preoperative refraction (p = 0.0052, R2 = 0.146). If preoperative refraction was more myopic than -1.5 D, then refraction became positive. If preoperative refraction was not more myopic than -1.5 D, then refraction became negative. CONCLUSION: About 15% of postoperative refractive error may be associated with the vitreous, but further investigation is required.

Aged↗
PubMed2004

[Corneal asphericity in a young adult population. Clinical implications].

PURPOSE: To determine the relevance of the different ocular optical components in the refractive state of young adults, paying special attention to the corneal topography represented by the asphericity value. SUBJECTS AND METHODS: Corneal topographies and ultrasonic biometries were obtained from 109 university students with different refractive errors (spherical equivalent range: +3.25 D to -11.00 D). A regression study was performed in order to establish the relationships between corneal asphericity and refractive error, as well as other ocular optical components related to the emmetropization mechanism of the eye. RESULTS: The mean asphericity values were -0.23 (SD 0.08, range: -0.42 to -0.03). All the values correspond to the mathematical description of the prolate ellipse, most commonly accepted for the normal human cornea. The statistical correlation between asphericity and equivalent refractive error was not significant, but a significant correlation was found for the asphericity with respect to the radius of curvature, vitreous chamber depth and axial length. CONCLUSIONS: 1) The asphericity values support the generalised morphology of the prolate cornea as the standard. The influence of this configuration on the contact lens fit, refractive surgery or the visual performance of the eye are discussed. 2) Results suggest that, although a relationship between axial length and corneal topography actually exists, it is not likely that the latter has implications for the emmetropization mechanisms which determine the refractive state of the adult eye.

Adult↗
PubMed2003

[Visual screening to discover ophthalmologic disorders in children].

PURPOSE: [corrected] To report the frequency of common childhood ocular disorders in a pediatric population. To address the issue of access to care for vision screening programs. METHODS: Prospective vision screening for a period of 2 years (February 2001-February 2003) which enroll 254 children from 3 villages (Cepleniţa, Vlădeni, Aroneanu) sponsored by World Vision Romania. The study asses refractive errors, strabismus, amblyopia and other ocular abnormalities. RESULTS: The mean age was 8.09 +/- 2.88 with the following distribution: preschool 19%, first grade 56%, second grade (over 10 years of age) 25%. Refractive errors requiring correction were observed frequently in this group of children (especially mild hyperopia, small myopia, astigmatic refractive errors). Strabismus was identified în 7.87% of cases and amblyopia în 11.42% (1/3 of cases mild and severe). CONCLUSIONS: The frequency of common visual disorders in this population sample was larger than previously published studies. In poor economic subgroups the first ophthalmologic examination was performed after school age. Access to care is an integral part of any vision screening program. We are trying to highlight the importance of effective follow-up programs for all children especially those with limited resources for health care.

Adolescent↗
PubMed1990

Ocular dimensions and refractive power in Malay and Melanesian children.

A cross-sectional study of 753 Melanesian children in Vanuatu and 904 Malay children in Malaysia included measurement of refractive error and ocular dimensions. All children were between the ages of 6 and 17 years. The prevalence of myopia in Malay children was 4.3% at 7-8 years and 25.6% at 15-16 years with corresponding figures of 0.8% and 4.3% for Melanesian children. The range of refractive error was greater for Malay children at all ages. Mean refractive error for Malay children showed greater hypermetropia, together with a shorter axial length at 6 years, than Melanesian children, but at 17 years the situation reversed and Malay children had more myopia and longer axial lengths than their Melanesian counterparts.

Adolescent↗
PubMed2004

Sources of normal and anomalous motion in retinoscopy.

PURPOSE: Besides the classic "with," "against," and "neutral" absence of motion, retinoscopic reflexes can display anomalous "with" motion in myopia. A model is presented that explains the source of this anomalous motion, as well as quantifies the appearance of retinoscopic motion in myopia and hyperopia. METHODS: Various 2 x 2 matrices were created to describe schematic eyes for a +20 D trial lens, a Gullstrand #1 schematic eye, and an infant schematic eye. Rays from the retinoscope were traced paraxially through these matrices over a full transit of the retinoscope beam across the pupil. Retinal position of the edge of the reflex visible to the observer was plotted as a function of pupil sizes from 2 mm to 16 mm for -5.00 D and +2.00 D refractive errors for the +20 D trial lens. RESULTS: The edge of the retinoscopic reflex could be formed by one of two sources: the edge of the retinoscope beam itself, or the shadow cast by the beam against the edge of the pupil. Anomalous "with" motion arose in myopia when the edge of the reflex was formed by the edge of the beam. The edge of the beam was also visible in hyperopia but did not create anomalous motion. The retinoscope peephole was not involved in the formation of the edge of the reflex. The degree of anomalous motion increased with greater myopia and pupil size. Measured pupil sizes needed to completely eliminate anomalous motion agreed well with those predicted by the model, except at the largest pupil sizes. The limit for anomalous motion depended only on pupil size, refractive error, and working distance but not on whether the system matrix represented the trial lens, a Gullstrand #1 eye, or an infant eye. CONCLUSIONS: Seeing the edge of the beam at large pupil sizes during retinoscopy creates anomalous "with" motion in myopia but may make the reflex easier to see in hyperopia. Anomalous "with" motion in myopia can be managed by adjustment of pupil size, working distance, or net corrected refractive error. Aside from possible effects of aberrations, retinoscopic motion appears to be consistent across various paraxial optical systems for a given refractive error and pupil size.

Artifacts↗