Evaluating photoscreeners II: MTI and fortune videorefractor

Screening for visual impairment in children ages 1-5 years: update for the USPSTF

CONTEXT

Screening could identify preschool-aged children with vision problems at a critical period of visual development and lead to treatments that could improve vision.

OBJECTIVE

To determine the effectiveness of screening preschool-aged children for impaired visual acuity on health outcomes.

METHODS

We searched Medline from 1950 to July 2009 and the Cochrane Library through the third quarter of 2009, reviewed reference lists, and consulted experts. We selected randomized trials and controlled observational studies on preschool vision screening and treatments, and studies of diagnostic accuracy of screening tests. One investigator abstracted relevant data, and a second investigator checked data abstraction and quality assessments.

RESULTS

Direct evidence on the effectiveness of preschool vision screening for improving visual acuity or other clinical outcomes remains limited and does not adequately address whether screening is more effective than no screening. Regarding indirect evidence, a number of screening tests have utility for identification of preschool-aged children with vision problems. Diagnostic accuracy did not clearly differ for children stratified according to age, although testability rates were generally lower in children 1 to 3 years of age. Treatments for amblyopia or unilateral refractive error were associated with mild improvements in visual acuity compared with no treatment. No study has evaluated school performance or other functional outcomes.

CONCLUSIONS

Although treatments for amblyopia or unilateral refractive error can improve vision in preschool-aged children and screening tests have utility for identifying vision problems, additional studies are needed to better understand the effects of screening compared with no screening.

Wave-front analysis as screening technique for amblyogenic ametropia with and without cycloplegia

INTRODUCTION

For many years, attempts have been made to find an easy, efficient and inexpensive method to screen children for amblyogenic ametropia. Wave-front analysis is a new way to determine the refractive state of the eye from a distance. This technique could be a useful tool for infant screening.

PURPOSE

The purpose of the study was the evaluation of the efficacy of a commercially available wave-front analyzing autorefractometer (SureSight, software version 2.0, Welch Allyn, Skaneateles Falls, NY 13153, U.S.A.) in detecting amblyogenic ametropia in patients with and without cycloplegia.

METHODS

256 eyes (-28.25 D to +7.88 D spherical equivalent) of 128 patients (1-81 years) were examined with the wave-front autorefractometer under cycloplegia. Prior to this investigation, 108 eyes (-21.38 D to 75 D) of 54 of these patients (1-76 years) were refracted without cycloplegia. The readings of the wave-front autorefractometer were compared with the results of retinoscopy under cycloplegia.

RESULTS

Without cycloplegia, the sensitivity in detecting any amblyogenic ametropia such as anisometropia, astigmatism, myopia or hyperopia was 94%, while the specificity was 63%. Following cycloplegia, the sensitivity decreased to 87% and the specificity increased to 80%.

CONCLUSION

Wave-front analyzing refractometry is highly applicable for infant screening. At the present state of development, the efficacy in detecting amblyogenic ametropia is similar to that of other screening techniques and instruments that operate from distance. Cycloplegia enhances the sensitivity in detecting hyperopia and decreases the sensitivity in detecting astigmatism.

A cost-benefit analysis of vision screening methods for preschoolers and school-age children

INTRODUCTION

The purpose of this study was to determine costs and benefits of visual acuity screening (VAS) or photoscreening (PS) in children.

METHODS

A societal-perspective, decision-analytic model compared VAS and PS conducted in three age groups: children 6 to 18 months, 3 to 4 years, and 7 to 8 years old. Literature estimates of sensitivity, specificity, and prevalence were used. Cost estimates and referral rates for surgical treatment were derived from a managed care database and the United States Social Security Administration.

RESULTS

All the benefit-to-cost ratios exceeded 1.0, meaning that all screening programs studied had benefits that exceeded the cost of screening. The total net benefit was highest for PS in children of 3 to 4 years of age (19,412 US dollars) and the least for VAS in children 7 to 8 years of age (15,179 US dollars). The benefit-to-cost ratio was highest for the VAS in children 3 to 4 years of age (162 US dollars) and least for PS in infants 6 to 18 month old (140 US dollars). Sensitivity of the PS instrument and VAS charts were the most influential variables in determining the most cost-beneficial program.

CONCLUSIONS

Based on the best available data, the net benefit of PS in 3 to 4 year old preschool children is greater than VAS in children 7 to 8 years of age, PS in toddlers, and VAS in children 3 to 4 years of age.

Laboratory, clinical, and kindergarten test of a new eccentric infrared photorefractor (PowerRefractor)

PURPOSE

Photorefraction is a convenient way to determine refractive state from a distance. It is, therefore, useful for measuring infants and noncooperative subjects. However, its reliability (or precision) and accuracy (or validity) has been questioned. In a study in subjects without cycloplegia, we have tested whether, after complete automatization, eccentric photorefraction at a 1-m distance can be as reliable as a common autorefractor.

METHODS

In a laboratory study of 15 student subjects without the use of cycloplegia (30 eyes, refractive errors ranging from -6 D to +6 D), age 25 to 31 years, the photorefractive measurements were compared with spectacle prescriptions. In a clinical study, photorefraction, autorefraction, and subjective refraction were performed in 40 patients without cycloplegia (refractive errors ranging from -4 D to +4 D), most of them with various ocular pathologies. Subjective refractions were obtained by an experienced clinical ophthalmologist but were not accessible to the examiner who used the two refractors. Visual acuity was 20/20 or better except for five subjects. Ages ranged from 6 to 75 years. In the kindergarten screening study, 108 children aged 3 to 6 years were screened for refractive errors.

RESULTS

In the laboratory study, it was found that the mean difference between spectacle prescription and PowerRefractor measurements was < 0.6 D for spheres and below 0.4 D for cylinders. In the clinical study, data were obtained by all three procedures in 78 eyes. The photorefractor and the autorefractor performed similarly for spheres (mean absolute dioptric difference between refractor and subjective measure: 0.593 D and 0.696 D) and cylinders (mean absolute dioptric differences: 0.399 D and 0.389 D). However, the photorefractor was superior with regard to the measurement of the magnitude and axis of astigmatism (mean weighted difference between objective and subjective axis 0.644 D and 0.769 D, respectively). In the kindergarten study, it was found that the PowerRefractor was very convenient to handle. The autorefractor measured more myopic refractions than the PowerRefractor (mean of the left eyes 0.11 +/- 1.1 D vs. 0.62 +/- 0.53 D, p < 0.001). There was no indication that the PowerRefractor failed to detect hyperopia, because all but one child with more than 2 D of hyperopia measured with autorefractor (n = 7) was also hyperopic with the PowerRefractor. Furthermore, presenting an interesting fixation target at a 3-m distance did not cause more hyperopic refractions, indicating that the camera of the PowerRefractor at a 1-m distance was not a significant stimulus to accommodation.

CONCLUSIONS

The PowerRefractor was shown to have comparable or slightly better reliability and accuracy than a modern autorefractor; however, it has major advantages over current autorefractors in that it is faster, measures both eyes at once, and gives interpupillary distance, pupil size, and information on the alignment of the eyes at the same time.