Risk factors for strabismus in children born before 32 weeks' gestation

Prevalence of strabismus in premature infants in an age-related perspective

THE AIM

was to investigate the prevalence of strabismus in premature infants; to identify diagnostic indicators for predicting strabismus at the age of 3-8 years.

METHODS

The material was the data of 84 premature infants who underwent ophthalmological examination at the age of 6 months - 3 years and again - at 3-8 years. All children underwent ophthalmic examination for retinopathy of prematurity (ROP) in infancy.

RESULTS

An increase in the frequency of strabismus occurrence among preterm infants was observed in 3-8 years compared to the data from 6 months - 3 years - from 13.3% to 20.0% in children without ROP, from 5.9% to 23.5% in children with self-resolving ROP, from 22.7% to 45.5% in children with ROP after laser retinal photocoagulation. The presence of strabismus and structural changes of eye at ages 6 months - 3 years increase the risk of strabismus at ages 3-8 years, OR = 6.5 (95% CI 3.8-11.3), (p < 0.001); OR = 4.2 (95% CI 2.8-6.2), (p = 0.005). The increase in the risk of developing strabismus at ages 3-8 years is associated with the presence of anisometropia, (p = 0.047), amblyopia, (p < 0.05). Children with higher visual acuity at ages 3-8 years have a decreased risk of strabismus, (p < 0.05).

CONCLUSIONS

The frequency of strabismus occurrence among preterm infants has increased by ages 3-8 years. Strabismus, structural changes of eye at ages 6 months - 3 years increases the risk of strabismus at ages 3-8 years. Anisometropia and amblyopia increase in the risk of strabismus, higher visual acuity decreases risk of strabismus.

Long-term outcomes of type 1 retinopathy of prematurity following monotherapy with bevacizumab: a Canadian experience

OBJECTIVE

To report long-term structural, visual, and refractive outcomes after monotherapy with intravitreal bevacizumab injection.

DESIGN

Cohort retrospective chart review.

PARTICIPANTS

A total of 56 premature infants with type 1 retinopathy of prematurity.

METHODS

This is a chart review at 2 Canadian institutions. Inclusion criteria were single injection of 0.625 mg  intravitreal bevacizumab and minimum age at last follow-up of 3 years. Primary outcome was retinal structure. Secondary outcomes were refractive error in spherical equivalent, monocular visual acuity, strabismus, and amblyopia.

RESULTS

Fifty-six infants (101 eyes) met inclusion criteria. Mean birth weight was 707 ± 178 g (range, 420-1520 g). Mean gestational age was 25.0 ± 1.3 weeks (range, 22.9-29.7 weeks). Twenty-four eyes were in zone I (24%) and 77 in zone II (76%). Mean postmenstrual age at treatment was 36.9 ± 2.1 weeks (range, 32.8-42.0 weeks). At a mean age of 5.4 ± 1.6 years (range, 3.0-8.0 years), all eyes had a favourable structural outcome with no reactivation requiring treatment. Mean monocular visual acuity was 0.29 ± 0.27 logMAR (range, 0.0-1.3 logMAR; 89 of 101 eyes). Mean spherical equivalent was -1.98 ± 4.91 D (range, -16.63 to +5.38 D; 101 of 101 eyes). Prevalence of emmetropia (>-1.0 to ≤1 D) was 43.6%; low myopia (≥1.0 to <5 D) was 17.8%; high myopia (≥5 to <8 D) was 8.9 %; very high myopia (≥8.0 D) was 12.9%; and hyperopia (>1 D) was 16.8%. Twelve children (23%) had amblyopia, and 17 (32%) developed strabismus.

CONCLUSIONS

All patients demonstrated a favourable structural outcome with a single bevacizumab injection without the need for additional laser. We suggest regular monitoring following regression of acute retinopathy of prematurity as an alternative to universal, preplanned delayed prophylactic laser treatment. Future studies to evaluate other aspects of visual function are needed.

Strabismus in Retinopathy of Prematurity: Risk Factors and the Effect of Macular Ectopia

Objectives

This study aimed to examine factors associated with strabismus in patients with retinopathy of prematurity (ROP) and the relationship between strabismus and macular ectopia.

Materials and Methods

Patients with ROP were divided into three groups: Group 1, patients with spontaneous regression (n=45); Group 2, patients who received laser treatment (n=70); and Group 3, patients who underwent surgical treatment (n=91). Rates of anisometropia, amblyopia, nystagmus, macular ectopia, and retinal pathologies were evaluated and their impacts on strabismus development were determined. Disc-to-fovea distance (DFD) was measured from color fundus photographs and the correlation of macular ectopia with severity of strabismus was evaluated.

Results

A total of 206 patients were included. Rates of anisometropia, amblyopia, nystagmus, macular ectopia, retinal pathologies causing vision loss, and strabismus were higher in Group 3 (p=0.0001) and correlated with higher stages of ROP (p=0.0001). Macular ectopia (p=0.005), retinal pathologies (p=0.005), and amblyopia (p=0.012) had the strongest impact on strabismus development in ROP patients. DFD and strabismus severity were not significantly correlated (p=0.364). Mean visual acuity (VA) was significantly higher in orthophoric patients compared to those with esotropia and exotropia (p=0.027). Esotropic patients had lower VA compared to patients with exotropia, but this finding was not statistically significant (p=0.729).

Conclusion

Presence of macular ectopia, retinal pathologies, and amblyopia were the most strongly correlated risk factors for strabismus development in ROP patients. DFD was not associated with severity of strabismus. Exotropia was mostly related to higher DFD and a possible relationship between esotropia and lower VA was observed.

Early childhood eye diseases and perinatal risk factors: potential of record linkage between current information flows

BACKGROUND

The aim of this study was to analyze the occurrence of specific maternal, obstetric or neonatal factors, by performing a comparison between children with refractive error, strabismus and/or amblyopia (cases) and unaffected children (controls) in the province of Trento (North-East Italy).

METHODS

In 2012-2014, 14,346 children attending the second year of nursery school were assessed through the preschool orthoptic screening scheme (covering 91% of the preschool population). Record linkage was performed between the orthoptic screening database and birth records (birth confirmation certificate database) for the corresponding birth cohorts (2008-2010), to examine specific maternal factors (age, smoking, nationality/race), obstetric factors (type of delivery) and neonatal factors (gestational age, weight at birth, Apgar Score, congenital birth defects, hospitalization at birth). The correlations were investigated using univariate and multivariate analysis in accordance with the logistic regression method.

RESULTS

During orthoptic screening, 6.4% of children were found to have at least one refractive error, with astigmatism being the most common condition (5.1%). 1.9% of children were found to have strabismus and 1.8% amblyopia. Multivariate logistic regression analysis showed that the risk of developing a refractive error is associated with: maternal age ≥45 years, foreign nationality, vacuum-assisted delivery and neonatal weight <1500 grams. An excessive risk of strabismus was observed in children whose mother had smoked during pregnancy (adjusted OR=1.64).

CONCLUSIONS

Preschool orthoptic screening is a well-consolidated practice in the province of Trento, with adhesion values consistently over 90%. Studies of this type show the potential of record linkage between current information flows.

Altered interhemispheric functional connectivity in patients with comitant exotropia before and after surgery: a resting-state fMRI study

Purpose

To assess the interhemispheric homotopic connectivity alterations in patients with comitant exotropia (CE) before and after surgery, using resting-state functional magnetic resonance imaging (rs-fMRI) with voxel-mirrored homotopic connectivity (VMHC).

Methods

Thirty-four patients with CE and twenty-four well-matched healthy controls (HCs) were enrolled to undergo a preoperative rs-fMRI scan. The rs-fMRI scan was performed again in twenty-four patients 1 month after surgery. The VMHC method was applied to evaluate the group differences of interhemispheric functional connectivity. The correlations between VMHC values and clinical variables were analyzed in the patient group.

Results

Compared with HCs, 34 patients with CE showed significantly increased VMHC values in occipital lobe (cuneus/superior occipital gyrus/middle occipital gyrus/calcarine), cerebellar area 8/cerebellar Crus1 area, and cerebellar Crus1 area. In CE group, VMHC in the cuneus was positively correlated with stereoacuity (r = 0.417, P = 0.014), meanwhile VMHC in the cerebellar Crus1 area was positively correlated with stereoacuity (r = 0.395, P = 0.021). One month after surgery, the 24 CE patients with follow-up showed decreased VMHC values in the cuneus and superior occipital gyrus compared with preoperative collection, meanwhile, non-significant difference compared with HCs.

Conclusion

Our study revealed the interhemispheric homotopic connectivity changes of patients with CE in the occipital lobe and cerebellum before and after surgery. The findings may provide a new perspective for the neurological alterations of CE.

Comitant strabismus etiology: extraocular muscle integrity and central nervous system involvement-a narrative review

Strabismus is not a condition in itself but the consequence of an underlying problem. Eye misalignment can be caused by disease, injury, and/or abnormalities in any of the structures and processes involved in visual perception and oculomotor control, from the extraocular muscles and their innervations to the oculomotor and visual processing areas in the brain. A small percentage of all strabismus cases are the consequence of well-described genetic syndromes, acquired insult, or disease affecting the extraocular muscles (EOMs) or their innervations. We will refer to them as strabismus of peripheral origin since their etiology lies in the peripheral nervous system. However, in most strabismus cases, that is comitant, non-restrictive, non-paralytic strabismus, the EOMs and their innervations function properly. These cases are not related to specific syndromes and their precise causes remain poorly understood. They are generally believed to be caused by deficits in the central neural pathways involved in visual perception and oculomotor control. Therefore, we will refer to them as central strabismus. The goal of this narrative review is to discuss the possible causes behind this particular type of eye misalignment and to raise awareness among eyecare professionals about the important role the central nervous system plays in strabismus etiology, and the subsequent implications regarding its treatment. A non-systematic search was conducted using PubMed, Medline, Cochrane, and Google Scholar databases with the keywords "origins," "causes," and "etiology" combined with "strabismus." A snowball approach was also used to find relevant references. In the following article, we will first describe EOM integrity in central strabismus; next, we will address numerous reasons that support the idea of central nervous system (CNS) involvement in the origin of the deviation, followed by listing several possible central causes of the ocular misalignment. Finally, we will discuss the implications CNS etiology has on strabismus treatment.

Screening, Diagnosis, and Treatment of Pediatric Ocular Diseases

Vision is an important aspect of a child's quality of life and intellectual, social, and emotional development. Disruptions to vision during infancy and early childhood can cause lifelong vision impairment or blindness. However, early identification and treatment of eye disease can prevent loss of sight and its consequent long-term effects. Therefore, screening guidelines exist to guide physicians in detecting the most common threats to sight in the different stages of infancy and childhood. This review describes common causes of pediatric vision impairment, the recommended screening guidelines for diagnosing them, and current treatment modalities.

Late sequelae of retinopathy of prematurity in adolescence and adulthood

This article provides information about late complications of retinopathy of prematurity (ROP), especially seen in adolescence and adulthood. The majority of ROP patients recover without complications and treatment, but severe ROP cases should be properly treated. Both prematurity itself and the treatment of ROP cause some changes in the anterior (refractive changes, cataract, and glaucoma) and posterior segments (tractional, rhegmatogenous and exudative retinal detachment, vitreous hemorrhage, etc.,) of the eye and predispose to significant lifelong complications. Awareness of these late complications can minimize severe vision loss with proper follow-up and appropriate treatment. Therefore, life-long ophthalmological follow-up is mandatory in all prematures with the diagnosis of ROP.

Profile of infantile strabismus at a tertiary eye care center in India

Purpose

To study the profile, risk factors, and management outcomes of infantile strabismus at a tertiary eye care center.

Methods

We prospectively analyzed the data of infants (children less than 1 year of age) who presented at our institute from August 2018 to December 2019. We excluded infants who did not complete a minimum follow-up of 6 months. Detailed meticulous history based on a set of standardized questionnaires was obtained and a comprehensive ophthalmological examination of the child was performed. Data were collected regarding refractive error (astigmatism; myopia; hyperopia; anisometropia [<1.0 DS or >1.0 DS]; astigmatism [<1.0 DS or >1.0 DS]) and the type of strabismus.

Results

During this period, we saw 4,773 infants, out of which 123 infants were diagnosed to have infantile-onset strabismus (hospital prevalence of 2.6%). Boys and girls were equally affected. Sixty-two patients had esotropia, 37 had exotropia, 2 had hypotropia, and 22 had pseudo strabismus. Prematurity, hypermetropia, and anisometropia had increased odds of developing esotropia, whereas delivery by cesarean section, delayed cry at birth, infantile seizures, parental consanguinity, delayed development of milestones, and myopia had increased odds of developing exotropia. Twenty-nine patients underwent a surgical correction. The mean deviation at the first visit was 42.59 ± 15.40 PD and 8.25 ± 12.70 PD at the last visit. For all patients who underwent a squint surgery, the change in ocular deviation was clinically and statistically significant (P-value <0.0001, paired t-test).

Conclusion

The hospital prevalence of infantile strabismus in our cohort was found to be 2.6%. Our study suggests that esotropia is two-fold more common in our cohort as compared to exotropia. Further, our study highlights risk factors for the development of strabismus in infancy, which must be kept in mind and awareness must be created among pediatricians. Surgical correction should be considered early during the infantile period, because it may lead to promote the development of good binocular vision.

[Ocular abnormalities of children born prematurely at the Yaoundé Gynaeco-Obstetrics And Pediatric Hospital]

PURPOSE

To identify ocular abnormalities in premature children in order to treat reversible visual disorders and help prevent low vision and blindness in this population at risk.

METHODOLOGY

This was a cross-sectional, analytical study carried out from November 1, 2018 to July 31, 2019 at the Yaoundé Gyneco-Obstetric And Pediatric Hospital, including premature children, aged 3 to 15 years. The variables studied were age, sex, prenatal, birth and past ophthalmological history, visual acuity, oculomotor examination and fundus examination. For statistical analysis, we used the epi-info software 3.5.4, the Chi² test, odds ratio and a 95% confidence interval with a significance P<0.05.

RESULTS

Of the 50 patients examined, the mean age was 6.02 years±2.58. Of the 22 optically corrected patients, hyperopia and hyperopic astigmatism were predominant (70.5%) (n=31). Distance visual acuity, measured in 31 cooperative patients (62 eyes), was between 3/10 and 8/10 in 14 eyes (22.6%), and<3/10 in two eyes (3.2%). Strabismus was present in 21 patients (42%), of which 13 cases were esotropia (61.9%). Tropical endemic limbo-conjunctivitis was found in eight eyes (8%). There were no cases of retinopathy of prematurity. Very low birth weight (<1500g) and neonatal resuscitation were associated with strabismus.

CONCLUSION

Ocular abnormalities in preterm infants are dominated by strabismus, which is associated with very low birth weight and neonatal resuscitation.

An Opioid-free Anesthesia Protocol for Pediatric Strabismus Surgery: A Quality Improvement Project

Introduction:

This quality improvement (QI) project tracks a series of 2 Plan-Do-Study-Act (PDSA) cycles as we standardized and refined an ambulatory pediatric anesthesia strabismus protocol. We aimed to provide effective pain relief, reduce postoperative nausea and vomiting (PONV) rates, and be cost-efficient while minimizing perioperative opioids over 5 years.

Methods:

We used statistical process control (SPC) charts to analyze real-world data captured from the medical record. We chose the following outcome and process measures to evaluate effectiveness: postoperative morphine rescue rate, maximum pain score in the postanesthesia care unit (PACU), and PONV rescue rate. We also used 2 balancing measures: postoperative length of stay (LOS) and total anesthesia time. We standardized our anesthesia protocol for our first PDSA cycle (April 2017) by removing intraoperative intravenous acetaminophen and utilizing fentanyl only. For the second PDSA cycle (January 2019), we replaced intraoperative fentanyl with dexmedetomidine.

Results:

There was a total of 325 pediatric strabismus repair surgeries performed between April 2015 and July 2020. There was no special cause variation detected in the SPC charts for the family of measures chosen to measure effectiveness: postoperative morphine rescue rate, maximum pain score in the PACU, or the PONV rescue rate. The PONV rescue rate was 0 with the removal of opioids. Also, there was no special cause variation for the balancing measures: postoperative LOS or total anesthesia time.

Conclusions:

Throughout 2 PDSA cycles, this QI project enabled our team to standardize an opioid-free and cost-efficient anesthesia protocol for pediatric strabismus surgery over 5 years.

Clinical Spectrum of Ocular and Visual Dysfunction in Children with Periventricular Leukomalacia: A Need for an Interdisciplinary Approach

The study aimed to evaluate the ocular motility and visual and optic disc abnormalities in children diagnosed with periventricular leukomalacia (PVL). A retrospective analysis was performed on 51 consecutive children who had ophthalmic symptoms and were diagnosed with PVL by using magnetic resonance imaging. The patients were assessed for visual function, strabismus, cycloplegic refraction, fundus examination, and if appropriate, spectral-domain optical coherence tomography and visual field testing were applied. The primary outcome measures were the prevalence and visual and ocular motility dysfunctions. Mean age was 5.72 ± 2.6 years (range = 1–12), median birth weight was 2,740 g (range = 1,240–3,460), and median gestational age was 34 weeks (range = 28–38). In total, 21 patients (39.6%) had neurological deficit, 11 (21.5%) had intellectual disability, and 19 (37.2%) had no neurological symptom. In the spherical equivalent refractive error and cylinder power analysis, 10 patients had ≥3.0 D myopia, 15 had ≥3.0 D hyperopia, and eight had ≥2.50 D astigmatism. Thirteen (25.4%) children had a best-corrected visual acuity between 20/40 and 20/20 for Snellen card, while 9 (17.6%) had strabismic amblyopia and 6 (11.7%) had anisometropic amblyopia. Manifest strabismus was present in 35 patients (68.6%); of whom 12 had esotropia (23.5%), 16 had exotropia (31.3%) and 6 had vertical deviation (11.7%). Manifest or latent nystagmus was detected in 14 patients (27.4%). In 28 patients (54.9%), there was optic nerve abnormality. Two patients had hypoplastic disc, 14 had optic disc pallor, 7 had large cupping, and 5 had total optic atrophy. Six subjects underwent reliable visual field (VF) examinations, and all six had abnormal VFs, with inferior fields being most affected. Ocular motility disorders, optic nerve abnormalities, VF defects, and low visual acuity are common findings in this cohort of PVL patients and maybe the only presenting signs of the disease. The recognition of the visual disabilities and implementation of early rehabilitation may have a significant benefit in these children.

Assessment of Different Types of Strabismus Among Pediatric Patients in a Tertiary Hospital in Jeddah

Background Strabismus, also known as squint, is an ocular disorder in which the eyes do not align properly with each other when looking at an object. The estimated global prevalence of strabismus among children is between 1.3% and 5.7%. This study aimed to assess the various types of strabismus among pediatric patients in Jeddah, in the western region of Saudi Arabia. Methods The medical records of 281 patients with strabismus aged ≤18 years, who presented to the pediatric ophthalmology clinic in King Abdulaziz University Hospital between 2010 and 2019, were retrospectively reviewed. Data were analyzed using the Statistical Package for Social Sciences (SPSS; IBM Corp., Armonk, NY, USA). A p-value of 0.05 or less was considered statistically significant. Results Out of the 281 patients, 141 were (50.2%) female. The average age of the patients was 9.50 ± 4.24 years. The most common type of strabismus was esotropia (177 [63%] patients), followed by exotropia (96 [34.2%] patients), hypertropia (10 [3.6%] patients), and dissociated vertical deviation (four [1.4%] patients). Two-hundred thirty-one (82.8%) patients had bilateral strabismus. A total of 178 patients (63.3%) had no associated conditions with strabismus, whereas 103 (36.7%) had an associated condition. A significant relationship was observed between esotropia and prematurity (p = 0.024). Conclusion Esotropia was the most common type of strabismus among the patients, followed by exotropia. The results of this study showed that males were equally affected as females. We also found a significant relationship between esotropia and prematurity. Implementation of a compulsory nationwide pediatric ophthalmic screening program for children aged one, three, and five years is recommended to enable timely diagnosis of strabismus and any other refractive errors.

Binocularity outcomes following treatment for retinopathy of prematurity

OBJECTIVE

Retinopathy of prematurity (ROP) is a leading cause of childhood visual impairment. Treatment options for severe ROP include laser and/or anti-vascular endothelial growth factor (anti-VEGF) injections. Previous studies have compared the 2 treatments for functional outcomes including visual acuity, amblyopia, and strabismus. The purpose of this study was to evaluate the influence of treatment on binocularity.

METHODS

In this masked, cross-sectional study, binocularity was measured using Bagolini lenses and the Frisby stereotest in children aged 3-8 years with a history of ROP treatment in 2 Canadian centres. Events associated with disruption of binocularity including amblyopia, anisometropia, and strabismus, were recorded and analyzed as secondary outcomes.

RESULTS

A total of 42 children were recruited: 19 were treated with laser and 23 with an anti-VEGF agent. The mean age at the time of assessment in the laser group was 81.2 (6.8 years) ± 16.2 months versus 63 (5.25 years) ± 15.7 months in the anti-VEGF group (p < 0.001). No statistically significant difference in rates of binocularity was detected (68% laser vs 82% anti-VEGF, p = 0.27). Laser-treated participants experienced a greater number of cumulative insults to binocularity (p = 0.01).

CONCLUSIONS

Patients with a history of ROP treated with laser or anti-VEGF agents require long-term follow-up to address binocularity-disrupting factors. Although we did not detect a difference in rates and level of binocularity between treatment groups, we did find an increased rate of cumulative binocularity disrupting events in the laser-treated group.

Ocular Findings in Low Birthweight and Premature Babies in the First Year: Do We Need to Screen?

Purpose

There is no standardized approach for the ophthalmic care follow-up of children screened for retinopathy of prematurity (ROP). The authors report the ocular findings at 12 months in preterm and low birthweight babies screened for ROP over a 5-year period (1998–2003).

Methods

The case notes of 211 babies were retrospectively reviewed for birth details, maternal details, presence of ROP, and findings at follow-up screening which included visual acuity, refraction at 12 months, presence of squint, and any other ocular problems.

Results

At 1 year follow-up, 16.6% of ROP positive children failed a screening visit because of squint (6.66%), refractive error (6.66%), and optic nerve abnormalities (3.33%). At 1 year follow-up, 10% of ROP negative children had failed a screening visit because of squint (3.75 %), refractive error (3.75%), and other pathology (2.5%).

Conclusions

The authors recommend screening all babies with ROP at 12 months to identify amblyogenic factors such as squint and refractive error. Parents of infants who do not develop ROP should be advised of the increased risk of visual problems in their children and to have their child examined in the preschool period.

The effects of preterm birth on visual development

Children born very preterm are at a greater risk of abnormal visual and neurological development when compared to children born at full term. Preterm birth is associated with retinopathy of prematurity (a proliferative retinal vascular disease) and can also affect the development of brain structures associated with post-retinal processing of visual information. Visual deficits common in children born preterm, such as reduced visual acuity, strabismus, abnormal stereopsis and refractive error, are likely to be detected through childhood vision screening programs, ophthalmological follow-up or optometric care. However, routine screening may not detect other vision problems, such as reduced visual fields, impaired contrast sensitivity and deficits in cortical visual processing, that may occur in children born preterm. For example, visual functions associated with the dorsal visual processing stream, such as global motion perception and visuomotor integration, may be impaired by preterm birth. These impairments can continue into adolescence and adulthood and may contribute to the difficulties in learning (particularly reading and mathematics), attention, behaviour and cognition that some children born preterm experience. Improvements in understanding the mechanisms by which preterm birth affects vision will inform future screening and interventions for children born preterm.

Pedigree Analysis of Familial Primary Concomitant Horizontal Strabismus in Northern India

PURPOSE

Familial clustering of common forms of primary strabismus like esotropia (ET) and exotropia (XT) is observed in a proportion of the strabismus cohort. The genetic components of this remain unidentified. Linkage studies have demonstrated susceptibility locus for primary strabismus at the STBMS1 locus on 7p22.1 as well as other loci on 4q28.3 and 7q31.2. Recently next generation sequencing (NGS) technology has emerged as a powerful tool in discovery genomics and a large number of novel disease-causing variants are being reported. In this study, we recruited informative families for subsequent genetic analysis for disease-causing variant identification.

METHODS

All consecutive families with two or more affected members with primary concomitant horizontal strabismus were prospectively recruited at the ophthalmic outpatients department (OPD) of Lady Hardinge Medical College, New Delhi, from August 2014 to February 2017. Detailed phenotypic evaluation and pedigree documentation was performed.

RESULTS

Of the 39 recruited families of north Indian origin, 18 families each had affected family members demonstrating either ET or XT. 100% concordance of the phenotype in the affected family members was observed in these families. While vertical transmission was observed in 17/18 families with XT, 7 with ET had affected members across one generation, 2 demonstrated consanguineous pedigree, and 2 comprised identical twin families. In 3 families, a combination of ET and XT was noted. This comprised one family with the ET and XT patients being from 2 separate arms of the family related by marriage, one family where one sibling had XT and the other had ET, and another family where the maternal aunt of the affected proband with ET had XT.

CONCLUSIONS

Subjects with familial primary concomitant strabismus recruited in this study may provide a valuable resource to unravel the genetic determinants of this condition, which is a common disorder of early childhood with high ophthalmic morbidity.

Sensorimotor outcomes in children with prenatal exposure to methadone

PURPOSE

To report the presentation and characteristics of strabismus in children with prenatal methadone exposure.

METHODS

The medical records of children with prenatal methadone exposure were retrospectively reviewed. Those who were evaluated by pediatric ophthalmology were included. Information on the timing and types of prenatal exposure by trimester of pregnancy was then collected from the patients' mothers' charts. The children's perinatal histories and ophthalmologic findings were collected from their pediatric clinic charts and ophthalmology clinic charts, respectively.

RESULTS

A total of 210 children with prenatal methadone exposure were identified, of whom 32 (15.2%) underwent eye examinations and 21 (10%) had strabismus. Five patients had esodeviations, with a mean age of onset of 11.6 months; 16 had exodeviations, with a mean age of onset of 6.8 months. Three patients with strabismus were born prematurely, and 2 had intracranial disease. Two patients underwent strabismus surgery.

CONCLUSIONS

The incidence of strabismus in patients with prenatal methadone exposure was higher than in the general population (10% vs 3%-4%). Intermittent exotropia was the most common type of strabismus and presented earlier than in the general population, with no association with other systemic disease. Prenatal exposure to methadone was likely confounded by exposure to other substances, environmental factors, and genetics. Poor compliance with follow-up reduced the power of the study.

Strabismus-associated myopia. Review

INTRODUCTION

The treatment of strabismus associated with myopia is often a therapeutic challenge for the ophthalmologist. The strabismus associated with myopia has certain peculiarities and there are even certain types of strabismus that occur exclusively in myopia, such as strabismus fixus, requiring treatments with specific surgical techniques.

MATERIALS AND METHODS

It is important to make a correct differential diagnosis, because there are many conditions described with this association. A review is presented of strabismus associated with myopia, together with its treatment adjusted to refractive error.

RESULTS

Measurements of strabismus may be altered by the prismatic effect of the spectacles. Surgical results may be unpredictable if myopia is not taken into account. Better results were obtained with the techniques of anatomical replacement described by Yokoyama than with traditional retro-insertion-resection.

CONCLUSION

For the diagnosis and appropriate treatment of strabismus, it is important to make a correct measurement of the angle of deviation, and perform image tests prior to surgery in certain cases. The anatomical characteristics of the myopic eye should also be taken into account during surgery.

Strabismus at Age 2 Years in Children Born Before 28 Weeks' Gestation: Antecedents and Correlates

Children born very preterm are at greater risk of ophthalmic morbidities, including strabismus, than children born at term. We evaluated perinatal factors associated with strabismus at age 2 years in a large population of infants delivered before 28 weeks' gestation. A total of 996 infants in the multicenter ELGAN (Extremely Low Gestational Age Newborn) study who had a retinal exam in infancy and a developmental assessment at 2 years corrected age are included. Their mothers were interviewed about the pregnancy, and both mother and newborn charts were reviewed. Certified examiners administered the Bayley Scales of Infant Development-II and performed an examination of ocular alignment. Time-oriented logistic regression risk models were created to evaluate the associations of characteristics and exposures with the development of strabismus. Overall, 14% (n = 141) of the children had strabismus at 2 years, and 80% of strabismic children had esotropia. Characteristics associated with strabismus were birth before 26 weeks' gestation, severe fetal growth restriction, and maternal history of aspirin ingestion. Associated postnatal factors included a SNAP-II (Score for Neonatal Acute Physiology) illness severity value ≥ 30, brain ventriculomegaly, type I retinopathy of prematurity, and ventilator-dependent severe bronchopulmonary dysplasia. Strabismus in very preterm populations is associated with a number of antenatal and postnatal antecedents as well as clinical and imaging correlates indicative of brain damage in these children. Routine ophthalmologic assessments in the early years can allow appropriate and timely interventions.

Convergence and Accommodation Development Is Preprogrammed in Premature Infants

PURPOSE

This study investigated whether vergence and accommodation development in preterm infants is preprogrammed or is driven by experience.

METHODS

Thirty-two healthy infants, born at mean 34 weeks gestation (range, 31.2-36 weeks), were compared with 45 healthy full-term infants (mean 40.0 weeks) over a 6-month period, starting at 4 to 6 weeks postnatally. Simultaneous accommodation and convergence to a detailed target were measured using a Plusoptix PowerRefII infrared photorefractor as a target moved between 0.33 and 2 m. Stimulus/response gains and responses at 0.33 and 2 m were compared by both corrected (gestational) age and chronological (postnatal) age.

RESULTS

When compared by their corrected age, preterm and full-term infants showed few significant differences in vergence and accommodation responses after 6 to 7 weeks of age. However, when compared by chronological age, preterm infants' responses were more variable, with significantly reduced vergence gains, reduced vergence response at 0.33 m, reduced accommodation gain, and increased accommodation at 2 m compared to full-term infants between 8 and 13 weeks after birth.

CONCLUSIONS

When matched by corrected age, vergence and accommodation in preterm infants show few differences from full-term infants' responses. Maturation appears preprogrammed and is not advanced by visual experience. Longer periods of immature visual responses might leave preterm infants more at risk of development of oculomotor deficits such as strabismus.

Management of Strabismus in Myopes

Strabismus in myopes can be related to anisometropia, accommodation/convergence effects, and/or muscle path deviations. This review article highlights management considerations in myopic patients.

Effect of gestational age and birth weight on the risk of strabismus among premature infants

IMPORTANCE

Strabismus causes irreversible vision loss if not detected and treated early. It is unclear whether birth weight (BW) and gestational age (GA) are risk factors for strabismus.

OBJECTIVE

To estimate the effect of BW and GA on the likelihood of premature infants developing strabismus.

DESIGN, SETTING, AND PARTICIPANTS

In this longitudinal cohort analysis, we monitored a group of premature children from birth to determine the proportion that developed strabismus and the timing of the first strabismus diagnosis. Multivariable Cox regression analyses assessed the relationships of BW and GA with the development of strabismus. Regression models were adjusted for other risk factors for strabismus, sociodemographic factors, and ocular comorbidities. The analysis included 38,055 otherwise healthy children born prematurely who were enrolled for more than 6 months in a nationwide US managed care network between 2001 and 2011 in communities throughout the United States.

EXPOSURES

Birth weight less than 2000 g or GA of 32 weeks or less.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) for strabismus with 95% CIs.

RESULTS

Of 38,055 otherwise healthy children who were born prematurely, 583 received a diagnosis of strabismus later in life. The cumulative incidence of strabismus was 3.0% at 5 years. Controlling for GA and other covariates, infants born with BW less than 2000 g had a 61% increased hazard (HR, 1.61; 95% CI, 1.22-2.13) of developing strabismus. Controlling for BW and other covariates, there was no significant association between strabismus and GA (HR, 0.98; 95% CI, 0.69-1.38). Among premature infants with BW of less than 2000 g, a GA of 32 weeks or less conveyed no additional increased risk for developing strabismus relative to infants born after 32 weeks (HR, 1.27; 95% CI, 0.86-1.88). In contrast, among infants with a GA of 32 weeks or less, BW of less than 2000 g conveyed a 14-fold increase in the risk of strabismus relative to BW of 2000 g or more (HR, 14.39; 95% CI, 1.99-104.14).

CONCLUSIONS AND RELEVANCE

Independent of GA, very low BW conferred a large increase in strabismus risk among premature infants. In contrast, independent of BW, GA did not significantly affect the risk of strabismus. Updates to existing guidelines in the pediatric and ophthalmic literature should be considered, highlighting the importance of BW rather than GA and alerting clinicians about the need for careful monitoring of premature infants with low BW for strabismus.

Prevalence and course of strabismus through age 6 years in participants of the Early Treatment for Retinopathy of Prematurity randomized trial

PURPOSE

To present strabismus data for children who participated in the Early Treatment for Retinopathy of Prematurity (ETROP) randomized trial.

METHODS

The prevalence of strabismus, categorized as present or absent, was tabulated for all children with history of high-risk prethreshold retinopathy of prematurity (ROP) who participated in the ETROP randomized trial and were examined at 9 months to 6 years of age. Relationships among strabismus and demographic measures, eye characteristics, and neurodevelopmental factors were analyzed.

RESULTS

Among the 342 children evaluated at 6 years, the prevalence of strabismus was 42.2%. Even with favorable acuity scores in both eyes, the prevalence of strabismus was 25.4%, and with favorable structural outcomes in both eyes the prevalence of strabismus was 34.2%. Of children categorized as visually impaired as the result of either ocular or cerebral causes, 80% were strabismic at the 6-year examination. Of 103 study participants who were strabismic at 9 months, 77 (74.8%) remained so at 6 years. Most strabismus was constant at both the 9-month (62.7%) and the 6-year examination (72.3%). After multiple logistic regression analysis, risk factors for strabismus were abnormal fixation behavior in one or both eyes (P < 0.001), history of amblyopia (P < 0.003), unfavorable structural outcome in one or both eyes (P = 0.025), and history of anisometropia (P = 0.04). Strabismus surgery was performed for 53 children. By 6 years, the cumulative prevalence of strabismus was 59.4%.

CONCLUSIONS

Most children with a history of high-risk prethreshold ROP develop strabismus at some time during the first 6 years of life.

Ocular growth and morbidity in preterm children without retinopathy of prematurity

PURPOSE

To investigate ocular growth and morbidity in both preschool and school-aged children born prematurely without retinopathy of prematurity (ROP).

METHODS

This population-based study was carried out in 26 children, 5-7 years of age, born prematurely without ROP. All children underwent a full ocular examination, including corrected visual acuity, cycloplegic refractive errors, color vision, ocular alignment, and anterior and posterior segment examinations. Anterior chamber depth, lens thickness, vitreous length, and total axial length were measured.

RESULTS

There was no correlation between the degree of prematurity and visual acuity or refractive state. Two (7.7%) subjects had strabismus, two (7.7%) had amblyopia, and four (15%) had anisometropia. Total axial length was significantly correlated with both gestational age at birth (r=0.822, P<0.001) and birth weight (r=0.569, P=0.003). Similarly, vitreous length was also significantly correlated with gestational age (r=0.744, P<0.001) and birth weight (r=0.553, P=0.004).

CONCLUSIONS

This study showed that although the globe gets longer as gestational age approaches term and as birth weight increases, this condition does not result in any significant refractive error. According to the literature, the prevalence of strabismus, amblyopia, and anisometropia may be higher in preterm children without ROP than in age-matched, normally delivered children.

The neurovascular retina in retinopathy of prematurity

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP disease process. The age of onset of ROP coincides with the rapid developmental increase in rod photoreceptor outer segment length and rhodopsin content of the retina with escalation of energy demands. Using a combination of non-invasive electroretinographic (ERG), psychophysical, and image analysis procedures, the neural retina and its vasculature have been studied in prematurely born human subjects, both with and without ROP, and in rats that model the key vascular and neural parameters found in human ROP subjects. These data are compared to comprehensive numeric summaries of the neural and vascular features in normally developing human and rat retina. In rats, biochemical, anatomical, and molecular biological investigations are paired with the non-invasive assessments. ROP, even if mild, primarily and persistently alters the structure and function of photoreceptors. Post-receptor neurons and retinal vasculature, which are intimately related, are also affected by ROP; conspicuous neurovascular abnormalities disappear, but subtle structural anomalies and functional deficits may persist years after clinical ROP resolves. The data from human subjects and rat models identify photoreceptor and post-receptor targets for interventions that promise improved outcomes for children at risk for ROP.

Delayed Visual Attention Caused by High Myopic Refractive Error

Delayed visual maturation (DVM) is usually a retrospective diagnosis given to infants who are born with no or poor visually-directed behavior, despite normal acuity on objective testing, but who recover months later. This condition can be organized into several types based on associated neurodevelopmental or ocular findings, but the etiology of DVM is probably complex and involves multiple possible origins. Here we report two infants who presented with delayed visual maturation (attention). They were visually unresponsive at birth but were later found to have high myopic errors. Patient 1 had -4 D right eye, -5 D left eye. Patient 2 had -9 D o.u. Upon spectacle correction at 5 and 4 months, respectively, both infants immediately displayed visually-directed behavior, suggesting that a high refractive error was the cause of inattention in these patients. These findings could add to knowledge surrounding DVM and the diagnosis of apparently blind infants. Findings presented here also indicate the importance of prompt refractive error measurement in such cases.

Childhood visual impairment: normal and abnormal visual function in the context of developmental disability

Abnormal or failed development of vision in children may give rise to varying degrees of visual impairment and disability. Disease and organ-specific mechanisms by which visual impairments arise are presented. The presentation of these mechanisms, along with an explanation of established pathologic processes and correlative up-to-date clinical and social research in the field of pediatrics, ophthalmology, and rehabilitation medicine are discussed. The goal of this article is to enhance the practitioner's recognition and care for children with developmental disability associated with visual impairment.

Ophthalmological problems associated with preterm birth

As survival of preterm infants improves, the long-term care of consequent ophthalmic problems is an expanding field. Preterm birth can inflict a host of challenges on the developing ocular system, resulting in the visual manifestations of varied significance and pathological scope. The ophthalmic condition most commonly associated with preterm birth is retinopathy of prematurity, which has the potential to result in devastating vision loss. However, the visual compromise from increased incidence of refractive errors, strabismus, and cerebral vision impairment has significant impact on visual function, which also has influence on other developmental aspects including psychological and educational. In this review, the normal ocular development is discussed, aiming to exemplify the impact of early exteriorisation on one of the more naive organs of prematurity. This is then related to the incidence and visual consequences of many types of deficit, including refractive error, strabismus, and loss of visual function in preterm populations, with comparisons to term infant studies. Often these conditions are linked with causal and resultant factors being impossible to segregate, but the common factor of increased rates of all types of ophthalmic deficits demonstrates that children born prematurely are indeed premature for life.

Long term ophthalmic sequelae of prematurity

There are numerous reports of an increase in refractive errors and amblyogenic factors in the low birth weight population relative to children born at full term. This raises the question of whether additional long term ophthalmic screening is required. The current provision of follow up care for preterm infants in the UK is haphazard and varies in terms of its availability, the type of assessment, age at assessment and age at discharge. This issue needs to be addressed to provide the best care for these children however there are different possible methodologies. One key aspect of a screening programme is the age at testing as this dictates the possible tests used which impacts on the efficacy. However, although the prevalence of strabismus and refractive errors is well documented the development of these conditions is poorly understood so for this and other reasons it is difficult to devise the most effective screening programme.

Visual outcomes and perinatal adversity

Preterm birth per se, the neonatal environment, retinopathy of prematurity (ROP) and neurological damage are all causes of visual impairment and the impact of these factors is discussed in relation to the resultant ophthalmic deficits. Visual acuity impairments range from blindness, due to ROP or cortical visual impairment, which can be identified at an early age, to subtle deficits related to preterm birth only identified at a later age. Visual function deficits are not limited to visual acuity but can affect contrast sensitivity, field of vision and colour vision. Strabismus and refractive errors are also very common in children following perinatal adversity. Although more is now known about the types of deficits affecting these children, there is still a poor understanding of how these deficits impact on a child's functional ability. The impact of these ophthalmic deficits on the long term ophthalmic care required, and the role of perinatal factors, is discussed.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

Nutritional factors and visual function in premature infants

Approximately 5-7% of all infants are born prematurely, and birth before 37 weeks is the most common cause of neonatal mortality, morbidity and long-term disability. Premature infants are poorly equipped for life outside the womb, and oxidant stress has been implicated in the aetiology of visual impairment in these infants, who are often exposed to increased O2 concentrations and high light intensity in neonatal units. The carotenoids lutein and zeaxanthin, which give the macular area of the eye its yellow colour, are located in the retinal pigment epithelium of the eye, and are believed to play a role in protecting it against oxidative and light damage. The macular pigments are of dietary origin, and green leafy vegetables are the primary source of lutein and zeaxanthin. Lutein is one of the five most common carotenoids found in the diet. There is current interest in the macular pigment in relation to age-related macular degeneration, but these pigments may also have a protective role in the retinal pigment epithelium of the newborn infant. Little information is available on blood lutein and zeaxanthin levels in neonates. Levels of lutein in human milk are two to three times higher than those of beta-carotene, whereas their concentrations in the mothers' blood are approximately the same. Human milk is the main dietary source of lutein and zeaxanthin for infants until weaning occurs. The biochemical mechanisms which mediate the transport of the macular carotenoids into the eye are not known, but tubulin has been identified as the major carotenoid-binding protein, and may play a role in the physiology of the macula.

The long term ophthalmic morbidity of low birth weight children: a review

Low birth weight infants are at greater risk of ophthalmic morbidity compared to children born at term. There are numerous studies detailing the outcome of low birth weight infants and the purpose of this paper is to discuss and summarize these studies, focusing on the long term effects on visual function and the prevalence of strabismus. The variation in study design will be discussed with regard to the subsequent effect on results. Despite the significant variation between studies, they all report an increase in the prevalence of strabismus and reduced visual acuity. This increase in ophthalmic morbidity is due in part to retinopathy of prematurity (ROP), but not all ophthalmic morbidity can be attributed to ROP.

Comitant strabismus

A review of the literature on comitant strabismus of the period from April 1999 until April 2000 is presented. A rather new and increasingly important issue is the psychosocial aspect of strabismus. Two studies have demonstrated that strabismus creates a significant negative social prejudice on the patients and that it can significantly reduce an applicant's ability to obtain employment. Subsequently, strabismus surgery can no longer be called "cosmetic". Concerning the timing of surgery in congenital esotropia, it was reported that early surgery does not ensure continued alignment, but frequently requires additional operations. The increased risk of early-onset strabismus in prematurely born children was confirmed by several studies, and the importance of regular ophthalmologic controls of all preterm infants screened for retinopathy of prematurity was stressed. It was reported that risk factors are cicatricial retinopathy of prematurity, refractive error, family history of strabismus, and poor neurodevelopmental outcome, rather than low gestational age and regressed acute retinopathy of prematurity. A number of other aspects of interest concerning exotropia, esotropia, and dissociated vertical deviation are presented in this review.

Periventricular leukomalacia: an important cause of visual and ocular motility dysfunction in children

The immature visual system in infants born preterm is vulnerable to adverse events during the perinatal period. Periventricular leukomalacia affecting the optic radiation has now become the principal cause of visual impairment and dysfunction in children born prematurely. Visual dysfunction is characterized by delayed visual maturation, subnormal visual acuity, crowding, visual field defects, and visual perceptual-cognitive problems. Magnetic resonance imaging is the method of choice for diagnosing this brain lesion, which is associated with optic disk abnormalities, strabismus, nystagmus, and deficient visually guided eye movements. Children with periventricular leukomalacia may present to the ophthalmologist within a clinical spectrum from severe cerebral visual impairment in combination with cerebral palsy and mental retardation to only early-onset esotropia, normal intellectual level, and no cerebral palsy. Optimal educational and habilitational strategies need to be developed to meet the needs of this group of visually impaired children.