Guidance

Diabetic eye screening: guidance on fundus image quality and when adequate images cannot be taken

Updated 11 March 2026

Applies to England

This NHS Diabetic Eye Screening (DES) Programme document provides guidance in the following situations: 

• when images cannot be taken 
• when determining the quality of images
• when images can be taken but are inadequate
• actions for staff if images are inadequate

This guidance only covers digital fundus images and does not apply to optical coherence tomography (OCT) imaging.

1. When images cannot be taken

If a screener is unable to capture images at screening, they must record the event in the software, noting the reason for the inability to capture images.

This may be due to technical, medical, or physical reasons. Or the individual did not consent.

1.1 Technical failure

In the event of an IT failure or technical reason, the software will automatically update the individual’s record as an incomplete encounter, and the individual will be reinvited for screening.

An invitation for the individual being screened will be automatically sent to the administration queue and they will need to be re-invited for screening by the local DES service.

An appropriate letter should automatically be issued to the individual and their GP.

Unreliable equipment should be reported and managed as per the local policy. 

1.2 Medical/physical reasons

If an individual is unable to have images taken due to physical or medical reasons, DES services should follow the medical opt out process in the cohort management guidance or refer to the slit lamp pathway if appropriate.

2. When images can be taken 

During a screening encounter, the images obtained for each eye are collectively referred to as an ‘image-set.’ Each image-set must be assessed for overall quality.

2.1 Definition of adequate image-set quality

The definition of adequate image-set quality includes: 

• for Routine Digital Screening, 2 nominal 45-degree fields (one fovea centred and one disc centred), or for Digital Surveillance, the area of retina to be imaged 
• a combined assessment of field position and visualisation of the retina/macula (see section 3 below)

2.2 Deciding on image-set quality at the point of screening 

Deciding on image-set quality at the point of capture is within the competencies of a screener and covered in the health screening qualification. 

A screener must decide the quality of an image-set at the point of image capture. In cases where an image-set is deemed to be inadequate, the screener should attempt, if appropriate, to: 

• ensure individual is positioned correctly
• capture extra images including a far temporal view and attempt to photograph around any opacity (jig-sawing)
• take anterior segment views to show any opacity or obscuration and the reason for the inadequate images
• use the small pupil setting where appropriate 
• ensure that the local DES service dilation protocol is complied with

The screener should record in the software if each image-set captured during the screening encounter is of adequate or inadequate quality.

2.3 Deciding on image-set quality at the point of grading 

All grading must be performed by qualified grading staff.

When grading an image-set, the grader should record whether the quality is adequate or inadequate. Image-sets should only be marked as adequate if the grader is confident the quality is sufficient.

All visible diabetic retinopathy (DR) features must be recorded on the features-based grading (FBG) form within the software.

A decision regarding quality of an image-set can be made at each step of the screening and grading pathway. If the primary/secondary/arbitration Full Disease Grader (FDG) disagrees with the decision of image-set quality taken at the point of screening, they can record a different quality decision. The final grading level will determine each image-set quality outcome for the screening encounter.

All image-sets go to primary disease grading regardless of quality. 

3. Combined assessment of field position and visualisation of the retina/macula

A combined assessment of field position and visualisation of the retina/macula is described below. 

Adequate: 

• macular image(s): the centre of fovea is > 2DD from edge of image and the 3rd generation vessels are visible within the macula
• disc image(s): the complete optic disc is > 2DD from edge of image and the fine vessels are visible on surface of disc

Follow the standard grading pathway for adequate image-sets.

Inadequate:

• failure to meet definition of adequate as described above. 
• for inadequate image-sets, any features ticked on the FBG form will be recorded in the software
• for R0, R1 or R3S features, the software will produce a U grade, and the individual will follow the specified pathway for inadequate image-sets
• for M1, R2L/H or R3A features, the software will produce the associated referral grade, and the individual will follow the specified pathway for referrable image-sets
• the final grading stage for these situations is Referral Outcome Grade (ROG)

4. Actions for referral outcome graders  

The referral outcome grader (ROG) should determine the screening outcome based on the single common pathway for DES and using the screener’s notes to support decision-making. Outcomes can be: 

• issue another appointment for repeat imaging
• refer to slit lamp biomicroscopy (SLB) 
• refer to hospital eye service (HES) 
• exclude one eye if unable to obtain images in that eye
• exclude from screening if the individual is considered unsuitable for further screening or treatment 

The DES Cohort management guidance should be used if an individual is to be excluded from screening. Not all ROG graders are able to make a decision to exclude from screening.

The local service should issue the appropriate letter to the individual and their GP once the action has been determined.