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PubMed2006

Accommodative facility in eyes with and without myopia.

PURPOSE: To compare accommodative facility in eyes with myopia to that in eyes with emmetropia or hyperopia and to determine whether accommodative facility can be used to predict an association with myopia. METHODS: In the Sydney Myopia Study, year-1 school children (6.7 +/- 0.4 years) were assessed for accommodative facility at distance (3 m) and near (33 cm) with semiautomated flippers. Spherical equivalent refractive error (RE) was defined as myopia (< or = -0.50 D), emmetropia (> -0.50 D, but < +1.50 D), and hyperopia (> or = +1.50 D) based on postcycloplegia readings. Only right eye data were considered. Differences between groups were analyzed with the Brown-Forsythe F test after adjustment for age and gender. Multiple comparisons were adjusted with the by the Games-Howell METHOD RESULTS: Of the 1328 right eyes assessed, 20 (1.5%) eyes were myopic, 977 (73.6%) were emmetropic, and 331 (24.9%) were hyperopic. At distance, mean facility was less for myopic eyes at 5.5 +/- 2.0 cycles per minute (cpm) in comparison to 6.9 +/- 1.7 cpm for eyes with emmetropia or hyperopia (P = 0.005). Myopic eyes recorded greater positive and negative accommodative response times than did emmetropic or hyperopic eyes (P < 0.05). There were no differences among the groups in near facility. The area under the receiver operating characteristic (ROC) curve for distance facility was 0.692 (P = 0.003, 95% CI, 0.580-0.805). CONCLUSIONS: Myopic eyes have reduced accommodative facility at distance, and accommodative responsiveness to both positive and negative defocus is slow. However, accommodative facility as a test does not have sufficient power to discriminate eyes with myopia from other refractive errors.

Accommodation, Ocular↗
PubMed1984

The optical effects of eyelid closure on the eyes of kittens reared in light and dark.

Monocular closure surgically performed during development by suturing the eyelids induced less hyperopia in the closed eye of light reared kittens (+0.95 Diopters) in comparison to the closed eyes of lid sutured dark reared kittens (+2.61 D). The normal control cats were also slightly hypermetropic (+0.69 D). While a certain proportion of myopic eyes was found in the monocularly closed light reared kittens and in the normal control cats, no one eye was myopic either in the operated or nonoperated dark reared kittens. Lid suture was found to considerably increase the hyperopia also in adult cats. The incidence of astigmatism was 47.0% for the closed eye in the lid sutured light reared kittens and 64.7% for their open eyes; for the lid sutured dark reared kittens the proportions were 45.4% and 54.5%, respectively. The incidence of astigmatism was 20.2% for the eyes of the normal control cats. Axial length of the closed eye of light (19.00 mm) and of dark (19.45 mm) reared kittens was smaller in comparison to that of the normal control cats (20.38 mm). The corneal curvature of the closed eyes of light (8.09 mm) and of the dark (8.64 mm) reared kittens was flatter than in the normal controls (7.11 mm). It is concluded that lid closure in kittens has a corneal effect, accentuating the tendency for hypermetropia naturally occurring in the dark. In the light lid closure results in an imbalanced combination of the corneal and the (axial?) visual deprivation effects, causing a considerable variability in the refractive error with a tendency for cancellation of the naturally occurring hyperopia.

Animals↗
PubMedDate not supplied

Calibration of photoscreeners for single-subject, contact-induced hyperopic anisometropia.

BACKGROUND: In 1999, the threshold anisometropic hyperopia for photoscreening toddlers and preschoolers was determined to be 1.50 D. We compared crescent size from induced anisometropic hyperopia using three commercially available photoscreeners and compared them with miniature digital video cameras, which have a flash-to-lens dimension similar to two of the three photoscreeners. Photoscreeners were compared with a remote autorefractor. METHODS: Anisometropia was induced by placing several known minus contact lenses (-1.00, -1.50, and -2.00 D) in the nondominant eye of a visually healthy, orthophoric emmetrope older than 3 years. Photographs were taken in light and dim conditions with all three cameras with and without the contact lenses. Corneal diameter, pupil diameter, and crescent location were determined. A protocol for flash initiation, focus, and distance was determined for the digital cameras. RESULTS: Under light and dim ambient light, no camera yielded a significant hyperopic crescent for emmetropia (no contact lens) or induced 1.0-D anisometropia. We propose a simple measure, "delta center crescent" distance from the center of the pupil to the edge of the crescent. Delta center crescent less than 1.5 mm identified most examples of threshold hyperopic anisometropia. The ideal distance for photoscreening using the digital cameras is approximately 1.6 m, whereas the commercially available photoscreeners focus at 1.0 m. CONCLUSIONS: We have developed a protocol for photoscreening and its interpretation with a miniature digital video camera weighing 400 g and costing approximately dollar 1,000. Threshold anisometropic hyperopia can be determined from digital still or audio-labeled video flash images if the pupils are at least 4 mm.

Amblyopia↗
PubMedDate not supplied

The cost and yield of photoscreening: impact of photoscreening on overall pediatric ophthalmic costs.

BACKGROUND: Approximately 5% of preschool-age children suffer from amblyopia. Many of them have high or unequal hyperopia. Amblyogenic risk factors frequently can be detected by photoscreening. METHODS: Free photoscreening was offered to Alaskan children ages 1 to 5 from urban and rural screening hubs. Screened images were mailed to the Alaska Blind Child Discovery coordinating center for physician photoscreen interpretation, specifically seeking latent or anisometropic hyperopia. Parents and screeners then were mailed results and information about amblyopia. Follow-up examination data were tallied, and a cost-consequence analysis was developed for various vision screening paradigms and eye care. RESULTS: From 1996 through 2003, a total of 13,255 screenings were performed with a positive interpretation rate of 4.7%. Penetrance of screening was 22% in urban and 44% in rural communities. Positive predictive value was estimated to be more than 90%. Average cost to screen and inform an Alaskan preschooler was approximately 10.67 dollars, and cost to detect amblyogenic risk factors by photoscreening in an Alaskan was approximately 206 dollars. Compared to American Academy of Pediatrics (AAP) 1995 guidelines, implementing photoscreening added 9%, while mandating complete prekindergarten examination added 49% to overall eye care. CONCLUSIONS: MTI photoscreening achieved high community penetrance and high positive predictive value for latent hyperopia and other amblyogenic factors. When follow-up costs are considered, adding photoscreening to current AAP guidelines may add 112 dollars per child over 10 years, but probably would assist in the reduction of amblyopia. Penetrance of urban photoscreening likely will remain low unless pediatric vision screening guidelines and reimbursement are revised.

Alaska↗
PubMed2000

Peripheral refraction and ocular shape in children.

PURPOSE: To evaluate the relation between ocular shape and refractive error in children. METHODS: Ocular shape was assessed by measuring relative peripheral refractive error (the difference between the spherical equivalent cycloplegic autorefraction 30 degrees in the nasal visual field and in primary gaze) for the right eye of 822 children aged 5 to 14 years participating in the Orinda Longitudinal Study of Myopia in 1995. Axial ocular dimensions were measured by A-scan ultrasonography, crystalline lens radii of curvature by videophakometry, and corneal power by videokeratography. RESULTS: Myopic children had greater relative hyperopia in the periphery (+0.80 +/- 1.29 D), indicating a prolate ocular shape (longer axial length than equatorial diameter), compared with relative peripheral myopia and an oblate shape (broader equatorial diameter than axial length) for emmetropes (-0.41 +/- 0.75 D) and hyperopes (-1.09 +/- 1.02 D). Relative peripheral hyperopia was associated with myopic ocular component characteristics: deeper anterior and vitreous chambers, flatter crystalline lenses that were smaller in volume, and steeper corneas. Lens thickness had a more complex association. Relative peripheral hyperopia was associated with thinner lenses between refractive error groups but changed in sign to become associated with thicker lenses when analyzed within each refractive error group. Receiver operator characteristics analysis of the ocular components indicated that vitreous chamber depth was the most important ocular component for characterizing the myopic eye, but that peripheral refraction made a significant independent contribution. CONCLUSIONS: The eyes of myopic children were both elongated and distorted into a prolate shape. Thinner crystalline lenses were associated with more hyperopic relative peripheral refractions across refractive error groups, but failure of the lens to thin may account for the association between thicker lenses and more hyperopic relative peripheral refractions within a given refractive group. Increased ciliary-choroidal tension is proposed as a potential cause of ocular distortion in myopic eyes.

Adolescent↗
PubMed2002

Prevalence rates of refractive errors in Sumatra, Indonesia.

PURPOSE: To determine the prevalence rates of myopia, hyperopia, astigmatism, and anisometropia in a prevalence survey of adults in Sumatra, Indonesia. METHODS: A population-based prevalence survey of 1043 adults 21 or more years of age was conducted in five rural villages and one provincial town of the Riau Province, Sumatra, Indonesia. A one-stage household cluster sampling procedure was used wherein 100 households were selected from each village or town. Refractive error measurements were obtained with one of two handheld autorefractors. Household interviews were conducted to obtain information on relevant lifestyle risk factors. RESULTS: The age-adjusted overall prevalence rates of myopia (SE [spherical equivalent] at least -1.0 D), hyperopia (SE of at least +1.0 D), astigmatism (cylinder of at least -1.0 D), and anisometropia (SE difference of +1.0 D) were 26.1% (95% confidence interval [CI]: 23.4-28.8), 9.2% (95% CI: 7.4-11.0), 18.5% (95% CI: 16.2-20.8), and 15.1% (95% CI: 12.9-17.4), respectively. The age-adjusted overall prevalence rate of high myopia (SE at least -6.0 D) was 0.8% (95% CI: 0.2-1.5). In a multiple logistic regression model, myopia rates varied with age and increased with income. Hyperopia, astigmatism, and anisometropia rates were independently higher in older adults. CONCLUSIONS: The prevalence rates of myopia in provincial Sumatra are higher than the rates in white populations, but lower than the rates in other urbanized Asian countries such as Singapore. The prevalence rate of high myopia is lower than in most other populations, and other refractive errors are common.

Adolescent↗
PubMed2004

Light-adjustable lens: development of in vitro nomograms.

PURPOSE: To determine whether digital spatial intensity patterns can be developed to effect precise in vitro correction of myopic, hyperopic, and astigmatic refractive errors in a silicone light-adjustable lens (LAL). Also, to determine whether a new spatial intensity pattern for "lock-in" is effective in vitro. METHODS: A digital interferometer/irradiation system was developed to irradiate LALs and measure the power change following irradiation. Light-adjustable lenses were mounted into a wet cell maintained at 35.0 +/- 0.5 degrees C (simulated ocular temperature) and allowed to equilibrate for a minimum of 2 hours. Ultraviolet light was then applied with spatial light intensity patterns to correct hyperopia, myopia, and astigmatism. Light-adjustable lenses were also treated to effect lock-in with a separate spatial light intensity pattern. Treated lenses were characterized for power change and optical quality. In the case of lock-in, exhaustive chemical extraction was also performed to determine the percentage of remaining macromer. RESULTS: Appropriate digital irradiation spatial intensity patterns were created to develop nomograms for in vitro correction of myopia, hyperopia, and astigmatism in approximate 0.25 D steps. Power changes were reproducible and did not alter optical quality of the LALs. Further, lock-in dosing of the LALs did not alter optical quality or significantly change LAL power. CONCLUSIONS: In vitro nomograms have been developed for a silicone LAL that permit precise correction of myopia, hyperopia, and astigmatism. Furthermore, a spatial light intensity pattern has been devised that effects lock-in without significantly altering LAL power or optical quality.

Astigmatism↗
PubMed1992

Optometric management of optically induced consecutive exotropia.

A 5-1/2 year old black female initially presenting with a moderate angle esotropia and latent hyperopia developed a large angle constant exotropia 2 years after final correction of her refractive error. The occurrence of consecutive exotropia as a result of optical correction of hyperopia has been documented infrequently in the ophthalmologic literature and has rarely been mentioned in the optometric literature. While the overall risk for occurrence of this complication from correction of hyperopia may be small, it is a problem which may occur and can be avoided. Unfortunately, there is only limited information about the various risk factors that should be monitored to avoid the occurrence of an optically induced consecutive exotropia. What is available with regard to evaluation and management is scant, and there are no case reports emphasizing optometric management which includes the use of lenses, occlusion and vision therapy. The purpose of this paper is to present a case report of optically induced consecutive exotropia followed by a summary of the available information from the optometric and ophthalmologic literature. This combined information will aid optometrists managing these patients to avoid the occurrence of this problem and better understand the various management aspects when it does occur.

Accommodation, Ocular↗
PubMed2005

The study of corneal topography in myopic and hyperopic children.

PURPOSE: To compare the differences of corneal topographies in myopic and hyperopic children and study the effect of Atropin on their changes. METHODS: The refractive components of 136 eyes with different refractive conditions were measured with A-Scan and their corneal topographies with and without cycloplegia were obtained respectively. RESULTS: The mean corneal power of zones 3mm (MD3, P=0.031) and minor keratometer K2 (P=0.003) of myopia are greater than those of hyperopia without cycloplegia. MD3 (P=0.009) and Keratometer K1 (P = 0.025) increased in hyperopic eyes, while MD3 (P=0.033), K1 (P = 0.035) and K2 (P = 0.002) decreased in myopic eyes significantly after cycloplegia. Similarly, the mean corneal power of zones 5mm (MD5) and 7mm (MD7) in myopic eyes decreased dramatically (P < or = 0.001). CONCLUSIONS: The corneal power was found to be greater in myopia than that in hyperopia. The effect of Atropin on corneal shape of myopia and hyperopia was in the opposite direction.

Accommodation, Ocular↗
PubMedDate not supplied

Clear lens extraction and intraocular lens implantation in normally sighted hyperopic eyes.

BACKGROUND: Currently used corneal refractive procedures do not offer a perfect solution for high hyperopia. This article proposes clear lens extraction and intraocular lens (IOL) implantation for the correction of high hyperopia. METHODS: Extracapsular clear lens extraction and posterior chamber IOL implantation was performed in 10 normally sighted eyes of five patients with a hyperopic spherical equivalent refraction between +7.88 and +9.75 D. The follow-up period was 18 months. RESULTS: Mean uncorrected visual acuity improved from count fingers to 20/25. All eyes saw 20/30 or better without correction. Postoperative correction ranged from -0.37 to +0.50 diopters (mean, 0.01). The mean endothelial cell loss percentage at 18 months was 11.2% +/- 1.87% (range, 8% to 13%). CONCLUSIONS: The excellent results of contemporary cataract surgery, the reduced morbidity, patient satisfaction, as well as accuracy and rapid stability of the refraction suggest that clear lens extraction and IOL implantation are useful refractive procedures for the correction of high hyperopia.

Adult↗
PubMed1996

Effects of continuous light on experimental refractive errors in chicks.

It is possible to induce ametropias in young chicks either by depriving the developing eye of clear form vision with a translucent goggle or by defocusing the retinal image with convex or concave lenses. The refractive properties of the developing chick eye are also altered by raising young birds in a continuous light environment. The effects of superimposing form deprivation or defocus treatments on chicks raised in continuous light are unclear. Newly hatched (n = 31) chicks were raised for 2 weeks under continuous light while wearing either translucent goggles or + 10 or -10 diopter (D) lenses over one eye. Refractive states, corneal curvature and intraocular dimensions were measured periodically by retinoscopy, keratometry and A-scan ultrasound. The birds were sacrificed after 2 weeks and the eyes removed and measured with calipers. Under continuous light, all eyes treated with translucent goggle and -10 D lens developed moderate myopia (-2.6 +/- 0.5 D and -1.4 +/- 0.3 D, respectively) by day 4. The eyes treated with a + 10 D lens developed moderate hyperopia (+ 4.8 +/- 0.5 D) at day 4. Corneal curvatures of all treated eyes were slightly, but significantly, larger than contralateral control eyes by day 4. After 2 weeks of goggle or lens application, all the treated eyes were hyperopic due to corneal flattening. But the eyes treated with a goggle or a -10 D lens still showed relative myopia compared to the fellow eyes (treated minus untreated = -3.8 +/- 0.4 D and -2.8 +/- 0.4 D, respectively), and the eyes treated with a + 10 D lens showed more hyperopia than fellow eyes (treated minus untreated = + 5.1 +/- 0.6 D). Compared with the control eyes, the axial length (mainly vitreous chamber depth) was slightly, but significantly, increased in the eyes treated with a goggle or a -10 D lens, and the axial length decreased slightly in the eyes treated with + 10 D lens. The results suggest that form deprivation and retinal defocus (induced by +/- 10 D lenses) could still induce experimental refractive errors (myopia and hyperopia) in chicks kept under continuous light, but the effects of form deprivation and retinal defocus were partially suppressed by continuous light.

Accommodation, Ocular↗
PubMed1995

Reduction of infant myopia: a longitudinal cycloplegic study.

Changes of cycloplegic retinoscopy refraction from 8.5 to 38.5 months of age were compared in two infant groups in the Cambridge population: "infant myopes", having at least one myopic axis (0 to -3.5 D inclusive), and a second, "control" group with low hyperopia (< or = +3.5 D). Cycloplegia eliminated the variable accommodation of infants. The myopic group showed a significant emmetropization of the mean spherical equivalent towards low hyperopia by 3 yr. There was no significant change in the control group's mean spherical equivalent power. Both groups showed a significant reduction in astigmatism with age. Analysis of the vertical and horizontal powers showed significant "emmetropization" of these meridians, in both groups, towards low hyperopia from 8.5 to 38.5 months. These meridional emmetropization changes were significant for both With-the-Rule and Against-the-Rule astigmatism.

Aging↗
PubMed2005

Reliability of Orbscan II topography measurements in relation to refractive status.

PURPOSE: To investigate the reliability of corneal topography measurements using the Orbscan II topography system (Bausch & Lomb) not only referring to a normal cohort but also to different refractive conditions. SETTING: Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany. METHODS: Eighty patients (mean age 46.4 +/- 19.0 years) were assigned to 4 refractive groups (Group A: emmetropia (n=20); Group B: astigmatism (n=20) (-1.98 +/- 1.77 diopters [D]); Group C: hyperopia (n=20) (+4.84 +/- 1.6 D); Group D: myopia (n=20) (-9.64 +/- 3.79 D). Three measurements were performed in a series. Thirteen defined, standardized points of the entire cornea (apex, 3.0 mm, 5.0 mm, and 7.0 mm zone) were evaluated for 3 different maps (anterior elevation, pachymetry, keratometry). RESULTS: In all 80 patients, the following mean values were found in relation to analyzed zones: with regard to the anterior elevation map, the values decreased from 5.53 microm (center) to -6.52 microm (7.0 mm zone), the corneal thickness increased from 549.41 microm to 638.63 microm peripheral and the keratometry from 43.86 D (apex) to 45.4 D (7.0 mm zone), respectively. Analysis of the 3 different maps in all 4 refraction groups showed a tendency toward an increase in SD from the center to the 7.0 mm zone for anterior elevation and pachymetry maps. For keratometry, however, the lowest SD was found in the 7.0 mm zone. In particular, patients with hyperopia showed significant differences (P<.01), compared with emmetropic patients; the SD was higher with regard to anterior elevation as well as keratometry in peripheral zones. Group B (astigmatism) showed significantly higher SD for anterior elevation in zones 3.0, 5.0, and 7.0 mm when compared with emmetropic patients. CONCLUSIONS: The repeated Orbscan II measurements showed SD in the micrometer range for anterior elevation and pachymetry but values between 0.48 D and 0.97 D for keratometric data. Patients with astigmatism and especially hyperopia showed significantly higher SD values in peripheral zones for anterior elevation and keratometry, indicating a lower reliability, compared with the emmetropic cohort. However, the different ages of the patients could also be a possible explanation for these findings. Therefore, the Orbscan II seems to be a predictable and useful device for measuring corneal topography.

Adolescent↗
PubMed1997

Local changes in eye growth induced by imposed local refractive error despite active accommodation.

We have tested whether defocus imposed on local retinal areas can produce local changes in eye growth, even if accommodation is available to clear part of the imposed defocus. Hemi-field lenses were attached to little leather hoods that were worn by young chickens from day 11-15 post-hatching. The lens segments defocused either the nasal or the temporal visual field, or covered the full field. We found that negative lenses (-7.5 D) were incompletely compensated in all three cases but caused significant myopia in the defocused parts of the visual field (differences to fellow eyes with normal vision: nasal visual field -3.13 +/- 1.56 D, P < 0.001; temporal visual field -4.02 +/- 1.38 D, P < 0.001; full field -3.82 +/- 2.48 D, P = 0.01). Myopia was not enhanced if the lenses covered the entire visual field. Positive lenses (+6.9 D) caused larger changes in refraction than negative lenses and, again, there was no significant difference in the amount of induced hyperopia in the nasal or temporal retina, or in the amount of hyperopia with full-field lenses (difference to fellow eyes with normal vision: nasal visual field +6.2 +/- 2.69 D, P < 0.001; temporal visual field +5.95 +/- 2.22 D, full field +7.22 +/- 2.44 D, P < 0.001). To compare the shapes of the excised eyes after lens treatment, we wrote a fully automated image processing program that traced their outlines in digitized video images. We found that the shapes of the eyes treated with positive lenses did scarcely differ from their fellow eyes with normal vision, indicating that hyperopia over this 4 day period was caused mostly by choroidal thickening. Full field negative lenses produced significant axial eye elongation; the effects of locally imposed defocus on eye shape were less conspicuous and were significant only in some areas. That local compensation of defocus was possible for both negative and positive lenses, suggests that the retina can recognize the sign of defocus without accommodation cues. Even more striking is that the presence of accommodation is apparently ignored since the drift in the plane of focus during accommodation does not disturb the compensation process. We re-analyze previous experimental results that argue for different mechanisms for deprivation myopia and lens-induced refractive errors. We propose that lens-induced refractive errors are compensated by similar retinal mechanisms as the ones proposed by Bartmann and Schaeffel [(1994). Vision Research, 34, pp. 873-876] to explain deprivation myopia. The proposed mechanisms can integrate with long time constants over the spatial frequency content in the retinal image while the viewing distances change, and control both choroidal thickening and scleral growth. However, it turns out that the compensation of imposed myopia cannot be explained if only one constant viewing is available. Apparently, there is more than a retinal blur detector to guide refractive development.

Accommodation, Ocular↗
PubMed1999

The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus).

We made a comprehensive study, involving observations on 45 marmosets, of the effects on ocular growth and refraction of wearing spectacles from the ages of 4-8 weeks. This period was within the period early in life when the eye grows rapidly and refraction changes from hyperopia to its adult value of modest myopia. In one series of experiments we studied the effect of lenses of powers -8, -4, +4 and +8D fitted monocularly. In another series of experiments we studied the effect of lenses of equal and opposite powers fitted binocularly, with the two eyes alternately occluded, so as to give an incentive to use both eyes, and in particular to accommodate, for at least part of each day, through the negative lens. The vitreous chamber of eyes that wore negative lenses of -4D or -8D, combined with alternate occlusion, elongated more rapidly than that of the fellow eye (negative lens eye-positive lens eye, 0.21 +/- 0.03 mm (S.E.M.), P < 0.01 and 0.25 +/- 0.06 mm, P < 0.05, respectively) and became relatively more myopic (2.8 +/- 0.26D, P < 0.01 and 2.4 +/- 0.61D, P < 0.05 respectively). Eyes that wore -4D lenses monocularly elongated more rapidly and became myopic than fellow eyes. Eyes that wore +4D or +8D lenses were less strongly affected: animals that wore +8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia (0.99 +/- 0.21D, P < 0.01), with the more hyperopic eyes also slightly shorter (0.09 +/- 0.05 mm) than their fellow eyes, but eyes wearing +4D lenses were not significantly different from their fellow eyes. Animals that wore -8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia after three weeks of lens-wear (0.85 +/- 0.26D, P < 0.05). These were the only eyes that responded in a non-compensatory direction to the optical challenge of spectacle wear, and we interpret this effect as one due to visual deprivation. After the removal of lenses, the degree of anisometropia slowly diminished in those groups of animals in which it had been induced, but in the three groups in which the largest effects had been produced by lens-wear the overall mean anisometropia (0.68 +/- 0.24D, P < 0.01) and vitreous chamber depth (VCD) discrepancy (0.09 +/- 0.03 mm, P < 0.01) were still significant at the end of the experiments, when the animals were 273 days old. The reduction of anisometropia in these groups was associated with an increase in the rate of elongation of the vitreous chamber in the eyes that had previously grown normally i.e. the less myopic eyes grew more rapidly than their fellow eyes: in the seven weeks following lens-wear these eyes became more myopic and longer than normal eyes (refraction P < 0.001; VCD P < 0.001). Control experiments showed that occlusion of one eye for 50% of the day had no effect on eye growth and refraction, and therefore that alternate occlusion itself had no effect.

Age Factors↗
PubMed1998

Ocular status of boys with fragile X syndrome: a prospective study.

PURPOSE: The purpose of this study was to determine whether the high rates of ocular problems described in previous retrospective reports of individuals with fragile X syndrome were present in a prospective sample of young boys. Fragile X syndrome is currently considered the leading hereditary cause of mental retardation, with prevalence estimates of 1:2500 to 1:5000 males. METHODS: Forty-eight boys with fragile X syndrome between the ages of 2.5 and 11 years were evaluated for ocular abnormalities. They received complete ophthalmic evaluations including assessment of visual acuity, cycloplegic refraction, ocular motility assessment, and dilated fundus examination. RESULTS: Approximately 25% of the children had clinically significant ocular findings that included refractive errors (17%, primarily hyperopia and astigmatism) and strabismus (8%). Of the 42 children with quantifiable visual acuities, only 1 child, with diagnoses of nystagmus and hyperopia, had a Snellen visual acuity that was not within normal limits for his age. Three of the 5 children with gross measures of visual acuity had clinically significant findings: 2 had hyperopia greater than 3.5 diopters and 1 had esotropia. The other 2 children with gross measures of acuity and the 1 child without visual acuity assessment had cycloplegic refractions of +1.25 to +1.5 and ocular motility appeared normal. CONCLUSIONS: These results suggest that previous reports of high rates of vision problems, particularly strabismus, in boys with fragile X syndrome may have resulted from selection bias. Although we did observe a higher prevalence of strabismus than that found in the general population (8% vs 0.5% to 1%), the proportion of children having strabismus in our sample was much smaller than that reported in other studies of children with fragile X syndrome (30% to 40%). However, 17% of the sample did have significant refractive errors. In addition to evaluating the ocular motility of children with fragile X syndrome, cycloplegic refraction should also be performed to determine whether refractive problems are present.

Child↗
PubMed1999

Refractive errors in children with cerebral palsy, psychomotor retardation, and other non-cerebral palsy neuromotor disabilities.

The aim of this study was to analyse the refractive state of four different groups of children: those with spastic cerebral palsy (CP), aged between 7 and 81 months (N=50); psychomotor retardation, aged between 19 and 70 months (N=16); other neuromotor dysfunctions, aged between 12 and 75 months (N=37); and without psychomotor retardation, aged between 9 and 73 months (N=181). Refractive errors were determined using cycloplegic retinoscopy and non-cycloplegic retinoscopy (Mohindra's technique). We found higher percentages of hyperopia, tendency toward hyperopia, and other refractive anomalies in all the pathological groups of children than in the non-pathological control groups. Children from both the non-CP pathological control group and the group with psychomotor retardation had similar or even higher levels of hyperopia than children from the group with spastic CP. Our results in different age groups indicate a less effective normal emmetropization course in all the pathological groups of children studied. The correction of refractive errors is needed in these children before the end of the neural plasticity period.

Cerebral Palsy↗
PubMed2004

Inhibitory effects of apomorphine and atropine and their combination on myopia in chicks.

PURPOSE: The inhibitory effect of apomorphine on form-deprivation myopia implies a role for dopaminergic pathways in eye growth; however, the effect of apomorphine on lens-induced changes has not been studied. Our study filled this deficiency. After establishing that apomorphine inhibited lens-induced myopia, we investigated whether apomorphine and atropine acted sequentially via the same control pathway or via different parallel pathways. METHODS: This study, conducted in 8-day-old chicks, was comprised of two parts: (1) a comparative study of apomorphine's effect on lens-induced myopia (-15 D), form-deprivation myopia (diffusers), and lens-induced hyperopia (+15 D) and (2) a study of the interacting effects of apomorphine and atropine on lens-induced myopia and form-deprivation myopia. In the first part, dH2O and six apomorphine doses (8 pmole to 800 nmole in log10 steps) were given as 10-microL intravitreal injections in combination with the above visual treatments. Apomorphine was used alone or given with atropine in the second part, which included four drug treatment groups: (1) control (dH2O); (2) 80 pmole of apomorphine; (3) 18 nmole of atropine; and (4) apomorphine + atropine. Additional dH2O injections were used to equalize the number of injections across groups. After 4.5 days of treatment, refractive errors and axial ocular dimensions were measured. RESULTS: The myopic shifts and axial elongation typical of lens-induced myopia (-15 D lens wear) were inhibited to maxima of 43% (4.5 D) and 52% (0.17 mm) by apomorphine, which, in contrast, enhanced lens-induced hyperopia (refractive error: 114%, 1.55 D; axial length: 134%, 0.16 mm). Inhibitory effects of apomorphine on lens-induced myopia were observed at doses > or = 80 pmole, whereas the doses required to enhance lens-induced hyperopia were 2 log10 units higher. Only a weak inhibitory effect of apomorphine on form-deprivation myopia was observed. Although both apomorphine and atropine inhibited lens-induced myopia, atropine was slightly more effective for the doses compared (refractive error, 53% cf. 32%), and the effect of the combination was not significantly greater than that of atropine alone (refractive error, 59% cf. 53%). CONCLUSIONS: Apomorphine inhibits both types of experimental myopia, which implies the involvement of dopaminergic mechanisms in both phenomena; likewise, cholinergic mechanisms are indicated by the inhibitory effects of atropine on both lens-induced myopia and form-deprivation myopia. We speculate that apomorphine and atropine act at different sites on a common control pathway because the combined effect of apomorphine and atropine was no more than atropine alone.

Animals↗