Seung Hee Baek

An Overview of Ophthalmologic Survey Methodology in the 2008-2015 Korean National Health and Nutrition Examination Surveys

The Korea National Health and Nutrition Examination Survey (KNHANES) is a national program designed to assess the health and nutritional status of the noninstitutionalized population of South Korea. The KNHANES was initiated in 1998 and has been conducted annually since 2007. Starting in the latter half of 2008, ophthalmologic examinations were included in the survey in order to investigate the prevalence and risk factors of common eye diseases such as visual impairment, refractive errors, strabismus, blepharoptosis, cataract, pterygium, diabetic retinopathy, age-related macular degeneration, glaucoma, dry eye disease, and color vision deficiency. The measurements included in the ophthalmic questionnaire and examination methods were modified in the KNHANES IV, V, and VI. In this article, we provide detailed information about the methodology of the ophthalmic examinations in KNHANES in order to aid in further investigations related to major eye diseases in South Korea.

Refractive Errors in Koreans: The Korea National Health and Nutrition Examination Survey 2008-2012

Purpose Our study provides epidemiologic data on the prevalence of refractive errors in all age group ≥5 years in Korea. Methods In 2008 to 2012, a total of 33,355 participants aged ≥5 years underwent ophthalmologic examinations. Using the right eye, myopia was defined as a spherical equivalent (SE) less than -0.5 or -1.0 diopters (D) in subjects aged 19 years and older or as an SE less than -0.75 or -1.25 D in subjects aged 5 to 18 years according to non-cycloplegic refraction. Other refractive errors were defined as follows: high myopia as an SE less than -6.0 D; hyperopia as an SE larger than +0.5 D; and astigmatism as a cylindrical error less than -1.0 D. The prevalence and risk factors of myopia were evaluated. Results Prevalence rates with a 95% confidence interval were determined for myopia (SE <-0.5 D, 51.9% [51.2 to 52.7]; SE <-1.0 D, 39.6% [38.8 to 40.3]), high myopia (5.0% [4.7 to 5.3]), hyperopia (13.4% [12.9 to 13.9]), and astigmatism (31.2% [30.5 to 32.0]). The prevalence of myopia demonstrated a nonlinear distribution with the highest peak between the ages of 19 and 29 years. The prevalence of hyperopia decreased with age in subjects aged 39 years or younger and then increased with age in subjects aged 40 years or older. The prevalence of astigmatism gradually increased with age. Education was associated with all refractive errors; myopia was more prevalent and hyperopia and astigmatism were less prevalent in the highly educated groups. Conclusions In young generations, the prevalence of myopia in Korea was much higher compared to the white or black populations in Western countries and is consistent with the high prevalence found in most other Asian countries. The overall prevalence of hyperopia was much lower compared to that of the white Western population. Age and education level were significant predictive factors associated with all kinds of refractive errors.

A nationwide population-based study of low vision and blindness in South Korea.

PURPOSE To investigate the prevalence and associated risk factors of low vision and blindness in the Korean population. METHODS This cross-sectional, population-based study examined the ophthalmologic data of 22,135 Koreans aged ≥5 years from the fifth Korea National Health and Nutrition Examination Survey (KNHANES V, 2010-2012). According to the World Health Organization criteria, blindness was defined as visual acuity (VA) less than 20/400 in the better-seeing eye, and low vision as VA of 20/60 or worse but 20/400 or better in the better-seeing eye. The prevalence rates were calculated from either presenting VA (PVA) or best-corrected VA (BCVA). Multivariate regression analysis was conducted for adults aged ≥20 years. RESULTS The overall prevalence rates of PVA-defined low vision and blindness were 4.98% and 0.26%, respectively, and those of BCVA-defined low vision and blindness were 0.46% and 0.05%, respectively. Prevalence increased rapidly above the age of 70 years. For subjects aged ≥70 years, the population-weighted prevalence rates of low vision, based on PVA and BCVA, were 12.85% and 3.87%, respectively, and the corresponding rates of blindness were 0.49% and 0.42%, respectively. The presenting vision problems were significantly associated with age (younger adults or elderly subjects), female sex, low educational level, and lowest household income, whereas the best-corrected vision problems were associated with age ≥ 70 years, a low educational level, and rural residence. CONCLUSIONS This population-based study provides useful information for planning optimal public eye health care services in South Korea.

Quantitative Analysis of Optic Disc Color

Purpose To evaluate the reproducibility of ImageJ software in analyzing the color of the optic disc. Methods One hundred twelve normal participants (56 males and 56 females) were enrolled in this study. The image of the optic disc was taken using Kowa digital disc photo-graphy, and the gray scales of the nasal rim (NR), brightest cupping center (BCC) and largest inferior retinal vein (IRV) were calculated using histogram in ImageJ. Three different observers calculated the gray scales three separate times. Reproducibility was assessed using the interclass correlation coefficient (ICC). Results The mean age of the participants was 50.6 years old (range, 11 to 82 years). The mean gray scales of the nasal rim were 91.81, 94.91, and 93.24; those of the brightest cupping center were 174.84, 179.94, and 177.76; and those of the largest inferior retinal vein were 61.85, 53.48, and 56.73 for observers 1, 2, and 3, respectively. Inter-observer reproducibility for NR, BCC and IRV was considered good based upon ICC values of 0.944, 0.860, and 0.789 for observers 1, 2, and 3, respectively. Significant age-related differences between the values of the brightest cupping center were noted, and the gray scale score was decreased in the older participants (p < 0.001). Conclusions The gray scale of the brightest cupping center diminished with age. ImageJ can be a useful objective tool with high reproducibility in the analysis of optic disc color.

Attempts to Reduce the Progression of Myopia and Spectacle Prescriptions during Childhood: A Survey of Eye Specialists

Purpose To determine methods tried in clinical trials to reduce the progression of myopia in children, and spectacle prescribing patterns of hospital ophthalmologists. Methods A multi-sectioned survey composed of Likert items relating to the methods of reducing myopia progression (orthokeratology lenses [O-K lenses], undercorrected glasses, and topical atropine) and the patterns of prescribing spectacles for children (including two cases involving a 5-year-old girl and an 8-year-old boy) were distributed to members of the Korean Ophthalmological Society, and the collected data was statistically analyzed. Results A total of 78 out of 130 ophthalmologists returned the survey. On a scale of 1 to 5, the mean rates of whether the ophthalmologists think O-K lenses arrest myopia progression, and whether they recommend their patients to wear O-K lenses if indicative, were 3.06 and 2.75, respectively. Moreover, the mean rates of whether they consider that wearing glasses which are undercorrected would slow down the progression of the myopia, or if they think topical atropine helps in arresting myopia progression in children, were 2.34 and 1.27, respectively. In response to the case studies, the majority of practitioners preferred to prescribe the full amount found in cycloplegic refraction to pediatric patients with myopia. Conclusions Ophthalmologists in clinical practice encouraged children to wear O-K lenses more than undercorrected glasses as a way to retard myopia progression. However, the application of atropine is rarely tried in clinical trials. In managing pediatric patients with myopia (case specific), the majority of the practitioners chose to prescribe glasses with full cycloplegic correction.

Body Stature as an Age-Dependent Risk Factor for Myopia in a South Korean Population*

ABSTRACT Purpose: To evaluate the association between myopia and risk factors, including anthropometric parameters. Methods: A total of 33,355 Koreans five years of age or more participated in the Korea National Health and Nutrition Examination Survey 2008–2012. All participants underwent non-cycloplegic autorefraction and were divided into three age groups (children and adolescents; young adults; adults). Myopia prevalence and risk factors were evaluated. Results: The prevalence of myopia was significantly higher in the taller quintiles of children and adolescents; however, not in young adults or adults in multivariate regression analyses. Higher household income was significantly associated with myopia only in children and adolescents, whereas urban residence and higher education were significantly associated with myopia in young adults and adult-aged subjects. Conclusions: Associations between myopia and sociodemographic factors, such as income and education, varied in each age group, and height remained significantly associated with myopia only in children and adolescents.

Relationship of Hypertropia and Excyclotorsion in Superior Oblique Palsy

Purpose To evaluate the correlation between hypertropia and excyclotorsion in acquired superior oblique palsy (SOP). Methods Thirty-one patients with acquired unilateral SOP were recruited for this study. The torsional angle of each patient was assessed via one objective method (fundus photography) and two subjective methods (double Maddox rod test and major amblyoscope). The patient population was divided into two groups (concordance group, n = 19 and discordance group, n = 12) according to the correspondence between the hypertropic eye (paralytic eye) and the more extorted eye (non-fixating eye), which was evaluated by fundus photography. Results The mean value of objective torsion was 5.09° ± 3.84°. The subjective excyclotorsion degrees were 5.18° ± 4.11° and 3.65° ± 1.93° as measured by double Maddox rod test and major amblyoscope, respectively. Hypertropia and the excyclotorsional angle did not differ significantly between the groups (p = 0.257). Although no correlation was found in the discordance group, the concordance group showed a significant and positive correlation between hypertropia and excyclotorsion (p = 0.011). Conclusions Torsional deviation was not related to hypertropia. However, in the concordance patients in whom the hypertropic eye showed excyclotorsion, a significant positive correlation was found between hypertropia and excyclotorsion.

Long-term Follow-up of Acute Isolated Accommodation Insufficiency

Purpose To define the long-term results of accommodation insufficiency and to investigate the correlation between accommodation insufficiency and other factors including near point of convergence (NPC), age, and refractive errors. Methods From January 2008 to December 2009, 11 patients with acute near vision disturbance and remote near point of accommodation (NPA) were evaluated. Full ophthalmologic examinations, including best corrected visual acuity, manifest refraction and prism cover tests were performed. Accommodation ability was measured by NPA using the push-up method. We compared accommodation insufficiency and factors including age, refractive errors and NPC. We also investigated the recovery from loss of accommodation in patients. Results Mean age of patients was 20 years (range, 9 to 34 years). Five of the 11 patients were female. Mean refractive error was -0.6 diopters (range, -3.5 to +0.25 diopters) and 8 of 11 patients (73%) had emmetropia (+0.50 to -0.50 diopters). No abnormalities were found in brain imaging tests. Refractive errors were not correlated with NPA or NPC (rho = 0.148, p = 0.511; rho = 0.319, p = 0.339; respectively). The correlation between age and NPA was not significant (rho = -395, p = 0.069). However, the correlation between age and NPC was negative (rho = -0.508, p = 0.016). Three of 11 patients were lost to follow-up, and 6 of 8 patients had permanent insufficiency of accommodation. Conclusions Accommodation insufficiency is most common in emmetropia, however, refractive errors and age are not correlated with accommodation insufficiency. Dysfunction of accommodation can be permanent in the isolated accommodation insufficiency.

Vision Improvement with Refractive Correction Does Not Completely Exclude Major Eye Diseases: Analyses of Visually Impaired South Korean Population in the Korea National Health and Nutrition Examination Survey 2009–2011

Purpose To investigate the association between vision improvement with refractive correction in the visually impaired eyes and the prevalence of ocular comorbidities in the South Korean population. Materials and Methods The data of 24,620 individuals in the Korea National Health and Nutrition Examination Survey (KNHANES 2009–2011) were reviewed. Visual impairment was defined as a presenting visual acuity < 20/60. The participants with visual impairment in at least one eye were divided into 3 groups according to the best-corrected visual acuity (group 1: <20/30, group 2: ≥20/30 but <20/25, and group 3: ≥20/25). The prevalence of ocular comorbidities was estimated and compared between the three groups. Results Visual impairment in at least one eye was found in 3031 individuals. Groups 1, 2, and 3 comprised 23.5%, 22.2%, and 54.3% of these visually impaired eyes, respectively. The prevalence of cataract, diabetic retinopathy, age-related macular degeneration, corneal opacity, blepharoptosis, and pterygium was similar to or even higher in group 2 compared to group 1. The prevalence of glaucoma and age-related macular degeneration was 5.40% and 11.39%, respectively, in group 2 and 3.31% and 3.76%, respectively, in group 3. Conclusions Appropriate ophthalmologic examination is necessary even if people exhibit vision improvement after optical correction.