Significance of the disc damage likelihood scale objectively measured by a non-mydriatic fundus camera in preperimetric glaucoma

Spotlight on the Disc-Damage Likelihood Scale (DDLS)

The disc damage likelihood scale (DDLS) is a tool for classifying glaucomatous structural changes to the optic disc based on the radial width of the neuroretinal rim at its thinnest location, or if no rim is present, the extent of absence of the rim. Unlike cup disc ratio (CDR), the DDLS also considers disc size. Twenty years after its first description, the aim of this review was to critically appraise evidence for the DDLS and evaluate its role in current practice. A literature search by two independent authors identified 33 relevant articles for inclusion. Five studies evaluated reproducibility, 5 diagnostic performance, and 2 studies examined ability to detect progression. Eleven studies evaluated correlation between DDLS and other markers of glaucoma. Despite the widespread availability of imaging devices such as optical coherence tomography (OCT), clinical examination of the optic disc remains an essential component of glaucoma diagnosis and monitoring. The DDLS provides a reliable method for semi-quantitative clinical grading of the optic disc in glaucoma, with higher reproducibility than methods such as CDR.

Automatic glaucoma screening using optic nerve head measurements and random forest classifier on fundus images

Glaucoma is an optic neuropathy that gradually steals the patient's sight by damaging the optic nerve head (which is responsible for transferring images from the eye to the brain). Causing an estimated 12.3% of global blindness, glaucoma is considered as the first leading cause of irreversible blindness in the world. This paper presents a novel eye fundus image analysis algorithm for the automatic measurement of fundus related glaucoma indicators; Cup to Disc Ratio (CDR), verification of the ISNT rule, Disc Damage Likelihood Scale (DDLS), and the classification of the input fundus into glaucoma or non-glaucoma case using a random forest model. The proposed method is applied on the public image database 'HRF', and a local database containing both, normal and glaucoma cases, and resulted sensitivity, specificity, and accuracy of 1, 0.93 and 0.97 respectively. This technique presented the highest classification accuracy compared to previous works studied in the state of the art; hence, it can be used as a computer aided glaucoma diagnosis system by ophthalmologists to assist in their screening routine.

Rim-to-Disc Ratio Outperforms Cup-to-Disc Ratio for Glaucoma Prescreening

We present a novel and fully automated fundus image processing technique for glaucoma prescreening based on the rim-to-disc ratio (RDR). The technique accurately segments the optic disc and optic cup and then computes the RDR based on which it is possible to differentiate a normal fundus from a glaucomatous one. The technique performs a further categorization into normal, moderate, or severely glaucomatous classes following the disc-damage-likelihood scale (DDLS). To the best of our knowledge, this is the first engineering attempt at using RDR and DDLS to perform glaucoma severity assessment. The segmentation of the optic disc and cup is based on the active disc, whose parameters are optimized to maximize the local contrast. The optimization is performed efficiently by means of a multiscale representation, accelerated gradient-descent, and Green’s theorem. Validations are performed on several publicly available databases as well as data provided by manufacturers of some commercially available fundus imaging devices. The segmentation and classification performance is assessed against expert clinician annotations in terms of sensitivity, specificity, accuracy, Jaccard, and Dice similarity indices. The results show that RDR based automated glaucoma assessment is about 8% to 10% more accurate than a cup-to-disc ratio (CDR) based system. An ablation study carried out considering the ground-truth expert outlines alone for classification showed that RDR is superior to CDR by 5.28% in a two-stage classification and about 3.21% in a three-stage severity grading.

Secondary glaucoma in uveitis: comparison of the optic nerve head morphology among a nonmydriatic fundus camera, HRT, and SD-OCT

PURPOSE

To assess the correlation between the disc damage likelihood scale (DDLS) objectively measured by a nonmydriatic fundus camera, confocal laser scanning ophthalmoscopy (HRT3), and spectral-domain optical coherence tomography (SD-OCT) in uveitic glaucoma.

METHODS

A total of 59 patients with uveitic glaucoma (21 female, 38 male; mean age 56.8 ± 18.7 years) were included in this prospective cross-sectional study. All patients were measured by the Kowa Nonmyd WX 3D camera (2D/3D nonmydriatic retinal camera, Kowa Company), the HRT3 (Heidelberg Engineering), and SD-OCT (Carl Zeiss Meditec) by one examiner on the same day. All 3 devices graded the optic disc topography. Statistical data were calculated using SPSS (v 20.0, SPSS).

RESULTS

In patients showing borderline results in one of the modalities (n = 45), the DDLS showed a significant correlation with the retinal nerve fiber layer (p = 0.016), while Moorfields regression analysis (p = 0.550) and glaucoma probability score (p = 0.629) did not correlate significantly. The highest predictive power was demonstrated by the objectively measured DDLS (area under the receiver operating characteristic curve 0.445-0.588), compared to R. Burk (0.149-0.375) and F.S. Mikelberg (0.033-0.450) coefficients considering HRT and optical coherence tomography.

CONCLUSIONS

In this study cohort, the objective DDLS showed the highest predictive power and thus is a reliable tool in diagnosing uveitic glaucoma. These 3 devices cannot be used interchangeably. As diagnosis and follow-ups are challenging in uveitis patients, the stereophotography is additionally a valuable tool.