High-risk Ocular Hypertension Research Articles

Low-energy Selective Laser Trabeculoplasty Repeated Annually: Rationale for the COAST Trial.

The recent Laser in Glaucoma and Ocular Hypertension Trial provided the evidentiary basis for a paradigm shift away from the historical medication-first approach to glaucoma--which has numerous limitations, the most important of which is poor adherence to therapy --and toward a laser-first approach. Now 20 years after its commercialization, selective laser trabeculoplasty (SLT) is routinely performed consistently with its initial description, with energy titrated to the appearance of fine, champagne-like cavitation bubbles. A recent data set suggested that lower energy SLT, applied as primary therapy and repeated annually irrespective of intraocular pressure--rather than pro re nata when its effect wanes and irrespective of intraocular pressure rises --yields longer medication-free survival than standard energy SLT repeated pro re nata. A new study--Clarifying the Optimal Application of SLT Therapy --has been initiated to explore this preliminary finding in a pair of consecutive randomized trials. Herein, we provide an evidence-based rationale for the use of low-energy SLT repeated annually as primary therapy for mild to moderate primary open-angle glaucoma or high-risk ocular hypertension.

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

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

The Effect of Limiting the Range of Perimetric Sensitivities on Pointwise Assessment of Visual Field Progression in Glaucoma.

PurposeAutomated perimetry does not produce reliable estimates of true psychophysical threshold in glaucomatous visual fields when the perimetric threshold falls below 15 to 19 dB. It may be possible to truncate testing at such locations and not use stimuli with very high contrast. However, this can only be recommended if it does not harm the ability to monitor change. This study examined the effect of applying such a cutoff by censoring sensitivities in two existing longitudinal datasets.MethodsSeries of six visual fields were taken from participants with glaucoma or high-risk ocular hypertension in the Portland Progression Project (P3) and Rotterdam Eye Study (RES). Pointwise linear regression was used to find “progressing” locations, defined as a slope ≤ −1 dB/y with P < 1%. An eye was labeled progressing if ≥3 locations were progressing. This was repeated after setting any sensitivities below the cutoff value C (CdB) to instead equal that value for different integer values of CdB.ResultsIn the P3 cohort tested using Swedish Interactive Testing Algorithm (SITA) Standard, censoring below 15 to 19 dB did not reduce the number of eyes flagged as progressing. For the RES cohort tested using the Full Threshold algorithm, censoring below 10 dB did not reduce the number of eyes flagged as progressing, but a modest reduction was seen for CdB between 10 dB and 15 to 19 dB.ConclusionsThe proportion of eyes flagged as progressing was not decreased by censoring unreliable sensitivities. Restricting the range of contrast used in clinical perimetry may be possible without hampering the ability to monitor glaucomatous visual field progression.

Anterior Lamina Cribrosa Surface Depth, Age, and Visual Field Sensitivity in the Portland Progression Project

To assess the effect of age on spectral-domain optical coherence tomography (SDOCT)-detected lamina cribrosa depth while controlling for visual field (VF) status and retinal nerve fiber layer thickness (RNFLT) in 221 high-risk ocular hypertension and glaucoma patients enrolled in the Portland Progression Project. In this cross-sectional study, each participant underwent 870-nm SDOCT to obtain high-resolution radial B-scans centered on the optic nerve head (ONH) and a standardized ophthalmologic examination, including automated perimetry, on the same day. For each ONH, an anterior lamina cribrosa surface depth (ALCSD) parameter was generated as the average perpendicular distance from each anterior lamina cribrosa surface point relative to Bruch's membrane opening (BMO) reference plane within all 24 delineated B-scans. The relative effects of age, age-corrected VF status (mean deviation [MD]), and RNFLT on ALCSD were analyzed. The mean age ± SD of participants was 64 ± 11 years (range, 33-90 years). The relationship between ALCSD and MD was age-dependent. ALCSD = 407.68 - 67.13 × MD - 0.08 × Age + 0.89 × MD × Age (MD, P = 0.001; MD × Age, P = 0.004). The relationship between ALCSD and RNFLT may also be age-dependent but did not achieve significance (interaction term, P = 0.067). ALCSD increased with worse VF status in younger eyes but not in older eyes. In older eyes, the anterior lamina was shallower than in younger eyes for the same VF status and RNFLT. These data are consistent with the concept that structure/structure and structure/function relationships change with age.

A Method to Estimate the Amount of Neuroretinal Rim Tissue in Glaucoma: Comparison With Current Methods for Measuring Rim Area

To test whether the minimum rim area assessed by spectral domain optical coherence tomography (SD-OCT), based on the shortest distance from the Bruch membrane opening (BMO) to the inner limiting membrane, corresponds more closely to retinal nerve fiber layer (RNFL) thickness and visual field mean deviation (MD) than current rim measures in early glaucoma. Prospective cross-sectional study. We studied 221 participants with non-endstage glaucoma or high-risk ocular hypertension and performed standard automated perimetry. We received SD-OCT and confocal scanning laser ophthalmoscopy (CSLO) scans on the same day. Rim area measured by CSLO was compared with 3 SD-OCT rim measures from radial B-scans: horizontal rim area between BMO and inner limiting membrane within the BMO plane; mean minimum rim width (BMO-MRW); and minimum rim area (BMO-MRA) optimized within sectors and then summed. Correlations between these measures and either MD from perimetry or RNFL thickness from SD-OCT were compared using the Steiger test. RNFL thickness was better correlated with BMO-MRA (r = 0.676) or BMO-MRW (r = 0.680) than with either CSLO rim area (r = 0.330, P < 0.001) or horizontal rim area (r = 0.482, P < 0.001). MD was better correlated with BMO-MRA (r = 0.534) or BMO-MRW (r = 0.546) than with either CSLO rim area (r = 0.321, P < 0.001) or horizontal rim area (0.403, P < 0.001). The correlation between MD and RNFL thickness was r = 0.646. Minimum rim measurements from SD-OCT are significantly better correlated to both RNFL thickness and MD than rim measurements within the BMO plane or based on the clinical disc margin. They provide new structural parameters for both diagnostic and research purposes in glaucoma.

Morphometric Analysis and Classification of Glaucomatous Optic Neuropathy Using Radial Polynomials

To quantify the morphological features of the optic nerve head using radial polynomials, to use these morphometric models as the basis for classification of glaucomatous optic neuropathy via an automated decision tree induction algorithm, and to compare these classification results with established procedures. A cohort of patients with high-risk ocular hypertension or early glaucoma (n=179) and a second cohort of normal subjects (n=96) were evaluated for glaucomatous optic neuropathy using stereographic disc photography and confocal scanning laser tomography. Morphological features of the optic nerve head region were modeled from the tomography data using pseudo-Zernike radial polynomials and features derived from these models were used as the basis for classification by a decision tree induction algorithm. Decision tree classification performance was compared with expert classification of stereographic disc photographs and analysis of neural retinal rim thickness by Moorfields Regression Analysis (MRA). Root mean squared error of the morphometric models decreased asymptotically with additional polynomial coefficients, from 62±0.5 (32 coefficients) to 32±5.7 μm (256 coefficients). Optimal morphometric classification was derived from a subset of 64 total features and had low sensitivity (69%), high specificity (88%), very good accuracy (80%), and area under the receiver operating characteristic curve (AUROC) was 88% (95% confidence interval, 78%-98%). In comparison, MRA classification of the same records had a comparatively poorer sensitivity (55%), but had higher specificity (95%), with similar overall accuracy (78%) and AUROC curve, 83% (95% CI, 70%-96%). Pseudo-Zernike radial polynomials provide a mathematically compact and faithful morphological representation of the structural features of the optic nerve head. This morphometric method of glaucomatous optic neuropathy classification has greater sensitivity, and similar overall classification performance (AUROC) when compared with classification by neural retinal rim thickness by MRA in patients with high-risk ocular hypertension and early glaucoma.

The effect of test variability on the structure–function relationship in early glaucoma

To determine whether the weakness of the structure-function relationship could be produced by test variability alone, without implying underlying dissociation between the true rates of structural and functional change. Perimetric mean deviation (MD), and rim area (RA) and cup volume (CV) from confocal scanning laser ophthalmoscopy, over six visits, were taken from 166 eyes of 92 participants with high-risk ocular hypertension or suspected/early glaucoma in the Portland Progression Project. Models were created of each measure's variability. A further model predicted the rate of functional change from the rate of structural change. These were used to generate realistic simulated sequences of both functional and structural data with different standard deviations σ between the underlying rates of change. 'Observed' structure-function relationships were calculated. An empirical p-value was derived, equaling the proportion of simulated series for which the 'observed' structure-function dissociation was greater than that seen in patient data. The correlation between the rates of structural (RA) and functional (MD) change was 0.171, consistent with σ < 0.02dB/yr. Using CV, the correlation was -0.091, consistent with σ < 0.01dB/yr. By comparison, the models predicted that the standard deviation of the rate of functional change for a healthy eye due to test variability would be 0.18dB/yr. Test variability is sufficiently large that realistic patient data can be simulated without requiring a large variability between the underlying rates of structural and functional change. This absence of implied dissociation is a necessary condition for it to be valid to combine structural and functional measures to improve estimates of functional change and/or to reduce perimetric variability.

Cup Size Predicts Subsequent Functional Change in Early Glaucoma

To identify structural predictors of functional change in patients with early glaucoma or risk factors for development of glaucoma. One hundred twenty-nine participants with either high-risk ocular hypertension, suspected, or early glaucoma were followed for 10 annual visits. Standard Automated Perimetry was performed at each visit, along with Confocal Scanning Laser Ophthalmoscopy (CSLO). Mean deviation (MD) at the same visit and the subsequent rate of change in MD were predicted by linear regression models based on CSLO parameters along with intraocular pressure, central corneal thickness, and treatment status. Models were assessed by comparing the correlations between predicted and observed perimetric results. The model using rim area predicted MD at the same visit with correlation 0.445. Using cup area, the equivalent correlation was r = 0.411, lower than the model using rim area with p = 0.096. Using cup volume, the correlation was r = 0.436, and the comparison had p = 0.714; using disc area r = 0.396 and p = 0.011. The model using rim area to predict the subsequent rate of change of MD had r = 0.539. Models using cup area (r = 0.631), cup volume (r = 0.649), or disc area (r = 0.602) were significantly better; p = 0.003, p = 0.001, and p = 0.044, respectively. Lower rim area, as measured by CSLO, is predictive of worse function when measured on the same date in participants with high-risk ocular hypertension, suspected, and early glaucoma. However, cup area, cup volume, and disc area may all be more predictive of the rate of subsequent functional change. Parameters should be chosen based on the specific purpose intended and questions asked, rather than using the same parameters in all circumstances.

Assessment of Patient Opinions of Different Clinical Tests Used in the Management of Glaucoma

To compare different tests used in the clinical management of glaucoma, with respect to the testing experience for patients undergoing each test. Evaluation of diagnostic tests. A total of 101 subjects with high-risk ocular hypertension or early glaucoma. Subjects were asked to give their opinion on 7 tests used clinically in glaucoma management by assigning each a score between 0 (absolute dislike) and 10 (perfect satisfaction). Tests were ranked for each subject from 1 (favorite test) to 7 (least favorite test) on the basis of patient-assigned scores. Goldmann applanation tonometry for measurement of intraocular pressure was ranked significantly better than any other test (median rank 2.5, P<or=0.01). This was followed by confocal scanning laser ophthalmoscopy using a Heidelberg Retina Tomograph (median rank 3.3); frequency doubling technology perimetry (4.0); multifocal visual evoked potential (4.0); optic nerve photography (4.3); and standard automated perimetry (4.8). Short-wavelength automated perimetry was ranked significantly worse than any other test (median rank 5.3, P</=0.04). In many cases, statistically significant differences were found between the patients' opinions of the tests. Information on this issue has to date largely been anecdotal or subjective. To our knowledge, this is the most comprehensive study to assess and compare the patient experience when undergoing these tests. The authors have no proprietary or commercial interest in any materials discussed in this article.

Predicting Progressive Glaucomatous Optic Neuropathy Using Baseline Standard Automated Perimetry Data

To test the hypothesis that specific locations and patterns of threshold findings within the visual field have predictive value for progressive glaucomatous optic neuropathy (pGON). Age-adjusted standard automated perimetry thresholds, along with other clinical variables gathered at the initial examination of 168 individuals with high-risk ocular hypertension or early glaucoma, were used as predictors in a classification tree model. The classification variable was a determination of pGON, based on longitudinally gathered stereo optic nerve head photographs. Only data for the worse eye of each individual were included. Data from 100 normal subjects were used to test the specificity of the models. Classification tree models suggest that patterns of baseline visual field findings are predictive of pGON with sensitivity 65% and specificity 87% on average. Average specificity when data from normal subjects were run on the models was 69%. Classification trees can be used to determine which visual field locations are most predictive of poorer prognosis for pGON. Spatial patterns within the visual field convey useable predictive information, in most cases when thresholds are still well within the classically defined normal range.

Effect of Recording Duration on the Diagnostic Performance of Multifocal Visual-evoked Potentials in High-risk Ocular Hypertension and Early Glaucoma

To evaluate the effect on diagnostic performance of reducing multifocal visual-evoked potential (mfVEP) recording duration from 16 to 8 minutes per eye. Both eyes of 185 individuals with high-risk ocular hypertension or early glaucoma were studied. Two 8-minute mfVEP recordings were obtained for each eye in an ABBA order using VERIS. The first recording for each eye was compared against single run (1-Run) mfVEP normative data; the average of both recordings for each eye was compared against 2-Run normative data. Visual fields (VFs) were obtained by standard automated perimetry (SAP) within 22.3+/-27.0 days of the mfVEP. Stereo disc photographs and Heidelberg Retina Tomograph images were obtained together, within 24.8+/-50.4 days of the mfVEP and 33.1+/-62.9 days of SAP. Masked experts graded disc photographs as either glaucomatous optic neuropathy or normal. The overall Moorfields Regression Analysis result from the Heidelberg Retina Tomograph was used as a separate diagnostic classification. Thus, 4 diagnostic standards were applied in total, 2 based on optic disc structure alone and 2 others based on disc structure and SAP. Agreement between the 1-Run and 2-Run mfVEP was 90%. Diagnostic performance of the 1-Run mfVEP was similar to that of the 2-Run mfVEP for all 4 diagnostic standards. Sensitivity was slightly higher for the 2-Run mfVEP, whereas specificity was slightly higher for the 1-Run mfVEP. If higher sensitivity is sought, the 2-Run mfVEP will provide better discrimination between groups of eyes with relatively high signal-to-noise ratio (eg, early glaucoma or high-risk suspects). But if higher specificity is a more important goal, the 1-Run mfVEP provides adequate sensitivity and requires only half the test time. Considered alongside prior studies, the present results suggest that the 1-Run mfVEP is an efficient way to confirm (or refute) the extent of VF loss in patients with moderate or advanced glaucoma, particularly in those with unreliable VFs, including malingering or other "functional" forms of VF loss.

Comparing Multifocal VEP and Standard Automated Perimetry in High-Risk Ocular Hypertension and Early Glaucoma

To compare the diagnostic performance of multifocal visual evoked potential (mfVEP) and standard automated perimetry (SAP), in eyes with high-risk ocular hypertension or early glaucoma. Both eyes of 185 individuals with high-risk ocular hypertension or early glaucoma were evaluated. Subjects ranged in age from 37 to 87 (mean +/- SD: 61 +/- 11 years). Pattern-reversal mfVEPs were obtained by using VERIS (Electro-Diagnostic Imaging, San Mateo, CA) with a four-electrode array and were analyzed with custom software. SAP visual fields (SITA-standard; Carl Zeiss Meditec, Inc., Dublin, CA) were obtained within 22.3 +/- 27.0 days of the mfVEP. Stereo disc photographs and Heidelberg Retina Tomograph (HRT) images were obtained during one visit, which was within 24.8 +/- 50.4 days of the mfVEP and 33.1 +/- 62.9 days of the SAP visual field. Abnormalities on the mfVEP were defined by using a variety of cluster criteria: SAP with pattern standard deviation (PSD) P </= 0.05 or glaucoma hemifield test (GHT) outside normal limits, according to OHTS criteria (SAP-OHTS). In separate analyses cluster criteria were used to determine SAP abnormalities. Disc photographs were graded as either glaucomatous optic neuropathy (GON) or normal by two independent masked experts, and disagreements were adjudicated by a third masked expert. The overall Moorfields regression analysis (MRA) result from the HRT was used as a separate diagnostic classification. All eyes classified as "borderline" by the MRA were assigned to the normal category (i.e., "within normal limits"). Sensitivity for mfVEP or SAP was defined as the percentage of GON eyes that had an abnormality on the functional test. Specificity for mfVEP or SAP was defined as the percentage of eyes with normal optic disc structure that had normal functional test results. Disc photographs from 50% of eyes were graded GON. Both eyes were graded GON in 71 (38%) of the 185 subjects. Exactly half as many eyes were abnormal by HRT MRA. The average SAP mean deviation (MD) was +0.3 +/- 2.1 dB; average PSD was 2.3 +/- 1.9 dB. By OHTS criteria, 83 (22%) of the 370 eyes had an abnormal SAP. Depending on the cluster criterion used, the proportion of eyes with an abnormal SAP ranged from 8% to 26% and with an abnormal mfVEP, from 14% to 45%. A criterion with an estimated specificity in normal subjects of 91% resulted in 102 (28%) eyes with an abnormal mfVEP. For criteria with estimated specificities of 95% and 99%, respectively, 88 (24%) eyes and 52 (14%) eyes had an abnormal mfVEP. Agreement between SAP and mfVEP ranged from 75% to 81%. The sensitivity of SAP-OHTS to detect GON (using the disc photograph as diagnostic standard) was 29%, whereas specificity was 84%. Sensitivity of the mfVEP to detect GON, for cluster criteria with disc structure specificity between 84% and 87%, ranged from 28% to 32%. When the HRT MRA was used as the diagnostic standard, sensitivities of both functional tests to detect GON increased to 42%. The diagnostic performance of mfVEP was similar to that of SAP. However, the two modalities agreed in only approximately 80% of eyes, suggesting that they may detect slightly different functional deficits.

A Long-Term Prospective Study of Risk Factors for Glaucomatous Visual Field Loss in Patients With Ocular Hypertension

To evaluate the importance of baseline risk factors for development of glaucomatous visual field loss in patients with high-risk ocular hypertension. In the Malmö Ocular Hypertension Study, 90 patients were randomized to topical timolol or placebo treatment and observed prospectively for up to 10 years. Patients with elevated intraocular pressure (IOP) and with open angles and normal visual fields, plus at least one extra risk factor, were eligible. Risk factors were suspect disc or known disc hemorrhage, positive family history of glaucoma, pseudoexfoliation or pigment dispersion syndrome, diabetes, and mean IOP on DTC > or = 27 mm Hg. These risk factors and also the mean baseline IOP and IOP fluctuation, sex, age, and blood pressure were evaluated as predictors for development of reproducible glaucomatous visual field loss. In addition to the prospective data, post-study data were retrieved from patients' records extending maximum follow-up to 17 years. Thirty-seven patients developed glaucomatous visual field loss. Of all factors included in the analysis, disc appearance, older age, and higher IOP came out as significant risks. Suspect disc appearance increased the risk approximately three times, with a hazard ratio of 2.90, and CI: 1.34-6.30, the hazard ratio was 1.05 and CI: 1.03-1.09 per year of age, while mean baseline IOP increased the risk with 14% per mm Hg (CI: 1.01-1.28). Patients with ocular hypertension were at higher risk for developing glaucomatous visual field loss if discs were suspect, if IOP was high, and if the patient was older in age.

Diurnal IOP fluctuation: not an independent risk factor for glaucomatous visual field loss in high-risk ocular hypertension

To establish whether intraocular pressure (IOP) fluctuations contribute to the risk of developing glaucoma in patients with high-risk ocular hypertension. Ninety patients included in the Malmö Ocular Hypertension Study were examined every 3 months with office-hours diurnal tension curves and computerised perimetry. Patients were followed up prospectively for 10 years or until glaucomatous visual field loss could be demonstrated. Poststudy data were included in the analyses, extending maximum follow-up to 17 years. After 17 years, 37 patients had developed glaucomatous visual field defects. When applying univariate Cox regression analyses, mean IOP of all measurements during the prospective part of the study was a significant risk factor for developing glaucoma (95% confidence interval [CI] 1.08-1.39), while IOP fluctuations were almost significant (95% CI 0.98-1.93). When separating effects of mean IOP level and mean IOP fluctuation using Cox multiple regression analysis, only IOP level came out as significant (95% CI 1.09-1.38), and IOP fluctuations did not contribute to the risk (95% CI 0.80-1.60). IOP fluctuation depended linearly on IOP level (p<0.0001), i.e. IOP fluctuation was larger in eyes with higher IOP levels. IOP fluctuations were not an independent risk factor for the incidence of glaucomatous visual field loss in subjects with ocular hypertension.

Glaucoma management in developing countries: medical, laser, and surgical options for glaucoma management in countries with limited resources.

Most people affected by glaucoma live in developing countries. Recent trials and reports provide sound evidence for management of glaucoma. This review extrapolates relevant articles to the developing world. The predictive value of gonioscopy for progression of primary angle closure suspects (PACS) to primary angle closure (PAC) is only 22% (95% CI: 9.80-34.2). PACS are not uncommon; laser peripheral iridotomy (LPI) is neither indicated nor feasible for all. Twenty-eight and a half percent of PAC progress to primary angle closure glaucoma; the number needed to treat (NNT) for LPI to prevent progression is only 4. Laser peripheral iridoplasty controls acute angle closure glaucoma (AACG) faster than medical therapy alone. Primary lens extraction has also been suggested as treatment for AACG after control of the acute attack. A 5-year NNT for ocular hypertension (OH) of 20 is too high to allow treatment of all OH. High-risk OH and primary open angle glaucoma (POAG) have an NNT of 5 to 6 and merit treatment. Latanoprost and brimonidine are effective in lowering IOP in Asian eyes with POAG, but primary surgical therapy may be a more viable option. For cataract and coexistent glaucoma requiring filtration, trabeculectomy combined with the Blumenthal technique of cataract surgery may be as effective as trabeculectomy combined with phacoemulsification. The principles of glaucoma management should be the same the world over. Considering the paucity of resources and competing opportunity costs, countries with limited resources have to extrapolate available information in a sensible and cost-effective manner.

Perimetric point density and detection of glaucomatous visual field loss

Eighty-three patients with high risk ocular hypertension were followed between 9 and 120 months with computerized threshold perimetry every three months in a prospective clinical study. Twenty eyes developed definite glaucomatous visual field defects. Analysis of these cases showed that definite field loss was preceded by increased variability of measured threshold values. Already at this early stage up to the time when a definite diagnosis of field loss first could be made, was, in all eyes, the disturbed area large enough to cover several test locations in the standard test point pattern used during the study. The results indicate that test point density of standard central field automated threshold tests is entirely sufficient, and that early field loss is unlikely to be extremely focal in nature and able to escape detection between tested points. While early recognition of glaucomatous field loss obviously is facilitated by access to large amounts of threshold data, the current results imply that test point density is usually not a limiting factor, but that testing an eye twice using the same standard test point pattern might be as effective as if two interlocking grids were used.

Screening for glaucoma in the community by non-ophthalmologically trained staff using semi automated equipment

Eighty-nine and a half per cent of the population of a general practice over the age of 49 years were screened for glaucoma and high risk ocular hypertension requiring treatment. Screening took place using semi-automated intraocular pressure and visual field equipment operated by non-ophthalmologically trained staff. An experienced ophthalmologist examined all patients in a single blind manner to reduce false negatives to a minimum. Patients suspected of requiring treatment on the grounds of raised intraocular pressure, abnormal visual fields or suspicious optic discs were subsequently examined in a hospital clinic. Treatment criteria, as commonly practiced, were carefully defined and the sensitivities and specificities of the methods of screening used were calculated. One and three tenths per cent of the practice population were known to be receiving treatment prior to the study and a further 1.4% were found to require treatment after screening. The sensitivity and specificity of the non-contact tonometer were 91.7% and 95.6% respectively with a predictive power of 22.5% for a positive result. The mean time taken to perform the test in both eyes was two minutes. Seventy per cent of the patients with pressures over 22 mmHg in both eyes on screening were found to require treatment. The routine use of the field screener did not increase either the sensitivity or specificity of the screening process but its use in cases with raised intraocular pressure is advised to indicate the degree of urgency of the referral. An algorithm based on the results of the study is suggested when planning the use of semi-automated equipment to screen for ocular disease related to raised intraocular pressure.

The Value of Indices in the Central and Peripheral Visual Fields for the Detection of Glaucoma

We assessed 81 patients in four groups (normal, low- and high-risk ocular hypertension, and early glaucoma) with the standard Octopus G1 central visual field program in addition to two quantitative programs, PFN (peripheral field-nasal) and PFT (peripheral field-temporal), designed for this study to test the nasal and temporal periphery, respectively. Indices were calculated for each program for each subject in all groups. We then examined the behavior of the indices across the separate visual field areas within each group as well as the behavior of the indices of each field area among the different groups. We found that quantitative testing of the peripheral nasal visual field provided valuable information in the detection of glaucomatous visual dysfunction additional to that provided by quantitative testing of the central visual field. Quantitative testing of the temporal periphery was less valuable.