Development of visual acuity

The automated preprocessing pipe-line for the estimation of scale-wise entropy from EEG data (APPLESEED): Development and validation for use in pediatric populations

It is increasingly understood that moment-to-moment brain signal variability - traditionally modeled out of analyses as mere "noise" - serves a valuable functional role related to development, cognitive processing, and psychopathology. Multiscale entropy (MSE) - a measure of signal irregularity across temporal scales - is an increasingly popular analytic technique in human neuroscience calculated from time series such as electroencephalography (EEG) signals. MSE provides insight into the time-structure and (non)linearity of fluctuations in neural activity and network dynamics, capturing the brain's moment-to-moment complexity as it operates on multiple time scales. MSE is emerging as a powerful predictor of developmental processes and outcomes. However, differences in data preprocessing and MSE computation make it challenging to compare results across studies. Here, we (1) provide an introduction to MSE for developmental researchers, (2) demonstrate the effect of preprocessing procedures on scale-wise entropy estimates, and (3) establish a standardized EEG preprocessing and entropy estimation pipeline that adapts a critical modification to the original MSE algorithm, and generates reliable scale-wise entropy estimates capable of differentiating developmental stages and cognitive states. This novel pipeline - the Automated Preprocessing Pipe-Line for the Estimation of Scale-wise Entropy from EEG Data (APPLESEED) is fully automated, customizable, and freely available for download from https://github.com/mhpuglia/APPLESEED.

Development of the spatial contrast sensitivity function (CSF) during childhood: Analysis of previous findings and new psychophysical data

Although the contrast sensitivity function (CSF) changes markedly during infancy, there is no consensus regarding whether, how, and why it continues to develop in later childhood. Here, we analyzed previously published data (N = 1928 CSFs), and present new psychophysical findings from 98 children (4.7–14.8 years) and 50 adults (18.1–29.7 years), in order to answer the following questions: (1) Does the CSF change during childhood? (2) How large is the developmental effect size? (3) Are any changes uniform across the CSF, or frequency-specific? and (4) Can some or all of the changes be explained by “non-visual” (i.e. procedural/cognitive) factors, such as boredom or inattentiveness? The new data were collected using a four-alternative forced-choice (4AFC) Gabor-detection task, with two different psychophysical procedures (Weighted Staircase; QUEST+), and suprathreshold (false-negative) catch trials to quantify lapse rates. It is shown that from ages 4 to 18 years, the CSF improves (at an exponentially decaying rate) by approximately 0.3 log₁₀ units (a doubling of contrast sensitivity [CS]), with 90% of this change complete by 12 years of age. The size of the effect was small relative to individual variability, with age alone explaining less than one sixth of variability (16%), and most children performing as well as some adults (i.e. falling within the 90% population limits for adults). Development was frequency-specific, with changes occurring primarily around or below the CSF peak (≤ 4 cpd). At least half — and potentially all — of the changes observed could be explained by non-visual factors (e.g. lapses in concentration), although possible biological mechanisms are discussed.

The effect of refractive error on optokinetic nystagmus

Subjective refraction is the gold-standard for prescribing refractive correction, but its accuracy is limited by patient’s subjective judgment about their clarity of vision. We asked if an involuntary eye movement, optokinetic nystagmus (OKN), could serve as an objective measure of visual-clarity, specifically measuring the dependence of OKN—elicited by drifting spatial-frequency filtered noise—on mean spherical equivalent (MSE) refractive error. In Experiment 1 we quantified OKN score—a measure of consistency with stimulus-direction—for participants with different MSEs. Estimates of MSE based on OKN scores correlate well with estimates of MSE made using autorefraction (r = 0.878, p < 0.001, Bland–Altman analysis: mean difference of 0.00D (95% limits of agreement: − 0.85 to + 0.85D). In Experiment 2, we quantified the relationship between OKN gain (ratio of tracking eye-movement velocity to stimulus velocity) and MSEs (− 2.00, − 1.00, − 0.50, 0.00 and + 1.00D) induced with contact lenses for each participant. The mean difference between measures of MSE based on autorefraction or on OKN gain was + 0.05D (− 0.90 to + 1.01D), and the correlation of these measures across participants was r = 0.976, p < 0.001. Results indicate that MSE attenuates OKN gain so that OKN can be used as an objective proxy for patient response to select the best corrective lens.

Epigenetic tuning of brain signal entropy in emergent human social behavior

BACKGROUND

How the brain develops accurate models of the external world and generates appropriate behavioral responses is a vital question of widespread multidisciplinary interest. It is increasingly understood that brain signal variability-posited to enhance perception, facilitate flexible cognitive representations, and improve behavioral outcomes-plays an important role in neural and cognitive development. The ability to perceive, interpret, and respond to complex and dynamic social information is particularly critical for the development of adaptive learning and behavior. Social perception relies on oxytocin-regulated neural networks that emerge early in development.

METHODS

We tested the hypothesis that individual differences in the endogenous oxytocinergic system early in life may influence social behavioral outcomes by regulating variability in brain signaling during social perception. In study 1, 55 infants provided a saliva sample at 5 months of age for analysis of individual differences in the oxytocinergic system and underwent electroencephalography (EEG) while listening to human vocalizations at 8 months of age for the assessment of brain signal variability. Infant behavior was assessed via parental report. In study 2, 60 infants provided a saliva sample and underwent EEG while viewing faces and objects and listening to human speech and water sounds at 4 months of age. Infant behavior was assessed via parental report and eye tracking.

RESULTS

We show in two independent infant samples that increased brain signal entropy during social perception is in part explained by an epigenetic modification to the oxytocin receptor gene (OXTR) and accounts for significant individual differences in social behavior in the first year of life. These results are measure-, context-, and modality-specific: entropy, not standard deviation, links OXTR methylation and infant behavior; entropy evoked during social perception specifically explains social behavior only; and only entropy evoked during social auditory perception predicts infant vocalization behavior.

CONCLUSIONS

Demonstrating these associations in infancy is critical for elucidating the neurobiological mechanisms accounting for individual differences in cognition and behavior relevant to neurodevelopmental disorders. Our results suggest that an epigenetic modification to the oxytocin receptor gene and brain signal entropy are useful indicators of social development and may hold potential diagnostic, therapeutic, and prognostic value.

Curveball: A tool for rapid measurement of contrast sensitivity based on smooth eye movements

The contrast sensitivity function (CSF) is an informative measure of visual function, but current tools for assessing it are limited by the attentional, motor, and communicative abilities of the participant. Impairments in these abilities can prevent participants from engaging with tasks or following an experimenter's instructions. Here, we describe an efficient new tool for measuring contrast sensitivity, Curveball, and empirically validate it with a sample of healthy adults. The Curveball algorithm continuously infers stimulus visibility through smooth eye tracking instead of perceptual report, and rapidly lowers stimulus contrast in real time until a threshold is found. The procedure requires minimal instruction to administer and takes only five minutes to estimate a full CSF, which is comparable to the best existing methods available for healthy adults. Task repeatability was high: the coefficients of repeatability were 0.275 (in log10 units of RMS contrast) within the same session and 0.227 across different days. We also present evidence that the task is robust across illumination changes, well correlated with results from conventional psychophysical methods, and highly sensitive to improvements in visual acuity from refractive correction. Our findings indicate that Curveball is a promising means of accurately assessing contrast sensitivity in previously neglected populations.

Maturation of Binocular, Monocular Grating Acuity and of the Visual Interocular Difference in the First 2 Years of Life

The sweep visual evoked potential method (sVEP) is a powerful tool for measurement of visual acuity in infants. Despite the applicability and reliability of the technique in measuring visual functions the understanding of sVEP acuity maturation and how interocular difference of acuity develops in early infancy, as well as the availability of normality ranges, are rare in the literature. We measured binocular and monocular sVEPS acuities in 481 healthy infants aged from birth to 24 months without ophthalmological diseases. Binocular sVEP acuity was significantly higher than monocular visual acuities for almost all ages. Maturation of monocular sVEP acuity showed 2 longer critical periods while binocular acuity showed three maturation periods in the same age range. We found a systematic variation of the mean interocular acuity difference (IAD) range according to age from 1.45 cpd at birth to 0.31 cpd at 24 months. An additional contribution was the determination of sVEP acuity norms for the entire age range. We conclude that binocular and monocular sVEP acuities have distinct growth curves reflecting different maturation profiles for each function. Differences in IAD range shorten according to age and they should be considered in using the sVEP acuity measurements for clinical diagnosis as amblyopia.

Analysis of computerized optokinetic nystagmus induction and effect of contrast on ocular fatigue

Optokinetic nystagmus (OKN) is useful in evaluating visual function objectively, and the classical black-and-white-striped OKN drum is being replaced by video or computer monitor. However, the examinee may feel fatigue during test because of high contrast of luminous pattern from monitor. This paper suggests a plan to reduce eye fatigue of participant by decreasing contrast of patterns without reducing OKN response. Alternating black and white stripes are shown on flat-panel liquid-crystal display monitor and moved horizontally to evoke OKN of the examinee, and the OKN wasW observed through electrooculography (EOG). Eye fatigue was estimated from the number of eye blinking, along with dry eye questionnaire according to the contrast of the black and white stripes. White stripes are shown as 300cd/m², and gradual decrement in contrast by 75%, 50%, and 25% were given to investigate the effect of the contrast on the eye fatigue and the OKN. Blinking of the eye was recorded as a video clip and was analyzed by image processing to count the number of blinks while measuring OKN. Experimental results show that incidence of nystagmus does not substantially change with the change of contrast in stimulus pattern but the eye fatigue decreased by the reduction of the contrast. In conclusion, the examinee may choose the contrast option for the OKN test to reduce the stress onto their eye, without affecting the test result.

Management of periorbital microcystic lymphatic malformation with blepharoptosis: Surgical treatment combined with intralesional bleomycin injection

OBJECTIVES

Periorbital microcystic lymphatic malformations (LM) can cause severe symptoms, such as blepharoptosis, amblyopia, chemosis, strabismus, diminished vision, and blindness. The purpose of this study was to evaluate the clinical outcome in periorbital microcystic LM patients with blepharoptosis who underwent surgical treatment combined with intralesional bleomycin injection.

PATIENTS AND METHODS

A retrospective study including nine patients diagnosed as periorbital microcystic LM with blepharoptosis was conducted. All of the patients underwent surgical treatment and bleomycin injection from January 2010 to January 2014. The lesion was resected through the lower eyebrow and/or a coronal incision at the first stage, and levator resection was performed at the second stage. Any persistent lesion or its recurrence was managed by intralesional bleomycin injection.

RESULTS

Blepharoptosis and visual obstruction were corrected in all patients. Mean follow-up was 24.6 months. Six patients had recurrence during the follow-up, and two patients who had partial eyelid closure after the second stage surgery recovered in three months. Amblyopia, astigmatism, and strabismus were not improved after treatment. All of the patients had excellent aesthetic improvement and corrected blepharoptosis.

CONCLUSIONS

Resection through a lower eyebrow and coronal incision and levator resection performed in two stages can quickly correct the visual impairment caused by periorbital microcystic lymphatic malformation with blepharoptosis. Intralesional bleomycin injection is a promising adjunctive therapy for residual or recurrent lesions after surgery.

Face preference in infancy and its relation to motor activity

Infants’ preference for faces was investigated in a cross-sectional sample of 75 children, aged 3 to 11 months, and 23 adults. A visual preference paradigm was used where pairs of faces and toys were presented side-by-side while eye gaze was recorded. In addition, motor activity was assessed via parent report and the relation between motor activity and face preference was examined. Face preference scores followed an inverted U-shaped developmental trajectory with no face preference in 3-month-olds, a strong face preference in 5- and 9-month-olds, and a weaker face preference in 11-month-olds. Adults showed no reliable face preference. Motor activity was a significant predictor of face preference in 3-month-old infants, supporting the presence of motor-social connections in early infancy.

Preverbal assessment for amblyopia

PURPOSE

To describe and compare the different methods of preverbal assessment of amblyopia.

RESULTS

Each method of visual assessment has its plusses and minuses.

CONCLUSION

There is no "best" method for assessment for amblyopia. The best method may be a combination of the various described tests.

Assessment of visual acuity in infancy and early childhood

The forced-choice preferential looking method (FPL) shows the development of acuity during the first year of life, and is applicable to clinical assessment. A tracking test using a narrow strip of grating yields a more sensitive measure for the later part of this age range, however. The development of acuity is dominated by neural rather than optical or accommodative factors. By age 3 years resolution acuity is very close to adult performance, but at 5 years 'crowding' effects may still impair performance on practical acuity tasks more than for the adult.

Relationship between optokinetic nystagmus response and recognition visual acuity

PURPOSE

The aim of this study was to investigate the relation between recognition visual acuity (RVA) and optokinetic nystagmus (OKN) response exhibited to different bar sizes with varying contrast.

METHODS

OKN testing was performed in 52 children aged between 3 and 11 years. The children were evaluated in two groups according to their RVA. Group I consisted of 22 eyes with RVA equal to or better than 0.1 logMAR units. Group II consisted of 30 eyes with RVA 0.2-1 logMAR units. Each subject was seated 60 cm from the screen of Ophthimus device, and was exposed to consecutive black and white stripes of seven different spatial frequencies (0.08-1.6 cycle/degree). The narrowest bar that elicited OKN was identified, and then the OKN contrast threshold at this bar size was established.

RESULTS

Twenty-one of the 22 eyes in Group I, and 26 of the 30 eyes in Group II exhibited 1.6 cycle/degree spatial frequency (P=0.287). In Group II, 88.9% of the 18 eyes with RVA 0.2-0.5 logMAR responded at this maximum spatial frequency, whereas the corresponding figure for the 12 eyes with RVA 0.6-1 logMAR was 83.3% (P=0.531). Contrast sensitivity (CS) significantly changed with age in Group I (P=0.006). When the eyes that responded at maximum spatial frequency in the two groups were compared, the mean CS in Group II was significantly lower than that in Group I (P=0.005).

CONCLUSIONS

The results indicate no relation between spatial frequency threshold for OKN response and RVA in children. However, the children with RVA deficits had significantly lower CS.

Ocular manifestations in congenital toxoplasmosis

BACKGROUND

Retinochoroiditis is the most common ocular manifestation of congenital toxoplasmosis, but other associated ophthalmological pathologies can also occur. The aim of this study was to determine the nature of the latter in treated cases of the disease and to assess their impact on visual function.

METHODS

Four hundred and thirty consecutive children with serologically confirmed congenital toxoplasmosis were included in this study. Data were prospectively collected using standardized ophthalmological assessment forms. The presence of retinochoroiditis and of associated pathologies was ascertained, and their impact on visual function was assessed.

RESULTS

After a median follow-up of 12 years [range 0.6-26 years], 130 children manifested retinochoroiditis. We detected 22 foci of retinochoroiditis at birth and 264 additional ones during the follow-up period. Of these, 48 (17%) were active when first diagnosed. Twenty-five of the 130 children (19%) had other associated ocular pathologies. Of these, 21 (16%) had a strabismus, which was due to macular lesions in 86% of the cases; 7 (5.4%) presented with unilateral microphthalmia, and 4 (3%) with cataracts. Most of these events were detected after the onset of retinochoroiditis. None of the children presented with ocular involvement in the absence of chorioretinal lesions. Macular lesions occurred more frequently in children with associated pathologies (p<0.0001), and associated pathologies were likewise more common in individuals with macular lesions (p=0.0003). Visual impairment occurred in 31/130 cases, and in all but 3 of these eyes it was due not to an associated pathology but to macular retinochoroiditis.

CONCLUSIONS

At the end of the follow-up period, ocular involvement existed in 30% of the treated children with congenital toxoplasmosis. Associated eye pathologies were manifested less frequently than anticipated. They may occur later in life and are an indirect marker of the severity of congenital toxoplasmosis, but they do not have a direct impact on visual acuity. The overall functional prognosis of congenital toxoplasmosis is better than would be expected on the basis of literature findings, with only 2 of the 130 children suffering bilateral visual impairment.

Long-term ocular prognosis in 327 children with congenital toxoplasmosis

OBJECTIVE

Retinochoroiditis is the most frequent consequence of congenital toxoplasmosis. Early diagnosis and treatment are believed to reduce the risk of visual impairment. We report on the clinical evolution of ocular lesions and final visual function in a prospective cohort of congenitally infected children who were identified during monthly maternal prenatal screening.

METHODS

The study included 327 congenitally infected children who were monitored for up to 14 years at the Croix Rousse Hospital in Lyon, France. Data on date of maternal infection; time and type of therapy; antenatal, neonatal, and postnatal work-ups; and ocular status were analyzed.

RESULTS

All mothers but 52 had been treated. Pyrimethamine and sulfadiazine was given in utero to 38% of children and after birth to 72% of newborns. Fansidar was given for an average duration of 337 days in all but 2 children. After a median follow-up of 6 years, 79 (24%) children had at least 1 retinochoroidal lesion. In 23 (29%) of them, at least 1 new event had been diagnosed up to 10 years after detection of the first lesions: reactivation of an existing lesion (1 case), new lesion in a previously healthy location (19 cases), or both (3 cases). Fifty-five children had lesions in 1 eye; of the 45 children for whom final visual acuity data were available, 31 (69%) had normal vision. Twenty-four children had lesions in both eyes; of the 21 for whom final visual acuity data were available, 11 had normal vision in both eyes. None had bilateral visual impairment.

CONCLUSIONS

Clinicians, parents, and elder children with congenital infection should be informed that late-onset retinal lesions and relapse can occur many years after birth but that the overall ocular prognosis of congenital toxoplasmosis is satisfactory when infection is identified early and treated accordingly.

Albipunctatus retinopathy in inherited interstitial nephritis

We describe here a patient with familial interstitial nephritis and albipunctatus retinopathy. Albipunctatus is often seen in patients with Alport syndrome, which is an X-linked disorder characterised in affected males by renal failure by the age of 25, high-tone sensorineural deafness, anterior lenticonus and albipunctatus. The diagnosis of Alport syndrome depends on the electron microscopic appearance of a trabeculated glomerular basement membrane (GBM); and mutations have been demonstrated in the gene for the alpha 5 chain of type IV collagen. In the familial interstitial nephritis described here, the inheritance was autosomal dominant, renal failure developed in middle age, and there was no associated hearing loss or anterior lenticonus. The finding of albipunctatus retinopathy in this patient suggests that the genetic mutation responsible involves a protein common to both retinal and interstitial basement membranes. In addition, we conclude that the demonstration of albipunctatus in an individual with familial nephritis does not necessarily indicate that the underlying disease is Alport syndrome.

Occlusion therapy for strabismic amblyopia

OBJECTIVE

To assess the outcome of occlusion therapy in strabismic amblyopia.

METHODS

The case notes of 369 children requiring strabismus surgery were reviewed.

RESULTS

Of 369 children requiring surgical correction for strabismus, 109 had strabismic amblyopia. All of these patients were treated with occlusion. Seventy-eight per cent (85 of 109) had improvement of their visual acuity to within one Snellen line of the other eye. Another 11% (12 of 109) of patients genuinely failed to achieve equal acuity in both eyes despite occlusion and 11% (11 of 109) failed to improve due to poor compliance.

CONCLUSIONS

Occlusion for six hours per day, every day, produced an effective and rapid response in most patients. There was no occlusion amblyopia. Admission to hospital for occlusion was effective in some refractory cases.

Visual assessment of infants: vernier targets for the Catford drum

Targets comprising a horizontal black line 5' thick offset by 1' were printed on strips to stick to the drums of the Catford Visual Acuity Apparatus. The 'vernier' targets so produced corresponded to the different sizes of Snellen letters from 6/6 to 2/60 when presented at 50 cm. Twenty-five children between the ages of 3 and 12 years with known amblyopia (mostly strabismic) were tested in a double blind trial to compare the visibility of the vernier targets with subjective Snellen acuity. All vernier results, both for better and amblyopic eye, were within one line of Snellen acuity. One hundred and twenty normal preverbal infants with normal eyes under the age of 2 1/2 years were tested with the vernier strips. Normal infants under the age of 6 months recorded a vision of 6/60-2/60; normal infants aged 6 to 12 months recorded 6/24-6/36, and infants between the ages of 1 and 2 1/2 years recorded 6/12-6/18.

Assessment of the Catford drum in visual acuity testing and its use as a measurement of visual performance in low-vision patients

Objective measurements of visual acuity were determined with the Catford drum in 82 eyes of patients in our Low-Vision Clinic who typically suffered from visual loss due to macular disease. The results were compared with subjective measurements of visual acuity by the Snellen chart. The findings indicated a significant overestimation of Snellen visual acuities by the Catford drum in 90.2% of eyes tested by a factor of 1.05 to 20.0, average 4.73. The correlation coefficient for the study was +0.40. This differs from the original results of Catford and Oliver in 1971. In addition, the Catford drum was used on follow-up visits in the same patients to assess 'visual performance'. The initial results showed an improvement in visual acuities when the Catford drum was used in 12 of 15 patients, while the Snellen acuities remained stable when retested after one month of basic instruction and use of standard low-vision aids. This improvement in 'Catford' acuity was by a factor of 0.3 to 10.0, average 4.08. This is thought to represent the patient's ability to learn the use of eccentric viewing or parafoveal retinal areas for vision. It confirms previous intuitive findings and helps to explain why low-vision patients seem to function at a higher level than expected from their Snellen visual acuities.

Assessment of visual acuity in toddlers

Visual acuity in children 15 to 35 months of age is particularly difficult to measure. Children in this age range become bored with methods used for assessment of infants, but they are often not capable of responding to the tests used with older children and adults. Partially because of these difficulties, there is no widely preferred standard test of visual acuity for the 15 to 35 month age range. Instead, a variety of behavioral techniques have been used, with varying degrees of success. These techniques will be described and evaluated with regard to adequacy of norms, percent testable rates, test times, accuracy and similarity to adult standards of visual acuity assessment. Practical suggestions regarding the use of existing techniques and the development of new visual acuity assessment techniques for 15- to 35-month-olds will be given.

Objective techniques of visual acuity assessment in infancy

Three primary techniques for objective assessment of visual acuity in the preverbal infant are variations of optokinetic nystagmus, forced preferential looking and visual evoked potentials. Although these tests are useful, the clinician must be aware of their shortcomings. Failure to evoke optokinetic nystagmus may reflect the infant's lack of interest in the stimulus, an inherently uninteresting stimulus, or a defect in the motor system generating the nystagmus, other than failure to see the stimulus. Forced choice preferential looking has provided useful information about visual development in preverbal infants. The need for more complex stimuli to yield more precise estimates of acuity than the standard grafting stimuli, especially in cases of amblyopia, is discussed. Visual evoked potentials, like forced preferential looking, may grossly overestimate the acuity of the amblyopic patient. Of the techniques discussed, it holds the most promise.

Assessment of early auditory and visual abilities of extremely premature infants

The early auditory and visual abilities of 47 extremely premature infants (31 born less than or equal to 28 weeks gestation) were assessed with a bell, a light and an optokinetic nystagmus drum. All the infants altered to the bell and blinked to the light from 25 weeks postconceptional age (PCA) and beyond. A few infants at first had only a change in heart rate or respiratory rate in response to the bell, or required a high-intensity light to elicit a blink. The majority appeared to habituate to the bell and light during their first examination at one week of age. None of the infants blinked in response to a threatening gesture. Optokinetic nystagmus could be elicited as early as 30 weeks PCA, could be elicited in the majority by 36 weeks PCA, and universally by term (40 weeks PCA). The responses of 15 fullterm newborn infants were not significantly different from those of the preterm infants at term. Alerting to a bell, blinking to light and habituation to both are simple bedside maneuvers for assessing extremely premature infants less than 30 weeks PCA. Optokinetic nystagmus may be useful in assessing the visual abilities of premature infants closer to term.

Critical analysis of visual function evaluating techniques in newborn babies

The most widely-used techniques for testing visual function in babies are reviewed. Advantages and limitations of optokinetic nystagmus testing, visual evoked responses and preferential looking techniques are considered. The theoretical basis and the clinical applicability of those techniques are outlined. Other simple methods are considered as well, which allow practicing ophthalmologists to assess the presence or absence of vision in babies. The importance of early diagnosis for prevention and treatment of visual deficits in babies is stressed.

'Preferential looking' for monocular and binocular acuity testing of infants

A method is described for obtaining rapid and reliable estimates of acuity in infants, for both monocular and binocular viewing. The method depends on 'preferential looking', where the infant prefers to look at a striped pattern rather than a blank screen of matched mean luminance. A staircase procedure for testing is followed, with observations being recorded by a 'blind' observer (who does not know on which of the 2 screens the striped pattern is displayed). Monocular acuity estimates have been obtained for a group of infants 3 to 4 months old with normal refractions. Many of these infants show similar acuity values in the 2 eyes, with a few showing reliable differences between the eyes. To check reliability of the method a comparison of 2 independent interleaved staircase estimates of the same eye have been made. In general this check shows highly consistent estimates for a given eye of a given infant. Nearly all infants show slightly higher acuity estimates for binocular viewing than for monocular. The possible reasons for this difference are discussed. The clinical use of such a method is reported for a number of cases. The method has been found to be useful in a variety of clinical conditions where other available tests are not possible on young infants.

Ophthalmological examination of the infant. Developmental aspects

In recent years, the ophthalmic examination of infants has been of increasing interest to both clinicians and vision researchers. Clinicians have documented a greater risk of retinopathy, strabismus and amblyopia in premature infants, especially those of low birthweight. In addition to the external and retinal examination of the infant eye, a number of clinical tests can help the ophthalmologist to detect visual dysfunction through the evaluation of pupillary responses and ocular motility. Recently, the development of objective techniques (optokinetic nystagmus, forced choice preferential looking, and visually evoked potentials) have not only aided in the detection of ophthalmic disorders in infants; they have contributed to useful definitions of "normal" vision at various ages and to the understanding of factors that influence the pre- and post-gestational development of visual function.

Does the Catford drum give an accurate assessment of acuity?

Adult emmetropes and myopes were tested with the Catford drum and the results compared with subjective (Landolt C) acuity. For he emmetropes the Catford drum was found to overestimate visual acuity by a factor of approximately 4. For myopes, and emmetropes viewing through plus lenses, the discrepancies were much larger. Since the Catford drum not only overestimates acuity but will do so by a factor which varies for different visual disorders, caution is needed in clinical interpretation of results obtained with it.

The development of mature patterns of head-eye coordination in the human infant

Four experiments examined the initiation of coordinated head and eye movement and the vestibulo-ocular reflex (VOR). Experiment 1 examined the initiation of head and eye movement to stationary, peripheral, visual targets. In adults we would expect to see an eye movement followed by a head movement. The VOR would maintain field-holding while the head rotated. Three-month-olds produced the same pattern of coordinated movement as seen in adults, 2-mth-olds produced only eye movements, i.e., no apparent head movement. Experiment 2 examined the gain of the VOR in darkness in 2- and 3-mth-olds and an adult. The VOR at all ages was qualitatively and quantitatively the same. Experiment 3 examined the gain of the VOR during visual fixation. The gain in 3-mth-olds shoed a significant increase as compared to gain in darkness. The same increment was seen in the adult. Two-month-olds showed no facilitation of gain. Experiment 4 examined tonic suppression of the VOR during visual fixation. While total suppression was seen in adult and the 3-mth-olds, no suppression was apparent in 2-mth-olds. Overall, the data indicate the communication between the visual, vestibular, head movement, and eye movement systems shows a marked shift between the second and third month of life.

Preschool visual acuity screening tests

The purpose of the study was to evaluate the relative merits of two screening tests used for visual acuity assessment of preschool children. The tests that were compared were the Good-Lite Company versions of the E-Test and of the STYCAR (Screening Test for Young Children and Retardates). The former is the most popular method for evaluating central acuity in young children in this nation; the STYCAR is a relatively new letter-matching-test developed in England, where it is widely employed. The E-Test poses left-right orientation problems which are eliminated by the symmetrical letters H, T, O and V utilized in the Letter-Matching-Test. Both visual acuity tests were administered on two separate occasions by personnel from the Prevention of Blindness Society of Metropolitan Washington to 633 preschool children in Washington, D.C. By random selection, 150 of the children received the E-Test at both sessions, 162 children received the Letter-Matching-Test at both sessions, 160 chilt athe the second session, and 161 children received the Letter-Matching-Test at the first session and the E-Test at the second session. The author medically examined the eyes of 408 of the 633 children without knowledge of which test had been initially administered. Statistical analysis of the data obtained from the study indicated that the Letter-Matching-Test was significantly better in terms of testability rates, group and individual instruction time, and performance time. The E-Test was more reliable in terms of test-retest acuity scores and was also more valid in terms of agreement between pass-fail results obtained at the first screening session and two levels of pass-fail refraction criteria.

Early surgery and visual correction of an infant born with unilateral eye lens opacity

A healthy neonate born with unilateral cataract was operated upon on Life Day 4. Visual correction and testing were initiated promptly. Resolution showed continuous improvement in the normal eye, with no improvement noted in the operated eye until adequate visual correction was provided. Following correction there was prompt marked improvement of visual resolution.