Sixty strabismus cases operated with the Computerized Strabismus Model 1.0: When does it benefit, when not?

While, in routine strabismus surgery, empirical guidelines and experience are the best in judging which eye muscles to operate, a complex case may need a unique surgical approach, the consequences of which cannot always be envisioned in detail. We sought to improve the results of surgery in these cases by preoperative simulation of each case with the Computerized Strabismus Model 1.0 (CSM). The basis of this model was laid by David A. Robinson. It has been improved by us over the past years to the point that it can be used clinically. Improvements concerned, for example, the mechanics of the eye muscles and the anatomy of insertions and origins. The ease of operation has been improved and the algorithms have been made so much faster that a full calculation for 9 positions of gaze now takes 10 seconds on a hand-held Hewlett Packard 200LX Palmtop. From 1994 onwards, all cases to be operated in our department which were more complex than straightforward horizontal rectus muscle surgery were simulated in the model preoperatively. The predictions of the model compared well with the actual result of surgery in most cases. The model was particularly good in handling complex and unique disorders of motility. However, the model could not reliably predict the effect of strabismus surgery in cases with mechanical restrictions of motilit

Eye colour and skin pigmentation as significant factors for refractive outcome and residual accommodation in hypermetropic children: a randomized clinical trial using cyclopentolate 1% and tropicamide 1%

Purpose To compare the refractive outcome and residual accommodation with respect to various degrees of iris and skin pigmentation in hypermetropic children using 2 drops of cyclopentolate 1% (C + C) or 1 drop of cyclopentolate 1% and 1 drop of tropicamide 1% (C + T). Methods Two hundred fifty-one hypermetropic children were classified according to iris and skin pigmentation (light, medium, dark) and received randomized and double-blind C + C or C + T. Refractive error (spherical equivalent, SEQ) was determined using the Retinomax-K + 3. In 204 subjects, residual accommodation (RA) was determined using the PlusoptiX PowerRefractor. Results A linear mixed model with a light-irided and light skin-pigmented reference group receiving C + T (mean SEQ +3.10 +/- 1.87D) indicated significant less hypermetropia in subjects with a dark iris having a medium- and dark-pigmented skin in C + T, -1.02 +/- 0.29 (-1.59/-0.45) and -1.53 +/- 0.30 (-2.10/-0.95); and in subjects having a light-, medium- and dark-pigmented skin in C + C, -0.74 +/- 0.34 (-1.41/-0.06), -1.26 +/- 0.30 (-1.85/-0.66) and -1.84 +/- 0.30 (-2.42/-1.26). Similar findings were present for RA. Our model with a light-irided and light skin-pigmented reference group receiving C + T (mean RA +0.84 +/- 0.61D) indicated significantly higher RA in dark-irided subjects with medium- and dark-pigmented skin in C + T, +1.05 +/- 0.19 (+0.67/+1.43) and +1.35 +/- 0.20 (+0.9/+1.74), and in C + C, +1.13 +/- 0.21 (+0.71/+1.55) and +1.90 +/- 0.19 (+1.51/+2.28). Conclusions We found solid evidence that skin pigmentation rather than iris pigmentation is the decisive factor for effectiveness of cycloplegics. Awareness of the limitations of cycloplegic regimens in dark-irided/pigmented children is needed. Our study showed that cyclopentolate 1% combined with tropicamide 1% provides more accurate refractive outcomes both statistically and clinically integrating the factor skin pigmentation for dark-irided subjects.Ophthalmic researc

Costs and effects of conventional vision screening and photoscreening in the Dutch preventive child health care system

Background: Little is known about costs and effects of vision screening strategies to detect amblyopia. Aim of this study was to compare costs and effects of conventional (optotype) vision screening, photoscreening or a combination in children aged 3-6 years. Methods: Population-based, cross-sectional study in preventive child health care in The Hague. Children aged 3 years (3y), 3 years and 9 months (3y9m) or 5-6 years (5/6y) received the conventional chart vision screening and a test with a photoscreener (Plusoptix 512C). Costs were based on test duration and additional costs for devices and diagnostic work-up. Results: Two thousand, one hundred and forty-four children were included. The estimated costs per child screened were (sic)17.44, (sic)20.37 and (sic)6.90 for conventional vision screening at 3y, 3y9m and 5/6y, respectively. For photoscreening, these estimates were (sic)6.61, (sic)7.52 and (sic)9.40 and for photoscreening followed by vision screening if the result was unclear (combination) (sic)9.32 (3y) and (sic)9.33 (3y9m). The number of children detected with amblyopia by age were 9, 14 and 5 (conventional screening), 6, 13 and 3 (photoscreening) and 10 (3y) and 15 (3y9m) (combination), respectively. The estimated costs per child diagnosed with amblyopia were (sic)1500, (sic)1050 and (sic)860 for conventional vision screening, (sic)860, (sic)420 and (sic)1940 for photoscreensic)ing and (sic)730 (3y) and (sic)450 (3y9m) for the combination. Conclusions: Combining photoscreening with vision screening seems promising to detect amblyopia in children aged 3y/3y9m, whereas conventional screening seems preferable at 5/6y. As the number of study children with amblyopia is small, further research on the effects of these screening alternatives in detecting children with amblyopia is recommended.Research into fetal development and medicin

Neutral Density Filters as a Tool for Cycloplegic Plusoptix-Photorefractor Measurements: An Explorative Study

Purpose:The purpose of this study is to investigate the usefulness of neutral-density (ND) filters in cycloplegic-Plusoptix-photorefractor measurements.Methods:No-filter and ND-filter 0.04, 0.1 and 0.2 cycloplegic-Plusoptix-photorefractor measurements were made in 42 hypermetropic eyes. Sphere, cylinder, spherical equivalent (SEQ), J0, and J45 values were compared.Results:Mean Plusoptix-photorefractor pupil sizes were 7.7 +/- 0.68 and 7.7 +/- 0.72 mm The no-filter failure rate was 16%, with 87% in pupils >7.8 mm. Mean no-filter sphere, cylinder, SEQ, J0 and J45 values were +0.34 +/- 0.35D, -0.29 +/- 0.22D, +0.20 +/- 0.36, -0.00 +/- 0.15, and +0.02 +/- 0.11, respectively. Only ND-filter-0.04 provided 5% more successful measurements and a clinically significant alteration in the percentage of values exceeding 0.5D for sphere and SEQ (-10% and -20%), but not for cylinder (+5%). Despite the increased accuracy, 21% of the spherical outcome exceeded 0.50D. Furthermore, the single-measure-intraclass-correlation-coefficient between no-filter and ND-filter-0.04 outcome was moderate (sphere 0.78 (0.62-0.87), cylinder 0.59 (0.35-0.75), SEQ 0.68 (0.48-0.82), J0 0.73 (0.54-0.84) and J45 0.57 (0.50-0.86)) and indicated significant individual variation. Bland-Altman-analyses indicated significant bias for sphere and SEQ; p=0.038 and p=0.030.Conclusion:ND-filter-0.04 resulted in a larger proportion of successful measurements and an increased accuracy. However, an unacceptable percentage of inaccuracy was still present compared to retinoscopy. There could be validity issues with the ND-filter 0.04 or the baseline no-filter readings at the start. We conclude that cycloplegic Plusoptix-photorefraction, even with the use of a 0.04 ND filter, is not a suitable method for exact objective refraction purposes in children.Ophthalmic researc

Adverse reactions following routine anticholinergic eye drops in a paediatric population: an observational cohort study

Ophthalmic researc

A randomized clinical trial using atropine, cyclopentolate, and tropicamide to compare refractive outcome in hypermetropic children with a dark iris; skin pigmentation and crying as significant factors for hypermetropic outcome

Ophthalmic researc

EEG changes as an indication of central nervous system involvement following cyclopentolate 1% eye drops: a randomized placebo-controlled pilot study in a pediatric population

To compare EEG-patterns after instillation of cyclopentolate versus placebo eye drops. Prospective, randomized, placebo-controlled, and observational pilot study is presented. Ophthalmology outpatient clinic Dutch metropolitan hospital. Healthy 6- to 15-year-old volunteers with normal or low BMI requiring a cycloplegic refraction/retinoscopy. Randomized; 1 visit 2 drops cyclopentolate-1% and 1 visit 2 drops placebo (saline-0.9%). Single-blind: conducting researcher. Double blind: subjects, parents, clinical-neurophysiology staff, neurologist, and statistician. A 10-min baseline EEG-recording, drop-application, and follow-up to at least 45 min. Primary outcome: Detection of CNS changes, i.e. EEG-pattern changes, following two drops of cyclopentolate-1%. Secondary outcome: Determination of the extent of these pattern changes. Thirty-six cyclopentolate-1% saline-0.9% EEG registrations were made in 33 subjects; 18 males and 15 females. Three subjects were tested twice (interval 7 months). Nine out of fourteen (64%) of the 11- to 15-year-old children reported impaired memory, attention, alertness, as well as mind wandering following cyclopentolate. Drowsiness and sleep were seen in EEG-recordings of 11 subjects (33%) following cyclopentolate. We observed no drowsiness nor sleep during placebo recordings. The mean time to drowsiness was 23 min. Nine subjects arrived in stage-3 sleep but none arrived in REM-sleep. In subjects without sleep (N=24), significant changes compared to placebo-EEG were present for many leads and parameters. The main findings during awake eye-open recording were as follows: 1) a significant increase of temporal Beta-1,2 and 3-power, and 2) a significant decrease in: a) the parietal and occipital Alpha-2-power, b) the frontal Delta-1-power, c) the frontal total power, and d) the occipital and parietal activation synchrony index. The former finding reflects cyclopentolate uptake in the CNS, and the latter findings provide evidence for CNS suppression. Cyclopentolate-1% eye drops can affect the CNS and may cause altered consciousness, drowsiness, and sleep with concomitant EEG results in both young children and children in puberty. There is evidence that cyclopentolate has the potency to act as a short acting CNS depressant. Nevertheless, however, cyclopentolate-1% can safely be used in children and young adolescents.Ophthalmic researc

Quantitative visual field analysis of squinting eye under binocular conditions in ten patients with microstrabismus

Introduction: It is still not exactly known how strabismic patients perceive the surrounding world. It is commonly believed that patients with early onset convergent strabismus and microstrabismus do not suffer from diplopia because of two mechanisms: suppression and anomalous retinal correspondence (ARC). Suppression only occurs under binocular viewing conditions and concerns the central part of the visual field of the strabismic eye. Suppression is associated with a decrease of binocular functions in the central part of the visual field. ARC can be described as a form of internal squint that corrects for the image disparity due to external squint. It is the defence mechanism against diplopia in the more peripheral visual field. There is evidence however that this shift in retinal localisation does not affect the visual field equally. It seems that ARC is more outspoken in the periphery than in the centre of the visual field. This might be expl

Quantitative perimetry under binocular viewing conditions in microstrabismus

In order to elucidate the type, size and depth of suppression scotomata in microstrabismus and small angle convergent strabismus, we performed binocular static perimetry in 14 subjects with strabismus and four normal observers. The strabismic cases had an objective angle of convergent squint between 1 and 8 deg, visual acuity between 0.1 and 1.25, and limited stereopsis. During testing the subjects fused pictures on two Friedmann visual field analyzers. Right and left eyes were studied separately under both monocular and binocular viewing conditions. In five strabismics a suppression scotoma was found in the squinting eye, with a diameter of 5-30 deg and a depth ranging from 4 to 14 dB. No suppression scotomata could be detected in the nine other subjects nor in the four normal observers. In conclusion, only 36% of subjects with strabismus were found to have a suppression scotoma. These scotomata were centered around the fixation point of the squinting eye, in some cases also encompassing the foveal area, and varying in depth and size