Prevent Blindness America visual field screening study. The Prevent Blindness America Glaucoma Advisory Committee

Long-term Outcomes in Patients Undergoing Surgery for Primary Congenital Glaucoma between 1991 and 2000: A Single-Center Database Study

PURPOSE

To estimate the long-term surgical and visual outcomes in patients with primary congenital glaucoma (PCG) who completed at least 20 years of follow-up.

DESIGN

Retrospective study.

PARTICIPANTS

Two hundred twenty eyes of 121 patients undergoing surgery for PCG between January 1991 and December 2000 and who returned for a follow-up visit from January 2021 through January 2022.

METHODS

Retrospective review of medical records of patients who underwent primary combined trabeculotomy-trabeculectomy (CTT) without mitomycin C as an initial procedure. Success was defined as complete when intraocular pressure (IOP) was ≥ 6 mmHg and ≤ 21 mmHg without glaucoma medication and as qualified when up to 2 glaucoma medications were required. Failure was defined as uncontrolled IOP with more than 2 glaucoma medications, need for a second IOP-lowering procedure, chronic hypotony (IOP < 6 mmHg on 2 consecutive visits), or any sight-threatening complication. A mixed-effects model using maximum likelihood estimation was used in estimation of eye-based variables and to make comparisons between different visits. Kaplan-Meier survival analysis was used to estimate the probabilities of surgical and functional successes. Cox proportional hazards regression using sandwich clustered estimation was used to evaluate risk factors for failure and poor visual outcome.

MAIN OUTCOME MEASURES

Primary outcome measure was the proportion of patients who demonstrated complete success over the 20-year follow-up. Secondary outcome measures included rate of surgical failure and need for reoperation for glaucoma, visual acuity, refractive errors, risk factors for poor outcome, and complications.

RESULTS

Kaplan-Meier survival analysis revealed 1-year, 10-year, and 20-year complete success rates of 90.7%, 78.9%, and 44.5%, respectively. In univariate analysis, surgical failure was higher among patients with any additional non-glaucoma intraocular surgery. None of the clinical parameters were associated significantly with failure in multivariable analysis. Overall, the proportion of eyes with good, fair, and poor visual outcomes was 33.2%, 16.4%, and 50.4%, respectively. Myopia was seen in 68.9% eyes. Twenty-eight eyes of those who underwent primary CTT (14.4%) required second surgery for IOP control. No significant intraoperative complications occurred. Six eyes required enucleation because of painful blind eye.

CONCLUSIONS

In this large cohort of patients with PCG, CTT is a useful procedure. It provides good IOP control and moderate visual recovery that remained over a 20-year follow-up after surgery.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

A generalizable deep learning regression model for automated glaucoma screening from fundus images

A plethora of classification models for the detection of glaucoma from fundus images have been proposed in recent years. Often trained with data from a single glaucoma clinic, they report impressive performance on internal test sets, but tend to struggle in generalizing to external sets. This performance drop can be attributed to data shifts in glaucoma prevalence, fundus camera, and the definition of glaucoma ground truth. In this study, we confirm that a previously described regression network for glaucoma referral (G-RISK) obtains excellent results in a variety of challenging settings. Thirteen different data sources of labeled fundus images were utilized. The data sources include two large population cohorts (Australian Blue Mountains Eye Study, BMES and German Gutenberg Health Study, GHS) and 11 publicly available datasets (AIROGS, ORIGA, REFUGE1, LAG, ODIR, REFUGE2, GAMMA, RIM-ONEr3, RIM-ONE DL, ACRIMA, PAPILA). To minimize data shifts in input data, a standardized image processing strategy was developed to obtain 30° disc-centered images from the original data. A total of 149,455 images were included for model testing. Area under the receiver operating characteristic curve (AUC) for BMES and GHS population cohorts were at 0.976 [95% CI: 0.967-0.986] and 0.984 [95% CI: 0.980-0.991] on participant level, respectively. At a fixed specificity of 95%, sensitivities were at 87.3% and 90.3%, respectively, surpassing the minimum criteria of 85% sensitivity recommended by Prevent Blindness America. AUC values on the eleven publicly available data sets ranged from 0.854 to 0.988. These results confirm the excellent generalizability of a glaucoma risk regression model trained with homogeneous data from a single tertiary referral center. Further validation using prospective cohort studies is warranted.

Screening for Glaucomatous Visual Field Defects in Rural Australia with an iPad

Aim and objective

Developing improved methods for early detection of visual field defects is pivotal to reducing glaucoma-related vision loss. The Melbourne Rapid Fields screening module (MRF-S) is an iPad-based test, which allows suprathreshold screening with zone-based analysis to rapidly assess the risk of manifest glaucoma. The versatility of MRF-S has potential utility in rural areas and during infectious pandemics. This study evaluates the utility of MRF-S for detecting field defects in non-metropolitan settings.

Materials and methods

This was a prospective, multicenter, cross-sectional validation study. Two hundred and fifty-two eyes of 142 participants were recruited from rural sites through two outreach eye services in Australia. Participants were tested using MRF-S and compared with a reference standard; either Zeiss Humphrey Field Analyzer or Haag-Streit Octopus performed at the same visit. Standardized questionnaires were used to assess user acceptability. Major outcome measures were the area under the curve (AUC) for detecting mild and moderate field defects defined by the reference tests, along with corresponding performance characteristics (sensitivity, specificity).

Results

The mean test duration for MRF-S was 1.88 minutes compared with 5.92 minutes for reference tests. The AUCs for mild and moderate field defects were 0.81 [95% confidence interval (CI): 0.75–0.87] and 0.87 (95% CI: 0.83–0.92), respectively, indicating very good diagnostic accuracy. Using a risk criterion of 55%, MRF-S identified moderate field defects with a sensitivity and specificity of 88.4 and 81.0%, respectively.

Conclusion and clinical significance

The MRF-S iPad module can identify patients with mild and moderate field defects while delivering favorable user acceptability and short test duration. This has potential application within rural locations and amidst infectious pandemics.

How to cite this article

Chia MA, Trang E, Agar A, et al. Screening for Glaucomatous Visual Field Defects in Rural Australia with an iPad. J Curr Glaucoma Pract 2021;15(3):125–131.

Combined structure-function analysis in glaucoma screening

AIM

To assess the applicability of a structure-function (S-F) analysis combining spectral-domain optical coherence tomography (SD-OCT) and standard automated perimetry (SAP) in glaucoma screening in a middle-aged population.

METHODS

A randomised sample of 3001 Caucasian participants aged 45-49 years of the Northern Finland Birth Cohort Eye Study was examined. We performed an eye examination, including 24-2 SAP, optic nerve head (ONH) and retinal nerve fibre layer (RNFL) photography and SD-OCT of the peripapillary RNFL. The S-F report was generated by Forum Glaucoma Workplace software. OCT, SAP and the S-F analysis were evaluated against clinical glaucoma diagnosis, that is, the positive '2 out of 3' rule based on the clinician's evaluation of ONH and RNFL photographs and visual fields (VFs).

RESULTS

At a specificity of 97.5%, the sensitivity for glaucomatous damage was 26% for abnormal OCT, 35% for SAP and 44% for S-F analysis. Estimated areas under the curve were 0.74, 0.85 and 0.76, and the corresponding positive predictive values were 8 %, 10% and 12%, respectively. By applying a classification tree approach combining OCT, SAP and defect localisation data, a sensitivity of 77% was achieved at 90% specificity. In a localisation analysis of glaucomatous structural and functional defects, the correlation with glaucoma increased significantly if the abnormal VF test points were located on borderline or abnormal OCT zones.

CONCLUSION

SAP performs slightly better than OCT in glaucoma screening of middle-aged population. However, the diagnostic capability can be improved by S-F analysis.

Structural Analysis of Glaucoma Brain and its Association With Ocular Parameters

PRECIS

Glaucoma patients presented a decreased occipital pole surface area in both hemispheres. Moreover, these parameters are independently correlated with functional and structural ocular parameters.

PURPOSE

The purpose of this study was to evaluate structural brain abnormalities in glaucoma patients using 3-Tesla magnetic resonance imaging and assess their correlation with associated structural and functional ocular findings.

PATIENTS AND METHODS

This cross-sectional prospective study included 30 glaucoma patients and 18 healthy volunteers. All participants underwent standard automated perimetry, spectral-domain optical coherence tomography, and 3.0-Tesla magnetic resonance imaging.

RESULTS

There was a significant difference between the surface area of the occipital pole in the left hemisphere of glaucoma patients (mean: 1253.9±149.3 mm) and that of control subjects (mean: 1341.9±129.8 mm), P=0.043. There was also a significant difference between the surface area of the occipital pole in the right hemisphere of glaucoma patients (mean: 1910.5±309.4 mm) and that of control subjects (mean: 2089.1±164.2 mm), P=0.029. There was no significant difference between the lingual, calcarine, superior frontal, and inferior frontal gyri of glaucoma patients and those of the control subjects (P>0.05 for all comparisons). The surface area of the occipital pole in the left hemisphere was significantly correlated with perimetry mean deviation values, visual acuity, age, and retinal nerve fiber layer thickness (P=0.001, <0.001, 0.010, and 0.006, respectively). The surface area of the occipital pole in the right hemisphere was significantly correlated with perimetry mean deviation values, visual field indices, visual acuity, age, and retinal nerve fiber layer thickness (P<0.001, 0.007, <0.001, 0.046, and <0.001, respectively).

CONCLUSION

Glaucoma patients presented a decreased occipital pole surface area in both hemispheres that independently correlated with functional and structural ocular parameters.

Detection of visual field defects by opticians - with Damato Multifixation Campimetry Online

PURPOSE

To study Damato Multifixation Campimetry Online (DMCO), an inexpensive online visual field test, used for screening at optician shops in Denmark.

METHODS

This was an evaluation of a diagnostic test and customers were included if minimum 50 years old, with a visual acuity of minimum 0.5 and with less myopia than 6 D. Standard equipment was a computer, a wireless mouse and a computer monitor. We used the 'DMCO STANDARD 4,5' algorithm for screening. DMCO results were electronically transmitted to the authors. Customers with a positive DMCO test received an eye examination including the reference standard Humphrey Visual Field Analyzer 30-2 SITA Fast test. A subset of control participants with a negative DMCO test received the same examination in order to estimate the number of false and true negatives. DMCO specificity and sensitivity were estimated according to five reference standards with 95% confidence intervals.

RESULTS

The population comprised 627 individuals, 381 women and 246 men, from 13 optician shops. Mean age was 62 years (SD 7.4). DMCO was positive in 32 individuals and 27 individuals were classified as 'true positives' with diagnoses such as glaucoma, cataract and neurological visual field defects. Of the 595 individuals with a negative DMCO test, 110 were examined and nine individuals were classified as 'false negatives' according to diagnoses. Depending on reference the specificity was 97-99% and sensitivity was 14-69%.

CONCLUSION

Screening with DMCO demonstrated high specificity, whereas sensitivity was unsatisfactory. Future studies with enough power to estimate the true sensitivity is needed.

Pattern Electroretinography and Visual Evoked Potentials Provide Clinical Evidence of CNS Modulation of High- and Low-Contrast VEP Latency in Glaucoma

Purpose

Both pattern electroretinography (PERG) and visual evoked potentials (VEP) can be performed using low- (15%; Lc) and high- (85%; Hc) contrast gratings that may preferentially stimulate the magno- and parvocellular pathways. We observed that among glaucomatous patients showing only one VEP latency deficit per eye, there appeared to be a very strong tendency for an Hc delay in one eye and an Lc delay in the other.

Methods

Diopsys NOVA-LX system was used to measure VEP Hc and Lc latency among a clinical glaucoma population to find all individuals with either a single Hc or Lc latency abnormality in each eye (group 1), or with greater than 0 and less than 4 Hc or Lc VEP latency abnormalities in the two eyes (group 2) to determine whether a significant inverse correlation existed for these values in either group. Hc and Lc PERG data were also evaluated to assess associated retinal ganglion cell responses.

Results

A strong inverse correlation (P = 0.0000003) was observed between the Hc and Lc VEP latency values among the 64 eyes in group 1. Group 2 provided a comparable result (n = 143; 286 eyes; P = 0.0005). PERG (n = 81; 162 eyes) also showed strong bilateral symmetry for magnitude values (P < 0.0001 for both Lc and Hc in groups 1 and 2).

Conclusions

Bilateral retention of both low-resolution/high-speed and high-resolution/low-speed function may persist with both eyes open despite symmetrically pathologic retinal ganglion cell PERG waveform asynchrony for Hc and Lc stimuli in the paired eyes.

Translational Relevance

Clinical electrophysiology strongly suggests binocular compensation for dynamic dysfunction operates under central nervous system (CNS) control in glaucoma.

Comparison of isolated-check visual evoked potential and standard automated perimetry in early glaucoma and high-risk ocular hypertension

AIM

To compare the diagnostic performance of isolated-check visual evoked potential (icVEP) and standard automated perimetry (SAP), for evaluating the application values of icVEP in the detection of early glaucoma.

METHODS

Totally 144 subjects (288 eyes) were enrolled in this study. icVEP testing was performed with the Neucodia visual electrophysiological diagnostic system. A 15% positive-contrast (bright) condition pattern was used in this device to differentiate between glaucoma patients and healthy control subjects. Signal-to-noise ratios (SNR) were derived based on a multivariate statistic. The eyes were judged as abnormal if the test yielded an SNR≤1. SAP testing was performed with the Humphrey Field Analyzer II. The visual fields were deemed as abnormality if the glaucoma hemifield test results outside normal limits; or the pattern standard deviation with P<0.05; or the cluster of three or more non-edge points on the pattern deviation plot in a single hemifield with P<0.05, one of which must have a P<0.01. Disc photographs were graded as either glaucomatous optic neuropathy or normal by two experts who were masked to all other patient information. Moorfields regression analysis (MRA) used as a separate diagnostic classification was performed by Heidelberg retina tomograph (HRT).

RESULTS

When the disc photograph grader was used as diagnostic standard, the sensitivity for SAP and icVEP was 32.3% and 38.5% respectively and specificity was 82.3% and 77.8% respectively. When the MRA Classifier was used as the diagnostic standard, the sensitivity for SAP and icVEP was 48.6% and 51.4% respectively and specificity was 84.1% and 78.0% respectively. When the combined structural assessment was used as the diagnostic standard, the sensitivity for SAP and icVEP was 59.2% and 53.1% respectively and specificity was 84.2% and 84.6% respectivlely. There was no statistical significance between the sensitivity or specificity of SAP and icVEP, regardless of which diagnostic standard was based on.

CONCLUSION

The diagnostic performance of icVEP is not better than that of SAP in the detection of early glaucoma.

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.

Refined Frequency Doubling Perimetry Analysis Reaffirms Central Nervous System Control of Chronic Glaucomatous Neurodegeneration

PURPOSE

Refined analysis of frequency doubling perimetric data was performed to assess binocular visual field conservation in patients with comparable degrees of bilateral glaucomatous damage, to determine whether unilateral visual field loss is random, anatomically symmetric, or non-random in relation to the fellow eye.

METHODS

Case control study of 41 consecutive patients with bilaterally mild to severe glaucoma; each right eye visual field locus was paired with randomly-selected co-isopteric left eye loci, performing 690,000 (10,000 complete sets of 69 loci) such iterations per subject. The potential role of anatomic symmetry in bilateral visual field conservation was also assessed by pairing mirror-image loci of the right- and left-eye fields. The mean values of the random co-isopteric and the symmetric mirror pairings were compared with natural point-for-point pairings of the two eyes by paired t-test.

RESULTS

Mean unilateral Matrix threshold across the entire 30-degree visual field were 17.0 dB left and 18.4 dB right (average 17.7). The better of the naturally paired concomitant loci yielded binocular equivalent mean bilateral Matrix threshold of 20.9 dB, 1.6 dB higher than the population mean of the 690,000 coisopteric pairings (t = -10.4; P < 10^-12). Thus, a remarkable natural tendency for conservation of the binocular Matrix visual field was confirmed, far stronger than explicable by random chance. Symmetric pairings of precise mirror-image loci also produced values higher than random co-isopteric pairings (Δ 1.1 dB; t = -4.0; P = 0.0004).

CONCLUSIONS

Refined data analysis of paired Matrix visual fields confirms the existence of a natural optimization of binocular visual function in severe bilateral glaucoma via interlocking fields that could only be created by CNS involvement. The disparity of paired Matrix threshold values at mirror-image loci was also highly nonrandom and quantitatively inverse from the expected if anatomic symmetry factors were merely passively contributing systematically to the compensatory binocular Matrix effect.

TRANSLATIONAL RELEVANCE

The paired eyes and brain are reaffirmed to function as a unified system in the progressive age-related neurodegenerative condition chronic open angle glaucoma, maximizing the binocular visual field. Given the extensive homology of this disorder with other age-related neurodegenerations, it is reasonable to assume that the brain will similarly resist simultaneous bilateral loss of paired functional zones in both hemispheres in diseases like Alzheimer's and Parkinson's disease. Glaucomatous eyes at all stages of the disease appear to provide a highly accessible paired-organ study model for developing therapeutics to optimize conservation of function in neurodegenerative disorders.

Effects of travoprost eye drops on intraocular pressure and pulsatile ocular blood flow: a 180-day, randomized, double-masked comparison with latanoprost eye drops in patients with open-angle glaucoma

BACKGROUND

Because of the increasing realization of the importance of optic nerve head perfusion in the pathogenesis of glaucoma, the influence of new antiglaucomatous drugs on ocular hemodynamic properties should be investigated.

OBJECTIVE

The aim of this study was to compare the effects of 2 prostaglandin analogues, travoprost eye drops and latanoprost eye drops, on intraocular pressure (IOP) and pulsatile ocular blood flow (pOBF) in patients with primary open-angle glaucoma (POAG).

METHODS

Previously untreated patients aged 40 to 60 years with POAG and normal brachial blood pressure (BBP), heart rate, body mass index, and hemorheologic findings were eligible for this randomized, double-masked study. Two drops of travoprost (group T) or latanoprost (group L) were self-administered in both eyes at 9:00 pm. In all patients, IOP, pOBF, BBP, and heart rate were measured at baseline and on days 15, 30, 60, 90, and 180 of treatment.

RESULTS

Twenty-five consecutive patients with POAG were enrolled in this study conducted at the Glaucoma Research Center of the Department of Ophthalmology, Bari University, Policlinico di Bari (Bari, Italy). Of these, 7 were withdrawn because they did not return for the second appointment, leaving 18 patients (11 men, 7 women; mean [SD] age, 51.9 [5.5] years) to complete the study. In both groups, mean IOP values were significantly reduced at all time points compared with baseline (all P<0.01). Mean pOBF values increased ∼50% from baseline following treatment with either travoprost or latanoprost by day 15, were maintained at that level for 60 days, and then gradually decreased (group T: P = NS, NS, <0.01, <0.05, and <0.05 at days 15, 30, 60, 90, and 180, respectively, vs baseline; group L: P<0.01 at all time points vs baseline). All other parameters remained constant throughout the study. An early inverse correlation between IOP and pOBF was noted in group T but not in group L. No significant differences were found between groups in IOP or pOBF at any time point.

CONCLUSIONS

In this study population, pOBF was increased with travoprost and latanoprost in the short term, but this effect was kept constant only with travoprost. IOP was reduced with both drugs after short-term therapy, and this reduction was maintained in both groups. Travoprost may represent another option for the medical treatment of POAG.

Refined Data Analysis Provides Clinical Evidence for Central Nervous System Control of Chronic Glaucomatous Neurodegeneration

PURPOSE

Refined data analysis was performed to assess binocular visual field conservation in patients with bilateral glaucomatous damage to determine whether unilateral visual field loss is random, anatomically symmetric, or nonrandom in relation to the fellow eye.

METHODS

This was a case-control study of 47 consecutive patients with bilaterally severe glaucoma; each right eye visual field locus was paired with randomly selected coisopteric left eye loci, with 760,000 (10,000 complete sets of 76 loci) such iterations performed per subject. The potential role of anatomic symmetry in bilateral visual field conservation was also assessed by pairing mirror-image loci of the paired fields. The mean values of the random coisopteric and the symmetric mirror pairings were compared with natural point-for-point pairings of the two eyes by paired t-test.

RESULTS

Mean unilateral thresholds across the entire visual field were 18.9 dB left and 19.9 dB right (average 19.4), 4 dB lower than the better of the naturally paired concomitant loci of 23.4 dB (P < 10^-15). A remarkable natural tendency for conservation of the binocular visual field was confirmed, far stronger than explicable by random chance or anatomic symmetry (P < 0.0001), and reaffirmed by subsequent prospective simultaneous binocular visual field retesting of an arbitrary subset (n = 16) of the study population (P < 0.0001).

CONCLUSIONS

Refined data analysis of paired visual fields confirms the existence of a natural optimization of binocular visual function in severe bilateral glaucoma via interlocking fields that could be created only by central nervous system (CNS) involvement.

TRANSLATIONAL RELEVANCE

Integrated bilateral visual field analysis should better define actual visual disability and more accurately reflect the functional efficacy of current ocular and future CNS-oriented therapeutic approaches to the treatment of glaucoma. Glaucomatous eyes provide a highly accessible paired-organ study model for developing therapeutics to optimize conservation of function in neurodegenerative disorders.

Visual field screening with a laptop computer system

BACKGROUND

The aim of this study was to develop a visual field screening system and investigate the importance of using 2 different programs for visual field screening to be used in places in which other perimeters are yet not available. The system consists of a laptop computer with instructions for the patient displayed on the screen and additional equipment to ensure central eye position, eye distance to the screen, optimal optical correction, and light intensity. This visual field screening system combines a screening program consisting of 68 test points with the highest density in areas of high prevalence of visual defects, followed by a supplementary program comprising 82 other test points in a quadratic lattice pattern.

METHODS

The system was compared with Octopus 1-2-3 threshold perimetry, and the applicability of the system when operated by optometrists was evaluated.

RESULTS

In the glaucoma clinic at the University Hospital, Rigshospitalet, Denmark, the screening program was used to investigate 98 patients (173 eyes) and to compare the results with those of the Octopus Perimetry Program dG2. The sensitivity of the system was 100% and the specificity was 78%. Subsequently, 18 optometrists in different locations in Denmark tested 1,022 patients (2,036 eyes). Patients contacted these optometrists because of the presence of refractive error, subjective vision problems, or eye symptoms. The screening was used as a part of a routine examination. In 432 eyes (21%), visual defects were detected using the screening program. By re-examining 349 eyes, with the addition of the supplementary program consisting of 82 other test points in a quadratic lattice pattern, the visual field defects were not reproduced in 263 eyes, a reduction of primary positive visual field defects by 75%. The additional supplementary program was not conducted with 38 eyes (2%) because of large visual field defects, high intraocular pressures, cataract, positive family history of glaucoma, lack of time, or poor patient cooperation. In 56 eyes (3%) examined with the additional supplementary program, the defects found in the screening program were reproduced. In total, 59 (5.8%) patients (38 + 56 eyes) were recommended to pursue an ophthalmologic eye examination by a local ophthalmologist.

CONCLUSION

Confrontation visual field testing in many places is the only method used for examining the visual field. A laptop computer system for visual field screening could be a better method for visual field screening in the primary eye care setting. For clinical relevance, it is necessary to perform the method with 2 different screening programs. The method can be useful as an important part of a routine examination and for directing further examinations.

Cost-effectiveness of glaucoma interventions in Barbados and Ghana

PURPOSE

More than 90% of blindness worldwide exists in the developing world, but information on the social and economic burden and the cost-effectiveness of treatment in these settings is often limited or nonexistent. We demonstrate the use of computer modeling to simulate the current and future epidemiology, outcomes, and treatment of primary open-angle glaucoma in high-incidence populations of the developing world.

METHODS

A previously validated vision model was modified to simulate the incidence progression and social and economic outcomes of glaucoma in Barbados, which was the source of epidemiology data, and Ghana, which has similar propensity for glaucoma but lower socioeconomic development. We then assessed the cost-effectiveness of hypothetical case-finding and treatment scenarios, including U.S. guideline-level care and one-time laser surgery.

RESULTS

Barbados incurs relatively greater social and economic burden from glaucoma than Ghana. In Barbados, population screening followed by U.S. guideline levels of care appears to be highly cost-effective. Because of a younger population with higher mortality at younger ages, glaucoma appears to cause less visual impairment and blindness in Ghana than in Barbados, resulting in lower per capita disability and productivity losses. Population screening or guideline-level treatment scenarios were generally not cost-effective in Ghana, but treating self-referring patients with a hypothetical one-time laser surgery was highly cost-effective relative to World Health Organization willingness to pay thresholds.

CONCLUSIONS

The social and economic burden of glaucoma is higher in developed nations because of increased life expectancy, an older population age profile, and higher per capita gross domestic product. Similarly, lower mortality rates and higher per capita gross domestic product increase the relative cost-effectiveness of screening and treatment interventions intended to mitigate glaucoma burden.

The cost-effectiveness of routine office-based identification and subsequent medical treatment of primary open-angle glaucoma in the United States

OBJECTIVE

To estimate the incremental cost-effectiveness of routine glaucoma assessment and treatment under current eye care visit and treatment patterns and different levels of treatment effectiveness (from randomized trials).

DESIGN

We compared the costs and benefits of routine glaucoma assessment and treatment compared with no treatment using conservative and optimistic assumptions regarding treatment efficacy and including and excluding prediagnostic assessment costs.

PARTICIPANTS AND CONTROLS

Computer simulation of 20 million people followed from age 50 years to death or age 100 years.

METHODS

With the use of a computer model, we simulated glaucoma incidence, natural progression, diagnosis, and treatment. We defined glaucoma incidence conservatively as a mean deviation of -4 decibels (dB) on visual field testing in either eye for all diagnoses to be both clinically meaningful and unambiguous. We simulated the annual probability of subsequent progression and the quantity of visual field lost when progression occurred.

MAIN OUTCOME MEASURES

Visual field loss, ophthalmologic and nursing home costs, quality-adjusted life years (QALYs), cost per QALY gained, and cost per year of sight gained. Costs and QALYs were discounted to 2005 values using a 3% rate.

RESULTS

Compared with no treatment and when including diagnostic assessment costs, the incremental cost-effectiveness of routine assessment and treatment was $46,000 per QALY gained, assuming conservative treatment efficacy, and $28,000 per QALY gained, assuming optimistic treatment efficacy. Compared with no treatment and when excluding diagnostic assessment costs, the incremental cost-effectiveness of routine assessment and treatment was $20,000 per QALY gained, assuming conservative treatment efficacy, and $11,000 per QALY gained, assuming optimistic treatment efficacy. The cost-effectiveness was most sensitive to the treatment costs and the value of QALY losses assigned to visual field losses.

CONCLUSIONS

Glaucoma treatment was highly cost-effective when the costs of diagnostic assessments were excluded or when we assumed optimistic treatment efficacy. The cost was reasonable and in line with other health interventions even when diagnostic assessment costs were included and assuming conservative efficacy.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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.

Sensitivity and specificity of frequency-doubling technology, tendency-oriented perimetry, SITA Standard and SITA Fast perimetry in perimetrically inexperienced individuals

PURPOSE

To evaluate the sensitivity and specificity of the screening modes of frequency-doubling technology (FDT), tendency-oriented perimetry (TOP), SITA Standard (SS) and SITA Fast (SF) in perimetrically inexperienced individuals.

METHODS

One eye of 64 glaucoma patients and 53 normal subjects who had never undergone automated perimetry were tested with programs C-20-5 (FDT), G1 (TOP) and 24-2 (SS and SF). The gold standard for glaucoma was the presence of a typical glaucomatous optic disc appearance on stereoscopic examination (judged by a glaucoma expert), and intraocular pressure (IOP) > 21 mmHg. The test order among strategies was randomized for each subject. To define an abnormal visual field, we applied three criteria for SS and SF and two criteria for TOP and FDT, all of which have been previously described in the literature. Sensitivities and specificities among the different criteria were compared using the Cochran test.

RESULTS

Frequency-doubling technology showed the shortest mean test duration, followed by TOP, SF and SS (p < 0.05). Sensitivity ranges were 87.5-89.1% for SS, 92.2-93.8% for SF, 87.5-89.1% for TOP, and 82.8-85.9% for FDT (p = 0.34). Specificity ranges were 73.6-83% for FDT, 56.6-62.3% for TOP, 60.4-69.8% for SF and 66.0-71.7% for SS. The specificity obtained with criterion 2 for FDT (based on the presence of two or more abnormal locations regardless of the severity of abnormal points) was higher than those measured with the other strategies (p < 0.01).

CONCLUSION

When testing individuals with no perimetric experience, moderate sensitivities and specificities should be expected, regardless of the strategy chosen.

Evaluation of Decision Rules for Frequency-Doubling Technology Screening Tests

PURPOSE

Frequency-doubling technology (FDT) perimetry has shown promise as a screening test for glaucoma. This study investigates different possible decision rules for FDT screening by applying them to groups of normal and glaucoma subjects.

METHODS

Within three centers, 218 subjects (aged 15-88 years; 78 with glaucoma, 140 without ocular disease) were each tested twice with the screening program of the FDT perimeter. The subjects consisted of 140 normal subjects with no evidence of glaucoma or other ocular disease likely to affect the visual field and 78 subjects with a diagnosis of glaucoma and no other ocular disease. Fifteen decision rules were applied to the data to compare their sensitivity and specificity.

RESULTS

Estimated specificities of the different decision rules ranged from 78% to 99%, although with this sample size, the confidence intervals for these estimates are quite large. Estimated sensitivities ranged from 40% to 72%. Suggested criteria for distinguishing normal subjects from those with glaucoma seem to be either a cluster of two or more adjacent locations abnormal at the p < 2% level with at least one location confirmed or a single location very abnormal (p < 1%) and confirmed.

CONCLUSIONS

Specificity was clearly improved by confirming an apparently abnormal test result by repeating the screening test outweighing the resultant small loss in sensitivity. These findings provide useful information for making an informed choice of decision rules for FDT screening results.

What is practical in glaucoma management?

This article addresses some important issues in the detection and management of glaucoma using examples from the developing world, particularly drawing on experiences and research in sub-Saharan Africa.

Detecting glaucoma with frequency-doubling technology perimetry: a comparison between N-30 and C-20 screening programs

PURPOSE

To evaluate the ability of frequency-doubling technology (FDT) perimetry in detecting glaucoma with N-30 and C-20 screening programs.

METHODS

Eighty eyes of 80 patients were enrolled (40 glaucomatous, 40 controls). Humphrey achromatic perimetry (standard automated perimetry, SAP) was considered as the "gold standard" for diagnosis. To assess whether N-30 screening program could detect more initial glaucomatous defects than C-20, glaucomatous patients included 20 cases with nasal step at SAP (pre-selected by medical chart inspection). Patients underwent two SAP examinations to confirm diagnosis; then two N-30 and two C-20 screening tests with frequency-doubling technology were performed in a randomized sequence. Finally, a frequency-doubling technology N-30 full-threshold examination was performed. Several criteria to define abnormality at frequency-doubling technology screening programs were evaluated.

RESULTS

For both C-20 and N-30 screening programs, the best parameter to detect glaucoma was the presence of at least 1 point with P < 5% (sensitivity = 87.5% for both tests and specificity of 90% and 95% for C-20 and N-30, respectively). Both screening procedures obtained a lower sensitivity (75%) in patients with a nasal step, whereas frequency-doubling technology full-threshold program was able to detect the initial defects in all cases.

CONCLUSIONS

N-30 and C-20 screening procedures obtained similar results in well-defined glaucoma patients in terms of sensitivity and specificity. In the presence of a standard automated perimetry nasal step, diagnostic ability with both frequency-doubling technology screening strategies decreased and one quarter of nasal steps went undetected.

Sensitivity and specificity of the 76-suprathreshold visual field test to detect eyes with visual field defect by Humphrey threshold testing in a population-based setting: the Thessaloniki eye study

PURPOSE

To evaluate the screening performance of the 76-Suprathreshold (76-STHR) visual field test to detect eyes with visual field defect (VFD) as measured by Humphrey threshold testing in a population-based setting.

DESIGN

Cross-sectional study.

METHODS

All 88 subjects who agreed to participate in the pilot phase of the Thessaloniki Eye Study were included. Participants underwent a 76-STHR visual field test followed by a 30-full threshold (30-2 FTHR) test (Humphrey field analyzer). One eye/subject was randomly selected and included in the analysis. Sensitivity and specificity rates of the 76-STHR to detect eyes with VFD by the 30 to 2 FTHR test were calculated.

RESULTS

When eyes with borderline results in the 30 to 2 FTHR test were classified as having a VFD, sensitivity rates of the 76-STHR to detect eyes with VFD by the 30 to 2 FTHR were 85.2%, 77.8%, and 74.1%, whereas specificity rates were 70%, 78%, and 86%, depending on the cutoff used for the 76-STHR.

CONCLUSIONS

The 76-STHR test showed high sensitivity and low false-negative results at the "at least one point missed" cutoff level criterion to detect eyes with visual field defect by Humphrey threshold testing in a population-based setting. This criterion should be used when screening in a population-based study setting. By contrast, the 76-STHR would not be the appropriate screening test in a primary care setting with limited resources.

The Finnish evidence-based guideline for open-angle glaucoma

In most patients, chronic open-angle glaucoma is a slowly progressive disease. Eyes with very high intraocular pressure (IOP > 30 mmHg) represent an exception to this and should be treated and followed extremely intensively. As lowering IOP is, so far, the only means of treating glaucoma, the majority of research reports deal with the IOP-lowering effect of the treatment. The primary goal of treatment, however, is to prevent glaucomatous damage to the structures and function of the eye. The effectiveness of treatment is monitored with optic disc and retinal nerve fibre layer imaging and with visual field examinations. If the glaucomatous changes are progressing, more effective treatment should be given. In the course of follow-up, it should be noted that the changes in the optic nerve structure and function appear and progress at different time-points with delays of up to several years. The assessment of abnormalities is dependent on the examination method and requires a great deal of experience on the part of the examiner. The important risk factors in glaucoma are elevated IOP (even if IOP is within normal range in half of patients ), age, positive family history, exfoliation, race and myopia.

Temba glaucoma study: a population-based cross-sectional survey in urban South Africa

OBJECTIVE

To determine the prevalence and features of glaucoma in an urban South African black population.

DESIGN

Random sampling cross-sectional population survey.

PARTICIPANTS

Black residents of Temba, North West Province, South Africa, age > or =40 years.

MAIN OUTCOME MEASURES

Automated visual field testing and detailed, standardized slit-lamp examination were attempted on all subjects. Glaucoma was diagnosed by use of the scheme proposed by the Working Group for Defining Glaucoma of the International Society of Geographical and Epidemiologic Ophthalmology on the basis of evidence of end-organ damage.

RESULTS

Of 1120 subjects, 839 (74.9%) were examined. The age- and gender-adjusted prevalence of glaucoma of all types was 5.3% (95% confidence interval [CI], 3.9%-7.1%). Primary open-angle glaucoma (POAG) was the most common glaucoma diagnosis, with an adjusted prevalence of 2.9% (95% CI, 1.9%-4.3%). Secondary glaucoma occurred with an adjusted prevalence of 2.0% (95% CI, 1.2%-3.3%). Exfoliative glaucoma was responsible for 16% of all glaucoma cases. The prevalence of primary angle-closure glaucoma was 0.5% (95% CI, 0.13%-1.2%). Of all subjects with glaucoma, 58% were blind in at least one eye. The prevalence of all types of glaucoma increased with age. Of subjects with POAG, 87% had not been previously diagnosed.

CONCLUSIONS

The prevalence of glaucoma in this South African population was higher than that found in white populations, and most cases were undiagnosed and untreated. Glaucoma is a major cause of blindness in this population.

Multicenter evaluation of tendency-oriented perimetry (TOP) using the G1 grid

PURPOSE

The G1-TOP program is a short automated perimetric strategy which sub-divides the G1 grid of 59 points into four sub-grids. Each point is tested only once, but each patient's response is used to modify that particular point and the surrounding ones from the remaining sub-grids. This study compared the results of the G1-TOP program with the Standard Bracketing strategy.

METHODS

Eleven participating institutions provided data from 213 patients (406 eyes). The main group consisted of 284 glaucomas and 55 glaucoma suspects. Other groups included 31 eyes with neurological disorders, 20 with chorioretinal lesions and 16 normal eyes. Mean age was 62.7 +/- 15.4 (range 14-88) years. All subjects had previous perimetric experience and visual acuity better than 0.5. Examination included G1-Standard Bracketing and G1-TOP testing, in interchangeable order, with the Octopus 1-2-3 perimeter.

RESULTS

The correlation coefficient for mean defect (MD) was 0.95. Standard error (YX) for MD, square root of loss variance (LV) and individual thresholds were 1.86 dB, 1.29 dB, and 4.72 dB, respectively. Mean sensitivity values were similar (difference 0.04 +/- 1.87 dB) (p>0.05). Mean duration for G1-TOP was 2.19 +/- 0.26 min, while G1-Standard Bracketing took 11.51 +/- 1.52 min (ratio 1/5.1, or a net reduction of 80.4%). The sensitivity of G1-TOP versus G1-Standard Bracketing was: glaucoma 77.1/78.5, glaucoma suspects 38.2/47.3, neurological disorders 87.1/87.1 and chorioretinal lesions 80.0/85.0.

CONCLUSIONS

The G1-TOP program gave very similar results to G1-Standard Bracketing in only 20% of the time required by the standard strategy.

Frequency-doubling perimetry after photorefractive keratectomy

PURPOSE

To evaluate the effect of photorefractive keratectomy (PRK) on frequency-doubling perimetry (FDP) patterns in myopic patients without glaucoma.

SETTING

Department of Ophthalmology, University of Bari, Bari, Italy.

METHODS

Sixteen myopic patients (16 eyes) with a spherical equivalent worse than -7.0 diopters were enrolled. The fellow eyes were used as controls. All patients had PRK for myopia. Using FDP, the mean defect (MD) and pattern standard deviation (PSD) were evaluated preoperatively and 2 weeks and 3 and 6 months after PRK. At the same examinations, the effect of the reprofiled cornea on the visual field was studied; the cornea was divided into 4 concentric zones (central, paracentral, lateral, and peripheral) and each median zone contrast sensitivity (MZCS) evaluated.

RESULTS

There was no difference in PSD and MZCS between treated eyes and controls in any zone at any time (P >.05). Longitudinally, there was no variation in any perimetry zone (P >.05). In treated eyes, there was a significant relationship among ablation depth, MD, and MZCS in all zones until 2 weeks after laser surgery (P <.02).

CONCLUSIONS

Frequency-doubling perimetry did not appear to be affected by corneal changes induced by PRK and can therefore be safely used in the early diagnosis of glaucoma.

Performance of glaucoma mass screening with only a visual field test using frequency-doubling technology perimetry

PURPOSE

To report the performance of glaucoma mass screening with only a visual field test utilizing frequency- doubling technology (FDT) perimetry in general populations.

DESIGN

Hospital and population-based cross-sectional study.

METHODS

This study took place in a multicenter setting. One hundred three consecutive glaucomatous patients and 14,814 persons were randomly selected. We had created a glaucoma screening protocol (GSP) using FDT perimetry (FDT-GSP). Frequency-doubling technology-glaucoma screening protocol was tested on consecutive glaucoma patients diagnosed with Humphrey visual field analyzer (30-2 SITA standard), and then FDT-GSP was applied to general populations. Frequency-doubling technology-glaucoma screening protocol positive subjects were ophthalmologically diagnosed. Detection ability of FDT-GSP was determined in consecutive patients, and the positive predictive value (PPV) of FDT-GSP to detect definitive glaucoma was estimated in general populations.

RESULTS

Frequency-doubling technique-glaucoma screening protocol detected 83.3% and 100% of definitive glaucoma patients with an early (mean deviation [MD] > -6 dB) and more advanced stage (MD < or = -6 dB), respectively. In the population-based screening, there were 660 (4.5%) subjects who had positive FDT-GSP, including 512 in whom no visual field abnormalities (VFA) had been pointed out previously. Of them, 370 subjects underwent ophthalmologic diagnosis. Then, 266 (71.9%, 266/370) subjects had a glaucomatous disk and 167 had definitive glaucomatous VFA. Fifty-five (14.9%) and 39 (10.5%) subjects were diagnosed as having other diseases and as normal, respectively. The PPV of FDT-GSP ranged from 32.6% (167/512)-45.1% (167/370).

CONCLUSIONS

Frequency-doubling technology-based screening with only a visual field test showed reasonable performance on mass screening for detection of definitive glaucoma in this study population, considering the glaucoma prevalence.

New developments in supra-threshold perimetry

PURPOSE

To describe a series of recent enhancements to supra-threshold perimetry.

METHODS

Computer simulations were used to develop an improved algorithm (HEART) for the setting of the supra-threshold test intensity at the beginning of a field test, and to evaluate the relationship between various pass/fail criteria and the test's performance (sensitivity and specificity) and how they compare with modern threshold perimetry. Data were collected in optometric practices to evaluate HEART and to assess how the patient's response times can be analysed to detect false positive response errors in visual field test results.

RESULTS

The HEART algorithm shows improved performance (reduced between-eye differences) over current algorithms. A pass/fail criterion of '3 stimuli seen of 3-5 presentations' at each test location reduces test/retest variability and combines high sensitivity and specificity. A large percentage of false positive responses can be detected by comparing their latencies to the average response time of a patient.

CONCLUSIONS

Optimised supra-threshold visual field tests can perform as well as modern threshold techniques. Such tests may be easier to perform for novice patients, compared with the more demanding threshold tests.

Sensitivity and specificity of the Swedish interactive threshold algorithm for glaucomatous visual field defects

PURPOSE

To determine the sensitivity and specificity of two new visual field algorithms in detecting glaucomatous visual field defects: (1) Swedish interactive threshold algorithm (SITA) standard and (2) SITA fast.

DESIGN

Prospective observational case series.

PARTICIPANTS

Ninety normal subjects and 82 glaucoma patients.

TESTING

Central 30 degrees fields were performed with the Humphrey visual field analyzer 30-2 program (Humphrey Systems, Dublin, CA) using full threshold, SITA standard, and SITA fast algorithms on the same day for two or more sessions within a 1-month period.

MAIN OUTCOME MEASURES

Sensitivity and specificity in detecting glaucomatous visual field defects with SITA standard and SITA fast using full threshold testing as the reference standard.

RESULTS

The sensitivity of SITA standard and SITA fast in detecting glaucomatous defects overall was 98% and 95%, respectively. In the subset of mild glaucomatous field defects (26 patients), sensitivity of SITA standard was 92% versus 85% with SITA fast. Sensitivity was 100% for both algorithms in moderate to severe glaucomatous defects. Specificity for glaucoma defects using SITA standard and SITA fast was 96% for both algorithms. SITA standard reduced test-taking time from full threshold by 52% in normal subjects and 47% in glaucoma patients (P < 0.001). SITA fast reduced test-taking time by 72% in normal subjects and 65% in glaucoma patients (P < 0.001). Mean deviation values were 0.4 dB and 0.8 dB better in SITA standard and SITA fast fields, respectively, in normal subjects (P < 0.001), and 0.7 dB and 1.2 dB in SITA standard and SITA fast fields, respectively, in glaucoma patients (P < 0.001) compared with full threshold values.

CONCLUSIONS

The new algorithms for measuring visual fields, SITA standard and SITA fast, have excellent sensitivity and specificity for glaucomatous visual field loss with considerable savings in time.

Community screening for eye disease by laypersons: the Hoffberger program

PURPOSE

To describe the results of a community-based eye screening program in Baltimore.

DESIGN

Cross-sectional study.

METHODS

This was a retrospective study of the results of screening both eyes of 5352 persons who presented at multiple community sites. The screening examination had eight risk factor questions, visual acuity measurement, and a screening field test and was carried out by technicians and lay volunteers. Screened persons (screenees) received a definitive eye examination at no out-of-pocket cost, transportation was offered, and inexpensive eyeglasses were provided if needed. The main outcome measures were the rate of appointment keeping and the eye diseases identified. Telephone interviews were used to assess reasons for missing appointments and satisfaction with visits.

RESULTS

Screenees had a median age of 45 years, were 71% black, 59% female, and had estimated median annual family income of 24,000 dollars. Among 1331 screenees who scheduled a definitive examination appointment, 552 (41%) completed the visit. Data on definitive diagnosis was available in 480 out of 552 persons (87%). Reasons given for failing to come for definitive examination were: no appointment given (26%), forgot (20%), lack of transportation (9%), and lack of insurance coverage (6%). Of those who accepted a second visit date after defaulting, only 25% (41/167) appeared. Of 17 persons identified with glaucoma at screening, 4 had previously been diagnosed, but had ceased active care.

CONCLUSION

After community screening for eye disease, efforts to provide definitive ophthalmic examination were only modestly effective. Failure of screenees to come for examination and loss to follow up were identified as serious problems.

Sensitivity and specificity of frequency-doubling technology, tendency-oriented perimetry, and Humphrey Swedish interactive threshold algorithm-fast perimetry in a glaucoma practice

PURPOSE

To evaluate the sensitivity and specificity of the screening mode of the Humphrey-Welch Allyn frequency-doubling technology (FDT), Octopus tendency-oriented perimetry (TOP), and the Humphrey Swedish Interactive Threshold Algorithm (SITA)-fast (HSF) in patients with glaucoma.

DESIGN

A comparative consecutive case series.

METHODS

This was a prospective study which took place in the glaucoma unit of an academic department of ophthalmology. One eye of 70 consecutive glaucoma patients and 28 age-matched normal subjects was studied. Eyes were examined with the program C-20 of FDT, G1-TOP, and 24-2 HSF in one visit and in random order. The gold standard for glaucoma was presence of a typical glaucomatous optic disk appearance on stereoscopic examination, which was judged by a glaucoma expert. The sensitivity and specificity, positive and negative predictive value, and receiver operating characteristic (ROC) curves of two algorithms for the FDT screening test, two algorithms for TOP, and three algorithms for HSF, as defined before the start of this study, were evaluated. The time required for each test was also analyzed.

RESULTS

Values for area under the ROC curve ranged from 82.5%-93.9%. The largest area (93.9%) under the ROC curve was obtained with the FDT criteria, defining abnormality as presence of at least one abnormal location. Mean test time was 1.08 +/- 0.28 minutes, 2.31 +/- 0.28 minutes, and 4.14 +/- 0.57 minutes for the FDT, TOP, and HSF, respectively. The difference in testing time was statistically significant (P <.0001).

CONCLUSIONS

The C-20 FDT, G1-TOP, and 24-2 HSF appear to be useful tools to diagnose glaucoma. The test C-20 FDT and G1-TOP take approximately 1/4 and 1/2 of the time taken by 24 to 2 HSF.

Frequency doubling perimetry in glaucoma

PURPOSE

To evaluate the validity of frequency doubling perimetry (FDP) in the detection of glaucomatous field defects.

METHODS

Group I consisted of 85 eyes of 85 patients with established field defects in automated perimetry, classified by severity of defect. Group II consisted of 48 eyes of 48 control subjects. Both groups underwent Swedish Interactive Testing Algorithm (SITA) standard tests as well as FDP screening strategies (C20-1 and C20-5 and full threshold test). Sensitivity and specificity measures for the FDP tests were calculated using one new and two previously published algorithms.

RESULTS

A described scoring system provided the best sensitivity (85.9%) and specificity (95.1%). For moderate and severe cases, the sensitivity improved to 91%. Quantification of the defect did not improve detection.

CONCLUSIONS

FDP is a valid screening test for glaucoma. The scoring system described by Patel et al. provided the best results.

Comparison of the frequency doubling technology screening algorithm and the Humphrey 24-2 SITA-FAST in a large eye screening

PURPOSE

To compare the Frequency Doubling Technology (FDT) C20-1 screening algorithm and the Humphrey Field Analyser II (HFA) 24-2 SITA-FAST in a large eye screening.

METHODS

In a non-randomized, prospective, free eye screening, the FDT Screening Protocol (C20-1 Screening Algorithm) was administered to 574 attendees (422 men and 152 women, average age 64, range 17-89 years) of the 1998 Veterans of Foreign Wars (VFW) Convention in San Antonio, Texas. Individuals who failed the FDT (two or more misses out of 17 locations) immediately underwent white-on-white threshold visual field perimetry (HFA 24-2, SITA-FAST). Humphrey visual field analysis included STATPAC and masked evaluations by three glaucoma specialists.

RESULTS

Approximately one-tenth of the VFW conference attendees voluntarily presented themselves for screening. Among these 574 volunteers, 69 (12%) failed the FDT and underwent HFA analysis. Eighty-one per cent (56/69) of these FDT failures had abnormal HFA Glaucoma Hemifield Tests. Eighty-eight per cent (61/69) were judged to have nerve fibre type visual field loss on HFA by at least two of three masked examiners. A positive correlation existed between the number of FDT locations missed and the HFA mean deviation (r = 0.5, P = 0.0001). A similar association was observed when FDT and HFA results were analysed by quadrant (r = 0.5, P < 0.0001).

CONCLUSION

There was a low false positive rate and a good positive predictive value comparing the FDT screening algorithm to the HFA 24-2 SITA-FAST in this study. This supports the potential use of FDT as an economical screening device.

Frequency of sustained glaucomatous-type visual field loss and associated optic nerve cupping in Beaver Dam, Wisconsin

PURPOSE

To determine the prevalence of persisting glaucomatous-type visual field loss in a Midwestern American adult population, in association with four grades of disc cupping.

METHODS

On two separate occasions (1988-1990 and 1993-1995) 2955 predominantly Caucasian adults aged 43-84 provided medical history, underwent applanation tonometry, slit-lamp examination, quantitative suprathreshold perimetry and stereoscopic disc analysis as part of the National Institutes of Health-sponsored Beaver Dam Eye Study. Those demonstrating evidence of glaucomatous-type visual field loss at both visits were the subject of the present analysis. Among these individuals, associations were determined for four categories of optic disc cupping (vertical cup/disc < 0.5, > 0.5, > 0.6, > 0.8), intraocular pressure, blood pressure, cardiovascular pathology and prior glaucoma diagnosis.

RESULTS

Of the 2955 subjects assessed, 120 (4%; 57 women, 63 men) demonstrated glaucomatous-type visual field defects at each visit. Fifty-five of these 120 (2% of the tested population) also exhibited some degree of disc cupping in a related eye at both visits. Among these 2%, positive associations relating the extent of field loss, cupping and intraocular pressure were confirmed, but the majority in each cupping category had normal eye pressures. Only seven of the 120 were aware of the presence or suspicion of eye disease prior to the screening.

CONCLUSIONS

A majority of those found to have visual field loss and optic nerve cupping persisting together in the same eye after 3-5 years had normal pressures in each eye at both visits. Despite good access to medical care, very few who demonstrated persisting cupping and field loss (even among those with elevated eye pressure) were aware of their ocular condition through prior contact with an eye care professional.

Evaluating a visual field screening test for glaucoma: how the choice of the gold standard affects the validity of the test

OBJECTIVE

To examine the effects of the gold standard on sensitivity, specificity, and area under the ROC curve when determining the validity of a screening test.

METHODS

Fifty-eight people were recruited from a Veterans' Administration eye clinic. Screening included testing with the 26-point oculokinetic perimeter (OKP). We used different gold standards to categorize patients as positive or negative for glaucoma. The glaucoma hemifield test (GHT) and corrected pattern standard deviation (CPSD) from the Humphrey visual field analyzer (HVF) were used as objective gold standards. Ophthalmologist review of the HVF, using two different methods for classifying visual field defects, was also used as a gold standard.

RESULTS

Using the review of the HVF that included mild, moderate, or severe defects, the area under the ROC curve was not significantly different from 50%. However, for all the other gold standards, the area under the ROC curve was significantly different from 50%.

CONCLUSIONS

In determining the ability of the OKP to differentiate between glaucoma and normal subjects, the choice of a gold standard led to different conclusions about its usefulness as a screening test for glaucoma. Furthermore, sensitivity and specificity varied widely depending on which gold standard was used, and what cutoff point was used for the OKP. Although clinician review of the HVF may be used when specific criteria are given to define visual field defects, using objective measures from the HVF is easier and will allow for better comparisons between studies.

Frequency doubling perimetry using a liquid crystal display

PURPOSE

To compare frequency doubling contrast thresholds using a new liquid crystal window display with those obtained with the commercial video-based Frequency Doubling Technology perimeter.

METHODS

One eye of 49 glaucoma patients and one eye of 49 normal controls were tested with the liquid crystal window and Frequency Doubling Technology systems. Both displays employed identical stimulus conditions and test strategies, although the dynamic range of the liquid crystal window-based display was approximately 30% smaller than that of the Frequency Doubling Technology system. Measurements were repeated using the video-based Frequency Doubling Technology perimeter in a subset of 21 eyes. Relationships between and within displays were assessed using a chance-corrected agreement measure (quadratic weighted kappa) and paired measurement differences. Variability was quantified using standard deviation from the mean paired measurement difference.

RESULTS

Over the restricted operating range of the liquid crystal display system, between-display and within-video display variability was 2.3 dB and 3.2 dB, respectively, between-display agreement was 0.66, and within-display agreement (test-retest for Frequency Doubling Technology) was 0.65.

CONCLUSIONS

Levels of agreement and variability between the two frequency doubling displays were of similar magnitude to repeated (test-retest) Frequency Doubling Technology measures, suggesting that contrast threshold measurements made using the two displays may be used interchangeably. However, the operating range of the current liquid crystal window-based display is smaller.

Accuracy of glaucoma detection with frequency-doubling perimetry

PURPOSE

To determine the accuracy of glaucoma detection by frequency-doubling perimetry.

METHODS

Stereoview optic nerve photographs, visual field examination, intraocular pressure measurements, medical and ocular history, and a screening and full threshold frequency-doubling perimetry examination were performed in a prospective study of consecutive subjects. Inclusion criteria included age of 45 years or older, absence of ocular disease other than glaucoma, cataract, or mild drusen, and Snellen visual acuity of 20/60 or better. A total of 125 eyes in 102 glaucoma subjects and 95 eyes of 95 normal subjects were included. Each eye was classified as "normal," "glaucoma," or "uncertain" by each of three ophthalmologists on the basis of all available clinical information with the exception of frequency-doubling perimetry results. Those in the glaucoma group were subclassified as having early (n = 51), moderate (n = 42), or severe (n = 32) glaucoma on the basis of automated Humphrey visual field criteria. In the glaucoma group, two eyes from a subject were allowed to be included (23 of 102 subjects) if they differed in level of damage because they were never analyzed within the same statistical analysis.

RESULTS

Several diagnostic algorithms were evaluated. Algorithms based on the most depressed single point, pair of adjacent points, and cluster of three points performed nearly identically. For the screening test, if any abnormality was identified, specificity was 95%, whereas sensitivity was 39%, 86%, and 100% for early, moderate, and severe glaucoma, respectively. For the full threshold test, with at least one point depressed to the P < 0.5% level, specificity measured 91%, whereas sensitivity was 35%, 88%, and 100% for early, moderate, and severe glaucoma, respectively. The two global indices, mean deviation and pattern standard deviation, were also evaluated and were generally less accurate.

CONCLUSION

Frequency-doubling perimetry, which is rapid and easily administered, is effective at detecting moderate and severe disease and appears well suited for glaucoma screening.

Management of ocular hypertension and primary open angle glaucoma

BACKGROUND: Glaucoma and ocular hypertension are among the most common pathologies encountered in clinical practice. Within the next 20 years, patients with these two problems will increase threefold as the population ages. The growing burden of glaucoma worldwide will also become a significant public health problem. The effective management of glaucoma will require the introduction of new screening strategies and better therapeutic approaches to these disorders. METHODS: Our current understanding of the epidemiology of primary open angle glaucoma and ocular hypertension is reviewed. Diagnosis and treatment strategies are discussed in the context of the current best available clinical trial and laboratory data. RESULTS: While few patients with ocular hypertension will require therapy, it is the conventional practice to lower the intraocular pressure by at least one-third once glaucomatous optic neuropathy is detected. Topical beta-adrenergic antagonists have been the preferred first-line therapy for primary open angle glaucoma for the past 20 years, but with the advent of topical prostaglandin analogues and alpha-2 agonists, the effectiveness of medical therapy has improved significantly. The decision to perform glaucoma filtering surgery or laser trabeculoplasty must be carefully considered and based on the past response to medication, the extent and rate of progression of any visual field loss, and on the life expectancy and wishes of the patient. CONCLUSION: The treatment of chronic glaucoma is directed at preserving vision and interfering with the quality of life of the patient as little as possible. Many older patients who develop primary open angle glaucoma may have a limited life expectancy and do not require aggressive medical therapy or surgery. Many new medications have become available that permit less frequent dosing with fewer local and systemic side-effects. In the near future, therapies that address the underlying molecular basis of glaucomatous optic neuropathy might become available and further reduce the risk of glaucoma blindness.

Algorithm for interpreting the results of frequency doubling perimetry

PURPOSE

To evaluate an algorithm for the identification of glaucomatous visual field defects with the screening mode of frequency doubling technology.

METHODS

Screening-mode frequency doubling technology and Swedish interactive threshold algorithm perimetry were performed on 137 of 150 consecutive patients referred to a glaucoma specialist. We created an algorithm for the frequency doubling technology that gave increased importance to both more severe defects and defects closer to fixation. These values were then compared with the results of the Swedish interactive threshold algorithm visual fields evaluated by the glaucoma hemifield test, two masked glaucoma specialists, and a published definition of glaucomatous damage to determine sensitivity and specificity of the frequency doubling technology screening mode for detecting glaucoma.

Comparison between Tendency-Oriented Perimetry (TOP) and octopus threshold perimetry

OBJECTIVE

To compare the results obtained by a new ultra-short automated perimetry test known as Tendency-Oriented Perimetry (TOP), which is an algorithm based on estimation of thresholds from information gathered from adjacent points with those obtained by a standard bracketing approach. TOP is designed to save up to 1/5 of the time taken by standard strategy by presenting each stimulus once on each location (instead of 4 to 6 times per location with the standard technique) and reaching a final threshold estimate by gathering information from responses to adjacent locations.

DESIGN

Prospective, multicenter, observational comparative case series.

PARTICIPANTS/METHODS

Four academic institutions provided data from testing 57 subjects, 15 with a normal ocular exam and 42 with a variety of visual field abnormalities. A total of 228 visual fields were analyzed. Two examinations of standard thresholding testing (Octopus program 32) and two examinations of the TOP program were obtained in each subject the same day.

MAIN OUTCOME MEASURES

Comparison of global indices such as mean deviation (MD), square root of loss of variance (sLV), topographical defects, point by point differences, reproducibility, sensitivity/specificity, and time required to complete the test.

RESULTS

Correlation coefficient of global indices between both tests was high, with mean deviation of r = 0.97 (SE[YX] +/- 1.65 decibels) and square root of loss variance of r = 0.93 (SE[YX] +/- 1.10 dB). Mean sensitivity tended to be 1 dB higher while MD tended to be 1 dB lower with TOP strategy. Reproducibility was equally good between both tests for threshold determination as well as for all global indices (MS, MD per quadrant, and LV). Cluster criteria for abnormality demonstrated TOP versus 32: sensitivity of 89/87; specificity of 90/77; positive predictive value of 96/91; negative predictive value of 75/68; and accuracy of 89/84. Mean time taken by this beta version of TOP was 4.05 minutes standard deviation +/- 0.55 versus the standard 32 version taking 14.65 minutes standard deviation +/- 3.75.

CONCLUSIONS

TOP was four times faster than the traditional full-threshold technique and was successful in detecting visual field abnormalities. Defects with TOP tended to be smaller, shallower, and with softer edges than with standard approach. TOP could prove an alternative to traditional perimetric techniques.

Glaucoma

In 2000 an estimated 66.8 million people worldwide will have glaucoma, 6.7 million of whom will be bilaterally blind from irreversible optic-nerve damage. Yet even in developed countries with public educational programmes that target glaucoma, half of the individuals with glaucoma remain undiagnosed. Patients with even mild visual impairment secondary to glaucoma may have difficulties with mobility, driving, and social interactions. Although glaucoma may be associated with increased eye pressures, its diagnosis does not rely on a specific level of eye pressure. Diagnosis of glaucoma often relies on examination of the optic disc and assessment of the visual field. The two most common types of glaucoma--primary open-angle glaucoma and primary angle-closure glaucoma--have different risk factors. Although similar medications can be used to treat these two types of glaucoma, the overall management of patients differs in important ways. Until recently, there were no randomised clinical trials that showed the effectiveness of lowering eye pressures with medications or surgery in patients with glaucoma. However, in 1998 a randomised clinical trial showed the benefit of lowering eye pressure in patients with glaucoma who had eye pressures of 24 mm Hg or less. Because glaucoma is treatable, and because the visual impairment from glaucoma is irreversible, early detection of the disease is critically important.