FP835 : Comparative Study of Conventional and Four Petal Evisceration Technique with Acrylic Orbital Implant

Dr. Animesh Sahu, S19626, Dr. Ram kishore shandilya, Dr. Narendra Patidar, Dr. Prerana

Introduction: Evisceration is usually performed for functional or cosmetic purposes. The main advantage of evisceration over enucleation, which is the complete surgical removal of the globe from the orbital socket, is that the procedure is simpler, quicker, is performed with less orbital manipulation and haemorrhage, and results in reduced postoperative swelling and pain. Factors favouring evisceration over enucleation are theoretically better eye movements and less chance of postoperative enophthalmos.¹ Evisceration is contraindicated in case of intraocular tumours as it does not allow a complete, controlled removal of the tumour and surgical margins are impossible to evaluate. It is also traditionally contraindicated in eyes that are shrunken as a result of phthisis bulbi as the sclera cannot hold an adequate sized implant which is one of the main determinant factors of good cosmetic results. The ablation of an eye and the subsequent management of the anophthalmic socket still pose a considerable challenge for the ophthalmic surgeon in spite of the numerous modifications of the standard evisceration technique that allow the use of larger orbital implants and the many recent advances in orbital materials. In this study we compared the outcome of conventional and four petal technique evisceration with acrylic orbital implant.

Material and methods: Interventional case series which included a total of 36 patients (36 eyes) who received treatment in form of evisceration with implant for cosmetic reasons or for blind painful eye between April 2016 and May 2017.Detailed history was elicited and a meticulous slit lamp examination was done for all the patients. Nil visual prognosis in the operated eye was clearly explained to the patients. Axial length of the fellow eye was measured by ultrasound for each patient.

Surgical procedure: 20 eyes underwent conventional evisceration with placement of appropriate or the largest possible size of implant. In 16 eyes the four petal evisceration technique as described by Sales-Sanz and Sanz-Lopez  ² was used. In the four petal technique, after separating the eyelids by an eyelid speculum, a 360° conjunctival periotomy was performed, and the dissection was carried out peripherally in the sub-Tenon’s space. The insertions of the recti muscles were identified.The cornea was removed followed by the ocular contents. Four sclerotomies were performed between the rectus muscle insertions from the limbus to the optic nerve fashioning four scleral flaps (or petals). Each petal, containing 1 rectus muscle insertion was separated from the optic nerve. A set of sizing implants was used intraoperatively before inserting the implant to ensure that it could be inserted easily, and the scleral flaps can be closed without tension. Non-porous polyethylmethacrylate (PMMA) implant was used in all cases and was placed inside the four petals. The vertical and horizontal scleral petals were sutured as two separate layers with interrupted 5-0 vicryl sutures. Tenon’s capsule and conjunctiva were sutured separately with 6-0 Vicryl sutures, and an ocular conformer was placed at the end of surgery. Systemic antibiotics, as well as topical combined antibiotic-corticosteroid drops, were prescribed for the 1^st week. The combined drops were used for the following 4 weeks. The patients were referred to an ocularist for fitting of the prosthesis 4-6 weeks after surgery.

Results: 20 patients underwent conventional evisceration while 16 patients were operated by the four petal method of evisceration with placement of appropriate implant. The conventional group had 13 males and 7 females with a mean age 48.40 years. The mean axial length of the fellow eye was 22.98mm and mean implant size was 15.60 mm. The four petal group had  6 males and 10 females with a mean age of 37.81 years. The mean  axial length of the fellow eye was 23.10mm and the mean implant size was 19.06mm. The mean axial length of the fellow eye in both group were comparable but the implant size difference was quite significant. (P value < 0.001).During a mean follow up of 290.80 days implant exposure was found in 2 patients of the conventional group and in none in the four petal group.

Discussion: The importance of complete volume replacement has been emphasized as a primary object of orbital reconstruction procedures. In comparison to enucleation, the advantages of evisceration include relative preservation of tissue, better cosmetic result, superior motility of the prosthesis, and lower risk of spread of intracranial infection or extrusion of the orbital implant. Implant size has traditionally been determined on an empiric basis. Many surgeons use standard implants in all cases, which is often determined by the age of the patient.^(3,4) Others employ a set of sizing implants to ascertain implant size most ideal for a particular individual.^5,6 . Excessively large implants are more prone to extrusion and may compromise the fitting, retention and  comfort of the prosthesis. Placement of an abnormally small implant causes a volume deficit in the socket, contributing to a deep superior sulcus and the need for a large, poorly mobile prosthesis. Kaltreider and Lucarelli⁷ described a simple formula which allowed 100% volume replacement. As per them, the implant diameter for the evisceration procedure was 3mm less than the axial length of the contralateral eye. The most common complication associated with porous orbital implants is exposure of the anterior implant surface. The actual incidences of implant exposure were variable in different reports using different surgical techniques. Viswanathan et al ⁸ in a national survey recorded a 14% exposure rate after evisceration (18 of 128 cases). . Wang et al⁹ reported an 11.4% exposure rate among evisceration cases in their series (8 of 70 cases). Other reports recorded lower exposure rates ranging from 3.3 to 6.5%^10,11 The main risk factors for exposure are inadequate surgical technique, covering the implant with high tension, and persistent conjunctival inflammation.

Standard evisceration techniques typically only allow placement of a 13-16mm spherical implant.^12,13 To achieve optimum volume replacement with insertion of a suitably large implant and reducing the tension on scleral flaps, the technique of evisceration has undergone several modifications. Yang et al¹⁴described scleral quadrisection after evisceration, without releasing  the sclera  from the optic nerve. Massry and Holds¹⁵performed 2 full thickness sclerotomies from the anterior limbus incision to the optic nerve in inferonasal and superotemporal quadrants. Kim et al.¹⁶used evisceration with four anterior full thickness scleral relaxing incisions between the recti muscles insertion to the equator, and a circumferential posterior sclerotomy surrounding the optic nerve for 360^o. Sales-Sanz and Sanz-Lopez²described the four petal technique of evisceration. They performed four sclerotomies from the limbus, between the recti muscles to the optic nerve with release of the scleral flaps from the optic nerve. Huang et al¹⁷ described a similar technique involving scleral quadrisection and suturing the implant with each rectus muscle through the scleral petal. In this series the four petal technique was used to facilitate the insertion of large implant and sclera closure without tension.

In our study with the use of the four petal technique we were able to put implants 2 or 3 mm less than the axial length of the fellow eye  while using the conventional technique we tried to put an implant as large as possible without too much tension over the sclera. During a mean follow up period of  290.80 days we found implant exposure in 2 eyes in the conventional group while no implant exposure was found in four petal group even though we placed larger implants in this as compared to the conventional group.

Conclusion: An implant diameter 2 or 3  mm smaller than the axial length of the contralateral eye provides good volume replacement after evisceration in all patients. The four petal technique facilitates the insertion of larger implants without tension on scleral flaps avoiding implant exposure.

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