Improved visualisation of choroidal neovascularisation by scanning laser ophthalmoscope using image averaging.

AIMS: To improve visualisation of angiographic features in patients with age related macular degeneration associated with choroidal neovascularisation (CNV) and related complications. To evaluate if image averaging can achieve this goal. METHODS: 27 eyes of 20 sequential patients with age related macular degeneration over a 3 month period were studied. Indocyanine green angiograms (ICGA), fluorescein angiograms (FA), and oral fluorescein angiograms were recorded with a confocal scanning laser ophthalmoscope. Software was used to average multiple images from a 10-20 image series (over 0.5-1.0 seconds). Image quality was assessed by two masked observers and graded on a scale of 0-3. A more quantifiable grading method was devised by adding a variable amount of Gaussian noise to the improved image until the original and image averaged image appeared equal. RESULTS: Masked review showed mild to strong improvement of visualisation of structures including borders of CNV. Improvement varied depending on the type and phase of the angiogram. Improvement was highest in late phase FA, mid and late phase ICGA, and all phases of oral FA. CONCLUSION: Image averaging using software based algorithms improves the quality of angiographic images, particularly late ICGA images and oral FAs. This method may assist in the visualisation of choroidal neovascularisation in age related macular degeneration.

Duration of vitrectomy and postoperative cataract in the vitrectomy for macular hole study.

PURPOSE: To report the association between duration of vitrectomy, as well as other risk factors, and the progression of nuclear sclerosis and posterior subcapsular cataract in the Vitrectomy for Macular Hole Study. DESIGN: A cohort study nested within a randomized controlled clinical trial. METHODS: Using a system similar to the Lens Opacities Classification System II, nuclear sclerosis (NS) and posterior subcapsular cataract (PSC) were scored in the vitrectomy and fellow eye of 74 patients at baseline and at 6, 12, and 24 months postoperatively. Age, baseline blood pressure and refractive power, and duration of surgery were evaluated as risk factors for NS or PSC progression and cataract extraction. RESULTS: The incidence of NS progression in the surgical group of vitrectomy eyes was 81% at 6 months, 98% at 1 year, and 100% at 2 years of follow-up. In contrast, NS progression in the control group of fellow eyes was only 18% at 6 months, 20% at 1 year, and 8% at 2 years. The incidence of PSC progression in the surgical group remained at approximately 11% throughout follow-up, which was not significantly higher than the 3% to 5% incidence in the control group. Vitrectomy was significantly related to progression of NS cataract (P <.001) and cataract extraction (P <.01). No statistically significant differences were found for NS scores, PSC scores, or progression rates between eyes that had less than median surgical duration (60 min.) or more than the median surgical duration. Additionally, no significant differences were found when eyes that experienced 45 minutes or less surgical duration were compared with eyes that endured more than 75 minutes surgical duration. Age, blood pressure, and refractive power were not found to be predictors for NS and PSC progression. CONCLUSIONS: Although vitrectomy is a risk factor for NS progression, the duration of vitrectomy does not increase the risk.