Measuring the Effects of Eye Alignment Surgery - a feasibility study

This research study aims to find out whether it is feasible to measure changes in vision and task performance in patients who have had eye alignment surgery for psychosocial reasons.

Overview of the research

The NHS currently funds eye alignment surgery for strabismus because of the known visual and/or psychosocial benefits to patients. However, more evidence is needed about the outcomes of eye alignment surgery in adults. Some areas in England have withdrawn funding for eye alignment surgery for psychosocial reasons over concern not enough patient benefit is proven. However, evidence suggests that there are aspects of patients lives and their vision that can improve following eye alignment surgery for a planned psychosocial benefit.

This research study aims to find out more information and improve our understanding of the potential outcomes from eye alignment surgery. It aims to answer the questions that have not been addressed by smaller studies.



Having an eye that turns, so that both eyes aren’t lined up in the same direction is known as strabismus. Strabismus is therefore a misalignment of the eyes and is sometimes also called a squint.

Eye alignment surgery (strabismus surgery)

Surgery can be performed on the muscles around the eyes to change the eye position. Eye alignment surgery (or strabismus surgery) aims to restore the alignment of the eyes to a straighter position.

Aims of eye alignment (strabismus) surgery

Some patients undergo eye alignment surgery with the aim of restoring eye alignment and gaining visual benefit from the procedure. Examples of visual benefit include:

  • Getting rid of or improving symptoms of double vision (also known as diplopia)
  • Restoring the use of the two eyes working together as a pair (also known as binocular single vision)

Some patients may not be expected or predicted to gain visual benefit from changing the alignment of their eyes, but eye alignment surgery may still be performed. In this group of patients, the aim is to restore eye alignment, which typically leads to psychosocial benefits and improved quality of life for the patient. Examples of psychosocial benefits include:

  • Suffering less with anxiety and depression
  • Feeling more confident in social situations
  • Improved self-esteem and self-confidence
  • Improved relationships with other people
  • Improved ability to get a job

Funding and supervision

The research is currently being funded by the NIHR. Gemma Arblaster has been awarded a Clinical Doctoral Research Fellowship to undertake this research at the Academic Unit of Ophthalmology and Orthoptics. The research began in June 2017.


Contact details:

Academic supervisors:

Clinical Supervisors:

Advisory group:

Lay patient representatives - we currently have one patient representative on the advisory group and have space to welcome one more. If you wish to discuss this role, please contact Gemma Arblaster.

Additional information

Plain English summary of the research

Having an eye that turns, so that both eyes aren’t lined up in the same direction, is known as strabismus (or squint). This disorder affects 4-5% of the population. Patients with strabismus may have visual problems, such as double vision, but for many it is the misalignment of their eyes that is their main concern. Having misaligned eyes is associated with anxiety and depression, it can reduce a person's self-esteem and self confidence, causing problems with their relationships with other people and reduces their ability to get a job. For the majority of patients with strabismus the main reason for having surgery is to restore the alignment of their eyes to a straighter position. This is called a ‘psychosocial benefit’ and can improve their quality of life. If a patient were to suffer less with anxiety and depression and feel more confident in social situations as a result of eye alignment surgery, this would be an example of ‘psychosocial benefit’. Therefore the NHS currently funds eye alignment surgery because of these known benefits to patients; however NHS services in some regions have withdrawn funding for this surgery over concerns that there is not enough evidence of the benefit to patients.

Approximately £8.4million is spent on adult eye alignment surgery per year in England. It is not fully understood whether eye alignment surgery causes additional benefits above and beyond the psychological and social benefits. Evidence from the literature suggests that there are aspects of patients’ lives and their vision that can improve following eye alignment surgery. But, the evidence comes from small studies that often only describe one aspect of vision. In order to better understand and measure the effects of eye alignment surgery, this study will firstly determine if it is achievable to measure changes in vision and the ability to perform everyday tasks after eye alignment surgery. The study aims to increase our knowledge and understanding of the potential benefits of alignment surgery, and answer the questions that haven’t been addressed in smaller studies.

Patients with strabismus and patients who had recently undergone eye alignment surgery were involved with the development of this research proposal in two focus groups. Their involvement has highlighted that information about possible changes in vision and ability to perform daily tasks after surgery is of high importance to patients deciding whether to undergo eye alignment surgery or not. Participants in the patient focus group will be invited to continue their involvement as part of an advisory group to ensure the study remains focused on what is important to patients.

In the first part of the study, patients who have had eye alignment surgery will be asked their views on what has changed for them following surgery. This study will uniquely focus on their experiences of changes in vision or other useful aspects of everyday living, such as task performance. The results from the first part will inform the second part of the study. In the second part, patients who have chosen to undergo eye alignment surgery will be recruited to have measurements of their vision and task performance before and after surgery. These results will be compared to a group with strabismus but not having surgery to determine whether it is feasible to measure changes in visual function and task performance after surgery. The results from this study will firstly decide whether it is feasible to measure changes in vision and task performance in patients who have had eye alignment surgery for psychological and/or social reasons. Secondly, the results will determine if the tests of vision and task performance are acceptable for patients, and whether the range of tests can be narrowed down to the best at measuring any benefits. Thirdly, the feasibility of the study design will also be determined, specifically is it practical to recruit patients to a study that measures these outcomes before and after eye alignment surgery? This will provide important additional information for decision makers within local NHS services, patients and clinicians about the benefits that patients can gain from eye alignment surgery. In particular it will answer the initial question ‘can additional functional benefits in vision and everyday task performance be measured?’ These results will be used to plan a larger trial comparing different groups of patients with strabismus. This larger trial will measure the additional visual and task performance benefits gained by different groups of strabismus patients following eye alignment surgery, and how these benefits fit with the improvements to their quality of life.

Key research milestones

Update 4 - December 2019

Download updateUpdate 3 - May 2019

Download update

Update 2 - January 2019

Download updateUpdate 1 - May 2018

Download update

Information and transparency

EU General Data Protection Regulations (GDPR) came into effect on 25th May 2018.

Any information collected during this research is anonymised as soon as possible. This means participants are given a study number and are not referred to by any personal information. All data collected is kept confidential and secure, it can only be looked at by the research team directly involved with the study.

Personal contact details are only kept by the research team when participants chose to receive study update newsletters about the research.

Sheffield Teaching Hospitals NHS Foundation Trust are the sponsor of this study. If you would like to contact the sponsor directly you can contact: Dr Dipak Patel, Clinical Research Office, Sheffield Teaching Hospitals NHS Foundation Trust

Gemma Arblaster is registered at the University of Sheffield and study documents are kept on a secure computer system at the university. The University of Sheffield will act as the data controller for this study. This means the University is responsible for looking after any information relating to the study and using it properly. In order to collect and use personal information as part of this research project, we must have a legal basis to do so. The basis that we are using is that the research is ‘a task in the public interest’.

Further information, including detail about how and why the University processes your personal information, how we keep your information secure, and your legal rights (including how to complain in you feel that your personal information has not been handled correctly), can be found in the University’s Privacy Notice

Information collected during this study will be stored securely at the University of Sheffield and destroyed 5 years after the study has ended (expected end date May 2020).

If you have further questions about the study or your information, you can contact Gemma Arblaster directly. 0114 2159034

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