G. Robert LaRoche

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.

The use of binocular visual acuity in the assessment of intermittent exotropia.

BACKGROUND It has been suggested that a decrease in distance stereoacuity in patients with intermittent exotropia is a good indicator of diminishing control. However, there has been no adequate explanation for this reported reduction in distance stereoacuity in these patients. We postulate that the decrease in stereoacuity is related to blurred visual acuity created by an increasing demand on accommodation, which these patients use in an attempt to control the exodeviation. This can best be assessed by measuring binocular visual acuity (BVA). Analysis of BVA could provide a useful clinical tool to evaluate control measures used by patients with intermittent exotropia. METHODS A prospective study of patients with intermittent exotropia, ranging in age from 6 to 60 years, was performed. Only those patients with the presence of either basic or divergence excess (simulated or true) type exodeviation were included in the study. The data analysis included the age of these patients, age at onset of the deviation, monocular and binocular visual acuity, oculomotor and fusional status, and near and distance stereoacuity. RESULTS Data from 36 patients show that the measurements of BVA correlated well with a corresponding loss of distance stereoacuity but not with the size of the deviation. CONCLUSION The decrease of stereoacuity reported in patients with exotropia can be explained by increased accommodation and decreased distance BVA. This measurement can be a simple method of quantifying the fusional control of patients with intermittent exotropia.

The Range and Variability of Ophthalmological Parameters in Normal Children Aged 4½ to 5½ Years

BACKGROUND Some standards for childhood ophthalmological variables exist. However, for most parameters, the range of variation found in normal children remains poorly defined. METHODS We have determined the range of normal function for a number of commonly measured ophthalmological variables in 162 children, classified normal by Gold Standard ophthalmological examination. This group is representative of almost 12,000 normal children aged 4 1/2 to 5 1/2 in Nova Scotia. RESULTS In 56.8% of eyes the visual acuity was 6/4.5. The use of a chart with crowding bars was more discriminating between differences in higher levels of acuity and highlighted differences in acuity between the two eyes. Randot stereoacuity showed a uniform, non-Gaussian distribution of scores. Cycloplegic refractive errors were distributed about a modal value of between +0.5 and +1.0 diopter. Forty percent of eyes had no detectable astigmatism. Ninety-seven percent of subjects had no heterophoria. Fusional vergence data are presented. CONCLUSION Our results document the complete normal range for selected ophthalmological parameters in normal preschoolers. The values obtained were in general better than expected.

Autosomal recessive cerebellar hypoplasia and tapeto-retinal degeneration: A new syndrome

Two sisters with autosomal recessive cerebellar hypoplasia and severe nonprogressive retinal pigmentary disease are presented. This syndrome has been previously described in only 1 patient. The retinal changes may be difficult to discern and we suggest that all patients with congenital ataxia have a detailed ophthalmologic assessment, including electroretinography.

Has rising pediatric obesity increased the incidence of idiopathic intracranial hypertension in children

OBJECTIVE Idiopathic intracranial hypertension (IIH) in children is an uncommon but significant cause of morbidity, including permanent visual loss. It is important to understand if, like obesity, IIH in children is on the rise and is related to that increase. The aim of this study is to compare the recent incidence rate of pediatric IIH in a tertiary care hospital with earlier data published from that same hospital. DESIGN Retrospective chart review. PARTICIPANTS All children aged 2 to 16 years diagnosed with IIH at the IWK Health Centre in Halifax between 1997 and 2007. METHODS Charts of eligible patients were reviewed to ensure all diagnostic criteria for IIH were met. Incidence and obesity rates were calculated based on data from Statistics Canada. RESULTS Twelve cases (5 males, 7 females) fulfilling the diagnostic criteria for IIH were identified, for an annual incidence of 0.6 cases per 100,000 children with no sex predilection (p = 0.51). Obesity was noted in 75% of patients examined (9/12). Children older than 12 years were more likely to be obese (6/6, 100%) compared with those younger than 12 years (3/6, 50%). CONCLUSIONS The calculated incidence is lower than that found in an earlier study for the same geographic region (0.9 cases per 100,000 children) despite increasing obesity rates. This decrease may be a reflection of improved diagnostic techniques or may indicate that factors other than obesity govern IIH predilection in younger children.

The Method of Treatment Cessation and Recurrence Rate of Amblyopia

Background and purpose: To date, much of the research regarding amblyopia has been focused on which therapeutic modality is the most efficacious in amblyopia management. Unfortunately, there is a lack of research into which method of treatment cessation is the most appropriate once therapy has been completed. The purpose of this study is to investigate if the cessation method affects the recurrence rate of amblyopia. Methods: This study was a prospective randomized clinical trial of 20 subjects who were wearing full-time occlusion and were at the end point of their therapy. The subjects were randomized into one of two groups: abrupt cessation or therapy tapering. All subjects were followed for 3 consecutive 4-week intervals, for a total of 12 weeks, to assess the short-term recurrence rate of amblyopia. Subjects who were in the tapered group had their occlusion reduced from full-time occlusion (all waking hours minus one) to 50% of waking hours at study enrollment (i.e., from 12 hours/day to 6 hours per day); occlusion was reduced by an additional 50% at the first 4-week study visit (i.e., from 6 hours/day to 3 hours), with occlusion being discontinued completely at the week 8 visit. All subjects who were in the abrupt cessation group had their full-time occlusion discontinued completely at the start of the study (i.e., from 12 hours/day to none). Additional assessments were also conducted at week 26 and week 52 post–therapy cessation to determine the longer term amblyopia regression rate. For the purposes of this study, recurrence was defined as a 0.2 (10 letters) or more logarithm of the minimum angle of resolution (logMAR) loss of visual acuity. Results: A recurrence of amblyopia occurred in 4 of 17 (24%; CI 9%–47%) participants completing the study by the week 52 study end point. There were 2 subjects from each treatment group who demonstrated a study protocol–defined recurrence. Conclusion: There was a 24% risk of amblyopia recurrence if therapy was discontinued abruptly or tapered in 8 weeks. In this small sample, the assigned cessation method did not affect the rate of amblyopia recurrence. It is recognized that the smaller sample size in our study prevents us from making definitive conclusions on the potential role that abrupt cessation has on the regression rate of amblyopia. The sample size was too small to reach an acceptable level of statistical power; therefore the generalizability of the findings to the broad population of all patients with amblyopia requires continuing research. This study therefore could be considered as a pilot study.

Congenital corneal anesthesia

PURPOSE/METHODS The case of a 7-month-old infant illustrates the diagnostic findings, including magnetic resonance imaging, and the difficulties of treating congenital corneal anesthesia. RESULTS/CONCLUSIONS The diagnosis of sporadic idiopathic congenital corneal anesthesia was one of exclusion. Normal gasserian ganglia were demonstrated on magnetic resonance imaging. Visual rehabilitation was successful with continuous lubrication, arm splinting at bedtime, and treatment of amblyopia. It continues to be essential for the parents to monitor the corneal status.

Error of calibration in ophthalmic calipers: a source of significant clinical errors

OBJECTIVE Length measuring instruments are frequently used in ophthalmic surgery practice. For all subspecialties, calipers need to be accurate. This study was carried out to identify errors of calibration in ophthalmic calipers as a potential source of significant clinical errors. DESIGN This study is a descriptive research. METHODS All Castroviejo calipers free of any visible damage and available to the ophthalmic surgeons in the operating room suites of our 2 affiliated hospitals were included. The caliper scale readings were compared to measurement markings on a standardized ruler at screening points of 1, 5, 10, and 15 mm on the ruler. Any caliper with a discrepancy of 0.5 mm or more at any set of these screening points went on to having further analysis. RESULTS Seventy-one calipers were examined, of which 30 (42%) showed at least 1 caliper scale reading discrepancy of ≥0.5 mm as compared to ruler measurements. Errors of at least 1 mm were found in 6 of 30 calipers (20%). The majority of calipers underestimated lengths 22/30 (73%), whereas 27% overestimated. CONCLUSIONS With close to half of the calipers inducing a 0.5 mm or more error, and with 20% of these at least 1 mm, significant clinical consequences could ensue: for example, in follow up of glaucomatous corneas in children, in measurements for anterior chamber intraocular lens sizing, in certain refractive surgery techniques, pars-plana sclerotomies, and intravitreal injection sites, or in measuring amounts in strabismus to name a few. Errors in calibration of ophthalmic calipers must be acknowledged and avoided.

The Hidden Challenges of Mixed Amblyopia

Introduction This article will cover the subject of complex mixed amblyopia and its hidden challenges. Clarification of the terminology is followed by a clinical presentation of these difficult cases to illustrate their varied causes and many interactions. An examination of the evidence in the literature on treatment success is followed by a discussion on the challenges facing parents and members of the caring team in the management of complex mixed amblyopia. Method This exposé is both a critical summary of the literature on the subject and the result of 25 years of clinical experience in a busy tertiary care pediatric ophthalmic practice. Results Very little high quality evidence is available on the results of the treatment of complex mixed amblyopia. Descriptive series, illustrative case reports and anecdotal comments are nevertheless a source of information worthy of careful consideration to help both orthopists and ophthalmologists involved. The severity of the loss of organic integrity, a realistic visual target, and close monitoring of the therapeutic efforts are essential components of a successful outcome. Conclusion The treatment of complex mixed amblyopia is the ultimate test for the orthoptist. While the evidence in the literature is empirical at best, the diagnostic and therapeutic challenges it represents can nevertheless be met.

Diagnostic Challenges in Acquired Non-accommodative Esotropia

The sudden onset of an esotropia in childhood can be a challenging diagnostic dilemma for the ophthalmologist, especially when the child is healthy, the refraction is near normal and the family history is negative. Because of the possibility of a neurological cause, many will resort to neuroimaging in the setting of a normal full clinical examination and prior to initiating a treatment such as surgical correction. This chapter will examine the diagnostic challenges of such cases as well as examination findings that can help guide the clinician to the appropriate diagnostic evaluation and therapy.