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Prevalence of refractive errors and incidence of myopia in Swedish schoolchildren
Linnaeus University, Faculty of Health and Life Sciences, Department of Medicine and Optometry.ORCID iD: 0000-0002-9970-3237
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Purpose

The aim of this thesis was to investigate the prevalence, incidence, and risk factors for myopia development in a cohort of Swedish schoolchildren. The specific goals were: - to recruit a cohort of children aged 8 to 16 years and to follow the cohort over a period of 24 months with regular study visits; - to investigate the predictive value of relative peripheral error and other optical parameters for the prevalence and incidence of myopia; - to determine and investigate the predictive value of genetic and environmental factors, and structural characteristics of the eye to the incidence of myopia.

Methods

This was a longitudinal study with a follow-up period of 2-years conducted at Linnaeus University in Kalmar. All participants underwent eye examinations and completed questionnaires at regular intervals during the follow-up period. Data analysis was performed assuming hypotheses such as: - myopia development is associated with genetic factors and environmental factors (Papers I and IV); - changes in refractive error over time are explained by multiple genetic and environmental factors (Paper IV) - instruments with different measurement principles can lead to different refraction results (Paper II); - there is a relationship between refractive error and the characteristics of the choroid (Exploratory study, not published) and the characteristics of the microvasculature of the retina (Paper III).

Results

A total of 128 children (70 females and 58 males) participated in this study with mean age of 12.0 years (SD=2.4). Paper I: based on cycloplegic SER of the right eye, the distribution of refractive errors was: hyperopia 48.0% (CI95=38.8-56.7), emmetropia 42.0% (CI95=33.5-51.2) and myopia 10.0%. (CI95=4.4-14.9). Participants with two myopic parents had higher myopia and increased axial length than those with one or no myopic parents. Paper II: The Shin-Nippon was 0.30 D more hyperopic than COAS-HD VR at 2.5-mm pupil and 0.50 D more hyperopic than COAS-HD VR at 5-mm pupil for central refraction. Paper III: The sample included 86 out of the 128 participants, 51 (59%) females. The area of the foveal avascular zone (AFAZ) was correlated with central vessel density, perfusion, foveal thickness and with fovea-to-macula thickness ratio. Paper IV: The cumulative incidence of myopia during the two-years was 5.5%, incidence rate of myopia was 3.2 cases per 100 person-years. Cox regression revealed that the probability of myopic shift reduced with “age” and increased with “axial length/corneal-curvature ratio”. Myopic children at the baseline and children with two myopic parents showed a significant faster-paced SER change over time.

Conclusion

The prevalence and incidence of myopia in Sweden was lower than expected when compared with countries in East Asia. Genetic factors such as parental myopia remains a critical factor to consider when predicting myopia onset and progression. Children born full-term and visual acuity within the normal range can have very different retinal microvasculature at the centre of the macula that may influence refractive error development. Future studies are necessary to find out possible relationships between vasculature, structural changes and refractive error development. In addition, more studies involving children from different ethnicities and incorporating longer follow-up period are necessary to increase our understanding of the incidence of myopia in Swedish schoolchildren.

Abstract [sv]

Syfte

Syftet med denna avhandling var att undersöka prevalensen, incidensen och riskfaktorer för myopiutveckling hos svenska skolbarn. De specifika målen var att (1) rekrytera barn i åldrarna 8 till 16 år och följa de under en 24 månaders period med regelbundna studiebesök, (2) att undersöka det prediktiva värdet för det relativa perifera synfelet och andra optiska parametrar för prevalensen och incidensen av myopi, (3) att avgöra och undersöka det prediktiva värdet för genetiska och miljömässiga faktorer, samt ögats strukturella egenskaper hos ögat i förhållande till incidensen av myopi.

Metoder

Detta var en longitudinell studie med en uppföljningstid på 2 år och genomfördes vid Linnéuniversitetet i Kalmar. Under uppföljningstiden genomgick alla deltagare synundersökningar och fyllde i frågeformulär med jämna mellanrum. Dataanalys utfördes med antagande av hypoteser som: (1) myopiutveckling är associerad med genetiska faktorer och miljöfaktorer (Artikel I och IV), (2) förändringar av synfel som sker över tid förklaras av flera genetiska och miljömässiga faktorer (Artikel IV), (3) instrument med olika mätprinciper kan leda till olika refraktionsresultat (Artikel II), det finns ett samband mellan synfel och åderhinnans egenskaper (explanativ studie, ej publicerad) samt (4) ett samband mellan synfel och egenskaperna hos näthinnans mikrovaskulatur (Artikel III).

Resultat

Totalt deltog 128 barn (70 flickor och 58 pojkar) i denna studie med en medelålder på 12,0 år (SD=2,4). Artikel I: Baserat på höger ögats cykloplegiska sfäriska ekvivalent refraktion (SER) var fördelningen av synfel: hyperopi 48,0% (CI95=38,8–56,7), emmetropi 42,0% (CI95=33,5–51,2) och myopi 10,0% (CI95=4,4–14,9). Deltagare med två myopa föräldrar hade högre myopi och ökad axiallängd jämfört med de som hade en eller inga myopa föräldrar. Artikel II: Shin-Nippon visade 0,30 D mer hyperopi än COAS-HD VR med 2,5 mm pupilldiameter och 0,50 D mer hyperopi än COAS-HD VR med 5 mm pupilldiameter för centrala refraktionen. Artikel III: Urvalet bestod av 86 av de 128 deltagande, 51 (59 %) flickor. Arean av den foveala avaskulära zonen (AFAZ) korrelerades med central kärldensitet, perfusion, foveal tjocklek och med fovea-till-makula tjockleksförhållande. Artikel IV: Under de två åren var den kumulativa incidensen av myopi 5,5 %, incidensfrekvensen av myopi 3,2 fall per 100 personår. Cox-regression visade att sannolikheten för att en myopisk förändring ska ske minskade med "åldern" och ökade med "axiell längd/korneal-krökningsförhållande". Myopa barn vid studiens start och barn med två myopa föräldrar visade en signifikant snabbare SER-förändring över tiden.

Slutsats

Prevalensen och incidensen av myopi var lägre än förväntat i Sverige jämfört med länder i Östasien. Genetiska faktorer som myopi hos föräldrar är fortfarande en kritisk faktor att ta hänsyn till när man förutsäger debut och progression av myopi. Barn som är fullgångna och har en synskärpa inom normalområdet kan ha mycket varierande retinal mikrovaskulatur i makula som sin tur kan påverka utvecklingen av synfel. Framtida studier är nödvändiga för att ta reda på möjliga samband mellan vaskulatur, strukturella förändringar och utveckling av synfel. Dessutom är fler studier som involverar barn från olika etniciteter och som inkluderar längre uppföljningsperiod nödvändiga för att öka vår förståelse och kunskap för förekomsten av myopi hos svenska skolbarn

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2022. , p. 172
Series
Linnaeus University Dissertations ; 457
Keywords [en]
Refractive error, myopia, prevalence, incidence, risk factors, children, fovea, macula, autorefractor, aberrometer
Keywords [sv]
synfel, refraktion, myopi, barn, prevalens, incidens, riskfaktorer, fovea, makula, autorefractor, aberrometer
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
URN: urn:nbn:se:lnu:diva-115701ISBN: 9789189709218 (print)ISBN: 9789189709225 (electronic)OAI: oai:DiVA.org:lnu-115701DiVA, id: diva2:1686390
Public defence
2022-09-02, Room Lapis, Hus Vita, Kalmar and via zoom, Pedalstråket 11, 392 31 Kalmar, Kalmar, 09:00 (English)
Opponent
Supervisors
Available from: 2022-08-12 Created: 2022-08-09 Last updated: 2024-10-10Bibliographically approved
List of papers
1. Refractive error, axial length, environmental and hereditary factors associated with myopia in Swedish children
Open this publication in new window or tab >>Refractive error, axial length, environmental and hereditary factors associated with myopia in Swedish children
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2021 (English)In: Clinical and experimental optometry, ISSN 0816-4622, E-ISSN 1444-0938, Vol. 104, no 5, p. 595-601Article in journal (Refereed) Published
Abstract [en]

Clinical relevance: Investigation of refractive errors amongst Swedish schoolchildren will help identify risk factors associated with myopia development.Background: Genetic and hereditary aspects have been linked with the development of myopia. Nevertheless, in the case of ‘school myopia’ some authors suggest that environmental factors may affect gene expression, causing school myopia to soar. Additional understanding about which environmental factors play a relevant role can be gained by studying refractive errors in countries like Sweden, where prevalence of myopia is expected to be low.Methods: Swedish schoolchildren aged 8-16 years were invited to participate. Participants underwent an eye examination, including cycloplegic refraction and axial length (AL) measurements. Predictors such as time spent in near work, outdoor activities and parental myopia were obtained using a questionnaire. Myopia was defined as spherical equivalent refraction (SER) ≤ −0.50D and hyperopia as SER ≥ +0.75D.Results: A total of 128 children (70 females and 58 males) participated in this study with mean age of 12.0 years (SD = 2.4). Based on cycloplegic SER of the right eye, the distribution of refractive errors was: hyperopia 48.0% (CI95 = 38.8-56.7), emmetropia 42.0% (CI95 = 33.5-51.2) and myopia 10.0%. (CI95 = 4.4-14.9). The mean AL was 23.1 mm (SD = 0.86), there was a correlation between SER and AL, r = −0.65 (p < 0.001). Participants with two myopic parents had higher myopia and increased axial length than those with one or no myopic parents. The mean time spent in near work, outside of school, was 5.3 hours-per-day (SD = 3.1), and mean outdoor time reported was 2.6 hours-per-day (SD = 2.2) for all the participants. The time spent in near work and outdoor time were different for different refractive error categories.Conclusion: The prevalence of myopia amongst Swedish schoolchildren is low. Hereditary and environmental factors are associated with refractive error categories. Further studies with this sample are warranted to investigate how refractive errors and environmental factors interact over time.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2021
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-101455 (URN)10.1080/08164622.2021.1878833 (DOI)000624746100001 ()33689658 (PubMedID)2-s2.0-85102313065 (Scopus ID)2021 (Local ID)2021 (Archive number)2021 (OAI)
Available from: 2021-03-03 Created: 2021-03-03 Last updated: 2024-10-10Bibliographically approved
2. Comparison of an open view autorefractor with an open view aberrometer in determining peripheral refraction in children
Open this publication in new window or tab >>Comparison of an open view autorefractor with an open view aberrometer in determining peripheral refraction in children
2023 (English)In: Journal of Optometry, ISSN 1888-4296, Vol. 16, no 1, p. 20-29Article in journal (Refereed) Published
Abstract [en]

Purpose

The aim of this study was to compare central and peripheral refraction using an open view Shin-Nippon NVision-K 5001 autorefractor and an open view COAS-HD VR aberrometer in young children.

Methods

Cycloplegic central and peripheral autorefraction was measured in the right eye of 123 children aged 8 to 16 years. Three measurements each were obtained with both Shin-Nippon NVision-K 5001 autorefractor and COAS-HD VR aberrometer along the horizontal visual field up to 30° (nasal and temporal) in 10° steps. The refraction from the autorefractor was compared with aberrometer refraction for pupil analysis diameters of 2.5-mm and 5.0-mm.

Results

The Shin-Nippon was 0.30 D more hyperopic than COAS-HD VR at 2.5-mm pupil and 0.50 D more hyperopic than COAS-HD VR at 5-mm pupil for central refraction. For both pupil sizes, the 95% limits of agreement were approximately 0.50 D for central refraction, and limits were wider in the nasal visual field compared to the temporal visual field. The mean difference for both J0 and J45 were within 0.15 D and the 95% limits of agreement within 0.90 D across the horizontal visual field.

Conclusion

Defocus components were similar between the Shin-Nippon autorefractor and the COAS-HD VR aberrometer with a 2.5-mm pupil for most visual field angles. However, there was a significant difference in defocus component between the Shin-Nippon autorefractor and the COAS-HD VR aberrometer with a 5.0-mm pupil, wherein the autorefractor measured more hyperopia. The astigmatic components J0 and J45 were similar between instruments for both central and peripheral refraction.

Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-109244 (URN)10.1016/j.optom.2021.12.002 (DOI)000917490300001 ()2-s2.0-85122570954 (Scopus ID)
Available from: 2022-01-14 Created: 2022-01-14 Last updated: 2025-02-18Bibliographically approved
3. All retinas are not created equal: Fovea‐to‐macula thickness ratio and foveal microvasculature in healthy young children
Open this publication in new window or tab >>All retinas are not created equal: Fovea‐to‐macula thickness ratio and foveal microvasculature in healthy young children
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2022 (English)In: Ophthalmic & physiological optics, ISSN 0275-5408, E-ISSN 1475-1313, Vol. 42, no 3, p. 644-652Article in journal (Refereed) Published
Abstract [en]

Purpose: Markers for the relationships between structural and microvasculature measures given by optical coherence tomography angiography are necessary to increase the diagnostic and prognostic value of this technique. The aim of this study was to investigate relationships between structural and microvasculature measures around the fovea in healthy eyes of healthy children.

Methods: Observational cross-sectional study involving children aged 8–17 years, born at full-term, with no eye disease. The better of two 3 × 3 mm macular scans obtained with a Cirrus 5000HD-OCT was analysed. Images were corrected for lateral magnification errors. Vessel density and perfusion were measured with ImageJ/Fiji software for the superficial capillary plexus. Structural measures including foveal and macular thicknesses were performed manually.

Results: The sample included 86 participants, 51 (59%) females. Mean age was 12.4 years (SD = 2.5); mean best-corrected acuity was −0.10 logMAR (SD = 0.09); mean refractive error was +0.59 D (SD = 1.3) and mean axial length was 23.1 mm (SD = 0.86). Mean area of the foveal avascular zone (AFAZ) was 0.20 mm2 (SD = 0.88); median fovea-to-macula thickness ratio (FMTR) was 0.63 (IQR = 0.08); mean central vessel density was 12.42 mm−1 (SD = 2.78) and mean central perfusion was 38.66% (SD = 3.83). AFAZ was correlated with central vessel density (p < 0.001), perfusion (p < 0.001), foveal thickness (p < 0.001) and FMTR (p < 0.001). Central vessel density was correlated with foveal thickness (p < 0.001) and FMTR, (p = 0.01). Central perfusion was correlated with foveal thickness (p < 0.001) and FMTR, (p = 0.003).

Conclusion: In this study, foveal thickness, FMTR and foveal microvasculature measurements were correlated. Clinicians need to be aware that shallow foveal pits and persistent foveal microvasculature are likely to occur in optical coherence tomography angiography images. In healthy eyes from healthy children, an atypical high FMTR and a small AFAZ may be associated with incomplete foveal development. The mechanism and functional implications of this remain unknown.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
children, fovea, foveal avascular zone, foveal pit, optical coherence tomography angiography
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-110407 (URN)10.1111/opo.12958 (DOI)000754581800001 ()35156728 (PubMedID)2-s2.0-85124530607 (Scopus ID)
Available from: 2022-02-16 Created: 2022-02-16 Last updated: 2024-10-10Bibliographically approved

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