Search

Automated perimetry is a method which has largely proved its utility in the diagnosis and follow-up of certain ophthalmic pathologies1–3, as well as its functional repercussions4–6. We carried out a randomized prospective study to assess the variations in the retinal sensitivity with automated perimetry in two groups of population affected by a macular epiretinal membrane. We performed a vitrectomy with a membrane peeling in one group, while we kept the other group under observation.

High internal reflectivity and a predominantly irregular structure on standardized A-scan were the classic acoustic features encountered at first examination in nine patients with unilateral ophthalmoscopic evidence of choroidal nevus elevated from 1.6 to 3.5 mm. In all patients but one with a 3.5 mm elevated nevus, periodic fluorescein angiography and automated perimetry findings were consistent with the diagnosis of choroidal nevi located at the posterior pole or in the mid periphery. Slight or no growth was observed echographically during the follow-up (seven months to seven years) except in one eye with a solid pigmented lesion which progressively grew 1 mm and showed low reflectivity without spontaneous vertical movements or evidence of melanoma at ancillary examinations. In two other eyes the internal reflectivity of the choroidal nevus decreased gradually from high to medium. The differentiation between choroidal nevus and melanoma with standardized echography and the existence of a possible histologically intermediate lesion (‘nevoma’) are discussed.

While it is accepted that the macula represents a peak of sensitivity, normal population values and ranges are poorly defined. Now that the assessment of macular sensitivity with automated perimetry is being performed clinically to monitor conditions such as senile macular degeneration and cystoid macular oedema following cataract surgery, a better definition is desirable.

Among the static-kinetic programs, the Armaly-Drance strategy is universally accepted as a valid perimetric test for detecting early glaucomatous visual field defects. In our opinion, this program can be improved, thanks to recent progress in automated perimetry. The features of the Armaly-Drance program that can be modified are the following: Distribution of the tested points in the paracentral area: a more even arrangement of these points is desirable. Characteristics of the stimulus: individual threshold related stimuli can make the exam more accurate. Kinetic trajectories in the nasal v.f.: a greater number of kinetic stimuli can increase the probability of nasal step detection. Stimuli presentation sequence: a random stimuli presentation in recommended.

In 144 subjects (normals, ocular hypertensives, other glaucoma suspects and glaucoma patients) we investigated whether the fatigue-phenomenon that occurs during prolonged static threshold testing could be a useful diagnostic tool. On average the glaucoma patients had higher fatiguability than the other groups, but there was a large overlap between the 4 groups of subjects. We did not find a relation between fatigue and pathologic condition within the visual field. It seems unlikely that fatigue testing will become important for the detection of early glaucomatous damage.

The Scoperimeter is an experimental automatic perimeter based on an oscilloscope controlled by a micro-computer. This report describes the programs developed for various perimetric tests. The screening program does a quick detection and a limited assessment of defects. The threshold program measures thresholds with a resolution of six degrees. A further examination of parts of the visual field can be done in segments, in the central two degrees or along meridians. Also the concepts of a more statistical approach are discussed.

Results of automated perimetry by means of the Fieldmaster-200 and Fieldmaster-225 in 2500 flying subjects are described. In 22 subjects (approx. 1%) a serious visual field defect was found. In 12 subjects aspecific defects were found. Since the visual field is of utmost importance in aviation, while mass conventional screening is not possible, it is suggested that use should be made of automated perimetry testing.

The Peritest is a computer-assisted perimeter which purposely offers the possibility of both automatic and semi-automatic examination modes. A fast multiple-stimulus screening is possible next to extensive automatic assessment. The instrument uses LEDs for the 206 stimuli, of which 151 are located within 25° eccentricity. The examination strategy uses the system of threshold-related suprathreshold presentations. The assessment phase may use 0.2 or 0.6 log unit steps. The progress of the examination can be followed on a LED monitor. The experience of over 800 examinations with the Peritest has shown that the instrument is able to do a relatively quick examination with reproducible results. The examination time varies from 4 minutes for a semi-automatic screening to 15 minutes for a completely automatic detection and assessment. The detection rate is better than that of classical kinetic perimetry. This is demonstrated by the fact that 70% of early glaucomatous defects which are usually overlooked by kinetic perimetry are detected. The non-interpolated grey scale printout on a special chart demonstrates the configuration of defects satisfactorily and makes comparison with classical kinetic perimetry possible. The defect volume in separate areas of the visual field or in the whole visual field can be easily expressed in numbers. With some precautions this could be used for describing changes in the visual field.

The new computerized Autoperimeter has now been programmed to include the Functional Relative-Value Scale. This combination simultaneously performs automated perimetry and ergoperimetry: it plots the field, either monocular or binocular, and instantly prints the Functional score. The score is called ‘functional’ because it measures more than merely area; it assesses the total field’s usefulness and expresses it in percent or simple fraction — as does the Snellen Scale for central acuity. Thus, consultants for industry or government now have a standard scale to help determine job fitness, driver safety, social security disability, worker’s compensation, etc and to do this automatically, quickly, impersonally and as accurately as subjective testing will permit.

By examination with the automated perimetry system OCTOPUS in Diabetic Retinopathy (DR) characteristic changes in the visual field show up in form of flecked, partially confluent relative scotomas. They can be correlated to areas of capillary non-perfusion. The average decrease of light sensitivity in the different stages of DR was ascertained. It ranges between 1.4dB in the stage I and 6.7dB in the stage IV. It is remarkable, that even in beginning DR the loss of retinal function is greater in the middle periphery than in the central area. This becomes more distinct in advanced stages of DR and especially in the proliferative form.

Modern perspectives of cataract medical therapy have induced researchers to study objective methods for the evaluation of lens transparency. Visual acuity determination, slit-lamp examination, photographic and densitometric methods have poor reliability. In this study computerized static perimetry was tested and our strategy was based on two automatic perimeters: Peritest (Rodenstock) and Perikon (Optikon). Peritest was very useful in the static analysis of cataract-induced threshold changes in the central visual field. Static meridional perimetry by Perikon was utilized to study peripheral threshold changes. This method, tested in 50 patients (25 under therapy with anti-cataract drugs) appeared to be reliable, rapid, easily standardized and well-accepted by patients.

It has been demonstrated that in Parkinson’s disease VEP latency is frequently abnormal. The aim of this paper is to evaluate the possible existence of visual correlate to VEP changes in Parkinsonians. Therefore in the same group of patients VEP have been compared with the results of automated perimetry (Perikon and Peritest) and chromatic sense analysis (Farnsworth 100 Hue Test). Preliminary results indicate that the considered parameters are correlated. To establish if the visual changes are specific, the results obtained in the Parkinsonians are compared to those of a matched control group.

The spatially adaptive program SAPRO, written for the Octopus 201, has been applied in a study of angioscotoma. A mosaic of the interpolated results of 34 separate examinations performed over a one-month period on angioscotoma within a normal visual field region subtending approximately 20° on both sides of the macula is shown. This is compared on the one hand with the fundus picture (inverted) of the same subject’s eye. The agreement is remarkable. Also shown is a similar mosaic showing just the locations measured. The time saved by measuring with higher resolution only the areas of interest is apparent. Examples of program use as well as some of its features are also included.

Conventional psychophysical studies have used a variety of analysis methods for determining thresholds from staircase procedures. In general, these methods demonstrate very good agreement in their threshold estimates when a large number of stimulus presentations (50–200) are employed. However, staircases in automated perimetry typically employ between 4 and 12 stimulus presentations. The present study compared five different analysis procedures (average of all presentations, median of all presentations, mode of all presentations, average of reversals at the minimum step size, and the value of the last seen target) for staircases used in automated static perimetry. Test-retest data for 14 normal eyes and 14 eyes with moderate visual field loss were obtained using a 6–3–3 staircase procedure on the Digilab 750 automated perimeter. Threshold estimates were determined for the five analysis procedures for 66 target locations in each visual field (blind spot region excluded). All of the analysis procedures exhibited good agreement in threshold estimates, except for the ‘last seen’ procedure, which was approximately 1.5 dB different from all other threshold estimates. The average of all stimulus presentations and the average of reversals at the minimum step size both displayed the best test-retest reliability. This was a small but consistent effect, suggesting that these staircase analysis procedures should be employed to improve the test-retest reliability of automated perimetry tests.

We analysed the results of visual field examinations, measured repeatedly over time. In 40 eyes of 11 normal subjects, 8 patients with ocular hypertension and 21 glaucoma patients the measurements were performed with the Scoperimeter. In 35 eyes of 18 glaucoma patients the measurements were performed with the Friedmann Visual Field Analyser. We studied the Long-term Fluctuation (based on the standard deviation of differences between sessions) of three visual field parameters: Mean Threshold, Individual General Sensitivity and Mean Defect. We found that the long-term fluctuation of the Mean Threshold was around 1.5 dB (sd). We broke the Mean Threshold down in two components: the Individual General Sensitivity and the Mean Defect. The Mean Defect proved to be the most stable parameter over time. Thus, for assessment of the pathological state of the visual field the Mean Defect seems to be the better choice.

Selective retests were compared to global retests using a large pool of visual fields measured with program JO on the Octopus automated perimeter. The results of this investigation are that in selective retests, the mean sensitivity (MS) is increased, while the number of pathological test locations (NP) is decreased. To obtain as objective an impression as possible of a visual field, therefore, selective retests should be avoided. It is better to retest every test location or none.

To evaluate the reliability of automated perimetry results, fluctuation is one of the most important factors. This fluctuation is, however, influenced not only by the cooperation of the patient but also by the disease state and the defect depth. To estimate patient cooperation, an additional test is necessary. In Octopus perimetry, this has always been performed with the so-called catch trials. In a large series of visual fields, we analyzed the rates of false responses in catch trials and the factors influencing them.

The shape of the normal visual field and the distribution of threshold values was examined in a normal population and a population of glaucoma patients. Our goal was to optimize the determination of the reference field used in our evaluation program for visual fields. We found true interindividual differences in the gradient of sensitivity of the normal visual field. These findings emphasize the importance of individual determination of the reference field. For our normal as well as our glaucoma population the standard deviation of this variation was estimated to be 0.09 dB/degree.

The overall features of optimal examination strategies applied to computer-assisted perimetry are described. Emphasis is placed on the concepts of specificity and adaptivity which result from the necessity to obtain the greatest information gain within the amount of time available to the clinical examination. Implications for computer hardware and software are derived, including the programmability and interactive control of examination protocols.

Until a few years ago, microprocessors had several disadvantages in comparison with minicomputers: they were not fast process unit; they could implement only small sets of instructions; they could not reach a high number of memory cells; they implemented algorithms of modest complexity; they could control a limited number of peripherals, but had the advantages of very reduced overall dimensions and of reasonable costs.

We evaluated the screening ability of a central screening program of the Competer 350 in 60 patients (120 eyes) with ocular hypertension (OH) and 40 patients (70 eyes) with primary open angle glaucoma (POAG) in various stages of development. A control group of 40 normal subjects (80 eyes) was also taken into consideration.

Chronic glaucoma causes visual field defects and in some cases an increase in the latency of pattern evoked visual potentials (P E P). To assess the contribution of field defects to the latency increase in PEP we have reexamined 16 glaucoma patients out of a group of 27 whose PEP had been recorded two years before (Huber and Wagner 1978). PEP measurements and visual fields measured by automated static perimetry (Octopus) where compared. A significant increase in PEP latency could only be demonstrated in the presence of a relative central scotoma. The depth of the relative scotoma is related to the increase in latency. Peripheral field defects do not affect the PEP latency as a small central island of vision with normal sensitivity is sufficient to produce a normal PEP. A large visual field with reduced central sensitivity can however result in a large latency increase. Over a period of two years the shape of the individual PEP is constant. The latency increase in glaucoma thus represents a differential diagnosis of increased PEP latency in the context of neurological diseases. PEPs are not an adequate method for the detection of early glaucoma as the sensitivity of the visual field’s center can be unaffected for a long time in this disease.

In order to detect and follow up early functional defects in glaucoma, we are concerned with small changes which occur in quantitative perimetry. Changes due to a disease state must be differentiated from artificial changes, for example, those due to influence of drugs.