Up

 

PhotoScreenerTM Studies

Screening for Amblyogenic Factors Using a Volunteer Lay Network and the MTI PhotoScreener

Initial Results from 15,000 Preschool Children in a Statewide Effort

Sean P. Donahue, MD, PhD, Tammy M. Johnson, MPH, Thomas C. Leonard-Martin, PhD, MPH

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.

Click here to view the full study. (PDF)
 

Photoscreening for Amblyogenic Factors

Wanda L. Ottar, OC(C),Comt:William E.Scott, MD; and Sandra I. Holgado, MD

ABSTRACT

Background: The Medical Technology, Inc. PhotoScreener™ is a new eccentric photoscreener that is being marketed as a device for the detection of amblyogenic factors in preverbal children. The purpose of this study was to evaluate the accuracy of the PhotoScreener™ in the target population of young, healthy children.

Methods: One thousand and three healthy children between the age of 6 months and 59 months were photoscreened with the PhotoScreener™ . Nine hundred and forty nine children were included in the study and their results were compared with a complete ophthalmologic examination with cycloplegia.

Results: The sensitivity of the PhotoScreener™ was determined to be 81.8% with a specificity of 90.6%. The overall agreement rate was 88.8%. The positive and negative predictive values were 68.9% and 95.2%, respectively. All cases of strabismus and media opacities were detected.

Conclusion: The PhotoScreener™ is an accurate and reliable device designed to detect amblyogenic factors in young children. The camera offers promise as a useful mass-screening tool.

INTRODUCTION

Amblyopia is a common childhood disorder affecting 3% to 5% of the population. 1,2 The need for early detection of amblyopia and amblyogenic factors is widely recognized. 3,4 However, most current vision screening methodologies are not effective in screening preverbal children.5

Interest has increased in photoscreening as a method for detecting amblyogenic factors in young children. The methodology is simple: a flash photograph of the subject's eyes is taken. The light reflected from the retina is analyzed to detect refractive errors, strabismus, and/or media opacities. Two types of photoscreeners based on the relationship between the flash source and the optical axis of the camera have been described. 6-11The on-axis system has a coaxial camera and flash source. The off-axis system has a flash source slightly off the optical axis of the camera. Several studies comparing the two systems have found that the off-axis system provides more information with fewer photographs and is better suited for non-cycloplegic refractive screening.6,12,14

An off-axis instant film photoscreener, The Medical Technology, Inc. PhotoScreener™, was commercially manufactured after several studies were conducted with the prototype, EyeCor camera.1, 5-17 The purpose of this study was to measure the sensitivity, specificity and accuracy of the PhotoScreener™ in detecting strabismus, media opacities, and refractive errors in a large population of healthy children between the ages of 6 months and 59 months.

MATERIAL AND CONSTRUCTION

Camera

The PhotoScreener™ was designed and tested to have the same sensitivity on model eye testing as its prototype, the Eyecor camera. The specifications of the Eyecor camera have been previously described.15-17 Some additional modifications were made, including automatic rotation of the flash and a sliding film that places both the horizontal and vertical photographs on the same instant photograph. A 9-D lens with a back focal distance of 5 inches results in a 1:1 magnification. Each photograph was examined for the presence of strabismus, media opacities, and refractive errors. The diagnosis was determined from examination of the photographs as discussed below (see procedure).

A pupil-crescent measurement tool supplied with the camera was used to measure the pupil and crescent sizes in all photographs. The measurement tool is designed with 3 mm through 9 mm offset openings and complete hole openings. Each template is marked with one-mm lines. A small millimeter ruler also is located along the side (Fig 1).


 
Figure 1: Pupil-crescent measurement tool.

Subjects

One thousand and three "healthy" children between the ages of 6 months and 59 months were examined. Approximately two thirds of the children were photoscreened during routine screening at Public Health and Women, Infants and Children's (WIC) clinics in Iowa and Illinois. The remaining one third were screened in the private offices of pediatricians in Iowa and Texas. Children with history of an eye problem or who had previously examined by an ophthalmic professional were excluded. Children with known systemic disease also were excluded. The gender distribution was 51% male and 49% female. Of the patients, 81.3% were Caucasian, 7.8% African American, 5.8% Hispanic, and 2.9% Asian.

Procedure

The purpose of the study was explained, and informed consent was obtained from the legal guardian of each subject. Each child was photographed by one of the authors (S.H or W.O) with the PhotoScreener™ in a darkened environment. Photographs were immediately retaken if they were unfocused or if they demonstrated poor subject fixation or a pupil size less than 4 mm. The camera is designed for measurement of the bright crescent to estimate the refractive error. The pupil and bright crescent size were measured to the nearest 0.5 mm with the pupil-crescent measurement tool included with the camera. Myopic crescents were located on the same side as the flash (superiorly and to the left) (Fig 2), and hyperopic crescents are located on the opposite side of the flash (inferiorly and to the right) (Fig 3). By comparing the difference in crescent size, anisomtropia (Fig 2) and stigmatism (Fig 3) can be detected. The size of the crescent is related to the amount of refractive error. A two mirrored system reverses the eyes so that the eye that is to the left is the patient's right eye and the eye that is to the right is the patient's left eye just as if the examiner were facing the patient. The measurements of each patient were documented and the photographs were scored based on the pre-determined photoscreening criteria (Table 1). Each photograph was graded (S.H.) in a masked fashion and identified by a code number prior to the ophthalmic examination. Inter-observer variability was not addressed.

A complete ophthalmic examination including a cover test, mobility evaluation, and pupil assessment was performed by a pediatric ophthalmologist (S.H.) or an orthoptist (W.O.) on each child. Two cyclopentolate drops were instilled 5 minutes apart in each child. Children under 12 months of age were given .5% cyclopentolate. All children 12 months or older were dilated with 1% cyclopentolate. If the child presented with dark irides, age-appropriate cyclopentolate combines with 2.5% phenylephrine was installed. Approximately 30 minutes after each installation, a cycloplegic refraction and fundus examination were performed by a pediatric ophthalmologist (S.H.). Criteria for clinical failure are listed in Table 2. The term failure is used to describe subjects who do not meet the established photoscreening or eye examination criteria. All children who failed the ophthalmic examination were counseled on the need to follow up treatment.

 

Figure 2: Photoscreening picture of a subject with a difference in crescent location between eyes. This is an example of anisometropia. Upper photograph right eye: 3.0-mm crescent in a 5-mm pupil; left eye: 3.0-mm hyperopic crescent in a 5.5-mm pupil. Lower photograph right eye: 3.0-mm myopic crescent in a 5.5-mm pupil; left eye: 1.0-mm hyperopic crescent in 6.0-mm pupil.

Figure 3: PhotoScreening picture of a subject with a difference in crescent size between the upper and lower photograph. This is an example of astigmatism. Upper photograph right eye 0.5-mm hyperopic crescent in a 6-mm pupil; left eye: 2.0-mm hyperopic crescent in a 6.0-mm pupil; lower photograph right eye: 3.0-mm hyperopic crescent in a 6.0-mm pupil; left eye: 4.5mm hyperopic crescent in a 6.0-mm pupil.

References

1. Atkinson J, Braddick OJ, Durden K. Et al. Screening for refractive errors in six to nine month old infants by photorefraction. Brit J Ophthalmol. 1984;68:105-112.
2. Hsu-Winges C, Hamer R, Norica A, et al. Polaroid photorefractive screening of infants. J Pediatr Ophthalmol Strabismus. 1989;26:254-260.
3. American Association for Pediatric Ophthalmology and Strabismus. Eye care for the children of America. J Pediatr Ophthalmol Strabismus. 1991; 28:64-67.
4. American Academy of Pediatrics Committee on Practice in Ambulatory Medicine. Vision screening and eye examination in children. Pediatrics. 1986;77:918-919.
5. Ehrlich MI, Reinecke RD Simons K. Preschool vision screening for amblyopia and strabismus: programs, methods, guidelines, 1983. Surv Ophthalmol. 1983;28:145-63.
6. Kennedy RA, Sheps SB. A comparison of photoscreening techniques for amblyogenic factors in children. Can J Ophthalmol. 1989;24:259-264.
7. Abramov I, Hainline L, Duckman R. Screening infant vision with paraxial photorefraction. Optom Vis Sci. 1990;67:538-545.
8. Bobier WR, Braddick OJ. Eccentric photorefraction: optical analysis and empirical measures. Amer J Opt Physiol Optics. 1985;62:614-620.
9. Kaakinen KA, Kaseva HO, Teir HH. Two-flash photorefraction in screening of amblyogenic refractive errors. Ophthalmology. 1987;94:1036-1042.
10. Deutsch J, Smellie T, Tovey J. Audiovis Media Med. 1990;13:124-128.
11. Atkinson J, Braddick O. The use of isotropic photorefraction for vision screening in infants. Acta Ophthalmol (Copenh). 1982;157(suppl):36-45.
12. Morgan K, Johnson WD. Clinical evaluation of commercial photorefractor. Arch Ophthalmol. 1987;105:1528-1531.
13. Hamer R, Norica A, Day S, et al. Comparison on-and off-axis photorefraction with cycloplegic retinoscopy in infants. J Pediatr Ophthalmol Strabismus. 1992;29:232-239.
14. Howland H, Braddick O, Atkinson J, et al. Optics of photorefraction. Orthogonal and isotropic methods. Trans Opt Soc Amer. 1983;73:1701-1708.
15. Freedman H, Preston K. Polaroid photoscreening for amblyogenic factors. An improved methodology. Ophthalmology. 1992;99:1785-1795.
16. Morris C, Kutschke P, Morris R, et al. Polaroid photoscreening for amblyogenic factors in high pathology and normal population groups. In press.
17. Drack A, Stewart S, Scott WE, et al. Photoscreening for amblyogenic factors in a preschool population. J Pediatr Ophthalmol Strabismus. In press.
18. Macpherson H, Braunstein J, LaRoche G. Utilizing basic screening principals in the design and evaluation of vision screening programs. American Orthoptics Journal. 1991; 41:110-121.
19. Day S, Norica A. Photographic detection of amblyogenic factors. Ophthalmology. 1986;93:25-28.
20. Kaakinen K, Renta-Kemppainen L. Screening of infants for strabismus and refractive errors with two-flash photorefraction with and without cycloplegia. Acta Ophthalmol (Copenh). 1986;64:578-582.
21. Morgan K, Johnson W. Clinical evaluation of a commercial photorefractor. Arch Ophthalmol. 1987;105:1528-1531.
22. Howland H, Howland B. Photorefraction: a technique for study of refractive state at a distance. J Opt Soc Am A. 1974;64:240-249.
23. Maino J, Cibis G, Cress T, et al. Non-cycloplegic versus cycloplegic retinoscopy in preschool children. Ann Ophthalmol. 1984; 16:880-882.
24. Mutti D, Zadnik K, Egashira S, et al. The effect of cycloplegia on measurements of the ocular components. Invest Ophthalmol Vis Sci. 1994;35:515-527.
25. Howland H, Dobson V, Sayles N. Accommodation in infants as measured by photorefraction. Vision Res. 1987;28:2141-2152.
26. Norcia A, Zadnik K, Day S. Photorefraction with a catadioptric lens: improvement on the method of Kaakinen. Acta Ophthalmol (Copenh). 1986;64:379-385.
27. Maslin K, Hope C. Photoscreening to detect potential amblyopia. Aust NZ J Ophthalmol. 1990;18:313-318.

 


100 North Rancho Road, Suite #1
Thousand Oaks, CA   91362
Phone (805)495-3937   Fax (805)373-9843
E-Mail

 

[ Home ] [ Up ] [ What is Agape? ] [ Agape Learning ] [ Agape Optometry ] [ Appointments ] [ Location & Hours ] [ Questionnaires ] [ Staff ] [ Payment Options ] [ Job Opportunities ] [ Privacy Practices ]