Clinical Diagnosis Of Glaucoma Research Articles

Importance of genetic studies in the diagnosis of glaucoma

Glaucoma is the world's leading cause of irreversible blindness being a known family grouping disease with a strong hereditary component. Based on the age of onset and other clinical characteristics, glaucoma has been classified into primary congenital glaucoma (PCG), juvenile glaucoma (JG), and primary open‐angle glaucoma (POAG), the latter occurring in adulthood. Early‐onset forms of glaucoma such as, PCG and JG, are typically monogenic diseases inherited as Mendelian autosomal dominant or recessive traits, whereas adult glaucoma is a complex trait, with multifactorial inheritance.Genetic variants causing early‐onset glaucoma are highly penetrant. Some examples include dominant negative pathogenic variants in the MYOC gene accounting for 10% of JG cases or biallelic pathogenic variants in CYP1B1 gene mainly associated with PCG. In our cohort of 32 patients with a diagnosis of PCG or JG, we have identified two JOAG patients with two different pathogenic variants in the olfactomedin/like domain of MYOC gene and one PGC patient with two heterozygote pathogenic variants in CYP1B1 gene. Familiar segregation studies of these genetic variants in the three families confirm their pathogenicity. On the one hand, segregation studies of both variants identified in MYOC gene revealed its presence in those relatives with a clinical diagnosis of glaucoma and its absence in healthy individuals. On the other hand, parental screening of both variants identified in CYP1B1 showed that each parent is an asymptomatic carrier of one of the variants confirming that our patient present both variants in CYP1B1 gene in compound heterozygosis. Furthermore, heterozygote pathogenic variants in FOXC1 and COL2A1 genes associated with Axenfeld‐Rieger syndrome type 3 and Stickler syndrome type 1, respectively, have been identified in two different patients with PGC. In these cases, glaucoma is a phenotypic trait of both syndromes inherited in an autosomal dominant manner.Family grouping is a known risk factor for glaucoma in the adult, with a risk 7–10 times greater than the observed in general population. The genetic study of adult glaucoma is complex since its transmission mechanisms are sometimes unclear and have variable penetrance and late onset. In our cohort of 65 patients diagnosed with adult glaucoma, we have identified rare genetic variants with uncertain clinic significance in CYP1B1, SIX6, CARD10, MFN1, OPTC, OPTN, and WDR36 glaucoma‐related genes. Some of these variants are classified as hypomorphic alleles that reduce but do not eliminate gene's functionality and they can contribute to late‐onset disorders.Glaucoma is a treatable disease if detected in early stages and treatment can stop visual loss, however if damage has already occurred it cannot be reverted. Therefore, to identify a genetic cause associated with glaucoma is not only beneficial for the patient but also to detect asymptomatic carriers of the disease in the family‐relatives, which will be susceptible for early treatment. Therefore, proper genetic analysis may provide more accurate information on the prognosis and the adequacy of the therapeutic approach to personalize the treatment of glaucoma.

Normative Percentiles of Retinal Nerve Fiber Layer Thickness and Glaucomatous Visual Field Loss.

Circumpapillary retinal nerve fiber layer thickness (RNFLT) measurement aids in the clinical diagnosis of glaucoma. Spectral domain optical coherence tomography (SD-OCT) machines measure RNFLT and provide normative color-coded plots. In this retrospective study, we investigate whether normative percentiles of RNFLT (pRNFLT) from Spectralis SD-OCT improve prediction of glaucomatous visual field loss over raw RNFLT. A longitudinal database containing OCT scans and visual fields from Massachusetts Eye & Ear glaucoma clinic patients was generated. Reliable OCT-visual field pairs were selected. Spectralis OCT normative distributions were extracted from machine printouts. Supervised machine learning models compared predictive performance between pRNFLT and raw RNFLT inputs. Regional structure-function associations were assessed with univariate regression to predict mean deviation (MD). Multivariable classification predicted MD, pattern standard deviation, MD change per year, and glaucoma hemifield test. There were 3016 OCT-visual field pairs that met the reliability criteria. Spectralis norms were found to be independent of age, sex, and ocular magnification. Regional analysis showed significant decrease in R2 from pRNFLT models compared to raw RNFLT models in inferotemporal sectors, across multiple regressors. In multivariable classification, there were no significant improvements in area under the curve of receiver operating characteristic curve (ROC-AUC) score with pRNFLT models compared to raw RNFLT models. Our results challenge the assumption that normative percentiles from OCT machines improve prediction of glaucomatous visual field loss. Raw RNFLT alone shows strong prediction, with no models presenting improvement by the manufacturer norms. This may result from insufficient patient stratification in tested norms. Understanding correlation of normative databases to visual function may improve clinical interpretation of OCT data.

Segmentation of Optic Disc and Optic Cup Based on Two-Layer Level Set with Sparse Shape Prior Constraint in Fundus Images

Glaucoma is a common high-incidence eye disease. The detection of the optic cup and optic disc in fundus images is one of the important steps in the clinical diagnosis of glaucoma. However, the fundus images are generally intensity inhomogeneity, and complex organizational structure, and are disturbed by blood vessels and lesions. In order to extract the optic disc and optic cup regions more accurately, we propose a segmentation method of the optic disc and optic cup in fundus image based on distance regularized two-layer level with sparse shape prior constraint. The experimental results show that our method can segment the optic disc and optic cup region more accurately and obtain satisfactory results.

Candidate Glaucoma Biomarkers: From Proteins to Metabolites, and the Pitfalls to Clinical Applications.

Simple SummaryGlaucoma is a devastating eye disease causing progressive vision loss and consequent irreversible blindness. The global prevalence of glaucoma is estimated at 80 million people, with a projected increase in the number of people affected to 112 million by 2040. The clinical diagnosis of glaucoma usually occurs late, by which time up to 40% of neurosensory cells may be lost. There is an overriding need for early diagnosis systems based on the analysis of glaucoma biomarkers. However, plenty of candidate biomarkers have been published to date in humans, without clear clinical translation. In this review, we have summarized the efforts carried out for the discovery of proteomics- and metabolomics-based glaucoma biomarkers in blood, aqueous humor, tears, and ocular tissues from human subjects. The huge amount of data without real clinical application merits a new integrative approach, allowing future diagnostic tests to be based on local and/or systemic biomarkers of glaucoma.Glaucoma is an insidious group of eye diseases causing degeneration of the optic nerve, progressive loss of vision, and irreversible blindness. The number of people affected by glaucoma is estimated at 80 million in 2021, with 3.5% prevalence in people aged 40–80. The main biomarker and risk factor for the onset and progression of glaucoma is the elevation of intraocular pressure. However, when glaucoma is diagnosed, the level of retinal ganglion cell death usually amounts to 30–40%; hence, the urgent need for its early diagnosis. Molecular biomarkers of glaucoma, from proteins to metabolites, may be helpful as indicators of pathogenic processes observed during the disease’s onset. The discovery of human glaucoma biomarkers is hampered by major limitations, including whether medications are influencing the expression of molecules in bodily fluids, or whether tests to validate glaucoma biomarker candidates should include human subjects with different types and stages of the disease, as well as patients with other ocular and neurodegenerative diseases. Moreover, the proper selection of the biofluid or tissue, as well as the analytical platform, should be mandatory. In this review, we have summarized current knowledge concerning proteomics- and metabolomics-based glaucoma biomarkers, with specificity to human eye tissue and fluid, as well the analytical approach and the main results obtained. The complex data published to date, which include at least 458 different molecules altered in human glaucoma, merit a new, integrative approach allowing for future diagnostic tests based on the absolute quantification of local and/or systemic biomarkers of glaucoma.

Development and Validation of a Preference-Based Glaucoma Utility Instrument Using Discrete Choice Experiment

A glaucoma-specific instrument for estimating utilities across the spectrum of glaucoma severity is currently lacking, hindering the assessment of the cost-effectiveness of glaucoma treatments. To develop and validate the preference-based Glaucoma Utility Instrument (Glau-U) and to ascertain the association between Glau-U utilities and severity of glaucoma and vision impairment. This cross-sectional study was conducted in 2 stages at the Singapore National Eye Centre glaucoma clinics. Stage 1 focused on the identification and pretesting of the Glau-U attributes and was carried out between June 2009 and May 2016. Stage 2 involved the development and administration of the discrete choice experiment (DCE) survey and tasks and was conducted between May 7, 2018, and December 11, 2019. Stage 2 participants were English- or Mandarin-speaking Singaporean citizens or permanent residents of Chinese, Malay, or Indian ethnicity who were 40 years or older and had a clinical diagnosis of glaucoma in at least 1 eye. Glau-U comprised 6 quality-of-life attributes: activities of daily living, lighting and glare, movement, eye discomfort, other effects of glaucoma, and social and emotional effects. The descriptions or response options for these attributes were no difficulty or never, some difficulty or sometimes, or severe difficulty or often. Utility weights for Glau-U were developed using a DCE questionnaire, which was interviewer administered to participants. Mixed logit regression determined utility weights for each health state. Glau-U utility weights across better- or worse-eye glaucoma and vision impairment severity were calculated using 1-way analysis of variance. Correlations between Glau-U utilities and better- or worse-eye visual fields and EuroQol 5-Dimension utilities were ascertained to assess convergent and divergent validity. Of the 304 participants (mean [SD] age, 68.3 [8.7] years; 182 men [59.9%]), 281 (92.4%) had no vision impairment in the better eye, 13 (4.3%) had mild impairment, and 10 (3.3%) had moderate to severe vision impairment. Mean (SD) Glau-U utilities decreased as better-eye glaucoma severity increased (none: 0.73 [0.21]; mild: 0.66 [0.21]; moderate: 0.66 [0.20]; severe: 0.60 [0.28]; and advanced or end-stage: 0.22 [0.38]; P < .001), representing reductions of 20.7% to 76.1% in quality-adjusted life-years compared with a health state that included preperimetric glaucoma. Mean (SD) Glau-U utilities also decreased as better-eye vision impairment worsened from 0.67 (0.23) for none to 0.58 (0.32) for mild to 0.46 (0.29) for moderate to severe vision impairment. Glau-U utilities demonstrated moderate correlations with better-eye (r = 0.34; P < .001) and worse-eye (r = 0.33; P < .001) mean deviation scores and low correlations with EuroQol 5-Dimension utilities (r = 0.22; P < .001), supporting convergent and divergent validity. Use of Glau-U revealed large decrements in utility that were associated with late-stage glaucoma, suggesting that this new instrument may be useful for cost-effectiveness analyses of interventions and informing resource allocation policies for glaucoma and vision loss.

A wearable contact lens sensor for noninvasive in-situ monitoring of intraocular pressure

Glaucoma is the second leading cause of blindness in the world. Intraocular pressure (IOP) is a primary indicator of glaucoma which can be measured for the treatment of the disease. This paper presents a piezo-resistive principle pressure sensor to monitor IOP continuously and non-invasively. The sensor is designed based on the Wheatstone bridge circuit and fabricated by the spray-coating method. The hybrid nanomaterials of graphene and carbon nanotubes are introduced as sensing layers which are embedded inside the soft contact lens substrate composed of flexible polydimethyl siloxane (PDMS) and parylene. The sensing performance is discussed followed by a brief description of our sensor design and fabrication. Tests on a PDMS eyeball model indicate that it has a high sensitivity of 36.01 μV mmHg−1. Also, the frequency response and the ability to track dynamic pressure change cycles are demonstrated in normal IOP variation range from 9 to 34 mmHg. It shows good repeatability and linearity, and can accurately track fluctuating IOP. Thus, this sensor, with its ease of fabrication and simple design, as well as allowance for continuous pressure measurement, offers a promising approach for IOP monitoring in clinical diagnosis of glaucoma.

Optic Disc Segmentation Using Attention-Based U-Net and the Improved Cross-Entropy Convolutional Neural Network.

Medical image segmentation is an important part of medical image analysis. With the rapid development of convolutional neural networks in image processing, deep learning methods have achieved great success in the field of medical image processing. Deep learning is also used in the field of auxiliary diagnosis of glaucoma, and the effective segmentation of the optic disc area plays an important assistant role in the diagnosis of doctors in the clinical diagnosis of glaucoma. Previously, many U-Net-based optic disc segmentation methods have been proposed. However, the channel dependence of different levels of features is ignored. The performance of fundus image segmentation in small areas is not satisfactory. In this paper, we propose a new aggregation channel attention network to make full use of the influence of context information on semantic segmentation. Different from the existing attention mechanism, we exploit channel dependencies and integrate information of different scales into the attention mechanism. At the same time, we improved the basic classification framework based on cross entropy, combined the dice coefficient and cross entropy, and balanced the contribution of dice coefficients and cross entropy loss to the segmentation task, which enhanced the performance of the network in small area segmentation. The network retains more image features, restores the significant features more accurately, and further improves the segmentation performance of medical images. We apply it to the fundus optic disc segmentation task. We demonstrate the segmentation performance of the model on the Messidor dataset and the RIM-ONE dataset, and evaluate the proposed architecture. Experimental results show that our network architecture improves the prediction performance of the base architectures under different datasets while maintaining the computational efficiency. The results render that the proposed technologies improve the segmentation with 0.0469 overlapping error on Messidor.

Patients' perception of glaucoma diagnosis practice: Results from a survey of glaucoma patients in North India.

This study assesses the practice patterns of diagnosing ophthalmologists, as reported by glaucoma patients attending specialty glaucoma clinics in urban and rural areas of North India, for a second opinion. Prospective cross-sectional study using a structured interview-based survey was conducted from 1 November 2011 to 31 October 2012 on patients attending two specialty glaucoma care facilities in North India. Both clinics were in North India; however, one was rural (Kaithal) and one was urban (Delhi). Patients were asked through descriptions of machines and processes, regarding practice patterns of their glaucoma diagnosing ophthalmologists. The interview was conducted by ophthalmic assistants in tune with the vernacular of the region, in a language understood by the interviewee. A total of 1506 patients consented to participate in the survey. The majority of patients reported undergoing tests for intraocular pressure measurement; however, 56-60% of these tests were carried out by the non-contact tonometer. More than 90% of patients reported no knowledge regarding the type and severity of the glaucoma they suffered from, and even less reported undergoing gonioscopy (3.6% Karnal and 16% Delhi). 84-86% patients who underwent perimetry reported undergoing at least some digital imaging of the optic disc. Better counselling of, and communication with, the patient would help increase their awareness regarding their condition and the care required. This has the potential to enable better compliance with and adherence to treatment. Standardized training of ophthalmologists to improve clinical diagnosis of glaucoma would also go a long way.

Research progression of visual evoked potential in glaucomatous visual function evaluation

Visual evoked potential (VEP) is often used for the objective evaluation for impairment of visual function. Although these VEP-related tests have good results in the assessment of glaucoma, their application as routine tests in the clinical diagnosis of glaucoma is limited due to the time consumption and easy interference by the environment and the reliance on the experience of the doctors. However, several new VEP detection modes have emerged in the past decade, such as short-duration transient VEP and isolated check VEP. Preliminary studies have shown that both of them have good diagnostic ability in glaucoma, and more studies on the clinical application of these latest technologies are conducive to further understanding of their value in the visual function evaluation and follow-up of glaucoma. (Chin J Ophthalmol, 2020, 56: 61-65).

Evaluation of a Qualitative Approach for Detecting Glaucomatous Progression Using Wide-Field Optical Coherence Tomography Scans.

PurposeTo determine the effectiveness of detecting glaucomatous progression by a qualitative evaluation of wide-field (12 × 9 mm) scans on optical coherence tomography imaging. This method was compared to a conventional quantitative analysis of the global circumpapillary retinal nerve fiber layer (cpRNFL) thickness.MethodsA total of 409 eyes with a clinical diagnosis of glaucoma or suspected glaucoma for which two wide-field scans were obtained at least 1 year apart (n = 125) and within one session (n = 284) were included to determine the sensitivity of detecting progression at 95% specificity. Qualitative OCT evaluation was performed in a similar manner to flicker chronoscopy by superimposing the two scans, and the progression probability was graded. A quantitative event-based analysis of the global cpRNFL thickness also was performed.ResultsThirty-three and 25 eyes were deemed to have progressed based on qualitative and quantitative approaches, respectively (P = 0.152). A post hoc review of cases where the two methods disagreed revealed that all eyes missed by the quantitative analysis had established glaucomatous damage that appeared to show characteristic patterns of progression. All eyes missed by the qualitative evaluation appeared to be free of such established damage, and instead showed a generalized reduction in cpRNFL thickness.ConclusionsQualitative evaluation of OCT imaging information more frequently detected change consistent with known patterns of glaucomatous progression than global cpRNFL thickness, warranting further studies to evaluate its value.Translational RelevanceA framework for qualitatively evaluating progressive glaucomatous changes on OCT imaging clinically shows promise.

Evaluation of a Region-of-Interest Approach for Detecting Progressive Glaucomatous Macular Damage on Optical Coherence Tomography.

PurposeTo evaluate a manual region-of-interest (ROI) approach for detecting progressive macular ganglion cell complex (GCC) changes on optical coherence tomography (OCT) imaging.MethodsOne hundred forty-six eyes with a clinical diagnosis of glaucoma or suspected glaucoma with macular OCT scans obtained at least 1 year apart were evaluated. Changes in the GCC thickness were identified using a manual ROI approach (ROIM), whereby region(s) of observed or suspected glaucomatous damage were manually identified when using key features from the macular OCT scan on the second visit. Progression was also evaluated using the global GCC thickness and an automatic ROI approach (ROIA), where contiguous region(s) that fell below the 1% lower normative limit and exceeded 288 μm2 in size were evaluated. Longitudinal signal-to-noise ratios (SNRs) were calculated for progressive changes detected by each of these methods using individualized estimates of test–retest variability and age-related changes, obtained from 303 glaucoma and 394 healthy eyes, respectively.ResultsOn average, the longitudinal SNR for the global thickness, ROIA and ROIM methods were −0.90 y−1, −0.91 y−1, and −1.03 y−1, respectively, and was significantly more negative for the ROIM compared with the global thickness (P = 0.003) and ROIA methods (P = 0.021).ConclusionsProgressive glaucomatous macular GCC changes were optimally detected with a manual ROI approach.Translational RelevanceThese findings suggests that an approach based on a qualitative evaluation of OCT imaging information and consideration of known patterns of damage can improve the detection of progressive glaucomatous macular damage.

Detecting Glaucomatous Progression With a Region-of-Interest Approach on Optical Coherence Tomography: A Signal-to-Noise Evaluation.

PurposeTo compare two region-of-interest (ROI) approaches and a global thickness approach for capturing progressive circumpapillary retinal nerve fiber layer (cpRNFL) changes on optical coherence tomography (OCT) imaging.MethodsProgressive cpRNFL thickness changes were evaluated in 164 eyes with a clinical diagnosis of glaucoma or suspected glaucoma; all eyes underwent optic disc OCT imaging on two visits at least 1 year apart. Such changes were evaluated with a manual ROI approach (ROIM), which involved manual identification of region(s) of observed or suspected glaucomatous damage. The ROIM was compared with an automatic ROI approach (ROIA), where regions were automatically identified if the cpRNFL thickness fell below the 1% lower normative limits, and to global cpRNFL thickness. These methods were compared using longitudinal signal-to-noise ratios (SNRs), calculated based upon individualized estimates of measurement variability and age-related changes for each ROI, obtained from 321 glaucoma eyes and 394 healthy eyes, respectively.ResultsThe average longitudinal SNR of the ROIM, ROIA and global thickness methods were −0.46, −0.39, and −0.30 y−1, respectively. The average longitudinal SNR for the ROIM was significantly more negative compared with both the ROIA and global thickness methods (P = 0.005 for both).ConclusionsA manual ROI approach was the optimal method for detecting progressive cpRNFL loss compared with an automatic ROI approach and the global cpRNFL thickness measure.Translational RelevanceThese findings highlight the potential advantages conferred by a careful qualitative evaluation of OCT imaging for detecting glaucoma progression.

What's on TV? Detecting age-related neurodegenerative eye disease using eye movement scanpaths.

Purpose: We test the hypothesis that age-related neurodegenerative eye disease can be detected by examining patterns of eye movement recorded whilst a person naturally watches a movie.Methods: Thirty-two elderly people with healthy vision (median age: 70, interquartile range [IQR] 64–75 years) and 44 patients with a clinical diagnosis of glaucoma (median age: 69, IQR 63–77 years) had standard vision examinations including automated perimetry. Disease severity was measured using a standard clinical measure (visual field mean deviation; MD). All study participants viewed three unmodified TV and film clips on a computer set up incorporating the Eyelink 1000 eyetracker (SR Research, Ontario, Canada). Eye movement scanpaths were plotted using novel methods that first filtered the data and then generated saccade density maps. Maps were then subjected to a feature extraction analysis using kernel principal component analysis (KPCA). Features from the KPCA were then classified using a standard machine based classifier trained and tested by a 10-fold cross validation which was repeated 100 times to estimate the confidence interval (CI) of classification sensitivity and specificity.Results: Patients had a range of disease severity from early to advanced (median [IQR] right eye and left eye MD was −7 [−13 to −5] dB and −9 [−15 to −4] dB, respectively). Average sensitivity for correctly identifying a glaucoma patient at a fixed specificity of 90% was 79% (95% CI: 58–86%). The area under the Receiver Operating Characteristic curve was 0.84 (95% CI: 0.82–0.87).Conclusions: Huge data from scanpaths of eye movements recorded whilst people freely watch TV type films can be processed into maps that contain a signature of vision loss. In this proof of principle study we have demonstrated that a group of patients with age-related neurodegenerative eye disease can be reasonably well separated from a group of healthy peers by considering these eye movement signatures alone.

Conjunctivochalasis as a Contributing Factor for the Development of Ocular Surface Disease in Medically Treated Glaucoma Patients

To evaluate the impact of conjunctivochalasis (CCh) and its severity on the ocular surface parameters of glaucoma subjects treated with topical antiglaucomatous medication. One hundred patients with the clinical diagnosis of glaucoma were recruited for this study. CCh was graded based on the extent of inferior lid margin involvement as follows: 1=single (temporal) location, 2=two locations (nasal and temporal), and 3=whole lid. For all the subjects, the break-up time (BUT), lissamine green (LG) staining, and Schirmer test (under topical anesthesia) was performed for both eyes. Ocular Surface Disease Index (OSDI) questionnaire scores were also noted for each subject. Student t test, Mann-Whitney U test, and Kruskal-Wallis test was used for statistical evaluations. Sixty-three subjects had evidence of CCh; 32 had grade 1, 24 had grade 2, 7 had grade 3 CCh, and 37 glaucoma patients had no evidence of CCh. There were significant differences in the BUT scores (7.2±2.7 vs. 10.1±2.4 s, P<0.001), Schirmer values (7.7±3.9 vs. 13.3.±4.0 mm, P<0.001), LG staining score (1.6±1.0 vs. 0.3±0.5, P<0.001), and the OSDI scores (19.4±17.2 vs. 6.7±5.2, P<0.001) between patients who had CCh and those without CCh. The BUT scores and Schirmer test values of patients with grades 2 and 3 CCh were significantly lower than those of grade 1 CCh and those without CCh (P<0.001). The LG grading and OSDI scores were significantly higher in grade 2 and 3 patients as compared with those with grade 1 CCh and those without CCh (P<0.001). The functional characteristics of the ocular surface appear to be adversely influenced by the presence and the extent of CCh in glaucoma patients.

Wavelength-Dependent Change of Retinal Nerve Fiber Layer Reflectance in Glaucomatous Retinas

Retinal nerve fiber layer (RNFL) reflectance is often used in optical methods for RNFL assessment in clinical diagnosis of glaucoma, yet little is known about the reflectance property of the RNFL under the development of glaucoma. This study measured the changes in RNFL reflectance spectra that occurred in retinal nerve fiber bundles with different degrees of glaucomatous damage. A rat model of glaucoma with laser photocoagulation of trabecular meshwork was used. Reflectance of the RNFL in an isolated retina was measured at wavelengths of 400-830 nm. Cytostructural distribution of the bundles measured optically was evaluated by confocal imaging of immunohistochemistry staining of cytoskeletal components, F-actin, microtubules, and neurofilaments. RNFL reflectance spectra were studied in bundles with normal-looking appearance, early F-actin distortion, and apparent damage of all cytoskeletal components. Changes of RNFL reflectance spectra were studied at different radii (0.22, 0.33, and 0.44 mm) from the optic nerve head (ONH). Bundles in 30 control retinas and 41 glaucomatous retinas were examined. In normal retinas, reflectance spectra were similar along the same bundles. In glaucomatous retinas, reflectance spectra changed along bundles with the spectra becoming flatter as bundle areas approached the ONH. Elevation of intraocular pressure (IOP) causes nonuniform changes in RNFL reflectance across wavelengths. Changes of reflectance spectra occur early in bundles near the ONH and prior to apparent cytoskeletal distortion. Using the ratio of RNFL reflectance measured at different wavelengths can provide early and sensitive detection of glaucomatous damage.

An exploratory study of visual search performance in glaucoma

Visual search plays an integral role in many daily activities. This study aimed to determine whether patients with glaucoma are slower than visually healthy age-matched individuals when searching for items in computer displayed images. Forty participants were recruited for the study: 20 patients with a clinical diagnosis of glaucoma and 20 age-similar visually healthy control subjects. All participants had visual acuity of 6/12 or better. Participants were presented with 20 images with Landolt C symbols and 15 photographic images of everyday scenes on a computer. The time taken by each participant to locate a specified item in each image was recorded. Average search times were calculated across participants and compared between groups. All the patients had visual field defects in both eyes. On average, the patients also differed from control subjects by binocular contrast sensitivity measurements (p = 0.01) and visual acuity (p = 0.003). The patients (mean age = 67 years, S.D.: 10 years) and controls (mean age: 67 years, S.D.: 11 years) were age similar (p = 0.40). The median search time for patients finding target items in photographs of everyday scenes was 15.2 s (interquartile range 9.4-20.6 s) and this was significantly slower than the median time (10.0 s; interquartile range 7.2-10.3 s) taken by the controls (p = 0.007). There was no statistical evidence for a difference in median search times between groups in the Landolt C search task (p = 0.24). Some individuals with glaucomatous visual field defects in both eyes find it especially difficult to locate objects in photographs of everyday scenes when compared to visually healthy individuals of a similar age.

Central Corneal Thickness in Children: Racial Differences (Black vs. White) and Correlation With Measured Intraocular Pressure

To test the hypotheses that the mean central corneal thickness (CCT) of healthy black children is thinner than that of healthy white children and to confirm the relationship between increased CCT and measured intraocular pressure (IOP) in children. This prospective observational case series included 178 eyes of 92 children aged 9 months to 17 years without anterior segment abnormalities or a clinical diagnosis of glaucoma. CCT was measured by ultrasonic pachymetry and IOP was measured by Goldmann or Tono-pen technique. The mean CCT for the 102 eyes of 52 white children was 562+/-35 microm versus 543+/-37 microm for the 66 eyes of 35 black children (P = 0.02). There was a positive relationship between CCT and IOP (P = 0.0002). For every 100 mum increase in CCT, the IOP increased by 2.2+/-0.6 mm Hg. The mean CCT of black children is thinner than that of white children. There is a positive relationship between increasing measured IOP and CCT among children with normal corneas and anterior segments. The interpretation of elevated IOP in eyes with abnormal anterior segment anatomy and thickened corneas awaits further study.