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Importance of Structural Examination Methods in the Follow-up of Patients with Ocular Hypertension

Purpose:
To evaluate the contribution of Heidelberg Retina Tomograph (HRT) and blue-on-yellow perimetry (B-Y) for the follow-up and early diagnosis of glaucoma in patients with ocular hypertension (OHT). We also dealed with the comparison of visual field (VF) examination by means of the B-Y and white-onwhite perimetry, correlation between VF indexes and HRT parameters, importance of the central corneal thickness (CCT) and the comparison of other characteristics of the study and control groups during the 3-year-study-period.

Patients and methods:
Both eyes of 28 patients with OHT (study group, SG) and 15 control subjects (control group, CG) were included in the study. Subjects in both groups were examined annually. At each visit complete ophthalmological examination was carried out, including the biomicroscopic evaluation of the optic disc, aplanation tonometry, HRT II analysis of the optic nerve head (ONH) and B-Y perimetry. Pachymetry was performed only once at the beginning of the study.

Results:
During the 3-year-follow-up structural changes of the ONH developed in 2 patients with OHT only. They were not accompanied by VF defects on B-Y perimetry. Intraocular pressure and CCT were higher in the SG (p<0.01). CCT significantly and positively correlated with the level of intraocular pressure in both groups. Mean sensitivity (MS) of the B-Y VF was repeatedly smaller in the SG compared to the CG (p<0.01). Difference between MS a mean defect (MD) of the B-Y and white-on-white VF in the SG was significant (p<0.01). The B-Y perimetry test lasted much longer than standard perimetry. A marked learning effect was found with B-Y perimetry. Despite significant correlations of follow-up B-Y perimetry examinations, high test-retest variability was found. No significant change in topographic parameters of the ONH occurred during the followup period. HRT displayed low variability of follow-up examinations. No significant correlation between topographic parameters of the ONH and VF indexes on B-Y perimetry was found.

Conclusion:
In 2 cases of OHT the HRT preceded VF changes on B-Y perimetry. HRT showed high reproducibility, on the contrary, B-Y perimetry was accompanied by high variability making the distinction of fluctuation and progression more difficult. Pachymetry is a very useful tool in patients with OHT.

Key words:
ocular hypertension, Heidelberg retina tomograph, perimetry, pachymetry