대한안과학회지 2017 년제 58 권제 8 호 J Korean Ophthalmol Soc 2017;58(8):911-915 ISSN 0378-6471 (Print) ISSN 2092-9374 (Online) https://doi.org/10.3341/jkos.2017.58.8.911 Original Article 한국인의각막전면, 후면난시축의분포와연령에따른변화 Age-related Changes in Anterior, Posterior Corneal Astigmatism in a Korean Population 심윤섭 양순원 박율리 나경선 김현승 Yoon Seob Sim, MD, Soon Won Yang, MD, Yu Li Park, MD, Kyung Sun Na, MD, PhD, Hyun Seung Kim, MD, PhD 가톨릭대학교의과대학여의도성모병원안과및시과학교실 Department of Ophthalmology and Visual Science, Yeouido St. Mary s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea Purpose: To evaluate age-related changes in anterior and posterior corneal astigmatism in Koreans. Methods: The anterior and posterior corneal astigmatisms of 160 subjects with age ranging from 11 to 92 years, none of whom experienced any complications, were measured with a rotating Scheimpflug camera (Pentacam ). Using this data, the changing proportions of with-the-rule to against-the-rule and changing tendency of anterior and posterior corneal astigmatisms with age were evaluated using polar value analysis according to the Naeser method. Results: For the anterior cornea, the proportion of with-the-rule astigmatisms decreased with age (p < 0.0001). On the other hand, for the posterior cornea, the proportion of against-the-rule astigmatisms decreased with age (p = 0.012). In the polar value analysis, there was a trend toward against-the-rule astigmatism associated with increasing age for the anterior cornea (p < 0.0001) and toward with-the-rule astigmatism for the posterior cornea (p < 0.0001). Conclusions: In previous studies, the anterior corneal surface shifted from with-the-rule to against-the-rule astigmatism with increasing age, whereas the posterior corneal surface remained as against-the-rule astigmatism in most cases. But, our results showed that the proportion of against-the-rule astigmatisms of the posterior cornea decreased with age. Thus, evaluation of posterior corneal astigmatisms should be performed before cataract surgery in old patients, especially when using a multifocal or toric intraocular lens. J Korean Ophthalmol Soc 2017;58(8):911-915 Keywords: Astigmatism, Cataract surgery, Pentacam, Toric intraocular lens 각막난시는각막의각경선의굴절력이서로달라망막황반에선명한상을맺지못하고두개의초선을형성하게되는것으로, 1 이를측정하기위한방법으로는자동각막굴 Received: 2017. 5. 11. Revised: 2017. 7. 5. Accepted: 2017. 7. 25. Address reprint requests to Hyun Seung Kim, MD, PhD Department of Ophthalmology, The Catholic University of Korea Yeouido St. Mary s Hospital, #10 63-ro, Yeongdeungpo-gu, Seoul 07345, Korea Tel: 82-2-3779-1243, Fax: 82-2-761-6869 E-mail: Sara514@catholic.ac.kr * Conflicts of Interest: The authors have no conflicts to disclose. 절계, IOL master (Carl Zeiss Meditec AG, Jena, Germany), 각막지형도등이있다. 자동각막굴절계는각막중심의 3.0 mm 부위의점들을통하여, IOL Master 는각막중심의 2.5 mm 부위의 6점을통하여, 각막지형도는각막전체에서수천개의점을통하여각막난시를측정하게된다. 2 이중세극등현미경의원리를이용한각막지형도는다른검사와달리각막후면난시를측정할수있는데, 백내장수술시수술후잔여난시를줄이기위해각막후면난시를고려해야한다는연구결과 3-5 가발표되면서최근중요성이대두되고있다. 각막난시의축은연령이증가함에따라직난시에서도난시로변화하는경향을보인다고알려져있다. 1,3,4,6,7 그러 c2017 The Korean Ophthalmological Society This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 911
- 대한안과학회지 2017 년제 58 권제 8 호 - 나이는대부분각막곡률계로측정한각막전면난시를분석하여얻어진결과들로각막후면난시를반영하지못했다는제한점이있다. 고령화사회로들어서면서특히국내에서고령의환자가많아지고있고, 난시교정용인공수정체를이용한백내장수술및부분층각막이식수술이증가하는등각막후면난시에대한관심이증가하고있기에본연구를통해한국인에서연령증가에따른각막전면및후면난시의변화를알아보고자하였다. 대상과방법 2014년 1월부터 2015년 8월까지본원안과외래에내원한환자 160명중 160안 ( 우안 ) 을대상으로후향적연구를진행하였다. 본연구는헬싱키선언에입각한가톨릭대학교의학연구윤리심의위원회의승인아래진행되었다. 11세부터 80세이상까지 10세간격의 8개의연령군으로나누었고, 한군당 20안씩포함하였다. 각막질환, 눈꺼풀질환, 안와및결막질환등각막난시에영향을줄수있는질환이동반된경우, 각막이식수술, 굴절교정수술, 녹내장수술등을받은경우는연구대상에서제외하였다. Pentacam (Oculus, Wetzlar, Germany) 은 360 로카메라가회전하는샤임플러그 (Scheimpflug) 사진기원리를이용하여 2초가량의스캔을통해얻은화상으로각막전, 후면의지형도를구하게되며이를통해각막전, 후면의각막수차를구할수있다. 8 따라서본연구에서는 Pentacam 을이용하여각막전면및후면난시를측정하였고, 각막곡률의가파른축이 90 ± 30 에위치한경우는직난시군으로, 각막곡률의가파른축이 180 ± 30 에위치한경우는도난시군으로, 그외는사난시군으로정의하였다. 9 단, 후면난시의경우렌즈굴절력이음의부호인관계로각막곡률의가파른축이 90 ± 30 에위치한경우를도난시군으로, 180 ± 30 에위치한경우를직난시군으로정의하였다. 7 연령증가에따른각막난시의변화를분석하기위해 Naeser 공식을이용하여굴절구면값 (Sph, Cyl, A) 을극값으로변형하였다. 9 여기서극값 (in diopter) 은 Cyl (Sin 2 A Cos 2 A) 로정의되며양의값인경우직난시, 음의값인경우도난시임을의미한다. 10 통계분석은 SPSS 24.0 (IBM Corp., Armonk, NY, USA) 을이용하였으며연령증가에따른각막전면난시에서직난시비율의감소여부, 각막후면난시에서도난시비율의증가여부를선형대선형결합을이용하여분석하였으며, 각각의상관성을선형회귀분석을이용하여분석하였고, p 값이 0.05 미만인경우통계학적인의의가있는것으로판 단하였다. 결 과 75명의남성과 85명의여성을대상으로하였으며전체평균나이는 49.11 ± 23.12세 (11-92세) 였다 (Table 1). 각막전면난시는연령이증가함에따라통계적으로유의하게직난시의비율이감소하는경향 (p<0.0001) 을보였으며, 각막후면난시는연령이증가함에따라통계적으로유의하게도난시의비율이감소하는경향 (p=0.012) 을보였다 (Fig. 1). 극값을이용하여분석한결과, 연령이증가함에따라각막전면난시는도난시로변화하는경향을보였고 10년간평균변화량은 0.356D였다 (p<0.0001) (Fig. 2). 반면각막후면난시는직난시로변화하는경향을보였고 10년간평균변화량은 0.033D였다 (p<0.0001). Table 1. The age and sex distributions of subjects Age (years) Male Female 11-20 (n = 20) 13 7 21-30 (n = 20) 12 8 31-40 (n = 20) 9 11 41-50 (n = 20) 12 8 51-60 (n = 20) 9 11 61-70 (n = 20) 6 14 71-80 (n = 20) 7 13 81 (n = 20) 7 13 All ages (n = 160) 75 85 A B Figure 1. Distributions of different kinds of astigmatism by age group. (A) The anterior cornea, The proportions of with-the rule astigmatisms are 95% in the 11 20 age group and 15% in the 81 age group. (B) The posterior cornea, The proportions of with-the-rule astigmatisms are 0% in the 11 20 age group and 5% in the 71 age group. ATR = against the rule; WTR = with the rule. 912
- 심윤섭외 : 각막난시의연령증가에따른변화 - A B Figure 2. Scattergrams of polar values described by Naeser (in diopter) versus age and the linear regression model. (A) The anterior corneal astigmatisms showed a significant against-the-rule change with age. The average change in against-the-rule astigmatism every 10 years was 0.356 D. On the other hand, (B) The posterior corneal astigmatism displayed with-the-rule changes with age with an average. The average change in with-the-rule astigmatism every 10 years was 0.033 D. 고찰 기존연구들에서각막전면난시는연령이증가함에따라직난시에서도난시로변화하는경향을보이는반면, 각막후면난시는연령과관계없이대부분도난시인모습을보였다. 3,7 또한공기와각막전면부의굴절계수차 (1.376 1=0.376) 에비하여, 각막후면과방수의굴절계수차 (1.336 1.376=-0.04) 는크기가작기때문에그동안각막후면난시는임상적으로중요하게여겨지지않았다. 각막곡률계는각막전면의곡률반경을측정하여 D=(n-1)/r (n= 안구의평균굴절률지수, r= 각막전면의곡률반경 ) 이라는면굴절력공식을이용해각막굴절력 (D) 을구할수있는장비로전통적으로각막곡률계로측정한각막전면굴곡에대한값을수정굴절상수 (modified refractive index: 1.3375) 를사용하여전체각막굴절력으로추정및환산한난시를각막계난시 (Keratometric Astigmatism) 라고하였다. 1 반면 Pentacam 이나 Orbscan II (Orbtec Inc., Salt Lake City, UT, USA) 같은각막지형도검사는각각세극등의원리와플라시도반사를이용해전안부이미지를 3차원적구조로재구성하기에전면과후면의각막을각각볼수있으며각막의특정부분에서의난시값을얻을수있다. Ho et al 11 의연구결과 (493안) 에서각막곡률계를이용하여측정한각막계난시는 Pentacam 을이용하여측정한각막전체난시와평균적으로크기 0.24 ± 0.16디옵터, 축 7.4 ± 10.3 의차이를보였으며이는각막후면난시때문으로사료된다. Ueno et al 7 의연구결과 (419안) 에서는각막후면난시는전면난시와는다르게연령과관계없이일정하게도난시인모습을보였다. 이연구는일본인을대상으로하 였다는점에서본연구와인종적으로유사하다고할수있으나 3D-OCT를이용하였다는점에서본연구와차이가있었다. 한편, Ho et al 9 의 Pentacam 을이용한연구결과 (370 안 ) 에서는연령증가에따라각막후면난시에서도난시의비율이통계적으로유의하게감소하는경향을보였다. 또한극값을이용한분석결과각막전면난시는도난시로변화하는경향을보였으며, 5년간평균변화량은 0.18D였고, 각막후면난시는직난시로변화하는경향을보였으며, 5년간평균변화량은 0.022D로본연구의결과와유사하였다. 국내에서진행되었던 Kim et al 12 의각막곡률계와등가교차원주렌즈를이용한연구결과 (263안) 에서는각막전체난시에서각막난시를뺀값을잔여난시로정의하여분석하였다는점에서각막후면난시를직접측정한본연구와차이가있으나, 잔여난시가전연령군에서대부분도난시를보였으며, 연령증가에따라도난시의감소양상을보였다는점에서본연구의결과와유사하였다. 각막난시의경우연령증가에따라직난시에서도난시로이행하는모습을보였으며이또한본연구의결과와유사하였다. 연령증가에따라각막전체난시가도난시화되는것의기전에대하여윗눈꺼풀긴장도의감소, 13 외안근의긴장도의변화, 14 각막구조의변화 15 등여러가지가설이제시되었으나현재까지명확한원인으로밝혀진것은없다. 본연구결과에따르면연령이증가함에따라각막전면난시는도난시화, 각막후면난시는직난시화되는경향을보이는데, 이는모두공통적으로각막곡률의가파른쪽이 180 ± 30 에위치하게되는것을의미한다. 각막에상하방향에서중심부로작용하는힘이감소되거나, 좌우방향에서중심부로작용하는힘이증가할때이러한변화가나타날수있을것 913
- 대한안과학회지 2017 년제 58 권제 8 호 - 으로사료되기에이와같은사실을활용하면각막난시축의변화원인을알아내는데도움이될것으로사료된다. 본연구의제한점으로는연구대상자수가적으며, 안과환자만을대상으로하여, 전체한국인을대표한다는데한계가있다는점, 여러장비로측정치의오류를보정하지못하였다는점등이있다. 각막후면난시가도난시일경우, 전체난시에 net against-the-rule astigmatism을유발하게된다. 따라서각막후면난시를고려하지않고난시교정인공수정체를삽입할경우환자의각막전면난시가도난시인경우술후부족교정을, 직난시인경우술후과교정을유발할수있으므로주의를기울여야한다. 16-18 저자들은본연구결과를통해각막후면난시는연령이증가함에따라도난시에서직난시로변화하는경향이있음을알수있었다. 이를토대로백내장수술후난시를줄이기위해, 특히고령인환자에서다초점인공수정체나난시교정용인공수정체를이용할경우각막후면난시의변화를고려하는것이환자들에게보다나은시력의질을제공할수있을것으로생각된다. REFERENCES 1) Kim CS, Kim M, Kim HS, Lee YC. Change of corneal astigmatism with aging in Koreans with normal visual acuity. J Korean Ophthalmol Soc 2002;43:1956-62. 2) Han JM, Choi HJ, Kim MK, et al. Comparative analysis of corneal refraction and astigmatism measured with Autokeratometer, IOL Master, and Topography. J Korean Ophthalmol Soc 2011;52: 1427-33. 3) Koch DD, Ali SF, Weikert MP, et al. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg 2012;38:2080-7. 4) Reitblat O, Levy A, Kleinmann G, et al. Effect of posterior corneal astigmatism on power calculation and alignment of toric intraocular lenses: comparison of methodologies. J Cataract Refract Surg 2016;42:217-25. 5) Cheng LS, Tsai CY, Tsai RJ, et al. Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement. Acta Ophthalmol 2011;89:417-22. 6) Miyake T, Shimizu K, Kamiya K. Distribution of posterior corneal astigmatism according to axis orientation of anterior corneal astigmatism. PLoS One 2015;10:e0117194. 7) Ueno Y, Hiraoka T, Beheregaray S, et al. Age-related changes in anterior, posterior, and total corneal astigmatism. J Refract Surg 2014;30:192-7. 8) Lim TH, Lee JR, Choi KY, Cho BJ. Anterior and posterior corneal spherical aberration measured with Pentacam in the Korean. J Korean Ophthalmol Soc 2010;51:816-21. 9) Ho JD, Liou SW, Tsai RJ, Tsai CY. Effects of aging on anterior and posterior corneal astigmatism. Cornea 2010;29:632-7. 10) Naeser K. Conversion of keratometer readings to polar values. J Cataract Refract Surg 1990;16:741-5. 11) Ho JD, Tsai CY, Liou SW. Accuracy of corneal astigmatism estimation by neglecting the posterior corneal surface measurement. Am J Ophthalmol 2009;147:788-95, 795.e1-2. 12) Kim CS, Ryu JW, Kim HS, Lee YC. Distribution and change of total astigmatism, corneal astigmatism and residual astigmatism with age in patient with emmetropia. J Korean Ophthalmol Soc 2005; 46:485-93. 13) Grosvenor T. Etiology of astigmatism. Am J Optom Physiol Opt 1978;55:214-8. 14) Howland HC, Sayles N. Photokeratometric and photorefractive measurements of astigmatism in infants and young children. Vision Res 1985;25:73-81. 15) Hayashi K, Hayashi H, Hayashi F. Topographic analysis of the changes in corneal shape due to aging. Cornea 1995;14:527-32. 16) Koch DD, Jenkins RB, Weikert MP, et al. Correcting astigmatism with toric intraocular lenses: effect of posterior corneal astigmatism. J Cataract Refract Surg 2013;39:1803-9. 17) Zhang L, Sy ME, Mai H, et al. Effect of posterior corneal astigmatism on refractive outcomes after toric intraocular lens implantation. J Cataract Refract Surg 2015;41:84-9. 18) Nemeth G, Berta A, Szalai E, et al. Analysis of surgically induced astigmatism on the posterior surface of the cornea. J Refract Surg 2014;30:604-8. 914
- 심윤섭외 : 각막난시의연령증가에따른변화 - = 국문초록 = 한국인의각막전면, 후면난시축의분포와연령에따른변화 목적 : 한국인에서연령증가에따른각막전면및후면난시의변화를알아보고자하였다. 대상과방법 : 11 세부터 92 세까지특이안질환이없는 160 명의각막전면및후면난시를회전샤임플러그카메라 (Pentacam R ) 를이용하여측정하였다. 이자료를이용해연령증가에따른각막전면및후면난시에서도난시와직난시의비율변화와극값을이용한변화경향을분석하였다. 결과 : 각막전면난시는연령이증가함에따라직난시의비율이감소하는경향을보였으며 (p<0.0001), 각막후면난시는도난시의비율이감소하는경향을보였다 (p=0.012). 극값을이용하여분석한결과에서는연령이증가함에따라각막전면난시는도난시로변화하는경향 (p<0.0001) 을, 후면난시는직난시로변화하는경향을보였다 (p<0.0001). 결론 : 기존연구들에서각막전면난시는연령이증가함에따라직난시에서도난시로변화하는경향을보이는반면, 각막후면난시는연령과관계없이대부분도난시인모습을보였다. 그러나본연구결과에따르면각막후면난시는연령이증가함에따라도난시의비율이감소하는경향을보였다. 따라서고령인환자에서의백내장수술시, 특히다초점혹은난시교정인공수정체를사용할경우각막후면난시에대한평가를반드시시행해야한다. < 대한안과학회지 2017;58(8):911-915> 915