The use of antimetabolites with trabeculectomy: a critical appraisal.

PURPOSE: To examine why most ophthalmologists routinely use mitomycin C or 5-fluorouracil (antimetabolites) in association with filtering surgery for glaucoma. METHODS: Critical analysis of seven medical, social and economic trends. RESULTS: The rapid acceptance of the adjunctive use of antimetabolites at the time of filtration surgery may be explained by reasons other than anticipated increase in the "success" of glaucoma surgery. CONCLUSION: The use of antimetabolites in conjuction with filtering glaucoma surgery may be at least partially a consequence of changing medical-social-economic factors, rather than solely a desire on the part of physicians to improve the "success" of glaucoma surgery. This may indicate a need to reevaluate the proper place of antimetabolites in association with filtration surgery.

Diffuse and localised visual field defects to automated perimetry in primary open angle glaucoma.

The occurrence of generalised or diffuse visual field depression in primary open angle glaucoma (POAG), in contrast to the presence of characteristic localised defects, is controversial. The frequency of diffuse visual field loss to automated static perimetry in the early stages of POAG was determined and compared with the frequency of localised defects. Twenty-five eyes of 25 consecutive POAG patients who met the selection criteria were tested on the Humphrey Visual Field Analyser with the Central 30-2 Threshold Test. Patients' mean age was 68 years. All eyes had visual acuity better than 6/9 with correction, refractive error of less than +/- 7 dioptres, no media opacities and normal pupils (3-6 mm). For all eyes, the frequency of abnormality on the STATPAC Total Deviation (TD) and Pattern Deviation (PD) plots were determined for all individual test points. Mean values and standard deviations were compared. The TD plots represent a composite of both diffuse and localised visual field depression, while PD plots are intended to reflect localised field defects. The frequency of involvement of the test points on the TD plots was higher than on the PD plots (mean +/- SD: 41.5 +/- 11.2% vs 27.5 +/- 10.9%) for all presenting defects. When only deep defects (STATPAC p < 1% and p < 0.5%) were evaluated, TD involvement was still more frequent than the PD (20.1 +/- 9.4% vs 13.2 +/- 7.2%). The topographical pointwise incidence of pure generalised sensitivity loss in the visual field was less frequent when only deep defects were taken into consideration (6.9 +/- 5.7%), and the incidence increased progressively with the inclusion of intermediate and shallow field defects (9.6 +/- 6.8% and 14.0 +/- 8.4% respectively). A component of diffuse sensitivity depression is present at all significant levels of visual field loss in glaucoma. This component of generalised loss decreases as the depth of the field defects increases. This finding suggests that early diffuse field loss converts into well-defined pattern defects at later stages.

Topographical reproducibility of small scotoma using computerised dynamic fixation target.

The computer assisted dynamic fixation technique uses the patient's eye movements to locate the test stimulus in the central visual field in relation to a randomly meandering fixation target. The patient looks at the moving fixation target on a high resolution monitor and tries to keep it inside a circle using a joystick. The stimuli are presented at predetermined locations in a seemingly random manner and the awareness of the stimuli is registered by the patient pressing the joystick button. That novel fixation maintenance technique has been combined with suprathreshold static light offset (dark-on-bright-light decrement) stimuli created on a cathode ray tube and used in mapping of the physiological blind spot in 10 healthy eyes. Each eye was examined twice with the same test program in order to document the repeatability of the results. On two consective tests, the physiological blind spot measured an average of 5.7 degrees horizontally and 6.4 degrees vertically, using 15% (17 dB) contrast, 16 mm2, single intensity offset stimuli. The moving eye method and the light offset stimuli, on repeated testing, yielded an average topographical reproducibility rate of 73% in mapping of the scotomas, with an average of 1.4 degrees and 0.6 degree variability in the vertical and horizontal dimensions of the blind spot respectively.

The effect of refractive blur on the detection sensitivity to light offsets in the central visual field.

Detection sensitivity to light decrements created on a cathode ray tube was measured along the nasal horizontal meridian of the central visual fields of 5 normal subjects. Decremental (light offset = negative contrast = dark-on-bright) static stimuli were presented at 6, 12, 18, 24 and 30 degrees eccentricity. Detection thresholds to rectangular stimuli of both 4 and 16 mm2 (Goldmann equivalent size III and IV, respectively) were determined with ascending staircase single-crossing technique under various Snellen visual acuity levels. Detection sensitivity diminished with increasing amounts of plus lens-induced refractive blur. One log unit decrease in visual acuity resulted in elevation of detection thresholds for an average of 3.8 contrast decibels (dB) using size III offset stimuli. The effect of blur was less with size IV offset stimuli which resulted in an average of 0.9 dB elevation in detection thresholds. The larger size decremental stimuli provided a wider dynamic range, less interindividual variation in stimulus visibility and more resistance to refractive error than those obtained with the smaller size stimuli.

A comparison of automated static dark stimuli with the Humphrey STATPAC program in glaucomatous visual field loss.

Visual field examination is conventionally performed with bright stimuli on a dark background. Dark stimuli on a bright background, however, may provide different information as light increases and decreases are subject to parallel processing in the visual pathway. Twenty five eyes with primary open angle glaucoma and visual field loss were examined with the Humphrey visual field analyser thresholding program 30-2 and the computer assisted moving eye campimeter (CAMEC) using static dark stimuli at four different Weber contrast levels of -10 (n = 9), -22 (n = 25), -37 (n = 14), and -76% (n = 25) on a cathode ray tube with a background luminance of 10 cd/m2. The cumulative results obtained with STATPAC 'pattern deviation' empirical probability maps and the results from each contrast of the dark stimulus at identical test locations were compared at eccentricity annuli bands of 4-9, 10-20, and 21-28 degrees. Dark stimuli of lower contrast provided higher abnormal point detection rates. Furthermore, visual field defects to the low contrast dark stimuli were more extensive than those to the luminous stimuli. In conclusion, dark stimuli allowed the delineation between glaucomatous field defects and the normal regions in the central visual field.

Representation of the visual field in the occipital striate cortex.

The representation of the field of vision in the human striate cortex is based on the Holmes map in which about 25% of the surface area of the striate cortex is allocated to the central 15 degrees of vision. Following the introduction of computed tomography of the brain, the accuracy of the Holmes map was apparently confirmed by clinical/radiological correlation, but a revision has been proposed by Horton and Hoyt based on a magnetic resonance imaging study of three patients with visual field defects due to striate lesions. They propose that the central cortical representation of vision occupies a much larger area. This study reviews the perimetric and imaging findings in a larger series of patients with striate cortical disease and provides support for the revised representation. The clinical phenomenon of macular sparing and its relation to representation of the macula at the occipital pole is also discussed.

Detection sensitivity to light offsets is abnormal in glaucomatous visual field.

The detection thresholds in the central visual fields of glaucomatous (n = 21), ocular hypertensive (n = 21) and normal (n = 13) individuals were tested with both light decrements (offsets = dark spots) on a cathode ray tube (CRT) and light increments (onsets = bright spots) on a bowl projection perimeter. Both types of stimuli were of equal surface area (Goldmann size IV = 16 mm2) and duration (200 milliseconds) on a 10 cd/m2 background intensity. Computerized threshold testing with light offsets on CRT could document the glaucomatous visual field loss with high accuracy and might indicate early glaucomatous visual field loss missed by the conventional light onset stimuli.

Visual field interpretation with a personal computer based neural network.

The Computer Assisted Touch Screen (CATS) and Computer Assisted Moving Eye Campimeter (CAMEC) are personal computer (PC)-based video-campimeters which employ multiple and single static stimuli on a cathode ray tube respectively. Clinical studies show that CATS and CAMEC provide comparable results to more expensive conventional visual field test devices. A neural network has been designed to classify visual field data from PC-based video-campimeters to facilitate diagnostic interpretation of visual field test results by non-experts. A three-layer back propagation network was designed, with 110 units in the input layer (each unit corresponding to a test point on the visual field test grid), a hidden layer of 40 processing units, and an output layer of 27 units (each one corresponding to a particular type of visual field pattern). The network was trained by a training set of 540 simulated visual field test result patterns, including normal, glaucomatous and neuro-ophthalmic defects, for up to 20,000 cycles. The classification accuracy of the network was initially measured with a previously unseen test set of 135 simulated fields and further tested with a genuine test result set of 100 neurological and 200 glaucomatous fields. A classification accuracy of 91-97% with simulated field results and 65-100% with genuine field results were achieved. This suggests that neural networks incorporated into PC-based video-campimeters may enable correct interpretation of results in non-specialist clinics or in the community.

Glaucomatous optic neuropathy causes sensitivity loss to light offsets in the visual field.

The functional integrity of the 'on' and 'off' neurovisual pathways has been examined in the central visual fields of normal (n = 13), glaucomatous (n = 21) and ocular hypertensive (n = 21) individuals. The detection thresholds to light increments (onsets = bright spots) and light decrements (offsets = dark spots) on a uniform background were determined in each eye and the visual field scores were calculated for each of the subjects. Light offsets detected the presence of glaucomatous visual loss and also revealed significant early visual deficits which were missed by the conventional light onset stimuli. This study indicates that 'off-pathway' evaluation with light offsets can be used for the assessment of the functional integrity of the visual system and may reveal sub-clinical early glaucomatous optic neuropathy.

Clinical evaluation of a multi-fixation campimeter for the detection of glaucomatous visual field loss.

The multi-fixation glaucoma screening chart, which uses the oculokinetic perimetry (OKP) technique, is a hand-held tangent screen with a central black test stimulus on a white background and a series of 26 numbered fixation targets arranged around the stimulus at various locations. When the numbers on the chart are read by the patient from 40 cm distance, the test stimulus passes through the relevant parts of the central visual field which are most vulnerable to glaucomatous damage. The test is positive (that is, abnormal) if at least one fixation number is associated with consistent disappearance of the stimulus. The OKP test was performed in 222 eyes of 126 glaucoma patients (aged 16-91 years) and 186 right eyes of 186 normal individuals (aged 19-86 years) using a 1.5 mm diameter stimulus. A further 144 eyes of 88 glaucoma patients (aged 60-85 years) and 31 right eyes of 31 normal individuals (aged 60-85 years) were tested with a 3 mm diameter stimulus. All eyes were also tested with conventional perimetry and the results of the conventional perimetry were categorised according to the Aulhorn-Karmeyer classification by four ophthalmologists without any knowledge of the OKP results. When the 1.5 mm stimulus was used, a true positive OKP result was obtained in 45% of eyes with relative scotomas, 81% of eyes with small absolute scotomas separate from the blind spot and 100% of eyes with more severe visual field defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Computerised perimetry with moving and steady fixation in children.

The computer assisted moving eye campimeter (CAMEC) maintains the patient's interest and fixation by using a moving fixation target which must be tracked by the patient using a joystick for the test to proceed. In this study, 32 children were examined with the blind spot test programs of both CAMEC and the Dicon Auto-Perimeter. Among those who completed both tests the blind spot was detected in 18 eyes (75%) by the Dicon Auto-Perimeter and in 24 eyes (100%) by CAMEC. The mean CAMEC score (61.0%) was significantly higher than the mean Dicon Auto-Perimeter score (26.6%). CAMEC allowed better detection and quantification of scotomas in patients more than 4 years of age.

Computerised campimetry with static dark-on-bright stimuli.

Perimetric examination of the central visual field with low contrast static dark-on-bright stimuli on a video display unit (VDU) is described. Threshold detection sensitivities to such dark stimuli are determined in normal as well as pathological central visual fields of glaucomatous, diabetic and neuro-ophthalmic patients. The static dark (light decrement type) stimuli on VDU seem capable of documenting the central visual field defects with high accuracy and revealing the field loss missed by conventional luminous (light increment type) stimuli of equal size and duration. In this report, the author presents examples from his new perimetric approach.

Clustering of fixation targets in multifixation campimetry.

The multifixation campimeter has a central test stimulus and a series of numbered fixation targets and uses the patient's eye movements to position the stimulus in the visual field. The stimulus is constantly exposed so that the patient reads the numbers and identifies any which are associated with its disappearance. The aim of this study is to identify the effect of clustering fixation targets on sensitivity. Two hundred and seventy-two eyes of 139 normal individuals were tested with a multifixation campimeter in which either one or two of the fixation targets corresponded to the physiological blind spot. Sixty-nine individuals (138 eyes) were tested with chart A and 70 individuals (134 eyes) with chart B. The second fixation target increased the blind spot detection rate from 65% to 85% of the eyes respectively. In 10% of eyes the blind spot was detected on only one of two examinations. The performance of multifixation campimetry is improved if fixation targets are clustered in vulnerable parts of the field and distributed so as to test the blind spot repeatedly during the examination. Inconsistent results are an indication for re-examination of selected points, with intermittent stimulus presentation.

The dark perimetric stimulus.

We determined the disappearance eccentricities of dark and bright stimuli of equal size in the inferonasal central visual field using the oculokinetic perimetry technique at different levels of surrounding illumination. The results suggest that a dark stimulus on a bright background has a smaller 'isoptre' than an equally bright stimulus on a dark background, and that variation of ambient illumination and consequent alteration of background luminance have less effect on the visibility of a dark stimulus than a bright one.

Visual evoked cortical potentials from transient dark and bright stimuli. Selective 'on' and 'off-pathway' testing?

The superior hemifields of five normal left eyes were stimulated by novel equal and opposite contrast pattern onset stimuli which were generated on a cathode ray tube. Patterns consisted of 144 discs, each subtending 60 min arc at the viewing distance of 40 cm and were separated by a distance equal to their diameter. Equal and opposite light changes were created by presenting the disc patterns with different luminance values on a uniform constant background (20 cd/m2). Transient visual evoked cortical potentials to the appearance and disappearance of the patterns were recorded separately and analysed. Significant amplitude differences between the responses to bright and dark stimuli were observed with light increment responses being 36-53% larger than the light decrement responses for pattern on-set and 54-80% larger for pattern off-set respectively. This finding is attributed to the difference in the input to the ON and OFF Parallel Pathways which are known to carry light increment and decrement information respectively, as well as differences in the metabolic and discharge rates of these pathways.

Low contrast visual acuity changes in human immuno-deficiency virus (HIV) infection.

A pilot study of low contrast visual acuity testing using Regan Charts has been undertaken in 34 patients seropositive for Human Immuno-Deficiency Virus and 20 normal control subjects. Low contrast visual acuities of the HIV (+) patients both with and without HIV retinopathy were found to be significantly lower than the age-matched controls (p < 0.01). This finding is probably attributable to pathology related to HIV in the visual pathways/Central Nervous System. Lowest contrast Chart (Chart C) was found to be a useful diagnostic tool for HIV retinopathy and presumed neuropathy.

Pattern of arterial involvement of the head, neck, and eyes in giant cell arteritis: three case reports.

The findings of two post-mortem examinations and one CT scan of patients with biopsy proved giant cell arteritis (GCA) are presented. The presence or absence of intracranial involvement in GCA is discussed.