To determine whether a normal visual field assessment at a referring optometric practice is predictive of a normal visual field assessment at the hospital eye service and therefore whether there is any need to repeat it prior to first hospital visit.
Between 1st January 2018 and 1st December 2018 all patients referred into Loughborough Community Hospital with a suspected diagnosis of glaucoma or ocular hypertension were booked for a visual field assessment prior to their initial new patient outpatient attendance. If the visual field test at the optician was documented as being "normal", "within normal limits", "no abnormality detected", or "OK" on the referral letter then the patient was included in the study population. These patients underwent a visual field assessment with a Humphrey's visual field analyser on a 24-2 SITA standard protocol. The outcome of the visual field test was documented including patient age, reliability indices, Mean Deviation and Pattern Standard Deviation. This data was statistically analysed by one of the authors.
Data on visual fields of 501 consecutive patients, 1002 eyes/visual field assessments were collected. The positive predictive value of a normal visual field at the patients referring optometrist was 97% for the right eye and 98% for the left eye. From all the visual field assessments the rate of a visual field where the glaucoma hemifield test (GHT) was outside normal limits (ONL) was 16% for the right eye and 7% for the left eye. There was very little observed association between the referral diagnosis, the IOP at referral, age of patient or the sex of the patient on the likelihood of having an abnormal visual field.
Our data suggests that, in the presence of a normal visual field assessment at the referring optometry practice, there is very little yield of positive findings when the visual field test is repeated prior to clinical assessment. Visual field tests should instead be targeted at those patients with an abnormal visual field test on referral and those with a clinical indication for the test.