|Year : 2019 | Volume
| Issue : 2 | Page : 86-89
Ultrasonographic and Clinical Correlation of Optic Disc Cupping − A Report
Sowmya Raveendra Murthy, Ankita Sharma
Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Bengaluru, India
|Date of Submission||14-Jan-2019|
|Date of Decision||23-Jun-2019|
|Date of Acceptance||14-Jul-2019|
|Date of Web Publication||07-Feb-2020|
Dr. Sowmya Raveendra Murthy
Sankara Eye Hospital, Bengaluru
Source of Support: None, Conflict of Interest: None
Presence of total cataract precludes the view of optic nerve head (ONH) and makes diagnosis of glaucoma difficult in presence of normal intraocular pressure. So, we studied the reliability of B scan in detecting ONH cupping and correlating with clinical findings. Aim: We aimed to note the diagnostic value of ultrasound echography (B scan) in determining the ONH cupping in patients with dense cataract. Methods: We included 195 eyes with total cataract and correlated the cupping noted in these eyes with clinical cupping noted postoperatively. Results: Clinical cupping was present in 50 patients and B scan could predict it in 13 patients. The sensitivity of B scan in predicting ONH cupping was found to be 16% (95% confidence interval 0.17–0.29) with specificity of 97.8% (95% confidence interval 0.94–0.99). A decrease in cup:disc ratio of 0.6 or less led to a decrease in sensitivity. Conclusions: Our study suggests that ultrasound echography may provide a qualitative assessment of the ONH cupping in glaucoma in some cases wherein there is media opacity such as cataract that precludes view of the ONH during fundoscopy. B-scan ultrasonography is done as a part of routine preoperative evaluation in cases where there is dense cataract and helps identify associated normal pressure glaucoma.
Keywords: B scan, optic disc cupping, total cataract
|How to cite this article:|
Murthy SR, Sharma A. Ultrasonographic and Clinical Correlation of Optic Disc Cupping − A Report. Niger J Ophthalmol 2019;27:86-9
| Introduction|| |
Cataract has been documented to be the most significant cause of bilateral blindness in India and has been reported to be responsible for 50% to 80% of the bilaterally blind in the country.,,,,, Glaucoma is the second leading cause of blindness after cataract. It is known to affect 60.7 million people worldwide with the estimated prevalence in India being 11.9 million.
Assessment and diagnosis of glaucoma includes tonometry, perimetry, and morphological evaluation of the optic disc. These methods involve expensive specialist equipment and image quality may be affected by media opacities. The presence of a total cataract precludes us from having a complete assessment of optic nerve head (ONH), which is important for diagnosis of glaucoma with normal intraocular pressures (IOPs). Hence, ocular ultrasonography (B scan) can help us in evaluating the ONH in the setting of dense cataract and similar other media opacities.
The eyeball’s fluid content and its superficial position make it ideally suited for examination with ultrasound. It is a simple, noninvasive tool for diagnosing lesions of the posterior segment of the eyeball. The optic nerve is well suited to echographic imaging because of its regular tubular structure consisting of low reflective nerve proper and highly reflective perineural sheaths, surrounded by the heterogeneous orbital fat.
Our study was aimed to evaluate the reliability of B scan in detecting ONH cupping and correlating it with clinical findings. Assessing the status of ONH in patients where morphological disc changes are not visible would help to devise an appropriate surgical plan and explain visual prognosis to the patient.
| Materials and Methods|| |
Patients were selected from outpatient community services of a tertiary eye hospital in South India from May 2018 to June 2018. Institutional ethical committee approval was obtained. A total of 295 eyes of 295 patients were evaluated. Patients with total cataract who underwent B scan as a part of routine preoperative evaluation were included. Patients who were unwilling to take part, those with active ocular surface disease, and in whom optic disc was not clearly visible postoperatively were excluded. All the patients underwent complete ophthalmic examination that included visual acuity measurement, tonometry, slit lamp biomicroscopy, gonioscopy, and B-scan ultrasonography.
B scan was done by multiple investigators unaware of the clinical findings. ONH cupping was documented and then compared with postoperative clinical findings. We used ultrascan imaging system from OTI Ophthalmic Technologies, Canada, a contact B scan with a frequency of 10 MHz, with the patient lying supine and the probe placed over the closed eyelid at the temporal equator, aiming nasally and posteriorly after application of a coupling gel. Fine adjustment of the probe was made while the patient fixates gaze in the primary position or slightly infero-temporally. Transverse (cross-section) and longitudinal (long-section) axial scans were performed on ONH giving vertical and horizontal sections of the disc cup. Both the sections have the advantage of avoiding the lens and allowing better resolution of images. Best images were frozen and photographs were taken [Figure 1].
|Figure 1 Axial B-scan display showing the optic cup as a posterior concavity anterior to the acoustically clear area of the optic nerve.|
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All the patients underwent temporal section small incision cataract surgery and were evaluated on day 1 of surgery for evidence of clinical cupping and comparisons were made with the B-scan findings.
| Results|| |
A total of 295 patients participated in this study. The group comprised of 184 females and 111 males. The average age was 62 years with a range of 35 to 92 years. There were 151 right eyes and 144 left eyes that were included. The average IOP of the operated eye was 14 mmHg.
All patients underwent small incision cataract surgery with implantation of posterior chamber intraocular lens via temporal incision. The different types of cataract that were operated are shown in [Table 1].
In 295 patients, clinical cupping was present in 50 patients and B scan could predict it in 13 patients. Sensitivity was calculated as the percentage of patients who were true positive (cup: disc ≥ 0.5) on B scan compared to the number of patients who had cupping on clinical examination (true positive + false negative) whereas specificity was calculated as the percentage of patients who were true negative (cup: disc < 0.5) on B scan compared to the number of patients who did not have cupping on clinical examination (true negative + false positive). The sensitivity of B scan in predicting ONH cupping was found to be 16% (95% confidence interval 0.17–0.29) with specificity of 97.8% (95% confidence interval 0.94–0.99).
In patients with a cup:disc ratio of 0.7:1 and 0.8:1, B scan was able to predict cupping in 66.67% and 50%, respectively, whereas in patients with a cup:disc ratio of 0.9:1, B scan accurately predicted optic head cupping in 100% patients [Table 2]. A decrease in cup:disc ratio 0.6 or less led to a decrease in sensitivity.
|Table 2 Accuracy of B-scan to predict optic nerve head cupping in terms of cup:disc ratio|
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| Discussion|| |
The evaluation of ONH is an important part of the management of glaucoma. This can be done clinically and also stereoscopically using various modern and sophisticated devices like optical coherence tomography, Heidelberg retinal tomography, and scanning laser polarimetry. However, many of these modalities require a clear media. Many studies have proposed the use of ultrasound examination as an ancillary method for the assessment of glaucoma patients, especially in cases wherein media opacity is present.,,
Winder and Atta have shown a strong correlation between optical and ultrasonic cup diameters and concluded that optic disc cups of 0.5 mm or larger could be defined by B-scan echography.
Our study aims to assess the reliability of B scan to correctly identify optic disc cupping using high-frequency B scanner.
Yousuf et al. have shown the sensitivity of low-resolution contact B scan to be 83%.
Sayed et al. in their study concluded that echographic assessment of optic nerve cupping is a useful and reproducible tool in the evaluation of pediatric patients suspected or known to have glaucoma, subject to experience of the examiner.
They further suggested that obtaining optimal B scan that takes into account measurements of optic disk size is warranted to precisely evaluate the utility of this tool.
We were able to predict ONH cupping in 16% of the patients. A higher correlation between echographic descriptions of ONH cup with increasing cup:disc ratio was found. It detected ONH cupping in 50% of patients with cup:disc ratio ≥ 0.7:1.
However, in our study, high-resolution ultrasound of 20 Hz was not used unlike other studies.
One of the limitations of our study is the fact that multiple investigators performed the ocular ultrasound. The weak point of the agreement clinically and ultrasonographically might be due in part to different reference planes.
| Conclusion|| |
Our study suggests that ultrasound echography may provide a qualitative assessment of the ONH cupping in glaucoma even in the presence of media opacity such as cataract.
The method proves useful in eyes with cup:disc ratio greater than 0.6. This is advantageous mainly in eyes with media opacity, in which clear optic media-based examinations, such as optical coherence tomography and Heidelberg retinal tomography, are unviable. However, we observed that ultrasound missed cupping in eyes especially with smaller cup:disc ratio.
B-scan ultrasonography is done as a part of routine preoperative evaluation in cases of dense cataract and assessment; the cupping is useful in prognosticating and picking up cases of glaucoma with normal IOP.
The authors sincerely thank and acknowledge the Retina Department of Sankara eye hospital, Bangalore, for their support in conducting this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]