The Effect of Horizontal Rectus Muscle Surgery on Distance-Near Incomitance.

PURPOSE: To determine the effect of horizontal rectus muscle surgery on distance-near incomitance. DESIGN: Prospective, comparative, interventional case series. METHODS: Prospective evaluation of patients >7 years old who had medial or lateral rectus muscle surgery at the University of Arkansas Medical Center or Arkansas Children's Hospital between December 2009 and January 2012. Prism and alternate cover testing was performed at distance (6 m) and near (0.3 m) fixation after >1 hour of monocular occlusion at preoperative and postoperative examinations within 1 week, and closest to 1 year after surgery. The change in distance-near incomitance was calculated. Patients with extraocular muscle fibrosis or paralysis were excluded. RESULTS: Forty-five patients met inclusion criteria. Twenty-five patients had medial rectus muscle surgery, and 20 patients had lateral rectus muscle surgery. Postoperative examinations showed a change in distance-near incomitance ≤10 prism diopters (PD) in 42 of 44 patients evaluated within 1 week after surgery and in all 28 patients evaluated 6-24 months after surgery. Horizontal rectus muscle surgery did not induce a clinically significant change in distance-near incomitance (±2 PD equivalence, TOST confidence interval, -1.8 +1.6 PD, P value = 0.014). Contrary to traditional teaching, medial rectus muscle surgery was not more likely to induce a greater effect at near fixation (P = 0.80) and lateral rectus muscle surgery was not more likely to induce a greater effect at distance fixation (P > 0.99). CONCLUSION: Horizontal rectus muscle surgery does not induce a clinically significant effect on distance-near incomitance. Contrary to traditional teaching, medial rectus muscle surgery does not induce a greater effect on ocular alignment at near fixation and lateral rectus muscle surgery does not induce a greater effect on ocular alignment at distance fixation. It is not necessary to consider distance-near incomitance when choosing between medial rectus and lateral rectus muscle surgery.

Fusional Amplitudes: Developing Testing Standards.

PURPOSE: The stability of binocular vision depends upon good fusional amplitudes, but the clinical assessment of fusional amplitudes varies around the world. The purpose of this study was to determine whether or not there is variation in the assessment of fusional amplitudes in normal subjects. The author looked at the testing distance, the order of testing, the role of examiner encouragement, and the subject's level of alertness. METHODS: In a prospective study using a modified crossover design, the author assessed fusional amplitudes in 99 subjects with normal eye exams. The measurements were done in two separate sessions on different days with each subject being randomized as to the order of fusional vergence testing. All subjects were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances. RESULTS: The author previously presented data on 50 subjects. In this expanded cohort, statistical significance was reached confirming the previous findings that convergence is significantly affected by encouragement, divergence is significantly reduced if assessed after convergence, and near amplitudes are significantly higher than distance amplitudes. Finally, there is a negative correlation between age and convergence break point. CONCLUSIONS: The results of this study demonstrate that divergence is significantly reduced if assessed after convergence in the subject with normal binocular function. Next, convergence is significantly affected by the use of encouragement. Measurements at near produced significantly higher results for all of the convergence and divergence tests. Finally, there is a significant negative correlation between age and convergence break point. We need to develop a standard of testing fusional amplitudes so there is consistency in the clinical assessment.

Unilateral strabismus surgery in patients with exotropia results in postoperative lateral incomitance.

PURPOSE: To determine whether unilateral strabismus surgery creates lateral incomitance in patients with exotropia. METHODS: Patients >7 years of age with intermittent or constant exotropia who underwent unilateral horizontal rectus muscle surgery between December 2009 and January 2012 were prospectively evaluated. Prism and alternate cover testing was performed with distance fixation in primary position, right gaze, and left gaze after 1 hour of monocular occlusion. Measurements were obtained within 1 month prior to surgery, within 1 week after surgery, and >3 months after surgery. The surgical procedure varied according to the surgeon's discretion. The change in deviation induced by strabismus surgery in lateral gaze was expressed as a percentage of the change in deviation induced in primary position. RESULTS: A total of 12 patients met inclusion criteria. Of the 11 patients with postoperative examinations within 1 week after surgery, 10 (91%) had greater surgical effect with gaze toward the operated eye (P = 0.007). All 9 patients with >3 months' follow-up had greater surgical effect with gaze toward the operated eye (P = 0.003). On average, the surgical effect in gaze toward the operated eye was 120% of that achieved in primary position; in gaze away from the operated eye, 75% (P < 0.001). Three patients had diplopia in lateral gaze toward the operated eye that remained >6 months after surgery. CONCLUSIONS: Unilateral strabismus surgery induces lateral incomitance that may cause diplopia >6 months after surgery in patients with exotropia. This should be considered when planning strabismus surgery and counseling patients.

DVD--a conceptual, clinical, and surgical overview.

Dissociated vertical deviation (DVD) is a slow, disconjugate hypertropic deviation of a nonfixating eye. It is usually bilateral, asymmetrical, and often associated with congenital esotropia. The deviating eye elevates, abducts, and excyclotorts. This type of strabismus is often variable, making measurement and clinical quantification difficult. Specific knowledge of the mechanisms and characteristics of the dissociated deviation are required for proper assessment and effective treatment. There is currently no consensus on the mechanisms and pathophysiology of DVD. In this workshop, participants discuss the characteristics and most current methods for assessing and quantifying the deviation and explore the potential etiologies, clinical characteristics, and indications for surgical intervention and nonsurgical management of DVD.

Fusional amplitudes: exploring where fusion falters.

BACKGROUND AND PURPOSE: The stability of binocular vision depends on good fusional amplitudes, but the assessment of fusional amplitudes varies around the world. The author reviewed the literature on fusional amplitudes and surveyed international orthoptists on their assessment of fusional amplitudes. The purpose of the study was to determine whether or not there is variation in fusional amplitudes in normal subjects when looking at the role of examiner encouragement; the order of testing; the method of testing; and the subject's level of alertness. The preliminary results from this ongoing, prospective study are presented. PATIENTS AND METHODS: Using a modified crossover design study, the author prospectively assessed fusional amplitudes in fifty participants with normal eye exams who met inclusion criteria. The measurements were done in two separate sessions with each participant being randomized as to the order of fusional vergence testing. All participants were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances. RESULTS: Convergence is significantly affected by encouragement and divergence is significantly reduced if assessed after convergence. Numbers were too small to get meaningful data on the effect of fatigue on final outcome measures. CONCLUSIONS: We need to develop consistency in assessing fusional amplitudes and agree upon a standard of testing. Variables such as the order of testing, whether or not encouragement is given, and a person's level of alertness can affect the final outcome. Encouragement should be done especially when assessing convergence fusional amplitudes and divergence should be assessed prior to convergence. Finally, it is important to note a patient's level of alertness during vergence testing, especially if they are feeling foggy on one visit and are alert on the next. By implementing these strategies into your assessment of fusional amplitudes, the examiner will know if a change in amplitudes is due to treatment effect or just testing method.

Learning to teach: a summary of the 3rd IOA Education Forum, June 26, 2012.

There is rising international interest in developing health care systems that are built on the basis of best evidence. However, it is a challenge to integrate evidence-based practice skills into existing educational courses in a manner that enables students to interpret and use such skills effectively. The 2012 IOA Education Forum provided a venue for educators to discuss strategies for teaching evidence-based practice (EBP) in different settings, including clinical practice, and develop the means to evaluate transfer of evidence into clinical practice. In addition, educators were given practical approaches and strategies on how to increase their effectiveness and efficiency using basic best-evidence-based principles of health profession education; including education theory, small group teaching, giving feedback, evaluation and teaching professionalism.

Functional benefits of sensory and motor evaluation before strabismus surgery.

Evaluating the sensory and motor status of your strabismus patient is an important part of the preoperative examination. However, not all clinicians follow the same protocol for this assessment. Many rely on personal experience to determine what tests to do. Is this enough? Interpreting the evidence regarding the proper preoperative exam for strabismus patients and incorporating it into your practice can help to enhance your postoperative results.

Dissociated horizontal deviation after surgery for infantile esotropia: clinical characteristics and proposed pathophysiologic mechanisms.

OBJECTIVE: To examine the results of reversed fixation testing in patients who develop consecutive exotropia after surgery for infantile esotropia. METHODS: The reversed fixation test was performed prospectively in 28 patients who developed consecutive exotropia after surgery for infantile esotropia. All patients were assessed for adduction weakness, latent nystagmus, dissociated vertical divergence, and neurologic disease. RESULTS: A positive reversed fixation test, indicating the presence of dissociated horizontal deviation, was found in 14 of 28 patients (50%) with consecutive exotropia. In patients with dissociated horizontal deviation, the exodeviation was usually smaller with the nonpreferred eye fixating than with the preferred eye fixating, and smaller with the preferred eye fixating than during periods of visual inattention or under general anesthesia. Dissociated horizontal deviation correlated with the findings of dissociated vertical divergence, but not with asymmetric adduction weakness, latent nystagmus, or neurologic disease. CONCLUSIONS: Dissociated horizontal deviation is a clinical expression of dissociated esotonus. The common clinical presentation of dissociated horizontal deviation as an intermittent exodeviation of 1 eye results from the superimposition of a dissociated esotonus on a baseline exodeviation.

Does infantile esotropia arise from a dissociated deviation?

Tonus refers to the effects of baseline innervation on musculature in the awake, alert state.(1) Since the normal anatomical resting position of the eyes is one of exodeviation, extraocular muscle tonus plays a vital physiologic role in establishing ocular alignment. Under normal conditions, binocular esotonus is superimposed on the baseline anatomical position of rest to maintain approximate ocular alignment, save for a minimal exophoria that is easily overcome by active convergence. When binocular visual input is preempted early in life, monocular fixation may give rise to a larger dissociated esotonus that gradually drives the 2 eyes into a "convergent" position, resulting in infantile esotropia.(2).

How to perform the reversed fixation test.

The reversed fixation test is a simple clinical test that was developed to visualize subtle dissociated deviations. In recent years, we have used this test to diagnose dissociated vertical divergence and dissociated horizontal deviation in the setting of complex strabismus. In this article, we describe our technique for performing and interpreting the reversed fixation test.

Ophthalmic manifestations of Wolf-Hirschhorn syndrome.

PURPOSE: Wolf-Hirschhorn syndrome is caused by partial deletion of the short arm of chromosome 4 (4p-). Common features include developmental delay, microcephaly, seizures, craniofacial anomalies, mental retardation, and cardiac defects. This article further describes the ocular manifestations of this rare disorder. METHODS: Charts of patients with 4p- from the University of Arkansas (n = 3) and the University of Minnesota (n = 7) were reviewed. Diagnosis was made by a geneticist and was confirmed by karyotype. Cytogenetic reports were available for review in eight patients. RESULTS: Ten patients (six females and four males) aged 4 months to 11 years were included. Ophthalmic findings included exodeviation (9/10), nasolacrimal obstruction (6/10), shallow orbits (3/10), epicanthal folds (3/10), foveal hypoplasia (3/10), upper lid coloboma (2/10), optic disk anomalies (2/10), downslanting palpebral fissures (2/10), microcornea (2/10), hypertelorism (1/10), nystagmus (1/10), and chorioretinal coloboma (1/10). Eight patients with 4p- had break points ranging from band 4p14 to 4p16.3. CONCLUSIONS: This study expands on previous reports of the ophthalmic phenotype in 4p- and includes the additional findings of foveal hypoplasia, nystagmus, shallow orbits, epicanthal folds, and upper lid colobomas. Ophthalmic findings in 4p- are variable, likely related to the size of the deletion.

Positive angle kappa: a sign of albinism in patients with congenital nystagmus.

PURPOSE: To determine whether the association of positive angle kappa and congenital nystagmus is a distinguishing feature of albinism. DESIGN: Observational case series. METHODS: Prospective examination of the location of the corneal light reflex in patients with albinism and idiopathic congenital nystagmus. RESULTS: A positive angle kappa in at least one eye was noted in 20/21 (95%) patients with albinism versus 4/12 (33%) patients with congenital nystagmus (P =.0003, Fisher exact test). A positive angle kappa in both eyes was noted in 15/21 (71.4%) patients with albinism versus 2/12 (16.6%) patients with idiopathic congenital nystagmus (P =.0039, Fisher exact test). CONCLUSION: A positive angle kappa in patients with congenital nystagmus is associated with albinism. The pathophysiology of the positive angle kappa may relate to the anomalous decussation of optic axons that characterizes the albinotic visual system.

Ocular outcomes in low birth weight premature infants with intraventricular hemorrhage.

PURPOSE: To study ocular outcomes in very low birth weight premature infants with intraventricular hemorrhage. METHODS: Parents of 490 consecutive very low birth weight (less than 1500 g) premature infants who were discharged from the neonatal intensive care unit of our hospital between 1994 and 1996 were asked to enroll their child/children in this cross-sectional study. Sixty infants (12%) were recruited and had complete masked ophthalmologic examinations at 12 months corrected gestational age. The medical records of each infant were reviewed after the eye examination was complete. The occurrence of intraventricular hemorrhage and other perinatal comorbidities was documented. Ocular outcomes of infants with no or low-grade (grades I-II) hemorrhages were compared with those of infants with high-grade (grades III-IV) intraventricular hemorrhage. RESULTS: Of the 60 infants examined, 17 (28%) had neonatal intraventricular hemorrhage. Eleven (18%) had high-grade intraventricular hemorrhage, and 49 (82%) had no or low-grade hemorrhage. Of the 11 infants with high-grade intraventricular hemorrhage, 8 (73%) had strabismus compared with 7 (14%) of 49 infants with no or low-grade hemorrhages who developed strabismus (P<0.001). The high-grade group also had a larger proportion of infants with ocular motility defects (P=0.008), nystagmus (P<0.001), optic nerve atrophy (P<0.001), and abnormal retinal findings (P=0.039). Additionally, these infants were more likely to have stage 3 or worse retinopathy of prematurity (P=0.003). CONCLUSIONS: These results confirm the findings of our earlier retrospective study, and suggest that the occurrence of high-grade intraventricular hemorrhage in the early postnatal period places these infants at significant risk for adverse ocular outcomes. These infants require close ophthalmologic surveillance.

Perinatal cortical and subcortical visual loss: mechanisms of injury and associated ophthalmologic signs.

PURPOSE: To determine whether term and preterm injuries to the retrogeniculate visual system are associated with recognizable patterns of ophthalmologic abnormalities and whether these patterns can be attributed to cortical (gray matter) or subcortical (white matter) injury. DESIGN: A retrospective case series. PARTICIPANTS: One hundred children with clinical and neuroimaging signs of perinatal posterior visual pathway injury who were examined at Arkansas Children's Hospital Eye Clinic between 1989 and 1999. METHODS: We reviewed magnetic resonance images or computed tomographic scans from 50 children with cortical (predominantly or exclusively involving cortical gray matter) and 50 children with subcortical (predominantly or exclusively involving subcortical white matter) perinatal injury to the retrogeniculate visual system. Ophthalmologic abnormalities were analyzed retrospectively in each group. MAIN OUTCOME MEASURES: Conjugate gaze deviation, type of strabismus, abnormal eye movements, and optic disc morphology. RESULTS: Horizontal conjugate gaze deviation, exotropia, and a normal optic disc appearance were significantly more common in cortical than in subcortical visual loss. Tonic downgaze, esotropia, and optic nerve hypoplasia (with or without coexisting pallor) were significantly more common in subcortical than in cortical visual loss. CONCLUSIONS: Perinatal cortical and subcortical visual loss produce differing profiles of ophthalmologic dysfunction. A reclassification of periventricular leukomalacia and other forms of retrogeniculate white matter injury as subcortical visual loss would increase diagnostic specificity.