Refractive Trends in Swedish Military Recruits

7/28/2019 Refractive Trends in Swedish Military Recruits

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D. Uhlin1

, S. Lutteman1

, J.A.M. Jennings2

, R.L. Brautaset1

1Unit o Optometry, Department o Clinical Science, Karolinska Institutet, Box 8056,104 20 Stockholm, Sweden and 2Faculty o Li e Science, University o Manchester,PO Box 88, Manchester M60 1QD, UK

AbstractPurpose: The aim o the study was to determine the prevalenceo re ractive errors in military recruits, with special re erence tomyopia. Methods: 651 male military recruits, 17-23 years o age, werere racted at Pliktverket in Nsby (a National Service Adminis-tration o fce near Stockholm, Sweden). The re ractive measu-rements were taken with a Topcon KR-7OOOP auto kerato-re ractometer during the initial health examination o NationalService recruits. Results: Out o the 651 recruits the prevalence o myopia ( -0.50DS) was 37.7% (i.e., both eyes being myopic). The mean re-ractive error was RE -0.47DS and LE -0.41DS. This di erence

was not statistically signifcant.Discussion:The prevalence o myopia in Swedish military recru-its has increased rom 8.9% to 37.7% and the mean re ractiveerror has changed rom +0.53DS to 0.44DS since the study o Strmberg (1936). However, the prevalence o myopia in these

present day recruits is lower than the 49.5% ound in 12-13 yearold Swedes (Villarreal et al., 2000).

Key words:myopia prevalence Swedish male military recruits

Refractive trends inSwedish Military recruits

SammanfattningBakgrund:Mlsttningen med studien var att underska preva-lensen av syn el hos mnstrande mn med okus p myopipre- valens. Metod: 651 vrnpliktiga i ldern 17 till 23 r blev underskta vidmnstring hos Pliktverket i Nsby utan r Stockholm. Mtnin-garna ut rdes med en Topcon autore raktor (KR-7000P) som delav deras hlsokontroll. Resultat:Av de 651 vrnpliktiga som undersktes ptr ades enmyopiprevalens ( -0.50DS) p 37,7%. Det genomsnittliga syn-elet var H 0,47DS och V 0,41D, en skillnad som inte varstatistisk signifkant.Diskussion: Myopiprevalensen hos mnstande mn i Sverigehar kat rn 8,9% til 37,7% och det genomsnittliga syn let harndrat sig rn +0,53D till 0,44DS sedan motsvarande studiegenom rdes av Strmberg (1936). Samtidigt ser man att myo-piprevalensen hos dagens mnstrande mn r lgre en myo-piprevalensen (49,5%) som hittades hos svenska 12-13 r gamla

barn (Villarreal et al., 2000).

Correspondence:Rune L. BrautasetUnit o OptometryDepartment o Clinical ScienceKarolinska InstitutetBox 8056S-104 20 StockholmSwedenFax: +46 (0)8 672 3846E-mail: [email protected]

Received: February 2008Revised form: November 2008

Accepted: December 2008

doi:10.5384/SJOVS.vol2i1p1 - ISSN: 1891-0890 Scandinavian Journal of Optometry and Visual Science Copyright Norwegian Association of Optometry

SJOVS, January 2009, Vol. 2, No. 1 - Article (in English)


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IntroductionThere is general agreement that the environment and geneticsinteract in the development o myopia (Adams and McBrien,1992; Chung et al., 1996; Cordain et al., 2002; Mutti et al., 1996;OHara and Nelson, 1997) and that some populations, parti-cularly in the Far East, are markedly predisposed to myopia

(Hosaka, 1988; Lin et al., 1988; Saw et al., 2005; Wong et al.,2000; Zhao et al., 2000), but there is also evidence o increasedprevalence o myopia in other parts o the world (Bar Dayan etal., 2005). The theory o myopia as an environmentally inducedphysiological adaptation to near work has lately been gaining more support (Adams and McBrien, 1992; Cordain et al., 2002;Flitcro t, 1998; Kinge and Midel art, 1994; Kinge et al., 1998,2000; Nyman 1998; Midel art, 1990; Midel art et al., 1992; Muttiet al., 2002; Saw et al., 2002; Williams et al., 2008), while theSydney Myopia study recently reported that near work was notassociated with concurrent myopia (Ip et al., 2007). From twinstudies evidence has been presented that indicates that myopiais 80-90% heritable (Hammond et al., 2001; Lyhne, et al., 2001),however, amily aggregation studies suggest lower heritability (Framingham O spring Eye Study Group, 1996). Furthermore,the observed large changes in prevalence over very ew gene-rations have again illustrated the importance o environmental

actors (Morgan and Rose, 2002). In general, recent research canbe summarized by saying that both environmental and geneticactors are o importance in the development o myopia, but thatit is still to be discovered how these actors interact in order toexplain the increase in myopia that can be seen in di erent parts

o the world. In the Nordic countries the prevalence o myopia is repor-ted to be approximately 30% (Fledelius, 1983; Fledelius,2000; Kinge et al., 1998; Midel art, 2004). A summary o Nor-dic studies into the prevalence o myopia can be ound inTable 1.

In 1936 Strmberg, based on subjective re raction, ound theprevalence o myopia in 2616 Swedish conscripts aged about 20 years to be 8.9%. Since the study o Strmberg (1936) no study has been conducted in Sweden in order to determine the prevalence o myopia in a population o similar age. The aim o the current study was to determine the prevalence o todaysSwedish army recruits and to compare the results with those o Strmberg (1936).

Table 1: Prevalence of myopia as found in the Nordic countries

Country

Norway

Denmark

Finland

Sweden

Prevalence of myopia

2.2%5.9%

50.3%35%

1%1.2%7.4%9.3%

28.6%10%9.5%

11-12%14.5%

13-14%32.6%50.0%

12%1.9%7.2%

21.8%14%

22.8%

49.7%19.5 - 25.3%

8.9%6.4%4.7%27%16%

37.7%

Age group

9 years12 years

Medical students20-25 years

7-8 years7-8 years

9-11 years9-11 years7-12 years

13-14 years13-14 years13-14 years17-23 years17-23 years17-23 years22-41 years

(median 26 years)14-15 years

7-8 years11-12 years14-15 years

12 years15 years

12-13 years18-19 years

20 years(all men)

20-35 years

17-23 years(all men)

Definition

?

-0.25 -0.50

-0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.25 -0.50

-0.5 -0.5

-0.25

-0.5?

-0.25 -0.75>-1.0

-0.25>-1.0 -0.5

Author

Holst & Tjland (1962)

Midelfart et al. (1992)Midelfart et al. (2004)

ster & Kjrgaard* (1964)Engbk* (1970)Johansen* (1950)Fledelius (1976)Jensen (1991)ster & Kjrgaard* (1964)Goldschmidt (1968)Engbk* (1983)Goldschmidt (1968)Fledelius (1980)Fledelius (1983)Fledelius (200)

Heinonen (1934)Laatikainen & Erkkil (1980)

Mntyjrvi (1983)

Villarreal et al. (2000)Lundgren (1954)Strmberg (1936)

Stenstrm (1947)

Present study




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Subjects and MethodsA total o 651 men aged between 17 and 23 years (mean age18 years) was examined. The ocular examination was anadditional and voluntary part o the initial health examina-tion or National Service recruits. The examination took placeat Pliktverket in Nsby (a National Service Administration

o ce near Stockholm, Sweden). All recruits enrolled over aone week period were examined consecutively, all recruitsaccepted to be part o the study and none o the enrolledrecruits were excluded. The recruits came rom the greaterStockholm area. O the 651 tested 98.5% were o Caucasianorigin. All subjects gave in ormed consent.

All subjects had their visual acuity measured with a 4 me-tre LogMar chart. The re ractive error was determined by useo a Topcon KR-7OOOP (auto kerato-re ractometer) withoutthe use o cycloplegics. As a sa eguard against proximal e -ects prior to the auto-re raction all subjects were asked toxate an acuity chart placed 4 metres away in order to relaxaccommodation.All statistics were per ormed using InStatTM (GraphPad, La Jolla, CA, USA) and OriginTM (Origin Lab, Northampton,MA, USA) statistical so tware. Comparison o the presentdata and the results o Strmberg (1936) was done using Chi-squared test. The range o re ractive errors could be conside-red normally distributed and the 95% con dence interval o the mean was constructed using the Student T-test.

ResultsClassi cation o re ractive error was based on sphericalequivalent (spherical value combined with hal the cylindervalue) and was divided into three groups: myopia ( -0.50D),hyperopia ( +0.50D), and emmetropia (+0.50D < sphericalequivalent +0.50D) the overall prevalence was 19.6% andright eye prevalence was 17.8%.Emmetropia:an overall prevalence o 42.7% with a 43.2% pre-valence in the right eye.The mean re ractive error or the right eye was -0.47D (0.14;0.95 con dence interval o the mean) and or the le t eye-0.41D (0.14; 0.95 con dence interval o the mean).

The highest re ractive errors were -8.25D and +6.50D. Thedistribution o re ractive errors can be seen in Figure 1.

DiscussionThe subject group examined in this study is similar to thegroup examined by Strmberg (1936) in that they are all male,o similar age, and predominantly Caucasian (98.5%). Thisimplies that the prevalence o myopia over a three-generationperiod (65 years) has increased rom 8.9% to 37.7% (p


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Refractive Trends in Swedish Military Recruits