Search

We present a method for calibrating the Scanning Laser Ophthalmoscope (SLO) that predicts radiant power at any of 256 grayscale values (gsv) and 12 polarized filter (polarizer) levels. Predicted power values, p(gsv), were determined by substitution into polynomials linearly transformed to old or new power at p(0) and p(255). This was compared with observed power values at 125 levels of attenuation/session. Prediction accuracy was the proportion of nonsignificant pairwise comparisons (t-test, p=0.0001). We found that power transformation between polarizers and within sessions has both linear and nonlinear characteristics. Within polarizer and between sessions, however, power transformation has linear characteristics. A 5th-degree polynomial was individually fit, at each polarizer, to session 1 power distributions of 9 gsv steps (0, 31, 63, 95, 127, 159, 191, 223, 255). When adjusted to p(255) and p(0) in new sessions, we obtained p(gsv) that predicted power at 25 gsv * 5 polarizers for 18 days with an accuracy of about 0.84. When only adjusted to p(255), predictive accuracy was 0.81.

Available output in the Scanning Laser Ophthalmoscope (SLO) may be expressed as radiant power at the beam pivot (SLO exit pupil), in units of microwatts (microW). This power corresponds to dimensions of brightness (like luminance and retinal illuminance) and to a range of related measures (like cd/m2, lm/m2, and the troland value) in both free and Maxwellian views. We demonstrate that the conversion factor power/troland=1.26*10(-3) microW and 3.15*10(-4) microW for SLO nominal visual angles 40 degrees and 20 degrees, respectively. The factor permits measured SLO power to be expressed in units of brightness and (inversely) brightnesses of everyday objects to be expressed in units of SLO power. Examples of both conversions are given. Reference to the literature demonstrates the importance of expressing SLO power in brightness terms common to everyday activities and to visual function-testing instruments besides the SLO.

Purpose: Submacular surgery for choroidal neovascularization (CNV) is under investigation in the treatment of age-related macular degeneration (AMD) and the presumed ocular histoplasmosis syndrome. Four case studies are presented to demonstrate scanning laser ophthalmoscope (SLO) testing in the pre- and postsurgical evaluation of visual function in patients with subfoveal CNV secondary to AMD, presumed ocular histoplasmosis syndrome, and submacular hemorrhage secondary to AMD., Methods: Patients underwent a visual assessment pre- and 6 months postoperatively, consisting of low vision visual acuity measurement, SLO macular perimetry of dense and relative scotomas, and analysis of the preferred retinal locus for fixation (PRL) location and ability., Results: Visual acuity, dense and relative scotoma size and location, and PRL location were compared; and relationships between anatomic and functional changes were observed. Decreases in scotoma size and improvement in PRL location and ability usually corresponded with improved visual acuity. Preoperative scotoma and PRL location guided retinotomy site selection., Conclusion: Scanning laser ophthalmoscope macular perimetry and PRL testing may be useful adjuncts in the visual assessment of submacular surgery and may advance under-standing of the effects of submacular surgery on visual function. In addition, this testing may be used to plan location of surgical interventions for macular diseases.

Purpose: To present a new method of performing scanning laser ophthalmoscope perimetry that compensates for eye movements so that the correct retinal location is tested even if fixation changes. This allows for accurate testing of patients with central scotomas and for repeating testing longitudinally at the same retinal locations even if central fixation is lost., Methods: The operator views the retina and selects a retinal landmark, such as a vessel bifurcation, that can be identified easily. A testing strategy is preselected, and the computer saves the landmark and stimulus coordinates. To present each stimulus, the operator positions a cursor over the retinal landmark, and the computer adjusts the site of presentation of the stimulus for any change in landmark position caused by an eye movement. At the conclusion of the testing, the results are displayed in the proper retinal location on a fundus image., Results: Sixty-seven eyes with macular disease were tested with the landmark-driven method, using the same preplanned strategy for each eye for both a bright and a dim stimulus. There was a low rate of inconsistent points (seen with dim but not bright stimuli), and virtually all of these bordered a dense scotoma. Those eyes with more inconsistent points had a significantly greater percentage of dense scotoma points and significantly lower visual acuity. The technique significantly corrected error in retinal localization resulting from large eye movement. There is no significant rotation or magnification change during the procedure, so specifying the change in location of one landmark is sufficient to describe movement of the retina. The technique is rapid and easy to administer to elderly patients and to children., Conclusions: This technique allows for accurate and repeatable measures of retinal sensitivity in specific locations. It is useful in following change over time. It can be developed further to allow for fully automated, retinally correct testing.