Comparison of retinal thickness by Fourier-domain optical coherence tomography and OCT retinal image analysis software segmentation analysis derived from Stratus optical coherence tomography images.

PURPOSE: To compare thickness measurements between Fourier-domain optical coherence tomography (FD-OCT) and time-domain OCT images analyzed with a custom-built OCT retinal image analysis software (OCTRIMA). METHODS: Macular mapping (MM) by StratusOCT and MM5 and MM6 scanning protocols by an RTVue-100 FD-OCT device are performed on 11 subjects with no retinal pathology. Retinal thickness (RT) and the thickness of the ganglion cell complex (GCC) obtained with the MM6 protocol are compared for each early treatment diabetic retinopathy study (ETDRS)-like region with corresponding results obtained with OCTRIMA. RT results are compared by analysis of variance with Dunnett post hoc test, while GCC results are compared by paired t-test. RESULTS: A high correlation is obtained for the RT between OCTRIMA and MM5 and MM6 protocols. In all regions, the StratusOCT provide the lowest RT values (mean difference 43 ± 8 µm compared to OCTRIMA, and 42 ± 14 µm compared to RTVue MM6). All RTVue GCC measurements were significantly thicker (mean difference between 6 and 12 µm) than the GCC measurements of OCTRIMA. CONCLUSION: High correspondence of RT measurements is obtained not only for RT but also for the segmentation of intraretinal layers between FD-OCT and StratusOCT-derived OCTRIMA analysis. However, a correction factor is required to compensate for OCT-specific differences to make measurements more comparable to any available OCT device.

Retinal layer thickness changes in eyes with preserved visual acuity and diffuse diabetic macular edema on optical coherence tomography.

BACKGROUND AND OBJECTIVE: Diabetic macular edema has several patterns on optical coherence tomography. This retrospective study aimed to assess which retinal layers show thickness changes in type 1 diffuse diabetic macular edema with preserved vision. PATIENTS AND METHODS: Eleven eyes with diffuse diabetic macular edema on optical coherence tomography and eight control eyes with 20/20 best-corrected visual acuity were enrolled. Optical coherence tomography images were segmented using an algorithm of the authors' design (OCTRIMA): regional thickness data in the central area, pericentral rings, and peripheral rings were obtained for the retinal cellular layers. RESULTS: The retinal nerve fiber layer showed no changes, the ganglion cell and inner plexiform composite layer and the ganglion cell complex were thicker only in the pericentral regions, and all other layers were thicker in all regions in diffuse diabetic macular edema. Macular thickness was normal in the peripheral region. CONCLUSION: The results show that the outer retina in the foveal area is the most affected in diffuse diabetic macular edema.

Role of multifocal electroretinography in the diagnosis of idiopathic macular hole.

PURPOSE: To analyze the preoperative results of multifocal electroretinography (mfERG) in the fellow eyes of patients with idiopathic unilateral macular hole and to evaluate the usefulness of this method in predicting the likelihood of macular hole formation in the fellow eye. METHODS: Over a period of 5 years, 80 eyes of 40 patients (mean age, 64.9 years) with unilateral idiopathic macular hole were examined. The diagnosis of idiopathic macular hole was confirmed by optical coherence tomography (OCT). The fellow eyes were intact in all cases. All patients underwent vitreoretinal surgery. Before the surgery, both eyes of the patients were examined by mfERG. During the follow-up period, the 40 fellow eyes were also observed by OCT, and the changes in the vitreofoveal attachment were investigated. The preoperative response densities and ring ratios of mfERG were analyzed in both eyes, and discriminant analysis was used to calculate the best separator function. RESULTS: Preoperative mfERGs demonstrated significantly lower mean response densities in the central area of the 40 eyes with macular hole than in the fellow eyes. During the follow-up period, macular hole was diagnosed in 13 fellow eyes by OCT. The preoperative values of the mfERGs in these eyes were significantly lower than in the other 27 cases. The mfERG ring ratios were significantly lower in the fellow eyes in which macular holes developed than in those that remained intact. CONCLUSIONS: The analysis of ERG in the fellow eyes of patients with macular hole seems clinically useful. The lower amplitude may forecast the propensity for subsequent development of a macular hole. Patients with low central ERG amplitude and lower ring ratios in the healthy fellow eyes should have stricter follow-up.

Reliability and reproducibility of macular segmentation using a custom-built optical coherence tomography retinal image analysis software.

We determine the reliability and reproducibility of retinal thickness measurements with a custom-built OCT retinal image analysis software (OCTRIMA). Ten eyes of five healthy subjects undergo repeated standard macular thickness map scan sessions by two experienced examiners using a Stratus OCT device. Automatic/semi automatic thickness quantification of the macula and intraretinal layers is performed using OCTRIMA software. Intraobserver, interobserver, and intervisit repeatability and reproducibility coefficients, and intraclass correlation coefficients (ICCs) per scan are calculated. Intraobserver, interobserver, and intervisit variability combined account for less than 5% of total variability for the total retinal thickness measurements and less than 7% for the intraretinal layers except the outer segment/ retinal pigment epithelium (RPE) junction. There is no significant difference between scans acquired by different observers or during different visits. The ICCs obtained for the intraobserver and intervisit variability tests are greater than 0.75 for the total retina and all intraretinal layers, except the inner nuclear layer intraobserver and interobserver test and the outer plexiform layer, intraobserver, interobserver, and intervisit test. Our results indicate that thickness measurements for the total retina and all intraretinal layers (except the outer segment/RPE junction) performed using OCTRIMA are highly repeatable and reproducible.

Intraocular lens power calculation for combined cataract surgery, vitrectomy and peeling of epiretinal membranes for macular oedema.

PURPOSE: This study aimed to compare preoperatively calculated and postoperatively achieved refraction following phacoemulsification and intraocular lens (IOL) implantation combined with pars plana vitrectomy with internal limiting membrane or epiretinal membrane removal. METHODS: Twelve eyes of 12 patients who underwent a combined procedure were enrolled in this study. Ultrasound axial length and macular thickness (optical coherence tomography, OCT) measurements were performed pre- and postoperatively. Intraocular lens power was calculated with the SRK/T formula and the planned refraction was compared with results of postoperative automatic refractometry. Comparisons between IOL calculations using the measured axial length and calculations using an adjusted axial length (by adding the macular thickness measured on OCT to the ultrasound axial length) were also performed. RESULTS: Axial length increased (p = 0.02), whereas macular thickness decreased (p = 0.002). The planned refraction was 0.63 +/- 0.38 dioptres, whereas the postoperative refraction error was - 0.16 +/- 0.48 D (p = 0.02), with a mean difference of - 0.79 +/- 0.24 D. During case-to-case comparisons, differences were observed between IOL calculations using the measured axial length and calculations using an adjusted axial length (0.63 +/- 0.38 D versus 0.13 +/- 0.48 D, p = 0.005). Correlation analysis showed a significant relationship between the 'adjusted planned' and the measured postoperative ametropia (r = 0.93, p < 0.001). CONCLUSIONS: The observed myopic shift due to erroneous IOL calculation results from underestimation of the axial length due to a thicker macula and calls for preoperative adjustment of ultrasound axial length when biometry is performed by this method.

Functional assessment of the possible toxicity of indocyanine green dye in macular hole surgery.

PURPOSE: To evaluate the possible toxicity of indocyanine green (ICG) dye in macular hole surgery by comparing functional results after successful surgeries performed with and without staining. DESIGN: Prospective observational case series. METHODS: In a study conducted at our department, 30 eyes of 29 patients with idiopathic macular hole underwent pars plana vitrectomy, with peeling of the internal limiting membrane (ILM). In 21 eyes (group A), ICG staining was used to visualize the membrane; in nine eyes (group B), no dye was applied. Pre- and postoperative examinations (at three, six, 12, and 20 months) included visual acuity (VA) (Snellen chart), slit-lamp biomicroscopy, multifocal electroretinography (mfERG), and optical coherence tomography (OCT). For statistical analysis, the Mann-Whitney U test and Newman-Keuls post hoc analysis were used. RESULTS: The macular hole was closed in all patients. At 20 months, VA improvement (logarithm of minimal angle of resolution units) compared with baseline was more pronounced in group B (P < .001) than in group A (P = .022); VA was also better for group B compared directly with group A (P = .048). For mfERG, preoperative responses were subnormal. Postoperatively, responses initially decreased, but at 20 months significant improvement was seen in both groups (P < .001). When data from the groups are compared at 20 months, significantly greater mfERG improvement was found in group B in both central and perimacular areas (P < .001). CONCLUSIONS: The significantly better outcomes without staining may suggest dye toxicity. Alternative internal limiting membrane visualization substances with fewer adverse effects (trypan blue, triamcinolone) may be preferable.