Experimental Disorientation and Conceptual Confusion

Thirty-two subjects were examined on a visual matching task. They were tested for their ability to maintain an orientation with respect to a particular direction in the horizontal plane, while being kept in circumstances designed to minimize their input of information and create thereby some conceptual confusion.

The results suggest that subjects tend to make corrections as if they were in the same position in space throughout, even though they have no necessary reason for supposing this to be true and some reasons for supposing the opposite. It seemed that non-verbal information had to be presented to the subjects in order to suppress this tendency.

Voluntary rotation of the subject from one setting to the next produced no more than chance errors, while arbitrary rotations only produced errors when cues were inconsistent, or possibly where no cues were available at all. In the cases where no cues—or minimal cues-were available, assumptions were made by the subjects about the nature of the environment. This caused both errors and correct responses for reasons that were not justified by the evidence in the hands of the subject.

Introspective reports revealed some interesting results as to the cues utilized and concepts consciously formulated by the subjects for their use.

Radiotherapy for recurrent choroidal neovascularisation complicating age related macular degeneration

AIMS

To report the safety and visual outcome data of external beam irradiation for recurrent choroidal neovascularisation complicating age related macular degeneration.

METHODS

Eighteen consecutive eyes received external beam irradiation with seven fractions of 2 Gy (total dose 14 Gy). The next 16 consecutive eyes received external beam irradiation with five fractions of 3 Gy (total dose 15 Gy). Main outcome measure was change in visual acuity. Secondary outcome variables were contrast sensitivity and fundus photographic/fluorescein angiographic progression.

RESULTS

The 3 Gy fraction group lost fewer lines of distance visual acuity at the three and six month follow up. At one year follow up, this difference was not maintained with 2 Gy fraction and 3 Gy fraction eyes. At one year follow up a decrease in visual acuity of three or more lines (moderate visual loss) occurred in 58% of 2 Gy and 42% of 3 Gy fraction eyes (p<0.36). At one year follow up a decrease in visual acuity of six or more lines (severe visual loss) occurred in 41% of 2 Gy eyes and 17% of 3 Gy eyes (p<0.23). At three months follow up, 3 Gy eyes were less likely (0%) than 2 Gy eyes (47%) to show moderate visual loss (p<0.003). However, Kaplan Meier curves estimate a significantly lower rate of severe visual loss in the 3 Gy group (p = 0.02). There were no significant differences in contrast sensitivity loss or fluorescein angiographic stabilisation rates. No evidence of radiation toxicity was observed.

CONCLUSION

Our results are consistent with trends for a palliative benefit with higher fraction sizes and doses. The radiobiologic differences between low and high fraction size groups in this study are modest and correlate with the modest and short term difference in visual outcomes. These trends support further investigation of radiotherapy using fraction sizes of 4 Gy or higher.

External beam irradiation of subfoveal choroidal neovascularization complicating age-related macular degeneration: one-year results of a prospective, double-masked, randomized clinical trial

OBJECTIVES

To determine the effects of low-dose external beam irradiation compared with observation on the visual function of eyes with subfoveal choroidal neovascularization (CNV) complicating age-related macular degeneration (ARMD).

DESIGN

Prospective, double-masked, randomized clinical trial. Patients randomized to the radiation group received external beam irradiation at a dose of 14 Gy in 7 fractions of 2 Gy. Patients randomized to the observation group received sham radiation.

SETTING

Tertiary care retinal referral practice.

PATIENTS

Individuals with classic, mixed, or occult subfoveal CNV secondary to ARMD.

MAIN OUTCOME MEASURES

Change in visual acuity from baseline to specified time periods. Secondary outcome variables were contrast sensitivity and fundus photographic/fluorescein angiographic progression.

RESULTS

Forty-two eyes were randomized to observation; 41 eyes, to radiation. Baseline characteristics and demographics did not differ between groups. The median distance visual acuity (DVA) in radiation-treated eyes decreased from 20/80 at baseline to 20/320 (mean loss rate, 4.14 lines) at 1-year follow-up. The median DVA in observation group eyes decreased from 20/125 at baseline to 20/250 (mean loss rate, 3.39 lines) at 1-year follow-up. There were no statistically significant differences in changes in DVA, contrast sensitivity, or fluorescein angiographic progression from baseline between groups at any follow-up period.

CONCLUSIONS

At 1-year follow-up, low-dose external beam irradiation at 14 Gy in 7 fractions of 2 Gy is neither beneficial nor harmful for subfoveal CNV complicating ARMD.

Sham radiation in clinical trials assessing radiotherapy for exudative age-related macular degeneration

BACKGROUND

To evaluate the effectiveness of sham radiation treatments in masking patients to their randomization group in the Radiation of Age-Related Macular Degeneration (ROARMD) Study.

METHODS

Patients with choroidal neovascularization complicating age-related macular degeneration were randomized to a treatment (RAD) group that received external beam irradiation (seven treatment sessions) or to a control (SHAM) group that received sham radiation (one sham treatment session). During a telephone survey, 62 of 73 randomized patients responded to the following questions: Do you think you received radiation? Why do you feel that way? Did the vision in your study eye worsen after enrollment?

RESULTS

Eighty-one percent of the RAD group and 59% of the SHAM group thought that they had received radiation. In patients who thought that their vision had stabilized or improved, 82% thought that they had received radiation. In patients who thought that their vision was worse, only 39% thought that they had received radiation. In 54% of patients, subjective perception of vision influenced their guess as to whether they received radiation.

CONCLUSIONS

Subjective patient perception of visual outcome was the most influential variable for masking. Variation between radiation treatment and sham session techniques, such as equipment used and duration of treatments, played a lesser role in the masking of patients. Seven treatment days correlated with a higher number of patients who thought that they had received radiation. Although our procedures do not strictly mask the two groups, one sham radiation session was effective in keeping patients guessing their randomization group.