The Rotterdam AMblyopia Screening Effectiveness Study (RAMSES): compliance and predictive value in the first 2 years

BACKGROUND

RAMSES is a 7 year follow up study, aiming at the evaluation of the effectiveness and the efficiency of screening for amblyopia. In this first report, concerning the first 2 years of life, the compliance with the prevention programme and the positive predictive value (PPV) of the screening tests used, are presented.

METHODS

All results of the standardised screening test for strabismus, applied by child healthcare physicians, within a birth cohort of 4072 Rotterdam children at the age of 9, 14, and 24 months, were registered. Children with a positive test result were referred to their general practitioner, who was asked to arrange a definitive referral to an ophthalmological centre. The results of the examinations at these centres were registered in standardised forms and served as reference for establishing the PPV.

RESULTS

The screening was (at least one time) attended by 3958 children (97%). 160 of these children (4%) were referred, of whom 101 (64%) visited an ophthalmological centre, so that a conclusive diagnostic evaluation was possible. For amblyopia, the predictive value of a positive test result followed by an effective referral was 0.42.

CONCLUSION

Referral procedures after a positive test result in the Dutch child healthcare screening programme for amblyopia need to be improved. The Dutch screening test used to detect amblyopia exhibits a relatively favourable PPV.

Contrast sensitivity function in children: normalized notation for the assessment and diagnosis of diseases

The purpose of this article is to describe a normalized notation for the assessment of the contrast sensitivity in children. This notation is obtained dividing the log contrast sensitivity value found in a patient by the corresponding normative contrast sensitivity data. The ratio obtained describes the contrast sensitivity of a patient facilitating its understanding, assessment and consequently effective communications. This article shows the normalized notation developed for children aged from 3 to 7 years old. An evaluation of the contrast sensitivity in healthy and amblyopic patients has been shown in order to explain the procedure to follow. The use of normalized notation in clinical procedures will provide to the clinician a better understanding of the results and the changes over time as well by comparison in the assessment of an ocular disease.

Non-cycloplegic screening for amblyopia via refractive findings with the Nikon Retinomax hand held autorefractor in 3 year old kindergarten children

AIMS

To assess non-cycloplegic screening for amblyopia with the hand held Nikon Retinomax autorefractor in 3 year old kindergarten children.

METHODS

427 three year old children were examined in kindergarten with the Retinomax without cycloplegia. A gold standard was established in all children by two orthoptic examinations in kindergarten. If there were missing, abnormal, or inconsistent findings, children were referred for ophthalmological examination. If, by the ophthalmological examination, a new case of amblyopia requiring treatment was diagnosed, the gold standard was set "positive."

RESULTS

In 404 children the gold standard was obtained. 10 children (2.5%) had a "positive" gold standard of unknown and untreated amblyopia. Screening sensitivity was 0.80, specificity 0.58, accuracy 0.58, and the likelihood ratio 1.89.

CONCLUSION

Non-cycloplegic refractive screening with the Retinomax led to many false positive referrals due to instrument myopia and "inconclusive" results. Hence specificity, accuracy, and the likelihood ratio were too low to conduct screening effectively.

Amblyopia: detection, prevention, and rehabilitation

This year's literature on the detection, prevention, and rehabilitation of amblyopia is again somewhat dominated by the topic of vision screening, specifically photoscreening and also by the therapeutic challenges of compliance and late treatment. Basic scientists also have added to our knowledge and understanding of certain interesting and clinically significant characteristics of the visual perception of amblyopes.

Screening merits of the Lang II, Frisby, Randot, Titmus, and TNO stereo tests

PURPOSE

Previous works show a pronounced disagreement on the reliability of stereo tests as screening tools for amblyopia and strabismus. This study's aim was to compare the ability of the Lang II, Frisby, Randot, Titmus, and TNO stereo tests to detect amblyopia and strabismus with visual acuity testing and cover testing.

METHODS

A total of 1035 school children aged 12 to 13 years were examined in a field study in Monterrey, Mexico. In addition to the 5 stereo tests, the examination included visual acuity, cover testing, refraction (skiascopy), and inspection of the red reflex and posterior pole.

RESULTS

Sensitivity ranged from 17% to 47% (Frisby-Titmus-Lang II-Randot-TNO, in order of occurrence). Of the 60 subjects with strabismus and/or amblyopia, only 8 subjects were identified by all 5 stereo tests. A considerable number of subjects (25), the majority of whom were amblyopic (23 subjects), were not identified by any of the tests. All stereo tests showed higher sensitivities for strabismus than for amblyopia.

CONCLUSION

None of the 5 stereo tests studied is suitable for screening for amblyopia or strabismus. The results of both ocularly normal subjects and subjects with strabismus and/or amblyopia are variable, and there is no way of separating normal response from abnormal response.

Vision screening in central Iowa

This study assessed the vision-screening practices of all preschools and elementary schools during the spring of 2000 in the Heartland Area Education Agency (AEA) in central Iowa. Surveys were returned by 7% of the preschools and 56% of the elementary schools. Survey questions were drafted based on recommendations from the Iowa Vision Screening Program Guidelines, which were distributed to all Iowa school districts in 1997. Areas surveyed included vision-screening personnel, attainment of students' visual history, rescreening practices, referral and follow-up, and screening procedures. Survey results indicated that there is a need for improvement to standardize vision-screening procedures within Heartland AEA. Time and effort are invested in activities that are not recommended, and not enough effort is being put into recommended activities such as obtaining vision histories, rescreening to avoid overreferrals, and follow-up to make sure students receive required treatment.

Detection of red reflex asymmetry by pediatric residents using the Brückner reflex versus the MTI photoscreener

OBJECTIVE

To compare the ability of pediatric residents to differentiate an asymmetric from a symmetric red reflex in patients with anisometropia and microstrabismus using the Brückner reflex and the Medical Technology Innovations (MTI) photoscreener.

METHODS

A prospective, masked, case-control study was performed. Twelve pediatric residents evaluated 10 study patients and 6 control subjects in a masked manner in 2 separate sessions, using the Brückner reflex or the MTI photoscreener, evaluating for asymmetric (abnormal) or symmetric (normal) red reflexes between the 2 eyes. Each study patient had asymmetric red reflexes and the amblyogenic risk factor of anisometropia or microstrabismus. Each control subject had symmetric red reflexes.

RESULTS

The pediatric residents had a mean correct score of 82% (69%-100%) using the MTI photoscreener versus a mean correct score of 65% (44%-81%) using the Brückner reflex (McNemar test: alpha < 0.01). The sensitivity of the MTI photoscreener evaluation was 89% in comparison to 61% for the Brückner reflex. The specificities for the MTI photoscreener versus the Brückner reflex were similar at 69% and 71%, respectively.

CONCLUSIONS

Pediatric residents were better at detecting asymmetric red reflexes in patients with anisometropia and microstrabismus when evaluating MTI photoscreener photographs than when evaluating the red reflexes by the Brückner reflex. The MTI photoscreener may be a more sensitive method than the Brückner reflex to screen for the common amblyogenic risk factors of anisometropia and microstrabismus by easier detection of red reflex asymmetry.

Amblyopia. Current clinical studies

Over the next two years, results from several multi-center amblyopia treatment studies will become available. These data may have a profound influence on our approach to treating this condition. This is indeed an exciting time to be taking care of children with amblyopia, as we anticipate the results of these studies.

Comparison between anisometropic and strabismic amblyopia using functional magnetic resonance imaging

AIMS

To assess calcarine activation with functional magnetic resonance imaging (fMRI) in patients with anisometropic and strabismic amblyopia.

METHODS

14 amblyopes (eight anisometropic and six strabismic) were studied with fMRI using stimuli of checkerboards of various checker sizes and temporal frequencies. While T2* weighted MRI were obtained every 3 seconds for 6 minutes, patients viewed the stimuli monocularly with either the amblyopic or sound eye.

RESULTS

Amblyopic eyes showed reduced calcarine activation compared with contralateral sound eyes in fMRI in all subjects. The calcarine activation from amblyopic eyes in anisometropic amblyopes was more suppressed at higher spatial frequencies, while that from amblyopic eyes in strabismic amblyopes was more suppressed at lower spatial frequencies.

CONCLUSION

These results suggest that fMRI is a useful tool for the study of amblyopia in humans. The calcarine activation via amblyopic eyes because of anisometropia or strabismus has different temporospatial characteristics, which suggests differences in the neurophysiological mechanisms between two types of amblyopia.

Commonly missed diagnoses in the childhood eye examination

Early and accurate detection of eye disorders in children can present a challenge for family physicians. Visual acuity screening, preferably performed before four years of age, is essential for diagnosing amblyopia. Cover testing may disclose small-angle or intermittent strabismus. Leukocoria, which is detected with an ophthalmoscope, may indicate retinoblastoma or cataract. Children with glaucoma may have light sensitivity and enlargement of the cornea, and conjunctivitis that does not respond quickly to treatment may reflect more serious ocular inflammation. Children with serious eye injuries often present to the primary care physician. Nystagmus and many systemic conditions are associated with specific eye findings.

Poor correlation between "fix-follow-maintain" monocular/binocular fixation pattern evaluation and presence of functional amblyopia

PURPOSE

To assess the reliability of visual screening with fix- follow-maintain (FFM) method in early detection of amblyopia in children who are not able to cooperate in testing with Allen Figures or Snellen E-chart.

METHODS

Followup records of 89 patients that were examined in our pediatric ophthalmology department between May 1996 and May 1999 were evaluated retrospectively. The visual acuities that were measured with FFM method at the first visit were compared with the visual acuity levels that were measured with the Snellen E-chart at later followup visits. Functional amblyopia was defined as a difference of 2 or more Snellen lines between the two eyes.

RESULTS

Amblyopia was later definitively diagnosed on the E-chart in only 17 (32.6%) of the 52 eyes that were estimated to have a significantly lower visual acuity than the fellow eye with the FFM method. Sensitivity of the FFM method in diagnosing amblyopia was found to be 53.1% and the specificity was 38.5%.

CONCLUSIONS

The use of the FFM monocular/binocular fixation pattern to determine visual acuity and the possible presence of amblyopia is so insensitive, and so unspecific, that its reliability is very low and the results of such testing are therefore virtually useless, if not medically hazardous. There is, therefore, a need to make more universally available more sophisticated tests of vision (preferential looking, VEP); where they are not available, further emphasis should be placed on Snellen equivalent vision testing as with Allen Cards, Tumbling E, HOTV Test, Lea Figures etc. so as to obtain an accurate direct visual acuity at as young an age as possible. Amblyopia treatment should not be initiated solely on the basis of FFM testing.

Visual screening of Swedish children: an ophthalmological evaluation

PURPOSE

This study describes the various ophthalmological conditions detected in the Swedish visual screening program for children.

METHODS

The study was longitudinal and retrospective. All children (3126) born in 1982 in three Swedish municipalities have been followed from birth to ten years of age. Visual acuity was examined at the ages of 4, 5.5, 7 and 10 years. Before the age of 4, a gross examination of the eyes was performed.

RESULTS

The prevalence of ametropia in the population was 7.7%, the prevalence of strabismus 3.1%, and the prevalence of organic lesions 0.6%. Seven children (0.2%) were visually handicapped (visual acuity </=0.3 in the better eye). Refractive errors and microtropias were mainly detected at the age of 4, when the first visual acuity test was performed, while manifest strabismus was in many cases detected before this age. With this screening and subsequent diagnosis and treatment, the prevalence of deep amblyopia (visual acuity </=0.3) has been reduced from 2% to 0.2%. With treatment, 47% of the amblyopic children achieved a visual acuity better than 0.7.

CONCLUSION

Visual screening is effective in detecting visual and ocular disorders. Most conditions are discovered before the age of 6. Compared to an unscreened population, the prevalence of amblyopia is greatly reduced.

BVAT distance vs. near stereopsis screening of strabismus, strabismic amblyopia and refractive amblyopia; a prospective study of 68 patients

PURPOSE

Although there have been studies in the past of the difference between distance and near stereopsis in intermittent exotropia, no such comparisons have been studied and/or reported for other forms of strabismus, nor for strabismic functional amblyopia, or for refractive functional amblyopia.

METHODS

The study was prospective: Sixty-eight consecutive patients, ages 6-76 years, with either childhood onset strabismus and no amblyopia, childhood onset strabismus and amblyopia, or refractive amblyopia and no strabismus, had their stereopsis measured. Distance stereopsis was determined on the Mentor BVAT with Random Dot E Test (global stereopsis) and the Circle Test (contour stereopsis). Near stereopsis was determined with the Circle Test of the Randot Stereotest. The data were tabulated and analyzed statistically.

RESULTS

Of the 26 strabismus/no amblyopia cases, 14 (54%) appreciated distance stereopsis. Of these, 12/14 were intermittent, and other 2 who were constant had deviations of 8 PD or less. Only 4 of the 14 appreciated global stereopsis at distance (mean = 90 sec. of arc), but all 14 appreciated contour stereopsis at distance (mean = 125 sec. of arc). Of all 26, 21 (81%) had near stereopsis (mean = 137 sec. of arc). For the 21 strabismic amblyopes, only one appreciated global stereopsis at distance (120 sec of arc), and 2 (10%) contour stereopsis at distance (mean = 210 sec. of arc). These two and 4 others (total 29%) had near stereopsis (mean = 162 sec. of arc). For the 21 refractive amblyopes, 3 appreciated global stereopsis at distance (mean = 220 sec. of arc), 11 in all, (52%) contour stereopsis at distance (mean = 121 sec. of arc) and 20 (95%) had near stereopsis (mean = 78 sec. of arc). The percentages of patients in all categories capable of appreciating distance stereopsis were "statistically significantly" (P<.05) or clinically/medically significantly different from (less than) the percentages having near stereopsis.

CONCLUSIONS

distance stereopsis is more likely to be reduced or absent than near stereopsis in strabismus, strabismic amblyopia and refractive amblyopia and thus appears to be more sensitive to, and better screening for, binocular vision disorders and a stronger and better outcome standard for treatment of binocular vision disorders than near stereopsis.

Visual and visuospatial development in young children with Williams syndrome

This study investigated the relation between sensory visual problems and the severity of visuospatial difficulties in a large group of young children with Williams' syndrome (WS). A questionnaire describing visual and associated problems was completed by the families of 108 children with WS and detailed follow-up assessments were conducted, including visual, spatial, motor, visuocognitive, and linguistic tests of 73 of these children (mean age 7 years 3 months; 40 males, 73 females). Children with WS showed a much higher incidence of common paediatric sensory vision problems (strabismus, visual acuity loss, amblyopia, reduced stereopsis) than normally developing children. It was found that delays with respect to age normative values increased with age on all tests. No significant correlation was found between the presence of a visual deficit and the severity of the visuospatial problems, suggesting that the difficulties children with WS have in understanding spatial arrangements are not simply a result of their earlier sensory visual problems. Results confirm the dissociation between visuospatial and language abilities in children with WS, and support the neurobiological model of a split between ventral and dorsal stream processing of visual information with a generalized deficit in dorsal stream processing in young children with WS.

Comparison of preschool vision screening methods in a population with a high prevalence of astigmatism

PURPOSE

To compare the effectiveness of four methods of screening 3- to 5-year-old children for astigmatism high enough to require spectacle correction.

METHODS

Lea Symbols Visual Acuity Screening (LSVAS), MTI Photoscreening (MTIPS), Nidek KM-500 Keratometry Screening (KERS), and Retinomax K-Plus Noncycloplegic Autorefraction Screening (NCARS) were attempted on 379 preschool children who are members of a Native American tribe having a high prevalence of astigmatism that is primarily corneal in origin. The need for spectacle correction was determined by cycloplegic refraction. Receiver Operating Characteristic (ROC) curves were fit, confidence intervals were determined, and area under the curves was compared.

RESULTS

Astigmatism > or = 1.00 D was present in the right eye of 47.5% and in the left eye of 48.0% of children. Spectacles were prescribed for children < 48 months of age who had cylinder > or = 2.00 D and children > or = 48 months who had cylinder > or = 1.50 D, with the result that 33% of subjects required spectacles. Area under the ROC curve was 0.98 for NCARS, 0.92 for KERS, 0.78 for MTIPS, and 0.70 for LSVAS, and each of these values differed significantly from the other three (all P < 0.007). Testability was significantly higher for NCARS (99.5%) and KERS (99.7%) than for MTIPS (93.5%) and LSVAS (92.0%).

CONCLUSIONS

In a population that included many children with astigmatism, objective, fully automated screening methods (NCARS and KERS) were superior to both visual acuity screening and photoscreening with subjective interpretation in identifying children who had astigmatism requiring spectacle correction.

[Unilateral amblyopia without strabismus and with anisometropia]

PURPOSE OF THE STUDY

To evaluate a group of patients with unilateral isometropic amblyopia according to presence of possible amblyogenic factors.

MATERIAL AND METHODS

37 patients (18 girls and 19 boys) with unilateral amblyopia without strabismus and with anisometropia of less than 1 D in any of the meridians were analysed according to such possible risk factors of amblyopia as age of examination, age of mother on delivery, sex, family history, puerperal complications, birth weight, refraction error, left or right eye. Depth of amblyopia, state of binocular vision and results of optical and pleoptical treatment were also evaluated.

RESULTS AND DISCUSSION

No significant risks were found regarding the age of patient, sex, left or right eye, birth weight, age of mother on delivery, puerperal complications and family history. Refraction error was not high. Depth of amblyopia did not correlate with amount of refraction error. Central fixation was present only in 50% and stereopsis only in 42% of patients. 10 patients revealed no significant defect of fixation or binocular vision. All patients responded significantly poorly to treatment.

CONCLUSIONS

Presence of amblyopia in patients with isometropia cannot be explained by genetic or puerperal risk factors. It might have developed in the period sensitive for amblyopia as a result of anisometropia that was later diminished by the process of emmetropisation or microstrabismus which was spontaneously cured. Some cases can be described as idiopathic because no defect can be detected. Early in life screening is necessary to successfully diagnose and treat amblyopia in childhood.

Detection of improper fixation in MTI photoscreening images

PURPOSE

To determine the effect of fixation shift on photoscreening crescents, the ability of human interpreters to detect fixation shift, and the potential improvement by image processing.

METHODS

MTI photoscreening (Medical Technologies & Innovations, Inc, Lancaster, PA) images, measured at 11 positions of gaze, were obtained from 10 subjects (9 with refractive error warranting spectacle correction). Photographs were taken with subjects fixating at 20, 15, 10, and 5 cm to the left and the right of the camera fixation target (1 m distant); 5 cm above and below the camera fixation target; and on-axis. Photographs were inspected by 11 experienced raters, who indicated if the subject appeared to be looking directly at the camera. The photographs were digitized, enlarged, contrast enhanced, and measured by 3 raters. For each photograph, distance from the corneal light reflex to the nasal limbus was measured and a measure of asymmetry computed.

RESULTS

Raters could reliably detect off-axis fixation greater than 10 cm away from the intended fixation target. Raters correctly identified on-axis subject viewing 73% of the time. Crescents became larger when the fixation shifted off-axis for both the myopic and hyperopic subjects. Image analysis correctly classified 10 of 10 on-axis measurements and 34 of 39 off-axis measurements.

CONCLUSION

Direct inspection of photoscreening images by trained raters can result in the failure to detect small but relevant errors of fixation. These fixation shifts can cause crescents to become larger than expected, resulting in false-positive classification. Image analysis offers a potential improvement in the detection of off-axis fixation in MTI photoscreening images.