FLORA™: Phase I development of a functional vision assessment for prosthetic vision users

Structure of the FLORA

Taking these guiding principles and challenges into account, the structure of the FLORA reflects a standard three-part approach of rehabilitation assessment: self-report, observation of performance, and case summary.

Part 1, the self-report part of the FLORA, includes 13 open-ended questions that were designed to guide a conversation to fully elicit the subject’s point of view on how the System has affected his or her life. For example:

• What would you like me to know about how the system has affected you?
• Has the system helped you do things you could not do before?

Self-report was viewed as a key element for the initial part of this work because we recognized that the implanted subjects were quickly becoming the experts on the use of the Argus II System, describing situations and experiences using the System that we had not considered. The self-report takes into consideration the patient’s point of view on the impact of the Argus II on their well-being.

While self-report is an important element of a comprehensive assessment, the demonstration of skills in the presence of an experienced observer is necessary to affirm or challenge the information gathered during the self-report [19]. Part 2 of the FLORA provides the evaluator the opportunity to observe the subject performing common ADLs and O&M while using the Argus II System and without using it (i.e., using only the subject’s residual vision). To choose the tasks, the team identified activities that both required vision for all or some portion of the task and had the potential to be improved with the range of vision provided by the System. Selected tasks ranged from some that could likely be performed successfully with light perception or projection only (locate a light source, find an open doorway, determine if lights are on/off), through the spectrum of ultra-low vision, to those tasks that likely require higher levels of movement, spatial, or form vision for successful completion (recognize shapes, estimate the size of an object). Activities such as reading 12-point print, identifying the color of a traffic light, or identifying individual faces require a level of vision generally beyond that afforded by the System, and were thus not included.

The list of tasks was then organized into 5 categories beginning with Body Awareness and Orientation. This category, intended to measure subjects’ general spatial orientation skills (System OFF only), was included in order to provide the evaluator with an understanding of the subject’s spatial abilities without the input of the Argus II System. It includes tasks such as “demonstrate awareness of head and eye position”, and “use directional and positional concepts (N, S, E, W, clockwise, counter-clockwise)”. The next category, Visual Orientation, evaluates the ability to use light projection and contrast to detect the location of lights, windows, and doors. The third category addresses using vision for mobility (e.g., independently cross residential streets by following the lines of a crosswalk; avoid obstacles while walking) and the fourth assesses Daily Living Tasks, with emphasis on the visual aspects of the tasks (e.g., visually locate/identify things in the bathroom; sort light from dark laundry). Blindness is known to be socially isolating[20-26], so the fifth category was added to evaluate visual tasks having to do with social interaction (e.g., visually detecting the presence of others in a room; determining the direction of movement of people walking by).

The evaluators were instructed to observe the subject performing each assessed task with the System ON and with it OFF, using as many trials as necessary to render a judgment about how difficult the task is for the subject to complete. The evaluators were encouraged to select which tasks to observe, basing the choice on the subject’s self-reported abilities (and goals) as well as his or her performance on previous tasks. Therefore, the assessment was customized for each subject.

For each task observed, the evaluators ranked the ease of performance as impossible, difficult, moderate, or easy. In addition, they estimated how much vision was used to accomplish the task: no vision, some vision, or vision only.

Part 3 is a narrative case report summarizing the findings of the interview and the observations. The purpose was to encourage the evaluator to synthesize the information into a coherent report that provides their insights into the effect of re-introducing vision to the lifestyle of this particular subject, and to identify activities where rehabilitation could improve their use of the technology. The case report documents evaluators' findings from two points of view: functional vision effects they observed, and the subject’s self-reported general observations of well-being and satisfaction (or displeasure).

Subjects

The FLORA was administered to subjects participating in the Argus II Retinal Prosthesis System clinical trial. This multi-center study is being conducted in accordance with the Declaration of Helsinki and the national regulations for medical device clinical trials in the countries in which the study is being conducted. The study has been approved by the national ministries of health in these countries and the Ethics Committees or Institutional Review Boards of participating institutions. All subjects signed informed consent to participate. The clinical trial is posted on www.clinicaltrials.gov, trial registration number {"type":"clinical-trial","attrs":{"text":"NCT00407602","term_id":"NCT00407602"}}NCT00407602.

The Argus II clinical trial enrolled 30 subjects with 14 from the United States and 16 from Europe. Twenty nine subjects had retinitis pigmentosa and 1 had choroideremia All subjects had long standing blindness, reaching bare light perception an average of 15.9 years prior to enrolling in the trial. The FLORA was administered on 26 subjects. One subject had been explanted and three subjects declined to participate.

There were seven evaluators (DG, MF, NT, MB, AF, MG, LF). All evaluators were qualified in the areas of rehabilitation for the blind, orientation and mobility, or occupational therapy and participated in a training session on the implementation of the FLORA. All evaluators were reimbursed for their time and expenses.

Procedures

The FLORA was administered to the 26 participating Argus II subjects between December 1, 2010 and April 8, 2011. To perform the FLORA, evaluators typically spent 3-4 hours with each subject at and/or near the subject’s home.

Usage of the FLORA

By allowing evaluators to customize each assessment – select the questions and tasks they believed would be relevant to each particular Argus II subject – we were able to use their selections as a reflection of the appropriateness of the questions and tasks in the FLORA. The results suggest the Part 1 interview includes mostly relevant questions, with the vast majority of interviews covering all 14 questions.

Most of the Part 2 tasks also appeared to be useful and appropriate for this ultra-low vision population, with all 35 items being tested on some subjects (low of 5), and six tasks being evaluated on all 26 subjects. The results also demonstrate that we avoided both floor and ceiling effects; evaluators made use of the full rating scale, with a distribution of scores from impossible (33%) to easy (19%). No correlations or trends were found between the number of tasks evaluated and several possible explanatory factors, including the percent of task rated as easy, and the list number of each item. While this may be a result of the small N, it does suggest that evaluators were not overly influenced by the perceived difficulty of the task or the order in which it appeared on the FLORA form.

Since the purpose of the clinical trial was to evaluate the effectiveness of the Argus II as a technology to re-introduce vision to the blind, we asked the assessors to indicate when, in their judgment, vision was and was not being used to complete the tasks, as shown in Table 1. The “amount of vision used” rating in System ON conditions was skewed toward tasks in which only vision was used (75%) rather than tasks performed with additional cues such as tactile or auditory information. This was by design; our task selection was deliberately biased towards tasks that require vision to be performed accurately. As discussed above, the clinical trial subjects had established mechanisms for coping with their blindness, and many everyday tasks could be performed faster and/or more accurately without vision. Choosing these tasks but requiring that subjects perform them visually would not represent a true test of the impact of the System on subjects’ lives and it would not accurately represent how they functioned. Including only the types of tasks usually found on low-vision functional vision assessments such as the NEI-VFQ or the Activity Inventory, however, would result in a failure to measure an impact at all, which was contrary to what we were hearing from subjects about the effect of the System.

Table 1 also indicates that some visual tasks could be performed with the system OFF by an average of 29% of subjects evaluated. Since one of the criteria for acceptance into the clinical trial was residual vision of bare light perception or worse, we assume these subjects were using their remaining native vision. There are also a number of activities -- using the sun to determine orientation (sensing heat of sun); travel within home independently (familiar environment) -- which can be accomplished without vision. As a last comment on the use of vision, some tasks, specifically detecting curbs and identify top/bottom step were assessed with vision only – no long cane – but this was done by certified O&M instructors and should not be assessed by evaluators not trained in O&M.

Financial Support: This work was supported by NIH EY020778 and NIH EY021220.