Identification of red–green colour deficiency: sensitivity of the Ishihara and American Optical Company (Hard,Rand and Rittler) pseudo‐isochromatic plates to identify slight anomalous trichromatism

Screening sensitivity, based on a specific number of errors, of the Ishihara plates and of the American Optical Company (Hardy, Rand and Rittler) plates (HRR plates) was determined by reviewing data obtained for 486 male anomalous trichromats identified and classified with the Nagel anomaloscope. Data were obtained for the 16 screening plates, with Transformation and Vanishing numeral designs, of the 38 plate Ishihara test, and for the four red–green screening plates (with six Vanishing designs) of the HRR test. Sensitivity of the Ishihara plates was found to be 97.7% on 4 errors and 98.4% on 3 errors. Only anomalous trichromats with slight deficiency, according to the anomaloscope matching range, made 8 errors or fewer. One screening error, a single missed figure, is normally allowed as a pass on the HRR test and 3 errors is often recommended as the fail criterion to eliminate false positive results. Twenty‐three subjects made no error on the HRR screening plates and 12 subjects made a single error (35 anomalous trichromats). Screening sensitivity was therefore 92.8% using 2 errors as the fail criterion. Screening sensitivity was reduced to 87% when 3 errors was the fail criterion, and some deuteranomalous trichromats with moderate deficiency, according to the anomaloscope matching range, were not identified. Individuals who make a maximum of 2 errors on the HRR test, or on the Richmond HRR 4th Edition, should be re‐examined with the Ishihara plates to determine their colour vision status. The present review confirms that the Ishihara test is a very sensitive screening test and identifies people with slight anomalous trichromatism. The HRR test is unsatisfactory for screening and should not be chosen solely for this purpose.     

RetCam imaging for retinopathy of prematurity screening.

PURPOSE: Indirect ophthalmoscopy is the gold standard for retinopathy of prematurity (ROP) screening. Screening for ROP with digital imaging has been proposed as a possible alternative. Our goal was to evaluate the longitudinal clinical outcomes of employing digital imaging to detect high-risk ROP. METHODS: Serial RetCam imaging and indirect ophthalmoscopy were performed on 43 premature infants. A masked reader evaluated the images and made management recommendations that were compared with indirect ophthalmoscopy results. Successful screening was determined by correctly identifying progression to prethreshold or threshold disease with referral for indirect ophthalmoscopy. Unsuccessful screening was determined by failure to identify prethreshold or threshold disease, inaccurately detecting prethreshold or threshold disease, or inability to evaluate for ROP. RESULTS: No cases of prethreshold or threshold disease were missed by the reader. The reader overestimated prethreshold or threshold disease in 5% of cases. Initial screening in 21% of cases could not be evaluated for ROP secondary to poor image quality. Digital photography had a sensitivity of 100% and specificity of 97.5% in detecting prethreshold and threshold ROP. Positive-predictive value of digital photography was 67% and negative-predictive value was 100%. CONCLUSIONS: Screening and management of ROP using RetCam imaging did not fail to detect prethreshold or threshold disease when images could be obtained. Ophthalmologic examinations were needed in 20% of cases that did not reach threshold or prethreshold disease because of poor image quality or overestimation of ROP. RetCam screening may safely reduce the overall number of indirect ophthalmologic examinations required.     

Gesundheitsökonomische Aspekte des Glaukomscreenings

Purpose

Screening for glaucoma can detect undiagnosed patients, and treatment can prevent blindness. There are defined criteria for screening programs, but economic aspects of screening programs and cost utility estimations are of increasing importance.

Methods

Medical databases (CDSR, HTA, MEDLINE, EMBASE) were searched on the topics of glaucoma screening, screening strategies and tools, and relevant health-economic analyses for glaucoma screening. In this article, the most important findings are presented and discussed using epidemiological data.

Results

Glaucoma screening meets most of the relevant criteria for screening strategies. The best single screening test at this time is the frequency doubling technique. The cost-effectiveness depends mainly on the prevalence of the disease, the specificity of the screening test, the costs of screening and disease, and the impairment of quality of life due to glaucoma. Two recently published cost utility studies from Finland and the United Kingdom are presented. A common result is that a population screening is not cost-effective, whereas targeted screening of high-risk groups is.

Conclusion

Glaucoma screening of the general population is not cost-effective, but screening of groups at risk (e.g., those of a certain age, family history, or ethnicity) may be cost-effective. Clear cutoff points regarding whom to screen can be determined by economic analyses using high-quality data. These data influence health policy decision makers.     

Negative predictive value of a population-based preschool vision screening program.

BACKGROUND: The Enhanced Vision Screening Program is a population-based vision screening program that has, at present, examined 59,782 children. Its main goal is to detect amblyopia, strabismus, and high refractive errors. An average of 11,910 4 1/2- to 5 1/2-year-old children are screened yearly. The current study determines the negative predictive value of the screening program: For a subject having passed the vision screening test, what is the probability of not having amblyopia, strabismus, or high refractive errors? METHODS: Of the 11,734 subjects who passed the vision screening, 200 were randomly chosen to undergo a strictly defined gold standard examination by an orthoptist and an ophthalmologist. RESULTS: Of the 200 randomly chosen subjects, 157 underwent the gold standard evaluation. The negative predictive value of the Enhanced Vision Screening Program was 97.6% for any potentially vision-threatening ocular condition. It was 98.7% if we considered only the visually significant ocular problems that the test was designed to detect. CONCLUSION: Because the negative predictive value of the Enhanced Vision Screening Program is not 100%, some children with amblyopia, strabismus, or refractive errors are missed. Occasionally, a rare, potentially vision-threatening condition may go undetected. Parents should be made aware of this when they receive the results of the vision screening.     

Congenital Color Blindness in Young Turkish Men

Purpose: The purpose of this analysis was to investigate the reliability of visual acuity screening and measurements made under field conditions when standardization of all test conditions is not possible.

Setting and Methods: In the Washington County Follow-Up Eye Study conducted in 1985 among cases of ocular histoplasmosis and controls from the same community who had been selected in 1970, a primary goal was to obtain a current visual acuity measurement of each eye of each participant in order to assess 15-year changes in visual acuity. Both visual acuity screening and measurement were accomplished on two separate occasions and in two separate locations (home or workplace and clinic) for 308 eyes and 317 eyes, respectively, of 161 participants. Screening was used to classify the visual acuity as 20/40 or better, worse than 20/40 but at least 20/160, or worse than 20/160. Screening and measurement were accomplished on at least one occasion for the eyes of 192 of 216 eligible individuals.

Results: Among 308 eyes screened twice, 289 (94%) were classified identically (k?=0.80). Among 317 eyes with visual acuity measured on two occasions, the measurements were within two lines for 305 eyes (96%; k? = 0.50). Among eyes for which classifications of visual acuity from screening and measurement could be compared, 325 (96%) of 340 assessed at home and 326 (96%) of 338 assessed in clinic were classified in the same way (k? = 0.86 and 0.88, respectively).

Conclusion: Despite the unavoidable lack of standardization of test conditions when visual acuity was screened and measured in the home or workplace, the results were highly reliable when compared with visual acuity testing in the clinic under standard conditions.     

Longitudinal study of a cohort of people with diabetes screened by the Exeter Diabetic Retinopathy Screening Programme

PURPOSE: To evaluate the long-term outcome of a cohort of people with diabetes screened by the Exeter Diabetic Retinopathy Screening Programme. METHOD: The cohort comprised of diabetic patients from nine market town General Practices around Exeter who first attended the diabetic retinopathy screening programme in 1992. Screening was carried out by a combination of dilated fundoscopy by a screening technician and a single 45 degrees Polaroid photograph of each eye. The prevalence of diabetic retinopathy at the baseline, the incidence of sight threatening diabetic retinopathy (STDR) in the next two rounds of screenings, and the long-term visual outcome are described. RESULTS: The cohort consisted of 775 patients (104 Type I, 517 Type II non-insulin-requiring and 154 Type II insulin-requiring). The mean age was 72.1 years (15-100), with mean disease duration of 13.0 years (1-79). Baseline prevalence was as follows: background retinopathy: 21.4%, proliferative: 2.8%, clinically significant macular oedema: 6.1%. The incidence of proliferative disease was 2.20% and 2.25% respectively in the next two rounds of screening (P > 0.05, chi2 test). The incidence of clinically significant macular oedema was also constant over next two rounds of screening, at 4.79% and 5.18% respectively (P > 0.05, chi2 test). Ninety-five (12.3%) patients were deceased and a further 179 (23%) patients were lost to follow-up by the third round. Only two patients with newly diagnosed STDR suffered deterioration of visual acuity to 6/60 or worse as a result of diabetic retinopathy. CONCLUSION: The incidence of STDR remained constant throughout the period of screening, reflecting the chronic progressive nature of the disease. Significant numbers of patients were lost to follow-up. Screening seemed effective in preserving vision in those patients with newly diagnosed STDR.     

原发性闭角型青光眼筛检方案的优化研究

目的：应用成本一效果分析的原理进行评价原发性产角青光眼不同筛检试验组成的筛检方案，从中选择出最优方案。方法：根据文献及我们研究的结果建立筛检模型及模型计算所需的参数，然后将手电筒侧照法、前房轴深、周边前房深度及手电筒侧照十周边前房深度串联法皲种筛检方法引入筛检模型的计算机程序进行计算，得出各种筛检方案筛检、诊断和治疗的成本；筛检出的病人多获得的质量调整寿命年。在这个基础上进行各种筛检方案的成本－效     

The value of screening for glaucoma with tonometry

This paper estimates the value of performing Schiotz tonometry to detect glaucoma in an asymptomatic patient. About 9% of adults over 40 will be found on a single Schiotz tonometry test to have elevated intraocular pressure (IOP). On work-up, about 1 out of 50 of these individuals with high IOP will be found to have glaucoma. Tonometry, however, will miss about half of all patients with glaucoma because they do not have elevated IOPs at the time of the test. Pilocarpine or epinephrine are the most commonly used drugs to treat the disease, but they are not always effective in lowering a patient's IOP or in stopping the progression of field defects. From the available evidence it does not appear that earlier diagnosis makes a substantial difference in the patient's outcome. If all individuals over 40 years of age in a city of 1,000,000 were screened, the total cost of finding and treating about 484 people with chronic simple glaucoma would be on the order of $4,944,866 or about $13,000 per patient potentially benefited. Screening with tonometry does not appear to be warranted.     

Evaluation of screening schemes for eye disease in a primary care setting

Background and purpose: Screening in a primary care setting could be an effective method for detection of eye disease. This study was designed to evaluate a questionnaire and a battery of tests for their performance in eye disease screening at a primary care clinic. Methods: 405 patients aged 40 years or older were interviewed and received a comprehensive eye examination including visual acuity and visual field testing, tonometry, slit-lamp examination, dilated fundus examination and photography. Sensitivity and specificity for the identification of eye disease were calculated for each test and various combinations of tests. Results: A questionnaire-based algorithm for detection of overall eye disease was sufficiently sensitive (90%) but less specific (44%) than an ideal screening test. Distance visual acuity with presenting correction of =20/40 had a sensitivity of 61% and specificity of 72%. A dilated fundus examination had a sensitivity of 79% and specificity of 82%. In screening for glaucoma, tonometry was ineffective (sensitivity=27% and specificity=96%), while visual field testing by suprathreshold screening had a sensitivity of 70% and specificity of 67%. Among a variety of combinations, a two-stage strategy with the questionnaire as a first-stage and visual acuity and ophthalmoscopy as second-stage tests provided the best balance of sensitivity (83%) and specificity (76%). Conclusion: Among currently available ophthalmic tests, an eye examination including a thorough fundus examination is critical in detection of eye disease. A five-item questionnaire may be useful to identify patients at high risk in primary care practice. More effective tests are needed to improve performance of eye disease screening.     

Performance of the 24-2-5 frequency doubling technology screening test: a prospective case study

AIM: To evaluate the performance of the frequency doubling technology (FDT) 24-2-5 screening test by comparison with the established N-30-5 FDT screening test for detection of glaucoma. METHOD: A prospective random sample of individuals referred for possible glaucoma were tested with FDT screening tests 24-2-5 and N-30-5 using the Humphrey Matrix perimeter in addition to standard clinical examination relevant to glaucoma detection. Discriminatory power, reliability and test time of these tests were assessed and compared. The case definition for glaucoma was made by patient according to the established clinical diagnosis. RESULTS: Of 63 referred eligible individuals, 53 (84%) were recruited. Sensitivity and specificity for the N-30-5 screening test was 78 and 85% respectively, compared with 83% and 75% for the 24-2-5 with areas under a receiver operator characteristic curve being 0.87 and 0.92. Differences between these indices were not statistically significant. For a specificity of 95%, sensitivity values were 76% and 56% for the 24-2-5 and N-30-5 respectively. Mean (standard deviation) test duration for the FDT 24-2-5 and N-30-5 screening tests were 111 (13) and 39 (10) seconds respectively (p<0.001). A total of 19 subjects (36%) produced unreliable test results in one or both eyes when tested with the 24-2-5 screening test compared with 5 subjects (9%) with the N-30-5 (p<0.0005). CONCLUSION: Minimal discriminatory power differences existed between the two screening tests evaluated, with both screening tests exhibiting high discriminatory power for detection of individuals with glaucoma. More individuals produced unreliable results on the 24-2-5 screening, which also took longer to perform.     

The results of screening frequency doubling technology perimetry in different locations of the community

PURPOSE: To determine the effect of screening location on the frequency of abnormal test results with Frequency Doubling Technology (FDT) perimetry. DESIGN: Retrospective cross-sectional study. METHODS: The Vision Screening Outreach Project conducted FDT testing in community sites surrounding Portland, Oregon. The sites were separated into a specific location type: health care clinics, work sites, senior centers, festivals/fairs, food banks/shelters, and other locations. These locations were compared for differences in the proportion of screening failures. MAIN OUTCOME MEASURES: Screening failure (defined as a repeatable, abnormal FDT result in either eye). RESULTS: There were 9052 participants from 211 locations in Oregon and Washington. On initial FDT testing, the right and left eye had abnormal results in 18% (1654/9052) and 21% (1918/9052) of participants. Of those with abnormal FDT results, approximately 30% of eyes reverted to normal on repeat testing. Overall, 13% of participants were screening failures. Screening failure was highly associated with age (P<0.001). After controlling for age, participants at senior centers (P<0.001) were most likely to be screening failures and participants at work sites (P=0.006) were least likely to be screening failures when compared with health clinics. CONCLUSIONS: An investigator should repeat an initially abnormal FDT result when screening with FDT. Age and the location of testing influence the probability of a screening failure. Screening in senior centers is most likely to result in screening failure. However, only a randomized controlled trial can determine the true benefit of FDT screening in these locations.     

Up-dated ophthalmological screening and follow-up management for long-term antimalarial treatment

The early detection of macular toxicity linked to long-term antimalarial treatment requires regular ophthalmological screening based on patients'classification based on their results compared to successive controls. Patients are classified as "low risk" with screening every 18 months if all of the following criteria are met: age under 65 years, no associated renal, hepatic or retinal disease, treatment for less than 5 years, dose less than or equal to 6,5mg/kg/d for hydroxychloroquine and 3mg/kg/d for chloroquine (for a lean patient's weight); "at risk, without fundus findings" with screening every 12 months if one of the following criteria is met: age over 65 years (at the start of or during treatment), antimalarial treatment for more than 5 years, daily dose higher than recommended, presence of renal and/or hepatic disease; "at risk, with fundus findings" with screening every 6 months if a retinal dysfunction has been detected and even if treatment is established or followed. Screening consists of an in-depth clinical examination and at least two complementary tests of macular function: color vision (desaturated-Panel-D15 test) and/or static macular perimetry (central 10 degrees) and/or macular electroretinography (pattern ERG/multifocal ERG). If any changes or anomalies are found between two successive check-ups, the state of the retina can be assessed by angiography and global retinal function by full-field-ERG and electro-oculogram (EOG). The progression from one check-up to the next decides whether a course of treatment will be followed.     

The Arden grating test of visual function: a preliminary study of its practicability and application in a rural community in north-west Iran.

In a preliminary study involving 75 normal and 10 abnormal eyes the Arden grating acuity test was assessed under difficult conditions of rural field work. It was found to be adequately sensitive and specific for screening out individuals with visual impairment due to refractive errors or ocular disease, and to distinguish between these. Inexperienced paramedical personnel could carry out the test satisfactorily with no difficulty and with a minimum of training. In spite of the unusually distracting conditions under which the test was carried out 95% of the subjects tested performed satisfactorily. The results of this preliminary study suggest that the Arden grating test is a valuable tool for screening large populations in rural areas of developing countries.     

Effectiveness of vision-screening in pre-school populations with preferential-looking cards used for assessment of visual acuity

Screening the vision of pre-school populations has been suggested as a way to assure early identification of vision problems as well as early intervention, thereby enabling normal development of the visual system and learning process. In a masked investigation, 119 pre-school children enrolled in Project Headstart with a mean age of 3.51 years (range 3 to 5 years) had their vision screened using the Modified Clinical Technique (MCT). Monocular visual acuities in this population were determined using preferential-looking (PL) cards. Visual acuity assessment of young children in screening settings is at best a challenge; yet, all 119 children were able to complete monocular acuity assessments on each eye. Acuities for nonreferrals (individuals who passed the screening) were significantly better than for referrals (individuals who failed the screening) at the 0.0167 level using a two-tailed Fisher's Exact Test with the Bonferroni Method for multiple comparisons. The effectivity of the screening technique as determined by phi-coefficient remained highest (phi = +0.94) with the visual acuity referral criterion set at 6/12 (20/40) or less either eye and/or greater than or equal to a 2-octave difference between the eyes. The resultant referral rate (17.6%) was higher than that predicted by extrapolation from the Orinda Study for this age group (12.3%) but expected because of the different socioeconomic group. PL cards enabled monocular visual acuity measurement on 100% of the children tested and measurably increased the effectiveness of the screening procedure.     

加强原发性青光眼的机会性筛查工作

早期发现和确诊原发性青光眼患者有利于减少青光眼引起的盲和视力损伤.开展机会性筛查工作是更早、更及时地发现原发性青光眼患者的有效方法.机会性筛查是指一些人因为健康体检或者其他问题来眼科就诊时,眼科医师有意识地进行青光眼方面的必要检查而发现的有关青光眼的情况,这应当是眼科临床工作的一部分.由于原发性闭角型青光眼与原发性开角型青光眼是两种不同类型的青光眼,具有明显不同的发病机制和临床特征,因此所采用的机会性筛查方法应当不同.作为眼科医师应当明确认识原发性闭角型青光眼和原发性开角型青光眼的发生和发展是一个连续体的概念,注意筛查试验和诊断试验的重要区别,选择筛查试验方法要力求简便、易行,重视防治青光眼人力资源的开发和应用,这对于做好机会性筛查工作十分重要.     

加强原发性青光眼的机会性筛查工作

早期发现和确诊原发性青光眼患者有利于减少青光眼引起的盲和视力损伤.开展机会性筛查工作是更早、更及时地发现原发性青光眼患者的有效方法.机会性筛查是指一些人因为健康体检或者其他问题来眼科就诊时,眼科医师有意识地进行青光眼方面的必要检查而发现的有关青光眼的情况,这应当是眼科临床工作的一部分.由于原发性闭角型青光眼与原发性开角型青光眼是两种不同类型的青光眼,具有明显不同的发病机制和临床特征,因此所采用的机会性筛查方法应当不同.作为眼科医师应当明确认识原发性闭角型青光眼和原发性开角型青光眼的发生和发展是一个连续体的概念,注意筛查试验和诊断试验的重要区别,选择筛查试验方法要力求简便、易行,重视防治青光眼人力资源的开发和应用,这对于做好机会性筛查工作十分重要.     

加强原发性青光眼的机会性筛查工作

早期发现和确诊原发性青光眼患者有利于减少青光眼引起的盲和视力损伤.开展机会性筛查工作是更早、更及时地发现原发性青光眼患者的有效方法.机会性筛查是指一些人因为健康体检或者其他问题来眼科就诊时,眼科医师有意识地进行青光眼方面的必要检查而发现的有关青光眼的情况,这应当是眼科临床工作的一部分.由于原发性闭角型青光眼与原发性开角型青光眼是两种不同类型的青光眼,具有明显不同的发病机制和临床特征,因此所采用的机会性筛查方法应当不同.作为眼科医师应当明确认识原发性闭角型青光眼和原发性开角型青光眼的发生和发展是一个连续体的概念,注意筛查试验和诊断试验的重要区别,选择筛查试验方法要力求简便、易行,重视防治青光眼人力资源的开发和应用,这对于做好机会性筛查工作十分重要.     

Sensitivity and specificity of tests to detect eye disease in an older population

OBJECTIVE: To compare the ability of tests of visual function to detect the presence of eye disease. DESIGN: Cross-sectional study. PARTICIPANTS: Three thousand six hundred fifty-four of 4433 (82.4%) eligible residents of an area near Sydney aged 49 years and older had a detailed eye examination, including retinal and lens photography and subsequent grading of eye disease, tests of presenting and corrected visual acuity, contrast sensitivity, screening visual field and intraocular pressure. MAIN OUTCOME MEASURES: Receiver operator characteristic (ROC) curves were created and area under the curve compared for each vision test. Sensitivity and specificity were calculated for each test. RESULTS: No single vision test predicted the presence of eye disease with any consistency. Best-corrected visual acuity or contrast sensitivity had the highest area under the ROC curve for most eye diseases examined but had poor sensitivity and specificity. For glaucoma and diabetic retinopathy there was no difference in area under the curve for any of the tests examined, and no test had a good balance of sensitivity and specificity. Screening tests (performed with presenting correction) did not perform as well as nonscreening tests (those carried out after refraction with best correction). CONCLUSIONS: Current vision tests are not particularly good at detecting eye disease compared with the "gold standard" of a full eye examination performed by an ophthalmologist. Further work in this area should be carried out before vision screening programs can be recommended for implementation among older people.     

Test characteristics of orthoptic screening examination in 3 year old kindergarten children

AIM: To analyse the test characteristics of orthoptic screening for amblyopia or amblyogenic risk factors (target conditions) in kindergarten. METHODS: 1180 three year old children were screened by orthoptists in 121 German kindergartens. Orthoptic screening consisted of cover tests, examination of eye motility and head posture, and monocular visual acuity testing with the Lea single optotype test. Children were re-examined in kindergarten by different orthoptists after 3-6 months using a more demanding pass threshold for visual acuity. All children with at least one positive orthoptic test result or an inconclusive re-examination were referred to an ophthalmologist for diagnosis. The gold standard was set positive if a target condition was diagnosed on ophthalmological examination. It was set negative if no target condition was found upon ophthalmological examination, or if a child who screened negative or inconclusive passed the orthoptic re-examination without any positive test result. RESULTS: The gold standard was ascertained in 1114 children. 26 (2.3%) children had a "positive" gold standard. In 10.8% of the children the initial screening was "inconclusive," mostly due to lack of collaboration. Screening test sensitivity (based on conclusive results only) was 90.9% and specificity was 93.8%. CONCLUSIONS: Orthoptic vision screening of 3 year olds in kindergarten is sensitive and specific. However, owing to a substantial proportion of inconclusive screening results, rescreening of non-cooperative 3 year old children should be considered.     

Examination compliance and screening for diabetic retinopathy: a 2-year follow-up study

Early detection and timely treatment of diabetic retinopathy can preserve vision, yet many people with diabetes do not have their eyes examined regularly. The purpose of this study was to examine eye care practices of people with diabetes who had not previously accessed eye care services on a regular basis. Screening with non-mydriatic retinal photography for diabetic retinopathy was initiated in 1996, and targeted people with diabetes who did not access eye care services on a regular basis. Each test area was revisited 2 years after the initial screening. Patients that did not attend the biennial screening were followed up by mail survey. Although none of the participants in this study had been previously accessing eye care services on a regular basis, 87% did so after attending the screening. These results indicate that mobile screening with non-mydriatic photography, as an adjunct to current eye care services, has the potential to increase examination compliance for diabetic retinopathy and to achieve sustained behaviour change.