Currently, most clinicians feel they need to document signs of progression to establish a firm glaucoma diagnosis. But a Swedish study may debunk that mindset. An accurate glaucoma diagnosis can be established in just two initial visits when it is based on visual field testing that uses strict criteria for interpretation. Findings that are considered borderline can be backed up with structural findings if visual fields are considered borderline.
Researchers investigated whether patients could be correctly diagnosed with glaucoma during two initial visits, or if signs of progression or disease activity are necessary for a reasonably specific diagnosis. They used data from the Early Manifest Glaucoma Trial (EMGT), where the majority of patients were previously undiagnosed early to moderate glaucoma and identified through population screening.
Definite field progression was defined as at least three identical points in the 30-2 or 24-2 test point patterns showing significant deterioration in glaucoma change probability maps in three consecutive tests. Tentative progression was defined as at least three identical points showing significant deterioration in glaucoma change probability maps in two consecutive tests. Of the trial’s patients, 117 were followed for at least 15 years, representing 147 eyes eligible for the study. The study’s long prospective follow-up provided researchers to determine whether the initial glaucoma diagnoses made without follow-up and proof of progression were reliable or incorrect.
At least one of the following criteria had to be fulfilled during follow-up to confirm the initial diagnosis: (1) visual field progression in at least one eye according to the EMGT criterion; (2) development of manifest glaucoma in an initially ineligible fellow eye; (3) optic disc progression in at least one eye; (4) optic disc hemorrhages in at least one eye.
During follow-up, 134 eyes (91%) showed visual field progression, and, of the remaining 13 eyes, only four (3%) did not fulfill any of the criteria to confirm the diagnosis. The patients did display other signs of glaucoma—progression of glaucomatous field defects or incident glaucoma in the fellow eye, occurrence of optic disc hemorrhages or documented optic disc progression.
The study concluded that there is little risk of making a false-positive diagnosis when practitioner bases it on visual field testing results with strict interpretation criteria as used in the EMGT.
|Öhnell HM, Bengtsson B, Heijl A. Making a correct diagnosis of glaucoma: data from the EMGT. Glaucoma. September 18, 2019. [Epub ahead of print].|