Retinal nerve fiber layer thickness and retinal vascular caliber alterations in coal miners in northern China: a community-based observational study

AIM: To evaluate retinal nerve fiber layer thickness and retinal vascular caliber alterations in coal mine workers. METHODS: The community-based observational cross-sectional study included 4004 participants of a sub-population of the Kailuan Study. All the study participants underwent structured interviews with a standardized questionnaire, fundus photography and spectral-domain optical coherence tomography (OCT) examinations performed by trained doctors. RESULTS: The retinal nerve fiber layer thickness was significantly higher (P=0.006) and the central macular thickness was lower in coal miners (n=659, 51.0±7.8y) as compared to the control (working above the ground; n=477, 51.8±7.5y; P=0.032). Additionally, the downhole workers showed a significantly thicker retinal artery (P=0.012) and vein diameters (P<0.001). In multivariable regression, a thicker retinal nerve fiber layer was associated with a higher cumulative silica dust exposure (P=0.005) after adjusting for younger age and larger spherical equivalent. In a reverse pattern, a higher cumulative silica dust exposure (P=0.004) was significantly associated with a thicker retinal nerve fiber layer after adjusting for age, high-density lipoproteins and uric acid. Wider retinal vein diameters were associated with higher cumulative silica dust exposure (P=0.036) after adjusting for younger age and larger spherical equivalent. CONCLUSION: The retinal vessels diameters and retinal nerve fiber layer thickness are significantly thicker in long term of coal mining. The results of our study indicate that underground working environment may lead to retinal vessel dilation and inflammation. Thus, ocular examination might be needed within coal miners in order to monitor the occupational eye health as well as the incidence and progression of eye diseases.

Criteria for the reliability of optical coherence tomography measurements in patients with age-related cataract

Purpose. To determine optimal criteria for reliable optical coherence tomography (OCT) measurements in patients with age-related cataract. Material and methods. We examined 83 patients (83 eyes) with agerelated cataract before and after cataract surgery. The intensity of lens opacity was assessed by the Cirrus HD-OCT signal strength and Pentacambased Scheimpflug images analysis. Clinical cataract grading was performed according to the WHO classification. Preoperative measurement was considered reliable if its' difference with postoperative measurement did not exceed 5 ?m for the peripapillary retinal nerve fiber layer thickness (pRNFL) and 8 ?m for the central subfield thickness. Results. According to the ROC analysis, only the OCT signal strength allows to distinguish reliable OCT measurements: area under the ROC-curve (AUC) of the OCT signal strength was 0.815 (95% confidence interval 0.720–0.909) for the pRNFL and 0.756 (95% CI: 0.632–0.880) for the central subfield thickness. The best signal strength thresholds for reliable data were 5.5 for pRNFL and 4.5 for the central macular thickness (considering that the signal strength is measured in integers, these values should be rounded to 6 and 5 respectively). The rest of the studied parameters had AUC less than 0.6 so they cannot be used for evaluating OCT data. Conclusion. In patients with age-related cataract, only OCT signal strength can determine reliability of the OCT measurements. The lowest signal strength for reliable data on the Cirrus HD-OCT is 6 for pRNFL and 5 for centr al subfield thickness. Key words: optical coherence tomography, cataract, retina, nerve fiber layer, lens densitometry.

Water-drinking Test in Normal Tension Glaucoma Patients with and without High Myopia

This prospective study aims to evaluate the correlation between myopic severity and normal tension glaucoma (NTG) by investigating IOP changes following water-drinking test (WDT). We reviewed 61 patients with NTG during an interval of three years, of which 31 were highly myopic (HM) and 30 were non-highly myopic (NHM). Basic characteristics such as age, gender, spherical equivalence, baseline IOP, visual field parameters, and average retinal nerve fiber layer thickness were compared between NTG patients with and without high myopia. The IOP parameters obtained following WDT were then compared between the HM and NHM NTG groups. Intragroup analysis revealed significant IOP elevation following WDT within the 45-minute duration in both groups. However, no significant differences in IOP parameters were observed between the HM and NHM NTG groups. In conclusion, although the pattern of IOP fluctuations was different, the extent of IOP fluctuations and peak IOP following WDT was similar between the HM and NHM NTG groups, suggesting that myopic severity probably has a limited role in NTG. Lastly, WDT was an effective tool for eliciting IOP peaks when 24-hour IOP monitoring is not available.