Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009

Infections of the Orbit 329

10.Levin LA, Avery R, Shore JW, Woog JJ, Baker AS. The spectrum of orbital aspergillosis: a clinicopathological review. Surv Ophthalmol 1996 Sep-Oct;41(2):142-54.

11.Levine SR, Twyman RE, Gilman S. The role of anticoagulation in cavernous sinus thrombosis. Neurology 1988 Apr;38(4):517-22.

12.Mahesh L, Biswas J, Subramanian N. Role of ultrasound and CTscan in diagnosis of hydatid cyst of the orbit. Orbit 2000 Sep;19(3):179-88.

13.Mauriello JA Jr, Yepez N, Mostafavi R, Barofsky J, Kapila R, Baredes S, Norris J. Invasive rhinosino-orbital aspergillosis with precipitous visual loss. Can J Ophthalmol 1995 Apr;30(3):124-30

14.McKinley SH, Yen MT, Miller AM, Yen KG. Microbiology of pediatric orbital cellulitis. Am J Ophthalmol 2007 Oct; 144(4):497501.

15.Mohindra S, Mohindra S, Gupta R, Bakshi J, Gupta SK. Rhinocerebral mucormycosis: the disease spectrum in 27 patients. Mycoses 2007 Jul;50(4):290-6.

16.Panda NK, Balaji P, Chakrabarti A, Sharma SC, Reddy CE. Paranasal sinus aspergillosis: its categorization to develop a treatment protocol. Mycoses. 2004 Aug;47(7):277-83.

17.Pushker N, Bajaj MS, Betharia SM. Orbital and adnexal cysticercosis. Clin Exp Ophthalmology Oct 2002;30(5):322-33.

18.Shome D, Honavar SG, Vemuganti GK, Joseph J. Orbital tuberculosis manifesting with enophthalmos and causing a diagnostic dilemma. Ophthal Plast Reconstr Surg 2006 May-Jun;22(3):219-21.

19.Siddiqui AA, Bashir SH, Ali Shah A, Sajjad Z, Ahmed N, Jooma R, Enam SA. Diagnostic MR imaging features of craniocerebral aspergillosis of sino-nasal origin in immunocompetent patients. Neurochir (Wien) 2006 Feb;148(2):155-66.

20.Sihota R, Honavar SG. Oral albendazole in the management of extraocular cysticercosis. Br J Ophthalmology 1994;78:621-3.

21.Sihota R, Sharma T. Albendazole therapy for a recurrent orbital hydatid cyst. Indian J Ophthalmol 2000;48:142.

22.Turgut AT, Turgut M, Koºar U. Hydatidosis of the orbit in Turkey: results from review of the literature 1963-2001. Int Ophthalmol 2004 Jul;25(4):193-200.

23.Uy HS, Tuano PM. Preseptal and orbital cellulitis in a developing country. Orbit 2007 Mar;26(1):33-7.

24.Youssef OH, Stefanyszyn MA, Bilyk JR. Odontogenic orbital cellulitis. Ophthal Plast Reconstr Surg. 2008 Jan-Feb;24(1):29-35.

INTRODUCTION

Orbital implants are devices, natural or synthetic, used to replace the orbital volume lost after enucleation or evisceration procedures.

An ideal implant should have the following features:

1.Mimics the normal globe as much as possible.

2.Must replace sufficient orbital volume.

3.Non-antigenic and biologically inert.

4.Light weight and simple in construction.

5.Allow for prosthesis of adequate anterior chamber depth.

6.Porous structure to allow fibrovascular ingrowth and better stability.

7.Provide socket motility transmitted to the prosthesis to simulate normal globe and socket as much as possible.

8.Buried and placed in intraconal space with good surgical technique to produce good cosmetic and functional results.

9.Minimal rates of exposure, extrusion, infection and inflammation.

Types of Implants

•Integrated/non-integrated

•Buried/exposed.

Orbital Implants 331

Non-integrated → no direct attachment to extraocular muscles or prostheses.

→single spheres of inert material buried beneath the conjunctiva and Tenon’s capsule in the muscle cone

→the recti may or may not be imbricated or incorporated into the soft tissue closure

Examples → spherical implants made of PMMA, glass,silicon, acrylic etc

Status of non-integrated implants—have low complication rates (infection, extrusion) but poor motility. To improve motility they can be wrapped with sclera/fascia lata/vicryl mesh which provides an anchor for extraocular muscles attachment and an extralayer between the implant and prosthesis resulting in low extrusion rates. It does not allow fibrovascular ingrowth thereby increasing the chances of implant migration.

Integrated →is designed in a manner to allow attachment of extraocular muscles and has anterior surface projections to push the prostheses in synchrony to the implant.

Examples → Allen, Iowa and Universal implants (nonporous)

→hydroxyapatite, polyethylene, alumina, etc. (porous)

Status of integrated implants—porous implants allow

ingrowth of fibrovascular tissue providing greater stability and increased resistance to extrusion (Is supplied with host immune defences thereby reducing infection, migration, extrusion). Allows placement of motility/support peg providing excellent motility, decrease of weight of prostheses on lower lid and minimizes sagging.

Proper sizing of the implant at the time of insertion is important; if too small—will cause enophthalmos and

332 Oculoplasty and Reconstructive Surgery

superior sulcus deformity; if too large – will produce exophthalmos/staring appearance and increase the incidence of dehiscence, entropion of lids and lack of proper lacrimal lubrication of the anterior prosthetic surface. Implant sizer kit is available to find the optimal size preoperatively. Insertors are available to ease the procedure of inserting the implant without infolding the surrounding soft tissue.

NEWER GENERATION ORBITAL

IMPLANTS (Figures 1 to 19)

Hydroxyapatite

Hydroxyapatite implant is close to being an ideal buried integrated implant. Hydroxyapatite is a calcium phosphate hydroxide compound made up of multiple interconnecting pores of diameter 500 microns. The implant material (corralline hydroxyapatite) is biocompatible, non-toxic and non-allergenic. The body’s tissue recognizes the material as similar to human cancellous bone and because of the porous nature, tissue will grow into it. The implant becomes more fixed and therefore resists migration. The implant allows attachment of the extraocular muscles which in turn leads to improved orbital implant motility. The orbital implant can also be directly attached to the prosthesis through a peg, protruding from the implant allowing a wide range of prosthetic movement as well as the darting eye movements commonly seen when people are engaged in conversation. Once vascularized, the chances of infection/extrusion/ migration are minimized. To offset the high costs of preparing the natural coral, an artificial variant has been made for a cheaper price.