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.

Laser flare-cell meter analysis of blood-aqueous barrier functional status in a patient with crystalline retinopathy

This is the first report in the literature of the application of a laser flare-cell meter to examine the functional status of the blood-aqueous barrier in a patient with crystalline retinopathy. The patient, a 34-year-old man with typical crystalline retinopathy, had crystal deposits scattered throughout the posterior pole of the fundus in both eyes. Fluorescein angiography showed atrophy of the retinal pigment epithelium and geographic areas of choriocapillaris atrophy in the posterior pole. Electroretinography showed subnormal amplitude, and the light-peak/dark-trough ratio of the electrooculogram was reduced. Laser photometry showed an increase in the aqueous flare intensity in both eyes, compared with normal values obtained from healthy control subjects. The increase in the aqueous flare intensity in this patient indicates that the function of the blood-aqueous barrier might have been affected in crystalline retinopathy.

Anterior chamber angles shallowing and intraocular pressure after topical pilocarpine

Pilocarpine has been well recognized as the drug of choice for acute angle-closure glaucoma. The purpose of this study is to clarify quantitatively the change of anterior chamber angle and depth with the passage of time after pilocarpine drop administration. Chamber angles of the four quadrants and chamber depths were measured in 18 normal subjects by Scheimpflug Video Image prior to and 30, 60, and 180 minutes after administration of one drop of 4% pilocarpine in one eye, while the opposite eye served as control. The anterior chamber angle and depth showed a significant shallowing at 30, 60 and 180 minutes after 4% pilocarpine administration with a maximal effect of -3.61 degrees and -0.15 mm at 30 minutes, respectively, while the reduction of intraocular pressure reached its maximal effect at 180 minutes. These facts should be well understood in the treatment of angle-closure glaucoma.

Vitreous fluorophotometry in patients with crystalline retinopathy

Patients with various stages of crystalline retinopathy were examined with vitreous fluorophotometry and the results were compared with those of normal subjects. Two patients with glistening crystals without pigment clumps, together with atrophy of the retinal pigment epithelium in the posterior pole, showed a normal inward permeability of fluorescein. Three patients with a large area of choriocapillaris atrophy in the posterior pole, in addition to atrophy of retinal pigment epithelium, demonstrated an increase in the rate of inward fluorescein penetration. Three patients with extensive areas of choriocapillaris atrophy throughout the fundus also revealed an increased posterior vitreous penetration ratio.

Indocyanine green videoangiography of choroidal neovascular membrane in age-related macular degeneration

Fluorescein angiography is the traditional tool for the detection of choroidal neovascularization of age-related macular degeneration. However, some limitations exist which impede its efficacy in the detection of subretinal neovascularization. Indocyanine green videoangiography is a recently developed technique which differs from fluorescein angiography in many ways. We performed indocyanine green videoangiography in 18 eyes with occult choroidal neovascularization, demonstrated by fluorescein angiography. Sixteen of the 18 eyes showed an abnormal vessel loop in the early phase of indocyanine green videoangiography. In the late phase, all 18 eyes had abnormal dye retention around the suspected neovascular area; however, only 12 eyes revealed a distinct border of neovascularization. No side effects, such as nausea, vomiting, or allergic reactions, were noted in our patients. Advantages and drawbacks of indocyanine green videoangiography in comparison with fluorescein angiography are discussed.