Por-Tying Hung

Epidemiologic Study of Ocular Refraction among Schoolchildren in Taiwan in 1995

PURPOSE In order to understand and update the prevalence of myopia in Taiwan, a nationwide survey was performed in 1995. METHODS We stratified the cluster sampling by developmental grading of the city, using a size proportional to the population. Two cities were randomly selected from each city grading. The total number of students enrolled was 11,178, including 5,676 boys and 5,502 girls. The refractive status and corneal radius of each student were measured with an autorefractometer under cycloplegia and checked with retinoscopy. Axial length was measured with biometric ultrasound. RESULTS The myopic rate was from 12% at the age of 6, it increased to 56% at the age of 12, and then to 76% at the age of 15. A myopic rate of 84% was found for the age range of 16 to 18. The prevalence of high myopia (over -6.0 D) at the age of 18 was 20% in girls and 12% in boys. The mean refractive status became myopic at the age of 9, then increased to -3.92 D in girls and -2.71 D in boys at the age of 18. The increase of axial length is correspondent with the progression of myopia. The anterior chamber depth (ACD) was deeper with age and the severity of myopia, whereas the corneal curvature remained unchanged. The lens thickness became thinner from age 7 to 13, then it became thicker with age and the severity of myopia after age 15. The prevalence and degree of myopia in girls was more severe than in boys. CONCLUSIONS The prevalence of myopia in Taiwan increased year by year. The increase in severity and prevalence of high myopia may be due to earlier onset.

Changes in ocular refraction and its components among medical students : A 5-year longitudinal study

Purpose. Myopic progression has been noted, especially during the period of puberty. It is interesting to investigate whether myopia will progress after the age of puberty and at what rate the changes in ocular components occur during its progression. Methods. A 5-year longitudinal study was made of refraction and its components among 345 National Taiwan University medical students (690 eyes). The examinations included corneal curvature and cycloplegic refraction measured by auto-refractor and retinoscopy, and axial length measurement with A scan ultrasonography. The same procedures and instruments were used again after 5 years. Results. The myopic prevalence increased from 92.8 to 95.8%; 21 new cases of myopia developed in the 5 years. The mean refractive error significantly increased from —4.26 ± 2.66 D of freshmen to -4.94 ± 2.70 D of clerks. The change in refractive error at the 5-year follow-up was 0.70 ± 0.65 D more myopic for males and 0.54 ± 0.64 D for females. The main change in the ocular components was in axial length, which increased from 25.54 to 26.05 mm in males and from 24.60 to 24.95 mm in females. Other optical components—including corneal curvature, anterior chamber depth, lens thickness— all remained relatively unchanged from the initial values. Conclusions. Myopia can progress after the age of puberty, but at a slower rate than during childhood. Axial elongation of the eyeball is the main component that changes in myopic progression.

Intraocular lens position and anterior chamber angle changes after cataract extraction in eyes with primary angle-closure glaucoma

Purpose: To prospectively study the anterior chamber angle in eyes with chronic primary angle‐closure glaucoma (PACG) having posterior chamber intraocular lens (IOL) implantation and evaluate IOL position and intraocular pressure (IOP). Setting: National Taiwan University Hospital, Taipei, Taiwan. Methods: Using Scheimpflug image processing, the anterior chamber angles were studied in 20 consecutive eyes with chronic PACG and 10 control eyes before and after posterior chamber IOL implantation. Anterior chamber depth, chamber angle width, IOL position, and IOP change were evaluated. Results: Mean anterior chamber depth in the PACG group was 2.04 ± 0.29 mm preoperatively and 3.44 ± 0.16 mm postoperatively. The anterior chamber angle widened significantly in relation to the superior, inferior, temporal, and nasal quadrants after surgery. The degree of IOL tilting and decentration was the same in both the PACG and control groups. All eyes in the PACG group maintained an IOP under 21 mm Hg during the 6 month follow‐up. Eighty‐four percent maintained or decreased their antiglaucoma medication; 16% required increased medication. Conclusion: Cataract extraction with posterior chamber IOL implantation in eyes with PACG controlled IOP well in most cases.

The prevalence of astigmatism in Taiwan schoolchildren.

Purpose. To understand the prevalence and distribution of astigmatism in schoolchildren in Taiwan, we analyzed and compared the nationwide survey data in 1995 and 2000. Methods. A total of 11,175 students were enrolled in 1995, and 10,878 students were enrolled in 2000. The refractive status of each student was measured with an autorefractor during cycloplegia and rechecked with retinoscopy. Results. About half of schoolchildren (57.5% in 1995 and 49.0% in 2000) had no astigmatism (<0.5 D). About one third of schoolchildren’s astigmatism was <1 D (27.9% vs. 32.6%). Eleven percent of schoolchildren in 1995 and 13% in 2000 had astigmatism between 1.0 and 2.0 D. Less than 2% of students had astigmatism >3.0 D (1.3% in 1995 and 1.8% in 2000). Most astigmatism was with-the-rule: 83.3% in 1995 and 89.9% in 2000. Only 16.6% of children in 1995 and 9.7% in 2000 had against-the-rule astigmatism. Very little astigmatism was oblique (0.1% in 1995 and 0.4% in 2000). The rate of myopic astigmatism increased with age. In contrast, the rate of hyperopic and mixed astigmatism decreased with age. In addition, the rate of with-the-rule astigmatism increased and the rate of against-the-rule decreased with respect to age, but oblique astigmatism was rather stable with age. Conclusions. Most schoolchildren had little or no astigmatism. In Taiwan, most astigmatism is <1 D and is myopic with-the-rule astigmatism. There was more myopic astigmatism and with-the-rule astigmatism in 2000 than in 1995.

Study of myopia among aboriginal school children in Taiwan

In various studies there were racial differences as to the refractional status between the white and the black or the natives (Taylor 198 1). Chandran (1972) thus compared the refractive errors of the Malayan, the Chinese and the Indian (or the Indonesian) in West Malaysia. The natives in Solomon Islands were found to have as low a rate as only 1 % of myopia (Verlee 1968). Most people in Taiwan descend from those who came to this island from mainland China some 300 years ago. According to the biostatistics, about one sixtieth of our population are the aboriginals, or the so-called high-mountain people. There are 9 tribes of them. It is believed that the aborigines in Taiwan belong to the Polynesians, which came from the South Pacific islands. In previous studies of the highmountain people Japanese authors reported that the myopic rates were exceptionally low (Motegi et al. 1945; Yamaji et al. 198 1). In order to know how the myopia would affect a different racial group living in the same Formosa, the authors made a refraction survey of 18 junior high schools around the whole island. All the children in the schools were examined, using retinoscopy performed under cycloplegia.

Early treatment of severe cystoid macular edema in central retinal vein occlusion with posterior sub-tenon triamcinolone acetonide.

Purpose: To evaluate the clinical outcomes of posterior sub-Tenon (PST) injection of triamcinolone acetonide (TA) in the early treatment of severe cystoid macular edema (CME) in central retinal vein occlusion (CRVO). Methods: In a noncomparative, prospective study, 18 eyes of 18 patients with severe CME (central macular thickness, CMT >450 &mgr;m) secondary to recent-onset CRVO (the onset of symptoms ≤4 weeks) and a decrease in visual acuity (≤80 letters of Early Treatment Diabetic Retinopathy Study [ETDRS] scores, 20/50) were included. PST injection of 40 mg of TA was given under topic anesthesia. All patients received three biweekly injections and were evaluated at baseline and at 1 day, 1, 2, 4, 6, and 8 weeks, and 3, 6, and 9 months after injection. The main outcome measures were ETDRS scores, CMT, intraocular pressure (IOP), cataract progression, and frequency of complications. Results: The mean age of the 18 patients was 61.17 years (range, 24–81 years) and the mean duration of symptoms was 15.28 days (range, 9–28 days). Eight eyes were diagnosed with ischemic CRVO and 10 eyes with nonischemic CRVO. Mean baseline ETDRS visual acuity (VA) score was 36.89 ± 18.22 in all affected eye. There was a significant improvement in VA at 1, 3, 6, and 9 months of follow-up. The mean VA at these time points were 46.61 ± 20.21, 58.11 ± 22.19, 59.39 ± 22.98, and 58.67 ± 23.27 (all P < 0.001), respectively. Both nonischemic and ischemic eyes benefited with a statistically significant VA improvement at each time point. A comparison of the gain in VA between two subgroups was not significant at 1 and 3 months (P > 0.05), but was statistically significant at 6 and 9 months (P = 0.009 and 0.008, respectively). VA gain of 10 or more letters was found in all nonischemic eyes (10/10) and 3 ischemic eyes (3/8) at the 9-month follow-up. Two ischemic eyes were found to have no gain of letters in VA at the 9-month follow-up. The mean baseline CMT for all eyes was 566 ± 42 &mgr;m. There was a 29% reduction with a mean CMT of 404 ± 49 &mgr;m (P < 0.001) at 1 month, 51% reduction with a mean CMT of 278 ± 40 &mgr;m (P < 0.001) at 3 months, 61% reduction with a mean CMT of 222 ± 56 &mgr;m (P < 0.001) at 6 months, and 63% reduction with a mean CMT of 210 ± 30 &mgr;m (P < 0.001) at 9 months. Both nonischemic and ischemic eyes demonstrated a statistically significant reduction in CMT (all P < 0.001). A comparison of the reduction in CMT between these two subgroups was not significant at each visit (all P > 0.05). For both subgroups, there was no statistically significant difference in IOP change at baseline, 1 week, 1, 3, 6, and 9 months of follow-up. Only two patients required topic antiglaucoma drops for elevated IOP. Three patients developed a recurrence of CME accompanied with visual decrease. No cataract progression or other complications were observed. Conclusions: PST injection of TA is effective in reversing CME and improving visual acuity in recent-onset CRVO in the first 9 months. Patients with nonischemic CRVO may respond more favorably than patients with ischemic CRVO. Early treatment may be better for visual improvement before longstanding macular edema results in irreversible photoreceptor damage. Further study with longer follow-up period is necessary.

Comparing myopic progression of urban and rural Taiwanese schoolchildren

PurposeTo compare myopic progression rates in Taiwanese schoolchildren between urban and rural areas.MethodsSeveral longitudinal studies of myopic progression were performed in urban and rural areas. Five primary schools, four junior high schools, and two senior high schools were selected from both urban and rural areas. Ages ranged from 7 to 18 years. The refractive state of each student was measured with an autorefractometer under cycloplegia.ResultsMean myopic progression in primary school children (ages 7 to 12) in the urban areas was around 0.20 D/year for boys and 0.27 D/year for girls. The mean myopic progression rate in urban children from primary to junior high school age (ages 10 to 15) was 0.43 D/year for boys and 0.50 D/year for girls, faster than that in rural children (0.24 and 0.31 D/year, respectively). The average progression rate was fastest in children in junior high school (ages 13 to 15), around 0.45 D/year in urban areas and 0.28 D/year in rural areas. In senior high schools (ages 16 to 18), myopic progression slowed to 0.17 D/ year in boys and 0.33 D/year in girls. Myopic progression in all groups was faster in myopic eyes than in emmetropic or hyperopic eyes.ConclusionsThe average myopic progression in urban areas was greater than that in rural areas. Environmental factors such as urban development and academic grade level may be important contributing factors to myopic progression.

Ciliary detachment after pars plana vitrectomy: an ultrasound biomicroscopic study.

Purpose To determine the incidence, duration, risk factors, and clinical outcomes for ciliary detachment after pars plana vitrectomy (PPV). Methods A total of 109 eyes of 103 patients who underwent PPV for various disease entities were included. Ultrasound biomicroscopy was applied to determine the tomographic features of the ciliary body before and 1, 3, and 7 days after the surgery. All eyes were then examined once weekly for 2 months. Demographic, preoperative, intraoperative, and postoperative parameters were evaluated to assess their predictive value in the formation of postvitrectomy ciliary detachment. Results Ciliary detachment was observed in 46 eyes (42%) after surgery and persisted for less than 3 weeks in 40 of 46 eyes. It most frequently occurred in eyes of patients with proliferative diabetic retinopathy (PDR) (64%) or retinal vascular obstructive diseases (RVO) (47%). Extensive retinal photocoagulation and retinal cryopexy positively predisposed to its formation whereas fluid–gas exchange had a protective effect. No clinical complications were observed in eyes with postoperative ciliary detachment. Conclusion Ciliary detachment occurred frequently after PPV. A diagnosis of PDR or RVO and surgical procedures with extensive retinal photocoagulation and retinal cryopexy may have a higher incidence of its occurrence.

Logistic regression analysis for glaucoma diagnosis using stratus optical coherence tomography

Purposes. The purposes of this study are to investigate the diagnostic performance of logistic regression analysis (LRA) applied to multidimensional information on glaucoma disease and to determine the area under receiver operator characteristic curves (AROCs) for differentiating between normal and glaucomatous eyes in the Taiwan Chinese population based on the summary data from the Stratus Optical Coherence Tomography (OCT). Methods. One randomly selected eye from each of the 89 patients with glaucoma and from each of the 88 age- and gender-matched normal individuals were included in the study. Nine glaucomatous eyes and eight normal eyes were excluded as a result of poor OCT scans. Finally, 80 normal eyes and 80 glaucomatous eyes (mean deviation, –4.5 ± 4.12 dB) were analyzed. The whole dataset was split into four equal sets. Each set combines 20 patients with glaucoma and 20 normal individuals. Fourfold crossvalidation was conducted. Retinal nerve fiber layer thickness and optic nerve head were measured by Stratus OCT in each patient. Twenty-five OCT parameters were included in a LRA method to determine the best combination of parameters for discriminating between glaucomatous and healthy eyes based on AROCs. Results. With the LRA method, the AROC for glaucoma detection was 0.911 with sensitivity at 80% and 90% specificity were 83.7% and 80.0%, respectively. Conclusions. Compared with the OCT-provided parameters, the LRA method improved the ability to differentiate between normal and glaucomatous eyes in the Taiwan Chinese population.

Prevalence of Anisometropia in Taiwanese Schoolchildren

BACKGROUND AND PURPOSE This study investigated the prevalence and distribution of anisometropia in Taiwanese schoolchildren using nationwide data from refractive surveys performed in 1995 and 2000. METHODS Complete survey data was obtained for 11,175 students in 1995 and 10,878 students in 2000. The refractive status of each student was measured using an autorefractometer under cycloplegia and rechecked with retinoscopy. The difference in refractive status between each participants eyes was determined. Chi-squared statistic was used to assess the difference between the 2 surveys. Multiple linear regression was used to determine the trend and effects of covariates. RESULTS Most of the schoolchildren (77.6% in 1995, 71.9% in 2000) were not anisometropic. Most of the anisometropic differences were in the range 0.5 to 1.0 D (14.1% in 1995 vs 17.9% in 2000). About 6% of schoolchildren in 1995 and 7.0% in 2000 had anisometropic differences in the range from -1.0 to -2.0 D. Fewer than 4% of students had a level of anisometropia greater than 2.0 D (2.7% vs 3.2%, respectively). The prevalence of anisometropia and the extent of anisometropic difference both increased with age and with maximal myopic refraction (both p < 0.0001). Both the prevalence and extent of anisometropia showed significant differences between the 2 surveys (both p < 0.0001). CONCLUSIONS Most of the Taiwanese schoolchildren surveyed were non-anisometropic. The prevalence and amount of anisometropia were significantly increased from 1995 to 2000. The mechanisms responsible for these increases have not been determined, but may be related to increase of myopic refraction.