A recent study published in Ophthalmology Science tests the effectiveness of eccentric viewing training on improving vision in patients with age-related macular degeneration (AMD).
Give me some background first.
For individuals with macular disease and central vision loss, non-central retina must be used to see.
Within six months of vision loss, the preferred retinal locus (PRL) is used in place of the damaged fovea.
While some clinicians recommend eccentric viewing (EV) for patients with macular disease to improve PRL and fixation stability, there is not enough strong evidence in support of EV training at the moment.
Which leads us to …
This study aimed to measure the effects of EV on visual function, which was measured through:
- Visual task ability
- Reading performance
- Fixation stability
Now talk about this study.
A total of 682 patients with AMD were identified to meet the inclusion criteria from low vision clinics at Moorfields Eye Hospital. Of that number, 200 were selected to participate.
The Eccentric Fixation From Enhanced Clinical Training trial method was used, which utilized a randomized controlled trial (RCT) to compare two models of eccentric viewing training:
- Training at the PRL
- Biofeedback training at the trained retinal locus (TRL)
What were the primary and secondary outcome measures?
The primary outcome measure was visual task ability, which was assessed using Activity Inventory (AI)—a visual function questionnaire widely used in low vision research that asks participants to report their ability to perform 50 different actions.
Secondary outcome measures included:
- Reading performance, evaluated using the MNREAD test and Morgan Low Vision Reading Comprehension Assessment test.
- Fixation stability, tested using a Nidek MP-1 microperimeter.
Findings?
No significant effect of EV training was observed on task ability, reading performance, or fixation stability.
Give me specifics.
On average, visual acuity (VA) decreased by 0.20 logMAR (mean [SD] = 0.47) and contrast sensitivity decreased by 0.18 log units (SD = 0.34).
The deterioration in VA and contrast sensitivity demonstrated the difficulty of rehabilitating vision in patients with a disease that progressively worsens vision.
Further, there was no significant difference in VA or contrast sensitivity between those with dry AMD and wet AMD.
How did this compare to previous studies?
This study did not report the improvements in visual function that some previous research has found. Study authors identified four possible reasons this may have occurred.
- Treatment times.
- Wide variability in recommended treatment times
- Greater training time may have led to more noticeable outcomes.
- Data of 24 participants who did not complete all training sessions were included in the results, even though this may minimize effectiveness of EV training.
- EV training experience.
- EV training was administered by experienced low vision optometrists (ODs) who received instructions from an experienced EV trainer.
- However, these ODs did not have prior experience with EV training.
- EV trained administrators may have altered study results.
- EV training was administered by experienced low vision optometrists (ODs) who received instructions from an experienced EV trainer.
- Customized training.
- Every participant received the same training.
- However, EV training can be tailored to individual patients in clinical practice, which may improve results.
- Every participant received the same training.
- Inclusion criteria.
- Participants had a broad range of VA.
- Restricting VA inclusion criteria may have yielded more results in favor of EV training.
Limitations?
A large number of patients declined to participate in the study possibly due to the time cost of traveling—potentially excluding individuals who greatly needed training but were least able to engage in the study.
As some participant groups were not asked to keep a journal of their exercises, some individuals may not have not completed all exercises—especially if they did not notice any immediate improvements.
Expert opinion?
This study does not offer strong evidence that EV training significantly improves reading ability and suggests that any possible improvements from training is overshadowed by disease progression.
The study authors concluded that these “results do not support the routine use of eccentric viewing training for people with progressing age-related macular disease, although this training may help people with end-stage disease.”