Comparison of optic disc image assessment methods when examining serial photographs for glaucomatous progression

Association between focal lamina cribrosa defects and optic disc haemorrhage in glaucoma

BACKGROUND/AIMS

To explore the relationship between focal lamina defect (LD) size and optic disc haemorrhages (DH) in glaucomatous eyes.

METHODS

Radial B-scan images at 15° intervals obtained using enhanced depth imaging (EDI) spectral-domain optical coherence tomography (OCT) were performed on a group of subjects previously assessed for DH every 3 months over a period of 5 years. EDI-OCT scans were assessed for the presence of focal lamina cribrosa defects by a single observer.

RESULTS

119 eyes from 62 subjects (44 females, 18 males) were analysed. 44 eyes (37%) were noted to have at least 1 LD, and of those, eight eyes had more than one defect. 68 eyes (57%) were observed to have at least one DH occur over the course of monitoring. 48 eyes (40%) had recurrent DH, with a mean of 5.17 haemorrhages over the 5-year period. Type 1 focal LD (p=0.0000, OR 7.17), glaucoma progression (p=0.0024, OR 0.32) and ArtDiff (p=0.0466, OR 1.04) were significantly associated as predictors of DH. No correlation between the size of the LD and DH occurrence (p=0.6449, Spearman rank correlation) was found.

CONCLUSION

Focal lamina cribrosa hole-type defects were significantly associated with an increase in DH occurrence over the preceding 5 years. The lack of association between defect size and DH suggests that DH and lamina defects may have separate links to the glaucomatous process.

Evaluation of a Qualitative Approach for Detecting Glaucomatous Progression Using Wide-Field Optical Coherence Tomography Scans

Purpose

To determine the effectiveness of detecting glaucomatous progression by a qualitative evaluation of wide-field (12 × 9 mm) scans on optical coherence tomography imaging. This method was compared to a conventional quantitative analysis of the global circumpapillary retinal nerve fiber layer (cpRNFL) thickness.

Methods

A total of 409 eyes with a clinical diagnosis of glaucoma or suspected glaucoma for which two wide-field scans were obtained at least 1 year apart (n = 125) and within one session (n = 284) were included to determine the sensitivity of detecting progression at 95% specificity. Qualitative OCT evaluation was performed in a similar manner to flicker chronoscopy by superimposing the two scans, and the progression probability was graded. A quantitative event-based analysis of the global cpRNFL thickness also was performed.

Results

Thirty-three and 25 eyes were deemed to have progressed based on qualitative and quantitative approaches, respectively (P = 0.152). A post hoc review of cases where the two methods disagreed revealed that all eyes missed by the quantitative analysis had established glaucomatous damage that appeared to show characteristic patterns of progression. All eyes missed by the qualitative evaluation appeared to be free of such established damage, and instead showed a generalized reduction in cpRNFL thickness.

Conclusions

Qualitative evaluation of OCT imaging information more frequently detected change consistent with known patterns of glaucomatous progression than global cpRNFL thickness, warranting further studies to evaluate its value.

Translational Relevance

A framework for qualitatively evaluating progressive glaucomatous changes on OCT imaging clinically shows promise.

Do optic discs get "thinner" or "narrower?"

PURPOSE

To survey the literature to determine how the dimensions of the neuroretinal rim are commonly described, and to clarify and standardize the description of changes in the dimensions of the neuroretinal rim in glaucoma.

MATERIALS AND METHODS

Literature review of 275 articles describing the neuroretinal rim in glaucoma and a survey of ophthalmologists describing 2 disc photographs. Frequencies of descriptors of the neuroretinal rim were surveyed, which included "thinning" and "narrowing."

RESULTS

Of the 275 articles, 80 described the neuroretinal rim clinically. Forty-one articles used "thinning" to describe progressive loss of rim tissue in a radial axis, 13 articles used "narrowing" and rest used "width" to describe the characteristics of neuroretinal rim. Of the 295 ophthalmologists, 264 used "thinner," whereas 31 used "narrower" to describe the neuroretinal rim.

CONCLUSIONS

Accurate phenotyping is an essential part of patient care, research, and training. "Thinning" is currently used more commonly than "narrowing" in the literature to describe progressive loss of the neuroretinal rim in a radial axis. It would be appropriate to use "narrowing" for radial loss or decrease in width and "thinning" for decrease in the thickness of the rim.

Diagnosing glaucoma progression: current practice and promising technologies

PURPOSE OF REVIEW

An update on recent work is provided that has broadened our understanding of the evaluation of visual function and structure, and their use in evaluating glaucoma progression.

RECENT FINDINGS

The challenge of determining visual-field progression and the implications of long-term fluctuation are reviewed and data to support the magnitude of the fluctuation are cited. The use of confirmatory testing can limit the over diagnosis of glaucoma progression. Focusing visual-field testing on the locations of present scotomas or using frequency doubling technology may provide new approaches to assessing visual function. New standardized techniques to interpret visual fields, including neural networks, unsupervised machine learning and pointwise linear regression, may provide more quantitative means for visual-field interpretation. These techniques, along with structural evaluation of the optic nerve and nerve fiber layer, are essential in glaucoma management. Optic-nerve-head photography is still a mainstay in evaluating glaucoma progression, although many technologies including scanning laser tomography, scanning laser polarimetry and optical coherence tomography offer more quantitative means to follow structural change. These modalities, in different ways, show promise in providing additional information regarding the stability of glaucoma.

SUMMARY

Identifying the functional visual component as well as structural changes is essential in evaluating glaucoma progression. New techniques of testing and evaluating visual fields, the optic-nerve head, and the retinal nerve fiber layer offer exciting opportunities to more accurately identify glaucoma progression, and are likely to become more central as imaging devices and software support develop further.

3D vs 2D qualitative and semiquantitative evaluation of the glaucomatous optic disc atrophy using computer-assisted stereophotography

BACKGROUND AND PURPOSE

Real colour documentation of the optic nerve head (ONH) is one of the most important methods to identify the early progression of glaucomatous optic nerve damage. This study compares the qualitative and semiquantitative evaluation of ONH photographs, using a 3D time-multiplexing system and conventional 2D photography, visualised on a computer monitor.

PATIENTS AND METHODS

Stereophotographs of the ONH were converted by special software in a 3D file. The same images were shown in 2D and 3D to 22 subjects with different training grades (residents and ophthalmologists). The evaluation based on a standardised questionnaire, containing semiquantitative parameters of the ONH. A weighted score for quality of ONH assessment counted the correct answers of the observers to compare their evaluation in 2D to the one made in 3D.

RESULTS

All of the observers achieved a significant better evaluation of the ONH with 3D than with 2D images. No significant differences were observed between both groups. Classification errors with respect to the 'gold standard' were lower for 3D measurements as compared with 2D measurements (P=0.007). No significant differences were observed between the gold standard and residents or ophthalmologists for the ONH size, but for the c/dratio the stereoscopic images lead to better results.

CONCLUSION

This study showed a better evaluation of parameters associated with the glaucomatous ONH atrophy with 3D images compared with 2D, independent of the clinical training grade. The computer-based evaluation of the ONH atrophy by using a time-multiplexing system (shutter-glasses) may improve the diagnosis of glaucoma patients.

[Time-multiplexing stereophotography: 2D and 3D qualitative and semiquantitative evaluation of glaucomatous optic disc atrophy]

PURPOSE

Real color documentation of the optic nerve head (ONH) is one of the most important methods in identifying early progression of glaucomatous optic nerve damage. This study qualitatively and semiquantitatively compared the evaluation of ONH photographs, using a 3D time-multiplexing system and conventional 2D photography, visualized on a computer monitor.

PATIENTS AND METHODS

Twelve 15 degrees sequential stereophotographs from the Erlangen Glaucoma Registry were scanned by a SprintScan 35 Plus Film scanner (Polaroid, Waltham, MA, USA) and converted by computer software (3D-PIX, NuVision, McNaughton Inc., Beaverton, OR, USA) in jps format (3D). The same ONH images were shown in 2D and 3D to 22 subjects: 12 residents and ten ophthalmologists and evaluated using a standardized questionnaire.

RESULTS

We observed a significantly better evaluation with stereoscopic pictures for both qualitative parameters (cup depth, visibility of the retinal nerve fibers, and the thinnest location of the neuroretinal rim) and quantitative parameters (c/d ratio and size of the disc, depending on the training level: in 3D better evaluation by the residents, in 2D by the ophthalmologists). With 2D pictures, we found better evaluation of the B zone and the stage of atrophy. Other than the method used for the entire evaluation, there was no significant difference between the groups. For the parameters weighed for clinical importance, the score of correct answers was significantly better with stereoscopic pictures.

CONCLUSION

This study showed a significantly better evaluation of glaucomatous ONH atrophy with 3D images than with 2D pictures, independently of the evaluators' clinical training level. The computer-based evaluation of ONH atrophy using a time-multiplexing system (shutter glasses) may improve the diagnosis of glaucoma patients.

Value of retinal vein pulsation characteristics in predicting increased optic disc excavation

BACKGROUND

Retinal vein pulsation is often absent in glaucoma, but can be induced by applying a graded ophthalmodynamometric force (ODF) to the eye, which is elevated in glaucoma.

AIM

To assess whether ODF has a predictive value in determining glaucoma progression.

METHODS

75 patients with glaucoma and suspected glaucoma were examined prospectively in 1996, and then re-examined at a mean of 82 months later. All subjects had intraocular pressure, visual fields, stereo optic disc photography and ODF measured on their initial visit. When venous pulsation was spontaneous, the ODF was said to be 0 g. At re-examination, central corneal thickness and blood pressure were also measured. Initial and subsequent optic disc photographs were compared and graded into those that had increased excavation and those that had remained stable. The relationship between increased excavation (recorded as a binary response) and the measured variables was modelled using a multiple mixed effects logistic regression.

RESULTS

ODF at the initial visit was strongly predictive of increased excavation (p = 0.004, odds ratio 1.16/g, range 0-60 g), with greater predictive value in women than in men (p = 0.004). Visual field mean deviation was predictive of increased excavation (p = 0.044), as was optic nerve haemorrhage in association with older age (p = 0.038). Central corneal thickness was not significantly predictive of increased excavation (p = 0.074) after having adjusted for other variables.

CONCLUSION

ODF measurement seems to be strongly predictive of the patient's risk for increased optic disc excavation. This suggests that ODF measurement may have predictive value in assessing the likelihood of glaucoma progression.

The reengineering of a software system for glaucoma analysis

Glaucoma is a destructive eye disease that causes blindness in individuals displaying little or no symptoms. There is no cure as yet though there are treatments that can arrest its effects or slow its development. The earlier the disease is detected, the more likely the treatment will be successful; however early detection of the disease can be difficult. This highlights the importance of ophthalmologists having access to tools that can assist in accurately diagnosing glaucoma and other retinal diseases as early as possible. The stereo optic disc analyser (SODA) software package is a tool intended to be used by ophthalmologists, to aid in the accurate detection of retinal diseases. SODA will use stereoscopy and three-dimensional image analysis to assist in accurately detecting changes in the retina, caused by diseases such as glaucoma. This paper will focus on the reengineering and redesign of the SODA software package to overcome the shortcomings inherent in its prototype implementation and develop a package that can be commercialised. Software Engineering principles and the software development lifecycle, along with principles of object-orientation and usability, have been used to establish a framework for SODA, improve its accuracy, enhance its usability and to redevelop the product into an implementation that can later be commercialised.

Optic disc hemorrhage in Asian glaucoma patients

PURPOSE

To assess the prevalence of optic disc hemorrhage in Asian patients with established glaucoma using a recently described, highly sensitive detection method.

MATERIALS AND METHODS

Patients entering a trial of glaucoma filtering surgery in Southeast Asia (The Singapore 5FU Study) were assessed for the presence or absence of optic disc hemorrhage using stereo flicker chronoscopy of stereophotograph pairs.

RESULTS

A total of 167 patients (117 males and 50 females) were assessed, of whom 128 were Chinese. Primary open-angle glaucoma was diagnosed in 90 patients, primary angle-closure glaucoma in 69 patients, and pseudoexfoliative or pigment dispersion glaucoma in 7 patients. Five eyes of 5 patients had disc hemorrhage at enrollment (5/167), a rate of 2.99%. Four patients with disc hemorrhage had primary open-angle glaucoma and 1 had primary angle-closure glaucoma. There were no significant differences in global visual field indices, AGIS scores, or intraocular pressures between eyes with and without disc hemorrhage. All disc hemorrhages were seen in eyes prior to trabeculectomy.

CONCLUSIONS

The prevalence of disc hemorrhage in the current study was comparable to that seen in primary open-angle glaucoma in clinic-based studies of white patients, but far less than that reported in normal-tension glaucoma studies. Hemorrhages were more common in primary open-angle glaucoma than primary angle-closure glaucoma.

Computer-assisted planimetry associated with Sturge-Weber syndrome

Photographs of the optic nerve head (optic disc) in the eye are used for the clinical assessment of the disease glaucoma. These images are usually subjectively assessed by a clinician. A case of Sturge-Weber Syndrome which includes glaucoma as a symptom, is presented here. Narrowing of the rim of the optic disc was measured using custom-made measurement software confirming glaucomatous progression. To maximize the information obtained from optic disc images, low cost software can assist with quantifying disc parameters aiding clinical interpretation.

Neuroretinal rim measurement error using PC-based stereo software

The neuroretinal rims of a set of glaucoma patients were measured using digitized stereo photographs, to determine the reproducibility of computerized stereo measurements of the neuroretinal rim. Each rim was measured five times at 18 locations, with measurement error (ME) defined as the mean of standard deviations of each set of measurements. The following ME were determined: (i) inter-sessional variability (n = 27 right and 24 left eyes, at t1 and t2); (ii) inter-assessor variability (n = 9, 2 assessors); and (iii) variability after colour adjustment algorithms were applied (n = 15). The results were as follows: (i) inter-sessional variability was 3.41+/-1.08 for t1 and 3.22+/-0.84 for t2; (ii) there was a significant difference between the two assessors, although the ME was still low; and (iii) there was no significant differences between the ME of unadjusted and adjusted images. With a measurement error of up to 11% of rim width, these results show that lowcost rim measurements can be made using PC-based software.