Evidence for Alteration in Photoreceptor Orientation

The effect of incident light, its point of origin, and its magnitude on receptor orientation was determined. A non-invasive test of vision, the Stiles-Crawford Effect (SCE), was used to investigate retinal directional sensitivity and alignment. The simple act of monocular black patching for a period of three to five days caused marked reduction in directional sensitivity and/or apparent dispersal of alignments. Recovery occurred in a comparable time period in normal adults 20 to 50 years of age. Special painted iris contact lenses with displaced pupillary apertures were worn to investigate the factors influencing alignment. Both light induced effects which caused alignment to shift toward a displaced aperture, and mechanical factors resulting in other alignment shifts were recorded. Thus, retinal receptors and/or associated anatomic components are apparently phototropic and subject to multiple forces influencing their directionality and/or alignment, and the milieu of the retinal receptor is active.     

Effect of oral CDP-choline on visual function in young amblyopic patients

Purpose The purpose of the study was to evaluate the effect on visual function of orally administered CDP-choline in addition to patching for the treatment of amblyopia in children. Methods This was an open label parallel group study comparing patching plus oral CDP-choline with patching alone. Sixty-one participants (aged between 5 and 10 years) suffering from anisometropic or strabismic amblyopia were divided at random into two groups: Group A, 800 or 1,200 mg (according to the body weight) of orally administered CDP-choline and 2-h patching a day; Group B, 2-h patching a day. Both groups were treated for 30 consecutive days. A follow-up visit was set 60 days after the treatment was discontinued. The main outcome measure was the change in visual acuity of amblyopic eyes as measured by Snellen’s E charts. The secondary outcome measures were changes in the visual acuity of amblyopic eye as measured by isolated letters (Snellen’s E) and changes in the contrast sensitivity of amblyopic eyes. Results The addition of CDP-choline to patching therapy was not found to be more effective than patching alone after 30-day treatment. The present results showed that adding CDP-choline to patching stabilised the effects obtained during the treatment period. In fact, whereas the participants treated only with patching showed a decrease in visual acuity at 90 days, these receiving CDP-choline and patching combined appeared to maintain the results obtained (two-way ANOVA: P = 0.0042). Similar results were obtained when measuring visual acuity by isolated Snellen’s E letters. Conclusions In amblyopic patients, CDP-choline combined with patching contributes to obtaining more stable effects than patching alone. Fabio De Gregorio works as an advisor for Tubilux Pharma S.p.A. The authors have full control of all primary data and they agree to allow Graefe’s Archives for Clinical and Experimental Ophthalmology to review their data if requested.     

Vision in the "good" eye of children treated for unilateral congenital cataract.

PURPOSE: The authors examined linear acuity and contrast sensitivity in the "good" (fellow) eye of children treated for unilateral congenital cataract to determine (1) whether there were subtle deficits like those described for the good eye of patients with strabismic amblyopia and (2) whether any deficits were related to the degree to which the good eye had been patched. METHODS: The authors tested patients treated for unilateral congenital cataract who had a well-documented history of patching. The good eye was physically normal with minimal refractive error. The measures were linear acuity at far (n = 15) and contrast sensitivity (n = 9). RESULTS: Compared with age-matched control subjects, the good eyes of patients had subtle deficits in linear acuity and in contrast sensitivity at high spatial frequencies. These deficits occurred even in eyes that had received minimal patching, and their severity was not related systematically to the duration of patching, which varied widely across the group. CONCLUSION: The visual sensitivity of the good eye of children treated for unilateral congenital cataract is, on average, slightly reduced, even in cases of minimal patching. Consequently, any deficits discovered after aggressive patching may not have been caused by occlusion amblyopia.     

Up- and downshoot in adduction after monocular patching in normal volunteers

Upshoot-in-adduction and downshoot-in-adduction are non-paretic motility disorders that usually accompany a horizontal squint in children, together with V- or A-pattern motility. Upshoot-in-adduction may sometime mimic a superior oblique palsy. The authors have found that even in healthy volunteers these motility disorders can be found and made manifest by patching. One eye of complaint-free volunteers with full stereopsis was patched for three days. Then the eye movements of the patched eye were recorded with the search coil technique, first before taking the patch off and secondly after putting the patch on the other eye. The latter registration served as reference for the first registration. It was found that 11 out of 18 volunteers had developed an upshoot-in-adduction of the patched eye. In five cases no directional change was found whereas two cases had developed a downshoot-in-adduction. It seems that up- and downshoot-in-adduction are latent motility disorders that become manifest after disruption of fusion. In addition, the authors found undershooting saccades and postsaccadic drift of the patched eyes.     

Two‐year follow‐up of a randomized trial of spectacles plus alternate‐day patching to treat strabismic amblyopia

Purpose: To compare spectacles plus alternate‐day patching for 8 hr or more with spectacles plus patching for 8 hr or more 6 days weekly to treat strabismic amblyopia 1 year after a 1‐year randomized trial. Methods: Forty children (mean age, 4.3 years) participated. Refractive correction was provided. The children were assigned to alternate‐day patching for 8 hr or more or patching for 8 hr or more daily 6 days weekly. VA, binocular function, and refractive errors were measured after 2 years. The main outcome measure was the median VA change in the amblyopic eye after 2 years. Results: The median VA change in the amblyopic eye at the 2‐year visit was significantly (p = 0.0453) greater with alternate‐day patching (0.8 log unit) versus patching daily 6 days weekly (0.6 log unit). The final median VA in the amblyopic eyes was 0.0 logMAR in the alternate‐day patching group and 0.1 logMAR in the daily patching group. Binocular function improved with both treatments. The median spherical equivalent (SE) refractive error increased in the fellow eyes (alternate‐day patching, p < 0.0001; patching daily 6 days weekly, p = 0.0033); no change was found in the amblyopic eyes in either group. Conclusions: The magnitude of the VA change 2 years after treatment with spectacles plus alternate‐day patching for 8 hr or more was significantly greater than with spectacles plus daily patching for 8 hr or more 6 days weekly for strabismic amblyopia. However, the final median VA did not differ significantly between the two treatments.     

Exercise alone impacts short-term adult visual neuroplasticity in a monocular deprivation paradigm

Adult homeostatic visual plasticity can be induced by short-term patching, heralded by a shift in ocular dominance in favor of the deprived eye after monocular occlusion. The potential to boost visual neuroplasticity with environmental enrichment such as exercise has also been explored; however, the results are inconsistent, with some studies finding no additive effect of exercise. Studies to date have only considered the effect of patching alone or in combination with exercise. Whether exercise alone affects typical outcome measures of experimental estimates of short-term visual neuroplasticity is unknown. We therefore measured binocular rivalry in 20 healthy young adults (20–34 years old) at baseline and after three 2-hour interventions: patching (of the dominant eye) only, patching with exercise, and exercise only. Consistent with previous work, the patching interventions produced a shift in ocular dominance toward the deprived (dominant) eye. Mild- to moderate-intensity exercise in the absence of patching had several effects on binocular rivalry metrics, including a reduction in the dominant eye percept. The proportion of mixed percept and the time to first switch (onset rivalry) did not change from baseline across all interventions. Thus, we demonstrate that exercise alone can impact binocular rivalry outcomes measures. We did not observe a synergistic effect between patching and exercise in our data.     

Effect of monocular light exclusion on the Stiles-Crawford function

Contrary to previously published studies, monocular light exclusion did not alter the shape of the Stiles-Crawford function in a substantial manner in four subjects who were patched in this laboratory for one full week. In order to rule out methodological differences, an experimenter from each of the two sets of experiments (current and prior) patched one eye for 1 week, then tested each other. For one subject, there was little effect of patching. For the other, patching had a measurable effect, but it was different from that originally reported. However, the much larger, symmetrical broadening of the Stiles-Crawford function reported in earlier studies was not replicated. A testable working hypothesis to explain the earlier results is discussed.     

Hypotony and corneal edema secondary to patching in normal eyes.

Over the past decade investigators have used patching when studying corneal response to eye lid closure. In these studies, corneal edema was thought to be secondary to hypoxia, and the results were used to predict corneal response to contact lens wear. None of these studies have measured or controlled the intraocular pressure (IOP) during eye patching. Reports in the literature indicate that hypotonous and hypertensive events may induce corneal edema. In order to evaluate the IOP and corresponding corneal changes, measurements were made on subjects with patched eyes. Thirty subjects were unilaterally patched and randomized into tight and light patch groups to maintain complete lid closure for 4 h. Measurements of IOP and corneal thickness (CT) were made at baseline and at hourly intervals. The contralateral eye served as the control for each subject. Our results indicate a significant decrease in IOP and a corresponding increase in CT in the tight patched group as compared to the light patch group, and baseline controls. These results suggest that the corneal edema which results from patching of the eye may be due to hypotony, or a combination of factors affecting corneal function, rather than hypoxia.     

Visual results in children treated for macular retinoblastoma

PURPOSE: To evaluate the results of patching treatment in children with macular retinoblastoma in one eye. METHODS: Fifteen children affected by macular retinoblastoma received instructions for patching treatment for amblyopia. Data were collected on age at diagnosis of the tumor, presence of unilateral or bilateral disease, area of posterior pole involvement by the scar of the regressed tumor and its relationship to the fovea; and the onset, duration, and compliance of patching. The visual acuities recorded were expressed in logMAR (logarithm minimum angle of resolution) equivalents. RESULTS: Twelve children (80%) had bilateral retinoblastoma with the macular involved in one eye and three children had unilateral macular tumors. The median age at which patching was initiated was 15 months (range 4-36). Compliance to patching was good in 80% of children, with a median duration of 4 h (range 0.5-8) per day, 7 days per week, with total occlusion of the better eye. The median percentage of posterior pole involvement was 34% (range 11-100%). Eighty percent of children had some improvement in their visual acuity, and of the children in whom final logMAR acuity was recorded, 73% had an acuity of 1.0 logMAR or better and 53% an acuity of 0.5 logMAR or better after patching. There was no evidence of association between age of patient, sex, duration of patching, or percentage of posterior pole involvement and the improvement in visual acuity. CONCLUSIONS: In spite of the macular involvement of eyes with retinoblastoma, some visual recovery was achieved in 80% of children. Hence a trial of patching therapy is recommended for all children with involvement of the macula by retinoblastoma.     

Directionally selective light adaptation: A visual consequence of receptor disarray?

Brightness matches were established between test lights that entered the eye at diametrically opposite points within the pupil. In parafoveal observation, test lights entering near the temporal margin had to be more intense for temporal than for nasal entry of an adapting light. The appendix develops a quantitative theory of this effect, and derives from the results an estimate of the directional sensitivity of single cones and an estimate of the variation in tilt among the receptors in a small retinal region.     

Psychosocial and clinical determinants of compliance with occlusion therapy for amblyopic children

AIMS: The objective of this study was to determine the extent that psychosocial and clinical variables influence parental compliance with occlusion therapy (eye patching) in children with amblyopia. METHODS: Children (n = 151) receiving occlusion therapy (eye patching) for the treatment of amblyopia were recruited from five orthoptic clinics in Bristol, UK. Parents completed a questionnaire based on Rogers' (1983) Protection Motivation Theory (PMT). The parents (n = 105) were also followed up 2 months later. Clinical data, including measures of visual acuity, were also recorded. Compliance with eye patching was assessed through self-report accounts of parents. Stepwise regression analyses were used to determine the factors predictive of compliance with eye patching. RESULTS: Self-reported compliance with eye patching at study entry revealed that only 54% of parents were achieving orthoptists' recommendations to patch their child. Perceived self-efficacy was positively associated with compliance and perceived prohibition of the child's activities were negatively associated with compliance. At follow-up, past behaviour accounted for the largest proportion of explained variance in patching behaviour followed by response efficacy, and prohibition of the child's activities. CONCLUSION: The present findings may serve to inform interventions aimed at enhancing current orthoptic practice to improve compliance in amblyopic children. The importance of 'self-efficacy' and past behaviour suggests that consultations with parents exhibiting higher levels of success with patching may elicit strategies that could be shared with parents experiencing difficulties with patching their children. In addition, it is possible that the perceived efficacy of the treatment could be enhanced if orthoptists emphasised evidence of improvements in visual acuity which may, in turn, foster the maintenance of eye patching.     

The effect on refractive error of unilateral atropine as compared with patching for the treatment of amblyopia.

Our objective was to determine whether the use of unilateral atropine as amblyopia therapy leads to an asymmetric change in refractive error compared with patching. Patients were enrolled in a clinical trial in which atropine 1% solution or occlusion with an adhesive patch was administered daily to the sound eye of children 3 to less than 7 years of age for a period of at least 6 months to a maximum of 2 years. Refractive error at entry and at 2 years was determined with cycloplegic retinoscopy for 282 of 419 patients enrolled. The baseline mean refractive error was + 3.13 diopters (D) in patients assigned randomly to receive atropine and + 2.58 D in patients assigned randomly to wear the patch. The mean change in refractive error of the sound eye was + 0.10 D in the atropine group (N = 134) and + 0.08 D in the patch group (N = 148). Patients also were subdivided into those treated with atropine only (n = 41) and patching only (n = 64) because some children changed treatments during their study participation. The mean change for the sound eyes was -0.21 D for the patients receiving only atropine and -0.06 D for the patients receiving only patching. Unilateral atropine applied to the sound eye compared with occlusion was not associated with any adverse effect on refractive error following up to 2 years of treatment.     

Spatial-frequency-dependent changes in cortical activation before and after patching in amblyopic children

PURPOSE: To examine the cortical response under transient stimulus conditions in amblyopic children before and after eye patching. To determine whether improvement in acuity is associated with spatial-frequency-dependent changes in specific peaks of the cortical response. METHODS: Visual evoked potentials (VEPs) to check reversal (163-18 arc min) and onset of sine wave gratings (0.5-4 cyc/deg) were measured in 24 amblyopic children (<7 years of age) before eye patching. VEPs were repeated in nine subjects with 20/40 or better acuity after patching. Age, severity of amblyopia, and VEP amplitudes of positive peak (P)100, P1, and negative peak (N)2 were analyzed by multivariate statistics. RESULTS: Before patching, the amblyopic eye showed decreasing amplitude with increasing spatial frequencies (P < 0.05) when compared with the nonamblyopic eye. Reduced amplitudes occurred at frequencies well below acuity. Latencies were mildly prolonged. After patching, amplitudes increased in the amblyopic eye across all spatial frequencies (ANCOVA; P < 0.0001 for each peak). However, a spatial-frequency-dependent increase in amplitude was significant only for a late negative peak (N2). The patched eye showed no significant changes. CONCLUSIONS: Recovery of acuity after eye patching is associated with an overall increase in cortical activation across a wide range of spatial frequencies below the acuity threshold. A spatial-frequency-dependent increase in a late negative peak suggests that the cortical generator of this peak demonstrates plasticity of acuity recovery.     

A randomized trial of prescribed patching regimens for treatment of severe amblyopia in children

OBJECTIVE: To compare full-time patching (all hours or all but 1 hour per day) to 6 hours of patching per day, as prescribed treatments for severe amblyopia in children younger than 7 years. DESIGN: Prospective, randomized multicenter clinical trial (32 sites). PARTICIPANTS: One hundred seventy-five children younger than 7 years with amblyopia in the range of 20/100 to 20/400. INTERVENTION: Randomization either to full-time patching or to 6 hours of patching per day, each combined with at least 1 hour of near-visual activities during patching. MAIN OUTCOME MEASURE: Visual acuity in the amblyopic eye after 4 months. RESULTS: Visual acuity in the amblyopic eye improved a similar amount in both groups. The improvement in the amblyopic eye acuity from baseline to 4 months averaged 4.8 lines in the 6-hour group and 4.7 lines in the full-time group (P = 0.45). CONCLUSION: Six hours of prescribed daily patching produces an improvement in visual acuity that is of similar magnitude to the improvement produced by prescribed full-time patching in treating severe amblyopia in children 3 to less than 7 years of age.     

光学药物压抑疗法对儿童单眼弱视的疗效

目的对比分析光学药物压抑疗法与遮盖疗法对儿童斜视性或屈光参差性弱视的疗效。方法前瞻性临床研究。收集2013年1月至2015年3月在我院诊断为斜视性或屈光参差性弱视的儿童患者,根据采用的弱视治疗方法不同分为遮盖疗法组（遮盖组）与光学药物压抑疗法组（压抑组）。根据弱视程度不同又分为轻度、中度、重度弱视进行分析。对随访12个月以上患者的弱视治疗效果进行分析比较。2组弱视程度比较采用Wilcoxon秩和检验,组间的有效率和治愈率比较采用χ²检验。结果共纳入斜视性或屈光参差性弱视患者85例（85眼）,其中遮盖组52例（52眼）,压抑组33例（33眼）。遮盖组治愈率60%,压抑组治愈率64%,2组治愈率差异无统计学意义（χ²=0.137,P=0.711）。遮盖组有效率88%,压抑组有效率85%,2组有效率差异无统计学意义（χ²=0.234,P=0.629）。轻度、中度、重度弱视患者中,遮盖组与压抑组有效率差异均无统计学意义。遮盖组52只弱视眼均转为注视眼,压抑组进行药物压抑治疗3~6个月后,29只弱视眼转为注视眼,4只未转为注视眼,后改为遮盖疗法。结论与传统遮盖疗法相比,光学药物压抑疗法对于儿童斜视性或屈光参差性弱视的治疗效果相近。     

On the mechanisms of the interocular light adaptation effect

Lansford and Baker recently demonstrated that the adaptation state of the contralateral eye effects the sensitivity of the test eye during dark adaptation. Specifically, a smaller and dimmer contralateral preadapting field which partially overlaps the preadapting field seen by the test eye accelerates subsequent monocular dark adaptation. The present study replicated the interocular light adaptation (Lansford-Baker) effect and produced the same effect under different test conditions. By the use of limited wavelength contralateral preadapting fields it demonstrated the interocular light adaptation effect in both cone and rod segments of the dark adaptation curve and that the rod effect is larger. Both long and short wavelength contralateral preadapting fields enhanced the effect to the point of doubling its magnitude.     

The effect of chronic one-eye patching on ocular myoclonus.

Ocular myoclonus developed in our 34-year-old patient 4 months after massive brain stem hemorrhage due to eclampsia. On chronic patching of the left eye, the vertical pendular nystagmus in the fixating right eye disappeared, whereas the covered eye was esotropic. While fixating, the left eye showed horizontal pendular nystagmus. With both eyes fixating, the right eye presented markedly vertical pendular nystagmus and the left eye a horizontal pendular nystagmus. It seems that chronic patching of one eye has a beneficial modulating effect on the vertical pendular nystagmus in the fixating eye.     

The Stiles-Crawford effect in the eye of the blowfly, Calliphora erythrocephala

Stiles-Crawford-like effects (that is, directional sensitivity of the retina) were investigated in the fly's eye. Intracellular recordings from the visual sense cells were made, and the radiation patterns emerging from the photoreceptors with antidromic light were photographed, and evaluated with a microdensitometer. The measurements from both methods agree well, and can be satisfactorily described by a theoretical model based on waveguide theory. Clear radiation patterns from the first and second order modes were observed at the level of the cornea. As in the vertebrate eye, the photoreceptors are aligned towards the center of the lens, a phenomenon for which a theoretical explanation is proposed.     

Traumatic epithelial flap detachment after laser subepithelial keratomileusis

PURPOSE: To report a case of corneal epithelial flap detachment 20 days after laser subepithelial keratomileusis (LASEK). METHODS: A 30-year-old man underwent LASEK for correction of myopia. On postoperative day 8, he was comfortable and the corneal epithelium healed completely with uncorrected visual acuity (UCVA) of 20/20. On postoperative day 20, the corneal epithelial flap on the right eye detached and was lost during pressure patching after puncture of the hordeolum. RESULTS: The corneal defect was treated with a bandage contact lens, levofloxacin, and hyaluronic acid eye drops. Ten days after detachment, UCVA had improved to 20/20 and the epithelium had closed completely. CONCLUSIONS: Mild trauma can cause epithelial flap detachment during the early postoperative period of LASEK.     

Evaluation of eye patching after cataract surgery in topical anesthesia

BACKGROUND: Although postoperative eye patching is a common practice its background is not well known. Therefore the necessity of eye patching after cataract surgery in topical anesthesia from the medical point of view and the patients' subjective opinion was studied. PATIENTS AND METHODS: In this prospective and randomized study 133 patients received after cataract surgery either no covering of the eye (group1), a transparent eye shield for four hours (group 2), an eye pad for four hours (group 3) or an eye pad until the next morning (group 4). Clinical findings were noted and local symptoms, such as pain, foreign body sensation, tearing and photophobia were documented on a visual analogue scale (0 - 10). Furthermore, a questionnaire concerning the subjective opinion was handed out to the patient. RESULTS: The clinical findings revealed no significant differences between the groups. The mean values for local pain were 0.94 +/- 1.56, for the foreign body sensation 1.41 +/- 2.02, for tearing 0.99 +/- 1.8 and for photophobia 1.05 +/- 1.99. Comparing the groups there was significantly more pain and foreign body sensation reported by the patients in group 3, who received eye patching for 4 hours. 91 % of the unpatched patients had no discomfort, whereas 53 % of the patients wearing an eye pad until the next morning considered it as unnecessary. CONCLUSION: After cataract surgery in topical anesthesia only mild symptoms were noted. There were no significant differences between the groups in the objective clinical findings and the subjective feeling. These results indicate that after cataract surgery eye patching could be unnecessary.