Morpho-functional analysis of Stargardt Disease for reading.

OBJECTIVE: To analyze Stargardt disease (STGD) by morpho-functional examination and investigate the relationship between morpho-functional measures and reading performance. DESIGN: Observational case series study. PARTICIPANTS: Fifteen patients with STGD. METHODS: Twenty-six eyes of 15 patients underwent complete ophthalmic evaluation. Spectral domain optical coherence tomography, fundus autofluorescence (FAF), best corrected visual acuity (BCVA), and microperimetric examinations were performed. FAF and optical coherence tomography (OCT) overlap on microperimetric images was obtained in order to evaluate both tomographic and FAF features passing through the eccentric fixation area. Both morphologic features and functional data were correlated with magnification of prescribed device and reading rate. RESULTS: Univariable analysis showed a significant correlation between magnification power and greatest linear dimension of both OCT and FAF (r = 0.69 and r = 0.67; p < 0.05). Magnification power was related to best corrected visual acuity (r = 0.56; p < 0.05). Retinal sensitivity map (r = 0.57; p < 0.05) was considered an indicator of reading rate. Magnification levels showed a positive correlation with eccentric preferred retinal location (p = 0.03) and the degree of FAF alteration (normal, dishomogeneous, ipoautofluorescence; p < 0.0001). CONCLUSIONS: As a result of the overlapping of OCT/FAF imaging on microperimetric exam, residual activity of outer retinal layers passing through the eccentric fixation area seems to be related with required magnification and reading rate. Identification of morpho-functional parameters is helpful for designing a customized rehabilitative program.

Rehabilitative approach in patients with ring scotoma.

OBJECTIVE: To investigate the rehabilitative approach in patients with ring scotoma. A central scotoma is characteristic for patients with age-related macular degeneration (AMD). Sometimes patients with AMD maintain a residual central vision area within the scotoma (ring scotoma). DESIGN: Prospective, nonrandomized case series. PARTICIPANTS: Twenty-four patients with AMD. METHODS: A formal low-vision assessment was performed for all study patients. The assessment included best corrected visual acuity (BCVA), contrast sensitivity, reading speed, and microperimetry. All patients were provided a low-vision assessment to satisfy patients' needs. Devices were prescribed accordingly. RESULTS: The BCVA found was 0.4 logMAR (SD 0.1). All had central and stable fixation. Residual central retinal area size and sensitivity measured 2.4° (SD 0.8) and 3.1 dB (SD 0.8), respectively. Twenty patients achieved better vision with optical magnification in the eye with ring scotoma. Mean reading speed achieved was 50.2 words/min (SD 20.9). A linear correlation was found for reading speed with both central area sensitivity (r² = 0.5, p < 0.05) and contrast sensitivity (r² = 0.3, p < 0.05). CONCLUSIONS: In patients with AMD with ring scotoma, moderate amounts of magnification seem to provide satisfactory rehabilitation outcomes. Central retinal spared area sensitivity may predict reading speed outcomes, whereas residual central area size is likely to be useful in determining magnification.

Biofeedback stimulation in patients with age-related macular degeneration: comparison between 2 different methods.

OBJECTIVE: To evaluate changes in patient's visual performance after rehabilitation training with 2 different biofeedback training programs offered by the MP-1 microperimeter. Spontaneous retinal location of preferred retinal loci (PRLs) and fixation stability are not always optimal for best visual performances. MP-1 microperimeter biofeedback techniques have been suggested as modalities for training for better fixation stability and to find a better location of the new PRL in a more useful area of the retina in nonoptimal cases. The MP-1 microperimeter offers different biofeedback strategies, such as acoustic biofeedback and structured light stimulus plus acoustic biofeedback. DESIGN: Retrospective study. PARTICIPANTS: Thirty subjects affected by age-related macular degeneration with absolute central scotoma. METHODS: A standard protocol of examination before and after visual rehabilitation training was performed on all study subjects. Assessment included demographics data, visual acuity, fixation stability, retinal sensitivity, and reading speed. Rehabilitation training was performed with standard and structured stimulus biofeedback. The whole sample was divided into 2 groups of 15 patients attending the 2 different stimulation training biofeedback. RESULTS: Mean reading speed was found to be significantly increased for both groups (p < 0.05 and p < 0.01). Also, a statistically significant improvement of fixation stability was registered for both groups (p < 0.01). Only patients trained with the flickering pattern biofeedback stimulation increased retinal sensitivity (p < 0.01). CONCLUSIONS: Both regular biofeedback and flickering pattern biofeedback training seem to improve visual functions. More benefits seem to be accrued, however, with flickering pattern biofeedback training.

Relationship between fixation stability measured with MP-1 and reading performance.

BACKGROUND: People with visual impairment have reduced reading performance, which is thought to be related to unstable or eccentric fixation. New microperimeters such as the MP-1 offer straightforward analysis of fixation stability. The aim of this study was to investigate the relationship between fixation stability and reading speed in a large cohort of people with diverse causes of visual impairment and to verify the correlation between reading speed and different methods for the quantification of fixation. METHODS: The better eye of one hundred and twenty subjects was assessed. Fixation values were obtained from the MP-1 microperimeter. Reading speed was evaluated using newspaper text with magnifiers if required. RESULTS: The poorest fixation stability and reading performance was found in people with age-related macular degeneration while the best fixation was in retinitis pigmentosa subjects. A linear relationship was found between reading speed and the proportion of fixations within 2° (r² = 0.51, p < 0.001) and 4° (r² = 0.36, p < 0.001). A negative correlation was found between reading speed and all three bivariate contour ellipse areas (BCEA; for log transformation of 1-S.D., 2-S.D. and 3-S.D.: r² = 0.39, p < 0.001). In a multiple regression model, proportion of points falling within 2° and 4° circle was significantly related to reading speed (r² = 0.55, p < 0.01; r² = 0.43 p < 0.01); also BCEAs values were strongly related to reading ability only in patients with central vision loss (r² = 0.62, p < 0.01 for LogBCEA 68.2%; r² = 0.61, p < 0.01 for LogBCEA 95.4% and 99.6%) and peripheral defect (r² = 0.52, p < 0.01 for LogBCEA 68.2%; r² = 0.50, p < 0.01 for LogBCEA 95.4%; r² = 0.49, p < 0.01 for LogBCEA 99.6%) but not in combined defect subjects. CONCLUSIONS: The study confirms that in people with visual impairment the reduced reading performance is correlated with fixation instability. Moreover, there is a strong relationship between reading speed and both the proportion of fixations falling within 2° and 4° and bivariate contour ellipse area values.