A process for evaluating adverse environmental impacts by cooling-water system entrainment at a California power plant

A study to determine the effects of entrainment by the Diablo Canyon Power Plant (DCPP) was conducted between 1996 and 1999 as required under Section 316(b) of the Clean Water Act. The goal of this study was to present the U.S. Environmental Protection Agency (EPA) and Central Coast Regional Water Quality Control Board (CCRWQCB) with results that could be used to determine if any adverse environmental impacts (AEIs) were caused by the operation of the plant's cooling-water intake structure (CWIS). To this end we chose, under guidance of the CCRWQCB and their entrainment technical working group, a unique approach combining three different models for estimating power plant effects: fecundity hindcasting (FH), adult equivalent loss (AEL), and the empirical transport model (ETM). Comparisons of the results from these three approaches provided us a relative measure of confidence in our estimates of effects. A total of 14 target larval fish taxa were assessed as part of the DCPP 316(b). Example results are presented here for the kelp, gopher, and black-and-yellow (KGB) rockfish complex and clinid kelpfish. Estimates of larval entrainment losses for KGB rockfish were in close agreement (FH is approximately equals to 550 adult females per year, AEL is approximately equals to 1,000 adults [male and female] per year, and ETM = larval mortality as high as 5% which could be interpreted as ca. 2,600 1 kg adult fish). The similar results from the three models provided confidence in the estimated effects for this group. Due to lack of life history information needed to parameterize the FH and AEL models, effects on clinid kelpfish could only be assessed using the ETM model. Results from this model plus ancillary information about local populations of adult kelpfish suggest that the CWIS might be causing an AEI in the vicinity of DCPP.

Cycloplegic refractions in healthy children aged 1 through 48 months

OBJECTIVES

To provide a description of refractive errors in healthy, term-born children, aged 1 through 48 months, and to test the hypotheses that spherical equivalent becomes significantly less hyperopic and less variable with increasing age.

METHODS

Following a prospective, cross-sectional design, cycloplegic retinoscopy was used to measure the refractive error in both eyes of 514 healthy, term-born children in 12 age groups. Three hundred were aged 12 months or younger. Spherical equivalent and cylindrical power and axis were analyzed as a function of age. Prediction limits for spherical equivalent were calculated.

RESULTS

Spherical equivalents of right and left eyes did not differ at any age. Hyperopia declined significantly with increasing age. The variability in spherical equivalent also decreased significantly with age. Cylindrical error of 1 diopter or more was found in 25% of the children; the proportion with astigmatism was highest in infancy and then waned. Myopia and anisometropia were rare, occurring in 3% and 1% of the sample, respectively.

CONCLUSIONS

Significant declines in hyperopia and variability of spherical equivalent appear to be features of emmetropization. The normal prediction limits provide guidelines against which data from individual patients can be compared.

Reduced visual resolution acuity and cerebral white matter damage in very-low-birthweight infants

Neonatal cerebral white matter echolucencies predict visual resolution acuity deficits in very-low-birthweight (VLBW) infants. We examined maternal sociodemographic, lifestyle, intrapartum, infant birth/perinatal, and ocular motor/refractive characteristics to determine whether they accounted for this association in infants who were tested once between postnatal age 25 and 56 weeks (corrected for gestational age at birth). Cranial ultrasound scans were read by consensus to identify echolucency in a population of VLBW infants with no known ocular abnormalities. Visual resolution acuity was measured with the Acuity Card Procedure (ACP) in 14 infants with echolucency and compared with that of 81 VLBW infants born in the same hospitals with normal ultrasound scans. In time-oriented logistic regression models, echolucency remained a consistent predictor of abnormal visual resolution acuity after adjustment for covariates in three developmental periods (pre-, peri-, and postnatal). Odds ratios ranged from 19.3 (95% confidence interval, 4.5 to 82.2; p=0.001) to 10.4 (95% confidence interval, 1.3 to 81.9; p=0.03). Reduced visual resolution acuity in VLBW infants appears to be due to cerebral white matter damage.

Semi-micro solid-phase extraction of organic compounds from aqueous and biological samples

A technique is described for performing solid-phase extractions on a semi-micro scale. Thin membrane disks 4 mm in diameter containing lightly sulfonated polystyrene or Silicalite particles are placed in the hub of a syringe needle. Aqueous samples (1-6 ml) are passed through the membrane disks and extracted compounds are subsequently eluted with 20-50 microliters of an organic solvent. Unlike solid-phase micro extraction (SPME) which uses a coated fiber, the present method is essentially a total extraction technique. Recoveries > 90% were generally obtained for a wide variety of test compounds. The same test compounds in human urine, albumin and human serum samples can be extracted without any pretreatment other than addition of a suitable surfactant. A "double-pass" technique was developed for convenient field sampling.

Vision in Leber congenital amaurosis

OBJECTIVE

To determine if vision changed with age in infants and children with Leber congenital amaurosis.

PATIENTS

Grating acuity and dark-adapted visual thresholds were tested in 36 patients with Leber congenital amaurosis. Longitudinal assessments were obtained for 24 patients and analyzed for significant changes over time. Visual acuity and threshold and the courses of visual acuity and threshold were examined for significant associations with hyperopia, fundus appearance, and complicated vs uncomplicated status.

RESULTS

Measurable grating acuities ranged from 0.16 to 6 cycles per degree (median, 1.27 cycles per degree or about 20/500), and dark-adapted visual thresholds were elevated 1.0 to 5.6 log units (median, 2.33 log units). Eighteen patients never had demonstrable grating acuity, and 12 had no light perception. Among those with serial tests, visual acuity improved or remained stable in 10 patients and declined in 4. Dark-adapted visual thresholds were stable in those with improving or stable visual acuities but worsened in 5 patients, including the 4 whose visual acuity worsened. No significant associations of visual acuity, dark-adapted visual threshold, the course of visual acuity, or the course of dark-adapted visual threshold with hyperopia, fundus appearance, or complicated vs uncomplicated status were found.

CONCLUSIONS

Visual capabilities varied widely. Vision was stable in the majority by longitudinal measures but increased in a few and deteriorated in others. Neither ocular characteristics nor complicated vs uncomplicated status predicted visual function. Thus, if vision and its course are to be known in a patient with Leber congenital amaurosis, it must be tested.

Monocular acuity norms for the Teller Acuity Cards between ages one month and four years

PURPOSE

To derive norms for monocular grating acuity and interocular acuity differences that are appropriate for clinical applications using the acuity card procedure (ACP) and Teller Acuity Cards (TAC).

METHODS

Monocular acuities were measured in 460 children in 12 age groups between 1 month and 4 years. Inclusion criteria were term birth, good general health and normal development, normal eyes, and cycloplegic refraction within specific limits. Each child was tested by two ACP testers who were aware of TAC spatial frequency but not grating location during testing.

RESULTS

Three monocular tests were completed in the first session in 99% of children. Median time to complete the tests of both eyes ranged from 3.2 to 8.4 minutes. Monocular acuity norms were calculated using 95% and 99% prediction limits. The new norms spanned higher spatial frequencies than the preliminary ACP norms between ages 1 month and 18 months but were similar between 24 and 36 months. The lower normal 2.5% limits were similar to lower limits of other normative studies. The interocular acuity difference was zero or 0.5 octave in 99% of subjects of all ages. Acuities obtained by the same tester on different days and by different testers on the same day were within 0.5 octave in at least 90% of subjects, comparable to previous studies.

CONCLUSIONS

This study provides monocular acuity norms that are appropriate for clinical settings in which the ACP and TAC are used and should replace the preliminary ACP norms.

Preferential looking--clinical lessons

Preferential looking-based tests of acuity have been available for over a decade. The authors discuss their use in clinical practice, particularly in three groups in whom acuity could not be quantified by traditional means: normal infants, and young children who are either mentally retarded, or who have visual disorders. Preferential looking (PL) testing has increased our understanding of the natural history of visual pathway disorders and has revealed certain patterns of acuity development. Early acuity development may be normal, delayed, or stationary, while in later infancy and childhood the following abnormal patterns have been identified: asymptotic, parallel, catch-up, or regressing. While this information has introduced a degree of complexity hitherto unknown which, if misunderstood, can lead to test misinterpretation, it offers the clinician invaluable information to improve patient care, and may also offer clues to the fundamental mechanisms of visual development.

Visual development of infants with severe ocular disorders

Among 11 patients who presented as blind in early infancy, with Leber's congenital amaurosis (5 patients), optic nerve hypoplasia (4 patients), or macular colobomata (2 patients), 8 developed visually guided behavior and measurable grating acuity by age 5 to 46 months. All children with measurable grating acuity demonstrated visually guided mobility. Grating acuity was predictive of later visual performance in 10 of 11 patients by age 12 to 16 months. The best grating acuity attained by 7 months was 1.3 to 3.0 cycles/degrees (20/460 to 20/200) and 0.13 cycles/degrees (20/4700) by month 8. Two patients with Leber's congenital amaurosis and one with optic nerve hypoplasia remained blind. No clinical features existed to differentiate these three patients from the eight whose visual status improved. Posterior visual pathway maturation may underlie the improvement.

Modified Allen pictures to assess amblyopia in young children

To produce a test of visual acuity for young children that is more sensitive to amblyopia than current preschool vision tests, the authors surrounded four Allen pictures with "crowding" bars. This modified Allen test was evaluated by measuring acuity of amblyopic children (n = 28) and children (n = 10) and adults (n = 5) with normal eyes. Mean acuities of amblyopic eyes for the modified pictures was 0.8 octaves or nearly three logMar Snellen lines poorer than for the isolated pictures. For nonamblyopic and normal eyes modified picture acuity averaged 0.1 to 0.4 octaves poorer than isolated picture acuity. Average acuities of amblyopic eyes (n = 22) for the modified pictures agreed with line letter acuities. These results suggest that the modified picture test induces contour interaction similar to that of line letter tests, and thus, is a more sensitive test of amblyopia in the preschool child than isolated symbols.

Assessment of vision and amblyopia by preferential looking tests after early surgery for unilateral congenital cataracts

Preferential looking tests obtained over the first 3 years were used to evaluate the development of visual acuity of 21 patients who underwent surgery for unilateral congenital cataracts and fitting of contact lenses before age 6 months. Mean acuity of the aphakic eyes improved rapidly in the first year; however, between the end of the first year and the end of the third year there was no improvement in mean aphakic acuity. Consistent with this, the percentage of patients who were amblyopic by the criterion interocular difference in acuity (IOD) of 0.5 octaves (oct) or greater was 94% at the first test age near the onset of occlusion therapy, decreased to 72% at the end of year 1, and increased to 89% by the end of year 3. Variations in occlusion therapy appear to account for these results: mean hours of occlusion per day were 6.2 in year 1, 4.4 in year 2, and 2.7 hours in year 3. Furthermore, the IOD at age 1 year was negatively correlated with hours of occlusion in the first year and the IOD at age 3 years was negatively correlated with cumulated hours of occlusion over all 3 years. That is, the less the amount of occlusion therapy, the greater the IOD. The patients' ages at time of surgery did not account for any further variance in these results than that accounted for by occlusion therapy. This study demonstrates that PL acuity measurement can aid in monitoring the response to occlusion therapy of infants with deprivation amblyopia due to unilateral congenital cataracts.

Visual acuities and dark-adapted thresholds of children with Bardet-Biedl syndrome

We studied the visual acuities and dark-adapted sensitivities of 12 children with Bardet-Biedl syndrome. All except one child, who was seen only once, were tested serially. In the first decade of life, all visual acuities were within 2 octaves of normal. All but two final visual acuities obtained from patients in their second and third decades were more than 2 octaves poorer than normal. Dark-adapted sensitivities of all patients were, or became, significantly less than normal even in those patients whose period of follow-up was limited to the first decade of life. Of the 11 patients measured serially, seven showed decreases in dark-adapted sensitivities of at least 0.5 log unit during the follow-up period, and the last measured sensitivities of all patients were at least 2 log units less than the normal mean.

Visual fields of young children

A light-emitting diode (LED) perimeter and forced-choice procedures are described that enable quantitative assessment of peripheral visual fields of young children. The visual fields of normal children, aged 2-5 years, and adults are compared. There are no significant differences in the extent of the LED visual field of the children and the adults. For selected neuro-ophthalmology patients, results of LED and kinetic Goldmann perimetry have been compared. The patients' LED and Goldmann fields are similar in overall extent. In all cases, field defects demonstrated by Goldmann perimetry are detected by LED perimetry. However, discrepancies in the severity of quandrantanopic defects of a patient have been discovered that may be stimulus-dependent.

Esotropic children with amblyopia: effects of patching on acuity

The rates of improvement of acuity in response to full-time occlusion therapy of 30 esotropic patients with amblyopia were determined. The children's ages at the time of full-time patching ranged from about 3 to 10 years. In keeping with clinical experience, the rate of acuity improvement during patching was slower for older than younger patients. The age-related changes in responsiveness to patching were modeled nonlinearly to provide quantitative guidelines for management of occlusion therapy of esotropic children with amblyopia.

Visual fields of infants assessed with a new perimetric technique

The visual field of normal infants was assessed using a perimeter with LED stimuli and a forced-choice observation procedure. Central fixation was elicited by four central, pulsing LEDs and maintained with the aid of auditory stimuli. Field extent was derived from the four-alternative, forced-choice judgments of an adult who observed the infant's eye movements to peripherally illuminated LEDs. The binocular visual field of infants, ages 6-7 months, was similar to that of adults tested with the same apparatus. Area of the infants' binocular field was 93% that of the adults'. However, the infants' monocular fields were smaller than those of adults, averaging 74% of the adults' monocular field area. This may have been due to the distracting effect on infant behavior of the adhesive patch used for monocular testing. The visual fields of a young patient with hydrocephalus illustrate the potential clinical utility of this new perimetric technique for infants at risk of field defects.

Results of early treatment of unilateral congenital cataracts

Twelve infants with unilateral congenital cataracts treated at Boston Children's Hospital between 1978 and 1986 have now reached the age of 3.5 years or older. All infants had cataract extractions, aphakic contact lens fitting, and occlusion of the unaffected eye by 6 months of age. Patients with posterior lenticonus or persistent hyperplastic primary vitreous were excluded from this review. Early improvement of visual acuity in the aphakic eye was monitored by preferential looking tests, and occlusion of the sound eye was adjusted accordingly. E card visual acuities are now available on all 12 children. Five patients have 20/70 or better visual acuity, three patients have between 20/100 and 20/400 vision, and four patients have less than 20/400 in the aphakic eye. Two patients whose cataract surgery was done after 4 months of age had the poorest visual results. Difficulty maintaining occlusion therapy and interruptions of contact lens wear limited the development of better vision in some patients. The visual results to date in these 12 patients suggest that early aggressive treatment of unilateral congenital cataracts is worthy of consideration in most instances.

Oscillatory potentials of visually inattentive children

The oscillatory potentials (OPs) are probably generated in the proximal retina. The OPs of 20 visually inattentive infants and children were recorded. All 20 had evidence of abnormalities of the visual parts of the brain. The a- and b-waves, indices of distal retinal function, were normal in 10 patients, abnormal in the other 10. Among the patients with abnormal, attenuated a- and b-waves, OP amplitudes were more attenuated than among those with normal a- and b-waves. However, the timing of the OP wavelets was not correlated with distal retinal activity. These results suggest that in humans OP amplitude may be determined by inputs from the distal retina, but OP latency and periodicity are governed by processes within the proximal retina.

Acuity of amblyopic children for small field gratings and recognition stimuli

Tests of grating acuity often underestimate amblyopia and underrefer esotropic infants with a fixation preference. To evaluate the effect of the large grating field used in preferential looking (PL) procedures, an eight-alternative, small field (about 1 degrees) grating acuity test was devised. Gratings contained at least eight cycles. Thirty-seven strabismic and/or anisometropic amblyopes, ages 3-13 yr, were tested. In most amblyopic eyes, grating acuities were better than recognition acuities; the difference was reduced, however, in the small field test compared to the large field (6 degrees test (means, 1 oct vs. 1.6 oct; paired-t = 5.5, P less than .001). Nevertheless, the same relation between grating and recognition acuities occurred for small as for large fields: an increased discrepancy between grating and recognition acuities accompanied poorer acuity. This larger discrepancy is attributed to increased probability summation of amblyopic eyes for low spatial frequencies. For preschool children who can be tested by both procedures, the eight-alternative grating acuity test may be preferable to operant PL because it is more easily administered and materials are simpler.

Assessment of young amblyopes. Array vs. single picture acuities

A linear array of intact and "jumbled" symbols suitable for testing young children has been used to evaluate 35 young amblyopes. Acuities with the jumbled array test were poorer than those obtained with single symbols: the discrepancy between the jumbled array and single picture acuities was greater for large acuity deficits than small deficits. The depth of amblyopia, indexed by the interocular difference in acuity, was greater for the jumbled array than single pictures. For the patients who could be tested with lines of Snellen letters the jumbled array acuities were closer to line letter acuities than single picture or grating acuities. These results suggest that the jumbled array provides a more sensitive test of amblyopia in young children than single symbols or gratings, possibly because the jumbled array presents contour interactions that exploit the crowding phenomenon.

Visual acuity screening of children 6 months to 3 years of age

The operant preferential looking (OPL) procedure allows a behavioral estimate of visual acuity to be obtained from children 6 mo to 3 yr of age. In clinical settings, there is often too little time available to obtain an acuity estimate with the standard OPL procedure. The goal of this study was to identify specific spatial frequencies, termed diagnostic grating frequencies, that could enable the OPL technique to be used as a screening procedure under conditions where completion of acuity estimation was not possible. One hundred eighty presumptively normal children, 6, 12, 18, 24, 30, and 36 mo of age, were each tested with up to 20 trials of a potential diagnostic grating frequency to determine the highest spatial frequency grating that could be resolved by 90% of children at each age. For all ages except 18 mo, there existed a spatial frequency that produced uniformly high OPL performance within the age group; this spatial frequency was separated by one-half to one octave from a higher spatial frequency that more than 30% of children at that age failed to detect. These results suggest that at all ages except 18 mo, it should be possible to use the OPL procedure as a vision screening tool by testing individual children with the diagnostic grating frequency appropriate for their age.

Visual acuity of infants and children with retinal degenerations

Visual acuity for gratings was studied in 18 infants and children with generalized retinal degenerations using preferential looking (PL) procedures. Diagnoses were Leber's congenital amaurosis (12), Laurence-Moon-Bardet-Biedl-like syndromes (4) and metabolic disorders (2). ERG's were extinguished in 11 patients and much attenuated in seven patients. Acuities at all ages (two months to 12 years) were significantly poorer than normal, and patients with extinguished ERG's had the poorest acuity. Neurological abnormality or mental retardation, present in ten patients, was as likely in patients with 6/60 or poorer grating acuity as in patients with better than 6/60 acuity. A comparison group of 12 infants and children with oculocutaneous albinism showed significantly better grating acuities than the patients with retinal degeneration. Relatively good grating acuity in infants with no anatomic fovea (oculocutaneous albinism) and much poorer acuities of infants with generalized retinal degeneration suggest that parafoveal or peripheral retina is necessary and sufficient for normal, behaviorally-obtained grating acuity in infancy.

Grating and recognition acuities of pediatric patients

Acuities for gratings obtained by preferential looking (PL) that differed from expectations based upon the ophthalmologic examination prompted this study. Older pediatric patients (124 patients; mean age, 6.5 years) were tested by the PL grating test and a test of recognition acuity (pictures or letters). On the average, grating acuity was better than recognition acuity. In patients with dense amblyopia or foveal abnormalities, very large discrepancies between grating and recognition acuities were found. In nonamblyopic patients, acuities were no more discrepant than for children with normal eyes. Amblyopia was less dense by grating acuities than by recognition acuities; grating acuities were sensitive, however, to refractive and organic amblyopia but not to strabismic amblyopia. Possible explanations include the heterogeneity of patients' eye disorders, single vs. linear acuity, stimulus size and relative complexity of stimuli. These results can aid in evaluating PL grating acuities of preverbal patients, and suggest modifications of stimuli to investigate amblyogenesis.

Preferential looking acuity of pediatric patients with developmental disabilities

The grating acuity of 181 patients from 6 weeks to 18 years of age who had neurological abnormalities and documented developmental delay was assessed using preferential looking (PL) procedures. PL acuities were estimated by a staircase procedure in 79% of all patients (143 of 181) on the first attempt. PL acuities were poorer than normal on the average in all patient groups, including those without ophthalmological disorders. However, PL acuities varied systematically with the severity of the eye disorder in each category, with two exceptions, high refractive error and nystagmus. Interocular acuity differences were sensitive to such asymmetric eye disorders as strabismic amblyopia and unilateral ocular abnormalities and enabled monitoring of occlusion therapy for these conditions. Many patients who were 'visually inattentive' despite the absence of major ophthalmological abnormalities were testable but had very poor acuity. This study evaluates the clinical applicability of PL procedures for routine assessment of visual acuity in pediatric patients with developmental disabilities.

Preferential looking vision testing: application to evaluation of high-risk, prematurely born infants and children

We studied the application of preferential looking (PL) procedures to evaluation of visual performance of 59 prematurely born infants and young children. Neurological abnormalities were present in 29 of the 59 patients. Ophthalmic examination revealed normal eyes in 20 of the patients; retinopathy of prematurity (20 patients) and strabismus (13 patients) were the most prevalent ophthalmological disorders; the remaining 6 patients had a variety of ophthalmic anomalies. Results indicate that PL testing of such patients is best accomplished after age 2 months. Patients with developmental delays can be tested, but they may have poor PL performance that is not accounted for by ophthalmic abnormalities. Differences in PL acuities between right and left eyes were indicative of amblyopia in some of the strabismic patients; sequential PL acuities monitored occlusion therapy in these pre-verbal youngsters.

Preferential looking acuity obtained with a staircase procedure in pediatric patients

Visual acuity of infants and young children with ophthalmologic disorders was assessed by adapting a transformed up-down staircase to preferential looking (PL) procedures. Eighty-five percent of pediatric patients between 11 days and 5 years of age were tested successfully. Acuity of infants and young children with normal eyes obtained by the PL staircase procedure agreed well with acuities obtained previously by the method of constant stimuli. In children with anisometropia, differences in acuity between eyes varied systematically with the amount of anisometropia. Monocular acuities of untreated patients with strabismus did not always agree with fixation preference. In general, test results from pediatric patients with structural ocular abnormalities were consistent with the severity of the disorder. By means of serial measurement of PL acuity, the therapy of patients with amblyopia was monitored. In our young patients, anisometropic amblyopia affected grating acuity differently than did strabismic amblyopia, as others have reported in older patients with these conditions. Our results indicate that the PL staircase procedure provides a useful measure of visual acuity in pediatric ocular disorders that can complement the clinical evaluation of infants and young children.

Visual acuity screening of preterm infants

Visual acuity was screened in 36 healthy infants born 4 or more weeks prior to term. Preterm infants tested at 8 and 12 weeks of postnatal age showed significantly poorer performances than those shown by 8- and 12-week-old full-term infants. However, no differences in performance were found when the scores of preterm infants tested at 4, 8, and 12 weeks of postterm age (i.e., 4, 8, and 12 weeks from due date) were compared with scores of 4-, 8-, and 12-week-old full-term infants. The results suggest that visual acuity is more closely correlated with age from conception than with age from birth and that visual acuity screening in preterm infants should be carried out with acuity gratings appropriate for the infant's postterm age rather than with acuity gratings appropriate for the infant's postnatal age.

Assessment of vision in young children: a new operant approach yields estimates of acuity

Behavorial assessment of visual function is now possible in 6- to 24-month-old children through the use of an operant preferential looking technique. Use of the technique to measure grating acuity shows that acuity develops from 6 to 8 min arc at 6 months of age to near adult levels by 2 years.

Astigmatism and acuity in two primate infants

The development of grating acuity was followed in two astigmatic primate infants, one a human being and one a pigtail macaque monkey. Both infants showed variations of acuity with grating orientation, predictable from the orientation and type of astigmatism present. Optical correction of the human infant during testing virtually eliminated the variation of acuity with orientation, suggesting that a neurally based meridional amblyopia had not yet been established.