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The multi-ethnic pediatric eye disease study: design and methods.

PURPOSE: To summarize the study design of the Multi-Ethnic Pediatric Eye Disease Study (MEPEDS). METHODS: The objectives of the MEPEDS are to: (1) estimate age- and ethnicity-specific prevalence of strabismus, amblyopia, and refractive error; (2) evaluate the association of selected risk factors with these ocular disorders; and (3) evaluate the association of ocular conditions on limitations in health-related functional status in a population-based sample of 12,000 children aged 6-72 months from four ethnic groups--African-American, Asian-American, Hispanics/Latinos and non-Hispanic White. Each eligible child undergoes an eye examination, which includes an interview with his/her parent. The interview includes an assessment of demographic, behavioral, biological, and ocular risk factors and health-related functional status. The examination includes fixation preference testing, visual acuity, stereoacuity, axial length measurement, cycloplegic refraction, keratometry, eye alignment, and anterior and posterior segment examination.

Amblyopia↗

Screening for amblyopia in preschool children: results of a population-based, randomised controlled trial. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood.

INTRODUCTION: The rationale for preschool vision screening programmes has recently been questioned. Evidence about the effects of early treatment is needed, but it is not known how early the target conditions can reliably be detected. In this study, an intensive programme comprising several different screening methods, used at different ages up to 37 months, was compared with the usual practice of visual surveillance and ad hoc referrals. METHODS: Two groups were randomly selected from children in a population birth cohort study. The control group (n = 1461) received visual surveillance only. The intervention group (n = 2029) was offered in addition a programme of regular visual assessments by orthoptists testing visual acuity, ocular alignment, stereopsis and non-cycloplegic photorefraction. RESULTS: The intervention group programme yielded more children with amblyopia (1.6% vs. 0.5%, p < 0.01), and was more specific (95% vs. 92%, p < 0.01), than the control programme. The individual components of the intervention programme were compared. The cover test and visual acuity tests were poorly sensitive until the children were 37 months, but were always >99% specific. Photorefraction was more sensitive than acuity testing at all ages below 37 months, with specificity >95% at 31 and 37 months. CONCLUSIONS: Photorefraction would have detected more children less than 37 months of age with straight-eyed amblyopia than did visual acuity testing, but with more false positives. At 37 months, photorefraction plus a cover test would have been comparable in effectiveness to visual acuity testing plus a cover test.

Amblyopia↗

Ophthalmic manifestations of Sanjad-Sakati syndrome.

BACKGROUND: Sanjad-Sakati syndrome (SSS) is a rare disorder characterized by hypoparathyroidism, growth and developmental delay, and dysmorphism. The purpose of this report is to describe the ophthalmic manifestations of Sanjad-Sakati syndrome (SSS; hypoparathyroidism-mental retardation-dysmorphism syndrome, HRD) (OMIM 241410). PATIENTS: We included a total of 17 patients who were seen at two hospitals in Riyadh. METHODS: Each patient underwent a complete ophthalmologic evaluation including visual acuity assessment, orthoptic workup, slit-lamp biomicroscopy, intraocular pressure measurement, cycloplegic retinoscopy, funduscopy, corneal diameter, and axial length measurement. RESULTS: All 17 (100%) of the patients had normal visual acuity. All patients had microphthalmia with normal intraocular pressure. Eight (47%) of the patients had esotropia and four (23%) had exotropia. Ophthalmoscopy revealed tortuous retinal blood vessels in all patients. Hyperopic astigmatism was present in 16 (94%) patients. CONCLUSION: Patients with SSS display a variety of ocular findings including errors of refraction, strabismus, and retinal vascular tortuousity.

Adolescent↗

Genomewide linkage scan for myopia susceptibility loci among Ashkenazi Jewish families shows evidence of linkage on chromosome 22q12.

Mild/moderate (common) myopia is a very common disorder, with both genetic and environmental influences. The environmental factors are related to near work and can be measured. There are no known genetic loci for common myopia. Our goal is to find evidence for a myopia susceptibility gene causing common myopia. Cycloplegic and manifest refraction were performed on 44 large American families of Ashkenazi Jewish descent, each with at least two affected siblings. Individuals with at least -1.00 diopter or lower in each meridian of both eyes were classified as myopic. Microsatellite genotyping with 387 markers was performed by the Center for Inherited Disease Research. Linkage analyses were conducted with parametric and nonparametric methods by use of 12 different penetrance models. The family-based association test was used for an association scan. A maximum multipoint parametric heterogeneity LOD (HLOD) score of 3.54 was observed at marker D22S685, and nonparametric linkage analyses gave consistent results, with a P value of.0002 at this marker. The parametric multipoint HLOD scores exceeded 3.0 for a 4-cM interval, and significant evidence of genetic heterogeneity was observed. This genomewide scan is the first step toward identifying a gene on chromosome 22 with an influence on common myopia. At present, we are following up our linkage results on chromosome 22 with a dense map of >1,500 single-nucleotide-polymorphism markers for fine mapping and association analyses. Identification of a susceptibility locus in this region may eventually lead to a better understanding of gene-environment interactions in the causation of this complex trait.

Alleles↗

Effects of nitric oxide donors and nitric oxide synthase substrates on ciliary muscle contracted by carbachol and endothelin for possible use in myopia prevention.

Research has suggested that the development of myopia may possibly be prevented by the use of drugs which facilitate relaxation of the intraocular ciliary muscle. We examined the effects of five nitric oxide-producing agents--two nitric oxide donors, hydralazine and sodium nitrite, and three nitric oxide synthase substrates, L-arginine, L-canavanine, and N-benzoyl-L-arginine ethyl ester--on isolated bovine ciliary muscle maximally contracted with either carbachol or endothelin-1. Of these agents, hydralazine and L-canavanine produced a relaxing effect on endothelin-1-contracted muscle that was significantly greater than relaxing effect on carbachol-contracted muscle. These results indicate that hydralazine and L-canavanine could possibly be used for the prevention of myopia by relaxing the ciliary muscle with few anticholinergic and cycloplegic side effects.

Animals↗

The effectiveness of 0.5% atropine in controlling high myopia in children.

Twenty highly myopic children (> or = -6.0 D) were treated with 0.5% atropine eyedrops once per night. Twelve subjects were initially treated with a short-acting cycloplegic agent, tropicamide (0.5%) (Group A), and the other eight subjects did not receive any myopic therapy before atropine (Group B). These cases were followed for up to five years. In Group A, the mean myopic progression rate after 0.5% atropine treatment was -0.01 +/- 0.04 D/M (Diopter/Month), which was significantly lower than that of the period during tropicamide treatment (-0.12 +/- 0.09 D/M) (p < 0.05). In Group B, the mean myopic progression rate after atropine therapy was begun was -0.04 +/- 0.06 D/M, which was also significantly slower than that of non-medication, -0.14 +/- 0.07 D/M (p < 0.05). The results suggested that 0.5% atropine is effective for slowing down myopic progression, even in highly myopic children.

Administration, Topical↗

Mycobacterium avium complex infection, rifabutin, and uveitis--is there a connection?

Rifabutin, an antimycobacterial agent, has been recommended by the U.S. Public Health Service as prophylaxis against infection due to Mycobacterium avium complex (MAC) in patients with AIDS. When rifabutin is administered as prophylaxis, uveitis has been reported only rarely. However, uveitis has been reported in two studies in which rifabutin was administered at higher doses in combination with an azole, a macrolide, or both for treatment of disseminated MAC infection. The uveitis that has been reported has been predominantly anterior and mild-to-moderate in nature, although severe hypopyon uveitis has occasionally been reported. No etiologic infectious agent has been isolated from any of these patients, and treatment with topical steroids and cycloplegics usually leads to rapid resolution of the uveitis. It is necessary to discontinue prophylaxis or therapy with rifabutin only in cases of uveitis that are refractory to treatment or when the uveitis recurs. Immunologic factors, rather than direct drug toxicity, appear to be the most likely explanation for the occurrence of uveitis in patients receiving rifabutin; however, further study is required to elucidate the mechanisms involved.

AIDS-Related Opportunistic Infections↗

The effect of cycloplegia on the determination of refractive error by the Ophthalmetron.

The Ophthalmetron was used to measure the refractive error of 10 male optometry students. Although there was a high incidence of invalid readings, more repeatable results were obtained with use of a cycloplegic. Measurements made under cycloplegia revealed 0.41 D more hyperopia but no differences in astigmatism as compared to the noncycloplegic refraction. Instrument myopia was shown not to be a factor.

Accommodation, Ocular↗

Plus lenses, prisms, and bifocal effects on myopia progression in military students.

Students of the Naval Academy Preparatory School (NAPS) class of 1978 to 1979 were randomly divided into three groups, one-third of the class receiving their correlation for distant vision with a no. 1 pink tint to be used for reading (the placebo group); one-third of the class receiving +1.25 D added to their distance correction with 2 delta base-in each eye, in glasses to be used for reading; and one-third of the class receiving bifocals, incorporating their distance correction with a +1.50 D near addition. The refractive error at distance for all 232 students was determined under cycloplegia. At the end of 5 months, a repeat cycloplegic refraction showed nonsignificant myopic shifts (Wilcoxon test) of -0.08 +/- 0.29 D in the placebo group, -0.07 +/- 0.25 D in the plus-with-prism group, and -0.06 +/- 0.18 D in the bifocal group. This research note is preliminary to a followup at academic graduation of these same students from the Naval Academy in 1983.

Adolescent↗

Ultrasound measures of vitreous chamber depth during ocular accommodation.

The vitreous chamber decreased in depth about 0.12 mm as accommodative demand increased from 0.2 to 7 D in nine accommodative steps. The depth decreases matched movement of the posterior lens surface toward the retina. Accommodation caused no significant increases in axial length compared to cyclopleged controls. These results do not favor the active role for the vitreous in accommodation proposed by Coleman in 1970. Computer analysis of A-scan interval counts demonstrated that multiple retinal complex peaks might erroneously point to vitreous or axial lengthening. About 30% of total lens thickening during accommodation was accounted for by posterior lens surface displacement.

Accommodation, Ocular↗

Does prior instillation of a topical anesthetic enhance the effect of tropicamide?

Preinstillation of a topical anesthetic has been reported to increase the effect of subsequently applied mydriatics. We examined the effect of instilling 1 drop of proparacaine hydrochloride (0.5%) before applying 1 drop of tropicamide (1%). The results show that preanesthesia prolongs the mydriatic and the cycloplegic effects of tropicamide in eyes with either lightly or more heavily pigmented irides.

Accommodation, Ocular↗

How the method used to measure refractive error is expected to affect statistical results.

Values of refractive error (RE) observed for subjects and groups depend on the degree to which the measurement method used relaxes accommodation. This affects statistics calculated on RE measurements in predictable ways. Comparing noncycloplegic (NC) with cycloplegic (C) methods, myopia is expected to be more frequent, differences between group means should be less, and correlations and regressions relating RE to other variables may be reduced slightly. Tests based on the categorization of RE will show weaker associations with putative influencing variables. The implications of this are discussed for comparing published studies and choosing measurement methods in epidemiological and genetic studies.

Humans↗

Time course of cycloplegia induced by a new phenylephrine-tropicamide combination drug.

A motorized and computer-interfaced phoropter was used to track the development of cycloplegia and recovery of accommodation over a 60-min period, after the topical application of a phenylephrine 5%-tropicamide 0.8% drug combination (Phenyltrope). Phenyltrope was introduced into the Canadian market about 2 years ago (Compendium of Pharmaceuticals and Specialties, 1987), and advertised as a fast acting cycloplegic and mydriatic drug. Here we report the results of our investigation of the depth of action and the temporal aspects of cycloplegia for this drug combination as a function of iris color. We also compare the action spectrum of Phenyltrope to that of tropicamide 1% under similar test conditions. Our results indicate that the latency for cycloplegia was shorter for tropicamide, the maximum rate of accommodative loss similar for both drugs, and the resultant cycloplegia at 20 min deeper for Phenyltrope. Recovery from induced cycloplegia was greater for tropicamide 60 min after drug administration. For both Phenyltrope and tropicamide, no significant differences in any of the parameters investigated were observed as a function of iris color. We conclude that even though Phenyltrope induced a measurably deeper cycloplegia than did tropicamide, the amount of residual accommodation present at 20 min (about 38%) is insufficient for most refractive purposes.

Accommodation, Ocular↗

Evaluation of accommotrac biofeedback training for myopia control.

A new treatment for myopia, biofeedback training for control of accommodation, has been proposed and developed over the past decade. Various reports in the literature show marked inconsistencies in the results of such treatment. A double-masked study with experimental and control groups of 15 subjects each was designed to obtain a definitive answer concerning the efficacy of this method. The parameters evaluated were visual acuity, cycloplegic and noncycloplegic retinoscopy, subjective refraction, amplitude of accommodation, and flexibility of accommodation. In all categories no significant difference was found between the control and experimental subjects. The consequences of these findings are discussed as to the benefit of treatments using this method and avenues to explore in future studies.

Accommodation, Ocular↗

Subjective and objective assessment of soft bifocal contact lens performance.

Subjective and objective techniques were used to assess the on-eye performance of soft bifocal contact lenses. In the subjective technique a young observer whose accommodation had been paralyzed with a cycloplegic agent was fitted with the contact lens type under investigation and aligned with a Maxwellian view Badal optometer using a bite-bar. Visual acuity was measured as a function of both target vergence (0.00 to -4.00 D) and pupil size (1 to 5 mm). Aspheric, concentric, and diffractive soft bifocal contact lens designs were investigated. Diffractive and concentric bifocal designs with +2.00 D near additions showed "twin peaks" of visual acuity with one peak at 0.00 D target vergence (equivalent to distance viewing) and the second at -2.00 D target vergence (equivalent to a target at 50 cm). Some aspheric designs produced a relatively constant visual acuity across this vergence range, whereas others gave poor acuity at near. Visual acuity with the Echelon diffractive lens was relatively unaffected by pupil size, confirming theoretical predictions. Visual acuity with concentric designs was also relatively free of pupil size effects. In the objective technique, the variation in surface power across the lens was assessed using video-keratography. This technique provided an elegant means of visualizing the power profile of the lens. The location of the zones of increased power and the magnitude of power variations allowed an accurate prediction of the visual performance measured subjectively. Temporal displacement of lenses may explain the occasions where visual performance did not vary with pupil size.

Accommodation, Ocular↗

Dapiprazole's effect upon accommodative recovery: is it due entirely to changes in depth of field?

We conducted a study to evaluate the ability of dapiprazole 0.5% ophthalmic solution to reverse accommodative loss brought about by mydriatic drugs having mild cycloplegic effects. To accomplish this, we analyzed data from several earlier randomized, masked clinical studies. Our composite data include over 90 subjects dilated with tropicamide. Tropicamide was used alone in 1% concentration, as well as in combination with phenylephrine, 2.5% and in the proprietary preparation, Paremyd (Allergan Pharmaceuticals). Accommodative amplitude and pupillary diameter were measured before instilling dilating drops and then again one-half hour later, immediately before instilling either dapiprazole or a placebo. Accommodative amplitude and pupil diameter measurements were then repeated four more times, on both the treatment and control eyes and at 30, 60, 120, and 180 min after instillation of the last drop of dapiprazole or placebo. We found accelerated "accommodative" recovery with dapiprazole for each of the three tropicamide-containing drugs used in our study. This is not surprising because some recovery of accommodative amplitude after dapiprazole's administration is expected. This is because dapiprazole accelerates pupillary recovery and a narrowing of the pupil gives rise to an increase in ocular depth of field. Rate of accommodative recovery with dapiprazole was found not to be significantly different for all three tropicamide-containing preparations tested (p > 0.05). Does dapiprazole produce improvement in amplitude of accommodation beyond that attributable to increased depth of field?(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗

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.

Adolescent↗

Corneal aberrations increase with the magnitude of radial keratotomy refractive correction.

BACKGROUND: Refractive surgery induces optically abrupt changes in shape in the midperiphery of the cornea. The abruptness of this change is in part dependent on the magnitude of the surgically induced refractive change. Therefore, the optical aberrations of the cornea, as quantified by wavefront variance (WFV), may be expected to increase as the surgically induced change in the refraction increases. PURPOSE: It is the purpose of this study to test the hypothesis that as the surgery-induced change in refraction increases, so does the WFV of the cornea. METHODS: Fourteen radial keratotomy (RK) patients and seven normal patients served as subjects. Measurements were made before and 2 years after RK surgery. To quantify the WFV of the cornea, we used corneal topography measurements to calculate the surgically induced change in corneal WFV with respect to two different reference surfaces, a sphere and the presurgical cornea. To quantify the surgically induced change in the equivalent spherical correction (ESC), cycloplegic refractions were performed. The measurements were summarized by regressing the surgically induced change in the WFV against the surgically induced change in the ESC. RESULTS: For large pupils (7 mm diameter), the correlation between the change in the WFV referenced to a sphere and the change in the ESC was significant (p < 0.0001, r2 = 0.745) and dominated by fourth order aberrations. Similar results were found for the surgical lens. For small pupils (3 mm diameter), the effects were markedly reduced. CONCLUSIONS: (1) As the magnitude of the surgically induced refractive change increases so does the WFV of the cornea, particularly for large pupils. (2) The increase in corneal WFV for large pupils is dominated by fourth order aberrations. (3) The increase in corneal WFV is consistent with reported decreases in visual function (contrast sensitivity and low contrast visual acuity), particularly for large pupil diameters in combination with large surgically induced changes in refractive error.

Cornea↗