Retinomax K-Plus Research Articles

Refractive errors and visual impairment in 900 adults with intellectual disabilities in the Netherlands.

To collect data on refractive errors and visual impairment in adults with an intellectual disability (ID) in the Netherlands. A randomized sample of 2100 participants was drawn from a base population of 9000 adults with intellectual disabilities in the Netherlands. This article reports on the first 900 participants. All participants underwent a protocol-based on-site ophthalmological assessment carried out by skilled investigators. Co-operation was classified according to the number of tests that could be carried out reliably and was good or excellent in 80% of subjects, average in 13% and poor in 7%. Refraction could be reliably assessed in 505/900 (56%) subjects. There was an increased risk of visual impairment in all subgroups compared to the general Dutch population. Visual acuity (VA) was related to the level of ID, but refractive errors were not. New spectacles were prescribed in 106 cases (12%). Of 374 people in whom both monocular VA and the refractive error of the right eye could be reliably assessed, 153 (41%) had a pretest prescription, 16 (10%) of which we found to be inadequate. Of the 221 participants without a pretest prescription, 41 (19%) benefited from correction. Only 38/84 (45%) subjects aged 50 years or older, who could benefit from correction for near vision, had near spectacles. New correction increased the mean distant VA significantly from 0.44 to 0.65 (p < 0.0005). With some adaptations, visual screening is feasible in a majority of adults with ID. Visual impairment and refractive errors are much more prevalent in adults with ID than in the normal population. Accurate spectacle correction resulted in significant improvement in distant VA.

Astigmatism and Amblyopia among Native American Children (AANAC): design and methods

The overall goal of the AANAC study is to improve detection of astigmatism and prevention of amblyopia in populations with a high prevalence of astigmatism. To meet this goal, the study will evaluate four methods of screening for astigmatism in preschool children and will assess both the short-term and long-term benefits of early correction of astigmatism in improving acuity and preventing amblyopia. This paper presents an overview of the design and methodology of the AANAC study. Subjects are members of the Tohono O'Odham Nation, a Native American tribe with a high prevalence of astigmatism. Preschool-age children who attend Head Start are screened with four tools: the Marco Nidek KM-500 autokeratometer, the MTI photoscreener, the Nikon Retinomax K-Plus autorefractor, and the Lea Symbols acuity chart. Sensitivity and specificity for detection of significant astigmatism, as measured by a technique that uses both cycloplegic retinoscopy and cycloplegic autorefraction, is determined for each of the four screening tools. Presence of amblyopia is evaluated by measurement of best-corrected recognition acuity and acuity for orthogonal gratings. Spectacles are provided to all 3-year-old children with =2.00 diopters (D) of astigmatism and all 4- and 5-year-old children with =1.50 D of astigmatism. Persistence of amblyopia after glasses wearing is evaluated by follow-up measurement of best-corrected recognition acuity and acuity for orthogonal gratings, conducted 2-5 months after glasses are prescribed. Long-term effectiveness of early screening and glasses prescription is evaluated through measurement of recognition acuity in two groups of first-grade children: one group who participated in the Head Start program before the intensive vision screening program was initiated, and a second group who participated in the study's Head Start vision screening program.

Visual acuity screening versus noncycloplegic autorefraction screening for astigmatism in Native American preschool children

Introduction: Visual acuity screening (VAS) is less reliable in preschoolers than in school-aged children as a means of detecting significant refractive error. We wished to compare the effectiveness of VAS with the effectiveness of an objective method, noncycloplegic autorefraction screening (NCARS), in detecting the presence of significant astigmatism warranting spectacle correction. Methods: We examined 245 Native American Head Start registrants aged 3 to 5 years. We attempted to obtain uncorrected visual acuity using Lea Symbols logMAR Chart (Precision Vision Inc, Villa Park, Ill), noncycloplegic autorefraction using the Nikon Retinomax K-plus (Nikon Corp, Melville, NY), and cycloplegic refraction (CR) on each eye. The VAS failure criterion was either a 2-line acuity difference between eyes or acuity worse than 20/40 in either eye. The NCARS and CR failure criterion was the spectacle correction threshold exceeding the 50th percentile on the basis of a survey of AAPOS members. Results: We completed VAS in 96% of children and NCARS and CR in 100% of children. There was high prevalence (31%) of significant astigmatic refractive error in this sample. Ten subjects who did not permit bilateral visual acuity measurements were scored as having a positive test result. The sensitivity and specificity of VAS were 90% and 44%, respectively. NCARS had sensitivity and specificity of 91% and 86%, respectively. NCARS becomes cost-effective after 1044 children are screened, assuming that the cost of the autorefractor is 300 times the cost of the referral examination. Conclusion: VAS offers high sensitivity but suffers from poor specificity. NCARS greatly reduces the number of unnecessary referrals. In this population, NCARS becomes cost-effective after approximately 1000 children are screened. (J AAPOS 1999;3:160-5)

Experiences with the hand-held autorefractometer "Retinomax" in adults and children

A measurement of ametropia with a table-top mounted autorefractor can be difficult or impossible on children--especially when the children are very young or handicapped. A hand-held autorefractor, however, may be successfully applied in some of these problematic cases. Results of comparative measurements are presented concerning the accuracy and applicability of the hand-held autorefractor. The data were obtained on healthy young adults (100 eyes) and children (age 2-10 years, 50 eyes). In the group of adults, the autorefractor readings (obtained with a Retinomax K-plus) were compared with the results of subjective refractions. The effectiveness of the technique to relax accommodation was also evaluated. All children were measured with a Retinomax in cycloplegia. Here, retinoscopy and a conventional autorefractor served as reference methods. The accuracy of measurement was analysed by using the following criteria: "Difference of the spherical equivalents" (delta SA), "difference of the cylinder powers" (delta C), "axis difference" (delta A), and "difference of the cylindrical corrections" (delta CK). a) Adults: On average, the spherical equivalent of the autorefractor was +0.28 D larger than the subjectively obtained value. In 88% of all cases, the difference of the spherical equivalents fell into the interval [-0.25 D, +0.75 D]. delta C and delta A were < or = +/- 0.5 D in 95% and 87% respectively. b) Children: When compared with retinoscopy, delta SA fell into the interval [-0.25 D, +0.75 D] in 72% of all cases. delta C and delta A were < or = +/- 0.5 D in 86% and 87% respectively. The accuracy of measurement of the handheld autorefractor is comparable to conventional table-top autorefractors. As it is also applicable in some problematic cases, such as small children, on whom objective refraction data can not be obtained with ordinary autorefractors, it seems to be a valuable addition to the existing set of ophthalmic refraction devices.