Table 1

Table of experimental studies included in the review

RefyearDesignParticipantsInterventionFactors that might lead to or prevent biasSize of effectOCEBM level of evidence9
111980Controlled trial131 with intellectual disability and refractive errors
≥+2.0D, ≤0.5D, ≥1D anisometropia
Distance spectacles vs noneObservers not masked81% compliance at 8 weeks. Variable effects on multiple behaviours3
121987Before/after105 with intellectual disability and refractive errors ≥+2.5D, ≤−3.0D, ≥1.5D anisometropia or astigmatismDistance spectaclesObservers not masked but also used VEPs as objective outcome measureQualitative results given—VEPs larger after spectacles given in 58 of the 105. Some anecdotes of marked improvements in awareness3
231991Controlled trial17 (of 58) with severe visual impairment diagnosed <13 months of age and with severe learning difficultiesIndividualised vision training programme vs general development programmeA third of participants allocated by non-random procedure.
Masked observer for final outcome
Groups not matched for diagnoses
Separate data for children with VND not given but qualitatively VND group did better in vision training arm as compared with general development arm3
241999Before/after10 children with vision of only PL or worse and additional impairmentsTraining/practice in looking at striped visual stimuliObservers may not have been maskedTeller acuity card vision improved but number of blinks or fixations unchanged3
342005Controlled trial34 children with Down syndrome and accommodative lagBifocal spectaclesAllocation not random
Examiners not masked but no examiner bias seen on video review
Improvement in lag was 2.9 D in bifocals group vs 0.5`D in controls2
352009Before/after40 children with Down syndrome and accommodative lagBifocal spectaclesExaminers not masked38/40 showed accurate accommodation through bifocal near segment2
362010Before/after11 children with Down syndrome and accommodative lagBifocal spectaclesExaminers not masked
No baseline for visuoperceptual outcomes but accommodation was stable 5 months prior to intervention
Near acuity improved from 0.58 LogMAR to 0.42 LogMAR.
Variable improvements in visuoperceptual test results
372007Before/after5 children with CP using hyoscine patches; acuity at 1 m 6/30 or worseSpectacles giving clear focus at 1 mExaminers not maskedQualitative improvement in near vision3
461983Before/after10 children with CP and nystagmus and/or poor oculomotor controlTraining/practice in tracking moving target with eyes and/or other parts bodyExaminers not masked but objective outcome using eyetrackerAccuracy of smooth pursuit increased, sometimes markedly. Errors and latencies in saccadic movements decreased2
482008Before/after3 children with CP and nystagmusSelective dorsal rhizotomyExaminers not masked but objective outcome using eyetracker2 of the 3 showed improved accuracy of smooth pursuit3
521980Controlled cross-over trial4 children with CP and visual impairmentWhite light vs UV light for training in looking at a target objectExaminers not maskedOverall (p<0.001) more fixations on target in UV light condition2
531983Controlled trial13 children with IQ <20 and legally blind with some residual visionWhite light vs UV light for training in shape matching taskRandom allocation; examiner not maskedOverall (p<0.01) better score in post-test shape matching task if had been trained with UV light condition2
541998Before/after6 children with visual impairment and intellectual or multiple other impairmentsExposure to a MSEExaminers not masked
Prespecified list of behaviours used as outcome; inter-rate reliability of videotaped observations of behaviour 93%
Mean scores for prespecified skills observed on video greater after 5 weeks’ exposure to MSE, greater for visual impaired (88 vs 93) group than for autism group (95 vs 96)3
  • CP, cerebral palsy; MSE, multisensory environment; OCEBM, Oxford Centre for Evidence Based Medicine; PL, perception of light; UV, ultraviolet; VEP, visual evoked potential; VND, vision and neurodevelopmental.