Evaluation of the Amblyopia tracker app.

PURPOSE: The Amblyopia tracker app has been developed to be a tool for parents to monitor changes in vision at home during amblyopia treatment. The aims of this study were to evaluate the feasibility and repeatability of parents testing their children at home and to compare home test results to an assessment in clinic by an orthoptist. METHODS: Children (age < 18 years) with amblyopia (interocular acuity difference of ≥ 0.2logMAR) were recruited. Parents were asked to test their child with the app three times during a two week period followed by an online questionnaire about the usability. Participants also tested within 48 h of their appointment where the measurement was repeated by an orthoptist. RESULTS: Out of 277 potential participants contacted, 37 completed three home measurements, mean age 6.8 years (SD 2.94). Home tests comparisons were made between test two and three to ensure familiarity with the process. Paired t-tests showed no statistically significant difference for either eye or the interocular acuity difference (IAD). However, 29% had a difference in IAD of more than 0.1logMAR on repeated testing, with a maximum of 0.4logMAR difference in the IAD. Questionnaire responses from the parents who participated were predominantly positive with 97% of respondents saying they would use it if were available. Comparison of home and clinical measurements (n = 23, mean age 6.72 SD 2.60) showed no statistically significant differences for either eye or interocular acuity difference (paired t-test, p > 0.3 in all cases). CONCLUSION: Results show no statistically significant differences for the Amblyopia tracker app when used by parents at home on repeated testing, or between the home test by a parent and the test by a clinician. However, variability in the results does indicate that further improvements are required to ensure the results can be used as a reliable clinical tool.

Normative data for the redesigned Kay Pictures visual acuity test.

The Kay Picture Test of visual acuity is used extensively in the diagnosis and management of children. The test has been redesigned and validated to meet the international visual acuity chart guidelines, necessitating the collection of new normative data. The data presented here demonstrates that the visual acuities of children <60 months of age with no visual deficiency improve with age and show no significant intraocular difference. This is the first report of normative data in young children for the redesigned Kay Pictures Test (singles format).

The effect of induced fusional demand on static and dynamic stereoacuity thresholds: the digital Synoptophore.

BACKGROUND/AIMS: The ability to extract depth from disparity may be hindered under fusional stress, as alignment of the eyes may be more difficult to maintain consistently. Therefore we aim to determine the effect of fusional demand on stereoacuity in individuals with no known binocular vision impairments. METHODS: A novel static and dynamic binocular depth detection task, capable of assessing many discrete levels of stereoacuity, was presented on digital displays attached to each tube of the Synoptophore. Stereoacuity was measured with any latent deviation fully corrected and compared to that measured at the 'recovery' angle. This recovery angle is where single vision is restored after decompensation to diplopia, during vergence range assessment. RESULTS: Seventy-two subjects (50 Female, 22 Male; mean (SD) age 22 (6) years) were assessed. The amount of fusional demand was between 1 and 26 prism dioptres (PD), with a mean (SD) of 8(6)PD. Under zero fusion demand the mean (SD) static and dynamic depth detection thresholds were 322(53)" and 69(23)". Under fusional stress these were 224(40)" and 77(21)". There was no significant difference between thresholds in stressed and zero demand fusion (p = 0.08). Dynamic depth detection thresholds were significantly lower than static (P < 0.01). CONCLUSION: Fusional stress does not appear to impact on stereoacuity. The numerical value of the recovery point varied amongst individuals, but this represents a common point, where single vision is easily restored and binocularity well established. Due to individual differences in the ability to control a certain amount of fusional stress (e.g. vergences stress of 10PD, when recovery is 8PD, will perturb binocularity more than a person with a recovery of 20PD), previous reports may not accurately represent the effect of fusional stress. Whilst our findings are contrary to previous reports, we did not stress fusion beyond the recovery point and used a more accurate/repeatable method to measure stereoacuity.

Stereopsis: are we assessing it in enough depth?

The assessment of stereoacuity is an integral part of the ophthalmic assessment, with the responses used to inform clinical management decisions. Stereoacuity impacts on many aspects of life, but there are discrepancies reported where people without measurable stereoacuity report appreciating 3-D vision. This could be due, in part, to the presentation of the stimuli. A literature review was undertaken to evaluate current assessment techniques, how they relate to patient outcomes, identify the limitations of current tests and discuss how they could be improved. Recent evidence has been collated on currently available tests, used commonly within vision clinics, with normative data provided allowing responses to the tests to be interpreted. The relevance of the results is evaluated in relation to a range of outcomes, where a reduced level of stereopsis has a negative impact on the ability of an individual to perform many tasks, and can lead to an increase in difficulty interacting in the world. Current tests are limited in the aspects of stereoacuity they assess and their ability to precisely measure stereopsis. The world is not static, yet clinical tests are limited to measuring static stereoacuity, even though higher grades of depth perception can be identified in the presence of changing depth. Presentation methods of stereoacuity tests have remained similar over time, with a limited number of disparity levels assessed. New assessment methods are becoming available that include automated staircase testing to present multiple levels of disparity using digital technology. Current clinical tests are limited in their presentation, and are poor at detecting/measuring stereoacuity in those with limited stereopsis. Given the relevance of the stereoacuity measurement to management choices and functional outcomes, new testing methods would be beneficial to fully assess stereoacuity, both static and dynamic.

Incidence, risk factors and management of intractable diplopia.

AIMS: There is a paucity of literature concerning intractable diplopia. The aims of this study were to determine the incidence of intractable diplopia in the UK, identify the causes and any associated risk factors, establish how cases are managed and if the treatment is successful and tolerated. METHODS: A 1-year prospective observational study was undertaken via the British Ophthalmological Surveillance Unit (BOSU). This involved implementation of a reporting mechanism, which then triggered distribution of an incident questionnaire to explore clinical details concerning each case and a follow-up questionnaire 6 months later to explore how the case had been managed. RESULTS: The incidence of intractable diplopia was 53 cases per year. The most common preceding events were strabismus surgery (32%), no known preceding event, that is,spontaneous (25%), severe head trauma (8%), cataract surgery (6%) and vitrectomy (6%). In the at-risk age group of 7 years and above, the incidence of intractable diplopia following strabismus surgery is 1 in 494 (95% CI; 1 in 296 to 790) cases. A total of nine different treatments were used in the management, with many patients receiving between two and four different methods. The overall success rate was poor, but most effective were opaque intraocular lenses (IOLs) (86%) and opaque contact lenses (50%). CONCLUSION: Intractable diplopia is a relatively rare but important condition. The main risk factor is a pre-existing strabismus, and careful counselling is needed when planning surgical correction in patients with no demonstrable binocular function. Treatment success of intractable diplopia is high when using opaque IOLs, although with additional risk, but is often disappointing via other methods where it can be difficult to eradicate the diplopia successfully.

Normative Values for Near and Distance Clinical Tests of Stereoacuity.

PURPOSE: Extensive literature exists on normative stereoacuity values for younger children, but there is less information about normative stereoacuity in older children/adults. Individual stereotests cannot be used interchangeably-knowing the upper limit of normality for each test is important. This report details normative stereoacuity values for 5 near/distance stereotests drawn from a large sample of participants aged 16-40 years, across 3 studies. METHODS: Participants (n=206, mean age 22.18±5.31 years) were administered the following stereotests: TNO, Preschool Randot, Frisby, Distance Randot, and Frisby-Davis 2. Medians and upper limits were calculated for each test. RESULTS: Upper limits for each stereotest were as follows: TNO (n=127, upper limit=120" arc), Preschool Randot (PSR, n=206, upper limit=70" arc), Frisby (n=206, upper limit=40" arc), Distance Randot (n=127, upper limit=160" arc), and Frisby-Davis 2 (n=109, upper limit=25" arc). CONCLUSIONS: Normative values for each stereotest are identified and discussed with respect to other studies. Potential sources of variation between tests, within testing distances, are also discussed.

A Systematic Comparison of Static and Dynamic Cues for Depth Perception.

PURPOSE: A clinical diagnosis of stereoblindness does not necessarily preclude compelling depth perception. Qualitative observations suggest that this may be due to the dynamic nature of the stimuli. The purpose of this study was to systematically investigate the effectiveness of static and dynamic stereoscopic stimuli. METHODS: Stereoscopic stimuli were presented on a passive polarized stereoscopic monitor and were manipulated as follows: static disparity (baseline condition), dynamic disparity (change in z-location), change in stimulus pattern, change in z-location with pattern change, change in x-location (horizontal shift), a control (nil-disparity signal). All depth-detection thresholds were measured simultaneously using an adaptive four-alternative-forced-choice (4AFC) paradigm with all six conditions randomly interleaved. RESULTS: A total of 127 participants (85 women, 42 men; mean [SD] age, 21 [5] years) with visual acuity better than 0.22 logMAR in both eyes were assessed. In comparison to the static disparity condition, depth-detection thresholds were up to 50% lower for the dynamic disparity conditions, with and without pattern change (P < 0.001). The presence of a changing pattern in isolation (P = 0.71) or a horizontal shift (P = 0.41) did not affect the thresholds. CONCLUSIONS: Dynamic disparity information facilitates the extraction of depth in comparison to static disparity signals. This finding may account for the compelling perception of depth reported in individuals with no measurable static stereoacuity. Our findings challenge the traditional definition of stereoblindness and suggest that current diagnostic tests using static stimuli may be suboptimal. We argue that both static and dynamic stimuli should be employed to fully assess the binocular potential of patients when considering management options.

Assessment of the Density of Suppression to Identify Risk of Intractable Diplopia in the United Kingdom.

BACKGROUND/AIMS: Occlusion used to treat amblyopia towards the end of the developmental component of the critical period gives a risk of inducing intractable diplopia. In the United Kingdom, the density of suppression is assessed via the Sbisa/Bagolini filter bar, but there is very little research evidence to guide clinical practice or interpretation of the tests used. The aims of this study were to determine current practice and estimate the incidence of intractable diplopia following amblyopia treatment. METHODS: Current practice and incidence of intractable diplopia following amblyopia were determined via a questionnaire distributed to head orthoptists in every eye department in the United Kingdom. The questionnaire explored testing and test conditions, interpretation of the test results, and cases of intractable diplopia over the last 5 years. RESULTS: There was considerable variation in clinical practice of the measurement of the density of suppression and interpretation of the results to guide the treatment of amblyopia. The minimum age of patients taking the test ranged from 2 to 8 years and the minimum filter considered still safe to continue treatment ranged from 4 to 17. It is estimated there were 24 cases of intractable diplopia over the last 5 years. CONCLUSION: The issue of intractable diplopia and amblyopia treatment is likely to become increasingly important as there appears to be greater plasticity and scope to treat amblyopia in teenagers and adults than was previously thought. Lack of knowledge of how to evaluate the risk may lead to more cases of intractable diplopia or alternatively treatment being withheld unnecessarily.

Clinical Assessment of Stereoacuity and 3-D Stereoscopic Entertainment.

BACKGROUND/AIMS: The perception of compelling depth is often reported in individuals where no clinically measurable stereoacuity is apparent. We aim to investigate the potential cause of this finding by varying the amount of stereopsis available to the subject, and assessing their perception of depth viewing 3-D video clips and a Nintendo 3DS. METHODS: Monocular blur was used to vary interocular VA difference, consequently creating 4 levels of measurable binocular deficit from normal stereoacuity to suppression. Stereoacuity was assessed at each level using the TNO, Preschool Randot®, Frisby, the FD2, and Distance Randot®. Subjects also completed an object depth identification task using the Nintendo 3DS, a static 3DTV stereoacuity test, and a 3-D perception rating task of 6 video clips. RESULTS: As intraocular VA differences increased, stereoacuity of the 57 subjects (aged 16-62 years) decreased (eg, 110", 280", 340", and suppression). The ability to correctly identify depth on the Nintendo 3DS remained at 100% until suppression of one eye occurred. The perception of a compelling 3-D effect when viewing the video clips was rated high until suppression of one eye occurred, where the 3-D effect was still reported as fairly evident. CONCLUSION: If an individual has any level of measurable stereoacuity, the perception of 3-D when viewing stereoscopic entertainment is present. The presence of motion in stereoscopic video appears to provide cues to depth, where static cues are not sufficient. This suggests there is a need for a dynamic test of stereoacuity to be developed, to allow fully informed patient management decisions to be made.

Use of atropine penalization to treat amblyopia in UK orthoptic practice.

PURPOSE: To compare clinical practice patterns regarding atropine penalization use by UK orthoptists to the current evidence base and identify any existing barriers against use of AP as first-line treatment. METHODS: An online survey was designed to assess current practice patterns of UK orthoptists using atropine penalization. They were asked to identify issues limiting their use of atropine penalization and give opinions on its effectiveness compared to occlusion. Descriptive statistics and content analysis were applied to the results. RESULTS: Responses were obtained from 151 orthoptists throughout the United Kingdom. The main perceived barriers to use of atropine penalization were inability to prescribe atropine and supply difficulties. However, respondents also did not consider atropine penalization as effective as occlusion in treating amblyopia, contrary to recent research findings. Patient selection criteria and treatment administration largely follow current evidence. More orthoptists use atropine penalization as first-line treatment than previously reported. CONCLUSIONS: Practitioners tend to closely follow the current evidence base when using atropine penalization, but reluctance in offering it as first-line treatment or providing a choice for parents between occlusion and atropine still remains. This may result from concerns regarding atropine's general efficacy, side effects, and risk of reverse amblyopia. Alternatively, as demonstrated in other areas of medicine, it may reflect the inherent delay of research findings translating to clinical practice changes.

The effect of degrading binocular single vision on fine visuomotor skill task performance.

PURPOSE: To evaluate the impact of degrading binocular single vision (BSV) on performance of fine visuomotor skill tasks requiring speed/accuracy. METHODS: Binocular functions (Frisby/Preschool Randot [PSR] stereoacuity, horizontal phasic prism fusion amplitudes) were measured in visually normal participants aged 18 to 40 years (n = 80). Participants performed 2-timed visuomotor tasks: water pouring (450 mL accurately into five measuring cylinders at 90 mL) and bead threading on upright needles (30 large, 22 small beads, creating two difficulty levels). Task and binocular function measures were repeated in a randomized order with monocular visual acuity (VA) reduced in three-line increments using convex spherical lenses. Analyses used were Kruskal-Wallis/Mann-Whitney U tests and linear mixed modeling. RESULTS: Median Frisby stereoacuity levels were 20″ arc at baseline, 55″ arc when VA was degraded by 6 lines, 210″ arc by 9 lines, and unmeasurable by 12 lines (9 lines in some individuals). Task performance times deteriorated for the large bead task (7%-10% between lenses, total 37% from median baseline time of 51 seconds, P < 0.001), and small bead task (0.5%-15% between lenses, total 42% from median baseline time of 57 seconds, P < 0.001). Binocular function measures causing significant fixed effects were base-out fusional amplitudes in both bead tasks (large: P = 0.010, small: P = 0.011) and PSR stereoacuity in the small bead task (P = 0.047). Water-pouring task performance was not significantly affected by changes in any experimental parameter. CONCLUSIONS: Degrading motor fusion as well as stereoacuity significantly affects performance in certain fine visuomotor tasks. This impact is differentially affected by task difficulty.

Visual acuity assessment of children with special needs.

INTRODUCTION AND PURPOSE: A number of studies have evaluated visual acuity (VA) of special needs children, but no analyses of the parents' perception of VA testing or the utilization of VA test results by pediatric ophthalmologists have been reported. PATIENTS AND METHODS: Special needs children referred for an initial VA test (Teller Acuity Cards) during a 2-year period were enrolled (n = 309). Within the overall cohort, twenty consecutive parents whose child attended during a 6-week period completed a Parent Questionnaire before and after VA testing. Also, 58 parents of infants with cortical visual impairment (CVI) completed the Parental Stress Index-Short Form (PSI-SF) before VA testing and 3 months later. Referring pediatric ophthalmologists (n = 12) completed a Physician Questionnaire. RESULTS: VA testing was associated with parents reporting increased knowledge scores and decreased concerns about their children's vision on the Parent Questionnaire. VA testing was also associated with reduced Total and Parental Distress subscale scores on the PSI-SF by parents of infants with CVI. Ophthalmologists reported that VA results were useful in diagnosis and clinical management and provided new information to parents, Early Childhood Intervention programs, schools, and social agencies. CONCLUSION: VA testing is of benefit in children with special needs to both their parents and ophthalmologists, providing quantitative information about visual impairment and reducing stress experienced by parents.

Conservative management of intermittent distance exotropia: a review.

BACKGROUND AND PURPOSE: Intermittent distance exotropia is difficult to conservatively manage, with techniques varying widely between institutions. This review aims to examine current literature on conservative management for intermittent distance exotropia, investigate its impact upon current clinical practice, and identify areas for further research. METHOD: A literature search was performed using PubMed, Web of Knowledge, LILACS, and the University of Liverpool Orthoptic Journals and Conference Transactions Database. All English-language papers published between 1950 and the present day were considered. RESULTS: Intermittent distance exotropia is a difficult condition to manage because of its variability / uncertain natural history, although control scores can facilitate management decisions. Research is required to establish recommended dosages for antisuppression occlusion and determine whether other treatments such as minus lenses are more effective. Use of orthoptic exercises has declined, but recently certain exercises have been shown to improve surgical outcomes if applied preoperatively. Prisms are mainly used postoperatively. Minus lens therapy is recommended as a first line treatment, but may not always be successful. CONCLUSION: Conservative management techniques for intermittent distance exotropia have their place as both an alternative and an adjunct to surgery. However, further research needs to be conducted to determine which techniques are appropriate for which patients.

Relationship between binocular vision, visual acuity, and fine motor skills.

PURPOSE: The aims of this study were to analyze the relationship between the performance on fine motor skills tasks and peripheral and bifoveal sensory fusion, phasic and tonic motor fusion, the level of visual acuity (VA) in the poorer seeing eye, and the interocular VA difference. METHODS: Subjects aged 12 to 28 years with a range of levels of binocular vision and VA performed three tasks: Purdue pegboard (number of pegs placed in 30 s), bead threading task (with two sizes of bead to increase the difficulty, time taken to thread a fixed number of beads), and a water pouring task (accuracy and time to pour a fixed quantity into five glass cylinders). Ophthalmic measures included peripheral (Worth 4 dot) and bifoveal (4 prism diopter) sensory fusion, phasic (prism bar) and tonic (Risley rotary prism) motor fusion ranges, and monocular VA. RESULTS: One hundred twenty-one subjects with a mean age of 18.8 years were tested; 18.2% had a manifest strabismus. Performance on fine motor skills tasks was significantly better in subjects with sensory and motor fusion compared with those without for most tasks, with significant differences between those with and without all measures of fusion on the pegboard and bead task. Both the acuity in the poorer seeing eye (highest r value of all motor tasks = 0.43) and the interocular acuity difference were statistically significantly related to performance on the motor skill tasks. CONCLUSIONS: Both sensory and motor fusion and good VA in both eyes are of benefit in the performance of fine motor skills tasks, with the presence of some binocular vision being beneficial compared with no fusion on certain sensorimotor tasks. This evidence supports the need to maximize fusion and VA outcomes.

Final version of the Distance Randot Stereotest: normative data, reliability, and validity.

PURPOSE: Measurement of distance stereoacuity may be useful in assessing strabismic patients, especially those with intermittent exotropia. We developed the Distance Randot Stereotest as an easily administered quantitative test for distance stereoacuity in children. By using a prototype, we reported testability, validity, and normative data. Here we report normative and validity data for the final, commercially available version of the test. METHOD: We administered both the Prototype and the Final Version Distance Randot Stereotest to 156 normal volunteers (2-40 years of age) and 77 strabismic patients (4-62 years of age). Test-retest data were collected for the Final Version. RESULTS: Normative Final Version scores were similar to those obtained with the Prototype; 96% were < or = 100 arcsec. Test-retests were identical in 82% and within one disparity level in 100%. Final Version scores were correlated with Prototype scores (rs = 0.64, p < 0.001). Among strabismic patients, 62.3% had abnormal stereoacuity; those with normal scores had incomitant or intermittent deviations. Nil stereoacuity was found in 27 patients, confirmed in 90.9% of retests; 17 had measurable stereoacuity, confirmed in 96.3% of retests. Patients with constant strabismus were more likely to have nil stereoacuity than patients who had intermittent strabismus (95% vs 12.2%). CONCLUSIONS: Distance Randot scores from normal subjects have low variability within each age group and high test-retest reliability. There is little overlap between Distance Randot scores from normal control and strabismic patients. The Distance Randot Stereotest is a sensitive measurement of binocular sensory status that may be useful in monitoring progression of strabismus and/or recovery after strabismus surgery.

The functional significance of stereopsis.

Purpose. Development or restoration of binocular vision is one of the key goals of strabismus management; however, the functional impact of stereoacuity has largely been neglected. Methods. Subjects aged 10 to 30 years with normal, reduced, or nil stereoacuity performed three tasks: Purdue pegboard (measured how many pegs placed in 30 seconds), bead threading (with two sizes of bead, to increase the difficulty; measured time taken to thread a number of beads), and water pouring (measured both accuracy and time). All tests were undertaken both with and without occlusion of one eye. Results. One hundred forty-three subjects were recruited, 32.9% (n = 47) with a manifest deviation. Performances on the pegboard and bead tasks were significantly worse in the nil stereoacuity group when compared with that of the normal stereoacuity group. On the large and small bead tasks, those with reduced stereoacuity were better than those with nil stereoacuity (when the Preschool Randot Stereoacuity Test [Stereo Optical Co, Inc., Chicago, IL] results were used to determine stereoacuity levels). Comparison of the short-term monocular conditions (those with normal stereoacuity but occluded) with nil stereoacuity showed that, on all measures, the performance was best in the nil stereoacuity group and was statistically significant for the large and small beads task, irrespective of which test result was used to define the stereoacuity levels. Conclusions. Performance on motor skills tasks was related to stereoacuity, with subjects with normal stereoacuity performing best on all tests. This quantifiable degradation in performance on some motor skill tasks supports the need to implement management strategies to maximize development of high-grade stereoacuity.

Factors affecting development of motor skills in extremely low birth weight children.

PURPOSE: The aim of this study is to analyze the impact of ophthalmic and neonatal factors on motor development in extremely low birth weight (ELBW) children. METHODS: Sixty-four ELBW children at least 3 years of age were recruited. Visual acuity (VA) was assessed using the Teller acuity cards (TACs) and a letter test, if possible. A validated questionnaire assessing 25 fine (part A) and 20 gross motor (part B) skills was administered to the parents. Data were collected on retinopathy of prematurity (ROP) zone, intraventricular haemorrhage (IVH), length of stay in hospital, and number of days on oxygen. RESULTS: Abnormal TAC acuity was associated with significantly lower scores on both parts A and B (part A: 21.5 versus 11.8, p < 0.001; part B: 17.5 versus 13.2, p < 0.001). Linear regression demonstrates a significant direct relationship between letter acuity and score A only (p = 0.03, r(2) = 0.179). Neither length of hospital stay, number of days ventilated, nor a history of IVH were associated with score A or B. However, the presence of ROP zone 1 was associated with a lower score A (p = 0.03). CONCLUSION: In this ELBW cohort VA and ophthalmic factors were the only factors associated with scores of development, particularly fine motor development.

Spontaneous consecutive exotropia in childhood.

PURPOSE: Consecutive exotropia is commonly the result of a surgical correction of a primary esotropia but may develop spontaneously. This study examines the clinical characteristics of patients who have developed a spontaneous consecutive exotropia and relates the key features to previously reported findings. METHODS: Patients were identified by routine clinical practice from May 2000 to December 2003 by retrospective case note analysis. Patients that presented with an esotropia that became an exotropia (without surgery or botulinum toxin A) were included. RESULTS: This study consisted of 14 patients who presented with an esotropia from early weeks of life to almost 4 years. No patients were undergoing occlusion treatment at the onset of the exotropia and no subject had dense amblyopia. The most common characteristics included (1) age of onset of esotropia of 24 months or less; (2) hypermetropic refractive error of +5 DS mean spherical equivalent; (3) lack of binocular single vision. CONCLUSION: The results highlight the variability of the condition with no single consistent finding, with the lack of binocular single vision, early onset esotropia, and high hypermetropia being common findings. Amblyopia was not found to be an important characteristic.

Visual outcomes and perinatal adversity.

Preterm birth per se, the neonatal environment, retinopathy of prematurity (ROP) and neurological damage are all causes of visual impairment and the impact of these factors is discussed in relation to the resultant ophthalmic deficits. Visual acuity impairments range from blindness, due to ROP or cortical visual impairment, which can be identified at an early age, to subtle deficits related to preterm birth only identified at a later age. Visual function deficits are not limited to visual acuity but can affect contrast sensitivity, field of vision and colour vision. Strabismus and refractive errors are also very common in children following perinatal adversity. Although more is now known about the types of deficits affecting these children, there is still a poor understanding of how these deficits impact on a child's functional ability. The impact of these ophthalmic deficits on the long term ophthalmic care required, and the role of perinatal factors, is discussed.

Predicting long-term visual outcome in children with birth weight under 1001 g.

PURPOSE: To examine the visual acuity development of extremely low birth weight children and to determine factors that are predictive of long-term outcome. METHODS: This is a prospective observational longitudinal cohort study of children with birth weight less than 1001 g. One hundred thirty-nine children were recruited. Retinopathy of prematurity (ROP) examinations were graded according to the International Classification for ROP. Grating acuity was assessed monocularly with Teller acuity cards. All children were assessed before 24 months corrected age; 123 of the cohort had a grating acuity assessment at over 3 years. For the children who were capable, an assessment of recognition acuity was measured with the Electronic Visual Acuity system. RESULTS: Data are presented for the right eye and the ages reported are adjusted for prematurity to allow comparison with normative data. Initial grating acuity was compared with the late grating and recognition acuity, but in both cases analysis showed no statistically significant association. However, the relative risk analysis showed that, if the slope was abnormal, there was a 5.5 times higher risk of abnormal recognition acuity. Eyes with zone 1 disease were associated with a worse visual acuity outcome, but zone 1 disease also occurred more frequently in children with lower birth weight and gestational age. CONCLUSIONS: Early measurements of visual acuity may be misleading in terms of the visual prognosis. The factor that was most predictive of a poor late visual acuity outcome was the rate of development, as calculated by the slope of the early visual acuity measurements.