Repeatability and reproducibility of applanation resonance tonometry : a cross-sectional study

Background: To assess repeatability (intra-observer variability) and reproducibility (inter-operator variability) of intraocular pressure (IOP) measurements with servo-controlled Bioresonator Applanation Resonance Tonometry (ART) and to evaluate possible influential factors. Methods: The study included 178 patients (115 glaucoma and 63 controls; one eye per subject). IOP was measured once with a Goldmann applanation tonometer (GAT) and twice by ART (ART1, ART2), in randomized sequence, by a single operator to assess intra-operator variability. Each ART measurement consisted on 3 readings. To assess inter-operator variability 2 evaluators performed 2 measurements each (in random order) on the same patient. Repeatability and reproducibility were assessed by the coefficient of variation (CoV) and intraclass correlation coefficient (ICC). Results: In the entire cohort, ART1 was 0.4 \ub1 2.2 mmHg (-7.0 to 5.7 mmHg) higher than ART2 (p = 0.03) regardless of test order. Intra-operator CoV was 7.0% \ub1 6.3%, and ICC was 0.80-0.92. Inter-operator CoV ranged between 5.7% \ub1 6.1% and 8.2% \ub1 7.2%, and ICC between 0.86 and 0.97. ART1 and 2 were respectively 1.7 \ub1 3.1 and 1.3 \ub1 3.1 mmHg higher than GAT (p < 0.01). Test-retest difference with ART fell within \ub11 mmHg in 41% of cases, within \ub12 mmHg in 70%, within \ub13 mmHg in 85%. 15% had a test-retest difference higher than \ub1 3 mmHg; Bland-Altman 95% intervals of confidence were -3.9 and +4.6 mmHg. Results were unaffected by age, diagnosis, central corneal thickness, keratometry, operator, randomization sequence. Conclusions: In most cases ART repeatability and reproducibility were high, with no differences due to patients' characteristics. ART measurements overestimated GAT by a mean of 1.3-1.7 mmHg

In vivo confocal microscopy of conjunctiva in preservative-free timolol 0.1% gel formulation therapy for glaucoma

10noPURPOSE: To evaluate the effects at 1 year of preservative-free timolol gel and preserved timolol eye drops on conjunctiva and tear parameters. METHODS: Forty patients with primary open-angle glaucoma or ocular hypertension were randomized to the two treatment groups and compared with 20 healthy age-matched controls. Clinical tests (IOP, Schirmer I test, and lacrimal film break-up time BUT) and in vivo conjunctival confocal microscopy (IVCM) were performed in all patients at baseline and after 12 months. IVCM (HRT II Rostock Cornea Module; Heidelberg Engineering GmbH, Heidelberg, Germany) was performed after topical anaesthesia in the four cardinal locations and at the corresponding limbus to analyse conjunctiva cells. The main IVCM outcomes were goblet cell density and epithelial regularity. RESULTS: IVCM and clinical parameters were similar in the three groups at baseline. After 12 months, intra-epithelial goblet cell density was significantly lower in the preserved (48.25 ± 7.70) than in the preservative-free beta-blocker group (86.83 ± 22.17, p < 0.001) and controls (88.9 ± 18.33, p < 0.001). The epithelial layer was significantly more regular in the preserved beta-blocker medication group than in the preservative-free beta-blocker group (p < 0.001) and the control group (p < 0.001). A significant reduction in both Schirmer I and BUT was found in the group of preserved timolol (respectively, 11.3 ± 2.97 and 8.12 ± 0.99) compared with preservative-free timolol (16.8 ± 1.83 and 11.27 ± 1.27, p < 0.001) and controls (17.8 ± 1.87 and 12.10 ± 1.28, p < 0.001). CONCLUSIONS: Based on our IVCM data, preservative-free beta-blocker gel induces less changes at ocular surface than preserved beta-blockers, a fact that should be considered to obtain less adverse effects and maximal adherence to treatment in a chronic condition such as glaucoma.reservedmixedFrezzotti P; Fogagnolo P; Haka G; Motolese I; Iester M; Bagaglia SA; Mittica P; Menicacci C; Rossetti L; Motolese EFrezzotti, Paolo; Fogagnolo, P; Haka, G; Motolese, I; Iester, M; Bagaglia, Sa; Mittica, P; Menicacci, C; Rossetti, L; Motolese, Eduard