Screening for glaucoma in a general population with the non-mydriatic fundus camera and the frequency doubling perimeter

An interpretable and interactive deep learning algorithm for a clinically applicable retinal fundus diagnosis system by modelling finding-disease relationship

The identification of abnormal findings manifested in retinal fundus images and diagnosis of ophthalmic diseases are essential to the management of potentially vision-threatening eye conditions. Recently, deep learning-based computer-aided diagnosis systems (CADs) have demonstrated their potential to reduce reading time and discrepancy amongst readers. However, the obscure reasoning of deep neural networks (DNNs) has been the leading cause to reluctance in its clinical use as CAD systems. Here, we present a novel architectural and algorithmic design of DNNs to comprehensively identify 15 abnormal retinal findings and diagnose 8 major ophthalmic diseases from macula-centered fundus images with the accuracy comparable to experts. We then define a notion of counterfactual attribution ratio (CAR) which luminates the system's diagnostic reasoning, representing how each abnormal finding contributed to its diagnostic prediction. By using CAR, we show that both quantitative and qualitative interpretation and interactive adjustment of the CAD result can be achieved. A comparison of the model's CAR with experts' finding-disease diagnosis correlation confirms that the proposed model identifies the relationship between findings and diseases similarly as ophthalmologists do.

Impact of illumination spectrum and eye pigmentation on image quality from a fundus camera using transscleral illumination

SIGNIFICANCE

The use of the transscleral illumination approach has the potential to simplify the optical design of fundus cameras. In particular, this approach could allow the use of smaller and cheaper cameras that are easier to use by non-specialists, thereby facilitating a wider spread of eye disease screening programs.

AIM

Our aim was to investigate the suitability of transscleral illumination in a fundus camera system. In particular, we explored the impact of the illumination spectrum and the eye pigmentation on the quality of the image. These factors have never been systematically investigated before in the literature on transscleral illumination.

APPROACH

A fundus camera was constructed using transscleral illumination. We studied the influence of eye pigmentation and choice of illumination spectra on the image quality for a group of 10 individuals with varied skin pigmentation, ranging from pale white (North-European) to darkest brown (African). The influence of the light source spectrum on the image quality was assessed using wavelength filters.

RESULTS

There was a difference of a factor of 100 in the signal level of retinal images between individuals with low and high skin pigmentation. The image contrast was highest using illumination wavelengths of 500 to 600 nm. The illumination level can be adjusted to obtain high-quality images for highly pigmented eyes while keeping the system eye-safe.

CONCLUSIONS

We have demonstrated that a fundus camera with transscleral illumination can provide high-quality images. However, the variations observed in scleral and retinal pigmentation in a practical setting require a system that must be able to adapt illumination and/or exposure to the individual patient.

Validation of a portable, non-mydriatic fundus camera compared to gold standard dilated fundus examination using slit lamp biomicroscopy for assessing the optic disc for glaucoma

Purpose

To evaluate the sensitivity and specificity of a portable non-mydriatic fundus camera to assess the optic disc for glaucoma.

Methods

We conducted a single-site, cross-sectional, observational, instrument validation study. Non-mydriatic fundus photographs centred at the optic disc were obtained from 276 eyes of 68 glaucoma and 70 normal patients, using a portable fundus camera (Smartscope, Optomed, Oulu, Finland). A senior Glaucoma consultant, masked to the patient’s study participation, performed a gold standard dilated fundus examination to make the diagnosis of glaucoma. Following this, a mydriatic photograph was taken by a standard table-top fundus camera. All the images were digitalized and de-identified by an independent investigator and presented to two remote graders, masked to the patients, their diagnoses, and photographic modality. Based on individual disc characteristics, a diagnosis of screening positive or negative for glaucoma was made. In the end, the independent investigator re-identified the images. Sensitivity and specificity to detect glaucoma with the undilated Smartscope camera was calculated compared to dilated fundus examination.

Results

Grading remote images taken with the portable non-mydriatic fundus camera showed a sensitivity of 96.3% (95% confidence interval (CI): 91.6–98.8%) and 94.8% (95% CI: 89.7–97.9%) and a specificity of 98.5% (95% CI: 94.9–99.8%) and 97.8% (95% CI: 93.9–99.6%) for the two graders respectively as compared to gold standard dilated fundus examination.

Conclusion

The non-mydriatic Smartscope fundus images have high sensitivity and specificity for diagnosing glaucoma remotely and thus may be an effective tool for use in community outreach programs.

FDT Perimetry for Glaucoma Detection in Comprehensive Health Checkup Service

We aimed to investigate the efficacy of frequency doubling technology (FDT) perimetry for glaucoma detection in comprehensive screening examinations. We performed a retrospective analysis of prospectively collected data of participants who underwent a comprehensive health checkup service. Participants with glaucoma were excluded. In the first year, 2024 participants (46.8 ± 9.4 years) who underwent FDT perimetry and fundus photography were classified as the FDT group, whereas 3052 participants (42.2 ± 8.2 years) who underwent only fundus photography were classified as the non-FDT control group. Participants with abnormal findings on FDT perimetry and/or fundus photography were recommended to undergo further complete examination. All participants reported whether they had been newly diagnosed with glaucoma within 2 years of the first visit. In the FDT group, 23 (1.14%) participants were newly diagnosed with glaucoma. Among them, 20 (87.0%) had abnormal FDT perimetry findings and 12 (52.2%) had abnormal findings on fundus photography. The positive-predictive value (PPV) of FDT perimetry was 16.5% (20/121) and that of fundus photography was 13.3% (12/90). In participants with abnormal findings on both tests, the PPV was 26.2%. In the non-FDT group, 15 (0.49%) participants were newly diagnosed with glaucoma. Among them, 9 (60.0%) had abnormal findings on fundus photography. The PPV of fundus photography was 10.8% (9/83). The glaucoma detection rate, analyzed using age adjustment, was significantly higher in the FDT group than that in the non-FDT group (0.97% versus 0.47%, P=0.041). FDT perimetry, even if performed by nonspecialized physicians, could improve glaucoma detection when used in addition to fundus photography. This study was registered with UMIN000037951.

Comparison of glaucoma patients referred by glaucoma screening versus referral from primary eye clinic

Purpose

To investigate whether mass glaucoma screening relative to opportunistic case finding at a primary eye clinic is helpful for early detection of glaucoma.

Methods

Subjects referred by glaucoma screening (by non-contact tonometry and non-mydriatic fundus photography; group A, n = 220) and from a primary eye clinic (group B, n = 327) were retrospectively recruited. The positive predictive value (PPV) for glaucoma and the rate of glaucoma awareness were compared. Also, for the newly diagnosed glaucoma (‘definite glaucoma’) patients, the demographics and structural and functional severities of glaucoma were compared.

Results

The PPV for definite glaucoma was 25.5% for group A and 52.4% for group B. The rate of false-positive for ‘glaucoma referral to tertiary hospital’ was significantly higher for group A than for group B (38.6 vs. 18.3%, P < 0.001). Among the definite-glaucoma patients (group A: n = 56; group B: n = 182), the proportion of glaucoma awareness was significantly higher in group B (69.2%) than in group A (8.9%, P < 0.001). The mean deviation (MD) of visual field (VF) was significantly higher in group A than in group B (–3.08 ± 3.99 vs. –6.70 ± 7.29 dB, P_adjusted = 0.040), and the inferior and inferotemporal ganglion cell-inner plexiform layer (GCIPL) thicknesses tended to be greater in group A than in group B, with marginal significance (P_adjusted < 0.10).

Conclusions

Glaucoma screening can be helpful for early detection of glaucoma. However, improvement of the screening strategy is needed in order to enhance its specificity for glaucoma.

An evidence-based approach to the routine use of optical coherence tomography

Optical coherence tomography is an imaging technology that has revolutionised the detection, assessment and management of ocular disease. It is now a mainstream technology in clinical practice and is performed by non-specialised personnel in some settings. This article provides a clinical perspective on the implications of that movement and describes best practice using multimodal imaging and an evidence-based approach. Practical, illustrative guides on the interpretation of optical coherence tomography are provided for three major diseases of the ocular fundus, in which optical coherence tomography is often crucial to management: age-related macular degeneration, diabetic retinopathy and glaucoma. Topics discussed include: cross-sectional and longitudinal signs in ocular disease, so-called 'red-green' disease whereby clinicians rely on machine/statistical comparisons for diagnosis in managing treatment-naïve patients, and the utility of optical coherence tomography angiography and machine learning.

Glaucoma detection with damato multifixation campimetry online

PurposeTo evaluate Damato Multifixation Campimetry Online (DMCO), a free-of-charge internet-based visual field test. DMCO exists in three versions: DMCO BASIC, DMCO STANDARD, and DMCO ADVANCED. The main focus was (i) to investigate the sensitivity and the specificity of the existing DMCO versions in the detection of glaucomatous visual field loss and (ii) to define and evaluate algorithms for the interpretation of DMCO results.MethodsThe study design was an evaluation of a diagnostic test and included 97 individuals performing DMCO and white-on-white perimetry. Interpretation algorithms were devised to define abnormality, and these were evaluated using the Glaucoma Staging System as gold standard. Receiver operating characteristic (ROC) curves and area under the ROC (AUC) were calculated.ResultsAUCs from 15 algorithms ranged from 0.79 to 0.90. The most promising algorithm combined results from two successive DMCO STANDARD tests. The sensitivity was highly dependent on the severity of glaucoma. Hence, for eyes with mild, moderate, advanced, and severe glaucoma, the DMCO test demonstrated a sensitivity of 11.8, 71.4, 100, and 100%, respectively. The specificity was as high as 98.1%. Median duration per eye to complete the DMCO STANDARD test was 86 s for the control group and 125 s in participants with glaucoma.ConclusionsDMCO shows promise as a free-of-charge online tool to identify glaucomatous visual field defects in a preselected population. Ongoing studies are evaluating the use of DMCO in a nonselected population.

Methodology and reporting of diagnostic accuracy studies of automated perimetry in glaucoma: evaluation using a standardised approach

PURPOSE

To evaluate methodological and reporting quality of diagnostic accuracy studies of perimetry in glaucoma and to determine whether there had been any improvement since the publication of the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines.

METHODS

A systematic review of English language articles published between 1993 and 2013 reporting the diagnostic accuracy of perimetry in glaucoma. Articles were appraised for methodological quality using the 14-item Quality assessment tool for diagnostic accuracy studies (QUADAS) and evaluated for quality of reporting by applying the STARD checklist.

RESULTS

Fifty-eight articles were appraised. Overall methodological quality of these studies was moderate with a median number of QUADAS items rated as 'yes' equal to nine (out of a maximum of 14) (IQR 7-10). The studies were often poorly reported; median score of STARD items fully reported was 11 out of 25 (IQR 10-14). A comparison of the studies published in 10-year periods before and after the publication of the STARD checklist in 2003 found quality of reporting had not substantially improved.

CONCLUSIONS

Methodological and reporting quality of diagnostic accuracy studies of perimetry is sub-optimal and appears not to have improved substantially following the development of the STARD reporting guidance. This observation is consistent with previous studies in ophthalmology and in other medical specialities.

Diagnostic Accuracy of Nonmydriatic Fundus Photography for the Detection of Glaucoma in Diabetic Patients

Purpose. To determine the diagnostic accuracy for glaucoma of a set of criteria with nonmydriatic monoscopic fundus photography (NMFP) in diabetics. Methods. Diabetics recruited from a screening program for diabetic retinopathy and diabetic glaucoma patients recruited from our glaucoma unit were included. Any patient with evidence of diabetic retinopathy was excluded. Diabetic patients had to have no visual field defects to be included as controls. Glaucoma patients had to have a glaucomatous field defect in at least one eye to be included. One NMFP was taken per eye for all subjects. These photographs were evaluated by two masked glaucoma specialists for the presence of the following: bilateral cup to disc (C/D) ratio ≥0.6, notching or thinning of the neuroretinal rim, disc hemorrhages, and asymmetry in the C/D ratio between both eyes ≥0.2. This evaluation led to a dichotomous classification: if any of the above criteria was present, the patient was classified as glaucoma. If none were present, the patient was classified as normal. Results. 72 control subjects and 72 glaucoma patients were included. Evaluation of NMFP had a sensitivity of 79.17% and a specificity of 80.56% for specialist 1 and a sensitivity of 72.22% and a specificity of 88.88% for specialist 2 for the detection of glaucoma. The overall accuracy was 79.83% and 80.55%, respectively. Discussion. NMFP evaluation by a glaucoma specialist may be useful for the detection of glaucoma in diabetics.

Diagnostic Accuracy of Technologies for Glaucoma Case-Finding in a Community Setting

PURPOSE

To assess case-finding performance of the Frequency Doubling Technology Perimeter (FDT) (Carl Zeiss Meditec, Inc., Dublin, CA), Moorfields Motion Displacement Test (MMDT) (Moorfields Eye Hospital, London, UK), iVue optical coherence tomography (OCT) (Optovue Inc., Fremont, CA), and ocular response analyzer (ORA) (Reichert Ophthalmic Instruments, Depew, NY), alone or combined, for primary open-angle glaucoma (POAG).

DESIGN

Cross-sectional, observational, community-based study.

PARTICIPANTS

A total of 505 subjects aged ≥60 years recruited from a community setting using no predefined exclusion criteria.

METHODS

Subjects underwent 4 index tests conducted by a technician unaware of subjects' ocular status. FDT and MMDT were used in suprathreshold mode. iVue OCT measured ganglion cell complex and retinal nerve fiber layer (RNFL) thickness. Reference standard was full ophthalmic examination by an experienced clinician who was masked to index test results. Subjects were classified as POAG (open drainage angle, glaucomatous optic neuropathy, and glaucomatous field defect), glaucoma suspect, ocular hypertension, or non-POAG/nonocular hypertension.

MAIN OUTCOME MEASURES

Test performance evaluated the individual as the unit of analysis. Diagnostic accuracy was assessed using predefined cutoffs for abnormality, generating sensitivity, specificity, and likelihood ratios. Continuous data were used to derive estimates of sensitivity at 90% specificity and partial area under the receiver operating characteristic curve (AUROC) plots from 90% to 100% specificity.

RESULTS

From the reference standard examination, 26 subjects (5.1%) had POAG and 32 subjects (6.4%) were glaucoma suspects. Sensitivity (95% confidence interval) at 90% specificity for detection of glaucoma suspect/POAG combined was 41% (28-55) for FDT, 35% (21-48) for MMDT, and 57% (44-70) for best-performing OCT parameter (inferior quadrant RNFL thickness); for POAG, sensitivity was 62% (39-84) for FDT, 58% (37-78) for MMDT, and 83% (68-98) for inferior quadrant RNFL thickness. Partial AUROC was significantly greater for inferior RNFL thickness than visual-function tests (P < 0.001). Post-test probability of glaucoma suspect/POAG combined and definite POAG increased substantially when best-performing criteria were combined for FDT or MMDT, iVue OCT, and ORA.

CONCLUSIONS

Diagnostic performance of individual tests gave acceptable accuracy for POAG detection. Low specificity of visual-function tests precludes their use in isolation, but case detection improves by combining RNFL thickness analysis with visual function tests.

The East London glaucoma prediction score: web-based validation of glaucoma risk screening tool

AIM

It is difficult for Optometrists and General Practitioners to know which patients are at risk. The East London glaucoma prediction score (ELGPS) is a web based risk calculator that has been developed to determine Glaucoma risk at the time of screening. Multiple risk factors that are available in a low tech environment are assessed to provide a risk assessment. This is extremely useful in settings where access to specialist care is difficult. Use of the calculator is educational. It is a free web based service. Data capture is user specific.

METHOD

The scoring system is a web based questionnaire that captures and subsequently calculates the relative risk for the presence of Glaucoma at the time of screening. Three categories of patient are described: Unlikely to have Glaucoma; Glaucoma Suspect and Glaucoma. A case review methodology of patients with known diagnosis is employed to validate the calculator risk assessment.

RESULTS

Data from the patient records of 400 patients with an established diagnosis has been captured and used to validate the screening tool. The website reports that the calculated diagnosis correlates with the actual diagnosis 82% of the time. Biostatistics analysis showed: Sensitivity = 88%; Positive predictive value = 97%; Specificity = 75%.

CONCLUSION

Analysis of the first 400 patients validates the web based screening tool as being a good method of screening for the at risk population. The validation is ongoing. The web based format will allow a more widespread recruitment for different geographic, population and personnel variables.

Prevalence and correlates of self-reported nonadherence with eye drop treatment: the Belgian Compliance Study in Ophthalmology (BCSO)

PURPOSE

This study aimed to investigate (1) the prevalence of nonadherence with eye drop treatment; (2) selected correlates of nonadherence at the patient and health-care organization level; and (3) the diagnostic value of the ophthalmologists' ratings, using patients' self-reports as standard.

METHODS

This cross-sectional multicenter survey used questionnaires for ophthalmologists and their patients to assess self-reported nonadherence and its correlates. One item, using a 4-point scale [never (ie, adherent) to daily], asked the patients whether they had forgotten to administer eye drops during the past 2 weeks. Ophthalmologists rated their patients as adherent or nonadherent. Nonadherence was also determined by combined methods, whereby either could indicate nonadherence. Given the nested structure of the data, multilevel modeling was used to investigate self-reported nonadherence-correlates. Diagnostic values of ophthalmologists' report were calculated.

RESULTS

Of 663 patients (48% female, 44% >69 years), nonadherence was indicated in 39.2% (n=260) through self-reporting, 2.1% (n=14) through ophthalmologists' ratings, and 40% (n=266) through combined measures. The multivariable, multilevel model showed following significant nonadherence-correlates: Male sex (P=0.01), younger age (P=0.027), and higher-dose frequency (P=0.001). No significant correlation with treating ophthalmologist (P=0.21) could be seen. Yet, the patients visiting their ophthalmologists at least every 3 months were less nonadherent than patients with fewer consultations (P=0.01). The ophthalmologists' report showed a sensitivity and specificity of 3% and 98.5%, respectively.

CONCLUSIONS

The prevalence of self-reported nonadherence was congruent with literature. The patients visiting their ophthalmologists at least every 3 months have a lower risk of nonadherence. Ophthalmologist report is an insensitive method for detecting nonadherence.

Prevalence and determinants of glaucoma in citizens of qatar aged 40 years or older: a community-based survey

Background:

We present the prevalence and determinants of glaucoma among subjects 40 years of age and older in Qatar.

Materials and Methods:

This community-based survey was held in 2009 at 49 randomly selected clusters. Demographic details and history of glaucoma was collected by the nurses. Ophthalmologists evaluated the optic disc and retina using a digital camera housed in a mobile van. Visual field was tested with an automated perimeter, the intraocular pressure with an applanation tonometer and the angle of the anterior chamber by gonioscopy. A panel of glaucoma experts diagnosed subjects with glaucoma.

Results:

This survey enrolled 3,149 (97.3%) participants. The age- and sex-adjusted prevalence of glaucoma in the population aged 40 years and older was 1.73% (95% confidence intervals [CI] 1.69-1.77). Accordingly, 5,641 individuals in this age group in Qatar would have glaucoma. Chronological age of 60 years and older (Odds ratio [OR] 11.1) and the presence of myopia (OR 1.78) were predictors of glaucoma. Open-angle glaucoma was diagnosed in 44 (65.7%) individuals with glaucoma. In nine (13.4%) and 15 (20.9%) subjects, angle closure glaucoma and other (post-traumatic, pseudoexfoliation) glaucoma were present. Bilateral blindness (vision <3/60) and severe visual impairment (<6/60) were found in four (6%) and three (4.5%) subjects with glaucoma, respectively. Glaucoma was treated in 36 (54%) subjects.

Conclusions:

The prevalence of glaucoma among citizens of Qatar aged 40 years and older was 1.71%. Glaucoma was associated with the age of 60 years and older and the presence of myopia.

Incidence of cilioretinal arteries in Chinese Han population

AIM

To estimate the incidence of cilioretinal arteries among Han population of north China.

METHODS

A cross-sectional sample of subjects aged from 20 years old to 80 years old were selected using a cluster sampling technique from Shenyang of Liaoning Province for Diabetic Eye Disease Study. Eligible subjects were recruited in the Community Health Center which took the stereo fundus photography using 45°Non-Mydriatic Fundus Camera. Data were analyzed by SPSS 14.0.

RESULTS

The incidence of cilioretinal arteries in 5000 eyes of 2500 subjects was determined. One, two or more cilioretinal arteries were present in 876 of all subjects and in 923 of all the eyes. Difference of presence, number and distribution of cilioretinal arteries was observed. During the subjects, the arteries occurred bilaterally in 6.9% and contributed to some portion of the temporal circulation in 78.3%, nasal circulation 14.8%, respectively. Statistical analysis indicated that there was no significant difference in incidence between men and women, left and right eyes (P>0.05).

CONCLUSION

35.0% persons have the cilioretinal arteries in Han population of north China. Men and women have an equal distribution of cilioretinal arteries.

[Ophthalmic disease in diabetes mellitus: management from primary health care]

OBJECTIVE

To study the feasibility of a basic ophthalmological examination for the eye disease in diabetic patients by Primary Health Care (PHC).

PATIENTS AND METHODS

A multi-centre prospective study. A sample of 712 type 2 diabetics.

INTERVENTIONS

Visual acuity examination, intraocular pressure measurement and the eye fundus photograph with a non-mydriatic camera taken by an optometrist. The interpretation and subsequent referral to an ophthalmology department by ophthalmologists and general practitioners (GP).

RESULTS

Visual acuity deficiency: GP, 43.7%; ophthalmologist, 36.1%; concordance, 70%; glaucoma suspicion: GP, 8.8%; ophthalmologist, 7.6%; concordance, 94%; diabetic retinopathy: GP, 28.2%; ophthalmologist, 13.4%; concordance, 78%. Ophthalmology Department referral: GP, 56.8%; ophthalmologist, 41.3% (P=0.001).

CONCLUSIONS

Agreement between GP and ophthalmologist leads to a reliable ophthalmological examination of the diabetic patient in PHC. Despite an over-diagnosis and 16% of non-justified referrals by the GP, Ophthalmology Department referral is avoided in almost half of the diabetic patients.

Quantitative depth analysis of optic nerve head using stereo retinal fundus image pair

Depth analysis of the optic nerve head (ONH) in the retinal fundus is important for the early detection of glaucoma. In this study, we investigate an automatic reconstruction method for the quantitative depth measurement of the ONH from a stereo retinal fundus image pair. We propose a technique to obtain the depth value from the stereo retinal fundus image pair, which mainly consists of five steps: 1. cutout of the ONH region from the stereo retinal fundus image pair, 2. registration of the stereo image pair, 3. disparity measurement, 4. noise reduction, and 5. quantitative depth calculation. Depth measurements of 12 normal eyes are performed using the stereo fundus camera and the Heidelberg Retina Tomograph (HRT), which is a confocal laser-scanning microscope. The depth values of the ONH obtained from the stereo retinal fundus image pair were in good accordance with the value obtained using HRT (r=0.80+/-0.15). These results indicate that our proposed method could be a useful and easy-to-handle tool for assessing the cup depth of the ONH in routine diagnosis as well as in glaucoma screening.

Comparing optic nerve-head-size measurements by the heidelberg retina tomograph with fundus photography performed with a novel focusing technique

PURPOSE

To compare disc areas as measured with the Heidelberg Retina Tomograph (HRT) to those obtained with a fundus camera.

DESIGN

A nonrandomized comparative trial.

PARTICIPANTS

Forty-six patients (88 eyes) who were participating in a glaucoma-screening study.

METHODS

Disc areas from fundus photographs taken with a Nidek nonmydriatic camera were measured in pixels (Adobe photoshop 7.0). A magnification factor was determined, using a previously described technique that uses the position of the focusing slide on the camera to account for the spherical refractive error. The resulting calculated disc areas were then compared with the disc areas as measured with the HRT.

MAIN OUTCOME MEASURES

Disc area.

RESULTS

The limits of agreement between the 2 techniques were 0.49 and -0.51 mm2, indicating that the range of differences between these imaging techniques was approximately 1 mm2. Using a Bland-Altman plot, the distribution of residuals indicated that the 2 techniques do not differ in a systematic way.

CONCLUSIONS

Disc area measurements can be reasonably determined from digital fundus photography if corrected for focusing slide position when compared with HRT. This may have useful applications for both clinical glaucoma patient care and population-based glaucoma-screening programs.

The papilla as screening parameter for early diagnosis of glaucoma

INTRODUCTION

In the industrialized countries 67 million people suffer from glaucoma, which represents the third most common cause of blindness and thus has a high economic impact. Early diagnosis of glaucoma, which does not necessarily involve raised intraocular pressure, is essential because by the time the patient notices functional impairment the damage is irreversible. Early treatment can decrease the rate of blindness 20 years later by about 50%.

METHODS

Selective literature review and clinical investigation of early glaucoma detection and of screening methods.

RESULTS

Currently, no evidence-based recommendations for glaucoma screening can be found in the literature. No single method or combination of screening procedures can be recommended unambiguously on economic grounds.

DISCUSSION

From the clinical perspective sensitive, specific, and cost-effective glaucoma screening seems feasible. The high-risk group would need to be defined on the basis of age and family history. A two-stage screening process would then have to be established with initial computer-supported telemedical sorting followed by telemedical ophthalmological diagnosis of cases selected for clarification.

A pilot study to detect glaucoma with confocal scanning laser ophthalmoscopy compared with nonmydriatic stereoscopic photography in a community health screening

PURPOSE

To assess the efficacy and practical usefulness of the Heidelberg Retina Tomograph II (HRT II) compared with nonmydriatic stereoscopic photography in a public glaucoma screening.

METHODS

We examined 1173 local residents, aged 40 years or older, who visited a community health screening in Komatsu City. Initial glaucoma screening consisted of noncontact pneumotonometry, nonmydriatic stereoscopic fundus photography, and HRT II. When glaucoma was suspected, the subjects were referred for a definitive examination, in which slit-lamp biomicroscopic examination, Goldmann applanation tonometry, Humphrey 30-2 test, gonioscopy, and optic nerve head evaluation were performed.

RESULTS

A total of 97.2% (2279/2345) of the nonmydriatic stereoscopic optic disc photographs could be interpreted and 93.4% (2189/2345) were good images. HRT II measurements were successful in 99.0% (2322/2345) of eyes, and acceptable images were obtained in 91.9% (2154/2345) of eyes. On the basis of clinical diagnoses, 94 eyes of 60 participants were diagnosed with glaucoma. The sensitivity of nonmydriatic stereoscopic photographs for personal-level analysis and eye-level analysis was 95.8% and 95.5%, respectively. Using Moorfield's regression analysis, HRT sensitivity and specificity were 72.3% to 91.5% and 84.0% to 93.1%, respectively, for personal-level analysis, and 60.3% to 72.6% and 89.7% to 95.6%, respectively, for eye-level analysis.

CONCLUSION

Although HRT II did not detect glaucoma as well as optic nerve stereophotographs in this Japanese population, it may play a role in community health screening.

Accuracy of combined GDx-VCC and matrix FDT in a glaucoma screening trial

PURPOSE

To assess the advantage in glaucoma screening of the use of scanning laser polarimetry with customized cornea compensation (GDx-VCC) combined with Matrix Frequency Doubling Technology (M-FDT) testing.

METHODS

In a nonpopulation-based prepublicized trial, self-recruited white participants were screened for glaucoma with GDx-VCC, with M-FDT, and by independent clinical examination. Cases with possible glaucoma as found with any of the screening methods underwent a detailed clinical investigation to verify or exclude glaucoma. Sensitivity, specificity, accuracy, likelihood ratios, and predictive values were calculated using different threshold criteria for GDx-VCC alone, M-FDT alone, and for various combinations.

RESULTS

Of the 233 attendees, 181 participants (345 eyes) successfully underwent the GDx-VCC and M-FDT measurements. Thirty-nine eyes of 24 participants had glaucoma (11.3% prevalence among eyes tested successfully). All but 2 of the glaucomatous eyes had only early damage. Evaluated separately, the criterion GDx-VCC NFI (normal threshold < or =30) performed best, with 97.0% specificity, 88.8% accuracy, and 25.6% sensitivity; but with only 8.5 positive likelihood ratio (PLR). For paired criteria, the best combination of GDx-VCC-screening test with M-FDT-screening test provided 99.6% specificity, 91.3% accuracy, and 28.6 PLR. For NFI combined with GDx-VCC nerve fiber bundle defect criterion, specificity was 99.0%, accuracy 89.6%, and PLR 18.0. However, the sensitivities in the 2 cases fell to 12.0% and 18.0%. For a triple combination of M-FDT-screening test with the latter pair of criteria, sensitivity increased to 41.7% and PLR (13.6) still remained clinically useful.

CONCLUSIONS

In a self-recruited white population with relatively high risk for mild glaucomatous damage, a combination of GDx-VCC together with M-FDT could usefully be employed for mass glaucoma screening.

[Usefulness of a glaucoma and ocular hypertension screening strategy in primary care]

OBJECTIVES

To evaluate the usefulness of a glaucoma and intraocular hypertension screening strategy for new cases detected. To evaluate the acceptability of taking intra-ocular pressure (IOP) and the appearance of side effects.

DESIGN

Cross-sectional, descriptive study.

SETTING

An urban health centre and the ophthalmology clinic of its main hospital.

PARTICIPANTS

A total of 2044 patients aged over 40, 63.5% women and 36.5% men, with a mean age of 61.23 (SD, 11.42). They were selected by consecutive sampling from patients who visited the health centre over a 9-month period. Subjects diagnosed with glaucoma, ocular hypertension (OH), conjunctivitis, or corneal pathology were excluded.

INTERVENTIONS

Taking of IOP with Tonopen XL in primary care. Subjects with IOP > or = 21 mm Hg were referred to ophthalmology. In these patients, IOP was measured with Goldmann, and patients with confirmed OH received ophthalmoscopy and campimetry.

MAIN MEASUREMENTS

Percentage of subjects with glaucoma, suspected glaucoma, and OH confirmed in ophthalmology. Positive predictive value (PPV) for OH.

RESULTS

One hundred subjects with OH were detected (4.89%; 95% CI, 3.93%-5.85%), of whom 21 were diagnosed with glaucoma (1.04%; 95% CI, 0.57-1.49) and 10 with suspected glaucoma (0.49%; 95% CI, 0.16-0.82). The PPV for OH was 44.27%. The acceptability of the test was 98.09%. No patients presented with side-effects following the taking of their IOP.

CONCLUSIONS

The strategy evaluated is useful in terms of the number of subjects with glaucoma and OH detected. The acceptability of taking IOP with Tonopen XL was high.

Screening for glaucoma in Canada: a systematic review of the literature

BACKGROUND

To provide a recommendation on screening for glaucoma in Canada based on a review of recent evidence available in the literature.

METHODS

A systematic literature review was performed to identify publications from MEDLINE, EMBASE, HealthSTAR, and Cochrane databases from 1990 to 2005. Relevant articles were categorized as economic studies, epidemiologic and intervention studies, or policy papers. Web sites and publications from provincial, state, national, and international health authorities were reviewed for policy recommendations and guidelines.

RESULTS

We identified 39 articles (34 epidemiology and intervention, and 5 economic studies) for the review. From the economic studies, 2 were simple cost analyses and 3 were full economic evaluations (cost-effectiveness). Gaps were observed from these economic studies, where incremental cost-effectiveness analyses of modelled screening programmes were not observed. A large number of alternatives (i.e., screening techniques) and diverse outcome measures were found in the 34 epidemiology and intervention studies. This shows that evidence on the effectiveness of glaucoma screening programmes is available to be used in future modelled analyses. Neutral recommendation made by the Canadian Task Force on Periodic Health Examination regarding glaucoma screening in Canada could be related to the lack of reliable data and models used in past cost-effectiveness analyses.

INTERPRETATION

A need exists to reevaluate the cost-effectiveness of a screening programme for glaucoma in Canada with updated efficacy and cost data. Health and monetary benefits could be improved compared with current practice and decision-makers would have the best available data when reevaluating the policy on screening for glaucoma.

Evaluation of Screening versus Regular Polarimetry

PURPOSE

The purpose of this study is to evaluate a new screening program for the GDx VCC (variable corneal compensation) retinal nerve fiber layer analyzer. This new method uses a fast screening approach to detect retinal nerve fiber layer loss associated with glaucoma. The study evaluates the sensitivity and specificity of the screening program and compares the results with those from the GDx VCC full examination.

METHODS

One hundred seventeen eyes from 60 subjects with a mean age of 60.65 years (range, 41-79 years old) were analyzed. Subjects were divided into a normal or glaucoma group based on an ophthalmic examination. Each individual underwent a GDx VCC screening examination, GDx full examination, Humphrey HFA II 24-2 SITA Standard visual field, intraocular pressure assessment, and dilated optic nerve examination. The outcome for the GDx screening examination was within normal limits, borderline, or outside normal limits and compared with the GDx full examination results.

RESULTS

The sensitivity and specificity for the GDx full examination were 73% and 79%, respectively. The sensitivity and specificity for the screening method were 67% and 91%, respectively. The full examination was more sensitive; however, the screening examination was more specific.

CONCLUSION

The screening examination is more conservative than the full examination algorithm and may miss some individuals with glaucomatous damage that the full examination may identify. However, the number of false-positives for the screening examination is less than the full examination method.

Glaucoma screening: current trends, economic issues, technology, and challenges

PURPOSE OF REVIEW

Glaucoma is one of the leading causes of irreversible blindness worldwide. Early glaucoma detection and treatment are currently the only known methods for preventing blindness and low vision resulting from this frequently asymptomatic disease.

RECENT FINDINGS

New technologies for detecting early glaucomatous damage are important in diagnosing optic nerve disease, not only in community screening settings but also in clinics. Imaging of the optic nerve head and macula and retinal nerve fiber layer analysis can provide quick, automated, and quantitative measurements in agreement with clinical estimates of optic disc structure and visual function. In the area of perimetry, frequency-doubling technology is a promising and feasible mass-screening method with reasonable sensitivity for detecting visual field loss. Central corneal thickness has emerged as a new risk factor for the development and progression of glaucoma, thereby complicating the role of tonometry and measurement of intraocular pressure as screening parameters for glaucoma. Along with technological advances, strides are also being made with public policy and legislative efforts to bring glaucoma onto the national and global health care agenda. These initiatives incorporate vision-screening goals into national disease prevention programs emphasizing the need for early glaucoma detection and treatment.

SUMMARY

Glaucoma awareness needs to be increased through better education, and compliance with follow-up care needs to be improved to decrease the economic and social costs from glaucoma. In addition, screening models need to be developed that will be effective in developing countries where the risk of blindness from glaucoma is highest.