Precursors to infant sensorimotor synchronization to speech and non-speech rhythms: A longitudinal study

Impaired sensorimotor synchronization (SMS) to acoustic rhythm may be a marker of atypical language development. Here, Motion Capture was used to assess gross motor rhythmic movement at six time points between 5- and 11 months of age. Infants were recorded drumming to acoustic stimuli of varying linguistic and temporal complexity: drumbeats, repeated syllables and nursery rhymes. Here we show, for the first time, developmental change in infants' movement timing in response to auditory stimuli over the first year of life. Longitudinal analyses revealed that whilst infants could not yet reliably synchronize their movement to auditory rhythms, infant spontaneous motor tempo became faster with age, and by 11 months, a subset of infants decelerate from their spontaneous motor tempo, which better accords with the incoming tempo. Further, infants became more regular drummers with age, with marked decreases in the variability of spontaneous motor tempo and variability in response to drumbeats. This latter effect was subdued in response to linguistic stimuli. The current work lays the foundation for using individual differences in precursors of SMS in infancy to predict later language outcomes. RESEARCH HIGHLIGHT: We present the first longitudinal investigation of infant rhythmic movement over the first year of life Whilst infants generally move more quickly and with higher regularity over their first year, by 11 months infants begin to counter this pattern when hearing slower infant-directed song Infant movement is more variable to speech than non-speech stimuli In the context of the larger Cambridge UK BabyRhythm Project, we lay the foundation for rhythmic movement in infancy to predict later language outcomes.

Decoding speech information from EEG data with 4-, 7- and 11-month-old infants: Using convolutional neural network, mutual information-based and backward linear models

BACKGROUND

Computational models that successfully decode neural activity into speech are increasing in the adult literature, with convolutional neural networks (CNNs), backward linear models, and mutual information (MI) models all being applied to neural data in relation to speech input. This is not the case in the infant literature.

NEW METHOD

Three different computational models, two novel for infants, were applied to decode low-frequency speech envelope information. Previously-employed backward linear models were compared to novel CNN and MI-based models. Fifty infants provided EEG recordings when aged 4, 7, and 11 months, while listening passively to natural speech (sung or chanted nursery rhymes) presented by video with a female singer.

RESULTS

Each model computed speech information for these nursery rhymes in two different low-frequency bands, delta and theta, thought to provide different types of linguistic information. All three models demonstrated significant levels of performance for delta-band neural activity from 4 months of age, with two of three models also showing significant performance for theta-band activity. All models also demonstrated higher accuracy for the delta-band neural responses. None of the models showed developmental (age-related) effects.

COMPARISONS WITH EXISTING METHODS

The data demonstrate that the choice of algorithm used to decode speech envelope information from neural activity in the infant brain determines the developmental conclusions that can be drawn.

CONCLUSIONS

The modelling shows that better understanding of the strengths and weaknesses of each modelling approach is fundamental to improving our understanding of how the human brain builds a language system.

Emergence of the cortical encoding of phonetic features in the first year of life

Even prior to producing their first words, infants are developing a sophisticated speech processing system, with robust word recognition present by 4-6 months of age. These emergent linguistic skills, observed with behavioural investigations, are likely to rely on increasingly sophisticated neural underpinnings. The infant brain is known to robustly track the speech envelope, however previous cortical tracking studies were unable to demonstrate the presence of phonetic feature encoding. Here we utilise temporal response functions computed from electrophysiological responses to nursery rhymes to investigate the cortical encoding of phonetic features in a longitudinal cohort of infants when aged 4, 7 and 11 months, as well as adults. The analyses reveal an increasingly detailed and acoustically invariant phonetic encoding emerging over the first year of life, providing neurophysiological evidence that the pre-verbal human cortex learns phonetic categories. By contrast, we found no credible evidence for age-related increases in cortical tracking of the acoustic spectrogram.

Neural phase angle from two months when tracking speech and non-speech rhythm linked to language performance from 12 to 24 months

Atypical phase alignment of low-frequency neural oscillations to speech rhythm has been implicated in phonological deficits in developmental dyslexia. Atypical phase alignment to rhythm could thus also characterize infants at risk for later language difficulties. Here, we investigate phase-language mechanisms in a neurotypical infant sample. 122 two-, six- and nine-month-old infants were played speech and non-speech rhythms while EEG was recorded in a longitudinal design. The phase of infants' neural oscillations aligned consistently to the stimuli, with group-level convergence towards a common phase. Individual low-frequency phase alignment related to subsequent measures of language acquisition up to 24 months of age. Accordingly, individual differences in language acquisition are related to the phase alignment of cortical tracking of auditory and audiovisual rhythms in infancy, an automatic neural mechanism. Automatic rhythmic phase-language mechanisms could eventually serve as biomarkers, identifying at-risk infants and enabling intervention at the earliest stages of development.

Cortical Tracking of Sung Speech in Adults vs Infants: A Developmental Analysis

Here we duplicate a neural tracking paradigm, previously published with infants (aged 4 to 11 months), with adult participants, in order to explore potential developmental similarities and differences in entrainment. Adults listened and watched passively as nursery rhymes were sung or chanted in infant-directed speech. Whole-head EEG (128 channels) was recorded, and cortical tracking of the sung speech in the delta (0.5–4 Hz), theta (4–8 Hz) and alpha (8–12 Hz) frequency bands was computed using linear decoders (multivariate Temporal Response Function models, mTRFs). Phase-amplitude coupling (PAC) was also computed to assess whether delta and theta phases temporally organize higher-frequency amplitudes for adults in the same pattern as found in the infant brain. Similar to previous infant participants, the adults showed significant cortical tracking of the sung speech in both delta and theta bands. However, the frequencies associated with peaks in stimulus-induced spectral power (PSD) in the two populations were different. PAC was also different in the adults compared to the infants. PAC was stronger for theta- versus delta- driven coupling in adults but was equal for delta- versus theta-driven coupling in infants. Adults also showed a stimulus-induced increase in low alpha power that was absent in infants. This may suggest adult recruitment of other cognitive processes, possibly related to comprehension or attention. The comparative data suggest that while infant and adult brains utilize essentially the same cortical mechanisms to track linguistic input, the operation of and interplay between these mechanisms may change with age and language experience.

Neural detection of changes in amplitude rise time in infancy

Amplitude rise times play a crucial role in the perception of rhythm in speech, and reduced perceptual sensitivity to differences in rise time is related to developmental language difficulties. Amplitude rise times also play a mechanistic role in neural entrainment to the speech amplitude envelope. Using an ERP paradigm, here we examined for the first time whether infants at the ages of seven and eleven months exhibit an auditory mismatch response to changes in the rise times of simple repeating auditory stimuli. We found that infants exhibited a mismatch response (MMR) to all of the oddball rise times used for the study. The MMR was more positive at seven than eleven months of age. At eleven months, there was a shift to a mismatch negativity (MMN) that was more pronounced over left fronto-central electrodes. The MMR over right fronto-central electrodes was sensitive to the size of the difference in rise time. The results indicate that neural processing of changes in rise time is present at seven months, supporting the possibility that early speech processing is facilitated by neural sensitivity to these important acoustic cues.

Delta- and theta-band cortical tracking and phase-amplitude coupling to sung speech by infants

The amplitude envelope of speech carries crucial low-frequency acoustic information that assists linguistic decoding at multiple time scales. Neurophysiological signals are known to track the amplitude envelope of adult-directed speech (ADS), particularly in the theta-band. Acoustic analysis of infant-directed speech (IDS) has revealed significantly greater modulation energy than ADS in an amplitude-modulation (AM) band centred on ∼2 Hz. Accordingly, cortical tracking of IDS by delta-band neural signals may be key to language acquisition. Speech also contains acoustic information within its higher-frequency bands (beta, gamma). Adult EEG and MEG studies reveal an oscillatory hierarchy, whereby low-frequency (delta, theta) neural phase dynamics temporally organize the amplitude of high-frequency signals (phase amplitude coupling, PAC). Whilst consensus is growing around the role of PAC in the matured adult brain, its role in the development of speech processing is unexplored. Here, we examined the presence and maturation of low-frequency (<12 Hz) cortical speech tracking in infants by recording EEG longitudinally from 60 participants when aged 4-, 7- and 11- months as they listened to nursery rhymes. After establishing stimulus-related neural signals in delta and theta, cortical tracking at each age was assessed in the delta, theta and alpha [control] bands using a multivariate temporal response function (mTRF) method. Delta-beta, delta-gamma, theta-beta and theta-gamma phase-amplitude coupling (PAC) was also assessed. Significant delta and theta but not alpha tracking was found. Significant PAC was present at all ages, with both delta and theta -driven coupling observed.

The Acquisition of Noun and Verb Categories by Bootstrapping From a Few Known Words: A Computational Model

While many studies have shown that toddlers are able to detect syntactic regularities in speech, the learning mechanism allowing them to do this is still largely unclear. In this article, we use computational modeling to assess the plausibility of a context-based learning mechanism for the acquisition of nouns and verbs. We hypothesize that infants can assign basic semantic features, such as “is-an-object” and/or “is-an-action,” to the very first words they learn, then use these words, the semantic seed, to ground proto-categories of nouns and verbs. The contexts in which these words occur, would then be exploited to bootstrap the noun and verb categories: unknown words are attributed to the class that has been observed most frequently in the corresponding context. To test our hypothesis, we designed a series of computational experiments which used French corpora of child-directed speech and different sizes of semantic seed. We partitioned these corpora in training and test sets: the model extracted the two-word contexts of the seed from the training sets, then used them to predict the syntactic category of content words from the test sets. This very simple algorithm demonstrated to be highly efficient in a categorization task: even the smallest semantic seed (only 8 nouns and 1 verb known) yields a very high precision (~90% of new nouns; ~80% of new verbs). Recall, in contrast, was low for small seeds, and increased with the seed size. Interestingly, we observed that the contexts used most often by the model featured function words, which is in line with what we know about infants' language development. Crucially, for the learning method we evaluated here, all initialization hypotheses are plausible and fit the developmental literature (semantic seed and ability to analyse contexts). While this experiment cannot prove that this learning mechanism is indeed used by infants, it demonstrates the feasibility of a realistic learning hypothesis, by using an algorithm that relies on very little computational and memory resources. Altogether, this supports the idea that a probabilistic, context-based mechanism can be very efficient for the acquisition of syntactic categories in infants.

Machine learning accurately classifies neural responses to rhythmic speech vs. non-speech from 8-week-old infant EEG

Currently there are no reliable means of identifying infants at-risk for later language disorders. Infant neural responses to rhythmic stimuli may offer a solution, as neural tracking of rhythm is atypical in children with developmental language disorders. However, infant brain recordings are noisy. As a first step to developing accurate neural biomarkers, we investigate whether infant brain responses to rhythmic stimuli can be classified reliably using EEG from 95 eight-week-old infants listening to natural stimuli (repeated syllables or drumbeats). Both Convolutional Neural Network (CNN) and Support Vector Machine (SVM) approaches were employed. Applied to one infant at a time, the CNN discriminated syllables from drumbeats with a mean AUC of 0.87, against two levels of noise. The SVM classified with AUC 0.95 and 0.86 respectively, showing reduced performance as noise increased. Our proof-of-concept modelling opens the way to the development of clinical biomarkers for language disorders related to rhythmic entrainment.

Newborns are sensitive to multiple cues for word segmentation in continuous speech

Before infants can learn words, they must identify those words in continuous speech. Yet, the speech signal lacks obvious boundary markers, which poses a potential problem for language acquisition (Swingley, Philos Trans R Soc Lond. Series B, Biol Sci 364(1536), 3617-3632, 2009). By the middle of the first year, infants seem to have solved this problem (Bergelson & Swingley, Proc Natl Acad Sci 109(9), 3253-3258, 2012; Jusczyk & Aslin, Cogn Psychol 29, 1-23, 1995), but it is unknown if segmentation abilities are present from birth, or if they only emerge after sufficient language exposure and/or brain maturation. Here, in two independent experiments, we looked at two cues known to be crucial for the segmentation of human speech: the computation of statistical co-occurrences between syllables and the use of the language's prosody. After a brief familiarization of about 3 min with continuous speech, using functional near-infrared spectroscopy, neonates showed differential brain responses on a recognition test to words that violated either the statistical (Experiment 1) or prosodic (Experiment 2) boundaries of the familiarization, compared to words that conformed to those boundaries. Importantly, word recognition in Experiment 2 occurred even in the absence of prosodic information at test, meaning that newborns encoded the phonological content independently of its prosody. These data indicate that humans are born with operational language processing and memory capacities and can use at least two types of cues to segment otherwise continuous speech, a key first step in language acquisition.

Clinical use of a New Method for Visual Field Damage Classification in Glaucoma

This new method, based on the use of MD and CPSD (or CLV) visual field indices, can instantly classify not only the stage of glaucomatous visual field damage, but also the type of defect (localized, generalized or mixed). This system was used to study glaucomatous visual field defects in 500 automated tests, performed with either Humphrey 30-2 or Octopus G1 threshold tests. The most common defects found were mixed, and purely local defects were very unusual, especially in advanced glaucoma.

Ocular Hypertension and Corneal Thickness: A Long-Term Prospective Study. Results after Two Years

Purpose

To study the importance of the central corneal thickness (CCT) in patients with ocular hypertension in a 2-year follow-up.

Methods

A total of 110 subjects with ocular hypertension (intraocular pressure [IOP] >21 mmHg and normal automated visual field test) were admitted to the study. All patients periodically underwent the following tests: 1) circadian IOP curve; 2) standard automated perimetry (SAP, Humphrey 30–2 SITA test); 3) short wavelength automated perimetry (SWAP); 4) frequency doubling technology perimetry (FDT, N-30 threshold test); 5) nerve fiber layer analysis with GDx; 6) ibopamine test; 7) ultrasonic pachymetry. Patients were divided into three groups, based on corneal thickness. The frequency of abnormal tests within these groups was evaluated with the Pearson's χ2 test. Baseline IOP was corrected using the Doughty and Zaman formula. CCT was also considered as a continuous variable. A control group of 48 normal subjects was also considered.

Results

The mean CCT was 562.8 um ± 37.7. The difference with respect to normal subjects was statistically significant (p<0.01). Using the correction formula, 43 eyes (39.1%) had an IOP <21 mmHg. Abnormal test results were more frequently found with FDT. The percentage of abnormal results was found to be inversely proportional to CCT. The other tests gave inconsistent or conflicting results. Using the values of CCT as a continuous variable, no significant association was found with the GDx number and the visual field indices.

Conclusions

The results of our 2-year study confirm the importance of CCT measurement in the evaluation of the risk of developing glaucomatous damage.

Scleroretinal Necrosis after a Subconjunctival Injection of Gentamicin in a Patient with a Surgically Repaired Episcleral Retinal Detachment

PURPOSE

To describe a case of scleroretinal necrosis after a subconjunctival injection of gentamicin in a patient who had an episcleral retinal detachment that was surgically repaired.

METHODS

Case presentation.

RESULTS

Thinning of the sclera due to cryosurgery and the induced localized inflammatory response resulting from the surgical procedure, in addition to the effect of the sponge buckle itself, could have played an important role in accumulation and storage of gentamicin under and adjacent to the buckle after injection. The increasingly higher concentration of the drug under the buckle could have induced a greater penetration of gentamicin through the sclera, which could have been the cause of the scleral-chorio-retinal necrosis observed in this patient.

CONCLUSIONS

Attention must be given to avoid side effects from subconjunctival injection of gentamicin.

A novel form of perceptual attunement: Context-dependent perception of a native contrast in 14-month-old infants

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A novel form of infants’ perceptual attunement to a native contrast is shown.

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An original Type I error-free EEG Mismatch paradigm is used in 14-month-olds.

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Like adults, infants do not detect a native voicing contrast in specific contexts.

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Infants’ perceptual attunement to their native language is context-dependent.

By the end of their first year of life, infants have become experts in discriminating the sounds of their native language, while they have lost the ability to discriminate non-native contrasts. This type of phonetic learning is referred to as perceptual attunement. In the present study, we investigated the emergence of a context-dependent form of perceptual attunement in infancy. Indeed, some native contrasts are not discriminated in certain phonological contexts by adults, due to the presence of a language-specific process that neutralizes the contrasts in those contexts. We used a mismatch design and recorded high-density Electroencephalography (EEG) in French-learning 14-month-olds. Our results show that similarly to French adults, infants fail to discriminate a native voicing contrast (e.g., [f] vs. [v]) when it occurs in a specific phonological context (e.g. [ofbe] vs. [ovbe], no mismatch response), while they successfully detected it in other phonological contexts (e.g., [ofne] vs. [ovne], mismatch response). The present results demonstrate for the first time that by the age of 14 months, infants’ phonetic learning does not only rely on the processing of individual sounds, but also takes into account in a language-specific manner the phonological contexts in which these sounds occur.

ERP evidence for on-line syntactic computations in 2-year-olds

Syntax allows human beings to build an infinite number of sentences from a finite number of words. How this unique, productive power of human language unfolds over the course of language development is still hotly debated. When they listen to sentences comprising newly-learned words, do children generalize from their knowledge of the legal combinations of word categories or do they instead rely on strings of words stored in memory to detect syntactic errors? Using novel words taught in the lab, we recorded Evoked Response Potentials (ERPs) in two-year-olds and adults listening to grammatical and ungrammatical sentences containing syntactic contexts that had not been used during training. In toddlers, the ungrammatical use of words, even when they have been just learned, induced an early left anterior negativity (surfacing 100-400ms after target word onset) followed by a late posterior positivity (surfacing 700-900ms after target word onset) that was not observed in grammatical sentences. This late effect was remarkably similar to the P600 displayed by adults, suggesting that toddlers and adults perform similar syntactic computations. Our results thus show that toddlers build on-line expectations regarding the syntactic category of upcoming words in a sentence.

Baseline factors predicting the risk of conversion from ocular hypertension to primary open-angle glaucoma during a 10-year follow-up

PurposeTo evaluate the ability of baseline clinical, morphological, and functional factors to predict the conversion to primary open-angle glaucoma (POAG) in ocular hypertensive (OHT) patients.MethodsThis single-center prospective longitudinal observational study included 116 eyes of 116 OHT patients followed for a 10-year period. All patients had intraocular pressure (IOP) ≥24 mm Hg in one eye and >21 mm Hg in the other eye, normal visual fields (VFs) and normal optic disc (OD) appearance in both eyes at baseline. All OHT patients were untreated at baseline with subsequent treatment upon need according to clinical judgement. Only one eye per subject was randomly selected. Patient age, gender, IOP, central corneal thickness (CCT), and ibopamine test results were collected at baseline. All patients underwent standard automated perimetry, short-wavelength automated perimetry (SWAP), frequency-doubling technology, confocal scanning laser ophthalmoscopy (CSLO), and scanning laser polarimetry (SLP) at baseline and every 6 months thereafter. Main outcome measure was the conversion to POAG, defined as the development of reproducible VF and/or OD abnormalities attributable to glaucoma. Cox proportional hazards models were used to identify the baseline factors predictive of POAG conversion.ResultsDuring the 10-year follow-up, 25% of eyes converted to POAG. In multivariate Cox models, baseline factors that were significant predictors of POAG development included: older age (hazard ratio (HR) 1.0, 99% confidence intervals (CIs) 1.0-1.2, per 1 year older); SWAP Glaucoma Hemifield test 'outside normal limits' (HR 4.3, 99% CIs 1.2-17.9); greater SLP 'Inter-eye Symmetry' (HR 1.1, 99% CIs 0.4-3.0, per 1 unit lower); lower CSLO Rim Volume (HR 1.1, 99% CIs 0.3-3.2, per 0.1 mm(3) lower); and greater CSLO cup-to-disc ratio (HR 6.0, 99% CIs 3.6-16.8, per 0.1 unit greater).ConclusionsThe baseline parameters that proved to be useful in assessing the likelihood of an OHT patient to develop POAG included age, functional variables provided by SWAP, and structural variables provided by SLP and CSLO. In this cohort of patients, baseline IOP, CCT, and ibopamine provocative test results were not significant predictors of POAG conversion.

Listeners Exploit Syntactic Structure On-Line to Restrict Their Lexical Search to a Subclass of Verbs

Many experiments have shown that listeners actively build expectations about up-coming words, rather than simply waiting for information to accumulate. The online construction of a syntactic structure is one of the cues that listeners may use to construct strong expectations about the possible words they will be exposed to. For example, speakers of verb-final languages use pre-verbal arguments to predict on-line the kind of arguments that are likely to occur next (e.g., Kamide, 2008, for a review). Although in SVO languages information about a verb's arguments typically follows the verb, some languages use pre-verbal object pronouns, potentially allowing listeners to build on-line expectations about the nature of the upcoming verb. For instance, if a pre-verbal direct object pronoun is heard, then the following verb has to be able to enter a transitive structure, thus excluding intransitive verbs. To test this, we used French, in which object pronouns have to appear pre-verbally, to investigate whether listeners use this cue to predict the occurrence of a transitive verb. In a word detection task, we measured the number of false alarms to sentences that contained a transitive verb whose first syllable was homophonous to the target monosyllabic verb (e.g., target “dort” /dɔʁ/ to sleep and false alarm verb “dorlote” /dɔʁlɔt/ to cuddle). The crucial comparison involved two sentence types, one without a pre-verbal object clitic, for which an intransitive verb was temporarily a plausible option (e.g., “Il dorlote” / He cuddles) and the other with a pre-verbal object clitic, that made the appearance of an intransitive verb impossible (“Il le dorlote” / He cuddles it). Results showed a lower rate of false alarms for sentences with a pre-verbal object pronoun (3%) compared to locally ambiguous sentences (about 20%). Participants rapidly incorporate information about a verb's argument structure to constrain lexical access to verbs that match the expected subcategorization frame.

Toddlers default to canonical surface-to-meaning mapping when learning verbs

Previous work has shown that toddlers readily encode each noun in the sentence as a distinct argument of the verb. However, languages allow multiple mappings between form and meaning that do not fit this canonical format. Two experiments examined French 28-month-olds' interpretation of right-dislocated sentences (nouni -verb, nouni) where the presence of clear, language-specific cues should block such a canonical mapping. Toddlers (N = 96) interpreted novel verbs embedded in these sentences as transitive, disregarding prosodic cues to dislocation (Experiment 1) but correctly interpreted right-dislocated sentences containing well-known verbs (Experiment 2). These results suggest that toddlers can integrate multiple cues in ideal conditions, but default to canonical surface-to-meaning mapping when extracting structural information about novel verbs in semantically impoverished conditions.

Comparison of iCare tonometer and Goldmann applanation tonometry in normal corneas and in eyes with automated lamellar and penetrating keratoplasty

PURPOSE

To compare intraocular pressure (IOP) measurements with Goldmann applanation tonometry (GAT) and iCare tonometry in normal and post-keratoplasty corneas and to assess the influence of central corneal thickness (CCT), corneal curvature (CC), and corneal astigmatism (CA) on IOP.

METHODS

This prospective cross-sectional study included one eye of 101 subjects with normal corneas (58 healthy subjects, 43 glaucoma); and 90 post-keratoplasty patients: 34 penetrating keratoplasties (PK); 20 automated-lamellar-therapeutic keratoplasties (ALTK); 19 Descemet-stripping-automated-endothelial keratoplasties (DSAEK); 17 edematous grafts. All subjects underwent GAT and iCare IOP measurements in random order, and CCT, CC, and CA evaluation. The Bland-Altman method and multivariate regression analysis were used to assess inter-tonometer agreement and the influence of CCT, CC, and CA on IOP.

RESULTS

iCare significantly underestimated IOP in all groups compared with GAT (GAT minus iCare of 3.5±3.5 mm Hg, P<0.001), but overestimated IOP in the edematous grafts (GAT minus iCare of -6.5±1.9 mm Hg, P<0.001). In normal corneas, both tonometer measurements were directly related to CCT values; iCare readings appeared inversely related to CC. There was no significant relationship between IOP and CCT, CC and CA in post-keratoplasty eyes, except between CC and iCare measurements for PK eyes.

CONCLUSIONS

The agreement between GAT and iCare was clinically acceptable in control, ALTK and DSAEK groups, and poor in PK and edematous grafts eyes. In normal corneas, GAT was significantly affected by CCT; iCare was influenced by CCT and CC. The iCare appeared less influenced by corneal edema when compared with GAT. High IOP readings taken with both tonometers in grafts should raise suspicion of true elevated IOP.

Pupil size influence on the intraocular performance of the multifocal AMO-Array intraocular lens in elderly patients

PURPOSE

To study the relationship between pupil size and AMO-Array multifocal intraocular lens (MIOL) performance in a population of elderly patients.

METHODS

This prospective trial included 62 patients (mean age 76 years; range 70 to 86) undergoing bilateral cataract phacoemulsification and MIOL (AMO-Array SA-40N, Allergan) implantation. Patients were divided into two groups based on preoperative pupil diameter: small pupil group (pupil size of 2.5-2.9 mm; 45 subjects) and large pupil group (pupil size of 3-5 mm; 17 subjects). The analysis included uncorrected (UC) and best-corrected (BC) near and distance visual acuity (VA), spectacle dependence, and photic phenomena complaints (postoperative follow-up 16.6+/-6.2 months; range 11-26 months).

RESULTS

Patients in the small pupil group showed postoperatively significantly higher distance UCVA and BCVA, but lower near UCVA compared to those in the large pupil group (Mann-Whitney test, p< or = 0.02). Patients with small pupils also tended to: be more (not statistically significant) spectacle independent for distance (73.3% versus 47.1%) and spectacle-dependent for near vision (55.6% versus 28.4%); report significantly less photic phenomena complaints (37.8% versus 93.1%, chisquare test, p<0.001); and, more satisfied with the surgery (95.5% versus 76.5%). Posterior capsular opacification (PCO) was observed in 19.4% of the patients.

CONCLUSIONS

Bilateral AMO-Array MIOL implantation in elderly patients seems to be an effective and safe surgical procedure that improves distance and near UCVA, providing spectacle independence in many cases. The use of these MIOLs, however, can induce photic phenomena and cause PCO. Patients with small preoperative pupils (<3 mm) presented less photic phenomena complaints and expressed a higher visual outcome satisfaction after surgery.

Stratus-OCT imaging in early glaucomatous and in ocular hypertensive patients with and without frequency-doubling technology abnormalities

AIM

To compare Stratus-OCT measurements in controls, ocular hypertensive (OHT) patients with (FDT+) and without (FDT-) frequency-doubling technology (FDT) abnormalities, and in patients affected with early primary open-angle glaucoma (POAG).

METHODS

Thirty-two controls, 78 OHT patients (38 FDT- and 40 FDT+), and 45 early POAG patients (six FDT- and 39 FDT+) underwent the following tests within 3 months: standard automated perimetry (SAP) HFA 30-2; FDT N-30-F; and, Stratus-OCT imaging with retinal nerve fibre layer (RNFL) and optic nerve head (ONH) scans. One eye per patient was considered. Differences among groups were evaluated using the Kruskal-Wallis, analysis of variance, and Duncan's tests.

RESULTS

There were no significant differences in all Stratus-OCT parameters between POAG and OHT FDT+ patients. Statistically significant differences were found between the control group and both the POAG and OHT FDT+ groups for 15 of the 21 Stratus-OCT parameters. Control eyes compared to OHT FDT- showed significant differences in 13 of the 21 parameters. The comparison between the OHT FDT- group, and both the POAG and OHT FDT+ group resulted in 13 of the 21 parameters to be significantly different.

CONCLUSIONS

Stratus-OCT seems to show a higher ability in detecting significant differences between healthy, OHT, and early POAG eyes when compared to SAP and FDT. This suggests that the Stratus-OCT could show structural abnormalities before SAP or FDT visual field defects appear in patients at risk of developing glaucoma, which may be beneficial in making therapeutic decisions, especially in OHT patients.

Expression of haematopoietic stem cell markers, CD133 and CD34 on human corneal keratocytes

AIM

To study the expression of CD133 and CD34 antigens on cultured human keratocytes over time.

METHODS

Primary cultures of human corneal stromal cells were established from explants derived from cadaver eye donors. The cultures were sorted for CD133+ and CD34+ cells using magnetic beads. Both the primary cultures and secondary passages of sorted cells were further analysed by flow cytometry and western blot analysis for expression of the same antigens over time.

RESULTS

Four different cell populations-namely, CD133+, CD133-, CD34+ and CD34-, were identified in the culture samples. Two further specific subgroups were identified by flow cytometry: CD133+/CD34- cells and CD133+/CD34+ cells. Expression of CD133 declines more than CD34 with time in cell cultures. Although most cells lost expression of these markers, small populations retained staining up to 5 weeks in culture.

CONCLUSION

Human keratocytes express the haematopoietic stem cell markers CD133 and CD34. This expression decreases with time in culture, with most but not all cells losing expression. On the basis of these markers, the corneal stroma shows a heterogeneous population of cells. Expression or down regulation of expression of these molecules could represent different stages of activation of these cells.

Discrimination between normal and early glaucomatous eyes with scanning laser polarimeter with fixed and variable corneal compensator settings

PURPOSE

To evaluate the ability of scanning laser polarimetry (SLP) with a fixed corneal polarization compensator (GDx-FCC Nerve Fiber Analyzer) compared to one with a variable one (GDx-VCC) in the discrimination between healthy and early glaucomatous eyes.

METHODS

Forty patients with early glaucomatous visual field defects, having a mean deviation of 3.1-/+1.6 dB and a pattern standard deviation of 3.1-/+0.9 dB, and 40 controls underwent both GDx-FCC and GDx-VCC. One eye per patient was considered. The cut-off point, taken as the value dividing healthy from glaucomatous eyes with highest probability, was determined for each GDx parameter. Linear discriminant functions (LDFs) were separately developed for GDx-FCC and GDx-VCC parameters. Sensitivity, specificity, and area under the receiver operating characteristic curve (AROC) for discriminating between healthy and glaucomatous eyes were calculated for each GDx parameter, both according to the GDx normative database and after the selection of new cut-off points, and for the LDFs.

RESULTS

All software-provided parameters showed low sensitivity and high specificity. The selection of new cut-off points improved the performance of all GDx parameters: VCC parameters performed better than FCC parameters; the largest AROCs were associated with the superior/nasal ratio for the GDx-FCC (0.86) and with the Number for the GDx-VCC (0.87). The LDFs provided an AROC of 0.89 with both the GDx-FCC and the GDx-VCC parameters.

CONCLUSIONS

The GDx-VCC showed a higher ability in the early diagnosis of glaucoma when compared with the GDx-FCC. The individuation of the right cut-off point of selected parameters with both GDx settings performed better than the software-provided parameters, and comparably to the GDx parameters-based LDFs.

Corneal thickness and functional damage in patients with ocular hypertension

PURPOSE

To correlate functional damage over time detected by standard automated perimetry (SAP) and frequency doubling technology (FDT) with central corneal thickness (CCT) in patients with ocular hypertension (OHT).

METHODS

Seventy-eight OHT patients underwent CCT measurements, SAP, and FDT (the latter two also after 12 and 18 months). Patients were divided into three equally sized groups of 26 patients each: thin (< 540 microm), normal (540-580 microm), and thick cornea (> 580 microm). The frequency of abnormal FDT and SAP results was analyzed over time (Pearson chi2 test).

RESULTS

Six of 26 patients with thin corneas (23.1%) presented an abnormal FDT test at baseline, compared to 1 of 26 (3.8%) in the normal thickness cornea group and 1 of 26 (3.8%) in the thick cornea group. After 12 months, the abnormal FDT tests were as follows, respectively: 9 of 26 (34.6%), 2 of 26 (7.7%), and 2 of 26 (7.7%). For SAP the abnormal results were as follows, respectively: 8 (30.1%), 5 (19.2%), and 2 (7.7%). After 18 months, the abnormal FDT tests were as follows, respectively: 16 (61.5%), 5 (19.2%), and 5 (19.2%). For SAP, the abnormal results were as follows, respectively: 10 (38.5%), 5 (19.2%), and 2 (7.7%).

CONCLUSIONS

OHT patients with thinner corneas have a greater risk of developing functional damage over time.

Probing glaucoma visual damage by rarebit perimetry

AIM

To compare rarebit perimetry (RBP) with standard achromatic perimetry (SAP) in detecting early glaucomatous functional damage.

METHODS

43 patients with ocular hypertension (OH), 39 with early primary open angle glaucoma (POAG), and 41 controls were considered. Visual fields were assessed using the Humphrey field analyser (HFA) 30-2 and RBP tests. Differences among the groups were evaluated using Student-Newman-Keuls and chi(2) tests. Correlation between HFA and RBP parameters was assessed using the Pearson's correlation coefficients and regression analysis. Sensitivity and specificity of RBP in detecting early glaucomatous visual damage were calculated with different algorithms.

RESULTS

RBP-mean hit rate (MHR) was respectively 88.6% (SD 4.8%) in controls; 79.1% (10.9%) in the OH group; 64.3% (13.8%) in the POAG group (differences statistically significant). Good correlation in the POAG group was found between HFA-mean deviation and RBP-MHR. Largest AROC (0.95) and optimal sensitivity (97.4%) were obtained when an abnormal RBP test was defined as having (at least 1): MHR <80%; >15 areas with a non-hit rate of >10%; > or =2 areas with a non-hit rate of >50%; at least one area with a non-hit rate of > or =70%.

CONCLUSIONS

The RBP appeared to be a rapid, comfortable, and easily available perimetric test (requiring only a PC device), showing a high sensitivity and specificity in detecting early glaucomatous visual field defects.

Quantitative mapping of the retinal thickness at the posterior pole in chronic open angle glaucoma

The sensitivity of a new device, which is able to measure the thickness of the retina at the posterior pole (Retinal Thickness Analyzer), was assessed in a group of 21 glaucomatous patients, and in 24 patients with ocular hypertension. The specificity of RTA was evaluated in a control group of normal eyes. Of the glaucomatous eyes, 57.6% had a significant reduction in retinal thickness, while another 30.3% were borderline. In the ocular hypertension group, 37.5% of eyes were abnormal, and 45.8% were borderline. In the control group, no eye was abnormal, though 42.9% had borderline alterations. In many glaucomatous eyes (81.8%) there was a relationship between retinal thickness loss and visual field defects.

Corneal thickness in glaucoma: an important parameter?

Central corneal thickness was measured by pachometry in 49 patients with primary open-angle glaucoma (POAG), 41 with ocular hypertension (OHT), 14 with normal tension glaucoma (NTG) and 48 normal subjects. The mean corneal thickness of the OHT patients was significantly greater than that of the normal control group. The NTG patients, on the other hand, had a cornea on average thinner than the normals. These differences may cause misclassification of normals with a thick cornea as ocular hypertensive eyes or, contrarywise, cause those normals whose IOP is underestimated because of a thin cornea to be classed as NTG patients.

Frequency doubling perimetry in glaucoma early diagnosis

Frequency-doubling perimetry (FDP) is a new, out-of-the-ordinary, visual field testing method. Its sensitivity and reliability was tested in 16 patients (32 eyes) with ocular hypertension and 21 patients (37 eyes) with early chronic glaucoma. Significant defects were found in almost 10% of hypertensive eyes and in 67.7% of glaucomatous eyes. FDP is an effective and sensitive technique for glaucoma functional loss assessment.

Estimating glaucomatous anatomical damage by computerized automated perimetry

The ability of two methods (the Glaucoma Staging System and the Functional Score index) in estimating anatomical damage from automated visual field data was studied in 100 patients with chronic open-angle glaucoma. The level of association between functional and anatomical loss (classified by cup/disk ratio assessment) was satisfactory in both systems. Both the GSS (Glaucoma Staging System) and the FS (Functional Score) could be useful for estimating and quantifying the glaucomatous anatomical damage, both in the day-to-day clinical practice and in research.

Capsulorhexis in mature cataracts: why not?

Continuous circular capsulorhexis is now widely used in cataract surgery. In the case of mature cataract, however, this technique may be difficult due to the poor visibility of the anterior capsule. This problem can be overcome performing capsulorhexis under air. A small amount of a high molecular weight viscoelastic agent is injected near the incision, so as to avoid air escaping from the anterior chamber. Visibility is good and the handling of the anterior capsule is easy and safe.

Spontaneous hyphaema from persistent remnant of the pupillary membrane. A case report

A spontaneous unilateral hyphaema in a 75-year-old woman, due to bleeding from iris vessels, a remnant of the pupillary membrane, was observed. Hyphaema was completely resorbed after 24 h. Fluorescein angiography showed the presence of a blood circulation in the anomalous vessels and a diffusion of fluorescein from saccular dilatations on the inferior vessel.