The Fovea in Retinopathy of Prematurity

Purpose

Because preterm birth and retinopathy of prematurity (ROP) are associated with poor visual acuity (VA) and altered foveal development, we evaluated relationships among the central retinal photoreceptors, postreceptor retinal neurons, overlying fovea, and VA in ROP.

Methods

We obtained optical coherence tomograms (OCTs) in preterm born subjects with no history of ROP (none; n = 61), ROP that resolved spontaneously without treatment (mild; n = 51), and ROP that required treatment by laser ablation of the avascular peripheral retina (severe; n = 22), as well as in term born control subjects (term; n = 111). We obtained foveal shape descriptors, measured central retinal layer thicknesses, and demarcated the anatomic parafovea using automated routines. In subsets of these subjects, we obtained OCTs eccentrically through the pupil (n = 46) to reveal the fiber layer of Henle (FLH) and obtained adaptive optics scanning light ophthalmograms (AO-SLOs) of the parafoveal cones (n = 34) and measured their spacing and distribution.

Results

Both VA and foveal depth decreased with increasing ROP severity (term, none, mild, severe). In severe subjects, foveae were broader than normal and the parafovea was significantly enlarged compared to every other group. The FLH was thinner than normal in mild (but not severe) subjects. VA was associated with foveal depth more than group. Density of parafoveal cones did not differ significantly among groups.

Conclusions

Foveal structure is associated with loss of VA in ROP. The preserved FLH in severe (relative to mild) eyes suggests treatment may help cone axon development. The significantly larger parafovea and increased outer nuclear layer (ONL) thickness in ROP hint that some developmental process affecting the photoreceptors is not arrested in ROP but rather is supranormal.

Dark-adapted threshold and electroretinogram for diagnosis of Usher syndrome

PURPOSE

To determine the utility of ophthalmology evaluation, dark-adapted threshold, and full-field electroretinogram for early detection of Usher syndrome in young patients with bilateral sensorineural hearing loss.

METHODS

We identified 39 patients with secure genetic diagnoses of Usher Syndrome. Visual acuity, spherical equivalent, fundus appearance, dark-adapted threshold, and full-field electroretinogram results were summarized and compared to those in a group of healthy controls with normal hearing. In those Usher patients with repeated measures, regression analysis was done to evaluate for change in visual acuity and dark-adapted threshold with age. Spherical equivalent and full-field electroretinogram responses from dark- and light-adapted eyes were evaluated as a function of age.

RESULTS

The majority of initial visual acuity and spherical equivalent results were within normal limits for age. Visual acuity and dark-adapted threshold worsened significantly with age in Usher type 1 but not in Usher type 2. At initial test, full-field electroretinogram responses from dark- and light-adapted eyes were abnormal in 53% of patients. Remarkably, nearly half of our patients (17% of Usher type 1 and 30% of Usher type 2) would have been missed by tests of retinal function alone if evaluated before age 10.

CONCLUSIONS

Although there is an association of abnormal dark-adapted threshold and full-field electroretinogram at young ages in Usher patients, it appears that a small but important proportion of patients would not be detected by tests of retinal function alone. Thus, genetic testing is needed to secure a diagnosis of Usher syndrome.

1172 Sleep Education Improves Screening for Sleep Disorders Among Physicians and Residents in Primary Care and Neurology Specialties

Introduction

Sleep disorders are under-diagnosed. The purpose of the study was to evaluate if providing sleep education improves screening and thereby, diagnosis of sleep disorders among physicians.

Methods

The study was approved by the institutional review board. Pediatric (P), neurology (N) and internal medicine (IM) physicians/residents participated in the study. After collecting demographics, including baseline screening rates (BSR), the participants were randomized to educational intervention- either manuscript or oral presentation reviewing insomnia, obstructive sleep apnea and sleep disorders in epilepsy. Questionnaires-baseline knowledge (BQ), post-intervention (PQ) and 9 months after the intervention, screening (SQ) evaluating screening rates (PSR) and usefulness of the study, were collected. The change in knowledge (PQ-BQ) and screening rates (PSR-BSR) were compared between the groups by t-test and ANCOVA after adjusting for BSR. t-tests were used to compare the knowledge and screening rates before and after the intervention in the entire cohort. Correlations identified the factors associated with improved screening rates.

Results

Thirty and 23 subjects completed the study and SQ, respectively. The average age was 30.4 (standards deviation [SD]= 3.1) with 53% female and practice experience of 2.5 years (SD=1.7) with 60% P, 23.3% N and 16.7% IM participants. There were no significant differences in the characteristics, and knowledge and screening rate change after the intervention between the two groups. However, for individual questions, the oral presentation group had improved knowledge about sleep disorders in epilepsy. The study improved knowledge by 82% for understanding, 77% for managing and 79% for screening for sleep disorders. Knowledge (Mean Difference [MD]= 0.22, p=0.0001) and screening rates (MD=0.29, p=0.001) improved significantly after the intervention in the entire cohort. The improvement in screening rates was associated with presence of screening by the physicians prior to the intervention (r=0.5, p=0.008).

Conclusion

The study showed that sleep education improved knowledge and screening for sleep disorders among physicians.

Support

The study was funded by the American Academy of Sleep Medicine Foundation Focused Project Award.

Impact of Obstructive Sleep Apnea on Optic Nerve Function in Patients With Craniosynostosis and Recurrent Intracranial Hypertension

PURPOSE

Assessment of combined impact of intracranial hypertension (ICH) and obstructive sleep apnea (OSA) on optic nerve function in children with craniosynostosis (CS).

DESIGN

Retrospective cross-sectional study.

METHODS

Patients treated at Boston Children's Hospital for CS who had an ophthalmic examination that included pattern reversal (pr)VEP (2013-2014) and history of ICH based on direct measurement, papilledema, or classic features on neuroimaging and during cranial vault expansion were included. History of OSA was determined by polysomnography and associated conditions, including apnea and (adeno)tonsillectomy. Subjects were divided into 4 groups: group 1, resolved ICH absent history of OSA; group 2, resolved ICH with history of OSA; group 3, recurrent ICH absent history of OSA; and group 4, recurrent ICH with history of OSA. Predictor variables included latency of P100 component of pattern-reversal visual evoked potential, best-corrected visual acuity, optic nerve appearance, visual fields, and global retinal nerve fiber layer. Primary outcome was association of prolonged P100 latency with resolved vs recurrent ICH and OSA.

RESULTS

Twenty-eight children met inclusion criteria (mean age 11.6 ± 6.9 years): group 1 (n = 3), group 2 (n = 6), group 3 (n = 8), and group 4 (n = 11). P100 latencies were not prolonged in groups 1 and 2. Three of 8 in group 3 and 9 of 11 in group 4 had prolonged P100 latency. Group 4 was significantly worse than group 3 (P = .005).

CONCLUSIONS

History of OSA, in addition to recurrent ICH, is associated with greatest risk of optic neuropathy with CS. Ophthalmologists should encourage early management of OSA as well as ICH to optimize ophthalmic outcomes.

Survival, disease progression and prognostic factors in elderly patients with mycosis fungoides and Sézary syndrome: a retrospective analysis of 174 patients

BACKGROUND

Advanced age at diagnosis is considered a poor prognostic factor in mycosis fungoides (MF) and Sézary syndrome (SS).

OBJECTIVE

To evaluate the outcomes and prognostic factors in patients diagnosed at an advanced age (≥65 years) with MF/SS.

METHODS

Survival, progression rates and various clinical and histopathological variables were studied in a group of 174 elderly patients diagnosed with MF/SS between 1992 and 2015 at a single referral cancer center in the United States. Kaplan-Meier estimates were used to determine survival and progression and Cox proportional hazards regression univariate and multivariate models were used to identify prognostic factors.

RESULTS

Of 174 elderly patients, 76.4% were diagnosed with early-stage (clinical stages IA-IIA) and 23.6% with late-stage MF/SS (IIB-IV). Advanced age was associated with poor overall survival, but not with disease-specific survival (DSS) or progression-free survival (PFS). Gender, increasing clinical stage, T and B classifications, elevated lactate dehydrogenase (LDH) levels and development of large cell transformation (LCT) were significant predictors of poor survival or disease progression. Patients with early-stage MF and <10% total skin involvement (T1 classification) or patch-only disease (T1a/T2a) showed better PFS with no observed disease-specific mortality. Folliculotropic MF was associated with poor DSS in patients with early-stage disease.

CONCLUSIONS

Older age at diagnosis of MF/SS does not predict worse disease-specific outcomes. Elderly patients with early-stage disease, specifically involving less than 10% of the skin surface with patches but without plaques or folliculotropism, have an excellent prognosis. However, the development of LCT is a strong prognostic indicator of poor survival in elderly patients with MF/SS.

Multifocal ERG Responses in Subjects With a History of Preterm Birth

Purpose

The purpose of this study is to assess cone-mediated central retinal function in children with a history of preterm birth, including subjects with and without retinopathy of prematurity (ROP). The multifocal electroretinogram (mfERG) records activity of the postreceptor retinal circuitry.

Methods

mfERG responses were recorded to an array of 103 hexagonal elements that subtended 43° around a central fixation target. The amplitude and latency of the first negative (N1) and first positive (P1) response were evaluated in six concentric rings centered on the fovea. Responses were recorded from 40 subjects with a history of preterm birth (severe ROP, mild ROP, no ROP) and 19 term-born control subjects.

Results

The amplitude of N1 and P1 varied significantly with eccentricity and ROP severity. For all four groups, these amplitudes were largest in the center and decreased with eccentricity. At all eccentricities, N1 amplitude was significantly smaller in severe ROP and did not differ significantly among the other three groups (mild ROP, no ROP, term-born controls). P1 amplitude in all preterm groups was significantly smaller than in controls; P1 amplitude was similar in no ROP and mild ROP and significantly smaller in severe ROP.

Conclusions

These results provide evidence that premature birth alone affects cone-mediated central retinal function and that the magnitude of the effect varies with severity of the antecedent ROP. The lack of difference in mfERG amplitude between the mild and no ROP groups is evidence that the effect of ROP on the neurosensory retina may not depend solely on appearance of abnormal retinal vasculature.

Increment Threshold Functions in Retinopathy of Prematurity

PURPOSE

To assess scotopic background adaptation in subjects with a history of preterm birth and retinopathy of prematurity (ROP). Retinopathy of prematurity is known to have long-term effects on rod photoreceptor and rod mediated postreceptor retinal function.

METHODS

Rod-mediated thresholds for detection of 3° diameter, 50 ms stimuli presented 20° from fixation were measured using a spatial forced choice method in 36 subjects (aged 9-17 years) with a history of preterm birth and 11 age similar term-born subjects. Thresholds were measured first in the dark-adapted condition and then in the presence of 6 steady background lights (-2.8 to +2.0 log scot td). A model of the increment threshold function was fit to each subject's thresholds to estimate the dark-adapted threshold (TDA) and the Eigengrau (A0, the background that elevates threshold 0.3 log unit above TDA).

RESULTS

In subjects with a history of severe ROP, both TDA and A0 were significantly elevated relative to those in former preterms who never had ROP and term-born control subjects. Subjects who had mild ROP had normal TDA but elevated A0. Neither TDA nor A0 differed significantly between former preterms who never had ROP and term-born controls.

CONCLUSIONS

The results suggest that in severe ROP, threshold is affected at a preadaptation site, possibly the rod outer segment. In mild ROP, changes in the Eigengrau may reflect increased intrinsic noise in the photoreceptor or postreceptor circuitry or both.

Juvenile Macular Degenerations

In this article, we review the following 3 common juvenile macular degenerations: Stargardt disease, X-linked retinoschisis, and Best vitelliform macular dystrophy. These are inherited disorders that typically present during childhood, when vision is still developing. They are sufficiently common that they should be included in the differential diagnosis of visual loss in pediatric patients. Diagnosis is secured by a combination of clinical findings, optical coherence tomography imaging, and genetic testing. Early diagnosis promotes optimal management. Although there is currently no definitive cure for these conditions, therapeutic modalities under investigation include pharmacologic treatment, gene therapy, and stem cell transplantation.

The neural retina in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a neurovascular disease that affects prematurely born infants and is known to have significant long term effects on vision. We conducted the studies described herein not only to learn more about vision but also about the pathogenesis of ROP. The coincidence of ROP onset and rapid developmental elongation of the rod photoreceptor outer segments motivated us to consider the role of the rods in this disease. We used noninvasive electroretinographic (ERG), psychophysical, and retinal imaging procedures to study the function and structure of the neurosensory retina. Rod photoreceptor and post-receptor responses are significantly altered years after the preterm days during which ROP is an active disease. The alterations include persistent rod dysfunction, and evidence of compensatory remodeling of the post-receptor retina is found in ERG responses to full-field stimuli and in psychophysical thresholds that probe small retinal regions. In the central retina, both Mild and Severe ROP delay maturation of parafoveal scotopic thresholds and are associated with attenuation of cone mediated multifocal ERG responses, significant thickening of post-receptor retinal laminae, and dysmorphic cone photoreceptors. These results have implications for vision and control of eye growth and refractive development and suggest future research directions. These results also lead to a proposal for noninvasive management using light that may add to the currently invasive therapeutic armamentarium against ROP.

Extrafoveal Cone Packing in Eyes With a History of Retinopathy of Prematurity

Purpose

To study the density and packing geometry of the extrafoveal cone photoreceptors in eyes with a history of retinopathy of prematurity (ROP). We used a multimodal combination of adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT).

Methods

Cones were identified in subjects (aged 14–26 years) with a history of ROP that was either severe and treated by laser ablation of avascular peripheral retina (TROP; n = 5) or mild and spontaneously resolved, untreated (UROP; n = 5), and in term-born controls (CT; n = 8). The AO-SLO images were obtained at temporal eccentricities 4.5°, 9°, 13.5°, and 18° using both confocal and offset apertures with simultaneous, colocal OCT images. Effects of group, eccentricity, and aperture were evaluated and the modalities compared.

Results

In the SLO images, cone density was lower and the packing pattern less regular in TROP, relative to CT and UROP retinae. Although SLO image quality appeared lower in TROP, root mean square (RMS) wavefront error did not differ among the groups. In TROP eyes, cone discrimination was easier in offset aperture images. There was no evidence of cone loss in the TROP OCT images.

Conclusions

Low cone density in TROP confocal SLO images may have resulted from lower image quality. Since AO correction in these eyes was equivalent to that of the control group, and OCT imaging showed no significant cone loss, the optical properties of the inner retina or properties of the cones themselves are likely altered in a way that affects photoreceptor imaging.

Retinal, visual, and refractive development in retinopathy of prematurity

The pivotal role of the neurosensory retina in retinopathy of prematurity (ROP) disease processes has been amply demonstrated in rat models. We have hypothesized that analogous cellular processes are operative in human ROP and have evaluated these presumptions in a series on non-invasive investigations of the photoreceptor and post-receptor peripheral and central retina in infants and children. Key results are slowed kinetics of phototransduction and deficits in photoreceptor sensitivity that persist years after ROP has completely resolved based on clinical criteria. On the other hand, deficits in post-receptor sensitivity are present in infancy regardless of the severity of the ROP but are not present in older children if the ROP was so mild that it never required treatment and resolved without a clinical trace. Accompanying the persistent deficits in photoreceptor sensitivity, there is increased receptive field size and thickening of the post-receptor retinal laminae in the peripheral retina of ROP subjects. In the late maturing central retina, which mediates visual acuity, attenuation of multifocal electroretinogram activity in the post-receptor retina led us to the discovery of a shallow foveal pit and significant thickening of the post-receptor retinal laminae in the macular region; this is most likely due to failure of the normal centrifugal movement of the post-receptor cells during foveal development. As for refractive development, myopia, at times high, is more common in ROP subjects than in control subjects, in accord with refractive findings in other populations of former preterms. This information about the neurosensory retina enhances understanding of vision in patients with a history of ROP, and taken as a whole, raises the possibility that the neurosensory retina is a target for therapeutic intervention.

Eye growth in term- and preterm-born eyes modeled from magnetic resonance images

PURPOSE

We generated a model of eye growth and tested it against an eye known to develop abnormally, one with a history of retinopathy of prematurity (ROP).

METHODS

We reviewed extant magnetic resonance images (MRIs) from term and preterm-born patients for suitable images (n = 129). We binned subjects for analysis based upon postmenstrual age at birth (in weeks) and ROP history ("Term" ≥ 37, "Premature" ≤ 32 with no ROP, "ROP" ≤ 32 with ROP). We measured the axial positions and curvatures of the cornea, anterior and posterior lens, and inner retinal surface. We fit anterior chamber depth (ACD), posterior segment depth (PSD), axial length (AL), and corneal and lenticular curvatures with logistic growth curves that we then evaluated for significant differences. We also measured the length of rays from the centroid to the surface of the eye at 5° intervals, and described the length versus age relationship of each ray, L(ray)(x), using the same logistic growth curve. We determined the rate of ray elongation, E(ray)(x), from L(ray)dy/dx. Then, we estimated the scleral growth that accounted for E(ray)(x), G(x), at every age and position.

RESULTS

Relative to Term, development of ACD, PSD, AL, and corneal and lenticular curvatures was delayed in ROP eyes, but not Premature eyes. In Term infants, G(x) was fast and predominantly equatorial; in age-matched ROP eyes, maximal G(x) was offset by approximately 90°.

CONCLUSIONS

We produced a model of normal eye growth in term-born subjects. Relative to normal, the ROP eye is characterized by delayed, abnormal growth.

Temporal summation in children with a history of retinopathy of prematurity

PURPOSE

To assess temporal summation in children with a history of retinopathy of prematurity (ROP) by determining the critical duration (tCRIT) for complete temporal summation under rod-mediated conditions. From prior ERG studies, it is known that the kinetics of activation of phototransduction are prolonged in the ROP rod photoreceptor.

METHODS

Dark-adapted thresholds for detecting 10° diameter stimuli with durations from 10 to 640 ms were measured. A two-alternative, spatial, forced-choice psychophysical procedure was used. The tCRIT for complete summation was estimated in former preterm subjects with a history of severe ROP (n = 7), mild ROP (n = 23), and no ROP (n = 15). The subjects ranged in age from 10.4 to 17.6 (median 15.6) years. Age-similar term-born control subjects (n = 5) were also tested.

RESULTS

Critical duration was significantly longer in subjects with a history of ROP than in subjects who never had ROP or who were born at term. Mean tCRIT in the mild ROP group [127.5 (SD = 19.9) ms] and severe group [147.6 (SD = 18.9) ms] did not differ significantly, but both were significantly longer than in former preterms who never had ROP [101.1 (SD = 16.5) ms] and in term-born controls [101.0 (SD = 19.5) ms].

CONCLUSIONS

In ROP subjects, tCRIT is significantly prolonged. This is likely due to abnormal kinetics in the rod outer segment.

Effect of retinopathy of prematurity on scotopic spatial summation

PURPOSE

To evaluate scotopic retinal organization in retinopathy of prematurity (ROP) through a study of spatial summation.

METHODS

Thresholds for a range of stimulus diameters (0.4°-10°) were measured using a two alternative, spatial, forced choice psychophysical procedure. The critical diameter (DCRIT) for complete summation was estimated in subjects with a history of severe ROP (N = 7) and mild ROP (N = 17). Subjects who were born preterm and never had ROP (N = 16) and term-born subjects (N = 7) were also tested. The subjects ranged in age from 9 to 17 (median 13.5) years.

RESULTS

Critical diameter for complete spatial summation was significantly larger in ROP subjects than in subjects who never had ROP and in term-born control subjects. Critical diameter varied significantly with severity of ROP.

CONCLUSIONS

The larger DCRIT values in ROP are consistent with altered organization of the post receptor retina. This may offer the ROP retina a strategy for achieving noise reduction and good dark-adapted visual sensitivity.

Prognosis in HIV-infected patients with non-small cell lung cancer

Background:

We conducted a population-based study to evaluate whether non-small cell lung cancer (NSCLC) prognosis was worse in HIV-infected compared with HIV-uninfected patients.

Methods:

Using the Surveillance, Epidemiology and End Results (SEER) registry linked to Medicare claims, we identified 267 HIV-infected patients and 1428 similar controls with no evidence of HIV diagnosed with NSCLC between 1996 and 2007. We used conditional probability function (CPF) analyses to compare survival by HIV status accounting for an increased risk of non-lung cancer death (competing risks) in HIV-infected patients. We used multivariable CPF regression to evaluate lung cancer prognosis by HIV status adjusted for confounders.

Results:

Stage at presentation and use of stage-appropriate lung cancer treatment did not differ by HIV status. Median survival was 6 months (95% confidence interval (CI): 5–8 months) among HIV-infected NSCLC patients compared with 20 months (95% CI: 17–23 months) in patients without evidence of HIV. Multivariable CPF regression showed that HIV was associated with a greater risk of lung cancer-specific death after controlling for confounders and competing risks.

Conclusion:

NSCLC patients with HIV have a poorer prognosis than patients without evidence of HIV. NSCLC may exhibit more aggressive behaviour in the setting of HIV.

Photoreceptor and postreceptor responses in congenital stationary night blindness

PURPOSE

To investigate photoreceptor and postreceptor retinal function in patients with congenital stationary night blindness (CSNB).

METHODS

Forty-one patients with CSNB (ages 0.19-32 years) were studied. ERG responses to a series of full-field stimuli were obtained under scotopic and photopic conditions and were used to categorize the CSNB patients as complete (cCSNB) or incomplete (iCSNB). Rod and cone photoreceptor (R(ROD), S(ROD), R(CONE), S(CONE)) and rod-driven postreceptor (V(MAX), log σ) response parameters were calculated from the a- and b-waves. Cone-driven responses to 30 Hz flicker and ON and OFF responses to a long duration (150 ms) flash were also obtained. Dark-adapted thresholds were measured. Analysis of variance was used to compare data from patients with cCSNB, patients with iCSNB, and controls.

RESULTS

We found significant reduction in saturated photoreceptor amplitude (R(ROD), R(CONE)) but normal photoreceptor sensitivity (S(ROD), S(CONE)) in both CSNB groups. Rod-driven postreceptor response amplitude (V(MAX)) and sensitivity (log σ) were significantly reduced in CSNB. Log σ was significantly worse in cCSNB than in iCSNB; this was the only scotopic parameter that differed between the two CSNB groups. Photopic b-wave amplitude increased monotonically with stimulus strength in CSNB patients rather than showing a normal photopic hill. The amplitude of the 30-Hz flicker response was reduced compared with controls, more so in iCSNB than in cCSNB. The mean dark-adapted threshold was significantly elevated in CSNB, more so in cCSNB than in iCSNB.

CONCLUSIONS

These results are evidence of normal photoreceptor function (despite the low saturated photoresponse amplitude) and anomalous postreceptor retinal circuitry.

Electroretinographic (ERG) responses in pediatric patients using vigabatrin

The antiepileptic drug vigabatrin is known to cause retinal and visual dysfunction, particularly visual field defects, in some patients. Electroretinography (ERG) is used in an attempt to identify adverse effects of vigabatrin (VGB) in patients who are not candidates for conventional perimetry. We report data from 114 pediatric patients taking VGB referred for clinical evaluation; median age at test was 22.9 (2.4 to 266.1) months, and median duration of VGB use was 9.7 (0.3 to 140.7) months. Twenty-seven of them were tested longitudinally (3 to 12 ERG tests). ERG responses to full-field stimuli were recorded in scotopic and photopic conditions, and results were compared to responses from healthy control subjects. We found that abnormalities of photoreceptor and post-receptor ERG responses are frequent in these young patients. The most frequently abnormal scotopic parameter was post-receptor sensitivity, log σ, derived from the b-wave stimulus-response function; the most frequently abnormal photopic parameter was the implicit time of the OFF response (d-wave) to a long (150 ms) flash. Abnormal 30-Hz flicker response amplitude, previously reported to be a predictor of visual field loss, occurred infrequently. For the group as a whole, none of the ERG parameters changed significantly with increasing duration of VGB use. Four of the 27 patients tested longitudinally showed systematic worsening of log σ with duration of VGB use. In a subset of patients who underwent perimetry (N = 39), there was no significant association of any ERG parameter with visual field defects. We cannot determine whether the ERG abnormalities we found were due solely to the effects of VGB. We caution against over-reliance on the ERG to monitor pediatric patients for VGB toxicity and recommend further development of a reliable test of peripheral vision to supplant ERG testing.

Cone ERG responses in patients with Smith-Lemli-Opitz Syndrome (SLOS)

PURPOSE

To evaluate cone and cone-driven retinal function in patients with Smith-Lemli-Opitz syndrome (SLOS), a condition characterized by low cholesterol. Rod and rod-driven function in patients with SLOS are known to be abnormal.

METHODS

Electroretinographic (ERG) responses to full-field stimuli presented on a steady, rod suppressing background were recorded in 13 patients who had received long-term cholesterol supplementation. Cone photoresponse sensitivity (S(CONE)) and saturated amplitude (R(CONE)) parameters were estimated using a model of the activation of phototransduction, and post-receptor b-wave and 30 Hz flicker responses were analyzed. The responses of the patients were compared to those of control subjects (N = 13).

RESULTS

Although average values of both S(CONE) and R(CONE) were lower than in controls, the differences were not statistically significant. Post-receptor b-wave amplitude and implicit time and flicker responses were normal.

CONCLUSIONS

The normal cone function contrasts with the significant abnormalities in rod function that were found previously in these same patients. Possibly, cholesterol supplementation has a greater protective effect on cones than on rods as has been demonstrated in the rat model of SLOS.

Deactivation of the rod response in retinopathy of prematurity

It is known that retinopathy of prematurity (ROP) alters the activation of rod photoreceptors, but the effect of ROP on deactivation has not been investigated. We studied deactivation using an electroretinographic (ERG) paired flash procedure in 22 subjects (12 infants and 10 older subjects) with a history of preterm birth and ROP. The amplitude of the rod-isolated a-wave response to a flash presented 2-120 s after a test flash was measured, and the time at which it reached 50% of the single flash amplitude (t(50)) was determined by linear interpolation. Deactivation results were compared to those in former preterms who never had ROP (n = 6) and term-born controls. In infants, t(50) values of ROP subjects did not differ from those in subjects who never had ROP or term-born controls. Among mature ROP subjects, eight of 12 had t(50) values longer than any control subject. Prolonged deactivation in these mature ROP subjects may indicate lack of maturation of the deactivation process (t(50)) or progressive compromise of retinal function with increasing age.

The neurovascular retina in retinopathy of prematurity

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP disease process. The age of onset of ROP coincides with the rapid developmental increase in rod photoreceptor outer segment length and rhodopsin content of the retina with escalation of energy demands. Using a combination of non-invasive electroretinographic (ERG), psychophysical, and image analysis procedures, the neural retina and its vasculature have been studied in prematurely born human subjects, both with and without ROP, and in rats that model the key vascular and neural parameters found in human ROP subjects. These data are compared to comprehensive numeric summaries of the neural and vascular features in normally developing human and rat retina. In rats, biochemical, anatomical, and molecular biological investigations are paired with the non-invasive assessments. ROP, even if mild, primarily and persistently alters the structure and function of photoreceptors. Post-receptor neurons and retinal vasculature, which are intimately related, are also affected by ROP; conspicuous neurovascular abnormalities disappear, but subtle structural anomalies and functional deficits may persist years after clinical ROP resolves. The data from human subjects and rat models identify photoreceptor and post-receptor targets for interventions that promise improved outcomes for children at risk for ROP.

Rod and rod-driven function in achromatopsia and blue cone monochromatism

PURPOSE

To evaluate rod photoreceptor and postreceptor retinal function in pediatric patients with achromatopsia (ACHR) and blue cone monochromatism (BCM) using contemporary electroretinographic (ERG) procedures.

METHODS

Fifteen patients (age range, 1-20 years) with ACHR and six patients (age range, 4-22 years) with BCM were studied. ERG responses to full-field stimuli were obtained in scotopic and photopic conditions. Rod photoreceptor (S(rod), R(rod)) and rod-driven postreceptor (log sigma, V(max)) response parameters were calculated from the a-wave and b-wave. ERG records were digitally filtered to demonstrate the oscillatory potentials (OPs); a sensitivity parameter, log SOPA(1/2), and an amplitude parameter, SOPA(max), were used to characterize the OP response. Response parameters were compared with those of 12 healthy control subjects.

RESULTS

As expected, photopic responses were nondetectable in patients with ACHR and BCM. In addition, mean scotopic photoreceptor (R(rod)) and postreceptor (V(max) and SOPA(max)) amplitude parameters were significantly reduced compared with those in healthy controls. The flash intensity required to evoke a half-maximum b-wave amplitude (log sigma) was significantly increased.

CONCLUSIONS

Results of this study provide evidence that deficits in rod and rod-mediated function occur in the primary cone dysfunction syndromes ACHR and BCM.

Multifocal ERG responses in infants

PURPOSE

To assess function of the central retina in 10-week-old infants, multifocal electroretinograms (mfERGs) were recorded. mfERG responses represent postreceptor retinal activity.

METHODS

In infants (n = 23) and adults (n = 10), mfERG responses to both unscaled and scaled 61 hexagon arrays were recorded. Amplitude and implicit time of negative (N(1), N(2)) and positive (P(1)) peaks of the first-order kernel were examined. The response from the entire area stimulated and responses to concentric rings were analyzed separately. The overall averaged response of the first slice of the second-order kernel was also evaluated. Results from infants and adults were compared.

RESULTS

Amplitudes of the infants' responses (N(1), P(1), N(2)) were significantly smaller and implicit times were significantly longer than those of adults. In infants, amplitude and implicit time varied little with eccentricity. In adults, amplitude decreased with eccentricity, whereas implicit time varied little. In infants, the second-order kernel was relatively more attenuated than the first-order kernel.

CONCLUSIONS

The infants' mfERG responses indicated immaturities of processing in the central retina. Infant-adult differences in the distribution of cones and bipolar cells may account for the results.

Retinal degenerative and hypoxic ischemic disease

A broad spectrum of retinal diseases affects both the retinal vasculature and the neural retina, including photoreceptor and postreceptor layers. The accepted clinical hallmarks of acute retinopathy of prematurity (ROP) are dilation and tortuosity of the retinal vasculature. Additionally, significant early and persistent effects on photoreceptor and postreceptor neural structures and function are demonstrated in ROP. In this paper, we focus on the results of longitudinal studies of electroretinographic (ERG) and vascular features in rats with induced retinopathies that model the gamut of human ROP, mild to severe. Two potential targets for pharmaceutical interventions emerge from the observations. The first target is immature photoreceptors because the status of the photoreceptors at an early age predicts later vascular outcome; this approach is appealing as it holds promise to prevent ROP. The second target is the interplay of the neural and vascular retinal networks, which develop cooperatively. Beneficial pharmaceutical interventions may be measured in improved visual outcome as well as lessening of the vascular abnormalities.

The cone electroretinogram in retinopathy of prematurity

PURPOSE

To test the hypothesis that retinopathy of prematurity (ROP) affects the cone photoreceptors less than the rod photoreceptors.

METHODS

Electroretinogram (ERG) responses to a 1.8-log-unit range of red flashes on a white, rod-saturating background were recorded in 42 subjects with a history of preterm birth and ROP (28 untreated; 6 treated) or no ROP (n = 8). The sensitivity (S(CONE)) and saturated amplitude (R(CONE)) of the cone photoresponse were calculated by fit of a model of the activation of cone phototransduction to the a-waves. The cone-driven b-wave amplitude was evaluated as a function of stimulus intensity. S(CONE) and R(CONE) were compared to the rod response parameters (S(ROD), R(ROD)) recorded from the same preterm subjects. Responses in the former preterm subjects were compared to those in control subjects.

RESULTS

The values of S(CONE) and R(CONE) in the preterm subjects overlapped broadly with those in the control subjects. The shapes of the b-wave stimulus-response functions did not differ between preterm and control subjects. The relative value of S(CONE) was significantly greater than that of S(ROD).

CONCLUSIONS

ROP has less effect on the cone than on the rod photoresponses, suggesting that cones are more resistant to the ROP disease process. The similar shape of the b-wave stimulus-response function in preterms and control subjects is evidence that ROP does not alter the balance of ON and OFF signals in the cone pathway.

The oscillatory potentials of the dark-adapted electroretinogram in retinopathy of prematurity

PURPOSE

To study the development of the electroretinographic (ERG) oscillatory potentials (OPs) in two rat models of ROP and in human subjects with a history of ROP.

METHODS

Sprague-Dawley rats (n = 36) were studied longitudinally. Rat models of ROP were induced, either by exposure to alternating 50%/10% oxygen (50/10 model) from postnatal day (P) 0 to P14 or by exposure to 75% oxygen (75 model) from P7 to P14. Control rats were reared in room air. Infant and adult human subjects with and without a history of ROP (n = 91) were also studied. Dark-adapted ERGs were recorded and filtered to demonstrate the OPs. Discreet Fourier transform (DFT) allowed evaluation of the OP power spectrum. OP energy (E), dominant frequency (F(peak)), and sensitivity (log i(1/2)) were evaluated.

RESULTS

In 50/10 model rats, E was low compared with that in the 75 model rats and control animals. F(peak) (approximately 95 Hz) did not vary with age or group. Intriguingly, log i(1/2) in 75 model rats was greater than that in controls or 50/10 model rats. Human adults with a history of ROP had lower-energy OPs than did the control adults, but infants with a history of ROP had higher-energy OPs than did the control infants. F(peak) was lower (approximately 120 Hz) in infants than in adults (approximately 130 Hz). ROP did not affect log i(1/2) in humans.

CONCLUSIONS

Differences between OPs in healthy rats and healthy humans were substantial, suggesting that OPs in rat models of ROP are unlikely to provide insight into the effects of ROP on human OPs. Indeed, neither ROP model studied showed a pattern of effects similar to that in human ROP.

Development of scotopic visual thresholds in retinopathy of prematurity

PURPOSE

To test the hypothesis that the late-maturing parafoveal rod photoreceptors are more vulnerable than peripheral rods to the effects of retinopathy of prematurity (ROP).

METHODS

Twenty-four infants with a history of preterm birth (gestational age at birth </=31 weeks) participated in a longitudinal study: 12 had mild ROP that resolved without treatment, and 12 had never had ROP. Thresholds for detecting stimuli (2 degrees diameter, 50 ms duration) presented 10 degrees (parafoveal) and 30 degrees (peripheral) from a central fixation target were estimated by using a preferential-looking

METHOD

At each visit, thresholds at both sites were obtained in random order. Thresholds of the preterm subjects were compared with those of previously reported term infants.

RESULTS

The course of threshold maturation in subjects with ROP was significantly prolonged (P </= 0.01) compared with those who had never had ROP and with term-born control subjects. On average, parafoveal thresholds in subjects with ROP reached the adult level at a median age of 12 (range, 6-18) months, and peripheral thresholds reached the adult level at 9 (range, 5-12) months. Median thresholds in subjects who had never had ROP reached adult levels at both sites by approximately 7 months.

CONCLUSIONS

The slower development of parafoveal compared with peripheral thresholds in subjects with a history of ROP is evidence that the late-maturing parafoveal rods are more affected by the ROP disease process.

Development of the electroretinographic oscillatory potentials in normal and ROP rats

PURPOSE

To study the development of the electroretinographic (ERG) oscillatory potentials (OPs) in rats and to compare normal OPs with those in a rat model of retinopathy of prematurity (ROP).

METHODS

Following a longitudinal design, ERG responses to a greater than 5 log unit range of full-field stimuli were recorded in dark-adapted rats at postnatal day (P) 18, P31, P47, and P67. The ERG records were digitally filtered (60-235 Hz), and the trough-to-peak amplitudes and implicit times of OP2, OP3, OP4, and OP5 were measured. Additionally, rats with oxygen-induced retinopathy, a model of ROP, were studied at P31.

RESULTS

Generally, OP amplitude increased and implicit time decreased with increasing stimulus intensity. The shape of the stimulus-response functions changed with age. The amplitudes of OP2, OP3, and OP4 were largest at P31. OP5 was largest at P47. All OPs were significantly affected in ROP rats; OP5 was least affected by ROP.

CONCLUSIONS

A prolonged normal course of OP development, which featured waxing and waning of amplitudes, was observed and might have been consequent to maturation and then to final refinements of inner retinal circuitry. In ROP rats, marked attenuation of early OPs was consistent with persistent dysfunction of photoreceptors, and significant attenuation of the late OP5 was evidence of compromised function of inner retinal circuitry.

Pediatric clinical visual electrophysiology: a survey of actual practice

PURPOSE

Survey the actual clinical practice of pediatric visual electrophysiology. The electrophysiologists surveyed were members of the International Society for Clinical Electrophysiology of Vision (ISCEV).

METHODS

A self-administered questionnaire with 55 items about visual evoked potential (VEP) and electroretinogram (ERG) testing of pediatric patients was sent to ISCEV members. The survey queried personnel, facilities, referral patterns and conduct of tests.

RESULTS

Nearly all respondents (94%) had advanced scientific or clinical degrees or both, and most (96%) worked in academic or medical facilities. Of the 71 respondents, 68 tested patients 12 years or younger, and nearly all of those performed both VEPs and ERGs. However, fewer than a third did high volume (>10/month) testing of infants and young children (< or =6 years). Eye care professionals and neurologists made the majority (57%) of the referrals, with the most common reason for referral being suspected visual impairment. Conduct of a pediatric test session often required more than one practitioner. For both VEP and ERG, more than 70% of respondents required at least 30 min for each test. The majority indicated that they followed the ISCEV standards for stimuli and data acquisition. Almost all (94%) reported using the ISCEV recommended VEP electrode configuration. For ERG, most (88%) used ocular contact electrodes (including contact lens, thread, foil and HK loop), but 12% used skin electrodes exclusively and some (17%) used skin electrodes at times.

CONCLUSIONS

Pediatric ERG and VEP testing is a labor intensive endeavor of highly trained professionals. ISCEV technical standards are typically met or exceeded, indicating that high quality testing of infants and children is feasible. Revision of the ISCEV ERG standard is necessary to bring actual practice into accord with evidence-based recommendations for infant testing.