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Anatomic endoscopy of the ciliary body, part 2
Knowing the retroiridal anatomy can help prevent iatrogenic intraocular trauma.
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All instruments used in intraocular surgery, whether of the anterior or posterior segment, come into proximity with the ciliary crown and the anatomy surrounding the ciliary body. Whenever an instrument passes the edge of the pupil and penetrates into the retroiridal space of the posterior chamber, it disappears and evades direct visual control from the operating microscope.
One has only to imagine the multitude of micro-traumas that the related tissues suffer — the capsular planes, the pigmented part of the posterior iris, the iridociliary angle, the equator of the capsular bag, the ciliary body — especially since the structures are close and distances for our precise therapeutic actions are on the order of microns.
It is therefore absolutely essential to know well all the parameters of the area concerned before venturing into surgery.
All directions
The relationships of the ciliary body to surrounding structures are important to know:
---Endoscopic side view of the ciliary body from the anterior chamber. Pre-iridal (anterior chamber) and retroiridal (posterior chamber) spaces can be seen with the intermediary pupillary edge. We can easily identify the posterior iris, the endoscopic tightrope line and many details of the processes (atrophic appearance, congestive capillaries).
Anteriorly. The posterior side of the iris faces the anterior side of the ciliary process. The ciliary epithelium is in constant contact with the aqueous humor of the posterior chamber. The precise nature of contacts with the pigmented epithelium depends on the width and the depth of the iridociliary angle. Between the two epitheliums, ciliary and iridal, there are times of proximity and even of direct contact.
Peripherally. The stroma of the ciliary body lies peripherally — the true basis of the ciliary crown. It is never visible. It is masked by a double layer of ciliary epithelium.
Centrally. The equator of the lens and the circumlenticulary unit are several hundred microns distant from the head of the process under normal conditions. After the extraction of the contents of the crystalline bag, this distance is reduced to almost nothing. This is even truer after implantation of an IOL in the bag. Contact is made between the crystalline lens equator and the ciliary process, between the biomaterial and the uveal structures concerned. We can differentiate direct uveal contact (in the case of a haptic outside the capsular bag) from indirect uveal contact (with the equator of the capsular bag interposed). An endoscopic report of this occurrence is essential, attesting to tissue trauma even though the haptic is in the bag.
---Endoscopic side view of the ciliary body from the posterior chamber. From front to back: posterior iris, zonular structures, lens equator facing the top of the ciliary body, eight ciliary processes with peanut-like appearance, pars plana, ora serrata and the extreme periphery of the retina.
Posteriorly. The retro-coronary zonules, the anterior hyaloid membrane and the pre-basal peripheral vitreous have a constant relationship, a narrow superimposition of different structures, from outside and inside: epithelium of the process in two layers, zonular attachments in two layers, the anterior hyaloid membrane and the pre-basal vitreous. Certain areas can be distinguished endoscopically by their degree of pigmentation (epithelium to pigmented cells of the process), or by their degree of refraction at the insertion zones (Salzmann’s ligament).
The vascular network of the processes is usually visible by endoscopy. The epithelial layer of nonpigmented cells allows good transmission of light. The difficulty is in the second, underlying pigmented layer, with important melanin content. This double epithelial layer is a good barrier for the transmission of fluorescein, except in the case of the blood aqueous barrier.
In performing fluorescein angiography of the ciliary body under endoscopy, it is important to take the views carefully in order to avoid, because of the massive diffusion of dye, obscuring certain interesting details.
Under endoscopy, the capillaries are easily distinguished, especially in the tip and the posterior aspect of the process. Very often two capillary networks cover the area of the processes. Sinuous and of irregular diameter, the capillaries disappear before the corona ciliaris. This corresponds to their deepest point of passage at the base of the process, in front of the circulatory system, near the vertical drains. Dilated and easily visible or exsanguine and less distinguishable, the ciliary capillaries are always perceived. All the better since usually there is epithelial atrophy. Whitish rows from which the vessels are visible prove this.
Conclusion
---Anatomic elements seen in an endoscopic retroiridal view include both fixed elements — the papillary edge, posterior iris, sulcus, ciliary body and pars plana — and mobile elements — anterior and posterior lens capsules, anterior, equatorial and posterior zonular network.
Since it is responsible for the secretion of aqueous humor, the ciliary body deserves a retro-iridal tour using endoscopy. Endoscopic approaches that are both diagnostic (cycloangiography) and therapeutic (cyclophotocoagulation) have been described.
In future installments of The Endo-Scoop, these perspectives on the ciliary body will be linked to two other points of focus: its connection to the uvea and inflammation, and the diversity and quality of its relationship with its surrounding structures (the capsular bag, vitreous body and retina).
The Drs. Leon would like to thank the scientific endoscopic collaborators for their help with this endoscopic article: Daniele S. Aron-Rosa, MD, PhD (France); Yale L. Fisher, MD (USA); Karen M. Joos, MD PhD (USA); Frank H. Koch, MD (Germany); and Bruce M Massaro, MD (USA).
For Your Information:
- Claude S. Leon, MD is president of the International Society of Ophthalmic Endoscopy Inc. in New York. He can be reached at Ocular Endoscopic Department, Ave. George Pompidou, Porto-Vecchio 20137, France; (33) 495-706-300; fax: (33) 495-706-293; e-mail: endo.leon@wanadoo.fr; Web site: perso.wanadoo.fr/endoscopy.leon/.
- Joseph A. Leon, MD, under a European laser certification, is working in all ophthalmic applications of laser-endoscopy; e-mail: Leon.joseph.opht.endoscop@wanadoo.fr.