The SPARK examination strategy was primarily developed for glaucoma patients and is available for all OCULUS perimeters. It is based on data from more than 90 000 perimetric findings and allows a very fast, yet very precise measurement of thresholds in the central visual field. The modular structure of the method makes it suitable for a variety of applications:
- SPARK Precision (optional software) is the full version of SPARK. The complete visual field examination of glaucoma patients takes only 3 minutes per eye. The greater stability of the results allows for more sensitive progression analysis.
- SPARK Quick is used for follow-up or screening examinations. The test takes just 90 seconds per eye.
- SPARK Training is ideal for patient training. The 40 second measurement can also be used as a screening examination.
The enhanced Glaucoma Staging System (GSS 2) of Brusini classifies visual field defects based on the perimetric indices MD (Mean Deviation) and PSD (Pattern Standard Deviation). The representative point of the examination is placed in a chart according to the values of these indices. The chart displays defined areas for the different stages of disease (Stage 0 – Stage 5) and separates generalized, localized and mixed defects.
The Glaucoma Staging Program (GSP) is based on pattern recognition and is dedicated to early detection of glaucoma.
The GSP software places examination findings into visual field classes (normal, glaucomatous, artifactual and neuro) based solely on their appearance. In addition, risk classes (normal, suspect, pre-perimetric, early stage, moderate and severe) are also assigned to findings that are classified as normal or glaucomatous. The evaluation results are presented in intuitive green-yellow-red color coding.
The striking novelty of the GSP is its ability to detect subtle changes in the visual field associated with early stage glaucoma. Findings of suspect and pre-perimetric risk classes may contain reductions in the visual field that cannot be readily seen by the examiner. They usually remain undetected also by standard perimetric indices.
The Glaucoma Likelihood Index (GLI) summarizes the results of the GSP classification into a single parameter presenting a value between 0 (normal) and 5 (severe glaucoma).
The Glaucoma Staging Program (GSP) is available for OCULUS Twinfield® 2, Centerfield® 2 and Easyfield® perimeters. This upgrade is available for the existing units.
TNT provides a quantitative, statistical analysis of the visual field examinations conducted over time. For follow-up purposes the software uses all visual field results taken over the entire observation period and takes the patient's threshold values into account obtained on the 30-2, 30x24 or 24-2 patterns. TNT uses a specific filter to reduce the fluctuation range of the threshold values and to perform a consistent trend analysis. In conjunction with the fast SPARK strategy, the sensitivity of detecting progression in early stage glaucoma is greatly improved.
- TNT creates a concise progression analysis report containing the most important parameters (MD increase, p-values, etc.).
- TNT can differentiate between diffuse and focal progression based on the focality index (FI) value.
- TNT applies multiple statistical criteria to establish possible progression.
- TNT displays the prognosis of the expected visual field for a patient age-group selected by the examiner.
Functionality of a retinal location obviously depends on the underlying anatomical structure of the retina in that location. One characteristic feature of glaucoma is that there is a close connection between sensitivity levels of given retinal locations (as described by visual field measurements) and anatomical structures related to the optic nerve head. The merit of PATH is that it provides an estimate of the retinal nerve fibre layer (RNFL) thickness around the optic nerve head and the relative area of the neuroretinal rim based solely on the results of visual field measurements performed with the SPARK examination strategy. This novel approach of predicting structure from function is made possible by the high reproducibility of the SPARK visual field exams.
Predicting RNFL thickness
Working from the results of SPARK perimetry, RNFL thickness is predicted at 25 points of the TSNIT (Temporal – Superior – Nasal – Inferior – Temporal) circle around the optic nerve head. The value at each point is calculated from functional data selected for relevance. This selection is based on an objectively automated machine learning algorithm and does not rely on other findings such as on the correspondence between nerve fibre pathways and visual field areas.
Predicting the relative area of the neuroretinal rim
A linear combination of relevant threshold results is used in order to predict the ratio between the neuroretinal rim area and the total area of the optic disc. The result is compared to normative data and expressed as a percentage of the population average value (normalized to 100%).