Laser Scanning Imaging for Macular Disease

Precision of Epithelial Defect Measurements

PURPOSE

To ensure optimal care of patients, cornea specialists measure corneal features, including epithelial defects (ED), with slit-lamp calipers. However, caliper measurements are subject to interphysician variability. We examined the extent of variability in ED measurements between cornea specialists and discuss the potential clinical impact.

METHODS

A total of 48 variably sized EDs were created in pig eyes. Three cornea specialists measured the maximum vertical and horizontal ED lengths to the nearest 10th of a millimeter using slit-lamp microscopy. An absolute difference in ED measurement between cornea specialists of 0.5 mm was chosen to be the a priori threshold for clinical significance and was evaluated by the Wilcoxon signed-rank test. Interrater reliability was assessed by intraclass correlation coefficients.

RESULTS

The average absolute difference in the vertical ED length between pairs of examiners ranged from 0.54 to 0.63 mm, and that of the horizontal ED length ranged from 0.44 to 0.46 mm. These differences in ED measurement were not significantly different from 0.5 mm (all P > 0.06). However, pairs of examiners differed in vertical ED length measurements by >0.5 mm in 44% to 52% of EDs and by >1.0 mm in 13% to 17% of EDs. Pairs of examiners differed in horizontal ED length measurements by >0.5 mm in 31% to 40% of EDs and by >1.0 mm in 10% to 15% of EDs. The intraclass correlation coefficient was 0.85 (95% confidence interval, 0.77-0.91) for vertical and 0.84 (95% confidence interval, 0.74-0.90) for horizontal ED measurements.

CONCLUSIONS

Cornea specialists showed good reliability in the measured EDs; however, depending on the threshold for clinical significance, a nontrivial percentage of cases have high interexaminer clinical variability.

Diabetic Retinopathy Clinical Practice Guidelines: Customized for Iranian Population

PURPOSE

To customize clinical practice guidelines (CPGs) for management of diabetic retinopathy (DR) in the Iranian population.

METHODS

Three DR CPGs (The Royal College of Ophthalmologists 2013, American Academy of Ophthalmology [Preferred Practice Pattern 2012], and Australian Diabetes Society 2008) were selected from the literature using the AGREE tool. Clinical questions were designed and summarized into four tables by the customization team. The components of the clinical questions along with pertinent recommendations extracted from the above-mentioned CPGs; details of the supporting articles and their levels of evidence; clinical recommendations considering clinical benefits, cost and side effects; and revised recommendations based on customization capability (applicability, acceptability, external validity) were recorded in 4 tables, respectively. Customized recommendations were sent to the faculty members of all universities across the country to score the recommendations from 1 to 9.

RESULTS

Agreed recommendations were accepted as the final recommendations while the non-agreed ones were approved after revision. Eventually, 29 customized recommendations under three major categories consisting of screening, diagnosis and treatment of DR were developed along with their sources and levels of evidence.

CONCLUSION

This customized CPGs for management of DR can be used to standardize the referral pathway, diagnosis and treatment of patients with diabetic retinopathy.

Diabetic retinopathy: current concepts and emerging therapy

More Americans become blind each year from microvascular complications of diabetes than from any other cause. Several studies have indicated that tight glucose control and lifestyle modification can dramatically reduce the incidence and prevalence of diabetic retinopathy. Research over the past several years has yielded a tremendous increase in our knowledge of the pathogenesis of the damage to the retina that occurs in diabetes and has facilitated our ability to intervene and control the damage. New intravitreal medical therapies supported by government- and industry-supported research are gradually replacing standard laser photocoagulation for the treatment of all forms of retinopathy.

[Measurement of retinal thickness with the Heidelberg retina tomograph for patients with macular edema and healthy individuals]

BACKGROUND

This study was carried out to test the reliability of a defined cut-off value for retinal thickness with estimation of the sensitivity, specificity and formation of an edema index in comparison to retinal thickness.

MATERIALS AND METHODS

This was a single center prospective clinical non-blinded study of 100 eyes, including 22 eyes with central vein or branch vein occlusions, 20 eyes with diabetic macular edema, 6 eyes with postoperative macular edema, 2 eyes with uveitis and 50 healthy eyes. Detection of macular edema was carried out by third generation optical coherence tomography. Using the latest version of the Heidelberg retina tomograph (HRT 3) series of five images were produced and evaluated. The 9-zone circle of the HRT was used as the analysis contour.

RESULTS

The reliability of measuring retinal thickness with the HRT in the subjects showed an intraclass correlation between 0.248 and 0.740 and patients with macular edema showed values between 0.515 and 0.949. The reliability of the edema index with the HRT in the subjects showed an intraclass correlation between 0.461 and 0.826 and patients with macular edema showed values between 0.383 and 0.826. The calculated cut-off values were between 285 µm and 360 µm. The corresponding sensitivity values were between 74.7% and 95.9% with a corresponding specificity of 74.7-90.2%. There was also a highly significant correlation between the edema index and retinal thickness (p < 0.001).

CONCLUSIONS

The retina module of the latest generation HRT is capable of reproducible measurement of the retinal thickness in micrometers. The defined cut-off values correspond to expectations and can be used in this form in the clinical practice.

Scanning laser edema index: a reliable tool to correlate with diabetic retinopathy and systemic risk factors?

To correlate Heidelberg Retina Tomograph (HRT) derived macular edema (DME) index with severity of diabetic retinopathy and systemic factors. A total of 300 diabetic patients were recruited for the study for each of them a value for the macular edema index was obtained using the HRT II. Patients' age, gender, duration and type of diabetes mellitus, latest HbA1c result and presence or absence of co-morbid factors (hypertension, ischemic heart disease, nephropathy) were recorded together with the stage of diabetic retinopathy. These were correlated with DME. Out of 300 patients, HRT defined macula edema was seen in 68 patients (22.6%). There is a wider and higher range (95% percentile) of macula edema index in the severe non proliferative diabetic retinopathy (NPDR) group. Independent samples t test showed significant difference between the severe NPDR group and no DR group (p<0.001), mild NPDR group (p<0.05) and moderate NPDR group (p<0.05). A higher macula edema index was also found to have a low degree of correlation with more advanced stages of retinopathy (r=0.310; p<0.001). Also nephropathy showed a strong and significant correlation with DME. Hypertension had moderately significant correlation with DME. This study found no correlation between ischemic heart disease and DME. HRT derived scanning laser edema index is a reliable objective tool to evaluate diabetic retinopathy and systemic risk factors.