Strabismus

Strabismus Publications

Whitman MC. Axonal Growth Abnormalities Underlying Ocular Cranial Nerve Disorders. Annu Rev Vis Sci 2021;Abstract
Abnormalities in cranial motor nerve development cause paralytic strabismus syndromes, collectively referred to as congenital cranial dysinnervation disorders, in which patients cannot fully move their eyes. These disorders can arise through one of two mechanisms: (a) defective motor neuron specification, usually by loss of a transcription factor necessary for brainstem patterning, or (b) axon growth and guidance abnormalities of the oculomotor, trochlear, and abducens nerves. This review focuses on our current understanding of axon guidance mechanisms in the cranial motor nerves and how disease-causing mutations disrupt axon targeting. Abnormalities of axon growth and guidance are often limited to a single nerve or subdivision, even when the causative gene is ubiquitously expressed. Additionally, when one nerve is absent, its normal target muscles attract other motor neurons. Study of these disorders highlights the complexities of axon guidance and how each population of neurons uses a unique but overlapping set of axon guidance pathways. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Binenbaum G, Chang MY, Heidary G, Morrison DG, Trivedi RH, Galvin JA, Pineles SL. Botulinum Toxin Injection for the Treatment of Strabismus: A Report by the American Academy of Ophthalmology. Ophthalmology 2021;Abstract
PURPOSE: To review the available evidence comparing the effectiveness of extraocular muscle botulinum toxin type A (BTXA) injection with eye muscle surgery for restoring ocular alignment in children and adults with nonparalytic, nonrestrictive horizontal strabismus. METHODS: Literature searches in the PubMed Cochrane Library, and clinical trial databases with no date restrictions, but limited to articles published in English, were conducted last on January 10, 2021. The searches yielded 515 citations, 40 of which were reviewed in full text by the first author. Fourteen articles met the criteria for inclusion (randomized or nonrandomized comparative studies, or case series with a minimum 50 patients; evaluating extraocular muscle BTXA injection for initial or repeat treatment of horizontal, nonparalytic, nonrestrictive strabismus; with at least 6 months of follow-up) and were graded by a methodologist. RESULTS: The 14 included studies consisted of 2 randomized clinical trials, 3 nonrandomized comparative studies, and 9 case series. All 5 comparative studies were graded level II evidence, and the 9 case series were graded level III evidence. Successful motor outcomes after BTXA injection were relatively consistent across 4 of the 5 comparative studies at 60%, when adjustment was made for differential selection bias in 1 of the studies. In the 4 studies, successful motor outcomes after surgery ranged from 66% to 77% with a mean follow-up of 23 to 75 months, and the outcomes were not significantly different from those after BTXA injection. In the fifth level II study, success was significantly higher with BTXA injection than with surgery (94% vs. 72%). The level III BTXA case series demonstrated higher motor success rates of 87% to 89% when children were treated in 2 muscles at a time; rates were lower in adults treated with single-muscle BTXA injection. CONCLUSIONS: Extraocular muscle injection of BTXA achieves a high rate of successful motor alignment, comparable with that achieved after eye muscle surgery for nonparalytic, nonrestrictive horizontal strabismus. Good alignment may require multiple BTXA injections, and it is not yet clear whether sensory outcomes are equivalent for BTXA injections versus eye muscle surgery in young children.
Cheng W, Lynn MH, Pundlik S, Almeida C, Luo G, Houston K. A smartphone ocular alignment measurement app in school screening for strabismus. BMC Ophthalmol 2021;21(1):150.Abstract
BACKGROUND: Strabismus is the leading risk factor for amblyopia, which should be early detected for minimized visual impairment. However, traditional school screening for strabismus can be challenged due to several factors, most notably training, mobility and cost. The purpose of our study is to evaluate the feasibility of using a smartphone application in school vision screening for detection of strabismus. METHODS: The beta smartphone application, EyeTurn, can measure ocular misalignment by computerized Hirschberg test. The application was used by a school nurse in a routine vision screening for 133 elementary school children. All app measurements were reviewed by an ophthalmologist to assess the rate of successful measurement and were flagged for in-person verification with prism alternating cover test (PACT) using a 2.4Δ threshold (root mean squared error of the app). A receiver operating characteristic (ROC) curve was used to determine the best sensitivity and specificity for an 8Δ threshold (recommended by AAPOS) with the PACT measurement as ground truth. RESULTS: The nurse obtained at least one successful app measurement for 93% of children (125/133). 40 were flagged for PACT, of which 6 were confirmed to have strabismus, including 4 exotropia (10△, 10△, 14△ and 18△), 1 constant esotropia (25△) and 1 accommodative esotropia (14△). Based on the ROC curve, the optimum threshold for the app to detect strabismus was determined to be 3.0△, with the best sensitivity (83.0%), specificity (76.5%). With this threshold the app would have missed one child with accommodative esotriopia, whereas conventional screening missed 3 cases of intermittent extropia. CONCLUSIONS: Results support feasibility of use of the app by personnel without professional training in routine school screenings to improve detection of strabismus.
Scelfo C, Elhusseiny AM, Alkharashi M. Effect of inferior oblique myectomy on primary position when combined with lateral rectus recession for intermittent exotropia. Eur J Ophthalmol 2021;:11206721211002706.Abstract
PURPOSE: To evaluate the surgical success and need for adjustment due to overcorrection in patients who undergo inferior oblique myectomy (IOM) combined with lateral rectus recession (LRc) for intermittent exotropia in the setting of inferior oblique overaction. METHODS: A retrospective chart review was conducted of patients with intermittent exotropia who underwent LRc using adjustable sutures alone versus LRc combined with IOM between January 2010 and July 2018 at our institution. Binocular alignment was recorded before and within one week of surgery. Evaluation measures noted were surgical success (defined as distance alignment of ⩽10 prism diopters) and need for postoperative adjustment due to overcorrection. RESULTS: Of 48 patients, 24 underwent LRc alone and 24 underwent LRc combined with IOM; all 48 patients had adjustable sutures. Surgical success was significantly higher in the LRc alone group (91.6%) compared with the LRc with IOM group (62.5%) ( = 0.036). The need for postoperative adjustment due to overcorrection was also significantly higher in the LRc with IOM group (20.8%) compared with the LRc alone group (0%) ( = 0.049). CONCLUSIONS: In this study, more patients needed adjustment for overcorrection after undergoing LRc combined with IOM versus LRc alone. Since the tertiary action of the inferior oblique is abduction it is possible that, in patients with inferior oblique overaction, surgically weakening the inferior oblique causes more esodeviation and overcorrection. Thus, surgical correction of exotropia and inferior oblique overaction using LRc combined with IOM may lead to overcorrection and increased need for postoperative adjustment.
Serafino M, Granet DB, Kushner BJ, Dagi LR, Kekunnaya R, Nucci P, Kreatsoulas C. Definition of successful outcomes after surgery for each type of strabismus: a Delphi study. J AAPOS 2021;Abstract
BACKGROUND: The Delphi process has been widely used to delineate guidelines for the treatment of disorders for which there is little or no evidence in the published literature. The purpose of this study was to use the Delphi process to identify areas of consensus and disagreement on the definition of success after surgery for each type of strabismus. METHODS: Two rounds of electronic questionnaires were sent to 28 members of the Strabismus Success Definition Delphi Study Group. For the first round, responses to 70 questions were captured as agree (= 1) and disagree (= 2). For round 2, a total of 89 questions were captured on a Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Consensus was determined a priori at 85%. RESULTS: In both the first and second rounds, inter-rater agreement of 85% consensus was reached for only 20% of questions. Intra-rater agreement per question was low, with κ values ranging from -0.11 to 0.62. Intra-rater agreement was also low among themes, ranging from poor to fair agreement: κ = 0.25 for motor, κ = 0.28 for sensory, and κ = 0.35 for follow-up. CONCLUSIONS: This study highlights consensus areas that could be considered by researchers in designing studies and identifies areas where lack of consensus indicates that further research is needed.
Wan MJ, AlShaker S, Hunter DG. Use of Botulinum Toxin in Ophthalmology. Handb Exp Pharmacol 2021;263:147-160.Abstract
Botulinum toxin is an important treatment for many conditions in ophthalmology, including strabismus, nystagmus, blepharospasm, hemifacial spasm, spastic and congenital entropion, corneal exposure, and persistent epithelial defects. The mechanism of action of botulinum toxin for both strabismus and nystagmus is the neuromuscular blockade and transient paralysis of extraocular muscles, but when botulinum toxin is used for some forms of strabismus, a single injection can convey indefinite benefits. There are two unique mechanisms of action that account for the long-term effect on ocular alignment: (1) the disruption of a balanced system of agonist-antagonist extraocular muscles and (2) the reestablishment of central control of alignment by the binocular visual system. For other ocular conditions, botulinum toxin acts through transient paralysis of periocular muscles. Botulinum toxin is a powerful tool in ophthalmology, achieving its therapeutic effects by direct neuromuscular blockade of extraocular and periocular muscles and by unique mechanisms related to the underlying structure and function of the visual system.
Dagi LR, Elhusseiny AM. Adjustable graded augmentation of superior rectus transposition for treatment of abducens nerve palsy and Duane syndrome. J AAPOS 2020;Abstract
PURPOSE: To report the results of adjustable graded augmentation of superior rectus transposition, a novel modification of superior rectus transposition (SRT) designed to reduce postoperative vertical or torsional diplopia. METHODS: The medical records of patients who underwent adjustable graded augmentation of SRT with or without adjustable medial rectus recession (MRc) from February 2017 to December 2019 were reviewed retrospectively. A Mendez ring was used to monitor torsional change after transposition of the superior rectus muscle to the lateral rectus muscle and after sequential placement of 2 or 3 augmentation sutures by superior rectus-lateral rectus loop myopexy. If excessive mechanical intorsion was induced, the responsible augmentation suture was severed intraoperatively. If torsional or vertical diplopia was noted after recovery, the distal-most augmentation suture was cut. Exotropia was managed by severing the distal-most augmentation suture or by medial rectus adjustment. RESULTS: A total of 8 patients who underwent adjustable graded augmentation of SRT were included (6 using the 3-suture technique): 3 for esotropic Duane syndrome, 2 for abducens nerve palsy, 1 for Moebius syndrome, and 2 for combined trochlear and abducens nerve palsies. Of the 8 patients, 4 had prior strabismus surgery, and 1 patient had previously undergone treatment with botulinum toxin. Severing one augmentation suture in 3 cases resolved vertical (n = 2) or torsional (n = 1) diplopia and consecutive exotropia (n = 1), resulting in excellent alignment and reduction of torticollis to <4° in 7 cases. The technique proved insufficient in 1 patient, who had undergone 3 prior strabismus procedures. CONCLUSIONS: In this study cohort, adjustable graded augmentation of SRT effectively managed the risk of postoperative vertical or torsional diplopia.
Elhusseiny AM, Gore C, Sadiq MAA, Dagi LR, Kazlas M, Hunter DG. Self-grading effect of inferior oblique myectomy and recession. J AAPOS 2020;Abstract
PURPOSE: To evaluate the outcomes of inferior oblique (IO) weakening surgery, whether recession or myectomy, and to assess the dose-response relationship and correlation with angle of preoperative hypertropia. METHODS: The medical records of all patients with vertical deviation in primary gaze who underwent unilateral IO-weakening surgery, either recession or myectomy, at Boston Children's Hospital over an 8-year period with a minimum postoperative follow-up of 1 month were reviewed retrospectively. Outcome measures were effect of IO weakening surgery on vertical deviation in primary gaze and its correlation with the preoperative angle of hyperdeviation. Secondary outcomes included resolution of abnormal head posture, reduction of ocular torsion, and postoperative under- and overcorrection RESULTS: A total of 94 patients were identified (mean age at surgery, 29.3 ± 19.8 years; range, 1-69). The mean postoperative follow-up period was 17.2 ± 15 months. IO recession was performed in 30 patients; IO myectomy, in 64. Surgical success in primary position was achieved in 72 patients (77%), with resolution of anomalous preoperative head posture in 93%. The mean effect on alignment in primary position was 11.3 ± 6.8. The response to IO-weakening surgery was strongly correlated with the preoperative hyperdeviation for both recession (R = 0.53) and myectomy (R = 0.87). CONCLUSIONS: As with other types of strabismus surgery, IO weakening has a "self-grading" contribution, in which the surgical effect strongly correlates with the magnitude of preoperative deviation. A large range of vertical misalignment can be corrected with the same surgical approach.
Whitman MC, Di Gioia SA, Chan W-M, Gelber A, Pratt BM, Bell JL, Collins TE, Knowles JA, Armoskus C, Pato M, Pato C, Shaaban S, Staffieri S, MacKinnon S, Maconachie GDE, Elder JE, Traboulsi EI, Gottlob I, Mackey DA, Hunter DG, Engle EC, Engle EC. Recurrent Rare Copy Number Variants Increase Risk for Esotropia. Invest Ophthalmol Vis Sci 2020;61(10):22.Abstract
Purpose: To determine whether rare copy number variants (CNVs) increase risk for comitant esotropia. Methods: CNVs were identified in 1614 Caucasian individuals with comitant esotropia and 3922 Caucasian controls from Illumina SNP genotyping using two Hidden Markov model (HMM) algorithms, PennCNV and QuantiSNP, which call CNVs based on logR ratio and B allele frequency. Deletions and duplications greater than 10 kb were included. Common CNVs were excluded. Association testing was performed with 1 million permutations in PLINK. Significant CNVs were confirmed with digital droplet polymerase chain reaction (ddPCR). Whole genome sequencing was performed to determine insertion location and breakpoints. Results: Esotropia patients have similar rates and proportions of CNVs compared with controls but greater total length and average size of both deletions and duplications. Three recurrent rare duplications significantly (P = 1 × 10-6) increase the risk of esotropia: chromosome 2p11.2 (hg19, 2:87428677-87965359), spanning one long noncoding RNA (lncRNA) and two microRNAs (OR 14.16; 95% confidence interval [CI] 5.4-38.1); chromosome 4p15.2 (hg19, 4:25554332-25577184), spanning one lncRNA (OR 11.1; 95% CI 4.6-25.2); chromosome 10q11.22 (hg19, 10:47049547-47703870) spanning seven protein-coding genes, one lncRNA, and four pseudogenes (OR 8.96; 95% CI 5.4-14.9). Overall, 114 cases (7%) and only 28 controls (0.7%) had one of the three rare duplications. No case nor control had more than one of these three duplications. Conclusions: Rare CNVs are a source of genetic variation that contribute to the genetic risk for comitant esotropia, which is likely polygenic. Future research into the functional consequences of these recurrent duplications may shed light on the pathophysiology of esotropia.
Dagi LR, Velez FG, Archer SM, Atalay HT, Campolattaro BN, Holmes JM, Kerr NC, Kushner BJ, MacKinnon SE, Paysse EA, Pihlblad MS, Pineles SL, Strominger MB, Stager DR, Stager D, Capo H. Adult Strabismus Preferred Practice Pattern®. Ophthalmology 2020;127(1):P182-P298.
Elhusseiny AM, Huynh EM, Dagi LR. Evaluation and Management of V pattern Strabismus in Craniosynostosis. J Binocul Vis Ocul Motil 2019;:1-6.Abstract
V pattern strabismus is the most common ocular motor disorder reported in patients with craniosynostosis. Strabismus management may prove challenging, and few studies provide perspective on surgical approach. The purpose of this review is to discuss evaluation and surgical options for treating V pattern strabismus in patients with craniosynostosis. We provide a step-by-step approach to facilitate surgical planning.
Serafino M, Granet DB, Kushner BJ, Dagi LR, Kekunnaya R, Nucci P. Use of the Delphi process for defining successful outcomes for strabismus surgery. J AAPOS 2019;23(6):309-312.Abstract
The purpose of this review was to identify areas of consensus and disagreement among experts for the definition of success following strabismus surgery using the Delphi process. Three rounds of electronic questionnaires were sent to a panel of 28 strabismus experts. Throughout the process, members of the panel were masked to one another's identities to minimize the possibility of influence among members. Prior to data collection, we defined consensus as an 85% agreement on the answer to each question. Questions for which there was no consensus were reworded, and the resultant new questions were used in each subsequent round of questioning. We arrived at consensus for 23 of the 36 questions (64%). Consensus was obtained for recommending unique criteria for the definition of success for certain specific strabismus conditions. In addition, it was considered important that stereopsis and the range of single binocular vision be included in the definition of success for certain types of strabismus.
Heidary G, MacKinnon S, Elliott A, Barry BJ, Engle EC, Hunter DG. Outcomes of strabismus surgery in genetically confirmed congenital fibrosis of the extraocular muscles. J AAPOS 2019;Abstract
PURPOSE: To detail surgical strategy and strabismus outcomes in a genetically defined cohort of patients with congenital fibrosis of the extraocular muscles (CFEOM). METHODS: A total of 13 patients with genetically confirmed CFEOM (via genetic testing for mutations in KIF21A, PHOX2A, and TUBB3) were retrospectively identified after undergoing strabismus surgery at Boston Children's Hospital and surgical outcomes were compared. RESULTS: Age at first surgery ranged from 11 months to 63 years, with an average of 3 strabismus procedures per patient. Ten patients had CFEOM1, of whom 9 had the KIF21A R954W amino acid (AA) substitution and 1 had the M947T AA substitution. Of the 3 with CFEOM3, 2 had the TUBB3 E410K AA substitution, and 1 had a previously unreported E410V AA substitution. CFEOM1 patients all underwent at least 1 procedure to address chin-up posture. Chin-up posture improved from 24° ± 8° before surgery to 10.0° ± 8° postoperatively (P < 0.001). Three CFEOM1 patients developed exotropia after vertical muscle surgery alone; all had the R954W AA substitution. Postoperatively, 1 CFEOM1 patient developed a corneal ulcer. All CFEOM3 patients appeared to have underlying exposure keratopathy, successfully treated with prosthetic replacement of the ocular surface ecosystem (PROSE) lens in 2 patients. CONCLUSIONS: CFEOM is a complex strabismus disorder for which surgical management is difficult. Despite an aggressive surgical approach, multiple procedures may be necessary to achieve a desirable surgical effect. Knowledge of the underlying genetic diagnosis may help to inform surgical management.

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