Projection Perimeter Research Articles

A new method for reconstructing the 3D shape of single cells in fruit

Fruit cells’ shape generally reflects the physiological state and quality of the fruit, and indirectly dictates its economics. In this study, a new bio-microscope including three independent and orthogonal channels of opto-electromechanical microscopic observation systems was developed to obtain the three views (e.g., front view, top view, side view) of a single fruit cell using tomato and strawberry at two ripening stages as fruit samples. The obtained three-view images were used to reconstruct the 3D real shape of a single cell based on the 3D geometrical modelling method using Solidworks CAD design software and then compared with the actual geometric size. The average relative errors for the major diameter, minor diameter 1, minor diameter 2, projection perimeter and projection area were 4.04 %, 6.25 %, 5.71 %, 1.69 % and 3.79 %, respectively. This good accuracy makes the newly developed bio-microscope together with the proposed 3D geometrical modelling method a promising 3D shape reconstruction technology for a single fruit cell to extract real and detailed cell morphology information. Furthermore, this method can find applications in other fields such as human and animal cells where soft particles’ 3D shape analysis is important.

Визначення параметрів горизонтальних проекцій крон дерев за матеріалами зйомки безпілотними літальними апаратами

Опрацьовано можливість використання результатів зйомки дерев із безпілотного літального апарата (БПЛА) DJI Phantom 4 для визначення горизонтальних проекцій їхніх крон. Встановлено, що такий підхід дає змогу підвищувати якість, точність і швидкість визначення площі горизонтальної проекції крони за актуальним картографічним матеріалом, опрацьованим у середовищі ГІС. Апробацію запропонованого способу проведено на базі лісових масивів і садово-паркових насаджень міста Бережани в Тернопільській області шляхом порівняння результатів, отриманих з використанням цього підходу й традиційним способом вимірювання. Виявлено, що запропонований спосіб дає можливість отримувати результати високої точності внаслідок кращої передачі конфігурації крони фотографічними матеріалами БПЛА-зйомки в порівнянні з традиційними вимірювальними методами, які дають інформацію лише про її радіуси. Такий підхід дає змогу визначати горизонтальні проекції крон дерев за допомогою програмних засобів із мінімізацією трудомістких польових робіт і створює умови для збереження інформації в цифровому форматі. Він може бути використаний для потреб лісо- та парковпорядкування, вивчення взаємодії деревних рослин у насадженні, визначення зімкнутості деревостану, проведення інвентаризації зелених насаджень та інших наукових досліджень.

Clinical evaluation of video imaging technology during visual field exams

PurposeVideo imaging consists in recording the entire visual field process in synchrony with the video of the patient's head. Several clinical applications have been investigated to evaluate the clinical usefulness of this new technology.MethodsThe study included results from 48 visual field exams performed on a MonCvONE full field projection perimeter with synchronized video recording.The video from a large viewing field camera was recorded in synchrony with the position of the visual stimulus, with other test parameters such as luminance and size and with the patient's response obtained from the patient's press button or from the operator judgment. The study included patients who were unable to perform automated perimetry due to young age or handicap, patients with abnormal eye movements, head posture or ptosis and controls performed after automated perimetry.ResultsVideo recording was extremely useful in the majority of clinical cases. 24 exams were performed on young children (age between 2 and 5 years) using attraction perimetry. The eye orientation responses could be interpreted and validated after the exam. In other cases, the video recording facilitated the interpretation and documentation of visual field results with the inclusion of video snapshots in the examination report. Additional applications included the recording of cardinal eye gaze positions and of the fusion visual field.ConclusionsSynchronized video imaging performed during visual field exams is a clinically useful tool for the examination of patients who cannot perform automated perimetry and for the documentation of artefacts and situations such as ptosis, abnormal eye movements, abnormal head posture and incorrect position of refraction.

On the characterization of size and shape of irregular particles

The size and shape characterization of irregular particles is a key issue in many fields of science, which is often associated with large uncertainties. We assess existing protocols and introduce new strategies for the study of size and shape of irregular particles by performing a comprehensive characterization of 127 volcanic clasts with diameters between 155μm and 37mm. Methods include caliper measurements, image analysis, laser scanning and scanning electron microscope micro-computed tomography. Volume, surface area and various shape descriptors including form factors (e.g. flatness, elongation), circularity measures and sphericity are analyzed. First, existing procedures commonly applied by caliper and image analysis to determine 1D (i.e. particle lengths in three dimensions) and 2D variables (e.g. particle projection perimeter and area) have been revised. A new procedure based on particle projection area (PA protocol) for measuring particle lengths in three dimensions is also proposed that is associated with the lowest operator-related errors with respect to existing protocols. In addition, the effect of number of particle projections on the variables obtained through image analysis is investigated. It was found that two to three perpendicular projections can be used to characterize 2D variables with a maximum error of <10%. Second, 1D and 2D variables calculated based on the new PA protocol and image analysis are used to derive shape descriptors and investigate their variability and correlations. Finally, both existing and new empirical correlations for the estimation of 3D particle parameters (i.e. volume, surface area, sphericity) based on 1D and 2D variables are presented and benchmarked. It was found that correlations that are based on 2D variables are associated with the lowest average error (~2.6–4.6%).

Influence of a Dilated Pupil on the Visual Field in Glaucoma

The author studied the effects of pupillary dilation on perimetry in a group of glaucomatous patients receiving timolol therapy. A prospective study compared the visual fields of 23 patients with primary open-angle glaucoma of varying severity (mean defect: 3.84; short-term fluctuation: 1.91; pattern standard deviation [SD]: 3.61; corrected pattern SD: 3.12) before and after instillation of phenylephrine 10% using the Octopus 1-2-3 projection perimeter (INTERZEAG AG, Schlieren, Switzerland). The mean defect became impaired by an average of 3.01 (SD +/- 1.52) dB after administration of phenylephrine (p < 0.001). The pattern SD and the corrected pattern SD also became impaired with dilation by 1.51 dB (p < 0.01) and 1.73 dB (p < 0.05), respectively, after dilation. These changes varied across the visual field. The outer zone of the visual field had the greatest impairment after dilation with phenylephrine. Pupillary dilation in patients with glaucoma produces a nonuniform decrease in threshold sensitivities that is statistically greater on outer zone of the visual field.

Visual Field Loss While Wearing Full-Face Respiratory Protection

The loss of visual field was quantified for 21 test subjects while they wore three full-face respirators. Changes in visual field were quantified for each type of respirator using a modified Goldmann projection perimeter. The loss of visual field was determined by calculating the area under the curve while wearing a respirator to that while wearing no respirator. Distinct patterns of visual field loss were apparent for the different style respirators. Analysis of the patterns could lead to the design of full-face respirators with improved visual qualities, which could improve worker safety for certain occupations. This technique also could be of help when selecting models of respiratory protection when certain visual fields must be maintained.

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.

The influence of stimulus parameters on the visual field indices by automated projection perimetry

The various stimulus parameters offered by two standard automated projection perimeters [Humphrey Field Analyser 630 (HFA) and Octopus 201], namely, stimulus size and location and the interaction of adaptation level and stimulus duration, were compared in a sample of 20 patients attending a glaucoma clinic using the visual field indices mean defect (MD), loss variance (LV), short-term fluctuation (SF) and corrected loss variance (CLV). LV and SF were greater with Octopus program 32 compared with Octopus program G1 (P < 0.02). No difference in the indices was found between stimulus sizes I and III for HFA program 30-2. MD was greater for program 30-2 compared with program 32 (P < 0.002) when expressed in terms of log (L/delta L) whereas LV (P < 0.02) and SF (P < 0.02) were greater for program 32. All differences were considered to be negligible in the clinical sense.

Variability of Quantitative Automated Perimetry in Normal Observers

The test/retest variability in different regions of the visual field were evauated in six commercially available automated threshold static perimeters using normal volunteers. Three of the devices were projection perimeters (Squid®, Octopus 500®, Humphrey Field Analyzer®) and three of them used light-emitting diode stimuli (Dicon 2000®, Fieldmaster 50®, Digilab 350®). The authors' results show that, although some devices were better than others, all have some degree of variability. In addition, they found that there is increased variability from the central 10° out to 30° eccentricity for each perimeter.

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 (5570 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.

Visual field testing with red targets.

Ten patients with partial temporal visual field defects were examined with a modified tangent screen projection perimeter (Auto-Plot). Defects demonstrated with an isopter for chromatic recognition of a 3-mm red stimulus could always be reproduced with an isopter for achromatic recognition of a dim, 3-mm white stimulus. The red-white intensity ratio producing equivalent fields remained constant for a given patient but varied from subject to subject (range, 3.0 to 7.5; mean, 5.7; SD, 1.8). Thus, red functioned as dim white, but no single fixed ratio of intensities was applicable to all subjects. Visual field testing with 1 foot-candle of tangent screen illumination permitted subjects to adapt to dark. As retinal sensitivities increased, the corresponding visual field steadily enlarged for 30 minutes. This effect was greater in the pathologic temporal fields, which increased relatively more than intact nasal fields. The result was poor visual field reproducibility with time.

Manual projection perimetry combined with a pattern (author's transl)

The use of a uniform pattern for perimetry at the center of the visual field enables scotomas boundaries to be reproduced with almost complete authenticity, and small, isolated losses to be determined. As is the case with several automatic perimeters, the pattern principle can be used manually with the Goldmann projection perimeter; it is only necessary to modify the visual field scheme. The uniform pattern also permits the extent of central visual field loss to be expressed by means of a quotient which is simple to calculate.

Calibration of the Goldmann perimeter and accessories used in specific quantitative perimetry.

With known radiometric data of the components of the projection perimeter and its accessories it is possible to perform spectral sensitivity measurements which are essential for the performance of quantitative colour perimetry. The authors describes modifications made the Goldmann perimeter for the performance of such measurements. The calibration data of the perimeter and accessories are given. A good fit between the CIE scotopic spectral sensitivity curve (V' lambda) and our experimental results for a dark adapted eye serves as a control of the calibration.

A Comparison of Four Projection Perimeters

Identical specifications for size and luminance of the target and dome on four projection perimeters-Goldmann, Marco, Topcon, and Rodenstock- seemed to indicate that similar visual fields should be plottable with each instrument. We subjected 30 eyes to perimetry with all four machines. The Rodenstock perimeter was usually unable to map the central field with the I2e target and to identify the presence of most visual field defects. The Goldmann was most capable of demonstrating the presence of existing scotomata and was also able to plot them with the greatest definition. The Topcon was next most sensitive followed closely by the Marco. Analysis of the actual target size and luminance on each machine showed that significant variation existed and was probably responsible for the visual field differences that we found.

A description of a method for objective perimetry (author's transl)

An infrared-sensitive TV Camera has been fitted into a projection perimeter, which allows to control fixation independent of the particular background illumination. The consensual pupil light reflex, triggered by the test light of the perimeter, is measured and registered with a special TV processor designed for this purpose. The method was tested for its efficiency on four healthy volunteers. The course of sensory and pupillomotor thresholds were measured on the 135 degree meridian of the visual field. Determinations were conducted in the photopic range of 10 asb background illumination with two test points of 27' and 7'. A difference of 10 dB was found between the sensory and pupillomotor thresholds.

A comparison of four projection perimeters. Instrument specifications

In addition to the original and highly popular instrument designed by Goldmann, three other projection perimeters are now available. Features of the Goldmann, Topcon, Marco and Rodenstock machines are examined and compared.

The colour receptors studied by increment threshold measurements during chromatic adaptation in the Goldmann perimeter.

With the help of a method based on the Goldmann projection perimeter, measurements of spectral sensitivity during chromatic adaptation are performed utilizing the principle of the two‐colour threshold technique of Stiles. The method is flexible and is used for central as well as for peripheral registration. Characteristic sensitivity curves and static perimetry curves of normally sighted persons are demonstrated showing that each type of cones can be clearly separated and identified. With smaller sized objects, the foveal blue blindness is confirmed whilst in the parafoveal region the response of the blue receptor is good.

Modern perimetry in neuro-ophthalmic diagnosis.

Modern, hemispheric, projection perimeters have made it possible to obtain much more accurate information about the extent and progress of lesions affecting the visual pathways than one can gain by using the tangent screen and older arc perimeters. The newer instruments provide precisely controlled and standardized testing conditions that are necessary for perimetry, ie, determining all three dimensions of Traquair's island of vision. The third dimension, sensitivity to light and contrast, is directly measured by static perimetry, a valuable new method that has not yet been used to full advantage in neuro-ophthalmic diagnosis. This review describes the principles and techniques of quantitative perimetry, discusses some of the variables that affect the results of its use, and demonstrates its application to diagnostic problems.

A New Projection Adaptometer

<h3>I. Introduction</h3> An instrument has been designed and constructed for measuring the light thresholds of the human retina. It utilizes certain basic parts of the Goldmann Projection Perimeter. There are certain unique features in the adaptometric design which provide high levels of sensitivity, reliability, and experimental facility. Any point of the retina may be investigated, and the differential thresholds may be determined under a wide variety of adaptation levels. Adaptometric profiles or classic dark-adaptation curves may be recorded. <h3>II. Previous Equipment</h3> Since the early contribution by Aubert¹in 1865, many instruments have been designed for adaptometry. Investigations of the light sense have included determinations of the dark-adaptation curve as well as measurements of the thresholds of various areas of the retina.^2-5The published reports, dealing with adaptometric studies prior to 1937, have been carefully reviewed by Adams⁶and Sloan.⁷Three adaptometers, designed for clinical testing, have

Nature of the limit of the color zone in perimetry.

Blue and yellow outer color zones on the lower vertical meridian were measured in a Goldmann spherical projection perimeter using three different techniques and four observers.The limits of the color zones are not smooth but show irregular peaks and dips and do not have sharp cutoffs in sensitivity. The peaks and dips are reliable for any given observer, although they do not correspond between observers.The method of constant stimuli, the method of limits, and the clinical one-directional technique were compared. The method of constant stimuli is the most reliable method and it gives the most information about the shape and size of the color gradient.