Abstract
PurposeTo investigate the dependence of the ciliary body length (CBL) on the axial length (AL) and to draw conclusions on implications regarding safe pars plana access for intravitreal injections and vitreoretinal surgery.MethodsA total of 200 individuals (mean age 42 years, SD ± 15.4) were enrolled in the study. Objective refraction and AL were obtained. Spherical equivalent (SE) was calculated. Anterior segment optical coherence tomography (ASOCT) was used to image and measure the CBL.ResultsThe mean SE was − 1.64 diopters (SD ± 3.15, range − 14.5 to + 9 diopters) and the mean AL was 24.19 mm (SD ± 1.65, range 19.8–32.2 mm). There was a significant correlation between SE and AL (r2 = 0.62, p < 0.0001). Mean CBL correlated significantly with age (r2 = 0.11, p < 0.0001), AL (r2 = 0.23, p < 0.0001) and SE (r2 = 0.25, p < 0.0001). The mean CBL was 3351 μm (SD ± 459, range 2184–4451 μm). Three separate groups were defined by their AL with a normal AL group (AL 22.5 to 25 mm), a short AL group (AL < 22.5 mm) and a long AL group (AL > 25 mm). The mean CBL in the normal AL group was 3311 μm (SD ± 427), in the short AL group 2936 μm (SD ± 335) and in the long AL group 3715 μm (SD ± 365), and differed significantly (p < 0.0001) when compared.ConclusionFor interventions requiring pars plana access (as an intravitreal injection or vitreoretinal surgery), an incision distance of 3.5–4.0 mm posterior to the limbus is recommended. In our research, however, a difference of 0.77 mm in mean CBL between the group with short AL and the group with long AL is demonstrated, implying that the mean CBL in very short and very long eyes differs significantly. These findings suggest that the AL should be taken into account for pars plana access and that it would be advisable to prefer the shorter or longer recommended distance (3.5 and 4.0 mm, respectively) from the limbus, which correlates with the AL. If AL is > 25 mm, a distance of 4.0 mm from the limbus should be chosen; and if AL is < 22.5 mm, a distance of 3.5 mm seems adequate.Trial registration number and dateNCT00564291, 27 Nov 2007
Highlights
The ciliary body (CB) is located posterior to the iris [1]
Key messages The recommended incision distance of 3.5 – 4.0 mm from the limbus for safe pars plana access is based on the ciliary body length
In very short or long eyes, the ciliary body length should be taken into account when performing intravitreal injections or vitreoretinal surgery
Summary
The ciliary body (CB) is located posterior to the iris [1] It is composed of two parts, the pars plicata and the pars plana. The pars plicata forms the anterior portion and is contiguous to the posterior surface of the iris. It represents approximately one quarter of the whole CB. A distance of 0.5–3.5 mm from the limbus depending on the age is used [4, 5]. For this reason, it is important to have a thorough anatomical understanding of the CB and its extent
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