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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 112  |  Issue : 3  |  Page : 99-103

Photorefraction vision screening: value, constancy and credibility


1 Ophthalmology Department, Aswan University, Tingar, Egypt
2 Ophthalmology Department, Fayoum University, Fayoum, Egypt
3 Public Health and Community Medicine Department, Menofia University, Shebeen El-Kom, Egypt

Date of Submission15-Jun-2019
Date of Acceptance21-Aug-2019
Date of Web Publication25-Sep-2019

Correspondence Address:
FRCSEd, MD Ahmed F Gabr
19 Saif El-Dawla St Tanta, 31111
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_29_19

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  Abstract 

Background The purpose of this study was to compare photorefraction using Plusoptix vision screening with that of standard cycloplegic refraction, to detect variability between different observers.
Patients and methods In this prospective comparative study, the right eyes of 203 children were included. Refraction was performed for each child using Plusoptix photorefraction screener by two separate observers. Under the effect of cyclopentolate eye drops, retinoscopic cyclorefraction was performed for those under 4 years of age, and cyclorefraction using autorefractometer was performed for those 4 years or older.
Results In this study, 203 patients with 203 eyes were included, 110 (54.2%) of them were boys and 93 (45.8%) were girls. The mean age of the children was 6.61±4.49 years (range from 4 months to 16 years), and 74 (36.5%) of them were less than 4 years of age and 129 (63.5%) at least 4 years of age. There was no significant difference between the two observers, as regards mean spherical equivalent (+0.52±1.54 D with range of −3.8 to +5.38 for observer 1 and 0.540±1.63 D with range of −3.8 to +4.8 for observer 2). In all age groups, there was no significant difference between photorefraction results and the final objective refraction, as regards mean spherical equivalent (0.540±1.62 and 0.549±1.62 D, respectively). Myopic shift was noted with higher refractive errors.
Conclusion Compared with standard cycloplegic refraction, photorefraction using Plusoptix screener was found to be a valuable and reproducible method in spite of the tendency to myopic shift at higher refractive errors in children.

Keywords: amblyopia, cycloplegic refraction, myopic shift, photorefraction, presented-atThis study was presented as an oral presentation in the 36th ESCRS, Vienna, September 2018


How to cite this article:
Gabr AF, Nassef MA, Soliman SS. Photorefraction vision screening: value, constancy and credibility. J Egypt Ophthalmol Soc 2019;112:99-103

How to cite this URL:
Gabr AF, Nassef MA, Soliman SS. Photorefraction vision screening: value, constancy and credibility. J Egypt Ophthalmol Soc [serial online] 2019 [cited 2019 Oct 21];112:99-103. Available from: http://www.jeos.eg.net/text.asp?2019/112/3/99/267825


  Introduction Top


Screening using eccentric infrared photorefraction offers a useful tool, particularly in uncooperative children. Both eyes can be evaluated simultaneously without cycloplegia, with the coverage of a reasonable range of refractive errors in a relatively short duration [1],[2].

Some investigators expressed their concern about the accuracy of the procedure [3] and its affection by the use of universal defocus calibration factor by commercially available photorefractors [4].

This study intended to compare photorefraction using Plusoptix vision screening with standard cycloplegic refraction, to detect variability between different observers and to detect the existence of overestimation or underestimation of the measured refractive errors in children of mixed ethnicity.


  Patients and methods Top


In this prospective comparative randomized study, children attending the outpatient clinic of the ophthalmology department for vision checkup or suspicion of strabismus were included. Children with a history of previous ocular trauma, ocular surgeries or those with media opacities were excluded. Of the 221 children included, 203 (91.85%) of them could be tested by both photorefraction and cyclorefraction, and the data were submitted for statistical analysis.

Following the obtaining of informed consents, the 203 children included were exposed to full ocular examination and photorefraction by the first observer using Plusoptix A12R (Plusoptix GmbH, Nuremberg, Germany) without cycloplegia. Refraction was subsequently repeated using Plusoptix by the second observer. In the case binocular photorefraction was not achievable, monocular photorefraction was then used (as in cases of misalignment between both eyes).

Cycloplegic refraction using cyclopentolate 0.5% eye drops (Cycloplejico; Alcon Cusi, S.A. El Masnou, Barcelona, Spain) was then performed for all included children as follows: retinoscopic cyclorefraction for children under the age of 4 years or cycloautorefraction using Topcon autorefractometer (KR-800; Topcon Corporation, Tokyo, Japan) in children of at least 4 years of age. Thereafter, objective refraction was performed for each child, and the right eyes were randomly selected for statistical analysis, and the results were compared. For children aged more than 8 years and having no deviation, minor subjective refinements of prescription were performed, but only objective refraction was included in the evaluation.

Study protocols were all approved by the Institutional Review Board and followed the tents of the Declaration of Helsinki. Informed consents were obtained from parents or guardians of all included children after full explanation of the procedure. Confidentiality of all data was ensured at every step of the study.

Statistical methods of data analysis

Data were statistically described in terms of mean, SD, median, range and interquartile range when appropriate. Comparison between study groups was carried out using the Mann–Whitney test with P values less than 0.05 being considered statistically significant. As this study comprised continuous numerical (measurable) data, intraclass correlation coefficient (ICC) or Pearson correlation was used to express the validity of data between different groups. All statistical calculations were carried out using the computer program statistical package for the social sciences (SPSS Inc., Chicago, Illinois, USA) version 15 for Microsoft Windows.


  Results Top


Refraction using Plusoptix could be obtained in 203 of the 221 (91.85%) children tested. Causes of failure to complete the assessment were uncooperation and inattentiveness in eight, out of range refractive errors in five, deep amblyopia in three and large strabismus angle in two children. The mean age of the included children was 6.61±4.49 years (range from 4 months to 16 years); 74 (36.5%) of them were less than 4 years, and 129 (63.5%) were at least 4 years old.

No significant difference was found between photorefraction results of the first and second observers as regards the mean spherical equivalent (SE), vertical astigmatism (J0) and oblique astigmatism (J45) for the whole study group. ICC average measure of 0.97 (P<0.001) with a mean difference between the two observers for SE was −0.01 (−0.08 to 0.05) ([Table 1]).
Table 1 Comparison of photorefraction results between observer 1 and observer 2 among the whole group

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Moreover, there was no significant disparity between photorefraction results obtained by the second observer (the main observer) and the final cycloplegic refraction for the entire cohort of children as regards SE, J0 and J45 ([Table 2]).
Table 2 Comparison between results of photorefraction by the second observer and cycloplegic refraction among the whole group

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In children less than 4 years of age (N=74), there was no significant difference between photorefraction results and retinoscopic cyclorefraction as regards the mean SE and oblique astigmatic vector (J45). While a slightly significant difference in the vertical astigmatism vector (J0) was observed between the two observations (P=0.032), ICC was found to measure 0.97 (P<0.001), with mean difference between the two observations for SE being −0.006 (−0.10 to 0.08) ([Table 3]).
Table 3 Comparison between photorefraction results of observer 2 and retinoscopic cyclorefraction in children less than 4 years of age

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In children at least 4 years of age, there was no significant difference between photorefraction results and autocyclorefraction as regards the mean SE and vertical and oblique astigmatism. ICC average measure 0.97 (P<0.001) with mean difference between the two observations for SE was −0.02 (−0.12 to 0.07) ([Table 4]).
Table 4 Comparison between photorefraction results of observer 2 and cycloplegic autorefraction in patients of at least 4 years of age with regard to mean spherical equivalent and astigmatism

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Myopic shift (hyperopic underestimation) was found particularly with higher refractive errors but was found nonsignificant in the whole group ([Figure 1]). It was more prominent in the younger age group (>4 years old), compared with older children (≥4 years old) with high significance.
Figure 1 Myopic shift in mean subjective (cycloplegic) refraction compared with Plusoptix mean refractive spherical error for the whole group.

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  Discussion Top


While cycloplegic refraction remains the gold standard for detecting refractive errors, the main cause of amblyopia in children [5], photorefractor vision screeners provide a refractive estimate and allow detection of risk factors for amblyopia even before its development [6].

In this study, the comparison of cycloplegic refraction and photorefraction was carried out. The correlation between both techniques was reported in a community of mixed ethnicity to inspect the applicability of an universal program.

In this study, refraction could not be obtained in 18 (8.15%) children, generally due to uncooperation of children and high refractive errors. Other investigators reported failure to complete photorefraction mainly due to uncooperation of the investigated children, which ranged from 2.2 to 16% [7],[8],[9].

The mean age of the included children was 6.61±4.49 years (range from 4 months to 16 years); 74 (36.5%) of them were less than 4 years of age, and 129 (63.5%) of at least 4 years of age. This range of age was comparable to most of the published studies on photorefraction (ranging from 6 months to 14.1 years), allowing appropriate comparison with them [10],[11],[12],[13].

No interobserver difference was noted between the two observers when using photorefraction, and their results were found to be nearly identical. This finding indicates the repeatability of photorefraction when used as a screening tool, as supported by a previous report [11].

Comparable refraction results were obtained when using phororefraction and cyclorefraction in the whole study group (203 eyes) as regards SE and astigmatism. This agreement was universal between photorefraction and autocyclorefraction in children of at least 4 years of age and almost so with retinoscopic cyclorefraction in children less than 4 years of age. Many investigators agreed with these results and found overall agreement between photorefraction and cycloautorefraction to be over 81%; they reported photorefraction as an accurate and repeatable method for measurement of refractive errors, particularly for myopia and astigmatism [8],[14],[15],[16]. Moreover, Paff et al. [17] stated that Plusoptix has high sensitivity for the detection of myopia, astigmatism, and anisometropia compared with cycloplegic retinoscopy. In contrast, a statistically significant difference in SE values when using Plusoptix S04 and cycloplegic retinoscopy was reported by others [3], and Plusoptix was condemned as a limited method that could not detect the exact values in those cases with high hypermetropia or high myopia [18].

Myopic shift (hyperopic underestimation) was encountered with the higher degrees of ametropia, particularly in children less than 4 years of age. This could be expected due to partially uncontrolled accommodation in the younger age group, as measurement was usually carried out at 1 meter distance, without the use of cycloplegic eye drops, stimulating about one diopter of accommodation [10],[11],[19]. Despite the inclusion of corrective value for the anticipated accommodation in the software of new photorefractors, hyperopic underestimation was still encountered more with higher degrees of hypermetropia, and this was in agreement with the findings of recent investigators [3],[16],[18],[20],[21].

Although some investigators declared that universal defocus calibration factor used in the calculation of refractive errors by photoscreeners such as Plusoptix is originally obtained from the Caucasian population and this can affect their use to evaluate children from other ethnicities [22],[23], no significant differences between the results of this study (carried out in mixed ethnicity populations, mainly Africans) and those of previous studies obtained from other populations of different ethnic origins were found, and using photorefraction with universal defocus calibration factor showed no effect on the refractive power estimation [7],[8],[9],[12],[16],[24].


  Conclusion Top


Compared with standard cycloplegic refraction, photorefraction using Plusoptix screener was found to be a valuable and reproducible method in spite of the tendency to mild myopic shift at higher refractive errors in children in a community of mixed ethnicity.

Acknowledgements

The research was funded by the resources of the Ophthalmology Department, Faculty of Medicine, Aswan University.

The authors acknowledge the staff members of the Ophthalmology Department, Aswan University Hospital, and Ibn Sina Eye Center, Tanta, Egypt, for their technical help and support.

Ahmed F. Gabr contributed to the concept, design, and definition of intellectual content of this study. He also contributed to the literature search, data acquisition, manuscript preparation, and manuscript editing. Mohamed A. Nassef contributed to the design, the definition of intellectual content of the study, the collection of data, manuscript editing and manuscript review. Shaimaa S. Soliman was involved in contribution to the intellectual content of study, data analysis, statistical analysis, manuscript editing and manuscript review. The manuscript has been read and approved by all the authors; the requirements for authorship have been met; and each author believes that the manuscript represents honest work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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[PUBMED]  [Full text]  
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Paff T, Oudesluys-Murphy AM, Wolterbeek R, Swart-van den Berg M, de Nie JM, Tijssen E et al. Screening for refractive errors in children: the Plusoptix S08 and the Retinomax K-plus2 performed by a lay screener compared to cycloplegic retinoscopy. J AAPOS 2010; 14:478–483.  Back to cited text no. 17
    
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