Comparing the RETeval® portable ERG device with more traditional tabletop ERG systems in normal subjects and selected retinopathies.

PURPOSE: Our study aimed to determine if ISCEV standard-like ERGs recorded with the LKC RETeval® portable ERG unit compared to those obtained using the more traditional tabletop unit. METHODS: ERGs recorded from normal subjects and patients affected with retinal ON and OFF pathway anomalies were compared. Analysis included peak time and amplitude measurements as well as time-frequency domain analysis with the discrete wavelet transform of waveforms obtained with the two systems. RESULTS: Although both systems were similarly able to record reliable and highly reproducible ERG responses, there were major discrepancies in ERG responses between the portable and tabletop units, pointing toward a weaker stimulation of the retinal OFF pathway with the portable RETeval® unit. CONCLUSION: The portable RETeval® unit appears to be able to record highly reproducible and diagnostically useful clinical ERGs, albeit with some significant differences in waveform composition compared to those obtained with more standard tabletop systems. Given the unknown origin of these waveform discrepancies, if left uncorrected, these differences could potentially lead to erroneous interpretation when used in the clinical context and/or compared to ERGs recorded using more traditional table top units. Clearly, more research is warranted before handheld devices, such as the RETeval®, can be homologated as a diagnostically sound ERG devices.

Organic visual loss measured by kinetic perimetry and retinal electrophysiology in children with functional amblyopia.

PURPOSE: To demonstrate an organic (retinal) amblyogenic defect in functional amblyopes not responding to treatment. METHODS: Twenty-four children (Mean age: 5.9 ± 1.8 years; range: 4-10 years) with functional amblyopia were recruited for this study. All these children underwent complete ophthalmic and orthoptic evaluation. In addition, Kinetic Goldman Visual Fields (KGVF), Spectral Domain Optical Coherence Tomography (SD-OCT), full field flash electroretinograms (ffERG) and multifocal electroretinograms (mfERG) were also performed. Ratios were subsequently derived by comparing the amplitudes obtained from the amblyopic eye (AE) to the good eye (GE) for the a- and b-waves of the ffERG, as well as for the ring analysis of the mfERG. RESULTS: KGVF showed a central scotoma of varying size (3°-7°) and density (absolute to relative), with increasing target size in 14/24 patients whose best post-treatment vision in the AE ranged from 20/100 to 20/40. The scotoma decreased in size and density with improving vision until a plateau of recovery was reached. The remaining 10/24 patients with a vision ≥ 20/30 showed no scotoma. SD-OCT showed no significant difference between the AE and GE. ffERG and mfERG were obtained in 18/24 patients. The ffERG AE/GE ratio was abnormal in 7 patients, 5 of which had large scotomas on KGVF. The mfERG ring 1 AE/GE ratio was significantly (p < .05) attenuated in 9/18 patients out of which 3 were no longer amblyopic. However, there was no significant difference (p > .05) in ring 1 AE/GE amplitude ratio between those who achieved 20/50-20/40 (.81 ± .26) and those with ≥ 20/25(.86 ± .25). CONCLUSIONS: The combined findings of central scotoma on KGVF and mfERG anomalies in patients who did not achieve optimal vision with treatment suggest an underlying organic defect impairing macular function.

Ring analysis of multifocal oscillatory potentials (mfOPs) in cCSNB suggests near-normal ON-OFF pathways at the fovea only.

PURPOSE: To investigate the center-periphery distribution of ON and OFF retinal responses in complete congenital stationary night blindness (cCSNB). METHODS: Photopic full-field flash ERGs (photopic ffERGs) and OPs (photopic ffOPs) and slow m-sequence (to enhance OP prominence) mfERGs (and filtered mfOPs) evoked by a 37 hexagon stimulus array were recorded from normal subjects and cCSNB patients. Discrete wavelet transform (DWT) analysis of photopic ffERGs and mfERGs was also performed in order to assess the contribution of the ON and OFF retinal pathways (i.e., OFF-to-ON ratio) in both cohorts. RESULTS: As expected, the photopic ffERG (and ffOPs) responses in cCSNB were devoid of the first two of the three OPs (i.e., OP2 and OP3 and OP4) normally seen on the ascending limb of the b-wave. A similar finding was also noted in the mfERGs (and mfOPs) of ring 4. In contrast, the mfERGs (and mfOPs) of ring 1 included all three OPs. DWT analysis revealed that while in normal subjects, the OFF-to-ON ratio of mfERGs slightly increased from rings 1 to 4 (from 0.61 ± 0.03 to 0.78 ± 0.04; p < 0.05; median: from 0.62 to 0.79; p < 0.05), in cCSNB this ratio increased significantly more [from 0.73 ± 0.13 (ring 1) to 1.18 ± 0.17 (ring 4); p < 0.05; median: 0.78 to 1.22; p < 0.05], hence from a normal ON-dominated ratio (central ring) to an OFF-dominated ratio (peripheral ring). CONCLUSIONS: Our results show a clear discrepancy of ON and OFF mfOP components in cCSNB. Responses originating from the most central ring (i.e., ring 1) disclosed a near-normal electrophysiological contribution (as revealed with the presence of OP2, OP3 and OP4 as well as with the DWT OFF-to-ON ratio) of the retinal ON and OFF pathways in mfERG (and mfOPs) responses compared to responses from the more peripheral ring (and ffOP) which are devoid of the ON OPs (i.e., OP2 and OP3).

Revealing a retinal facilitatory effect with the multifocal ERG.

PURPOSE: We have previously shown that the amplitude of the mfERG response obtained to a single (large) hexagon is significantly smaller than that obtained when summating all the mfERG responses evoked to an array of 7-61 hexagons covering the same retinal area. The purpose of this study was to confirm our initial findings in normal subjects of different ages and in selected patients. METHODS: Binocular mfERGs (1, 7, 19, 37 and 61 hexagon arrays; Espion V6.0.54 Diagnosys LLC) were recorded from 40 normal subjects (25 aged 18-25, and 15 aged 3-12). Individual mfERG waveforms evoked in response to the multi-hexagon arrays (7, 19, 37 and 61) were summated, and the amplitude of the resulting composite mfERG waveform was compared to that measured in the response evoked to the single (large) hexagon stimulus to yield the amplitude ratio (i.e., 7:1 X100, 19:1X100, etc.). RESULTS: In normal subjects, the 7:1 ratio was 119.5 ± 9.2%, a value that gradually decreased to reach 109.4 ± 20.6% with the 61:1 ratio and a finding that was similar across all ages. CONCLUSION: The present study indicates a significant enhancement in amplitude of the summed mfERG composite waveform evoked to the 7 hexagon stimulus array (and to a lesser extent to the 19, 37 and 61 stimuli) compared to the 1 hexagon array, possibly mediated through the retinal lateral pathway (horizontal or amacrine cells), a claim that awaits confirmation. Preliminary results obtained from patients treated with Plaquenil suggest that this new method of mfERG analysis might probe a feature of macular function different from that investigated with the more usual method of mfERG ring ratio.

Optic pathway gliomas in patients with neurofibromatosis type 1: follow-up of 44 patients.

BACKGROUND: Children born with neurofibromatosis type 1 (NF1) have an increased risk of developing optic pathway gliomas (OPGs) during childhood. The aim of this study is to evaluate the clinical course of NF1 patients with OPGs at our institution with respect to visual and endocrinologic morbidity. METHODS: Retrospective case series of patients with OPGs and NF1 seen at the Montreal Children's Hospital, where screening imaging is performed on all NF1 patients. Details on patient demographics, tumor location, and progression of disease were recorded. RESULTS: Of 331 NF1 patient charts reviewed, 44 had confirmed OPG (13%). Average follow-up was 7 years. Mean age at presentation was 6 years, with 16 patients (36%) presenting past age 6. A total of 8 patients were symptomatic secondary to the OPG (defined as decreased vision or precocious puberty), with 5 of the 8 patients receiving treatment. These 8 patients all demonstrated chiasmal and/or retrochiasmal tumor in addition to nerve involvement. Final visual acuity was 20/40 or better in both eyes in 34 patients (77%); central, steady, and maintained in 3 preverbal children; and decreased vision secondary to OPG in 4 children (9%). CONCLUSIONS: OPGs can present and progress beyond the preschool years, and children should be screened with clinical ophthalmological examinations accordingly. The location of OPG as demonstrated on magnetic resonance imaging (MRI) cannot be used as a prognostic indicator because visual outcomes were similar between optic nerve/chiasmal and retrochiasmal tumors.

Optimal compliance for amblyopia therapy: occlusion with a translucent tape on the lens.

OBJECTIVE: To demonstrate that optimal compliance to amblyopia therapy and a better visual outcome can be achieved by occluding the lens over the preferred eye with a translucent tape. STUDY DESIGN: Prospective study of amblyopic children. PARTICIPANTS: Eighty-four amblyopic children recruited from 2000 to 2006 at the Montreal Children's Vision Centre. METHODS: A group of bilateral ametropes (mean age 3.8 years) were treated with glasses and occlusion of the sound eye with a translucent tape on the lens over the preferred eye, or an adhesive patch. The translucent tape reduced vision to hand motion at 0.3 m in the sound eye. Patients were divided into 2 groups depending on the treatment received. Group 1 (n = 36) was occluded with a translucent tape, and group 2 (n = 48) with a conventional adhesive patch, later replaced by the translucent tape. Twenty-five previously reported patients, treated with the conventional adhesive patch only, were used as controls (group 3). RESULTS: The mean amblyopic visual acuity was 20/100-2. Compliance was good in 36 patients (group 1), and was poor or deteriorated in 24/48 patients (group 2). Substituting the adhesive patch with a translucent tape permitted uninterrupted and prolonged occlusion, with a successful visual outcome. The amblyopic eye achieved a significantly better final vision (20/30+2; groups 1+2) than the controls (20/40+1; group 3) (p = 0.04). Sixty-four (76.19%) patients achieved >or=20/30. CONCLUSIONS: The translucent tape optimizes compliance and yields better vision by lengthening the duration of occlusion therapy and reducing the number of treatment failures due to noncompliance.

Acquired restrictive strabismus and high axial myopia: diagnosis and management.

OBJECTIVE: This paper documents the clinical, ultrasound, magnetic resonance imaging (MRI), and anatomic characteristics of 6 patients with esohypotropia and high axial myopia. The results of strabismus surgery performed on these patients are evaluated. STUDY DESIGN: Retrospective cohort study. PARTICIPANTS: Six patients with esohypotropia and high axial myopia were selected from the practice of the second author (Michael Flanders). METHODS: We extracted the history and data from the preoperative and postoperative ophthalmic and orthoptic examinations, recorded the surgical procedures, and tabulated the postoperative results. A- and B-scans, orbital MRI images, and photo documentation were obtained for all patients. Supramaximal recession and resection on the horizontal rectus muscles, using adjustable sutures, was performed in all patients. A surgical outcome was deemed successful if, in primary position, postoperative horizontal ocular alignment measured 15 prism diopters (PD) or less and (or) if diplopia was eliminated. RESULTS: Echographic and MRI findings demonstrated an enlarged globe in all cases. Globe flattening on the orbital walls was found in 5 cases. Lateral rectus depression was visualized on MRI images in 4 cases. Surgical success was obtained in all patients. The average preoperative primary position esotropia measured 60 PD (25 to 90 PD) and the esodeviation after surgery was 7.0 PD (0 to 15 PD). Ductions were also improved. CONCLUSIONS: Different surgical approaches to realignment of eyes with high myopia and esohypotropia have been attempted. In this study, supramaximal amounts of recession and resection on the rectus muscles provided satisfactory results.

Prevalence and severity of hypertensive retinopathy in children.

The National High Blood Pressure Education Program (NHBPEP) report recommends a retinal exam seeking evidence of target organ damage in hypertensive children. This study aimed to determine the prevalence and severity of hypertensive retinopathy among hypertensive children, evaluated by pediatric ophthalmologists in the "real world" clinical setting using direct ophthalmoscopy. The authors retrospectively reviewed the medical records of the 83 children diagnosed with hypertension by a pediatric nephrologist between 1999 and 2006. Of the 35 children examined by an ophthalmologist within 12 months of the diagnosis of hypertension, only 3 (8.6%; 95% CI, 1.8%-23.1%) were diagnosed with hypertensive retinopathy. Despite the fact that those selected for retinal examination were likely at higher risk for retinopathy, the prevalence of retinopathy was low, and only mild abnormalities were detected. Given the lack of evidence linking mild retinal abnormalities with adverse outcomes, the NHBPEP recommendation for retinal examinations in hypertensive children should be reconsidered.

Resolution of periodic alternating nystagmus after decompression for Chiari malformation.

CASE REPORT: A 20-year-old female presented with horizontal jerk nystagmus, blurred vision, severe headaches, unsteady gait, and paresthesia. Magnetic resonance imaging revealed Chiari malformation I. Symptoms resolved after decompression of the posterior cranial fossa and removal of the right cerebellar tonsil. COMMENTS: Conditions associated with acquired periodic alternating nystagmus and ocular disorders associated with Chiari malformation are discussed. To our knowledge, this case is the first to report the resolution of periodic alternating nystagmus after neurosurgical decompression.

The photopic ERG luminance-response function (photopic hill): method of analysis and clinical application.

With progressively brighter stimuli, the amplitude of the photopic b-wave first increases, briefly saturates and then decreases gradually to reach a plateau, where the amplitude of the b-wave equals that of the a-wave; a phenomenon previously presented as the photopic hill. The unique presentation of this luminance-response function seriously complicates its analysis with curve fitting equations such as that of Naka-Rushton used for scotopic electroretinogram. We report a method of analysis of the photopic hill based on easily identifiable and reproducible features of the ascending and descending limbs of this function. The clinical usefulness of these parameters is illustrated with selected cases of retinal disorders.

Ophthalmic complications of slit-ventricle syndrome in children.

OBJECTIVE: To present the ophthalmic features and visual prognosis of patients with slit-ventricle syndrome (SVS). DESIGN: Observational case series. PARTICIPANTS: Six patients diagnosed and treated with SVS at the Montreal Children's Hospital between 1985 and 1999. METHODS: Patients were included in this study if they had an appropriate ophthalmologic follow-up and if they fulfilled the criteria for the diagnosis of SVS based on intracranial pressure monitoring and neuroimaging studies. MAIN OUTCOME MEASURES: Features studied included patients' baseline ophthalmologic evaluation, visual outcome, and neurosurgical characteristics. RESULTS: The follow-up ranged from 1 to 14 years. The average number of shunting procedures was 3.7. Ocular examination performed on the initial visit revealed a normal visual acuity in four patients, esotropia in three of six patients, and nystagmus in two of six patients. Cycloplegic refraction was normal in all the subjects. Initial funduscopic evaluation revealed optic atrophy in a 4-month-old infant, whereas two children developed optic atrophy later in the course of the disease. One child developed severe visual field defects. The two children with optic atrophy had moderate to severe loss of visual acuity associated with SVS. CONCLUSIONS: A prompt recognition of patients with SVS is crucial, because these individuals are at an increased risk for significant visual loss.