The role of the peripheral retina in diabetic retinopathy
: from basic science to town planning

Student thesis: Doctoral ThesisDoctor of Philosophy


Diabetes is a serious long-term condition which can cause many complications including diabetic retinopathy and diabetic maculopathy. These collectively not only affect the central vision, but often cause peripheral vision problems. Retinitis pigmentosa is an inherited retinal condition which also causes mid-far peripheral loss of vision as well as central loss at the later stages of the disease.

For those with diabetes, reduced quality of life is often related to loss of vision. For many losing sight is accompanied by multiple other complications including kidney disease. With loss of vision, daily tasks can become challenging and cause an inability to perform certain tasks leading to socio-economic disadvantages.

One of the biggest barriers for people with a loss of vision is navigating towns and cities. Built environments are often described as ‘not fit for purpose’ and ‘hostile’ by people with a visual impairment as they are created for the average human being as opposed to all who use them. Due to towns and cities serving as a platform for daily life and tasks, once they become inaccessible for any reason, such as a street clutter, noise, light and shared space, a barrier is created. Often these barriers prevent people going out due to embarrassment, frustration and loss of confidence. This often causes isolation and loneliness, creating further mental and physical issues.

Research Questions
•Does vision loss and function due to diabetes and retinitis pigmentosa affect independent mobility and navigation in urban environments?
1.To assess stakeholder opinions on navigating the built environment with a visual impairment
2.To develop a street audit tool which can be used to assess any barriers and enablers of the built environment in a global context
3.To assess the level of vision and retinal pathology in people with diabetes and retinitis pigmentosa using sophisticated imaging
4.To assess visual function in people with diabetes and retinitis pigmentosa through visual function testing
5.To assess quality of life and diabetes distress through the use of pre-validated questionnaires
6.To assess user experience through walkarounds of a set area
7.To correlate results from grading, visual function and walkarounds to assess how vision impacts on navigation of the built environment

Firstly, stakeholders including visually impaired people, architects, planners, charities and ophthalmic professionals were interviewed about their views on people with a visual impairment navigating the built environment, any potential barriers and any solutions to make navigation easier.
Secondly, participants with varying levels of diabetic retinopathy and retinitis pigmentosa were recruited into the study to complete visual function testing, retinal imaging, questionnaires and a walkaround of a set area.
Participants attended for a walkaround of an area near Queen’s University Belfast where they discussed any issues they faced when navigating through the streetscape. Questions on levels of confidence, anxiety and difficulty were asked at different points around the 1-mile walk.
Participants were then invited to the Northern Ireland Clinical Research Facility (NICRF) or Optos Wide-Field retinal imaging, Heidelberg OCT, OCTA and multicolour images. They also completed AdaptDx dark adaptation, visual acuity, contrast sensitivity and Metrovision Visual Fields. Quality of life (RetDQol), diabetes distress (DDS17) and a study questionnaire were also completed.

Stakeholder interview results showed that stakeholders agree that there can be barriers to navigating towns and cities for people with a visual impairment. Despite these issues, stakeholders made suggestions which could improve planners/architect knowledge and awareness while also improving the streetscape and making it more accessible for all. One of the recommendations for planners and architects was further specialised education into navigating with a visual impairment. In addition, more robust guidance and policies were suggested to create confluent accessible environments throughout the region.
When retinal images were graded for pathology, those with treated diabetic retinopathy and retinitis pigmentosa seemed to have a similar percentage of the retina affected. Despite this, those with treated diabetic retinopathy did not seem to have issues with visual acuity but did have visual field, contrast sensitivity and dark adaptation issues.
Of all participants, 43.8% reported confidence/anxiety issues and difficulty when navigating. Some of the most common issues discussed were bollards, shop signs, advertisement boards, uneven pavements, parked cars and colour contrast. While 80% of those with RP faced problems walking around the set area, only 5 (22.7%) people with diabetic eye disease (DED) (both treated and untreated) reported similar issues.

Conclusions and recommendations
Despite similar issues with visual function people with DED did not have the same issues navigating the built environment. This could be due to DED pathology being less absolute or confluent.
Small changes could be made to make built environment professionals more aware of the barriers faced by people with a visual impairment. In addition, more robust guidance and policy should be introduced to allow for a regional approach to accessible areas for all.
Date of AwardJul 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsQueen's University Belfast & Optos plc
SupervisorNeil Galway (Supervisor), Tunde Peto (Supervisor) & Gregory Hageman (Supervisor)


  • Town planning
  • visual impairment
  • diabetic retinopathy
  • retinitis pigmentosa
  • navigation
  • sight loss
  • diabetes

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