Principles of ophthalmic surgery

image of Principles of ophthalmic surgery
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A thorough understanding of ocular anatomy and physiology and attention to detail regarding positioning of both patient and surgeon, correct use of magnification, and careful instrument selection are all of vital importance if the best surgical outcome is to be achieved. General principles of ophthalmic surgery are considered in detail in this chapter, such as patient and surgeon positioning, sterile preparation of the eye and adnexa; use of magnification; ophthalmic instrumentation; postoperative care.

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6.1 The placement of coloured suture material within the lacrimal puncta and canaliculi is recommended prior to any procedure close to the medial canthus to help avoid inadvertent damage to these structures, as in this case where the dog is about to undergo surgery to remove a cyst at the medial canthus.
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6.2 Surgeon positioned with their arms resting on a folded towel because the chair does not have an integral arm rest. The surgeon should ensure that both they and the patient are appropriately positioned prior to scrubbing for surgery.
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6.3 Patient positioning for corneal surgery. Note that a vacuum positioning bag has been used to ensure that the cornea is horizontal.
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6.4 Small sharp, blunt-tipped, scissors can be coated with a water-soluble lubricant to trap lashes and periocular hairs during trimming, so that they do not contaminate the conjunctival sac.
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6.5 Dilutions of povidone–iodine solution should be made up fresh from the stock solution. A dilution of 1:10 can be used on soft woven (i.e. non-gauze) lint-free swabs for skin disinfection. A dilution of 1:50 can be used to flush the conjunctival sac (providing there is no corneal rupture), followed by sterile saline.
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6.6 Surgical preparation includes flushing the conjunctival sac with a 1:50 dilution of povidone–iodine solution using a syringe.
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6.7 Headband magnifier for use in ophthalmic surgery. (Courtesy of the University of Wisconsin-Madison, Comparative Ophthalmology Service)
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6.8 Surgical loupes provide higher magnification and have better optics compared with headband magnifiers.
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6.9 An operating microscope is essential for the accurate microsurgical techniques required for corneal and intraocular surgery. Operating microscopes are unlikely to be used by general practitioners as they require extensive training and practice to master.
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6.13 Ophthalmic instruments are best stored in specialized boxes with silicone ‘fingers’ to prevent instrument movement and potential damage. Note that the delicate sharp tips are also enclosed in plastic covers to prevent damage.
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6.14 Eyelid specula: (from the top) Castroviejo and Barraquer.
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6.15 Ophthalmic forceps: (from the top) Von Graefe, St Martins with tying platform and micro rat-toothed. Magnified view of the Von Graefe fixation forceps showing the interdigitating fine teeth used to grasp tissue such as the conjunctiva atraumatically. Colibri forceps, which are used to grasp the cornea only. Cilia forceps: (from the top) Whitfield and Bennett’s.
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6.16 Ophthalmic knives. Beaver handle with No. 64 blade and standard No. 15 Bard–Parker scalpel blade. Magnified views of the tips of restricted depth knives showing two different styles.
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6.17 Ophthalmic scissors: (from the top) straight eyelid scissors with blunt tips suited to undermining tissue during blunt dissection, Stevens tenotomy scissors (Straight), Westcott’s tenotomy scissors and Castroviejo type corneal scissors. Enucleation scissors with acutely angled, curved tips (similarly designed haemostats are also available).
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6.18 Needle holders: (from the top) mini-Gillies for large needles such as those swaged-on to 4/0 (1.5 metric) or larger suture material and Castroviejo type with lock.
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6.19 Design and use of various ophthalmic needles. (Illustrations redrawn after with permission from the publisher). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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6.21 Nettleship lacrimal dilator.
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6.22 Desmarres chalazion clamp, which is used for eyelid stabilization and haemostasis. Chalazion clamp in use during cryoepilation for distichiasis.
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6.23 Jaeger lid plate.
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6.24 Ophthalmic callipers (Castroviejo style).
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6.26 Transparent adherent drape for ophthalmic use, which sticks to the underlying paper drape. Note the placement of fine mosquito forceps at the limbus to aid globe stabilization. Drapes with collecting bags are useful when irrigation is used. Magnified image showing placement of an eyelid speculum with the cut edges of the sticky drape tucked under the speculum to maintain an aseptic surgical site.
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6.27 Swabs for ophthalmic use. For eyelid procedures, woven (i.e. non-gauze), lint-free swabs are ideal. For corneal and conjunctival procedures, cellulose spears are preferred.
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6.28 Stabilization of the eyelid skin can be achieved using the surgeon’s finger. A single smooth incision is recommended and the use of a finger not only protects the globe but allows the surgeon to judge the depth of the incision more easily.
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6.30 ‘Dangle’ technique used to pick up delicate ophthalmic suture needles. Tying forceps should grasp the suture material 1–2 cm from the needle, which is dangled and gently brought to rest on the drape. Needle holders can then be used to grasp the delicate needle in the correct position (i.e. one-third to one-half of the distance between the swaged end and the needle point).
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6.31 Accurate placement of sutures is best achieved by gently rolling the wrist and allowing the needle to find its own path, rather than trying to push it through the tissue. The needle should always be regrasped with needle holders (never with forceps as this may result in damage).
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6.32 Minimal tissue trauma and maximal wound alignment are achieved by directing the needle along a curvilinear path. This is achieved in a number of steps. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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6.33 Simple interrupted suture pattern. The rule of bisection should be used to close entropion incisions where the two incisions are of unequal length. In this example, the order of suture placement would be A – B – C – D. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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6.34 Figure-of-eight suture pattern, which can be used for wounds involving the eyelid margin. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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6.35 Closure of wound perpendicular to eyelid margin. Longer suture ends may be ‘captured’ in successive sutures or suture knots to aid suture removal. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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6.36 Placement of corneal sutures. Correct depth of suture at one-half to two-thirds of the stromal depth. Suture placed too shallow, resulting in endothelial gaping. Persistent corneal oedema will result. Suture placed too deep, penetrating the anterior chamber and resulting in aqueous leakage. Uneven suture placement will result in stepping of the cornea and poor apposition. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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