Nystagmus Characteristics in Albinism: Unveiling the Link to Foveal Hypoplasia and Visual Acuity

Purpose

The purpose of this study was to describe the association among nystagmus characteristics, foveal hypoplasia, and visual acuity in patients with albinism.

Methods

We studied nystagmus recordings of 50 patients with albinism. The nystagmus waveform was decomposed into two types: dominantly pendular and dominantly jerk. We correlated the nystagmus type, amplitude, frequency, and percentage of low velocity (PLOV) to Snellen visual acuity and foveal hypoplasia grades.

Results

The grade of foveal hypoplasia and visual acuity showed a strong correlation (r = 0.87, P < 0.0001). Nystagmus type and PLOV had the strongest significant (P < 0.0001) correlation with visual acuity (r = 0.70 and r = -0.56, respectively) and with foveal hypoplasia (r = 0.76 and r = -0.60, respectively). Patients with pendular nystagmus type had the lowest PLOV, and the highest grade of foveal hypoplasia (P < 0.0001). Severe foveal hypoplasia (grade 4), was almost invariably associated with pendular nystagmus (86%).

Conclusions

Foveal hypoplasia grade 4 is associated with pendular nystagmus, lower PLOV, and worse visual acuity. Based on these results, nystagmus recordings at a young age may contribute to predicting visual outcomes.

The Phenotypic and Mutational Spectrum of the FHONDA Syndrome and Oculocutaneous Albinism: Similarities and Differences

Purpose

The purpose of this study was to further expand the mutational spectrum of the Foveal Hypoplasia, Optic Nerve Decussation defect, and Anterior segment abnormalities (FHONDA syndrome), to describe the phenotypic spectrum, and to compare it to albinism.

Subjects and Methods

We retrospectively collected molecular, ophthalmic, and electrophysiological data of 28 patients molecularly confirmed with FHONDA from the Netherlands (9), Israel (13), France (2), and the United States of America (4). We compared the data to that of 133 Dutch patients with the 3 most common types of albinism in the Netherlands: oculocutaneous albinism type 1 (49), type 2 (41), and ocular albinism (43).

Results

Patients with FHONDA had a total of 15 different mutations in SLC38A8, of which 6 were novel. Excluding missing data, all patients had moderate to severe visual impairment (median visual acuity [VA] = 0.7 logMAR, interquartile range [IQR] = 0.6-0.8), nystagmus (28/28), and grade 4 foveal hypoplasia (17/17). Misrouting was present in all nine tested patients. None of the patients had any signs of hypopigmentation of skin and hair. VA in albinism was better (median = 0.5 logMAR, IQR = 0.3-0.7, P 0.006) and the phenotypes were more variable: 14 of 132 without nystagmus, foveal hypoplasia grades 1 to 4, and misrouting absent in 16 of 74.

Conclusions

Compared to albinism, the FHONDA syndrome appears to have a more narrow phenotypic spectrum, consisting of nonprogressive moderately to severely reduced VA, nystagmus, severe foveal hypoplasia, and misrouting. The co-occurrence of nystagmus, foveal hypoplasia, and misrouting in the absence of hypopigmentation implies that these abnormalities are not caused by lack of melanin, which has important implications for understanding the pathogenesis of these features.

Electroretinogram abnormalities in non-infectious uveitis often persist

PURPOSE

In uveitis, a prolonged implicit time of the cone b-wave is a characteristic electroretinogram (ERG) abnormality. We investigated whether this can improve or deteriorate over time and which clinical factors are associated with change.

METHODS

Prospective cohort study. Patients with a non-infectious uveitis were included. An ERG was measured in the first year of uveitis onset and a follow-up ERG one year later. Changes in the implicit time of the cone b-wave were investigated in relation to clinical parameters including the following: demographics, uveitis characteristics, treatment, best-corrected visual acuity, optical coherence tomography parameters and fluorescein angiography scores.

RESULTS

Of 98 eyes (63 patients), 40 showed a prolonged cone b-wave on the first ERG, which improved in 10 eyes. Eyes with an improved ERG more often had a panuveitis with initially a higher incidence of cells in the anterior chamber during the first ERG, which resolved at the time of their follow-up ERG. Five of the 58 eyes with a normal first ERG had a deteriorated follow-up ERG. These eyes had more frequently an active uveitis at the time of the follow-up ERG. Of the 78 eyes with a stable cone b-wave, 16 had a quiescent inflammation during follow-up. There were no differences in age or treatment.

CONCLUSION

In most patients with non-infectious uveitis, ERG abnormalities appear to be irreversible, even when the inflammation becomes quiescent. However, some ERGs improved, which was associated with reduction in inflammation of the anterior chamber due to panuveitis. In contrast, a worsened ERG was associated with a persistence of inflammation.

Effects of DTL electrode position on the amplitude and implicit time of the electroretinogram

PURPOSE

This study sought to investigate whether there is an optimal position of the Dawson, Trick, and Litzkow (DTL) electrodes when measuring the full-field electroretinogram (ERG) for monitoring purposes.

METHODS

In 200 uveitis patients, an extended light-adapted (LA) ERG protocol was measured twice, incorporating the International Society for Clinical Electrophysiology of Vision standards. First, a LA ERG was measured with the DTL in the lower lid position (LLP) and thereafter in the fornix position. Differences in amplitudes and implicit times of a-waves, b-waves, and the 30 Hz peak were investigated. Intraclass correlation coefficients (ICCs) as well as coefficients of variation (CoV) were calculated, to assess both reliability and relative variability between the two DTL positions.

RESULTS

Implicit times showed no statistically significant differences between the two DTL positions. As expected, amplitudes at the different stimulus strengths were 1.12-1.19 higher in the LLP, but there were no significant differences in the CoV between the two DTL positions. The ICC was high for the b-wave and 30 Hz flicker response (0.842-0.979), but lower for the a-wave, especially for amplitudes (0.584-0.716).

CONCLUSIONS

For monitoring purposes in patients, we conclude that based on relative variability, no position is preferable above the other. However, because in most diseases amplitudes are decreased, the LLP may be chosen because it yields higher amplitudes. Whatever the choice, it is important to ensure that the DTL position remains stable during an ERG recording.

Prolonged Cone b-Wave on Electroretinography Is Associated with Severity of Inflammation in Noninfectious Uveitis

PURPOSE

This study sought to investigate retinal function in patients with noninfectious uveitis by using full-field electroretinography (ERG) and correlate the ERG to disease duration and severity of inflammation.

DESIGN

Prospective cohort study.

METHODS

Patients (n = 200) with noninfectious uveitis and a disease duration of <1 year (group A [n = 80]) and those with a disease duration of >5 years (group B [n = 120]) were included. ERGs of the total 355 uveitis eyes were measured according to an extended International Society for Clinical Electrophysiology of Vision protocol. ERG abnormalities were related to demographics and uveitis characteristics, including anatomical classification, duration of uveitis, severity of inflammation, best corrected visual acuity (BCVA), cystoid macular edema (CME), and the highest fluorescein angiography (FA) score during the course of the disease.

RESULTS

ERGs showed abnormalities in 235 eyes (66.2%). The most frequent and pronounced ERG abnormality was a prolonged implicit time of the cone b-wave (151 eyes [42.5%]), which was associated with vitritis (P = .005); cells in the anterior chamber (P = .007); the highest fluorescein angiography score (P = .011); age (P < 0.001); and pupil diameter (P < 0.001). BCVA was relatively good (0.05 logMAR [interquartile range {IQR}, 0.011, 0.22]) and not associated with this ERG abnormality. There were no differences between the ERG abnormalities in group A and those in group B and no significant associations between ERG abnormalities and anatomical classification or specific diagnoses.

CONCLUSIONS

ERG results are frequently affected in cases of noninfectious uveitis of all anatomic subtypes, including anterior uveitis without apparent inflammation of the posterior segment. ERG abnormalities appear to be associated with the severity of inflammation from both the present and the past and therefore may be seen even when signs of retinal inflammation have disappeared.

CVI Experience toolbox: Simulation of visual processing difficulties

We designed a cerebral visual impairment (CVI)–experience toolbox containing simulation exercises to let professionals experience the complexity of visual information processing and to get an impression of what it means to have CVI. We measured the benefits of the CVI Experience toolbox by using questionnaires during three CVI seminars with professionals ( n = 69). These seminars started with a slide presentation on CVI followed by the CVI experience toolbox. We presented the professionals with the same survey on their knowledge of CVI at the start of the seminar, after the presentation, and after the toolbox.

Professionals with more previous CVI experience started on average with a higher score. The final end score, however, did not seem to depend on previous experience. Furthermore, the added value of the experience toolset was quite independent of the added value of the presentation.

The results indicate that both the presentationand the experience toolboxadd to the understanding of CVI.

Quantification of visual function assessment using remote eye tracking in children: validity and applicability

PURPOSE

Measurements of visual and oculomotor functions are essential for providing tailored support to visually impaired children. In young or intellectually disabled children these measurements can be difficult or even impossible to perform. Recordings of orienting gaze in response to specific visual information, made with eye tracking, may offer a solution. The aim of this study was to observe and quantify eye tracking (ET)-based gaze responses to provide information about visual and oculomotor functioning, and to compare this information with standard visual function assessments (VFA).

METHODS

One hundred and twenty-six visually impaired children from 1-14 years underwent a VFA. Next they underwent a remote ET test. Four aspects of oculomotor control (nystagmus, fixation, saccades, pursuit) and three visual functions (visual field, contrast, colour) were selected to compare both methods. Performance was assessed (1) during VFA using standard behavioural observation and test scores and (2) after ET by observing and scoring the eye movement recordings. Validity, in terms of agreement between results, was measured by correlation analyses. From the orienting gaze responses, quantitative parameters (gain, fixation duration and directional saccades) were calculated to characterize visual performance.

RESULTS

Good agreement between the two test methods was found for observational assessment of oculomotor control and visual functions (correlations ranging from rs  = 0.39 to rs  = 0.69). The quantitative parameters of visual performance showed distinct results between children with and without specific functional impairments, both in children aged 1-6 and 7-14 years.

CONCLUSION

Eye tracking-based gaze recordings are a promising tool to assess oculomotor and visual performance in a communication-free manner. Calculating quantitative parameters from specific gaze responses could assist in the characterization of functional visual performance in children, independent of age. Gaze responses are a useful addition to standard VFA in clinical practice.

The effect of zirconia and titanium implant abutments on light reflection of the supporting soft tissues

OBJECTIVES

To determine the difference in light reflection of oral mucosa covering titanium (Ti) or zirconia (ZrO(2)) abutments as it relates to the thickness of the covering mucosa.

MATERIAL AND METHODS

Fifteen anterior implants (Astra Osseo speed(®)) in 11 patients were fitted with a Ti or a ZrO(2) abutment (cross-over, within-subject comparison). Hyper-spectral images were taken with a camera fitted on a surgical microscope. High-resolution images with 70 nm interval between 440 and 720 nm were obtained within 30 s (1392 × 1024 pixels). Black- and white-point reference was used for spatial and spectral normalization as well as correction for motion during exposure. Reflection spectra were extracted from the image on a line mid-buccal of the implant, starting 1 mm above the soft tissue continuing up to 3 mm apically.

RESULTS

Median soft tissue height is 2.3 mm (min: 1.2 mm and max: 3.1 mm). The buccal mucosa rapidly increases in the thickness, when moving apically. At 2.2 mm, thickness is 3 mm. No perceivable difference between the Ti and ZrO(2) abutment can be observed when the thickness of the mucosa is 2±0.1 mm (95% confidence interval) or more.

CONCLUSION

It is expected that the difference in light reflection of soft tissue covering Ti or ZrO(2) abutments is no longer noticeable for the human eye when the mucosa thickness exceeds 2 mm. Haemoglobin peaks in the reflection spectrum can be observed and make hyper-spectral imaging a practical and useful tool for measuring soft tissue health.

Simulating the straylight effects of cataracts

PURPOSE

To study the additional straylight falling on the retina (retinal straylight) caused by cataract and find commercially available filters to simulate the cataract straylight effects.

SETTING

Research laboratory.

METHODS

The retinal straylight addition of cataract was derived from straylight parameter data in the literature. The scattering characteristics of cataract-simulating filters were measured using a scatterometer.

RESULTS

The straylight addition due to cataract follows a power law as a function of angle with power of -2.12 and straylight parameter log values of up to 1.6 for relatively mild cataract cases. Of the commercial filters that were tested, the Tiffen Black Pro Mist (BPM) filters resembled the straylight characteristics of cataracts fairly well. The filters had a limited effect on visual acuity and contrast sensitivity, which was also found for early cataracts. The BPM 2 followed a power law as a function of angle with power of approximately -2.21 and straylight log values of 1.12.

CONCLUSIONS

The BPM 2 filter is a good early-cataract-simulating filter. Stacking such filters is a good way to increase the cataract density. A drawback is that the BPM 2 filter has a transmission of 66% so stacking filters reduces the overall transmission significantly.

Field-Dependent Aniseikonia Associated with an Epiretinal Membrane

PURPOSE

Aniseikonia is a binocular anomaly in which the two eyes perceive images of different sizes and/or shapes. It is usually assumed to be constant as a function of visual field angle (VFA) (i.e., angular distance from the line of sight). This is correct for optically induced aniseikonia, such as the aniseikonia that is associated with anisometropia and probably also pseudophakia. The purpose of this article is to show that if the aniseikonia is of retinal origin, then the aniseikonia may no longer be constant as a function of VFA (i.e., field-dependent aniseikonia).

DESIGN

Case report, with the patient having a unilateral epiretinal membrane.

METHODS

The aniseikonia was measured in vertical and horizontal directions with a customized version of the Aniseikonia Inspector software. The VFA was made variable by changing the dimensions of the comparison targets in the direct comparison procedure.

MAIN OUTCOME MEASURE

Aniseikonia as a function of VFA.

RESULTS

The patient exhibited good repeatable aniseikonia, ranging from 23% to 2.5% for VFAs ranging from 0.36 degrees to 5.7 degrees . Higher angles had lower aniseikonia. A control subject did not show this field-dependent aniseikonia.

CONCLUSIONS

Aniseikonia may vary with VFA due to a retinal cause such as an epiretinal membrane. The problem with field-dependent aniseikonia is that it cannot be corrected fully with conventional optics, which exhibit an approximately constant magnification as a function of VFA. Nevertheless, by correcting 5% to 10% aniseikonia, which showed up in the VFA measurement range at 2 degrees to 3 degrees , our patient had improved visual comfort, especially for reading.

Evaluation of a new direct-comparison aniseikonia test

BACKGROUND AND PURPOSE

Aniseikonia is a condition in which the two eyes perceive images of different size or shape, causing a variety of visual symptoms including asthenopia. Besides anisometropes (with a prevalence of 5-10% in the population above age 20 years), also pseudophakes and refractive surgery patients are at risk. For example, 40% of the pseudophakes seem to suffer from aniseikonia. Reliable measurement and management of aniseikonia is therefore important. The "Aniseikonia Inspector" is a new, commercially available, software product to measure and manage aniseikonia. The purpose of this study is to evaluate this aniseikonia test of the Aniseikonia Inspector.

METHODS

Aniseikonia was induced in four subjects, with normal vision, by means of afocal size lenses. Using the Aniseikonia Inspector, the resulting aniseikonia was measured in vertical, horizontal and diagonal directions.

RESULTS

The average ratio between the measured aniseikonia and the induced aniseikonia was 0.98, 0.89 and 0.93 respectively for the vertical, horizontal and diagonal directions. For two consecutive measurements of the same aniseikonic state, the difference in measurement value was 97%, 75% and 94% of the time within one resolution step size (0.5% horizontally and vertically, and 0.7% diagonally).

CONCLUSION

Aniseikonia was measured accurately. Measurements in the vertical direction were more accurate than in the diagonal or horizontal directions, which is probably due to fixation disparities. The Aniseikonia Inspector is a very useful new tool in treating the growing number of aniseikonia patients.