Limits on improving the positive predictive value of the Welch Allyn SureSight for preschool vision screening

Preschool Vision Screening: Where We Have Been and Where We Are Going

PURPOSE

To discuss the evolution of instrument-based screening to detect amblyopia and its risk factors, and to summarize the importance of preschool vision screening.

DESIGN

Expert commentary.

METHODS

Author experiences were supplemented by a review and interpretation of pertinent medical literature.

RESULTS

Amblyopia remains a public health problem, as it is a common cause of monocular visual impairment. As a disease, amblyopia detection is best obtained by appropriate vision screening rather than by yearly mandated comprehensive eye examinations for all children; the US Preventative Services Task Force (USPSTF) recently reaffirmed their recommendations for vision screening in preschool children. Vision screening devices have evolved over the past 4 decades ranging from photoscreeners that use instantaneously developing film, to autorefractors that detect amblyopia risk factors, to nerve fiber layer scanners that detect the microtropia that nearly always accompanies amblyopia. When it is detected early, effective treatment for amblyopia can be initiated.

CONCLUSIONS

Amblyopia is a reversible cause of vision loss in children. Vision screening devices and screening programs have been extensively studied-experts and literature agree: vision screening devices and programs are cost-effective, are efficient, and are effective methods for amblyopia detection. The authors support the regular use of instrument-based vision screening in the medical home for all children until they reach a developmental stage where they can participate reliably in optotype-based vision screening.

Procedures for the Evaluation of the Visual System by Pediatricians

Vision screening is crucial for the detection of visual and systemic disorders. It should begin in the newborn nursery and continue throughout childhood. This clinical report provides details regarding methods for pediatricians to use for screening.

High specificity of the Pediatric Vision Scanner in a private pediatric primary care setting

PURPOSE

To determine the specificity of the Pediatric Vision Scanner, a binocular retinal birefringence scanner, in its intended setting, a pediatric primary care office.

METHODS

A total of 102 preschool children (age 2-6 years) were screened during a well-child pediatric visit using the Pediatric Vision Scanner and the SureSight Autorefractor and completed a masked comprehensive pediatric ophthalmic examination (gold standard examination).

RESULTS

Based on the gold standard examination, one child had anisometropic amblyopia, and the remaining 101 had no amblyopia or strabismus. Specificity of the Pediatric Vision Scanner was 90% (95% CI, 82%-95%) while specificity of the SureSight was 87% (95%CI, 79-93%). Combining these results with the sensitivity of the devices determined in our previous study conducted in a pediatric ophthalmology office setting, the positive likelihood ratio for the Pediatric Vision Scanner was 10.2; for the SureSight, 5.0. The negative likelihood ratio for the Pediatric Vision Scanner was 0.03; for the SureSight, 0.42, a significant difference.

CONCLUSIONS

The Pediatric Vision Scanner had high specificity (90%) in screening for amblyopia and strabismus as part of a pediatric well-child visit. Likelihood ratio analysis suggests that affected children have a high probability of being correctly identified by the Pediatric Vision Scanner. The high level of confidence conferred by Pediatric Vision Scanner screening may remove an important barrier to vision screening in pediatric primary care.

Beyond screening for risk factors: objective detection of strabismus and amblyopia

IMPORTANCE

Commercially available automated vision screening devices assess refractive risk factors, not amblyopia or strabismus, underreferring affected children and overreferring healthy children. Nearly half of affected children are not identified until after age 5 years, when treatment is less effective.

OBJECTIVES

To determine the diagnostic accuracy of the Pediatric Vision Scanner (PVS), a binocular retinal birefringence scanner, to objectively identify strabismus and amblyopia, and to compare retinal birefringence screening with a widely used automated pediatric screening device.

DESIGN, SETTING, AND PARTICIPANTS

Three hundred consecutive preschool children (aged 2-6 years) were screened using the PVS and the SureSight Autorefractor at 2 pediatric ophthalmology private practices. A masked comprehensive pediatric ophthalmic examination provided the gold standard for determining sensitivity and specificity for each screening device.

MAIN OUTCOMES AND MEASURES

The primary outcome was sensitivity and specificity of the PVS for detecting the targeted conditions, strabismus and amblyopia, in children aged 2 to 6 years. Secondary outcomes included the positive and negative likelihood ratios of the PVS for identifying the targeted conditions. In addition, sensitivity, specificity, and positive and negative likelihood ratios of the SureSight Autorefractor for the targeted conditions were assessed in the same cohort of children.

RESULTS

Of the 300 patients, 188 had strabismus only, amblyopia only, or both, and 112 had no strabismus or amblyopia. The sensitivity of the PVS to detect strabismus and amblyopia (0.97; 95% CI, 0.94-1.00) was significantly higher than that of the SureSight Autorefractor (0.74; 95% CI, 0.66-0.83). Specificity of the PVS for strabismus and amblyopia (0.87; 95% CI, 0.80-0.95) was significantly higher than that of the SureSight Autorefractor (0.62; 95% CI, 0.50-0.73).

CONCLUSIONS AND RELEVANCE

The PVS identified children with strabismus and/or amblyopia with high sensitivity, outperforming the SureSight Autorefractor. Accurate, early detection of these conditions could improve long-term vision outcomes of affected preschool children.

Preschool vision screening: update on guidelines and techniques

PURPOSE OF REVIEW

To discuss the current preschool vision screening (PVS) guidelines and review some of the newest vision screening techniques. The different vision screening practices and barriers to screening are discussed.

RECENT FINDINGS

Vision screening guidelines, which have been developed in response to the advances in technology and increased understanding of the developing visual system, have been recently updated by some of the major medical organizations that endorse vision screening. With advances in vision screening technology, there is a growing trend for screening at younger ages.

SUMMARY

PVS has been widely endorsed by various medical organizations as an effective way to detect preventable and treatable vision problems of childhood. Although PVS is widely recommended, actual screening rates remain low. There are several real and perceived barriers to screening which often prevents successful screening programs. Current vision screening guidelines take into account the recent advances in technology. With the development of new devices, vision screening can effectively be performed at younger ages.

Utility of an open field Shack-Hartmann aberrometer for measurement of refractive error in infants and young children

PURPOSE

To assess the utility of an open-field Shack-Hartmann aberrometer for measurement of refractive error without cycloplegia in infants and young children.

METHOD

Data included 2698 subject encounters with Native American infants and children aged 6 months to <8 years. We attempted right eye measurements without cycloplegia using the pediatric wavefront evaluator (PeWE) on all participants while they viewed near (50 cm) and distant (2 m) fixation targets. Cycloplegic autorefraction (Rmax [Nikon Retinomax K-plus2]) measurements were obtained for children aged ≥ 3 years.

RESULTS

The success rates of noncycloplegic PeWE measurement for near (70%) and distant targets (56%) significantly improved with age. Significant differences in mean spherical equivalent (M) across near versus distant fixation target conditions were consistent with the difference in accommodative demand. Differences in astigmatism measurements for near versus distant target conditions were not clinically significant. Noncycloplegic PeWE and cycloplegic Rmax measurements of M and astigmatism were strongly correlated. Mean noncycloplegic PeWE M was significantly more myopic or less hyperopic and astigmatism measurements tended to be greater in magnitude compared with cycloplegic Rmax.

CONCLUSIONS

The PeWE tended to overestimate myopia and underestimate hyperopia when cycloplegia was not used. The PeWE is useful for measuring accommodation and astigmatism.

Prevalence of astigmatism in Native American infants and children

PURPOSE

To describe the prevalence of high astigmatism in infants and young children who are members of a Native American tribe with a high prevalence of astigmatism.

METHODS

SureSight autorefraction measurements were obtained for 1461 Tohono O'odham children aged 6 months to 8 years.

RESULTS

The prevalence of astigmatism >2.00 diopters was 30% in Tohono O'odham children during infancy (6 months to <1 year of age) and was 23 to 29% at ages 2 to 7 years. However, prevalence dipped to 14% in children 1 to <2 years of age. At all ages, axis of astigmatism was with-the-rule (plus cylinder axis 90 degrees +/- 30 degrees ) in at least 94% of cases.

CONCLUSIONS

As in non-Native American populations, Tohono O'odham infants show a high prevalence of astigmatism, which decreases in the second year of life. However, the prevalence of high astigmatism in Tohono O'odham children increases by age 2 to <3 years to a level near that seen in infancy and remains at that level until at least age 8 years. Longitudinal data are needed to determine whether the increase in high astigmatism after infancy occurs in infants who had astigmatism as infants or is due to the development of high astigmatism in children who did not show astigmatism during infancy.

Impact of confidence number on accuracy of the SureSight Vision Screener

PURPOSE

To assess the relation between the confidence number provided by the Welch Allyn SureSight Vision Screener and screening accuracy, and to determine whether repeated testing to achieve a higher confidence number improves screening accuracy in pre-school children.

METHODS

Lay and nurse screeners screened 1452 children enrolled in the Vision in Preschoolers (VIP) Phase II Study. All children also underwent a comprehensive eye examination. By using statistical comparison of proportions, we examined sensitivity and specificity for detecting any ocular condition targeted for detection in the VIP study and conditions grouped by severity and by type (amblyopia, strabismus, significant refractive error, and unexplained decreased visual acuity) among children who had confidence numbers < or =4 (retest necessary), 5 (retest if possible), > or =6 (acceptable). Among the 687 (47.3%) children who had repeated testing by either lay or nurse screeners because of a low confidence number (<6) for one or both eyes in the initial testing, the same analyses were also conducted to compare results between the initial reading and repeated test reading with the highest confidence number in the same child. These analyses were based on the failure criteria associated with 90% specificity for detecting any VIP condition in VIP Phase II.

RESULTS

A lower confidence number category were associated with higher sensitivity (0.71, 0.65, and 0.59 for < or =4, 5, and > or =6, respectively, p = 0.04) but no statistical difference in specificity (0.85, 0.85, and 0.91, p = 0.07) of detecting any VIP-targeted condition. Children with any VIP-targeted condition were as likely to be detected using the initial confidence number reading as using the higher confidence number reading from repeated testing.

CONCLUSIONS

A higher confidence number obtained during screening with the SureSight Vision Screener is not associated with better screening accuracy. Repeated testing to reach the manufacturer's recommended minimum value is not helpful in pre-school vision screening.

Accuracy of the Welch Allyn SureSight for measurement of magnitude of astigmatism in 3- to 7-year-old children

PURPOSE

To evaluate the accuracy of the Welch Allyn SureSight in noncycloplegic measurements of astigmatism as compared to cycloplegic Retinomax K+ autorefractor measurements of astigmatism in children from a Native American population with a high prevalence of high astigmatism.

METHODS

Data are reported for 825 3- to 7-year-old children with no ocular abnormalities. Each child had a Retinomax K+ cycloplegic measurement of right eye astigmatism with a confidence rating > or =8 and 3 attempts to obtain a SureSight measurement on the right eye.

RESULTS

SureSight measurement success rates did not differ significantly across age or measurement confidence rating (<6 vs > or =6). Ninety-six percent of children had at least 1 measurement (any confidence), and 89% had at least 1 measurement with confidence at the manufacturer's recommended value (> or =6). Overall, the SureSight tended to overestimate astigmatism. If the SureSight measurement had any dioptric value (0.00 D to 3.00 D), astigmatism of 2.00 D or less was likely to be present. If the SureSight showed astigmatism beyond the instrument's dioptric range (>3.00 D), Retinomax K+ measurements indicated that >2.00 D of astigmatism was present in 136 of 157 (86.6%). In cooperative children for whom the SureSight would not give a reading, 32 of 34 (94%) had >3.00 D of astigmatism.

CONCLUSIONS

The SureSight does not provide an accurate, quantitative measure of amount of astigmatism. However, it does allow accurate categorization of amount of astigmatism as < or =2.00 D, >2.00 D, or >3.00 D, and it has high measurement success rate in young children.