Screening for amblyopia in preverbal children with photoscreening photographs. National Children's Eye Care Foundation Vision Screening Study Group

A Systematic Review of Current Teleophthalmology Services in New Zealand Compared to the Four Comparable Countries of the United Kingdom, Australia, United States of America (USA) and Canada

Background

Over 700,000 New Zealanders (NZ), particularly elderly and Māori, live without timely access to specialist ophthalmology services. Teleophthalmology is a widely recognised tool that can assist in overcoming resource and distance barriers. Teleophthalmology gained unprecedented traction in NZ during the COVID-19 pandemic and subsequent lockdown. However, its provision is still limited and there are equity issues. The aim of this study was to conduct a systematic review identifying, describing and contrasting teleophthalmology services in NZ with the comparable countries of Australia, USA, Canada and the United Kingdom.

Methods

The electronic databases Embase, PubMed, Web of Science, Google Scholar and Google were systemically searched using the keywords: telemedicine, ophthalmology, tele-ophthalmology/teleophthalmology. The searches were filtered to the countries above, with no time constraints. An integrative approach was used to synthesise findings.

Results

One hundred and thirty-two studies were identified describing 90 discrete teleophthalmology services. Articles spanned from 1997 to 2020. Models were categorised into general eye care (n=21; 16%); emergency/trauma (n=6; 4.5%); school screening (n=25; 19%); artificial intelligence (AI) (n=23; 18%); and disease-specific models of care (MOC) (n=57; 43%). The most common diseases addressed were diabetic retinopathy (n=23; 17%); retinopathy of prematurity (n=9; 7%); and glaucoma (n=8; 6%). Programs were mainly centred in the US (n=72; 54.5%), followed by the UK (n=29; 22%), then Canada (n=16; 12%), Australia (n=13; 10%), with the fewest identified in NZ (n=3; 2%). Models generally involved an ophthalmologist consultative service, remote supervision and triaging. Most models involved local clinicians transmitting fed-forward or live images.

Conclusion

Teleophthalmology will likely play a crucial role in the future of eye care. COVID-19 has offered a unique opportunity to observe the use of teleophthalmology services globally. Feed-forward and, increasingly, live-based teleophthalmology services have demonstrated feasibility and cost-effectiveness in similar countries internationally. New Zealand’s teleophthalmology services, however, are currently limited. Investing in strategic partnerships and technology at a national level can advance health equities in ophthalmic care.

Utilizing minicomputer technology for low-cost photorefraction: a feasibility study

Eccentric photorefraction is an objective technique to determine the refractive errors of the eye. To address the rise in prevalence of visual impairment, especially in rural areas, a minicomputer-based low-cost infrared photorefractor was developed using off-the-shelf hardware components. Clinical validation revealed that the developed infrared photorefractor demonstrated a linear working range between +4.0 D and -6.0 D at 50 cm. Further, measurement of astigmatism from human eye showed absolute error for cylinder of 0.3 D and high correlation for axis assessment. To conclude, feasibility was shown for a low-cost, portable and low-power driven stand-alone device to objectively determine refractive errors, showing potential for screening applications. The developed photorefractor creates a new avenue for telemedicine for ophthalmic measurements.

The effect of developmentally-at-risk status on the reliability of the iScreen® photorefractive device in young children

INTRODUCTION AND PURPOSE

We evaluated the impact of developmentally-at-risk status on the results of photorefractive screening with iScreen®.

PATIENTS AND METHODS

We sequentially recruited 169 children (aged 2-5 years) to participate in a blinded, prospective study of a photoscreening device. The principle investigator examined the children after photoscreening. Using established standards for amblyogenic factors, the principle investigator and photoscreen interpreters separately made a determination of "normal" or "needs referral" for each child. Sensitivity, specificity, positive predictive value, and negative predictive value for the photoscreening device were determined.

RESULTS

Overall, sensitivity was 85% with a positive predictive value of 98%, and specificity was 87% with a negative predictive value of 47%. Developmentally-at-risk status in 34 children (three refused imaging) did not reduce sensitivity (89%) or specificity (100%) when compared with 130 children (two refused imaging) who did not have developmentally-at-risk factors (sensitivity = 84% and specificity = 80%).

CONCLUSION

The efficacy of photorefractive screening in young children with developmentally-at-risk status is comparable to results found in normal children.

The value of serial personal photographs in timing the onset of unilateral cataracts in children

PURPOSE

To determine the value of serial personal photographs in timing the onset of unilateral cataracts in children over 6 months of age.

METHODS

Personal photographs from children with unilateral cataracts who underwent cataract extraction and intraocular lens implantation when > or =6 months of age were reviewed. Photographs were evaluated for changes in the red reflex, which might indicate the presence of a cataract.

RESULTS

Twelve children underwent cataract surgery at a mean age of 37 months. They were followed for a mean of 32 months. Ten children were diagnosed as having an acquired cataract by photographic review documenting a previously normal red reflex. The visual acuity in the affected eye of 4 of these children improved to > or =20/60. Cataracts were visible on photographs prior to clinical diagnosis in 6 patients, from 0.5 to 22 months prior to clinical diagnosis. Visual outcomes did not relate closely to the photographically documented duration of the cataract prior to treatment. Photographs were not helpful in timing the onset of cataract in 2 children due to the poor quality of the images.

CONCLUSIONS

Serial personal photographs are sometimes helpful in determining whether cataracts are acquired. However, the usefulness of personal photographs alone in predicting the visual outcome after cataract surgery was limited in this small, retrospective study.

A comparison of photorefraction and retinoscopy in children

PURPOSE

To compare the results of photorefraction measurement obtained with a Plusoptix CR03 to those of cycloplegic retinoscopy as a standard refraction method in children.

METHODS

We assessed the refractive status of 204 eyes in 204 healthy children. The values acquired via photorefraction (noncycloplegic refraction) with a Plusoptix CR03 device were compared with those obtained via cycloplegic retinoscopy. Both methods were used in the same eyes and in all children. The paired tt-test and Pearson's correlation analysis were used for statistical analysis.

RESULTS

The mean age was 7.1 +/- 2.4 years (range, 9 months to 14 years). The average spherical refractive error was +0.05 +/- 0.65 D for photorefraction versus +0.75 +/- 0.77 D for cycloplegic retinoscopy (average difference, -0.70 D; p < 0.001), with moderate correlation between measures (r = 0.63). The average cylinder power was +0.43 +/- 0.38 D for photorefraction versus +0.29 +/- 0.38 D for cycloplegic retinoscopy (average difference, +0.14 D; p < 0.001), with moderate correlation between measures (r = 0.70). The average spherical equivalent was +0.26 +/- 0.63 D for photorefraction versus +0.90 +/- 0.76 D for cycloplegic retinoscopy (average difference, -0.64 D; p < 0.001), with moderate correlation between measures (r = 0.63).

CONCLUSIONS

The Plusoptix CR03 device tends toward minus overcorrection in children, resulting in overdiagnosis of myopia. Studies of a population of subjects with a larger range of ametropia will be required to validate this instrument as a screening tool.

Infant hyperopia: detection, distribution, changes and correlates-outcomes from the cambridge infant screening programs

PURPOSE

To report on two population screening programs designed to detect significant refractive errors in 8308 8- to 9-month-old infants, examine the sequelae of infant hyperopia, and test whether early partial spectacle correction improved visual outcome (strabismus and acuity). The second program also examined whether infant hyperopia was associated with developmental differences across various domains such as language, cognition, attention, and visuomotor competences up to age 7 years. Linked programs in six European countries assessed costs of infant refractive screening.

METHOD

In the first program, screening included an orthoptic examination and isotropic photorefraction, with cycloplegia. In the second program we carried out the same screening procedure without cycloplegia. Hyperopic infants (> or = +4 D) were followed up alongside an emmetropic control group, with visual and developmental measures up to age 7 years, and entered a controlled trial of partial spectacle correction.

RESULTS

The second program showed that accommodative lag during photorefraction with a target at 75 cm (focus > or = +1.5 D) was a marker for significant hyperopia. In each program, prevalence of significant hyperopia at 9 to 11 months was around 5%; manifest strabismus was 0.3% at 9 months and 1.5 to 2.0% by school age. Infant hyperopia was associated with increased strabismus and poor acuity at 4 years. Spectacle wear by infant hyperopes produced better visual outcome than in uncorrected infants, although an improvement in strabismus was found in the first program only. The corrections did not affect emmetropization to 3.5 years; however, both corrected and uncorrected groups remained more hyperopic than controls in the preschool years. The hyperopic group showed poorer overall performance than controls between 1 and 7 years on visuoperceptual, cognitive, motor, and attention tests, but showed no consistent differences in early language or phonological awareness. Relative cost estimates suggest that refractive screening programs can detect visual problems in infancy at lower overall cost than surveillance in primary care.

CONCLUSIONS

Photo/videorefraction can successfully screen infants for refractive errors, with visual outcomes improved through early refractive correction. Infant hyperopia is associated with mild delays across many aspects of visuocognitive and visuomotor development. These studies raise the possibility that infant refractive screening can identify not only visual problems, but also potential developmental and learning difficulties.

Validation of the PowerRefractor for measuring human infant refraction

PURPOSE

Eccentric photorefraction provides an opportunity to gather rapid and remote estimates of refraction and gaze position from infants. The technique has the potential for extensive use in vision screenings and studies of visual development. The goal of this study was to assess the refraction calibration of the PowerRefractor (Multichannel Systems) for use with uncyclopleged infants.

METHODS

The defocus measurements from the instrument were compared with the results of simultaneous retinoscopy in one analysis and with known amounts of defocus induced with trial lenses in another. Data were collected from infants 1 to 6 months of age and adults.

RESULTS

The PowerRefractor typically read < 1 D of myopia when the retinoscopy reflex was judged to be neutral at the same working distance in both infants and adults. The slopes of both infant and adult validation functions (trial lens power vs. measurement of induced defocus) were close to 1 over a 4D range. The infant slopes were significantly greater than those of the adults, however.

CONCLUSIONS

The results suggest that the instrument is capable of detecting large amounts of defocus but needs individual calibration for detailed studies of accommodative accuracy and absolute levels of defocus, as has been recommended previously for adult subjects.

Predictive value of photoscreening and traditional screening of preschool children

PURPOSE

To compare the usefulness of traditional vision screening and photoscreening of 3- and 4-year-old children in the pediatrician's office.

METHODS

Following training of pediatricians and office staff, six pediatric clinics used both the MTI PhotoScreener (Medical Technology Industries, LLC, Riviera Beach, FL) and traditional acuity and stereopsis screening materials (HOTV charts/Random Dot E tests as recommended by established AAP-MCHB-PUPVS guidelines) during well-child exams. Clinics used one testing method for a 6-month period and switched to the other for the following 6 months, in a randomized manner. Referred children received a complete eye examination with cycloplegic refraction by local ophthalmologists or optometrists who forwarded the results to Vanderbilt Ophthalmology Outreach Center. Amblyogenic factors were defined using standardized published criteria.

RESULTS

Six hundred five children were screened with the photoscreener and 447 were screened with traditional techniques. Mean time for screening was less with the photoscreener: 2.5 versus 5.9 minutes ( P < 0.01). Untestable rates were similar (18% vs 10%, respectively P = NS), but higher with the photoscreener due to one clinic's 70% unreadable rate. Referral rates were also similar: 3.8% versus 4.5%. The positive predictive value (PPV) rate differed greatly. With follow-up results obtained from 56% of referred children, 73% of photoscreening referred children (8/11 examined) had amblyogenic factors confirmed on formal eye exams, whereas all children referred using traditional screening methods (10/10 examined) were normal.

CONCLUSION

Photoscreening is more time efficient than traditional screening and has a significantly higher PPV in 3- and 4-year-old children. This study was unable to validate traditional screening techniques in this preschool age group. If these results can be replicated, support for traditional vision screening must undergo intense scrutiny, and attention should be turned toward making photoscreening feasible for widespread implementation.

The cost and yield of photoscreening: impact of photoscreening on overall pediatric ophthalmic costs

BACKGROUND

Approximately 5% of preschool-age children suffer from amblyopia. Many of them have high or unequal hyperopia. Amblyogenic risk factors frequently can be detected by photoscreening.

METHODS

Free photoscreening was offered to Alaskan children ages 1 to 5 from urban and rural screening hubs. Screened images were mailed to the Alaska Blind Child Discovery coordinating center for physician photoscreen interpretation, specifically seeking latent or anisometropic hyperopia. Parents and screeners then were mailed results and information about amblyopia. Follow-up examination data were tallied, and a cost-consequence analysis was developed for various vision screening paradigms and eye care.

RESULTS

From 1996 through 2003, a total of 13,255 screenings were performed with a positive interpretation rate of 4.7%. Penetrance of screening was 22% in urban and 44% in rural communities. Positive predictive value was estimated to be more than 90%. Average cost to screen and inform an Alaskan preschooler was approximately 10.67 dollars, and cost to detect amblyogenic risk factors by photoscreening in an Alaskan was approximately 206 dollars. Compared to American Academy of Pediatrics (AAP) 1995 guidelines, implementing photoscreening added 9%, while mandating complete prekindergarten examination added 49% to overall eye care.

CONCLUSIONS

MTI photoscreening achieved high community penetrance and high positive predictive value for latent hyperopia and other amblyogenic factors. When follow-up costs are considered, adding photoscreening to current AAP guidelines may add 112 dollars per child over 10 years, but probably would assist in the reduction of amblyopia. Penetrance of urban photoscreening likely will remain low unless pediatric vision screening guidelines and reimbursement are revised.

A new visual evoked potential system for vision screening in infants and young children

INTRODUCTION

With a prevalence of 3-5%, amblyopia represents a major public health problem. Effective treatment depends on early detection, and a broad consensus of professional opinion supports vision screening of infants and young children. No single method of screening has been demonstrated to be superior in detecting amblyopia and all methods have significant limitations.

METHODS

We assessed a new, "child-friendly" visual evoked potential (VEP) system (ENFANTtrade mark II, Diopsys Corp., Metuchen, NJ) for use in screening. We studied 122 children, aged 6 months to 5 years, comparing test results in a masked fashion to results of standard ophthalmologic examinations. A statistical program analyzed VEP differences between fellow eyes to determine a "pass" or "fail" for each child. For verbal patients, clinical amblyopia was defined as an interocular difference of two or more lines in best-corrected visual acuity. For preverbal patients, clinical amblyopia was defined by the clinician's decision to treat with occlusion or atropine penalization. Preverbal children with significant refractive errors or structural eye pathology were also considered clinically abnormal.

RESULTS

The test was completed by 94% of the study group, each child requiring an average of 10 minutes to complete testing of both eyes. The sensitivity was 0.973, the specificity 0.808, the positive predictive value 0.706, and the negative predictive value 0.984.

CONCLUSION

With its easy electrode placement and rapid, attractive stimulus, the new system overcomes technical difficulties which were associated with older VEP techniques. The test shows promise as a screening tool for detecting amblyopia and other visual deficits in young children.

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.

Follow-up data their use in evidence-based decision-making

Experience with certain perinatal interventions, such as supplemental oxygen and dexamethasone, leads to the conclusion that follow-up data are needed to be well informed about the safety of certain perinatal interventions. Experience with indomethacin suggests that follow-up data also are regarded by some clinicians as a necessary aspect of evidence about effectiveness. Ideally, clinical trials of perinatal interventions might involve collection of data about neonatal predictors of outcome (such as a neuroimaging study and a standardized neurologic assessment); several developmental and neurologic assessments before school entry; a comprehensive evaluation of the child's cognitive function, behavioral competencies, and academic performance at 7 to 8 years of age; serial detailed assessments of the family psychosocial functioning; and an inventory of resources available for the child. Many clinical trials have not included follow-up after the neonatal period, and in such cases information about the effect of the intervention on participants' HRQL is incomplete. The approach taken in several recent trials, in which the outcome of interest is neurodevelopmental outcome at 18 months, attempts to strike a balance between a theoretical ideal (a comprehensive, longitudinal follow-up through school age) and a follow-up regimen that is not prohibitively expensive. Such trials include follow-up during the first 1 to 3 years of life, when major disabilities can be identified reliably, thereby providing moderately informative data about participants' eventual quality of life, related to the presence or absence of major disability. If, however, there is reason to suspect that the intervention has effects on the developing brain, follow-up after school entry may provide additional evidence pertinent to the risks and benefits of the intervention.

The eye examination in the pediatrician's office

The visual system of children must be routinely examined by the pediatrician. Speed, skill and diagnostic abilities will increase quickly as the examination techniques described here are practiced on a daily basis. When parents recognize that the pediatrician is also concerned about their child's visual health and development, they will play a more active role in obtaining crucial family ocular history, note ocular changes that otherwise may be ignored, and, if indicated, participate in the referral and treatment process to avoid life-long visual consequences.

Sensitivity of photoscreening to detect high-magnitude amblyogenic factors

PURPOSE

To determine the sensitivity of a unique pupil-size based set of referral criteria of the MTI PhotoScreener(Medical Technology and Innovations, Inc, Cedar Falls, Iowa) to detect high magnitude refractive error.

METHODS

The photoscreening photographs of 949 preschool children previously analyzed were reevaluated with the new referral criteria. The original photographs had been obtained from pediatricians' offices and public health and Women, Infants, and Children's (WIC) clinics. The results of this analysis were compared with the gold standard clinical examination and cycloplegic refraction. Sensitivities were calculated for amblyogenic factors based on the magnitude of the refractive error.

RESULTS

For 26 patients with anisometropia, the sensitivity to detect anisometropia increased from 46% for +1.25 or greater spherical interocular difference to 100% for +2.50 spherical intraocular difference. For 36 patients with hypermetropia in at least 1 meridian ranging from +3.75 to +7.50 D, sensitivity increased from 53% to detect +3.75 D or greater to 70% for +5.00 D or greater. The sensitivity to detect hypermetropia of +5.75 D or greater was 100%. These criteria detected 82% of patients with astigmatism greater than or equal to +3.00 D, and 100% of patients with astigmatism greater than +3.50 D.

CONCLUSION

It is crucial that screening programs avoid over-referrals caused by high false-positive screening rates. The sensitivity of our new criteria increases with higher magnitude refractive error; patients with moderate and severe amblyogenic factors are almost never missed. While the sensitivity to detect lower magnitude refractive error is poor, the amblyogenic impact of such errors remains to be determined.

Use of photoscreening for children's vision screening

This statement asserts that all children should be screened for risk factors associated with amblyopia. Guidelines are suggested for the use of photoscreening as a technique for the detection of amblyopia and strabismus in children of various age groups. The American Academy of Pediatrics favors additional research of the efficacy and cost-effectiveness of photoscreening as a vision screening tool.

Non-cycloplegic screening for refractive errors in children with the hand-held autorefractor Retinomax: final results and comparison with non-cycloplegic photoscreening

AIMS

To establish the results of refractive screening of preschool children with the hand-held autorefractor Retinomax under non-cycloplegic conditions, and to compare these results with those of photoscreening.

METHODS

Among 1218 children undergoing non-cycloplegic refractive screening, 302 (25%) were also refracted under cycloplegia using the same refractor and were used as controls. Our criteria for a positive screening test were based on the spherical or cylinder values and were: myopia over 3D, astigmatism > or = 2D, spherical or cylindrical anisometropia > or = 1.5D, and hyperopia > or = 1.5D. Absolute myopia over 3D, absolute astigmatism > or = 2D, absolute anisometropia > or = 1.5D and absolute hyperopia > 3.5D were considered as true positives. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated within the group of controls for each refractive anomaly. On the basis of Bayes' theorem, these figures were then corrected to yield the true screening results that would be expected in a population without verification and selection bias. To determine the usefulness of this screening technique, the likelihood ratios for positive test results (+LR) were also calculated. The results of this screening in terms of sensitivity, specificity and predictive values were then compared with those of photoscreening.

RESULTS

The basic results of screening with the hand-held autorefractor were as follows: -EHyperopia: sensitivity 46%, specificity 97%, PPV 55%, NPV 96%, +LR 15; -EAstigmatism: sensitivity 37%, specificity 99%, PPV 69%, NPV 96%, +LR 37; -EAnisometropia: sensitivity 66%, specificity 93%, PPV 19%, NPV 99%, +LR 9; -EMyopia: sensitivity 87%, specificity 99%, PPV 33%, NPV 100%, +LR 87. The comparison with photoscreening revealed a similar performance when screening for hyperopia, but the hand-held autorefractor yielded much better figures when screening for astigmatism. In the case of myopia and anisometropia, the lack of consistent information concerning photoscreening invalidates any comparison.

CONCLUSION

The hand-held autorefractor Retinomax appears to have potential as a screening device. Our experience with the non-cycloplegic screening of preschool children for refractive anomalies indicates definite usefulness and reasonable accuracy of the Retinomax for detecting myopia, astigmatism and hyperopia. The weak point of this screening technique is the diagnosis of anisometropia, with only moderate utility and poor accuracy.

Detection of improper fixation in MTI photoscreening images

PURPOSE

To determine the effect of fixation shift on photoscreening crescents, the ability of human interpreters to detect fixation shift, and the potential improvement by image processing.

METHODS

MTI photoscreening (Medical Technologies & Innovations, Inc, Lancaster, PA) images, measured at 11 positions of gaze, were obtained from 10 subjects (9 with refractive error warranting spectacle correction). Photographs were taken with subjects fixating at 20, 15, 10, and 5 cm to the left and the right of the camera fixation target (1 m distant); 5 cm above and below the camera fixation target; and on-axis. Photographs were inspected by 11 experienced raters, who indicated if the subject appeared to be looking directly at the camera. The photographs were digitized, enlarged, contrast enhanced, and measured by 3 raters. For each photograph, distance from the corneal light reflex to the nasal limbus was measured and a measure of asymmetry computed.

RESULTS

Raters could reliably detect off-axis fixation greater than 10 cm away from the intended fixation target. Raters correctly identified on-axis subject viewing 73% of the time. Crescents became larger when the fixation shifted off-axis for both the myopic and hyperopic subjects. Image analysis correctly classified 10 of 10 on-axis measurements and 34 of 39 off-axis measurements.

CONCLUSION

Direct inspection of photoscreening images by trained raters can result in the failure to detect small but relevant errors of fixation. These fixation shifts can cause crescents to become larger than expected, resulting in false-positive classification. Image analysis offers a potential improvement in the detection of off-axis fixation in MTI photoscreening images.

Inter-rater and intra-rater reliability in the interpretation of MTI Photoscreener photographs of Native American preschool children

PURPOSE

To evaluate inter- and intra-rater reliability for the interpretation of MTI Photoscreener photographs taken in a population of Native American preschool children with a high prevalence of astigmatism.

METHODS

Photographs of 369 children were rated by 11 nonexpert and 3 expert raters. Photographs for each child were scored as pass, refer, or retake. Nonexpert raters scored photos on two separate occasions, permitting analysis of intra-rater reliability.

RESULTS

Analyses of pass/refer responses only: inter-rater reliability was moderate to substantial among nonexpert raters and substantial among expert raters. Intra-rater reliability among nonexperts was substantial. Analyses of all responses (pass, refer, and retake): inter-rater reliability for pass and refer scores was moderate among nonexperts and substantial among experts; for retake scores inter-rater reliability was slight for nonexperts and moderate for experts. Intra-rater reliability among nonexperts was substantial for pass and refer scores and moderate for retake scores.

CONCLUSIONS

In this population with a high prevalence of astigmatism, whether MTI photoscreening results are interpretable is much more variable among and within raters than whether an interpretable photograph should be scored as pass or refer. The level of agreement among raters in the current study was influenced by the experience of the raters. In addition, nonexpert raters were more likely to deem a photograph uninterpretable than expert raters.

Screening for amblyopia in preverbal children with photoscreening photographs: II. Sensitivity and specificity of the MTI photoscreener

OBJECTIVE

To determine the sensitivity and specificity of vision screening using the Medical Technology and Innovations (MTI), Inc., PhotoScreener.

DESIGN

Cross-sectional study. PARTICIPANTS AND TESTING: Three hundred ninety-two children less than 4 years of age received a complete ophthalmologic examination and were photographed using the MTI PhotoScreener. One hundred three children had normal examinations, and the remaining 284 children had conditions of interest for pediatric screening: ptosis, media opacity, refractive error, or strabismus. Five children were excluded.

MAIN OUTCOME MEASURES

The grading of the photographs by the manufacturer's representative was compared with the results of the ophthalmologic examinations. Sensitivity and specificity of vision screening were determined.

RESULTS

The analysis of all informative photographs resulted in a sensitivity of 65% and a specificity of 87%. The sensitivity of detection for children with some forms of strabismus was high, up to 95% for esotropia of 10Delta or more. Sensitivities for the detection of ptosis, media opacity, and refractive error were poor in patients where strabismus was not also present.

CONCLUSIONS

The MTI PhotoScreener may play a role in preverbal vision screening; identification of two of three children with amblyopiogenic factors before age 4 would be an exciting advance in public health. However, improvement in the ability to identify children with media opacity and refractive error is necessary. Improvements may be possible with modifications of the examination failure and photograph grading criteria.

Screening for amblyogenic factors using a volunteer lay network and the MTI photoscreener. Initial results from 15,000 preschool children in a statewide effort

PURPOSE

To describe the results from a statewide preschool vision screening program using the MTI PhotoScreener (Medical Technology and Innovations, Inc., Cedar Falls, IA).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 15,059 children aged 6 to 47 months enrolled in childcare and preschool settings throughout the state of Tennessee.

METHODS

Volunteers from local Lions Clubs took photoscreening photographs of children in a statewide effort. Photographs were interpreted at the Vanderbilt Ophthalmic Photography Reading Center using predetermined criteria. Children who failed the screening were referred to community ophthalmologists or optometrists who performed a comprehensive evaluation and forwarded the results to the authors.

MAIN OUTCOME MEASURES

Referral rate, unreadable rate, and predictive value positive (PVP).

RESULTS

During the 2 years of the screening program, 15,059 children were screened in 850 screenings. The screening referred 1013 children (6.7%), and 704 photographs (4.7%) were unreadable. Children who failed the screening had a significant abnormality (strabismus, anisometropia, high hypermetropia, high astigmatism, or high myopia) in 320 of the 531 cases where adequate follow-up results were reported. The PVP ranged from 84% when a diagnosis of strabismus was suggested by the photoscreen reading to 41% for astigmatism. Despite intense attention to follow-up, many children who failed the screening never received a formal eye examination.

CONCLUSIONS

The MTI PhotoScreener can be used by volunteers to screen preschool children and can have a high PVP in organized settings, provided that meticulous attention is paid to photograph interpretation and quality control. The PVP of the MTI PhotoScreener depends on the diagnosis suggested when the photograph is read. Significant obstacles exist in obtaining care for those who fail screening.

Evaluation of the iScreen digital screening system for amblyogenic factors

BACKGROUND

A digital photoscreener, the iScreen screening system, is now available to detect amblyogenic factors. We carried out a prospective study to evaluate the accuracy of the device in detecting anisometropia, significant refractive error, strabismus and opacities of the ocular media.

METHODS

A total of 449 consecutive patients (median age 7 years) from a private pediatric ophthalmology practice underwent screening with the iScreen photoscreener operated by a minimally trained technician. The results were compared to the masked clinical examination of a pediatric ophthalmologist.

RESULTS

The iScreen device had a sensitivity of 92.4%, specificity of 89.1%, positive predictive value of 94.1% and false-negative rate of 13.8%. Of the 21 patients with a false-negative result, 12 had myopia of less than -1.50 dioptres. High hyperopia was missed in two patients, high astigmatism in one, unequal cylindrical error in one and strabismus in five.

INTERPRETATION

The iScreen digital photoscreener produced accurate and timely screening for potentially amblyogenic defects in the study population.

Development of refraction and strabismus

In the past year, as in recent years, most of the research on the development of refraction has focused on the following: 1) mechanisms whereby the eye can maintain coordinated growth to achieve emmetropia and 2) disruptions of emmetropization resulting in myopia or hyperopia. Preterm children and those with Down syndrome have higher refractive errors than other children, suggesting a failure of emmetropization. One of the most intriguing studies of the past year and one certain to lead to follow-up studies reported that ambient room illumination at night in a child's first two years is associated with a higher prevalence of myopia than sleeping in darkness. Reports on the development of hyperopia showed that it is axial in nature, similar to myopia. The effects of spectacle interventions to correct refractive errors are still being debated, with recent evidence from children suggesting that lenses do not exacerbate myopia. Analyses of risk factors and numerous new screening procedures detect patients with strabismus for referral at a variety of sensitivity and specificity levels. Hyperopia and high AC/A ratios are most clearly associated as causal agents for esotropia and intermittent exotropia. However, the action of even these simple mechanisms is confounded by abnormal binocular fusion mechanisms and the inability of optical correction to align the eyes of many patients. Asymmetric optokinetic nystagmus, latent nystagmus, and dissociated vertical deviation appear to be linked to infantile esotropia from before its onset. But the way the mechanisms underlying these oculomotor anomalies are causally related to the onset of infantile esotropia remains a mystery.

A new objective digital computerized vision screening system

PURPOSE

Fewer than 40% of children in the crucial younger-than-4 age group are evaluated for visual problems by pediatricians. This is due to impracticality from either a clinical or practice efficiency standpoint. Current photoscreening methods require trained readers and suffer from significant subjectivity and interobserver variability. We report a cross-sectional, double-masked study using new digital imaging with objective, automated, computerized image analysis.

METHODS

Two-hundred six children aged 9 months to 16 years were prospectively studied in a University-based pediatric ophthalmology practice. Images were taken by volunteers with a modified digital camera which, when downloaded, were analyzed within 35 seconds by new image analysis software. The analysis was compared to a masked review of a complete pediatric ophthalmic exam.

RESULTS

Overall agreement between physician and the objective computerized analysis was 86.9%. Positive predictive value was 91%, sensitivity was 89%, and specificity was 83%.

CONCLUSIONS

This automated digital imaging screening system eliminates human bias and provides accurate and immediate results. The system requires no special expertise.

A survey of vision screening policy of preschool children in the United States

A state-by-state survey regarding preschool vision screening guidelines, policies, and procedures was conducted. Currently 34 states provide vision screening guidelines and 15 states require vision screening of at least some of their preschool-aged children. The Department of Public Health administers the programs in 26 states, the Department of Education in 13. A wide range of professional and lay personnel conduct preschool vision screenings, and nurses participate in the screening process in 22 states. Visual acuity is assessed in 30 states, eye alignment in 24 states, refractive error in eight states, and color vision in 10 states. A combination of screening tests is recommended in 24 states. Currently, 45 states do not require screening of all preschool children. Thus, although laws, guidelines, and recommendations exist in most states, many preschool-age children do not have access to vision screening programs.