BLOG: Learning more about crystalline lens anatomy
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It is well known that the crystalline lens anatomy changes with age. However, some of its anatomical features have not previously been well characterized due to the difficulty of imaging and measuring lenses in vivo.
In a recently published paper, my colleagues and I used the intraoperative spectral-domain OCT integrated into the Catalys femtosecond laser (Johnson & Johnson Vision) to measure lens thickness, diameter and volume in 470 eyes undergoing cataract or refractive lens surgery.
As measured by this device, lens thickness (LT) is the distance between the anterior and posterior lens capsules; lens diameter (LD) is the distance between the intersections of the anterior and posterior lens surfaces; and lens volume (LV) is calculated from the measured anterior and posterior lenticular surface curvatures that were extended to intersect in the lenticular periphery.
We found significant natural variations in lens anatomy in our patient population (Table). The mean age was 68.2 years, and most patients were older than 55 years, so the results cannot necessarily be generalized to younger people, although we would expect similarly wide variation at any age.
Table. Lens anatomy parameters in eyes undergoing lens surgery
|
Parameter |
Minimum |
Maximum |
Mean |
|
Lens thickness (LT) |
3.6 mm |
5.7 mm |
4.7 mm |
|
Lens diameter (LD) |
7.5 mm |
11.9 mm |
10.7 mm |
|
Lens volume (LV) |
119.9 mm3 |
312.4 mm3 |
230.4 mm3 |
LV is particularly interesting because there really is no comparable normative data on LV in the literature. In our study, LV was moderately correlated with age (r = 0.573; P < .001) and strongly correlated with LT (r = 0.785; P < .001) and LD (r = 0.696; P < .001). There was a weak inverse correlation between LV and anterior chamber depth (ACD) (r = –0.317, P < .001) and no correlation between LV and axial length (AL) (r = 0.084).
Multiple linear regression analysis demonstrated that conventional biometry measurements are poor predictors of LD and LV. ACD and LT can explain only about 70% of the variance in LV, for example. Age, AL and ACD can explain only about 22% of the variance in LD. This suggests that a robust understanding of lens anatomy parameters requires precise intraoperative measurements.
More accurate quantification of lens anatomy and position using intraoperative SD-OCT could be useful for improving the accuracy of effective lens position estimation and IOL power calculation formulas, surgical decision-making and new IOL designs.
In a future blog post, I’ll discuss the implications of this study for surgical decision-making in eyes of varying axial lengths.
Reference:
- Waring GO 4th, et al. Am J Ophthalmol. 2021;doi:10.1016/j.ajo.2020.12.021.
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