Luke L.-K. Lin

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.

Lens Thickness Changes among Schoolchildren in Taiwan

PURPOSE To explore the possible influence of ocular growth, refractive error and age on the crystalline lens in school-age children. METHODS A Taiwan nationwide survey of myopia performed in 2006 was used to determine the prevalence and severity of myopia and the changes in ocular components. A total of 11,656 students were enrolled, including 5,390 boys and 6,266 girls, with ages ranging from 7 to 18 years. Refractive status was measured with an autorefractometer with the subject under cycloplegia. Lens thickness, anterior chamber depth, and axial length were measured with biometric ultrasound. RESULTS Data revealed that the crystalline lens became thinner between the ages of 7 and 11. Subsequent increases in the lens thickness correlated with age and the stability of myopia. This phenomenon was found not only in myopic eyes, but also in emmetropic and hyperopic eyes. The changes in anterior chamber depth inversely correlated with the changes in the lens. In school-age children, the ratio of lens/axial length was found to be significant: approximately 0.147 in the emmetropic group. However the ratio was seen to increase with age. The ratio of anterior segment/axial length was found to be approximately 0.3 in emmetropic eyes among all age groups and less than 0.3 in the myopic eyes of schoolchildren. CONCLUSIONS Lens thinning appeared to be compensatory in nature with respect to the increased axial length of normal eye growth. Myopic eye growth induces the lens to compensate by becoming much thinner. The change in anterior chamber depth corresponded inversely with lens thickness.

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.

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.

Prevention of Exposure of Porous Orbital Implants Following Enucleation

PURPOSE To investigate effectiveness of adding a scleral patch graft on a Vicryl mesh-wrapped porous orbital implant to prevent exposure following enucleation. DESIGN A retrospective, comparative, nonrandomized study. METHODS From October 1996 to February 2006, 74 consecutive patients (74 sockets) who received porous orbital implants primarily or secondarily after enucleation at National Taiwan University Hospital (72 cases) and at Far Eastern Memorial Hospital (2 cases) were collected. Patient demographics, ocular diagnosis, the surgical technique, prior ophthalmic surgery, type, covering, and size of the implant, follow-up periods, and complications associated with pegs and implants were recorded. Group 1 patients received a Vicryl mesh-wrapped implant without a scleral patch graft. Group 2 patients received anterior capping with a scleral patch on the Vicryl mesh-wrapped implant. RESULTS Of 74 identified cases, 12 were excluded for insufficient follow-up. The 62 remaining cases had more than a two-year follow-up. There were two implant exposures (12%, two of 17) in group 1. Retroauricular myoperiosteal graft and scleral patch were used to repair exposed implants successfully. No exposure was noted in group 2 (n = 45). A significant between-group difference in exposure rate was found (P = .02). Early conjunctival dehiscence followed by spontaneous healing occurred in three group 2 patients. CONCLUSIONS Scleral patch graft and Vicryl mesh can act as duplicate barriers between anterior surface of implants and overlying soft tissue. The modified wrapping technique prevents porous implants from exposure effectively.

Porous Polyethylene Implants in Orbital Floor Reconstruction

BACKGROUND/PURPOSE Various alloplastic materials are used in orbital wall reconstruction. This study investigated the outcome of patients treated with porous polyethylene sheet implants in the reconstruction of orbital floor fracture. METHODS Twenty-one patients who underwent orbital reconstructions using 0.85-mm porous polyethylene sheets for the repair of orbital floor fracture were included. A transconjunctival approach was used in all patients. The mean duration of postoperative follow-up was 29.7 +/- 12.3 months. Postoperatively, results and complications such as infection and implant extrusion were followed-up on the first day, the first week, monthly for the first 3 months and then every 3-6 months thereafter. RESULTS All 21 patients had symptomatic diplopia before surgery. The diplopia resolved in 14 patients and improved in seven patients within the first month after surgery. All patients except one were free from diplopia at follow-up periods exceeding 6 months. Preoperative enophthalmos resolved in four of seven patients and improved in three. None of the patients developed orbital infection, implant exposure or migration, worsening diplopia, infraorbital anesthesia or loss of vision during follow-up. CONCLUSION The study demonstrated that porous polyethylene implants in the repair of orbital wall fractures had good results with few complications.

Experimental myopia in chickens induced by corneal astigmatism

Abstract Astigmatism has been suggested to be an important factor in the production and/or progression of myopia. Chickens have been used as a myopic animal model for several years. In the present investigation our aim was to evaluate the importance of surgically induced corneal astigmatism by peripheral corneal incision with compression suture in one eye, the right, of 3‐day‐old chicks. Vertical incision (2 mm) with compression suture (nylon 9‐0, one stitch) induces against‐the‐rule astigmatism, horizontal incision with compression induces with‐the‐rule astigmatism. Four groups were studied 1) with one vertical cut, 2) one horizontal cut, 3) two vertical cuts, 4) two horizontal cuts. The eyes were measured by caliper after 8 weeks. Eye enlargements were induced in all groups, however, less by one cut (astigmatism around 5 diopters) than by two cuts (astigmatism 10 diopters, or more). In the latter groups the pattern of equatorial eye enlargement dependend on the axis of the induced astigmatism, the greater elongation being associated with the strongest refracting corneal meridian. All considered, the results suggest that significant corneal astigmatism could be another factor in the production of myopia, possibly acting by way of optical degradation of retinal image quality.

Examining rhodopsin retention in endoplasmic reticulum and intracellular localization in vitro and in vivo by using truncated rhodopsin fragments.

More than 100 mutations of rhodopsin have been identified to be associated with retinitis pigmentosa (RP), and mostly autosomal‐dominant RP (ADRP). The majority of rhodopsin‐associated ADRP is caused by protein misfolding and ER retention. In this study, we aimed to evaluate rhodopsin folding, exiting the ER and intracellular localization through expression of the rhodopsin fragments in COS‐1 cells as well as in the transgenic zebrafish. We cloned human rhodopsin cDNA, which was then divided into the N‐terminal domain, the C‐terminal domain, and the fragment between the N‐ and C‐terminal domains, and examine their intracellular expression in vitro and in vivo. We introduced a point mutation, either F45L or G51V, into this fragment and observed the intracellular localization of these mutants in COS‐1 cells and in the zebrafish. The results revealed all of the truncated rhodopsin fragments except for the C‐terminal domain and the full‐length rhodopsin which had some plasma membrane localization, formed aggregates nearby or within the ER in COS‐1 cells; however, the N‐terminally truncated rhodopsin fragment, the C‐terminal domain, and the full‐length rhodopsin could traffic to the ROS in the zebrafish. Besides, the F45L mutation and the G51Vmutation in the rhodopsin fragment between the N‐ and C‐terminal domains produced different effects on the aggresome formation and the intracellular distribution of the mutants both in vivo and in vitro. This current study provides new information about the mutant rhodopsin as well as in treatment of the RP in humans in the future. J. Cell. Biochem. 112: 520–530, 2011.

Epidemiological Studies on Multiple Risk Factors for Myopia in Taiwan: Gene-Environment Interaction

Myopia is a hyperendemic eye disease in Taiwan showing a rapid increase in prevalence since the early 1950s. In a recent national survey of schoolchildren, the prevalence of myopia was found to increase from 12% at age 6, 54% at age 12 to 85% at age 18. The prevalence was higher in females than males for all age groups. There was a striking difference in myopia prevalence in areas with different degrees of urbanization. Children in rural areas had a lower prevalence than those in urban areas. There was a significant familial aggregation of myopia. Children whose parents were affected with myopia had a higher prevalence of myopia than those without affected parents. The higher the proportion of siblings affected with myopia, the higher the risk of being affected with myopia. There were significant associations with myopia in a dose-response relationship for duration of near-work and sleeping, distance of studying and watching television as well as rank of academic achievement in class. Two twin studies were carried out to differentiate the relative importance of genetic and environmental components in the determination of myopia. Monozygotic (MZ) twins were found to have a higher concordance in myopia than dizygotic (DZ) twins. The concordance in ocular refraction, corneal curvature and axial length was higher in MZ twins than DZ twins. The heritability of the parameters was estimated to range from 0.16 to 0.31. MZ and DZ cotwins with similar studying and reading habits had a higher concordance in myopia than MZ and DZ twins with different studying and reading habits. A significant gene-environment interaction in the determination of myopia has also been observed. However, the etiological mechanism for the development of myopia remains to be elucidated.

The Blood-Aqueous Barrier in Anisometropia and High Myopia

Functional disorder of the blood-ocular barrier has been suggested in cases of degenerative high myopia. Whether the blood-aqueous barrier among young high myopes with healthy vitreous suffers changes is worthy to be explored. Flare density was measured with the laser flare cell meter (Kowa) in highly myopic and anisometropic students. The mean flare density of highly myopic eyes in the myopic group (4.28 +/- 1.13 photon counts/ms) was similar to that of the emmetropic control group (4.24 +/- 1.79 photon counts/ms). Moreover, the difference in flare density between the two eyes of anisometropic patients was not statistically significant. Thus, the blood-aqueous barrier seems intact in young high myopes with healthy posterior vitreous and fundus.