Ultrasonic examination in severe diabetic eye disease

Diabetic Macular Oedema Guidelines: An Australian Perspective

The number of people living with diabetes is expected to rise to 578 million by 2030 and to 700 million by 2045, exacting a severe socioeconomic burden on healthcare systems around the globe. This is also reflected in the increasing numbers of people with ocular complications of diabetes (namely, diabetic macular oedema (DMO) and diabetic retinopathy (DR)). In one study examining the global prevalence of DR, 35% of people with diabetes had some form of DR, 7% had PDR, 7% had DMO, and 10% were affected by these vision-threatening stages. In many regions of the world (Australia included), DR is one of the top three leading causes of vision loss amongst working age adults (20-74 years). In the management of DMO, the landmark ETDRS study demonstrated that moderate visual loss, defined as doubling of the visual angle, can be reduced by 50% or more by focal/grid laser photocoagulation. However, over the last 20 years, antivascular endothelial growth factor (VEGF) and corticosteroid therapies have emerged as alternative options for the management of DMO and provided patients with choices that have higher chances of improving vision than laser alone. In Australia, since the 2008 NHMRC guidelines, there have been significant developments in both the treatment options and treatment schedules for DMO. This working group was therefore assembled to review and address the current management options available in Australia.

Imaging in diabetic retinopathy

While the primary method for evaluating diabetic retinopathy involves direct and indirect ophthalmoscopy, various imaging modalities are of significant utility in the screening, evaluation, diagnosis, and treatment of different presentations and manifestations of this disease. This manuscript is a review of the important imaging modalities that are used in diabetic retinopathy, including color fundus photography, fluorescein angiography, B-scan ultrasonography, and optical coherence tomography. The article will provide an overview of these different imaging techniques and how they can be most effectively used in current practice.

Axial ultrasound B-scans of the entire eye with a 20-MHz linear array: correction of crystalline lens phase aberration by applying Fermat's principle

In ophthalmic ultrasonography the crystalline lens is known to be the main source of phase aberration, causing a significant decrease in resolution and distortion effects on axial B-scans. This paper proposes a computationally efficient method to correct the phase aberration arising from the crystalline lens, including refraction effects using a bending ray tracing approach based on Fermat's principle. This method is used as a basis to perform eye-adapted beamforming (BF), with appropriate focusing delays for a 128-element 20-MHz linear array in both emission and reception. Implementation was achieved on an in-house developed experimental ultrasound scanning device, the ECODERM. The proposed BF was tested in vitro by imaging a wire phantom through an eye phantom consisting of a synthetic gelatin lens anatomically set up in an appropriate liquid (turpentine) to approach the in vivo velocity ratio. Both extremes of accommodation shapes of the human crystalline lens were investigated. The performance of the developed BF was evaluated in relation to that in homogeneous medium and compared to a conventional delay-and-sum (DAS) BF and a second adapted BF which was simplified to ignore the lens refraction. Global expectations provided by our method with the transducer array are reviewed by an analysis quantifying both image quality and spatial fidelity, as well as the detrimental effects of a crystalline lens in conventional reconstruction. Compared to conventional array imaging, the results indicated a two-fold improvement in the lateral resolution, greater sensitivity and a considerable reduction of spatial distortions that were sufficient to envisage reliable biometry directly in B-mode, especially phakometry.

A chronic grey matter penumbra, lateral microvascular intussusception and venous peduncular avulsion underlie diabetic vitreous haemorrhage

The landmark publications that gave such impetus to our understanding of proliferative diabetic retinopathy are reviewed in the light of more recent reports. Briefly, confluence of small areas of capillary closure in the midperipheral and peripheral retina results in arteriovenous shunting and abnormal oxygen partial pressure gradients. These gradients embrace a chronic ischaemic penumbra that stimulates neuroglial secretion of angiogenic growth factors and upregulation of their receptors in the retinal venous endothelium and adventitia. The blood shunting produces biomechanical stresses within the veins and induces microvascular intussusception near arteriovenous crossings, giving way to neovascular outgrowths and/or segmental venous lesions (such as omega loops and coils) that penetrate the inner limiting lamina. The lamellar collagenous matrix of the vitreous cortex is then exploited for integrin-dependent rete expansion along chemotactic gradients. During posterior vitreous detachment, haemorrhaging takes place from the arterialised veins as venous neovascular peduncles are avulsed.

Ocular echography in the prognosis of vitreous haemorrhage in type II diabetes mellitus

PURPOSE

In this study, we have attempted to demonstrate the presence of various echographic parameters which could be associated with a non-spontaneous resorption of vitreous haemorrhage in type II diabetes mellitus and correlate these parameters with clinical outcome.

SUBJECTS AND METHODS

We studied 297 eyes of 257 patients with diabetic retinopathy and vitreous haemorrhage without tractional macular retinal detachment ophthalmoscopically and echographically. Of the total eyes studied, a 3-month follow-up visit (including ultrasound) was available in 208 eyes. We retrospectively reviewed the medical records of each patient.

RESULTS

The echographic parameters associated with non-resorption of the vitreous haemorrhage were: extramacular tractional retinal detachment, fibrovascular membranes and location of the haemorrhage within the subhyaloidal space (in contrast to within the intragel space). In addition, the duration of the vitreous haemorrhage and the presence of panretinal laser photocoagulation at the time of presentation with a vitreous haemorrhage influenced the resolution of the vitreous haemorrhage. We were also able to construct a logarithmic function that could be used to predict the prognosis of a vitreous haemorrhage in type II diabetes mellitus.

CONCLUSIONS

When employed to evaluate vitreous haemorrhages in non-insulin-dependent diabetes mellitus, ocular ultrasound can provide useful prognostic information regarding the lack of resorption of vitreous haemorrhages in type II diabetics.

The history of ultrasound techniques in ophthalmology

The history of 50 years of applications of ultrasound in ophthalmology is described. This period started in 1938 with a study of the possible effects of high intensity ultrasound on eyes. The measurement of biological effects for the assessment of potential hazards characterizes the first decades. More recently, the therapeutic use of ultrasound by hyperthermia has gained much interest in ophthalmology. Further topics are: the measurement of acoustic characteristics of ocular tissues; the biometry of the eye ball, the results of which are used to calculate the optical power of artificial lens implants; the development of diagnostic instruments in various parts of the world; and ultrasonic tissue characterization for the differential diagnosis of pathology. The final topic is concerned with some recent developments which present a look into the future.

A vitreoretinal service

Many serious disorders that threaten eyesight can now be treated with vitreoretinal surgery. As there was no regional facility for this treatment a service was developed to provide it. Among the first 100 patients treated over half had diabetic vitreoretinal disease. The remainder had ocular trauma (15), non-diabetic vasculopathy (10), rhegmatogenous retinal detachment (10), and miscellaneous disorders including diagnostic procedures (14). Sight was improved in most cases, 27 diabetic and 21 non-diabetic patients regaining navigating vision. Few patients were made worse: one only of the 49 non-diabetic patients and 12 of the 51 diabetic patients, and none whose vision was better than the ability to count fingers before operation. The many indications for this procedure, the size of the population that could benefit (an estimated minimum of 3800 operations per year in the United Kingdom in patients with diabetes alone), and the great potential benefit of the procedure all suggest the need for regional services. These would be cost effective in preventing blindness.

Vitrectomy for diabetic eye disease

Thirty four eyes which underwent vitrectomy because of diabetic proliferative retinopathy were reviewed. The overall success rate of the operation was 62%. Excluding table top retinal detachments, which all did badly, the success rate was 72%. Grading by ultrasound was found to be helpful in; (a) planning surgical approach, (b) assessing visual outcome. The most common late complication was cataract. Extracapsular cataract extraction with implantation was found to be successful in these cases.

Ultrasonographic mapping of vitreoretinal abnormalities

We conducted a prospective study of 50 consecutive eyes to determine the accuracy of ultrasonographic mapping of vitreoretinal abnormalities. The 50 eyes, all of which had opaque media, underwent A- and B-scan ultrasonography before undergoing vitrectomy. The location and differentiation of any abnormalities were mapped on a fundus drawing sheet. At the time of vitrectomy, the surgeon independently examined the fundus and recorded his findings on a second drawing sheet. When we compared the two sets of drawings, we found that ultrasonography correctly predicted the position of the retina in 45 of 50 eyes and the presence or absence of macular detachment in 48 of 50 eyes. These two findings are particularly important to the surgeon. Ultrasonography also correctly predicted the presence or absence of posterior vitreous detachment in all 50 eyes, correctly described the exact extents of the retinal detachments in 44 of 50 eyes, and located points of vitreoretinal adhesion in 39 of 50 eyes.