Arvind Chandna

A new test of contour integration deficits in patients with a history of disrupted binocular experience during visual development

Previous studies have suggested that the integration of orientation information across space is impaired in amblyopia. We developed a method for quantifying orientation-domain processing using a test format that is suitable for clinical application. The test comprises a graded series of cards where each card includes a closed path (contour) of high contrast Gabor signals embedded in a random background of Gabor signals. Contour visibility in both normals and patients with histories of abnormal binocular vision depends jointly on the spacing of elements on the contour as well as background element density. Strabismic amblyopes show significant degradation of performance compared to normals. Small but significant losses in sensitivity were also observed in a group of non-amblyopic strabismus patients. Threshold measurements made with contrast reducing diffusers indicated that the amblyopic loss is not due to the reduced contrast sensitivity of the amblyopic eye. An abnormal pattern of long-range connectivity between spatial filters or a loss of such connectivity appears to be the primary source of contour integration deficits in amblyopia and strabismus.

Abatacept: a potential therapy in refractory cases of juvenile idiopathic arthritis-associated uveitis

BackgroundJuvenile idiopathic arthritis (JIA) is the most common of all systemic conditions associated with childhood uveitis. Visual impairment has been shown to be as high as 40% of which 10% being blind (6/60 or worse). Due to the lack of well-designed randomized control trials for paediatric uveitis and arthritis there are limited comparative data regarding the efficacy of single or combination treatments. Recently, abatacept was shown to control ocular inflammation in a case of psoriatic arthritis- associated uveitis, seven cases of JIA- associated uveitis and in JIA. We present two cases with JIA-associated uveitis who have responded dramatically to abatacept therapy following unsuccessful therapy with other immunosuppressants. Control of arthritis still represents a challenge with this treatment.MethodsProspective review of two patients with refractory JIA- associated uveitis not responding to maximum conventional treatment. Patients were regularly reviewed in the ophthalmology and rheumatology clinics. Assessment of their ocular condition was characterized according to the Standardization of Uveitis Nomenclature (SUN) group.ResultsIn case 1, ocular inflammation was brought under control after repeated abatacept infusions. Case 2 showed complete resolution of cystoids macular edema CME and improvement of 5 Snellen’s lines in best corrected visual acuity. After 9 months, the ocular condition of both patients remains in remission with steroid sparing. Joint disease was brought to clinical remission in case 2, but not in case 1.ConclusionsAbatacept is a promising alternative treatment in refractory cases of JIA uveitis but may not be as successful in controlling joint disease. Larger series with long term follow up of biological therapies in paediatric uveitis are essential to assess the efficacy and cost effectiveness.

CONTOUR DETECTION THRESHOLD : REPEATABILITY AND LEARNING WITH 'CONTOUR CARDS'

Human observers are able to locate contours that are defined solely on the basis of long-range, orientation-domain correlations. The integrity of the mechanisms responsible for second-order contour detection is disrupted by amblyopia (Kovacs et al., 1996; Hess et al., 1997) and it is therefore of interest to develop methods for assessing pediatric patients undergoing treatment for amblyopia. In this study, we have determined the inter-observer and test-retest reliability of a card-based test of second-order contour integration. The magnitude of practice effects was also assessed in both adult and pediatric patient groups. Contour detection thresholds were measured for a closed contour, defined by Gabor patches, embedded in a randomly oriented Gabor-patch background. The visibility of the contour was controlled by varying the density of the background elements. Thresholds, defined in terms of the ratio of contour element spacing to average background spacing were measured with a clinical staircase procedure. Thresholds measured by two observers differed on average by 0.023 +/- 0.075 or about one half the increment between cards. Children and adults showed only small practice effects (0.022 +/- 0.051 vs 0.053 +/- 0.077, respectively) and average unsigned differences between repeated measures were equivalent to approximately 1 card across groups. A card-based test of second-order contour integration produces reliable estimates of contour integration performance in normal and amblyopic observers, including children.

Binocular Fixation Pattern and Visual Acuity in Children With Strabismic Amblyopia

BACKGROUND A prospective study was undertaken to compare the binocular fixation pattern and presence of amblyopia in strabismic children. METHODS Fifty-three children with manifest strabismus and the ability to cooperate with an optotype acuity test were examined. The binocular fixation pattern and logMAR visual acuity were recorded by separate, masked observers under standardized conditions. The binocular fixation pattern was divided into four grades from alternation to uniocular fixation. RESULTS Patients who freely alternated did not have amblyopia, while those who maintained or preferred fixation with a given eye tended to have amblyopia in the nonpreferred eye. CONCLUSION The binocular fixation pattern can be rapidly assessed with minimal equipment and training. These findings confirm the usefulness of a graded assessment of the binocular fixation pattern in the detection of amblyopia.

Etanercept in methotrexate-resistant JIA-related uveitis.

ABSTRACT We report our results with systemic Etanercept in patients with juvenile idiopathic arthritis in a joint ophthalmology–rheumatology clinic at a tertiary hospital. Methods: Patients with JIA on Etanercept were identified from a dedicated uveitis database. A retrospective review of electronic and paper-based patient records was performed. Results: Nine patients with JIA and current or previous treatment with Etanercept were identified, including six females and three males. Five patients with previous or current uveitis were noted. A further four were under observation for uveitis and required Etanercept for their joint disease. All nine patients had previously been taking Methotrexate, which had a suboptimal response in controlling arthritis or uveitis. Six out of nine patients did not show any uveitis activity at their last follow-up. Eyes of three patients still show signs of active inflammation in the anterior chamber (two on Etanercept and one off Etanercept). Severely impaired visual acuity (PL) was recorded in both eyes of one patient with long-standing persistent uveitis. Moderate visual loss in one eye of one patient was seen. The remaining seven patients did not show any significant loss of vision. Intraocular inflammation was not induced in any patient started on Etanercept. Conclusion: Etanercept may be useful in controlling JIA-related uveitis or arthritis in a pediatric patient when Methotrexate has had a suboptimal response in controlling the inflammatory activity.

Oscillatory motion but not pattern reversal elicits monocular motion VEP biases in infantile esotropia

Patients with early disruptions of binocularity show cortical directional asymmetries in their steady state monocular VEP response to oscillatory motion. The VEP directional asymmetry is characterized by significant first harmonic components that show a 180 degrees difference in the response phase between the two eyes. By contrast, the normal response is dominated by even-order response harmonics, although some normal observers also have measurable responses at the first harmonic. Experiments and simulations were conducted to determine if the first harmonic in patients could reasonably be attributed to direction selective mechanisms. A secondary goal was to determine whether the first harmonic response of normals was also due to imbalances in direction selective mechanisms. Monocular steady state VEPs were elicited by oscillating 3 c/deg gratings presented at 6 and 10 Hz in normal observers and observers with infantile esotropia. Responses were also obtained to phase-reversing gratings of the same spatial and temporal frequencies. Phase reversal eliminated the majority of first harmonic responses which were recorded for normal observers to oscillatory motion. However, phase reversal did not elicit the cortical motion asymmetry in infantile esotropia. Modeling results suggest that the first harmonic response to oscillatory motion arises due to non-linearities in both direction selective and non-direction-selective mechanisms, with the latter being dominant in patients with early onset strabismus.

Horner's syndrome and sixth nerve paresis secondary to a petrous internal carotid artery aneurysm.

We describe a report of a child with a horner’s syndrome and sixth nerve paresis secondary to a petrous internal carotid artery (ICA) aneurysm. Management of this condition involved coiling of the aneurysm and the use of botulinum toxin to manage his strabismus and associated symptoms.

Pattern Recognition of Vertical Strabismus Using an Artificial Neural Network (StrabNet

Background: Our goal is to develop an accessible expert system (StrabNet) that will assist in the clinical diagnosis of vertical strabismus, form the basis of a teaching/learning tool, and contribute to the audit process. Potentially, this model can be extended to other strabismus deviations. Methods: Vertical deviations were separated into eight classifications (diagnoses). An expert system based on architecture of artificial neural networks learned the patterns for each class of deviation based on 10 prism cover-test measurements (9 cardinal positions and near fixation). The expert system was tested with previously unseen and real-patient data. This system was extended to a reduced model requiring only six measurements (primary position, right, left, up, down gaze, and near fixation), and evaluated with real patient data. A freely available Web implementation is available on the Internet at www.StrabNet.com. Results: The expert system was found to be highly accurate at diagnosing vertical strabismus (100% and ≈96% for ten and six measurement models, respectively) from one of the eight classes. Conclusion: StrabNet is of demonstrable value in diagnosing commonly presenting vertical deviations from prism cover test (PCT) measurements. Its potential role in teaching and in audit is identified.

Corneal endothelial dysfunction in Pearson syndrome

Mitochondrial disorders are associated with well recognized ocular manifestations. Pearson syndrome is an often fatal, multisystem, mitochondrial disorder that causes variable bone marrow, hepatic, renal and pancreatic exocrine dysfunction. Phenotypic progression of ocular disease in a 12-year-old male with Pearson syndrome is described. This case illustrates phenotypic drift from Pearson syndrome to Kearns-Sayre syndrome given the patient’s longevity. Persistent corneal endothelial failure was noted in addition to ptosis, chronic external ophthalmoplegia and mid-peripheral pigmentary retinopathy. We propose that corneal edema resulting from corneal endothelial metabolic pump failure occurs within a spectrum of mitochondrial disorders.

Spontaneous Consecutive Exotropia in Childhood

Purpose: Consecutive exotropia is commonly the result of a surgical correction of a primary esotropia but may develop spontaneously. This study examines the clinical characteristics of patients who have developed a spontaneous consecutive exotropia and relates the key features to previously reported findings. Methods: Patients were identified by routine clinical practice from May 2000 to December 2003 by retrospective case note analysis. Patients that presented with an esotropia that became an exotropia (without surgery or botulinum toxin A) were included. Results: This study consisted of 14 patients who presented with an esotropia from early weeks of life to almost 4 years. No patients were undergoing occlusion treatment at the onset of the exotropia and no subject had dense amblyopia. The most common characteristics included (1) age of onset of esotropia of 24 months or less; (2) hypermetropic refractive error of +5 DS mean spherical equivalent; (3) lack of binocular single vision. Conclusion: The results highlight the variability of the condition with no single consistent finding, with the lack of binocular single vision, early onset esotropia, and high hypermetropia being common findings. Amblyopia was not found to be an important characteristic.