Over-diagnosed glaucoma:possible consequences for patients and health care services

Dear editor,

Recent epidemiological studies have reported that a large percentage of glaucoma patients remain undiagnosed and thus are at serious risk of progressive vision loss¹. The need to minimize this percentage leads to efforts to detect risk factors associated with glaucoma¹. Early detection requires clinical examinations on specific high-risk target groups, since mass screening examinations for the detection of glaucoma in the general population may not be cost-effective².

Although such measures to enhance early glaucoma diagnosis are undoubtedly the primary objective, the overall management of glaucoma may also be examined from a different perspective. By working in a tertiary glaucoma reference centre, we occasionally examine patients who have been previously erroneously diagnosed with open-angle glaucoma. A retrospective assessment of these patients' charts from 2005 to 2008 has revealed that out of 108 referrals (41 males, 37.96%) for tertiary glaucoma management, 16 (14.81%) did not strictly meet the criteria for glaucoma diagnosis³. All 16 patients (7 males, 43.75%) had previously been diagnosed with glaucoma by qualified ophthalmologists and had been given anti-glaucomatous medications. Glaucoma diagnosis had been widely based on the detection of "elevated" intraocular pressure (IOP) readings in one or both eyes, in some cases about 30-35mmhg, as well as "suspicious" appearance of the optic disk (including occasionally borderline peri-papillary nerve thickness measurements). The usual lack of findings on the visual fields had been attributed to the common knowledge that the visual fields become altered later on, along the course of the disease. Interestingly, in most of these patients, corneal pachymetry as well as gonioscopy had been performed and had been taken into consideration by the referring ophthalmologist. We therefore believe that glaucoma over-diagnosis in these patients did not reflect in any unrecognised presence of ocular hypertension or attacks of angle closure. We believe that in many cases, an elevated IOP reading may be attributed to neuro-psychological effects, as previously described⁴. However, once a diagnosis of glaucoma has been made it may be challenging for subsequent examining doctors to question its validity and take responsibility for discontinuing medications. Hence, a vicious circle of re-examinations and concern begins and it is difficult to break.

The situation may be further complicated by the liberal use of antiglaucomatous medications which add a substantial economic burden to patients and health care systems. This can also cause significant ocular surface morbidity and can compromise the success of any medical or surgical anti-glaucomatous treatment that may actually be required in the future. We therefore believe that both ophthalmologists and primary care physicians, through an active collaboration, should be more aware of the perils of glaucoma over-diagnosis, as well as the risk of missing undiagnosed glaucoma cases.

Conflict of Interest: None to declare