Clinical experiences with the use of an automated perimeter (Octopus) in the diagnosis and management of patients with glaucoma and neurologic diseases

A comparison of global indices between the Medmont Automated Perimeter and the Humphrey Field Analyzer

BACKGROUND

Two commonly used perimeters in Australia are the Humphrey Field Analyzer II (HFA) and the Medmont Automated Perimeter (MAP). Each device describes the visual field in terms of numerical values called global indices; however, these values are not interchangeable between devices. This study was designed to directly compare the global indices of HFA and MAP visual fields.

METHODS

63 subjects who had suspected glaucoma, ocular hypertension or glaucoma, or were normal controls were recruited selectively. Each patient was tested with the MAP and HFA. Global indices were then compared between tests. These included mean deviation (MD) and pattern standard deviation (PSD) from the HFA and average defect (AD) and pattern defect (PD) from the MAP.

RESULTS

The MD and PSD results were strongly correlated with the AD and PD results, respectively. The relationship between them could be described in terms of two polynomial equations: AD = 0.94+1.31(MD)+0.02(MD)(2) and PD = 2.21(PSD)-0.05(PSD)(2)-0.006. These non-linear relationships may be the result of differences in testing method (test stimulus spectrum, number of testing locations or background luminance) or differences in the way each global index was calculated.

CONCLUSION

The AD and PD results obtained from the MAP may be substituted for the MD and PSD results from the HFA after appropriate conversion.

A comparison of diagnostic protocols for interpretation of frequency doubling perimetry visual fields in glaucoma

BACKGROUND

Frequency doubling perimetry (FDP) shows good correlation with achromatic automated perimetry in the assessment of glaucoma. However, many recommended protocols lead to a significant number of false positives and negatives. Therefore, it may be difficult to identify visual field loss owing to glaucoma. We investigated the accuracy of a diagnostic protocol that only considered either temporal wedge, arcuate, or nasal step field loss on an FDP field as significant.

METHODS

Sixty-eight subjects who were glaucoma suspects, glaucoma patients or normal controls were recruited selectively. After achromatic automated perimetry and FDP visual field testing, results were compared between a conventional protocol and ones that took into account the position of FDP visual field loss.

RESULTS

If an FDP field was considered abnormal only when either a temporal wedge, an arcuate or a nasal step defect was present, the presence of a nasal step yielded the most accurate results with the least false positives (kappa coefficient=0.76) and with only minimal increase in false negatives, compared with a conventional FDP protocol (kappa coefficient=0.70).

CONCLUSIONS

Although, not statistically significant in this case, our results suggested a trend that a diagnostic protocol which considers nasal step FDP field loss significant may have a greater degree of accuracy when compared with conventional protocols and may facilitate interpretation in a clinical setting.

An evidence-based assessment of risk factors for the progression of ocular hypertension and glaucoma

PURPOSE

To critically review the existing literature concerning risk factors for progression of ocular hypertension and glaucoma to assist in assigning levels of risk for individual patients.

DESIGN

Evidence-based review.

METHODS

A panel of physicians specializing in treatment of glaucoma patients was convened to critically analyze published population-based studies of ocular hypertension and glaucoma progression. The strength of evidence in support of reported risk factors was weighed.

RESULTS

Many putative risk factors for progression of ocular hypertension or glaucoma have been reported in the literature. The risk factors most strongly supported by evidence are higher intraocular pressure (IOP), greater cup-to-disk ratio, thinner central corneal measurement, and older age. Black race does not appear to be an independent risk factor, although black individuals tend to have thinner corneas, greater cup-to-disk ratios, and higher IOP, which increase their risk. The limited number of studies in which other suspected risk factors are reported prevents drawing firm conclusions about their importance at this time.

CONCLUSIONS

Only a subset of patients with ocular hypertension will eventually develop glaucoma. Decisions regarding the implementation and extent of therapy for ocular hypertension can be difficult and require an understanding of the relative importance of risk factors for progression. This review discusses the strength of evidence supporting reported risk factors and may be useful in assessing the risk for progression of individual patients.

A visual field abnormality: ocular or cerebral cause?

The visual field can be affected by disorders involving any part of the visual pathway, from the retina to the striate cortex. The pattern of visual field damage can indicate the location of the disorder. The case is presented here of an 8-year-old girl with congenital glaucoma. Initial perimetry appeared consistent with glaucomatous field loss; however, this evolved into a homonymous quadrantanopia, indicating the presence of a cerebral lesion as the cause. Computed tomography and magnetic resonance imaging scans detected a large middle cranial fossa arachnoid cyst. Postoperatively there was resolution of the visual field defects secondary to the arachnoid cyst. The pattern of field loss was pivotal in this patient's management. Attention must be paid when caring for the patient with a chronic disease to ensure that concurrent conditions are diagnosed.

Blindness in patients with treated open-angle glaucoma

PURPOSE

To investigate blindness in patients with treated open-angle glaucoma (OAG) and risk factors for blindness.

DESIGN

Retrospective observational case series.

PARTICIPANTS

One hundred eighty-six patients seen between April and November 2000 at the University of Washington Medical Center Eye Clinic, diagnosed in 1975 or later, and treated for at least 2 years for OAG.

METHODS

Chart review with evaluation of visual acuity and visual field. Kaplan-Meier survival analysis was used to estimate the risk of blindness in one and both eyes. Variables considered to be possible risk factors for blindness were evaluated using chi-square test, t test, and Cox proportional hazards regression analysis.

MAIN OUTCOME MEASURES

Blindness, defined as visual acuity of 20/200 or worse, and/or continuous constriction of the visual field to 20 degrees or less in all four quadrants with a size III4e Goldmann stimulus or the equivalent on automated perimetry, allowing a higher threshold level on one point in one quadrant on automated perimetry.

RESULTS

The mean duration of disease was 10.2 +/- 4.9 years. Twelve patients were blind in at least one eye from OAG at diagnosis. Nineteen other patients became blind in at least one eye from OAG, and three patients became bilaterally blind from OAG. The Kaplan-Meier estimate for blindness at 15 years in one eye was 14.6%, and in both eyes was 6.4%. Noncompliance with the treatment regimen (P = 0.016) and worse initial visual field loss (P < 0.0001) were significantly associated with development of blindness. Nonwhite race was associated with blindness (P = 0.014) when all blindness, including that found at diagnosis, was considered in the analysis.

CONCLUSIONS

Bilateral blindness from chronic OAG was uncommon in this population of treated patients diagnosed in 1975 or later. Of patients with a blind eye, 39% were blind at diagnosis, and worse visual field loss at diagnosis and noncompliance were associated with development of blindness.

Automated suprathreshold static perimetry screening for detecting neuro-ophthalmologic disease

PURPOSE

To devise and evaluate a rapid, accurate, and cost-effective method of detecting neuro-ophthalmologic visual field defects.

METHODS

One hundred fifty-nine consecutive patients were evaluated with 76-point, central 30 degree automated static threshold perimetry on the Humphrey Visual Field Analyzer, as well as by a 76-point, central 30 degree suprathreshold examination with the central reference levels set at 2 or 4 dB lower than the estimated normal median central reference level adjusted for age. Six masked readers reviewed the fields. Their readings were compared with those of the other observers, as well as with the final diagnoses as determined from all available clinical information.

RESULTS

In detecting abnormality, the full-threshold 30 degree test had a sensitivity (percent of eyes with true field defects identified by the field test) of 93 percent or 99 percent (depending on whether borderline results were counted as a positive or negative test) and a specificity (percent of cases without true field defects appropriately identified by the field test) of 71 percent or 91 percent. In comparison, the 4-dB offset suprathreshold test had a sensitivity (averaged over all reviewers) of 79 percent or 87 percent and a specificity of 81 percent or 89 percent, whereas the 2-dB test had a sensitivity of 87 percent or 94 percent and a specificity of 73 percent or 85 percent. The mean duration of the suprathreshold tests was 3.5 +/- 1.0 minute, compared with 14.8 +/- 2.8 minutes for the full-threshold technique.

CONCLUSION

The central 30 degree, 76-point, 2-dB offset suprathreshold automated perimetry is more rapid and nearly as effective as the full-threshold test in detecting visual field abnormalities due to neuro-ophthalmologic disease. More quantitative, full-threshold perimetric strategies should be used in all equivocal cases and to follow progression of established disease.

Automated perimetry detects visual field loss before manual Goldmann perimetry

PURPOSE

To determine if automated perimetry detects visual field defects before manual Goldmann perimetry.

METHODS

Subjects with ocular hypertension without field loss on detailed manual perimetry were followed prospectively with annual automated and manual perimetry. Subjects with field loss on manual perimetry were age-matched post hoc to subjects who did not have field loss. The automated fields 1 year before the development of field loss on manual perimetry were compared between the two groups. Subjects were recruited from ophthalmologists' offices, eye clinics, and a population-based glaucoma survey in the Baltimore area. Abnormal results detected on the Humphrey Field Analyzer were defined using the glaucoma hemifield test, mean defect, and corrected-pattern standard deviation.

RESULTS

Forty subjects who had field loss during 8 years of follow-up were compared with 145 control subjects with ocular hypertension who did not have defects. Seventy-five percent of converters had abnormal results of the glaucoma hemifield test 1 year before field loss on manual perimetry, whereas 22% of controls had abnormal results of the glaucoma hemifield test (odds ratio, 13.4). The odds ratio of field loss developing on manual perimetry within 12 months was 3.3 for those with borderline results of the glaucoma hemifield test relative to the control subjects. The odds ratio was 6.0 for corrected-pattern standard deviation (P < 0.05) and 3.9 for mean deviation (P < 0.05).

CONCLUSIONS

Those with field loss on manual perimetry were more likely to have had an abnormal automated field 1 year before conversion than those who did not convert. However, 22% of subjects in whom definitive field loss did not develop on manual perimetry during the study had abnormal automated fields at one visit and 15% had abnormal automated fields on two consecutive visits.

Pituitary adenomas: automatic static perimetry and Goldmann perimetry. A comparative study of 345 visual field charts

In a series of 81 cases of pituitary adenoma 345 charts of visual field performed with static automatic perimetry (AP) on the Vision Monitor and Goldmann perimetry (GP) were compared. Generally both methods were equivalent in the detection of chiasmal compression. The charts were divided into two groups: (A) 208 charts and (B) 137 charts according to the number of isoptres investigated: two (V4, 112) or three (V4, 112, 12). In group A the AP was more often altered than the GP, and the difference was statistically significant (p less than 0.001). In group B the GP seemed more effective, but the number of questionable cases was greater and the difference was not statistically significant. When the most internal isoptre of GP was outside the central 30 degrees, AP was more often abnormal (29%) than GP (2.2%), and the difference was statistically significant (chi 2, p less than 0.001). Within the central 30 degrees the GP seemed more often to be altered (23% of cases) than the AP (19.4%), but one-third of the cases were questionable. Within the central 30 degrees both techniques gave identical results and there was no statistically significant difference. The discrepancies between both static and kinetic techniques are an argument for their complementary use.

Computerized perimetry in glaucoma management

The present article discusses the role of computerized perimetry in the management of patients with suspect and manifest glaucoma. The value of visual field examination is compared to that of inspection and photography of the optic disc and to some extent to retinal nerve fibre layer photography. Computerized perimetry is related to standard manual visual field examination. Guidelines are offered for the choice of test programs and for the interpretation of results.

Full threshold versus quantification of defects for visual field testing in glaucoma

Nineteen glaucoma patients, 17 ocular hypertensives, and 16 normal subjects underwent visual field testing on the Humphrey Field Analyzer using two programs: full threshold (thresholding of all test points with double-crossing technique) and quantification of defects (thresholding only points that deviated more than 6 dB from a presumed normal retinal contour). The purpose of the study was to compare the diagnostic value of information gained by the latter, less time-consuming test with that of the full threshold procedure. The average time requirement per eye was 13 min 11 s for full thresholding and 4 min 22 s for quantification of defects. Of the 104 sets of fields, the diagnosis was at variance in 18. The differences were most often due to shallow defects in otherwise normal fields or shallow defects surrounding deeper scotomas that had been detected by both programs. The shallow defects placed the fields in more advanced diagnostic categories and were all detected with the full threshold technique.

Threshold perimetry and the diagnosis of glaucoma

Visual field examinations are one of the commonest, presumably most sensitive practical indices of optic nerve dysfunction in glaucoma. Given the difficulties in training and retaining good technicians, and presumed vagaries of the Goldmann-type isopter examination technique, interest has turned to computer-controlled automated suprathreshold and threshold static perimetry. Despite the enthusiasm for these approaches, we lack rigorous tests of their value, criteria of abnormality and progressive deterioration, and even normal standards. These important issues are now being addressed. In the interim ophthalmologists must be cautious in their use and interpretation.

Screening for glaucomatous visual field loss with automated threshold perimetry

We examined 27 glaucomatous eyes and 154 normal eyes with automated threshold perimetry. Previously suggested algorithms for detecting mild to moderate glaucomatous visual field loss, primarily by comparing the sensitivity of corresponding clusters of points above and below the horizontal meridian, yielded results remarkably consistent with those of our earlier series: 93% (25 of 27) of abnormal and 88% (135 of 154) of normal eyes were correctly identified. Excluding unreliable examinations increased specificity from 88% to 93%. Test duration was similar to results with the Field Analyzer's older, purportedly slower operating system.

Perimetric findings in pseudotumor cerebri using automated techniques

The authors obtained automated static threshold visual fields in 44 eyes of 22 patients with pseudotumor cerebri. Severe defects were found in 9% and moderate defects in 68%. The pooled incidence of three recent studies using manual kinetic techniques also demonstrated 9% severe defects, but only 34% of eyes demonstrated moderate loss. In 20 of 44 eyes, the papilledema was felt to be severe or atrophic. In none of these eyes was a normal field obtained. Visual field defects in pseudotumor cerebri appear to be more common than previously thought.

Early detection of glaucomatous damage. I. Psychophysical disturbances

In summary, automated perimetry and other psychophysical tests currently provide the most sensitive, reliable and reproducible means of clinically detecting early glaucomatous changes. Compared to optic disk and nerve fiber layer evaluation, such procedures provide a consistent, quantitative method of distinguishing between early abnormalities and normal variations.

Quantitative office perimetry

This study presents a preliminary comparison of six commercially-available automated threshold static parameters, consisting of three projection perimeters (Humphrey Field Analyzer, Squid, and Octopus 500) and three light-emitting diode (LED) perimeters (Dicon 2000, Fieldmaster 50, and Digilab 350). Eighteen individuals were included in the study: 6 normal observers (31-58 years old), six patients with glaucomatous field loss in both eyes (55-70 years old), and six patients with neuro-ophthalmologic or retinal visual field abnormalities in both eyes (12-61 years old). Three aspects of quantitative testing were evaluated: (1) the patients' and normal observers' acceptance and subjective impressions of the test procedure; (2) the technician's ease of operating the device and related tasks; and (3) practitioner-oriented considerations such as test-retest reliability, comparability of test results and testing time. Our results showed that no device was clearly superior to the others in all respects. Patients were most favorably impressed with the Octopus 500, Squid, and the Fieldmaster 50, while technician impressions were most favorable to the Humphrey Field Analyzer and the Squid. The projection perimeters (Humphrey Field Analyzer, Squid, and Octopus 500) were the easiest to perform cross-comparisons of test results, although there was considerable variation in the clarity of data interpretation from one case to another. Test-retest reliability and the time of testing varied among the six automated perimeters.

Diurnal intraocular pressure. Correlation to automated perimetry

Patients referred to a centralized glaucoma laboratory obtained intraocular pressure measurements every two hours from 5:00 am to 3:00 pm. Analysis revealed 400 eyes with visual field defects and 400 eyes without visual field defects as determined by Octopus perimetry of the central 20 degrees. The diurnal variation in intraocular pressure was 6.2 mmHg +/- 3.6 for those with visual field defects and 5.5 mmHg +/- 2.7 for those without visual field defects. There was no statistical significance in the mean diurnal variation between the two groups (P = 0.91). The highest intraocular pressure tended to occur at either 5:00 am to 7:00 am or 11:00 am to 1:00 pm in both groups. The lowest intraocular pressure tended to occur between 7:00 am to 9:00 am or 1:00 pm to 3:00 pm in both groups. No significant differences were noted in the distribution between the two groups with regard to the time of the highest or lowest intraocular pressure. In the group with visual field defects, 30% had an intraocular pressure of less than 23 mmHg and 23% had an intraocular pressure of greater than or equal to 23 mmHg at all five time periods.

A clinical comparison of visual field testing with a new automated perimeter, the Humphrey Field Analyzer, and the Goldmann perimeter

Automated threshold static perimetry with the Humphrey field analyzer and kinetic and suprathreshold static perimetry with the Goldmann perimeter were performed on 171 eyes: 69 with glaucoma or ocular hypertension, 69 with "neurologic" disorders, and 33 normal. The two fields were similar or differed only slightly in 78% of eyes overall and in 88% when both fields appeared reliable. In general, defects were slightly more extensive using the Humphrey than the Goldmann perimeter. In 21% of the eyes with glaucoma or ocular hypertension, defects were found with the Humphrey perimeter that were not present with the Goldmann perimeter. Patient fixation was more difficult to maintain on the Humphrey than Goldmann perimeter. Poor fixation accounted for 9% of the automated fields being inadequate whereas only 2% of the manual fields were inadequate. The results indicate that the Humphrey Field Analyzer is capable of reliably detecting and quantitating visual field defects.

The qualitative comparative analysis of the visual field using computer assisted, semi-automated and manual instrumentation: II. Statistical analysis

A comparative evaluation of the Octopus automated perimeter (Programmes 21 and 31), the Goldmann Bowl perimeter, the Bjerrum Screen and the Friedmann VFAs MkI and MkII was carried out on a heterogeneous sample of 75 patients. The results for the sample as a whole were analysed statistically in terms of the scoring system developed by Flanagan, Wild, Barnes, Gilmartin, Good and Crews (1984a). Statistically significant differences between the instruments were found at each of the 4 levels of analysis.

Automated and manual perimetry-a six-year overview. Special emphasis on neuro-ophthalmic problems

Between August 1976 and September 1982, more than 34,000 manual and automated visual fields have been analyzed in the Department of Ophthalmology, University of California, Davis. Approximately 27% of these tests consisted of manual kinetic visual fields performed on the Goldmann perimeter, while 73% were conducted using automated perimetry. Automated testing alone, or a combination of automated perimetry and manual kinetic testing (Goldmann perimeter) was usually employed to monitor progression or regression of visual field loss. This paper provides an overview of two aspects of automated suprathreshold static perimetry that have not been emphasized in our previous studies: (1) methodologic difficulties and problem patients in automated suprathreshold static perimetry, and (2) examples of automated suprathreshold static perimetry in neuro-ophthalmologic patient populations.

Comparative material on automated and semiautomated perimeters-1983

In reviewing all the responses from the private practitioners and clinicians in Departments of Ophthalmology throughout the United States and Canada, it would appear that the majority of individuals are quite happy with the automated perimeters they have purchased. Clinicians should be aware that this is a rapidly changing field and several devices which were previously available are no longer being manufactured. In addition, because of the competition which has recently developed in the automated perimetry industry, prices are continuing to come down. Some practitioners have been unhappy with the fact they paid a higher price for a device which is currently selling at a lower price. However, a similar phenomenon has happened in the computer world and is to be expected as competition increases. The major problems which seem to be of concern to all ophthalmologists, are the difficulty in interpreting data and the management of the data. We believe one of the major frustrations of all practitioners using automated perimeters relates to the fact that this is a totally new technique, which requires time and practice to gain familiarity. In general, it would appear that most of the practitioners have been happy with the service provided by various companies, although there are a few exceptions. Read the enclosed responses and develop your own conclusions. We hope you find the information useful.

Diagnostic strategies in the management of unexplained visual loss. A cost-benefit analysis

In the investigation of visual loss from anterior visual pathway disease, it is imperative to differentiate the infrequent compressive from the much more common noncompressive lesions. To determine how relatively low-cost, risk-free, but error-prone visual field examination (VF) and high-cost, risk-prone, but accurate CT Scan (CT) and cerebral angiography (Angio) can be cost-effectively utilized to solve this diagnostic problem, the authors have developed a decision making model for the analysis of three management strategies. The visual field examination precedes and determines the use of neuroradiologic studies in Strategy A (VF-CT-Angio), whereas it follows the neuroradiologic studies in Strategies B (CT-VF-Angio) and C (CT-Angio-VF). The visual field-determined strategy (A) proved most cost-effective, based upon an estimated 6% or lower relative prevalence of chiasmal compressive lesions, a negligible risk in delaying their diagnosis, and a sensitive method of visual field examination. At a visual field sensitivity to chiasmal defects of 84% and a specificity of 88%, Strategy A annually saves $4 million over Strategy B and $27 million over Strategy C. At lower levels of perimetric accuracy, Strategy B is the most cost-effective approach. Strategy C is never cost-effective.

Changes of glaucomatous field defects. Degree of accuracy of measurements with the automatic perimeter Octopus

The analytical programme Delta was used to determine longterm fluctuation and accuracy of measurement of the programme 31 of Octopus when used on glaucoma patients. Programme 31 examines the 30 degrees field. The test locations are arranged in a square grid with 6 degrees resolution. The programme Delta determines and compares 1) the disturbed area in %; 2) the total loss, the total sensitivity being around 2000 dB; 3) the loss in dB per mean number of disturbed points. Thirty-two eyes of 22 patients with established glaucomatous field defects were examined twice within two to six days and two months later again twice. The size of the disturbed area served for classification of our sample into three groups: 1st group: disturbed area 1-33%; 2nd group: disturbed area 34-66%; 3rd group: disturbed area 67-100%. Long-term fluctuations and accuracy of measurement could be determined as respectively follows: 1) Disturbed area between 0.7 +/- 8% in group 3 and 1.7 +/- 13% in group 2. 2) The total loss increases proportionately to the disturbed area and was 4.9 +/- 29.2 dB in group 1 and 31.8 +/- 82.4 dB in group 3. 3) The total loss per mean number of disturbed points was 0.5 +/- 2 dB in group 1 and 0.3 +/- 1.2 dB in group 2. This signifies that if the learning effect is over, changes of more than 2 dB, especially if several adjacent points are affected, are a significant loss. The learning effect, as determined in an earlier study, may go up as high as 2 dB per point.