Diverse Research Teams and Underrepresented Groups in Clinical Studies

Importance

Several ophthalmic diseases disproportionately affect racial and ethnic minority patients, yet most clinical trials struggle to enroll cohorts that are demographically representative of disease burden; some barriers to recruitment include time and transportation, language and cultural differences, and fear and mistrust of research due to historical abuses. Incorporating diversity within the research team has been proposed as a method to increase trust and improve engagement among potential study participants.

Objective

To examine how demographic factors of potential research participants and personnel may be associated with patient consent rates to participate in prospective ophthalmic clinical studies.

Design, Setting, and Participants

This retrospective cohort study included patients from an urban, academic hospital who were approached for consent to participate in prospective ophthalmic clinical studies conducted between January 2015 and December 2021.

Main Outcomes and Measures

Multivariable logistic regression assessing associations between patient and research personnel demographics and rates of affirmative consent to participate was used.

Results

In total, 1380 patients (mean [SD] age, 58.6 [14.9] years; 50.3% male) who were approached for consent to participate in 10 prospective ophthalmic clinical studies were included. Of prospective patients, 566 (43.5%) were Black; 327 (25.1%), Hispanic or Latino; 373 (28.6%), White; 36 (2.8%), other race and ethnicity; and 78 (5.8%) declined to answer. Black patients (odds ratio [OR], 0.32; 95% CI, 0.24-0.44; P < .001) and Hispanic or Latino patients (OR, 0.31; 95% CI, 0.20-0.47; P < .001) were less likely to consent compared with White patients. Patients with lower socioeconomic status were less likely to consent than patients with higher socioeconomic status (OR, 0.43; 95% CI, 0.33-0.53; P < .001). Concordance between patient and research staff race and ethnicity was associated with increased odds of affirmative consent (OR, 2.72; 95% CI, 1.99-3.73; P < .001).

Conclusions and Relevance

In this cohort study, patients from underrepresented racial and ethnic groups and those with lower socioeconomic status were less likely to participate in ophthalmic clinical studies. Concordance of race and ethnicity between patients and research staff was associated with improved participant enrollment. These findings underscore the importance of increasing diversity in clinical research teams to improve racial and ethnic representation in clinical studies.

Modifiable Risk Factors and Preventative Strategies for Severe Retinopathy of Prematurity

Severe ROP is characterized by the development of retinal fibrovascular proliferation that may progress to retinal detachment. The purpose of this report is to review five of the most common and well-studied perinatal and neonatal modifiable risk factors for the development of severe ROP. Hyperoxemia, hypoxia, and associated prolonged respiratory support are linked to the development of severe ROP. While there is a well-established association between clinical maternal chorioamnionitis and severe ROP, there is greater variability between histologic chorioamnionitis and severe ROP. Neonatal sepsis, including both bacterial and fungal subtypes, are independent predictors of severe ROP in preterm infants. Although there is limited evidence related to platelet transfusions, the risk of severe ROP increases with the number and volume of red blood cell transfusions. Poor postnatal weight gain within the first six weeks of life is also strongly tied to the development of severe ROP. We also discuss preventative strategies that may reduce the risk of severe ROP. Limited evidence-based studies exist regarding the protective effects of caffeine, human milk, and vitamins A and E.

The Scholarly Impact of Student Authorship in Ophthalmology

Purpose  The H-index (H i ), an author-level metric of scholarly impact, is predictive of future scientific achievement. We sought to analyze the scholarly impact of student authorship on the H i of corresponding authors (CAs) within a major academic journal in the specialty of ophthalmology. Materials and Methods  We compared the H i of all unique CAs for manuscripts published in Ophthalmology (Journal of the American Academy of Ophthalmology) in 2008, 2012, and 2016. Data abstraction was completed twice: in October 2018 and March 2021. We further grouped published articles for CAs into those with student authors (StA) and those without (nStA). Primary analysis involved a linear regression analysis with change in H i from October 2018 to March 2021 as the outcome variable, CA groups as the predictor variable, adjusting for the covariates of baseline H i , the year when the CA published his or her article, number of research items published in October 2018, and the academic appointment of the CAs. Secondary analysis involved a linear regression analysis with change in H i from October 2018 to March 2021 as the outcome variable, total number of student authors per CA as the predictor variable, adjusting for the covariates of baseline H i , the year CA published his or her article, number of research items published in October 2018, and the academic appointment of the CAs. Results  The number of student authors increased from 168 in 2008 to 192 in 2016. Of the 902 articles, 316 articles were co-authored by one or more student authors. The average change in H i of CAs publishing with student authors (StA, 11.0 ± 14.7) was significantly greater ( p  < 0.0001) than the change in H i of CAs publishing without student authors (nStA, 6.2 ± 6.2). As the total number of student authors increased, the change in H i of CAs increased linearly for all years combined (regression coefficient = 1.70, p -value < 0.0001). Conclusion  CAs publishing with students in the field of ophthalmology have a higher scholarly impact than those publishing without students. The development of programs to integrate students into ophthalmology research early on may encourage their pursuit of a career in ophthalmology, while advancing the careers of their mentors.

Long-term strabismus outcomes after unilateral infantile cataract surgery in the Infant Aphakia Treatment Study

PURPOSE

To characterize long-term strabismus outcomes in children in the Infant Aphakia Treatment Study (IATS).

METHODS

This study was a secondary data analysis of long-term ocular alignment characteristics of children aged 10.5 years who had previously been enrolled in a randomized clinical trial evaluating aphakic management after unilateral cataract surgery between 1 and 6 months of age.

RESULTS

In the IATS study, 96 of 109 children (88%) developed strabismus through age 10.5 years. Half of the 20 children who were orthophoric at distance through age 5 years maintained orthophoria at distance fixation at 10.5 years. Esotropia was the most common type of strabismus prior to age 5 years (56/109 [51%]), whereas exotropia (49/109 [45%]) was the most common type of strabismus at 10.5 years (esotropia, 21%; isolated hypertropia, 17%). Strabismus surgery had been performed on 52 children (48%), with 18 of these (35%) achieving microtropia <10^Δ. Strabismus was equally prevalent in children randomized to contact lens care compared with those randomized to primary intraocular lens implantation (45/54 [83%] vs 45/55 [82%]; P = 0.8). Median visual acuity in the study eye was 0.56 logMAR (20/72) for children with orthotropia or microtropia <10^Δ versus 1.30 logMAR (20/400) for strabismus ≥10^Δ (P = 0.0003).

CONCLUSIONS

Strabismus-in particular, exotropia-is common irrespective of aphakia management 10 years following infant monocular cataract surgery. The delayed emergence of exotropia with longer follow-up indicates a need for caution in managing early esotropia in these children. Children with better visual acuity at 10 years of age are more likely to have better ocular alignment.

Unilateral Familial Exudative Vitreoretinopathy: Clinical Profile and Pathology

We report a case of a newborn with unilateral retinal detachment that could not be repaired. At examination under anesthesia, the retina was markedly abnormal and a presumptive diagnosis of retinal dysplasia was made. Several years later, the eye was enucleated because it was blind and painful. Final pathology was consistent with familial exudative vitreoretinopathy (FEVR). The literature describing unilateral retinal dysplasia is sparse. This case adds to the clinical spectrum of pathologic findings in FEVR.

Rate of ocular trauma in children operated on for unilateral cataract in infancy-data from the Infant Aphakia Treatment Study

To determine whether the fellow eye of children who have undergone unilateral cataract extraction in the first year of life are at increased risk of injury and vision loss, the 10.5-year data on 109 of 114 children enrolled in the Infant Aphakia Treatment Study were examined. Based on this limited data, it was estimated that the fellow eye is at greater risk of injury than the operated eye. Our data do not support the risk being higher in children with the worst vision in the treated eye.

Development of refractive error in children treated for retinopathy of prematurity with anti-vascular endothelial growth factor (anti-VEGF) agents: A meta-analysis and systematic review

Objective

To investigate refractive error development in preterm children with severe retinopathy of prematurity (ROP) treated with anti-vascular endothelial growth factor (anti-VEGF) agents and laser photocoagulation.

Methods

Selection criteria were comparative studies that compared the refractive errors in children, birthweights ≤1500 grams and gestational ages ≤30 weeks, and treatments for Type I ROP with intravitreal bevacizumab (IVB) versus laser photocoagulation. Studies were identified using PubMed, Google Scholar, and published reviews. Meta-analyses were performed on the post-treatment outcomes of spherical equivalent (SEQ), cylindrical power, and prevalence of high myopia. Longitudinal development of refractive error in IVB, or in laser-treated children, or in normal full-term children was visually summarized.

Results

Two randomized controlled trials and 5 non-randomized studies, including a total of 272 eyes treated by IVB and 247 eyes treated by laser, were included in this study. Compared with laser-treated children, IVB-treated children have less myopic refractive error (P<0.001), lower prevalence of high myopia (P<0.05), and less astigmatism (P = 0.02).

Conclusions

Treatment with IVB is associated with less myopia and astigmatism than laser treatment for infants with severe ROP. Given the complexity of ROP and the variability of dosing, our review supports close monitoring of refractive error outcomes in children treated with IVB.

Don't Miss This! Red Flags in the Pediatric Eye Exam: Pupils

The pupillary exam in the pediatric population is a vital part of any clinician's workup. In the right clinical setting, pupillary abnormalities such as anisocoria, light-near dissociation, an afferent pupillary defect, and paradoxic pupillary constriction in the dark can be red flags that trigger further examination and workup. Through both careful physical examination and detailed history-taking and observation, potentially vision- and life-threatening conditions can be detected.

Don't Miss This! Red Flags in the Pediatric Eye Examination: Introduction and Essential Concepts

Although the pediatric eye examination can be made more challenging by inattention, poor cooperation, sleep, or just the wiggles, these should never be justification for an inadequate assessment of the child. In fact, a challenging patient should make the examiner ever more careful to get a good history and to look carefully for potential red flags that should be examined in greater detail. Missing a history of diplopia, or not noticing an abnormal pupil, or blurred disc margins, to name a few, may delay the diagnosis and treatment of potentially life-threatening entities. In this symposium, red flags in the pediatric eye examination will be reviewed in depth with emphasis on diagnosis, testing, and referral.

Improvement of Eye Alignment in Adult Strabismic Monkeys by Sustained IGF-1 Treatment

Purpose

The goal of this study was to determine if continuous application of insulin-like growth factor-1 (IGF-1) could improve eye alignment of adult strabismic nonhuman primates and to assess possible mechanisms of effect.

Methods

A continuous release pellet of IGF-1 was placed on one medial rectus muscle in two adult nonhuman primates (M1, M2) rendered exotropic by the alternating monocular occlusion method during the first months of life. Eye alignment and eye movements were recorded for 3 months, after which M1 was euthanized, and the lateral and medial rectus muscles were removed for morphometric analysis of fiber size, nerve, and neuromuscular density.

Results

Monkey 1 showed a 40% reduction in strabismus angle, a reduction of exotropia of approximately 11° to 14° after 3 months. Monkey 2 showed a 15% improvement, with a reduction of its exotropia by approximately 3°. The treated medial rectus muscle of M1 showed increased mean myofiber cross-sectional areas. Increases in myofiber size also were seen in the contralateral medial rectus and lateral rectus muscles. Similarly, nerve density increased in the contralateral medial rectus and yoked lateral rectus.

Conclusions

This study demonstrates that in adult nonhuman primates with a sensory-induced exotropia in infancy, continuous IGF-1 treatment improves eye alignment, resulting in muscle fiber enlargement and altered innervational density that includes the untreated muscles. This supports the view that there is sufficient plasticity in the adult ocular motor system to allow continuous IGF-1 treatment over months to produce improvement in eye alignment in early-onset strabismus.

Strabismus surgery outcomes in the Infant Aphakia Treatment Study (IATS) at age 5 years

PURPOSE

To report strabismus surgery frequency and outcomes after monocular infantile cataract surgery with or without IOL implantation.

METHODS

The Infant Aphakia Treatment Study (IATS) is a randomized, multicenter clinical trial comparing treatment of aphakia with a primary IOL or contact lens in 114 infants with a unilateral congenital cataract. This report is a secondary outcome analysis of ocular motor data from IATS patients who underwent strabismus surgery prior to age 5 years.

RESULTS

Strabismus surgery was performed in 45 (39%) patients (contact lens group [CL], 37%; IOL group, 42% [P = 0.70]). The indications for strabismus surgery were esotropia (62%), exotropia (33%), and hypertropia (4%). Infants who underwent cataract surgery at a younger age were less likely to undergo strabismus surgery (28-48 days, 12/50 [24%]; 49-210 days, 33/64 [52%]; P = 0.0037). Of the 42 patients who underwent strabismus surgery, 14 (33%) had a postoperative distance alignment within 8^Δ of orthotropia at age 5 years. The 5-year visual acuity of children with strabismus was the same whether or not strabismus surgery had been performed (1.10 logMAR with surgery vs 1.00 without [P = 0.71]).

CONCLUSIONS

In this study cohort, cataract surgery performed in the first 6 weeks of life was associated with a reduced frequency of strabismus surgery. Strabismus surgery outcomes in this population are guarded. Surgical improvement of strabismus does not appear to influence long-term visual acuity.

Sensorimotor outcomes by age 5 years after monocular cataract surgery in the Infant Aphakia Treatment Study (IATS)

PURPOSE

To evaluate sensorimotor outcomes among children in the Infant Aphakia Treatment Study (IATS).

METHODS

Secondary outcome analysis was performed in this randomized, multicenter, clinical trial comparing treatment of unilateral aphakia with a primary intraocular lens (IOL) or contact lens (CL) correction. The alignment characteristics and sensory status of children through age 5 years were evaluated.

RESULTS

In the IATS study, 91 of 112 children (81%) developed strabismus through age 5 years. Of 34 infants who were orthotropic at near 12 months after cataract surgery, at age 5 years 14 (41%) were orthotropic at distance, and 15 (44%) were orthotropic at near at age 5 years without strabismus surgery. Eight of 56 children (14%) in the CL group and 13 of 56 (23%) in the IOL group were orthotropic at distance (P = 0.33) at 5 years of age and had no history of strabismus surgery. Thirteen of 48 (27%) who underwent cataract surgery prior to 49 days of age compared to 8 of 64 (13%) who had surgery after 49 days were orthotropic (P = 0.085). Median visual acuity in the operative eye was 0.4 logMAR (20/50) for children with orthotropia or microtropia (<10(Δ)) versus 1.10 logMAR (20/252) for strabismus ≥10(Δ) (P = 0.0001). Stereopsis was detected in 12 of 21 children (57%) with orthotropia versus 16 of 89 (18%) children with strabismus (P = 0.0006).

CONCLUSIONS

IOL placement does not reduce the development of strabismus after monocular congenital cataract surgery. Improved ocular alignment by age 5 years correlated strongly with improved visual acuity and stereopsis.

Tonic pupil after botulinum toxin-A injection for treatment of esotropia in children

A total of 27 children with esotropia (mean age, 3.9 years; range, 9 months to 13.8 years) were enrolled in a 9-month observational study following botulinum toxin A (BTX-A) injection of one (n = 7) or both (n = 20) medial rectus muscles. BTX-A dosage ranged from 3.0 to 6.0 units per muscle. Three participants developed tonic pupil, noted at the first follow-up visit, occurring 12-19 days after injection. All 3 cases occurred in the left eye of participants who underwent bilateral BTX-A injection by the same surgeon. Anisocoria diminished from a maximum of 4 mm at the 2-week visit to 1-2 mm in all patients over the 9-month postinjection data collection period. No adverse visual outcomes were noted. Tonic pupil is an infrequently reported complication of BTX-A injection for strabismus. The experience of our investigator group suggests the need for careful injection technique and thorough preinjection counseling.

Complications in the first 5 years following cataract surgery in infants with and without intraocular lens implantation in the Infant Aphakia Treatment Study

PURPOSE

To compare rates and severity of complications between infants undergoing cataract surgery with and without intraocular lens (IOL) implantation.

DESIGN

Prospective randomized clinical trial.

METHODS

A total of 114 infants were enrolled in the Infant Aphakia Treatment Study, a randomized, multi-center (12) clinical trial comparing the treatment of unilateral aphakia in patients under 7 months of age with a primary IOL implant or contact lens. The rate, character, and severity of intraoperative complications, adverse events, and additional intraocular surgeries during the first 5 postoperative years in the 2 groups were examined.

RESULTS

There were more patients with intraoperative complications (28% vs 11%, P = .031), adverse events (81% vs 56%, P = .008), and more additional intraocular surgeries (72% vs 16%, P < .0001) in the IOL group than in the contact lens group. However, the number of patients with adverse events in the contact lens group increased (15 to 24) in postoperative years 2-5 compared to the first postoperative year, while it decreased (44 to 14) in years 2-5 compared to the first postoperative year in the IOL group. If only one half of the patients in the contact lens (aphakic) group eventually undergo secondary IOL implantation, the number of additional intraocular surgeries in the 2 groups will be approximately equal.

CONCLUSION

The increased rate of complications, adverse events, and additional intraocular surgeries associated with IOL implantation in infants <7 months of age militates toward leaving babies aphakic if it is considered likely that the family will be successful with contact lens correction.

Diplopia after glaucoma surgery

The occurrence of strabismus and symptomatic diplopia following glaucoma surgery is becoming more common as the use of implanted setons increases. Understanding the factors contributing to the diplopia is critical to the development of treatment strategies to alleviate the patient's symptoms.

One-year strabismus outcomes in the Infant Aphakia Treatment Study

OBJECTIVE

To evaluate the characteristics of strabismus in infants who underwent cataract surgery with and without intraocular lens (IOL) implantation.

DESIGN

Secondary outcome analysis in a prospective, randomized clinical trial.

PARTICIPANTS

The Infant Aphakia Treatment Study is a randomized, multicenter (n = 12), clinical trial comparing treatment of aphakia with a primary IOL or contact lens in 114 infants with a unilateral congenital cataract.

INTERVENTION

Infants underwent cataract surgery with or without placement of an IOL.

MAIN OUTCOME MEASURES

The proportion of patients in whom strabismus developed during the first 12 months of follow-up was calculated using the life-table method and was compared across treatment groups and age strata using a log-rank test.

RESULTS

Strabismus developed within the first 12 months of follow-up in 38 pseudophakic infants (life-table estimate, 66.7%) and 42 infants (life-table estimate, 74.5%) treated with contact lenses (P = 0.59). The younger cohort (<49 days) at the time of surgery demonstrated less strabismus (29 of 50; life-table estimate, 58.0%) than the older cohort (≥ 49 days; 51 of 64; life-table estimate, 80.0%; P<0.01).

CONCLUSIONS

Intraocular lens placement does not prevent the early development of strabismus after congenital cataract surgery. However, strabismus was less likely to develop in infants whose cataract was removed at an earlier age.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Incidence of cataract development by 6 months' corrected age in the Early Treatment for Retinopathy of Prematurity study

PURPOSE

To report the incidence of cataract development by 6 months' corrected age in preterm children who participated in the Early Treatment for Retinopathy of Prematurity study.

METHODS

Infants who developed prethreshold retinopathy of prematurity (ROP) in one or both eyes and were determined by the RM-ROP2 model to have a high risk of poor structural outcome without treatment were randomized to receive early treatment (ET), defined as laser photocoagulation at high-risk prethreshold ROP, or to be conventionally managed (CM), receiving treatment only if threshold ROP developed. Data on eyes developing a cataract by 6 months' corrected age were analyzed.

RESULTS

Of 401 randomized infants, 366 survived patients were followed, and 8 eyes of 7 patients (1.9%) developed cataracts by 6 months' corrected age. Among these patients, mean birth weight was 754 g, and mean gestational age was 25.7 weeks. Mean gestational age at treatment was 36.3 weeks for ET patients and 39.5 weeks for CM patients. Three ET eyes and 5 CM eyes developed a cataract. Of the CM eyes, 3 with and 2 without laser treatment developed a cataract. All 6 treated eyes had plus disease when treated. Three eyes had ROP in zone 1, whereas the other 3 had ROP in zone 2. All eyes were treated using a diode laser.

CONCLUSIONS

By 6 months' corrected age, a small number of both ET and CM eyes developed cataracts following diode laser treatment for retinopathy of prematurity. Absence of obvious intraoperative complications does not preclude subsequent cataract development, which can occur without laser treatment.

Effects of sequential injections of hepatocyte growth factor and insulin-like growth factor-I on adult rabbit extraocular muscle

PURPOSE

To determine whether hepatocyte growth factor (HGF) and insulin-like growth factor-I (IGF-I) have synergistic effects in promoting extraocular muscle fiber growth and force generation.

METHODS

A superior rectus muscle of adult rabbits was treated with either a single injection of HGF or sequential injections of HGF followed 1 week later by IGF-I. One week after HGF alone and 1 week after the IGF-I injection, the superior rectus muscles from treated and control orbits were examined for alterations in force generation as well as changes in myofiber size.

RESULTS

Injection of HGF alone did not result in changes to muscle force, specific tension, or myofiber cross-sectional area; however, it did result in a significant increase in numbers of satellite cells. Sequential injection of HGF and IGF-I resulted in significantly increased force, specific tension, and myofiber cross-sectional areas as well as increased numbers of satellite cells.

CONCLUSIONS

Preinjection with HGF augments the treatment effect of IGF-I. This synergistic effect is likely a result of HGF-induced activation of satellite cells and should allow a reduction in IGF-I dosing required to produce a given increase in extraocular muscle force generation.

Effects of the sustained release of IGF-1 on extraocular muscle of the infant non-human primate: adaptations at the effector organ level

PURPOSE

The authors have demonstrated that prolonged exposure of adult rabbit extraocular muscle (EOM) to insulin-like growth factor-1 (IGF-1) results in significantly increased cross-sectional area and muscle force generation lasting over 3 months. Here the authors assess the effects on EOM of sustained IGF-1 treatment on normal binocular infant Macaca mulatta.

METHODS

Sustained-release IGF-1 pellets were implanted bilaterally in each medial rectus (MR) muscle of two normal infant non-human primates. Eye position was examined using corneal light reflex testing. After 3 months, morphometric analyses of myofiber cross-sectional area and innervation density in treated MR muscles were compared with an age-matched control and with antagonist lateral rectus (LR) muscles.

RESULTS

After 3 months, the slow-release pellets remained at the implantation site in all four MR muscles treated. The treated MR showed pronounced increases in cross-sectional area and nerve density, mirrored in the untreated antagonist LR.

CONCLUSIONS

Three months of bilateral sustained IGF-1 release in infant non-human primate MR resulted in increased muscle size and innervation density, mirrored in the untreated antagonist LR. It appears that bilateral MR treatment resulted in slow adaptation of both treated MR and contralateral LR muscles over time such that functional homeostasis and near-normal alignment were maintained. Further work is needed to determine what signaling mechanisms maintain proportional innervation when EOMs are forced to adapt to an externally applied perturbation.

Expansion of the CHN1 strabismus phenotype

PURPOSE

Hyperactivating CHN1 mutations have been described in individuals with Duane retraction syndrome with or without vertical gaze abnormalities. This was a study of five family members with distinctive ocular dysmotility patterns that co-segregated with a novel hyperactivating CHN1 mutation.

METHODS

Participating members of a family segregating pleomorphic incomitant strabismus underwent ophthalmic examinations, and several underwent high-resolution magnetic resonance imaging (MRI) of the orbits and brain stem. Participant DNA was extracted and amplified for haplotype analysis encompassing the CHN1 region on chromosome 2q31.1, and mutation analysis of the CHN1 gene, which encodes the Rac-GAP signaling protein α2-chimaerin. In vitro functional studies of the co-inherited mutation were performed, including a Rac-GTP activation assay, quantification of α2-chimaerin translocation, and co-immunoprecipitation.

RESULTS

All five clinically affected family members exhibited monocular or binocular supraduction deficits, three in the absence of Duane retraction syndrome. MRI in four affected individuals demonstrated small or absent abducens nerves in all four, small oculomotor nerve in one, and small optic nerves in three. Superior oblique muscle volume was also decreased in three of the individuals, supporting trochlear nerve hypoplasia. Strabismus segregated with the CHN1 locus and affected individuals harbored a c.443A>T CHN1 mutation (p.Y148F). In vitro, this novel mutation behaved similarly to previously reported CHN1 mutations underlying familial Duane syndrome, hyperactivating α2-chimaerin by enhancing its dimerization and membrane association and lowering total intracellular Rac-GTP.

CONCLUSIONS

Analysis of the current pedigree expands the phenotypic spectrum of hyperactivating CHN1 mutations to include vertical strabismus and supraduction deficits in the absence of Duane retraction syndrome.

Sustained release of bone morphogenetic protein-4 in adult rabbit extraocular muscle results in decreased force and muscle size: potential for strabismus treatment

Purpose. To assess the effect of a sustained-release preparation of bone morphogenetic protein-4 (BMP-4) on EOM force generation and muscle size. Methods. Sustained-release pellets, releasing 500 nanograms/day of BMP-4 for a maximum of 3 months, were implanted beneath the superior rectus muscle (SR) belly in anesthetized adult rabbits. The contralateral side received a placebo pellet as a control. After 1, 3, and 6 months, SRs were removed, and force generation at twitch and tetanic frequencies as well as fatigue resistance were determined in vitro. Myofiber size, myosin heavy chain isoform expression, and satellite cell density were assessed histologically. Results. SR force generation was significantly decreased by BMP-4 compared with the contralateral controls. Force generation was decreased by 25-30% by 1 month, 31-50% by 3 months, and at 6 months, after 3 BMP-4-free months, force was still decreased by 20-31%. No change in fatigue was seen. Significant decreases in muscle size were seen, greatest at 3 months. At all time points Pax7- and MyoD-positive satellite cell densities were significantly decreased. Conclusions. The decreased force generation and muscle size caused by sustained release of BMP-4 suggests that myogenic signaling factors may provide a more biological method of decreasing muscle strength in vivo than exogenously administered toxins. Treating antagonist-agonist pairs of EOM with titratable, naturally occurring myogenic signaling and growth factors may provide safe, efficacious, nonsurgical treatment options for patients with strabismus.

Horizontal misalignment in patients with unilateral superior oblique palsy

PURPOSE

To determine the frequency and distribution of horizontal misalignment in patients with unilateral superior oblique palsy (SOP) and to determine the indications for combining horizontal with vertical strabismus surgery.

METHODS

Patients included in the study had a vertical heterophoria or tropia that fit Parks three-step test for SOP and had no previous strabismus surgery or other ocular motility disturbance. Ocular motility and alignment were recorded. Outcomes between patients who had vertical surgery alone and those who had combined vertical and horizontal surgery were compared using the Student's t test.

RESULTS

Of 205 patients, 121 (59.0%) had a horizontal misalignment in addition to vertical strabismus. Ninety-six patients (46.8%) required strabismus surgery. Of these, 29 had 8 prism diopters (PD) or more horizontal deviation. Twenty-two had vertical combined with horizontal surgery (V+H group). Although their initial deviation was greater, these patients had better surgical outcomes than patients who had vertical surgery alone (V group). The V+H group had a final mean horizontal deviation of 2.18 PD compared with 6.85 PD in the V group (P < .01). Postoperative vertical alignment in the V+H group was also superior with a final mean vertical deviation of 3.7 versus 6.8 PD for the V group (P = .12).

CONCLUSION

These results indicate that horizontal misalignment is common in patients with SOP. Patients with 8 PD or more horizontal deviation benefited from surgical correction of the horizontal deviation in addition to the vertical surgery.

Bilateral optic nerve drusen and gliomas in Klippel-Trenaunay syndrome

Klippel-Trenaunay syndrome (KTS) consists of a vascular nevus involving an extremity, varicosities of that extremity, and hypertrophy of bone and soft tissue. When arteriovenous malformation is also present, it is called Klippel-Trenaunay-Weber syndrome (KTWS). Ophthalmic features of these syndromes include vascular anomalies of the orbit, iris, retina, choroid, and optic nerve. We report a case of a 16-year-old girl with KTS who was found to have bilateral optic nerve and chiasmal gliomas, optic disk drusen, and acquired myelination of the retinal nerve fiber layer. These findings have not been previously reported to be associated with KTS or KTWS.

Classifying stability of misalignment in children with esotropia using simulations

OBJECTIVE

To determine the sensitivity and specificity of several classification rules for stability and instability of angle in childhood esotropia.

METHODS

We conducted 10 000 Monte Carlo simulations of participants with no actual change in angle of esotropia during follow-up, where "observed" changes in ocular alignment were sampled from a distribution of measurement errors for the prism and alternate cover test. Additional simulations were conducted for a range of "true" changes (1.0, 2.5, 4.2, 5.0, 7.5, and 10.0 prism diopters [PD] per visit) with up to 10 follow-up visits. We then estimated sensitivities and specificities for specific rules for retrospectively classifying stability (all measurements within 0, 5, 10, or 15 PD) and instability (≥2 measurements differing by ≥10 PD, etc) across a fixed number of visits. Results were extended to classifying ocular alignment stability and instability prospectively based on a varying number of measurements.

RESULTS

For a series of 4 measurements, the rules that optimized sensitivity and specificity were "all measurements within 5 PD" for stability and "at least 2 measurements differing by 15 PD or more" for instability. For a series of 3 measurements, all 3 measurements needed to be identical to confirm stability.

CONCLUSIONS

We derived definitions of stability and instability in childhood esotropia using estimates of actual measurement error that may be useful for clinical practice and for future clinical studies of esotropia.

Effects of recession versus tenotomy surgery without recession in adult rabbit extraocular muscle

PURPOSE

Surgical recession of an extraocular muscle (EOM) posterior to its original insertion is a common form of strabismus surgery, weakening the rotational force exerted by the muscle on the globe and improving eye alignment. The purpose of this study was to assess myosin heavy chain (MyHC) isoform expression and satellite cell activity as defined by Pax7 expression in recessed EOMs of adult rabbits compared with that in muscles tenotomized but not recessed and with that in normal control muscles.

METHODS

The scleral insertion of the superior rectus muscle was detached and sutured either 7 mm posterior to its original insertion site (recession surgery) or at the same site (tenotomy). One day before euthanization, the rabbits received bromodeoxyuridine (BrdU) injections. After 7 and 14 days, selected EOMs from both orbits were examined for changes in fast, slow, neonatal, and developmental MyHC isoform expression, Pax7 expression, and BrdU incorporation.

RESULTS

Recession and tenotomy surgery resulted in similar changes in the surgical EOMs. These included a decreased proportion of fast MyHC myofibers, an increased proportion of slow MyHC myofibers, and increased BrdU-positive satellite cells. Similar changes were seen in the non-operated contralateral superior rectus muscles. The ipsilateral inferior rectus showed reciprocal changes to the surgical superior rectus muscles.

CONCLUSIONS

The EOMs are extremely adaptive to changes induced by recession and tenotomy surgery, responding with modulations in fiber remodeling and myosin expression. These adaptive responses could be manipulated to improve surgical success rates.

Outcome of angle surgery in children with aphakic glaucoma

PURPOSE

To investigate the outcome of trabeculotomy and/or goniotomy for pediatric aphakic glaucoma.

METHODS

Retrospective chart review of consecutive children who had congenital cataract surgery between 1990 and 2006 and required goniotomy and/or trabeculotomy for aphakic glaucoma. Treatment success was defined as postoperative intraocular pressure of <or=24 mm Hg despite topical medication use, avoidance of trabeculectomy or shunt placement, and no visually significant complications in the follow-up period. Exclusion criteria included a diagnosis of anterior segment dysgenesis, microcornea, and glaucoma at the time of cataract surgery, and follow-up less than 1 year.

RESULTS

A total of 14 eyes of 11 patients met inclusion criteria, with a mean follow-up of 4.7 years. Of theses, 2 eyes had goniotomy alone, 3 eyes had goniotomy followed by trabeculotomy, and 9 eyes had trabeculotomy alone. Mean IOP before angle surgery was 35 +/- 10 mm Hg. Mean IOP at the last recorded visit was 22 +/- 4 mm Hg (p = 0.0005). Treatment success was observed in 8 of the 14 eyes (57.1%), with a mean number of angle procedures of 1.4 per eye: 6 eyes (42.8%) were successful after a single angle surgery, each involving an initial trabeculotomy; 3 eyes (21.4%) underwent subsequent shunt placement after initial goniotomy at 6 months, 1.3 years, and 5.5 years after the last angle surgery.

CONCLUSIONS

When intraocular surgery is indicated to control IOP in pediatric aphakic glaucoma, trabeculotomy and/or goniotomy can be successful in the majority of eyes and may decrease the need for filtering and shunting procedures.

Progression of type 2 to type 1 retinopathy of prematurity in the Early Treatment for Retinopathy of Prematurity Study

OBJECTIVE

To examine the frequency and timing of progression from type 2 to type 1 retinopathy of prematurity (ROP) in the Early Treatment for Retinopathy of Prematurity Study.

METHODS

Infants with prethreshold ROP that was no worse than low risk in 1 or both eyes, based on the RM-ROP2 model, were examined every 2 to 4 days for at least 2 weeks. Using the Early Treatment for Retinopathy of Prematurity Study-defined classification of eyes as having type 1 or type 2 prethreshold ROP, we analyzed the time to conversion from type 2 to type 1. Data were analyzed for 1 randomly selected eye for each child.

RESULTS

Of 294 eyes at first diagnosis of type 2 ROP, 65 (22.1%) progressed to type 1 (mean [SD] interval, 9.0 [6.6] days; median, 7.0 days). Of 217 eyes with type 2 ROP that had an examination in less than 7 days, 25 (11.5%) were diagnosed with type 1 ROP in less than 7 days. Of 200 eyes that continued to have type 2 disease at the first follow-up examination and underwent a subsequent examination, 24 (15.7% of the 153 eyes that had an examination in <7 days) developed type 1 ROP in less than 7 days. The risk of progression from type 2 to type 1 in less than 7 days was greatest between 33 and 36 weeks' postmenstrual age, regardless of zone of retinopathy.

CONCLUSIONS

Type 1 ROP can be identified with weekly examinations in most eyes with initial diagnosis of type 2 ROP; a small subset progresses to type 1 in less than 7 days.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00027222.

The relationship between preoperative alignment stability and postoperative motor outcomes in children with esotropia

PURPOSE

To examine the effect of preoperative alignment stability on postoperative motor outcomes in children who underwent surgery for esotropia.

METHODS

One hundred sixty-seven subjects (68 with infantile esotropia and 99 with acquired esotropia) aged less than 6 years had surgery after completing 18 weeks of follow-up as part of an observational study. Preoperative alignment was classified as stable, uncertain, or unstable, based on measurements taken at baseline and every 6 weeks for 18 weeks. Distance alignment measured by prism and alternate cover test was compared among stability classification groups at 6 weeks and 6 months after surgery.

RESULTS

Among subjects with infantile esotropia, median 6-week postoperative deviation was 2(Delta), 6(Delta), and 2(Delta) for subjects with stable, uncertain, and unstable preoperative alignment, respectively (p = 0.73 for stable vs unstable). Median 6-month postoperative deviation was 1(Delta), 9(Delta), and 1(Delta) for stable, uncertain, and unstable, respectively (p = 1.00 for stable vs unstable). Among subjects with acquired esotropia, median 6-week postoperative deviation was 6(Delta), 4(Delta), and 4(Delta) for subjects with stable, uncertain, and unstable preoperative alignment, respectively (p = 0.69 for stable vs unstable). Median 6-month postoperative deviation was 8(Delta), 4(Delta), and 6(Delta) for stable, uncertain, and unstable, respectively (p = 0.22 for stable vs unstable).

CONCLUSIONS

Postoperative alignment at 6 weeks and 6 months appears similar in children with stable versus unstable preoperative esotropia. Nevertheless, our finding should be interpreted with caution due to small sample size.

Anterior ciliary circulation from the horizontal rectus muscles

PURPOSE

To quantify the anterior ciliary arteries that accompany horizontal rectus muscles and to correlate these findings with analysis of arterial cross-sectional area in distal tendons of these muscles.

PATIENTS AND METHODS

In 31 consecutive patients, previously unoperated horizontal rectus muscles were photographed intraoperatively. Major and minor anterior ciliary arteries (ACAs) were counted from the photographs by a masked independent observer and compared between medial and lateral rectus muscles. Cross sections from medial and lateral rectus muscle resection specimens were stained for elastin to quantify arterial volume in the distal tendons.

RESULTS

Twenty lateral and 22 medial rectus muscles from 31 patients were included. There was no significant difference in the mean number of major anterior ciliary arteries between lateral rectus muscles (2.25 +/- 0.79, range 1-4) and medial rectus muscles (2.05 +/- 0.65, range 1-3) (p = 0.46). The mean number of minor anterior ciliary arteries was 6.7 in both medial and lateral rectus muscles (p = 0.97). Resected rectus muscle tendons showed no significant difference between lateral and medial rectus muscles for arterial vessel number or cross-sectional area.

CONCLUSIONS

These results show the contribution from the lateral rectus muscle to the anterior segment circulation may be more robust than is commonly taught.

Instability of ocular alignment in childhood esotropia

OBJECTIVE

Instability of ocular alignment may cause surgeons to delay surgical correction of childhood esotropia. The authors investigated the stability of ocular alignment over 18 weeks in children with infantile esotropia (IET), acquired nonaccommodative esotropia (ANAET), or acquired partially accommodative esotropia (APAET).

DESIGN

Prospective, observational study.

PARTICIPANTS

Two hundred thirty-three children aged 2 months to less than 5 years with IET, ANAET, or APAET of less than 6 months' duration.

METHODS

Ocular alignment was measured at baseline and at 6-week intervals for 18 weeks.

MAIN OUTCOME MEASURES

Using definitions derived from a nested test-retest study and computer simulation modeling, ocular alignment was classified as unstable if there was a change of 15 prism diopters (PD) or more between any 2 of the 4 measurements, as stable if all 4 measurements were within 5 PD or less of one another, or as uncertain if neither criteria was met.

RESULTS

Of those who completed all 3 follow-up visits within time windows for analysis, 27 (46%) of 59 subjects with IET had ocular alignment classified as unstable (95% confidence interval [CI], 33%-59%), 20% as stable (95% CI, 11%-33%), and 34% as uncertain (95% CI, 22%-47%). Thirteen (22%) of 60 subjects with ANAET had ocular alignment classified as unstable (95% CI, 12%-34%), 37% as stable (95% CI, 25%-50%), and 42% as uncertain (95% CI, 29%-55%). Six (15%) of 41 subjects with APAET had ocular alignment classified as unstable (95% CI, 6%-29%), 39% as stable (95% CI, 24%-56%), and 46% as uncertain (95% CI, 31%-63%). For IET, subjects who were older at presentation were less likely to have unstable angles than subjects who were younger at presentation (risk ratio for unstable vs stable per additional month of age, 0.85; 99% CI, 0.74-0.99).

CONCLUSIONS

Ocular alignment instability is common in children with IET, ANAET, and APAET. The impact of this finding on the optimal timing for strabismus surgery in childhood esotropia awaits further study.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Predictive factors for vision loss after hematopoietic cell transplant for X-linked adrenoleukodystrophy

BACKGROUND

X-linked adrenoleukodystrophy (X-ALD) is an inherited disease characterized by cerebral demyelination, adrenal insufficiency, and progressive neurological deterioration. Hematopoietic cell transplantation (HCT) is the only effective treatment. Visual dysfunction is a common component of the disease and may continue to progress in patients after HCT. This study was designed to determine prognostic factors predictive of vision loss after HCT.

SUBJECTS AND METHODS

A retrospective chart review was performed for all boys who had HCT for cerebral X-ALD at the University of Minnesota between 1991 and 2002. Patients were included if they survived 100 days post-HCT and had pre- and post-HCT ophthalmology evaluation. Complete data were available for 14 patients. Patient characteristics examined included HLA match status, graft-versus-host disease prophylaxis, source of HCT, reason for diagnosis, age at treatment, magnetic resonance imaging (MRI) severity score, pattern of demyelination on MRI, and pretreatment performance intelligence quotient (IQ). Univariate analysis was performed for correlation with posttransplant visual acuity and optic disk pallor.

RESULTS

Factors significantly correlated with loss of visual acuity after HCT included pretransplant MRI severity score >11 (p = 0.03), pretransplant performance IQ <76 (p = 0.02), and the presence of pretransplant parieto-occipital demyelination on MRI (p = 0.03). Additionally, the presence of pretransplant parieto-occipital demyelination on MRI was found to correlate with the development of new optic disk pallor after HCT (p = 0.05).

CONCLUSIONS

This study identifies patient characteristics predictive of vision loss after HCT for X-ALD. Decisions about treatment for X-ALD rely heavily upon prognostic information about adverse outcomes following HCT. These findings will aid clinicians counseling patients considering HCT for X-ALD.

Botulinum toxin pretreatment augments the weakening effect of injection with ricin-mAb35 in rabbit extraocular muscle

PURPOSE

To examine force generation and duration of effect of botulinum toxin pretreatment, followed by injection of ricin-mAb35 in extraocular muscle.

METHODS

In normal adult rabbits, one superior rectus muscle was injected with either 5 units botulinum toxin or 1/50 maximally tolerated dose for rats (rMTD) of ricin-mAb35. Additional rabbits were first injected with 5 units botulinum toxin, and after 1, 2, or 4 weeks the same muscle was injected with either 1/10 or 1/50 rMTD ricin-mAb35. In each treatment group, the contralateral muscle was injected with an equal volume of saline. After 12 weeks (1/50 rMTD) or 6 months (1/10 rMTD), the rabbits were euthanized. Both SR muscles were removed and assayed physiologically, using an in vitro apparatus.

RESULTS

Twelve weeks after treatment with either botulinum toxin or immunotoxin alone, only ricin-mAb35-treated muscles were weaker than control muscles at tetanic stimulation frequencies. Pretreatment with botulinum toxin prior to injection with immunotoxin, especially at shorter intervals between injections, resulted in significant decreases in twitch and tetanic force generation compared with controls and muscles treated with ricin-mAb35 only or botulinum toxin only. At 6 months, force generation was decreased from control only in muscles treated with the higher dose of ricin-mAb35. Botulinum toxin pretreatment did not augment this effect at 6 months.

CONCLUSIONS

Upregulation of postsynaptic nicotinic acetylcholine receptors caused by botulinum toxin pretreatment amplifies the reduction of force generation in extraocular muscle following secondary injection of the immunotoxin ricin-mAb35 within 3 months of treatment.

Myogenic growth factors can decrease extraocular muscle force generation: a potential biological approach to the treatment of strabismus

PURPOSE

Future pharmacologic treatment of strabismus may be optimized if drugs that are less potentially toxic to patients can be developed. Prior studies have shown that direct injection of extraocular muscles (EOMs) with insulin growth factor or fibroblast growth factor results in significant increases in the generation of EOM force. The purpose of this study was to examine the morphometric and physiological effects of direct EOM injection with the growth factors BMP4, TGFbeta1, Shh, and Wnt3A.

METHODS

One superior rectus muscle of normal adult rabbits was injected with BMP4, TGFbeta1, Shh, or Wnt3A. The contralateral muscle was injected with an equal volume of saline to serve as a control. After 1 week, the animals were euthanatized, and both superior rectus muscles were removed and assayed physiologically. The muscles were stimulated at increasing frequencies to determine force generation. A separate group of treated and control superior rectus muscles were examined histologically for alterations in total muscle cross-sectional area and myosin heavy chain isoform (MyHC) composition.

RESULTS

One week after a single injection of BMP4, TGFbeta1, Shh, or Wnt3A, all treated muscles showed significant decreases in generation of force compared with control muscles. BMP4, TGFbeta1, Shh, and Wnt3A significantly decreased the mean myofiber cross-sectional area of fast MyHC-positive myofibers. BMP4 resulted in a conversion of fast-to-slow myofibers and a significant decrease in the percentage of developmental and neonatal MyHC-positive myofibers. Alterations in mean cross-sectional area and proportion of MyHCs were seen after injection with TGFbeta1, Shh, and Wnt3A. TGFbeta1 and BMP4 injections resulted in increased Pax7-positive satellite cells, whereas BMP4, TGFbeta1, and Wnt3A resulted in a decrease in MyoD-positive satellite cells.

CONCLUSIONS

These results suggest that, rather than using toxins or immunotoxins, a more biological approach to decrease muscle strength is possible and demonstrate the potential utility of myogenic signaling factors for decreasing EOM strength. Ongoing drug-delivery studies will elucidate means of extending treatment effect to make such agents clinically useful.

Increasing muscle strength as a treatment for strabismus: sustained release of insulin-like growth factor-1 in rabbit extraocular muscle

PURPOSE

Currently, no drug treatment is available for strengthening underacting extraocular muscles (EOM) in strabismus. We showed previously that single injections of insulin-like growth factor (IGF-1) result in significant but short-term increases in muscle force generation. This study examined the effects of sustained release of IGF-1 on force generation in rabbit superior rectus muscles.

METHODS

In adult rabbits, slow-release pellets containing IGF-1 were implanted on the global side of one superior rectus muscle. After 1 week, or 1, 2, 3, or 6 months, treated and control muscles were examined for force generation using an in vitro physiology apparatus. All muscles were prepared for histology and mean myofiber cross-sectional areas were determined.

RESULTS

One and 3 months after pellet implantation, treated muscles generated significantly greater force than contralateral control muscles, whereas at 2 months, no significant difference was found. Force per cross-sectional area (mN/cm(2)) at 3 months also increased significantly in the treated muscles. Mean muscle cross-sectional area increased significantly after 1, 2, and 3 months of sustained exposure to IGF-1 compared with controls. After an additional 3 months without IGF-1 exposure, mean cross-sectional areas were significantly greater than controls but significantly reduced compared with areas at 1, 2, and 3 months.

CONCLUSIONS

IGF-1 appears to be highly effective in increasing muscle force generation. Because slow release of IGF-1 results in sustained increases in EOM force generation, it may be a potentially useful alternative to surgical resection procedures because it avoids many of the potential long-term biomechanical hazards of resection surgery.

Increased extraocular muscle strength with direct injection of insulin-like growth factor-I

PURPOSE

Previous work has demonstrated the effectiveness of insulin-like growth factor (IGF)-II in increasing force generation in extraocular muscle (EOM). Studies in the literature have suggested that IGF-I would be even more effective than IGF-II. This study was performed to assess the effects on muscle mass and force generation of IGF-I injection in adult rabbit superior rectus muscle.

METHODS

Adult rabbits received a single injection of IGF-I at one of several doses into one superior rectus muscle. One week after treatment, the rabbits were euthanatized, and the superior rectus muscle from each orbit was removed. Force generation was measured using an in vitro apparatus, and injected muscles were compared with the contralateral control. A second group of animals were injected similarly, and the muscles were examined at 1 week for changes in cross-sectional area of individual myofibers.

RESULTS

EOMs demonstrate significant numbers of cells expressing the IGF receptor. After the EOMs were injected with IGF-I, there were significant increases both in muscle force generation and cross-sectional area at all doses tested in this study. Doses of 10 and 25 microg IGF-I were most effective.

CONCLUSIONS

Direct muscular injection of IGF-I effectively increases EOM force generation without the potential biomechanical hazards of surgery such as permanently altered muscle length or insertional position on the globe.

Strabismus and amblyopia in bilateral Peters anomaly

BACKGROUND

Peters anomaly is a rare form of anterior segment dysgenesis in which abnormal cleavage of the anterior chamber occurs at the end of the third week of gestation. We examined the prevalence of strabismus and amblyopia and analyzed predictive factors for their development, as well as the visual outcome and associated anomalies in patients with bilateral Peters anomaly.

METHODS

Using a retrospective review, we identified 25 consecutive patients with bilateral Peters anomaly who were observed between August 1995 and February 2005. Ocular structural and systemic anomalies, amblyopia therapy, visual acuity, and binocular alignment at last visit were recorded. Fisher's exact test was used to identify any association between defined predictive factors and the development of strabismus.

RESULTS

Mean follow-up time was 5.1 year (range, 0.5-21 years). Median age at presentation was 2.5 months (range, 1 day to 13 years). Penetrating keratoplasties were performed on 34 eyes in 20 patients. Final best-corrected visual acuity ranged from 20/25 to no light perception. Thirteen of 18 patients with recorded motility (72%) developed strabismus: esotropia (n = 7), exotropia (n = 5), and variable (n = 1); one also had dissociated vertical deviation. Patients with equal vision were either orthophoric (n = 4) or had intermittent esotropia (n = 1), whereas strabismus occurred in 100% of patients whose vision was asymmetric by more than 1.5 octaves. Asymmetric vision was the only statistically significant predictive factor for the development of strabismus (P = 0.002). Amblyopia treatment resulted in improved vision in 3 of 5 patients.

CONCLUSION

Strabismus occurs frequently in bilateral Peters anomaly. Asymmetric vision, (because of ocular structural anomalies) postoperative complications, and amblyopia may predispose to strabismus. Despite ocular structural limitations, amblyopia therapy is recommended in the aggressive rehabilitation of these eyes.

The effect of resection on satellite cell activity in rabbit extraocular muscle

PURPOSE

A common treatment for motility disorders of the extraocular muscles (EOMs) is a resection procedure in which there is surgical shortening of the muscle. This procedure results in rotation of the globe toward the resected muscle, increased resting tension across the agonist-antagonist pair, and stretching of the elastic components of the muscles. In the rabbit, due to orbital constraints and limited rotation, resection results in more significant stretch of the surgically treated muscle than the antagonist. This surgical preparation allows for the examination of the effects of surgical shortening of one rectus muscle and passive stretch of its ipsilateral antagonist.

METHODS

The insertional 6 mm of the superior rectus muscles of adult rabbits were resected and reattached to the original insertion site. After 7 and 14 days, the animals were injected intraperitoneally with bromodeoxyuridine (BrdU) every 2 hours for 12 hours, followed by a 24-hour BrdU-free period. All superior and inferior rectus muscles from both globes were examined for BrdU incorporation, MyoD expression, neonatal and developmental myosin heavy chain (MyHC) isoform expression, and myofiber cross-sectional area alterations.

RESULTS

In the resected muscle and in the passively stretched antagonist muscle, there was a dramatic increase in the number of myofibers positive for neonatal MyHC and in the number of BrdU- and MyoD-positive satellite cells. The addition of BrdU-positive myonuclei increased from 1 per 1000 myofibers in cross sections of control muscles to 2 to 3 per 100 myofibers in the resected muscles. Single myofiber reconstructions showed that multiple BrdU-positive myonuclei were added to individual myofibers. Addition of new myonuclei occurred in random locations along the myofiber length of single fibers. There was no correlation between myofibers with BrdU-positive myonuclei and neonatal MyHC isoform expression.

CONCLUSIONS

Both active and passive stretch of the rectus muscles produced by strabismus surgery dramatically upregulated the processes of satellite cell activation, integration of new myonuclei into existing myofibers, and concomitant upregulation of immature myosin heavy chain isoforms. Understanding the effects of strabismus surgery on muscle cell biological reactions and myofiber remodeling may suggest new approaches for improving surgical outcomes.

The natural history of glaucoma and ocular hypertension after pediatric cataract surgery

INTRODUCTION

We sought to define the prevalence and natural history of ocular hypertension and glaucoma for at least a 10-year period after pediatric cataract surgery.

METHODS

We conducted a prospective observational study of patients who received pediatric cataract surgery. Inclusion criteria included 2 directed ophthalmologic examinations performed at a minimum of 5 and 10 years after surgery.

RESULTS

A total of 63 patients (22 with bilateral cataracts and 41 with unilateral cataracts) were examined at a median of 15.1 year (range, 10.3-21.3 years) after surgery. A majority of the subjects had glaucoma or ocular hypertension (ie, 59%; 37/63). Nineteen percent (12/63) had glaucoma (5/22 with bilateral cataracts and 7/41 with unilateral cataracts). Approximately half (7/12) had developed glaucoma during the first 5-year observational period and the remainder (5/12) developed it during the following observational period. Forty percent (25/63) of the patients had ocular hypertension in at least one aphakic eye (9/23 with bilateral cataracts and 16/40 with unilateral cataracts). The rate of progression from ocular hypertension to glaucoma over a mean observational period of 7.2 years (range, 6.2-8.1 years) was 23% (5/22).

DISCUSSION

Patients who receive surgery for pediatric cataracts are at very high risk of developing ocular hypertension and glaucoma. Patients can develop late-onset glaucoma and ocular hypertension more than 10 years after surgery. Years of ocular hypertension may precede the diagnosis of late-onset glaucoma.

Botulinum toxin treatment of extraocular muscles in rabbits results in increased myofiber remodeling

PURPOSE

Botulinum toxin A (Botox) is commonly used for strabismus treatment. Although other muscles atrophy after intramuscular injection with Botox, extraocular muscles (EOMs) do not. A continuous process of myonuclear addition in normal uninjured adult myofibers in rabbit EOMs was studied. In this study, the effect of Botox-induced muscle paralysis on myofiber remodeling in adult EOMs was examined.

METHODS

The superior rectus muscles of adult rabbits were each injected with 5 units of Botox. The contralateral muscle received injections of saline only. Bromodeoxyuridine (BrdU) was administered for various periods after Botox treatment, followed by various BrdU-free periods. Myonuclear addition, the number of BrdU-positive satellite cells, and the number of MyoD-positive satellite cells were quantified, as were alterations in expression of immature myosins.

RESULTS

Intramuscular injection of Botox resulted in a significant increase in both the number of BrdU-positive myonuclei and satellite cells. MyoD expression in both satellite cells and myonuclei was significantly increased after Botox injection in EOMs. In Botox-treated EOMs, an increased number of myofibers positive for the neonatal myosin heavy chain (MyHC) isoform was detected in the orbital layer.

CONCLUSIONS

Botox-induced EOM paralysis resulted in a significant short-term increase in satellite cell activation and myonuclear addition in single myofibers in adult rabbit EOMs compared with control muscles. The appearance of MyoD-positive myonuclei suggests that protein synthesis becomes upregulated after Botox injection, and this, in turn, may help explain the minimal effects on myofiber size in EOMs after Botox injection. Understanding the effect of Botox on satellite cell activation and myonuclear addition in existing myofibers may suggest new ways to maximize the clinical effectiveness of Botox in patients with strabismus.

Referral patterns for common amblyogenic conditions

PURPOSE

The early detection and management of common pediatric ophthalmic problems is crucial to assure successful visual maturation and best potential for development of binocular vision. The referring physician plays a pivotal role in this process. This study was designed to investigate the prevailing referral patterns for common amblyogenic conditions in a defined geographic region.

METHODS

We sent a short questionnaire to 300 pediatricians and 1500 family practitioners (FPs) in Minnesota, asking them to use a multiple choice system to indicate how long after diagnosis they would wait before referring a child to an ophthalmologist for exotropia, esotropia, ptosis, nystagmus, and abnormal red reflex.

RESULTS

The response rate was 46.9% ( n = 117) for pediatricians and 17.9% ( n = 240) for FPs. Of respondents, 64.6% of pediatricians and 50.2% of FPs would refer patients with exotropia within 2 months of diagnosis ( P < 0.001). For esotropia, 58.8% of pediatricians would refer within 2 months, while 38.6% would wait up to 12 months. In comparison, 48.7% of FPs would refer sooner, while 47.9% would refer later. These differences in referral patterns for pediatricians and FPs were statistically significant ( P = 0.037). There was less variation for referral of ptosis, nystagmus, and abnormal red reflex. These referral patterns were unaffected by years in practice.

CONCLUSIONS

Pediatricians referred patients with strabismus significantly more promptly than FPs. The majority of primary care providers (PCPs) appropriately timed their referrals for these amblyogenic conditions. However, many children continue to be referred late, underscoring the need for continued education of PCPs.

Glaucoma following cataract surgery in children: surgically modifiable risk factors

PURPOSE

To determine the incidence of glaucoma following cataract surgery in children and to identify surgically modifiable risk factors that may influence the development of glaucoma in these eyes.

METHODS

All lensectomies performed in patients 18 years old or younger over a 7-year period (1995 through 2001) were identified by conducting a database search. A retrospective chart review was performed for every patient identified. Data extraction included patient's age at surgery, intraocular lens implantation at cataract extraction, date of glaucoma onset, and length of follow-up. Statistical methods included risk ratio calculations and Kaplan-Meier analyses for the "time to glaucoma" for eyes undergoing lensectomy.

RESULTS

We identified 116 eyes of 79 children in whom lensectomy was performed. The median age at cataract surgery was 178 days (approval 6 months). Mean follow-up time was 2.7 years. The overall incidence of glaucoma was 11%. Kaplan-Meier analysis demonstrated that eyes operated on at less than 30 days of age were statistically more likely to develop glaucoma than eyes operated on at age 30 days or older (P < .001). For those operated on at less than 30 days of age, the risk ratio was 11.8 for subsequent glaucoma development compared with those operated on at 30 days of age or older. Forty-nine eyes (42%) had primary intraocular lens implantation, and none of these developed glaucoma (P = .001).

CONCLUSIONS

Timing of surgery at less than 30 days of age and lack of implantation of an intraocular lens at lensectomy were both associated with an increased risk of subsequent glaucoma. Knowledge of modifiable risk factors is essential to allow ophthalmic surgeons to make cogent decisions regarding the care of children with cataracts.

Myotoxic effects of the skeletal muscle-specific immunotoxin, ricin-mAb35, on orbicularis oculi muscle after eyelid injections in rabbits

PURPOSE

The authors recently demonstrated that a single injection of the immunotoxin ricin-mAb35 has potent and long-lasting myotoxic effects in extraocular muscles. The myotoxicity of injected ricin-mAb35 was tested in the eyelids of rabbits to determine its potential for use in the treatment of benign essential blepharospasm and other dystonias.

METHODS

The immunotoxin ricin-mAb35 was injected in one eyelid of adult rabbits. After 1 week, 1 month, or 6 months, the rabbits were euthanized, and the eyelids were prepared for histologic examination of inflammatory cell infiltrate with immunohistochemical localization of cd11b and myosin heavy chain isoform expression. Muscle loss was quantified by analysis of muscle fiber cross-sectional area and total myofiber number.

RESULTS

Within the first week after a single injection of ricin-mAb35, some edema developed, which resolved by the second week. Otherwise, the eyelids were normal in appearance. A short-lived inflammatory response was seen at 1 week, but this resolved 1 month after treatment. One week after injection, there was a significant decrease in the total number of orbicularis oculi myofibers in the ricin-mAb35-treated eyelids. This myofiber loss remained significant 1 month later and was maintained 6 months after the initial injection.

CONCLUSIONS

Direct injection of the immunotoxin ricin-mAb35 resulted in significant, acute muscle loss in the orbicularis oculi of rabbits that was maintained for up to 6 months. Physiologic studies are needed to demonstrate concomitant loss of muscle strength, but these results suggest that ricin-mAb35 injection holds promise as a muscle-weakening agent in the eyelid.