Cluster analysis of computerized visual field and optical coherence tomography–ganglion cell complex defects in high intraocular pressure patients or early stage glaucoma

Abstract

Purpose:

The aim of the study is to evaluate the relationship between functional defects shown by cluster analysis of computerized visual field and anatomic defects from optical coherence tomography–ganglion cell complex examination in ocular hypertension or eyes affected by glaucoma.

Methods:

205 eyes affected by ocular hypertension (intraocular pressure > 22 mmHg) or early stage glaucoma were enrolled. The age of the patients ranged from 26 to 87 years (average: 61.83 ± 1.54 years). Computerized 30° visual field (Octopus G1x Dynamic strategy) and optical coherence tomography–ganglion cell complex (I-Vue Optovue) analyses were performed for each eye selected; 68 eyes were tested and retested from two to seven times for a total of 320 visual fields and 320 optical coherence tomography–ganglion cell complex examinations. The visual field was considered abnormal with a mean defect < –2 and loss variance > 6. The optical coherence tomography–ganglion cell complex was considered abnormal with a significant focal loss volume (p < 5%) and/or a significant thinning of total, superior, or inferior thickness (p < 5%). Four different groups of examinations were created according to the results of visual field and ganglion cell complex: normal visual field and normal ganglion cell complex (group 1), abnormal visual field and abnormal ganglion cell complex (group 2), normal visual field and abnormal ganglion cell complex (group 3), and abnormal visual field and normal ganglion cell complex (group 4). The cluster analysis of visual fields (EyeSuite software Interzeag CH) was performed only in the visual field of group 3, and the correlation between cluster values and topographical changes at optical coherence tomography–ganglion cell complex was analyzed.

Results:

The results of the ganglion cell complex and visual field examinations matched 247 (77.19%) times. In 143 cases, the examinations belonged to group 1, in 104 to group 2, in 23 to group 3, and, finally, in 50 to group 4. The visual field cluster analysis performed on group 3 showed that the correlation between optical coherence tomography–ganglion cell complex and visual field cluster analysis defects was 100% (both the exams altered). In 72% of them, there was also a topographical correspondence between the visual field and optical coherence tomography–ganglion cell complex defects.

Conclusion:

In the early stages of glaucoma, the visual field cluster analysis seems to be useful to detect some focal defects that can be otherwise underestimated when globally considering the visual field. In group 3, where the conventional analysis of visual field was normal while the optical coherence tomography–ganglion cell complex exam was abnormal, the visual field cluster analysis showed a topographical correlation with optical coherence tomography–ganglion cell complex defects in more than 70% of the examinations performed. In addition, the patients with abnormal visual field and normal optical coherence tomography–ganglion cell complex were older than those with normal visual field and abnormal optical coherence tomography–ganglion cell complex (66.44 ± 3.51 vs 57.04 ± 5.96 years, p < 0.001 (0.0002)). These results confirm that the reliability of a visual field examination is subjective and decreases with age because of its difficulty and the personal compliance of the patient toward this examination.