¡¡¡¡2¡¡Results

¡¡¡¡2.1¡¡The averaged results for some of the variables measured or recorded are shown in Table 1. These data give useful values for the expected ranges of a wide range of parameters for a southern Chinese population.A number of these values may change with age and refractive error, however, and these factors must be taken into account when the values are considered.

¡¡¡¡2.2 Correlations

¡¡¡¡It is known that ocular dimensions vary with age, gender and refractive error£Û7£¬8£¬9£Ý.To obtain meaningful correlations from our date, we used partial correlations and controlled for the effects of age, refractive error and gender in our data set.Intraocular pressure was correlated weakly with corneal radius, anterior chamber depth and pupil size in the dark.

¡¡¡¡Table 1¡¡The averaged findings of the parameters examined

¡¡¡¡(ACD=anterior chamber depth;IOP£½intraocular pressure.)

¡¡¡¡Table 2¡¡Partial correlations between measured variable

¡¡¡¡*P£¼0.05£¬**P£¼0.01

¡¡¡¡When controlled only for gender and refractive error,anterior chamber depth was well correlated with age(r=-0.60,P£¼0.001),as might be expected since the crystalline lens continues to grow throughout life and corneal curvature reaches adult levels early in life£Û10£Ý.

¡¡¡¡The van Herick findings for nasal and temporal regions correlate well(Spearman Rank correlation:rs=0.79,P£¼0.01),but this high correlation is due in part to the fact that the same observer made all measurements and that only four classification categories were used.The gonioscopic findings for nasal and temporal regions also correlate well(rs=0.89,P£¼0.01).

¡¡¡¡How well do the van Herick ratios and gonioscopic findings

¡¡¡¡agree?The correlation between the van Herick and gonioscopic results for the nasal region was 0.53(P£¼0.01)and for the temporal region was 0.50(P£¼0.01).The cross-tabulations show that the van Herick method was more likely to indicate that the anterior angle was wider than the gonioscopic finding(Table 3).If gonioscopy is taken as the "gold standard",then the van Herick method over-estimates the relative width of the anterior angle.

¡¡¡¡Is the anterior chamber depth related in some way to the van Herick and gonioscopic findings?Our analyses suggest not. When controlled for age,gender and refractive error,the anterior chamber depth was not significantly different for the various van Herick grades at the nasal (F=1.61;df=3,65;P=0.19) or temporal regions(F=0.89;df=3,65;P=0.45).Anterior chamber depth was also not different for the various gonioscopic grades(temporal region:F=1.27;df=2,58;P=0.28;nasal region F=0.75;df=3,57;P=0.52).

¡¡¡¡Table 3¡¡Gonioscopy and van Herick gradings

¡¡¡¡We found no differences between males and females in IOP, anterior chamber depth, van Herick ratios and gonioscopic findings for the nasal and temporal regions when age and refractive error were held constant.

¡¡¡¡3¡¡Discussion

¡¡¡¡We found the mean anterior chamber depth to be 2.85mm for our subjects. Moreno-Montanes et al. reported mean anterior chamber depths of 3.01mm for women and 3.10mm for men(mean age of their sample:52.7 years£¬SD:20.3 years.)£Û11£Ý.Since the age distribution of our subjects was similar to that of Moreno-Montanes et al.(Welch's approximate t=0.449,P=0.65),we can infer that our subjects had a shallower anterior chamber depth.

¡¡¡¡Our results show that anterior chamber depth decreases significantly with age,even when partial correlation analysis is used,with controls for refractive error and gender. This agrees with previous findings in caucasian populations£Û11£¬12£Ý.This finding is significant becasue a narrow anterior chamber is a recognised risk factor in primary closed angle glaucoma£Û13,14£Ý.

¡¡¡¡The van Herick technique is widely used in clinical practice for assessing the width of the anterior angle. It is often used to indicate whether gonioscopic examination is needed.van Herick,Shaffer and Schwartz£Û1£Ý intended that the technique be used to alert the clinician to the possibility of angle closure in the narrow-angle group,and help avoid gonioscopic misinterpretations.They also reported close agreement between the anterior chamber angle width estimated by gonioscopy and with the slitlamp method, but they did not present data to support their observation.We found significant correlations between angle widths estimated by the van Herick method and gonioscopy(rs=0.53¡¡and¡¡rs=0.50 for the nasal and temporal regions respectively).However,these correlations account for only 28% and 25% of the variance associated with these measures, and thus other factors must enter into these assessments.van herick,Shaffer and Schwartz reported that in a few cases, the slitlamp method gave a greater width than that observed with gonioscopy£Û1£Ý.We found that the van Herick method was more likely to indicate that the anterior angle was wider than the gonioscopic finding(Table 3).If gonioscopy is taken as the "gold standard",then the van Herick method over-estimates the relative width of the anterior angle. Clinicians should be aware that the van Herick findings are more likely to suggest a wider anterior chamber angle than does gonioscopy. thus, if clinicians are in any doubt about their van Herick findings, they should perform gonioscopy.

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