An educational intervention to improve adherence to high-dosage patching regimen for amblyopia: a randomised controlled trial.

BACKGROUND: Previous reports suggest that adherence to patching is a major issue in amblyopia treatment. We tested with an unmasked randomised controlled clinical trial whether an intense educational/motivational intervention improves adherence when a high-dose regime is prescribed. METHODS: 62 children with newly diagnosed amblyopia were randomly allocated into two treatment arms with and without educational/motivational intervention material. Both were prescribed patching 10 h/day, 6 days/week for a fixed period of 12 weeks. The intervention arm received an educational/motivational intervention before patching which included information booklets, video, a cartoon story book, sticker charts and a dedicated session with a researcher. The control arm received the usual clinical information. The primary outcome measure was adherence measured using electronic occlusion dose monitors where a success/failure binary outcome was used to account for participants who dropped out of the study defined as patching >4 h/day. Visual outcome, expressed as percentage visual deficit, was measured as secondary outcome. RESULTS: The intervention increased adherence success rate from 45.2% in the control group to 80.6% in the intervention group (p=0.0027). However, visual outcome was not significantly better in the intervention group (p=0.190). CONCLUSIONS: Our study shows that an intense educational/motivational intervention can improve adherence to patching to high prescribed doses although no significant improvement in visual outcome was observed. TRIALS REGISTRATION NUMBER: ISRCTN05346737 (International Standard Randomised Controlled Trial Number Register).

What we know about the generation of nystagmus and other ocular oscillations: are we closer to identifying therapeutic targets?

Mechanisms underlying acquired nystagmus are better understood than those leading to infantile nystagmus. Accordingly, further progress has been made in the development of effective therapies for acquired nystagmus, mainly through pharmacological interventions. Some of these therapies have been developed under the guidance of findings from experimental animal models. Although mechanisms behind infantile nystagmus are less understood, progress has been made in determining the genetic basis of nystagmus and characterizing associated sensory deficits. Pharmacological, surgical, and other treatments options for infantile nystagmus are now emerging. Further investigations are required for all forms of nystagmus to produce high-quality evidence, such as randomized controlled trials, upon which clinicians can make appropriate treatment decisions.

The functional significance of foveal abnormalities in albinism measured using spectral-domain optical coherence tomography.

PURPOSE: The relationship between foveal abnormalities in albinism and best-corrected visual acuity (BCVA) is unclear. High-resolution spectral-domain optical coherence tomography (SD OCT) was used to quantify foveal retinal layer thicknesses and to assess the functional significance of foveal morphologic features in patients with albinism. DESIGN: Cross-sectional study. PARTICIPANTS: Forty-seven patients with albinism and 20 healthy control volunteers were recruited to the study. METHODS: Using high-resolution SD OCT, 7×7×2-mm volumetric scans of the fovea were acquired (3-µm axial resolution). The B scan nearest the center of the fovea was identified using signs of foveal development. The thickness of each retinal layer at the fovea and foveal pit depth were quantified manually using ImageJ software and were compared with BCVA. MAIN OUTCOME MEASURES: Total retinal thickness, foveal pit depth, photoreceptor layer thickness, and processing layer thickness in relation to BCVA. RESULTS: Total photoreceptor layer thickness at the fovea was correlated highly to BCVA (P = 0.0008; r = -0.501). Of the photoreceptor layers, the outer segment length was correlated most strongly to BCVA (P<0.0001; r = -0.641). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (P>0.05). This was because of an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (P<0.0001; r = -0.696). CONCLUSIONS: Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit, because patients with similar overall retinal thickness had widely varying foveal morphologic features. In albinism, the size of the photoreceptor outer segment was found to be the strongest predictor of BCVA. These results suggest that detailed SD OCT images of photoreceptor anatomic features provide a useful tool in assessing the visual potential in patients with albinism. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Physiology and pathology of eye-head coordination.

Human head movement control can be considered as part of the oculomotor system since the control of gaze involves coordination of the eyes and head. Humans show a remarkable degree of flexibility in eye-head coordination strategies, nonetheless an individual will often demonstrate stereotypical patterns of eye-head behaviour for a given visual task. This review examines eye-head coordination in laboratory-based visual tasks, such as saccadic gaze shifts and combined eye-head pursuit, and in common tasks in daily life, such as reading. The effect of the aging process on eye-head coordination is then reviewed from infancy through to senescence. Consideration is also given to how pathology can affect eye-head coordination from the lowest through to the highest levels of oculomotor control, comparing conditions as diverse as eye movement restrictions and schizophrenia. Given the adaptability of the eye-head system we postulate that this flexible system is under the control of the frontal cortical regions, which assist in planning, coordinating and executing behaviour. We provide evidence for this based on changes in eye-head coordination dependant on the context and expectation of presented visual stimuli, as well as from changes in eye-head coordination caused by frontal lobe dysfunction.

Filling-in along horizontal and vertical meridians.

PURPOSE: Filling-in is not homogeneous across the visual field; rather, fading time (FT) varies with eccentricity and polar angle. The reasons for this are unclear. The authors investigated FT along horizontal and vertical meridians in central and peripheral visual fields for luminance-defined targets, comparing Weber contrast sensitivity (CSw). They also compared cone-mediated and rod-mediated filling-in with previously described photoreceptor densities. This represents the first investigation into rod-mediated filling-in. METHODS: Fading times were recorded in nine volunteers using luminance-defined stimuli at eccentricities of 0 degrees , 2.5 degrees , 5 degrees , 10 degrees , and 20 degrees for high-contrast stimuli and 0 degrees , 1.25 degrees , 2.5 degrees , 3.75 degrees , and 5 degrees for low-contrast stimuli and were compared with CSw at each location. Fading times were also recorded at 0 degrees , 2.5 degrees , 5 degrees , 10 degrees , and 20 degrees using red-green stimuli and at 5 degrees , 10 degrees , and 20 degrees under dark-adapted conditions and compared with cone and rod densities in the nasal, temporal, superior, and inferior hemimeridians. RESULTS: Consistent anisotropy was evident in central and peripheral fields for luminance-defined targets and for chromatic targets, with horizontal meridians taking longer to fill in. The same pattern was observed in CSw and the previously described cone density. Log FT and CSw were correlated irrespective of visual field location. The ratio of rod-mediated FT to rod density decreased with eccentricity. CONCLUSIONS: Anisotropy between horizontal and vertical meridians for FT is consistent in central and peripheral fields, reflecting patterns in CSw and cone density. This is discussed in the context of cortical processes underlying filling-in. For rod-mediated filling-in, more peripheral eccentricities are characterized by reduced FTs in relation to rod density.

Coordination of eye and head movements during reading.

PURPOSE: There is little information regarding the characteristics of head movements during reading. This study was undertaken to investigate horizontal and vertical head movements during two different reading tasks. METHODS: Head and eye movements were monitored with an infrared pupil and head tracker in 15 subjects during repeated reading of text from an A4-sized card and a card 90 degrees wide. In addition, head and eye movements were recorded in 45 subjects to compare head movement propensity during an A4 text-reading task and a saccadic task of an equivalent gaze shift. RESULTS: During the A4 standard reading task, horizontal and vertical head movements accounted for 4.7% and 28.7% of the gaze shift, respectively. During the 90 degrees text reading, horizontal head movements accounted for 40.3% of the gaze amplitude, and vertical head movements accounted for 28.4%. Horizontal gaze velocities increased significantly on repeated A4 and 90 degrees text readings, as did horizontal head velocities and amplitudes. Reading head movement propensities were significantly smaller than saccadic head movement propensities (P < 0.001). CONCLUSIONS: Head movement strategies are rapidly switched between the A4 and 90 degrees text-reading paradigms. They are minimized during A4 text reading but actively assist the gaze strategy during 90 degrees text reading. Horizontal head movement is reduced during A4 reading compared to the equivalent saccadic task and may be suppressed to improve fixation stability. The results support the view that the head and eye movement system is a highly coupled but extremely flexible system.