Amblyopia: etiology, detection, and treatment.

Amblyopia is a preventable cause of visual loss in children that may be permanent unless it is detected and treated early. It may be caused by strabismus, refractive errors, or cataracts. Primary strabismus may lead to loss of vision from amblyopia and the loss of binocularity. Secondary strabismus may be a sign of primary visual loss in one or both eyes. The most serious disorder that may present as secondary strabismus is retinoblastoma. It is imperative to detect retinoblastoma early because of its morbidity and mortality. Amblyopia is detected by assessing the visual acuity of each eye. Strabismus is detected by using the corneal light reflex test and the cover test. Focusing problems are detected by assessing the visual acuity and the red reflex. Cataracts and retinoblastoma may be detected by examining the red reflex of the eye. Treatment of amblyopia consists of correcting the amblyogenic factor with appropriate glasses and surgery. The preferred eye is patched with an adhesive patch to stimulate visual development in the amblyopic eye. The pediatrician plays a crucial role in the early detection of amblyopia, strabismus, and cataracts. The key to successful visual outcome is early recognition by the pediatrician, referral to the pediatric ophthalmologist, and prompt treatment.     

Children at risk of developing amblyopia: When to refer for an eye examination

Amblyopia is a sensory vision deficit that may be detected, diagnosed and treated best during the early stages of visual development. Only a small percentage of the paediatric population receive oculovisual examinations during this critical period of development even though such care is often free and easily accessible. Vision screening programs exist in certain states in the United States and in several European countries. Unfortunately, these programs are rarely implemented in Canada because of limited resources.Alternatively, screening at-risk infants may be more efficient and cost-effective in the early detection of amblyopia. Educating and training health care professionals, such as paediatricians, to recognize certain risk factors for amblyopia and encouraging early referral of the at-risk child to an eye care professional may prevent the development of amblyopia. The at-risk child has been defined to guide paediatricians and other primary health care professionals as to when to refer these children, the appropriate frequency of follow-up evaluations and the comanagement of compliance and treatment.     

VISION SCREENING OF FOUR-YEAR-OLD CHILDREN

Included in a general health control of an un-selected population of 2 447 four-year-old children, a vision screening was performed, using a visual acuity test (Marquez-Bostrom's hooks), cover test and Wirt Fly Stereo test. The screening could be carried out in 98% of the children. 364 children (15.2%) were referred because of newly detected visual defects, and 358 children (15.0%) were professionally examined. Of these, 40.8% had a visual acuity of ≤0.6 and 5.9% of ≤0.1. Functional amblyopia was found in 12.3% and manifest strabismus in 10.3%, The main error of refraction was hyperopia (≥ 2.5 D), diagnosed in 28.5%, while myopia was infrequent, 3.9%. The children examined by the ophthalmologist were also classified into four groups, according to their need of professional care, where group 0 means overreferral and groups 2–3 represent “significant eye disorders”, in need of ophthalmological treatment and/or observation. Overreferral was found in 16.5% and significant eye disorders in 43%. With the visual acuity test, 97% of the children with eye disorders were detected. Retesting children, who failed the tests, reduced the over-referral from 39.5% to 12.5% (p<0.001). By lowering the passing standards of the visual acuity test, still fewer children would have been overreferred, but, at the same time, 1/5 of children needing treatment would then have remained undiscovered. Including children already under professional care, the prevalence of strabismus in this unselected material of 4-year-old children was just below 4%, and the need for corrective glasses around 8%. Children reported to have family eye disorders, partus complications or present eye complaints were in the risk zone for suffering significant eye disorders, but this information from the parents was not sufficiently selective to be of practical value as a screening method. A small control group of 73 children and a follow-up of 479 children at school 3 years later, revealed that no children with functional amblyopia were missed at the screening test.     

Services provided for preschool-aged children with suspected amblyopia

BACKGROUND: Little is known about the pattern and variation of care offered to preschool-aged children who have had an abnormal vision screening test. PURPOSE: To evaluate the variations in pediatric eye care services and availability of optometrists and ophthalmologists for preschool-aged patients, referral patterns, and barriers to providing care as perceived by eye care specialists. METHODS: A survey was mailed to 542 ophthalmologists and a random sample of 501 optometrists actively practicing in Michigan. RESULTS: The response rate was 65% (optometrists, 75%; ophthalmologists, 57%). More optometrists than ophthalmologists evaluated preschool-aged children (97% vs 79%; P < .001). Of these, most managed amblyopia (80% vs 77%; P = .372) and strabismus (89% vs 80%; P = .002) themselves. Fewer optometrists than ophthalmologists dilated eyes routinely during the first evaluation of a preschool-aged child (39% vs 93%; P < .001). The leading barrier to care for preschool-aged children reported by both optometrists and ophthalmologists was difficulty of the examination (25% vs 23%; P = .501). Optometrists reported that most of their patients were referred from community-based screening programs or by parent self-referral. Ophthalmologists reported that most of their preschool-aged patients were referred from primary care providers. CONCLUSIONS: There are different sources of referrals for optometrists and ophthalmologists. Although most eye care specialists treat amblyopia, the types of care offered by optometrists and ophthalmologists differ. Future studies should address the impact that these patterns have on outcomes and cost. The results of these studies should be shared with those responsible for screening.     

Comparison of monocular autorefraction to comprehensive eye examinations in preschool-aged and younger children

BACKGROUND: Monocular autorefraction is a newly available technology for vision screening that has been advocated to test young children. Such devices automatically determine the refractive state of each eye, but cannot directly detect amblyopia or strabismus. OBJECTIVE: To compare the results of a commercially available monocular autorefractor (SureSight; Welch Allyn Medical Products, Skaneateles Falls, NY) with findings from a comprehensive eye examination for significant refractive error, strabismus, and amblyopia. METHODS: Children 5 years and younger who were new patients attending a pediatric ophthalmology clinic were tested with the monocular autorefractor without dilation and underwent a comprehensive eye examination that included dilation. MAIN OUTCOME MEASURES: The proportion of children who could be tested and the sensitivity and specificity of the screening. RESULTS: Of the 170 children enrolled (age, <3 years, n = 80; age range, 3-5 years, n = 90), 36% had abnormal eye examination findings. Most (84%) children 3 years or older could be tested compared with 49% of the children younger than 3 years (P<.001). Among those who were testable, for children younger than 3 years the sensitivity was 80% (95% confidence interval [CI], 44%-97%) and the specificity was 41% (95% CI, 24%-61%). For children aged 3 to 5 years, the sensitivity was 88% (95% CI, 68%-97%) and the specificity was 58% (95% CI, 43%-71%). CONCLUSIONS: Our findings suggest that screening children aged 3 to 5 years with monocular autorefraction would identify most cases of visual impairment but would be associated with many false-positive results. For children younger than 3 years, testability was low and results were nonspecific.     

Outcome of treatment of marked ametropia without strabismus following screening and diagnosis before the age of three

Following early treatment of 39 consecutive cases with marked ametropia without strabismus, diagnosed by screening at the age of one to two and a half years, residual amblyopia was found in 20 (51%), including six (15%) with bilateral amblyopia, but with relatively good visual acuity in at least one eye. Anisometropia showed the highest rate of residual amblyopia. The main changes in refraction that occurred from the age of screening to the age of seven years was myopisation, especially in hypermetropic eyes without amblyopia. Heterotropia, always intermittent, developed in six of the 39 cases. Full stereopsis could be found in eight cases only, all without amblyopia. The majority, whether amblyopic or not, had partial binocular functions but four cases, all amblyopic, had none.     

Experience in the early detection of strabismus in child day care centers. Value in the prevention of amblyopia in young children

A screening for early detection of strabismus in infants and young children attending day care centers in the town of Lyons was conducted during one year (1986): 838 children (3 month to 3 year old) were screened. A defective vision was found in 17 children (2%). Such early screening of strabismus, easy to realize and well accepted by the parents, is of great interest since it allows early detection and treatment with a maximum chance of complete recovery before starting primary school.     

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.     

Association between fixation preference testing and strabismic pseudoamblyopia

PURPOSE: Fixation preference testing is the mainstay of clinical diagnosis of strabismic amblyopia in preverbal children and infants. The purpose of this study is to evaluate the strength of the association between fixation preference and strabismic amblyopia. PATIENTS AND METHODS: Eighty patients (3 to 8.3 years) with manifest strabismus and the capability to cooperate with a Snellen acuity test were prospectively examined. Thirty patients were diagnosed as having partially accommodative esotropia, 15 as having congenital esotropia, 15 as having primary acquired esotropia, 15 as having congenital exotropia, and 5 as having hypertropia. Visual acuity levels were measured using a Snellen E-chart. Fixation preference was evaluated and graded from 0 (free alternation) to 3 (strong uniocular fixation). At the end, we compared visual acuity and the grade of fixation preference. Amblyopia was defined as a difference of two or more Snellen lines between the two eyes. RESULTS: Sixty patients (75%) had strong uniocular fixation (grade 3). Of these patients, 50 (85%) had no amblyopia and only 10 had deep amblyopia. Ten patients (12.5%) had moderate fixation (grades 1 and 2). Of these patients, five (50%) had no amblyopia and five had moderate amblyopia. Ten patients (12.5%) had free alternation (grade 0). These patients had equal vision. CONCLUSION: Treatment of strabismic amblyopia on the basis that the sound eye will show strong fixation preference can be hazardous. Fixation preference could be a severe form of eye dominance, and better methods for testing visual acuity in preverbal children are required.     

Use of photoscreening for children's vision screening

This statement asserts that all children should be screened for risk factors associated with amblyopia. Guidelines are suggested for the use of photoscreening as a technique for the detection of amblyopia and strabismus in children of various age groups. The American Academy of Pediatrics favors additional research of the efficacy and cost-effectiveness of photoscreening as a vision screening tool.     

Amblyopia: definition, classification, diagnosis, and management considerations for pediatricians, family physicians, and general practitioners

Amblyopia is a reduction in the quality of central, corrected vision resulting from a disturbance in retinal image formation during the first decade of human life. Although the neurophysiology and neuropathology of amblyopia are now better understood than in the past, treatment has not changed significantly in more than 200 years. The earlier amblyopia is detected, the shorter the duration of treatment required to reduce its severity. The mainstay of treatment still consists of forcing the use of the amblyopic eye, most often by occlusion of the sound eye. Complications of treatment include occlusion amblyopia and induction of strabismus in straight-eyed patients.     

Faktoren der Früherkennung visueller Entwicklungsstörungen bei 3-jährigen Kindergartenkindern

Purpose and Background

In the ‘Tuebingen Kindergarten Study’, an orthoptic screening program for amblyopia in 3-year-olds was evaluated. In the retrospective analysis presented here, the association between a child’s history—especially participation in regular preventive care examinations (U4 to U7)—and time of detection of target diseases was investigated.

Methods and Subjects

Parents of three children groups were interviewed by telephone. Group 1 consisted of 21 children already treated for amblyopia before orthoptic screening, group 2 of 26 children with target conditions newly detected by orthoptic screening, and group 3 of 32 children with newly detected moderate ametropia. The groups were tested for differences in history and utilisation/results of regular screenings.

Results

77–90% of all children had positive family histories. Participation in regular screenings ranged from 82% to 92%. There were no significant differences between the groups. Nearly 90% of parents from groups 2 and 3 had not heard of amblyopia before orthoptic screening. One child was referred after preventive care examinations.

Conclusions

Regular preventive care examinations contributed little to the detection of amblyopia. The strong authority of the paediatrician should be exerted for early education of parents.     

Unexpected good results after therapy for anisometropic amblyopia associated with unilateral peripapillary myelinated nerve fibers

Unilateral extensive myelination of the peripapillary nerve fibers may be associated with anisometropic myopia, strabismus, and reduced vision. Despite aggressive occlusion of the normal eye, visual results are often disappointing, presumably due to associated structural abnormalities in the macula which limit visual potential. We report two cases, a 21-month-old child and a 23-month-old child with unilateral peripapillary myelination, ipsilateral high myopia, and dense amblyopia. Despite an abnormal macular reflex in each child, vision improved to 20/30 in one child and 20/50 in the other child after occlusion therapy. Visual results in these patients suggest that aggressive amblyopia therapy should be considered in patients with anisometropic amblyopia associated with extensive myelination continuous with the optic nerve. Not all patients with unilateral peripapillary myelinated nerve fibers, an abnormal macula, and myopia will have refractory amblyopia.     

Strabismus in very low birth weight and/or very preterm children: Discrepancy between age of onset and start of treatment

Very low birth weight (VLBW; less than 1500 g) and/or very preterm children are at risk for strabismus. However, the age of onset of strabismus is still unknown. The present study reports on the frequency of strabismus in 450 5-year-old children born with a birth weight of less then 1500 g and/or with a gestational age below 32 weeks. The age at which strabismus was initially diagnosed was determined retrospectively. At 5 years of age 65 of the atrisk children (14.4%) presented with strabismus. Fifteen of them (3%) had at that age not been referred to or treated by an ophthalmologist. At 3 years of age only 28 strabismic children were being treated; 7 at-risk children (2%) had been treated for strabismus before the end of the 1st year. These results were compared to those from a second study in which eye alignment was longitudinally examined in 194 VLBW children from 6 weeks until 12 months of (corrected) age and additionally in 65 of these children at the age of 2.5 years. At a first glance, the frequency of strabismus in the longitudinal study seemed rather stable during the first 2.5 years of life, with values varying between 14% and 18%. However, only a small percentage of misalignments which were noted at 6 weeks of age persisted until 2.5 years. On the other hand, if children had a misalignment at 9 months, strabismus was still present when they were reexamined at 1 and at 2.5 years of age. In order to prevent the rather high incidence of untreated strabismus, screening programmes for atrisk children should focus on diagnosing strabismus at 9 months of (corrected) age. Because strabismus can also develop after this age, it is important to re-examine ocular alignment at later ages.Conclusion Present medical care is not sufficient for early detection and treatment of strabismus in at-risk children. Our results suggest that the optimal screening age for early detection of persistent strabismus in VLBW children is at 9 months of age. Because strabismus can also develop after this age, it is important to repeat examination of visual functions in at risk-children at regular intervals after 1 year of age.     

Identifying infants and young children with developmental disorders in the medical home: an algorithm for developmental surveillance and screening

Early identification of developmental disorders is critical to the well-being of children and their families. It is an integral function of the primary care medical home and an appropriate responsibility of all pediatric health care professionals. This statement provides an algorithm as a strategy to support health care professionals in developing a pattern and practice for addressing developmental concerns in children from birth through 3 years of age. The authors recommend that developmental surveillance be incorporated at every well-child preventive care visit. Any concerns raised during surveillance should be promptly addressed with standardized developmental screening tests. In addition, screening tests should be administered regularly at the 9-, 18-, and 30-month visits. (Because the 30-month visit is not yet a part of the preventive care system and is often not reimbursable by third-party payers at this time, developmental screening can be performed at 24 months of age. In addition, because the frequency of regular pediatric visits decreases after 24 months of age, a pediatrician who expects that his or her patients will have difficulty attending a 30-month visit should conduct screening during the 24-month visit.) The early identification of developmental problems should lead to further developmental and medical evaluation, diagnosis, and treatment, including early developmental intervention. Children diagnosed with developmental disorders should be identified as children with special health care needs, and chronic-condition management should be initiated. Identification of a developmental disorder and its underlying etiology may also drive a range of treatment planning, from medical treatment of the child to family planning for his or her parents.     

Strabismus und Amblyopie

Not detecting visual problems or diagnosing them too late may lead to major consequences: amblyopia of one eye and thus lack of a “substitute eye” (after loss of the healthy eye), poor binocular function, limited choice of occupation. Obvious pathologic findings such as drooping eyelids with pupillary occlusion, possible strabismus or nystagmus should prompt further ophthalmologic evaluation. The sooner strabismus is detected, and the earlier it is treated (by spectacles or occlusion, for example), the better will be the chances to develop good visual acuity and useful binocular function. Pediatricians do have a key role in appropiate screening and collaboration with ophthalmologists.     

Sequelae of retinopathy of prematurity

Retinopathy of prematurity (ROP) affects preterm infants. Here we describe its revised classification and the amended treatment indications which recommend treatment at an earlier ROP stage known as ‘prethreshold’. The three global ROP epidemics are briefly discussed. ROP sequelae are discussed under four headings: visual functions, strabismus, refractive state and the effect of ROP on the structures of the eye. While ROP is potentially blinding, in general, ophthalmic outcome is similar for preterm children who did not develop ROP or in whom this was only mild (stages 1 & 2). In the main their deficits are not functionally disabling, although treatment, to correct a refractive error, strabismus or amblyopia, may be required. The outcome for children who had severe, potentially sight-threatening ROP (stages 3–5 and prethreshold) is far more variable and in a proportion of children is disabling and even blinding. Whether children who had ROP need follow-up is discussed. Finally the future role of anti-VEGF treatment is considered.     

Psychosocial aspects of the treatment of phenylketonuria

The psychosocial aspects of phenylketonuria (PKU) were investigated retrospectively in the families of 25 children and adolescents with classical PKU. With the help of a semistructurated questionnaire the parents were asked in interviews what impact the birth, the diagnosis of PKU in their child and the treatment itself had on them. 19 of the children had been detected by newborn screening and given early treatment. With one exception they all showed adequate intellectual development. Six other children were diagnosed late and only three of them had been given dietary treatment with some degree of success. Many of the parents reacted with shock and disbelief after being informed that their child was abnormal. In many ways the parents expressed retrospectively the wish that they had been better informed about their childs disease and had more intensive support from the medical professionals. They believed that with these prerequisites they would have been more competent in the case of their children. The data demonstrate the necessity of psychological care for the entire family of the chronically sick child.     

北京市托幼园（所）5522名学龄前儿童视觉状况调查

为了解北京市托幼园（所）学龄前儿童视觉发育状况及弱视等病的流行特点，对北京市托幼园（所）５５２２名学龄前儿童进行了抽样调查。结果：３岁、４岁、５岁、６岁和７岁组儿童视力１．０检出率分别为６４．５４％、６４．９５％、７３．０８％、８２．６２％和９６．７７％，农村最高，城镇其次，城市最低；屈光不正以远视为主；显性斜视的检出率为１．５４％，隐性斜视为４０．２５％；弱视发生率为２．９９％，以屈光不正和屈光参差性弱视占全部弱视的６６．０６％，斜视性弱视占１５．１５％。屈光不正、斜视和弱视儿童的立体视率明显低于正常，χ２＝１７．５６，Ｐ＜０．０１。提示：学龄前儿童视力随年龄增长而增加，屈光不正、斜视和弱视是儿童期影响正常视功能形成的主要因素，应加强监测与矫治。