|Year : 2004 | Volume
| Issue : 3 | Page : 221-6
Myoconjunctival enucleation for enhanced implant motility. result of a randomised prospective study.
U Yadava, P Sachdeva, V Arora
Maulana Azad Medical College and allied Guru Nanak Eye Centre, New Delhi, India
|Date of Submission||16-Sep-2002|
|Date of Acceptance||08-Mar-2004|
Maulana Azad Medical College and allied Guru Nanak Eye Centre, New Delhi
Source of Support: None, Conflict of Interest: None
PURPOSE: Implant motility and cosmetic appearance of the eye after enucleation have remained major considerations whenever mycoconjunctival enucleation is planned. Despite major advances in surgical technique and the availability of a variety of implant materials and shapes, there is lack of consensus on the best material and type of implant. This study was conducted to compare routine and myoconjunctival techniques of enucleation in terms of motility index. METHODS: Thirty consecutive patients scheduled for enucleation for non-malignant indications were randomly assigned to one of the two groups- routine and myoconjunctival techniques. The postoperative results were compared for the motility of implant and the complications. RESULTS: The two techniques showed no difference in rates of complications, but implant motility was significantly better with the myoconjunctival technique. Implant extrusion or migration was not seen. CONCLUSION: We recommend the use of myoconjunctival enucleation for enhanced motility and cosmesis.
Keywords: Myoconjunctival enucleation, implant, scleral graft, prosthesis
|How to cite this article:|
Yadava U, Sachdeva P, Arora V. Myoconjunctival enucleation for enhanced implant motility. result of a randomised prospective study. Indian J Ophthalmol 2004;52:221
|How to cite this URL:|
Yadava U, Sachdeva P, Arora V. Myoconjunctival enucleation for enhanced implant motility. result of a randomised prospective study. Indian J Ophthalmol [serial online] 2004 [cited 2019 Jun 25];52:221. Available from: http://www.ijo.in/text.asp?2004/52/3/221/14587
Enucleation is a surgical procedure in which the globe and the attached portion of the optic nerve are excised from the orbit. Rehabilitation and cosmesis remain the nemesis of an anophthalmic socket. After enucleation, the cosmetic goal is to replace the lost volume of the socket and to restore natural appearance and movement with an artificial eye. To this end, implants of various materials, shapes and sizes have been used from time to time. These include glass, gold, tantalum, vitallium and silicon. Certain newer materials include hydroxyapatite,,, protoplast (a combination of teflon fluorocarbon polymer and vitreous carbon fibres) and goretex.
Of all the biologically inert materials, silicon is most often used in ophthalmology. Silicon offers a less hard and weighty subsitute which is in itself an advantage, as bigger the size of the implant the better the end result. Silicon also has the lowest rates of exposure and extrusion.,
Placement of scleral graft provides an added protective barrier against implant extrusion, while placement of sclera about the implant and suturing the rectus muscles to the scleral graft increases the motility of the implant. Sclera offers the advantages of easy availability in eye banks, easy preservation and storage, good tensile strength, low incidence of rejection, little inflammatory reaction and easy retention.
We did a comparative evaluation of routine and myoconjunctival techniques of enucleation and used the motility index for quick and reliable assessment of implant motility.
| Materials and Methods|| |
Thirty patients scheduled for primary enucleation for non-malignant indications, at Guru Nanak Eye Centre, New Delhi, were selected as subjects for the study.
A thorough systemic and ocular examination was conducted and patients were included in the study after ruling out the following: ocular malignancy, conjunctival shrinkage, adnexal deformities, infection, gross deformity of globe, and patients posted for secondary implant. Informed consent was obtained from each of the subjects after providing a detailed explanation of the procedure.
The patients were alternately assigned to one of the two groups:
Group I: Routine enucleation with implant (RT)
Group II: Myoconjunctival enucleation with implant (MCT)
All surgeries were performed by the same surgeon under local anaesthesia (5cc 1:1 mixture of lignocaine 2% with adrenaline 1:200000 and bupivacaine 0.5% in retro bulbar space) and a spherical silicon orbital implant was used in all cases.
Surgical steps of RT:
1. A self-retaining eyelid speculum was applied.
2. 360° peritomy was done using Wescott scissors
3. The underlying Tenon's layer was undermined in all quadrants up to the equator [Figure - 1].
4. Each of the four recti, commencing with medial rectus, was hooked, identified, secured on double-armed 6-0 vicryl suture and detached from the globe .
5. Superior and inferior oblique tendons were amputated close to the insertions and muscles allowed to retract .
6. An Arruga spoon was inserted behind the globe temporally and the optic nerve disinserted using enucleation scissors. Haemostasis was achieved by pressure with soaked gauze for 5 minutes.
7. The silicon implant was put in the orbit; four recti were passed through tunnels in the implant and sutured to each other anterior to it .
8. Tenon's layer was closed with interrupted 4-0 prolene sutures.
9. Conjunctiva was closed with running 6-0 chromic catgut sutures.
10. A polymethylmetaacrylate (PMMA) conformer was applied and a light pressure bandage was done.
Surgical steps of MCT
1. The initial steps of conjunctival peritomy, undermining of the Tenon's layer and disinsertion of the four recti were similar.
2. Superior oblique tendon was hooked, detached from the globe and attached to superior rectus muscle.
3. Inferior oblique tendon was hooked, detached from the globe and attached to lateral rectus muscle at its inferior border close to the insertion.
4. An Arruga spoon was inserted behind the globe temporally and the optic nerve cut using enucleation scissors. Haemostasis was achieved by pressure with soaked gauze for 5 minutes.
5. Silicon implant was covered with the scleral coat of eye just enucleated after cleaning off all the uveal tissue. The scleral surface was used to anchor the respective muscles in their positions before exteriorisation.
6. The anterior layer of Tenon's was closed in a diagonal fashion (superonasal to inferotemporal and superotemporal to inferonasal) using interrupted 6-0 prolene sutures [Figure - 2].
7. Each of the four rectus muscle sutures was then passed through the overlying conjunctiva. The superior and inferior recti were placed 12mm from the horizontal edge of conjunctival wound in their respective fornix. The medial and lateral recti were attached myoconjun-ctivally to medial and lateral fornices 25mm apart [Figure - 3].
8. Conjunctiva was closed with running 6-0 chromic catgut sutures.
9. A PMMA conformer was placed and light pressure bandage was applied.
All patients were evaluated daily in the first week, weekly for the next 6 weeks and at the end of 8, 10 and 12 weeks.
The parameters looked for included the symptoms like pain, and watering, lid oedema ecchymosis, chemosis/ wound gape, haematoma, exposure/ extrusion of implant, and implant motility. For an objective measurement of implant motility, with the patient looking in the primary gaze, a '+' shaped piece of micropore tape with an ink mark in its centre was placed on the conjunctiva overlying the centre of the implant [Figure - 4]. The patient was then instructed to look to the left, right, up and down and the excursion of the ink mark was measured using a standard mm ruler. Total horizontal and vertical excursions were calculated and compared. The mean of upward, downward, medial and lateral movements was calculated and labeled as the "Motility Index" (MI). [Figure - 4] also shows the implant motility in up, down, medial and lateral gazes. [Figure - 5] shows the horizontal motility of the prosthesis.
| Results|| |
The mean age in group I was 37.4 (± 20.26) years while that in group II was 33.5 (± 16.52) years. Both groups were also matched for gender with a male to female ratio of 6:4.
The indications for enucleation in the two groups are shown in [Table - 1]. Overall, anterior staphyloma accounted for 60% of cases, atrophic bulbi for 25%, intractable endophthalmitis for 10% and neovascular glaucoma for 5% of cases.The surgical procedure was uneventful in all cases.
The patients in both groups had a similar postoperative course in terms of symptoms and objective signs. Most of the symptoms subsided by the end of the first week.
One patient in group I had a shallow upper fornix, which was dealt with by a mucous membrane graft; thereafter, the course was uneventful. Mild ptosis persisted in all cases after fitting of the prosthesis. All patients had a deep superior sulcus. No case of implant migration or extrusion was seen.
At the end of 12 weeks, motility measurements were taken and compared. The results are shown in [Table - 2]. In Group I, mean medial movement (MM) was 3.4 mm, mean lateral movement (LM) was 1.7 mm, mean upward movement (UM) was 2.2 mm, mean downward movement (DM) was 2.2 mm, mean horizontal excursion [MM + LM] was 5.1 mm, mean vertical excursion [UM + DM] was 4.4 mm.
In Group II, mean MM was 4.4 mm, mean LM was 2.8 mm, mean UM was 3.2 mm, mean DM was 3.0 mm, mean horizontal excursion [MM + LM] was 7.2mm, mean vertical excursion [UM + DM] was 6.5mm.
Group II was stastistically superior to Group I in terms of implant motility in all four directions. [The P value for MM was 0.002, for LM was 0.003, for UM was 0.034, for DM was 0.011, for horizontal excursion [MM + LM] was 0.007 and the P value for vertical excursion [UM + DM] was 0.001].
The motility in group II was significantly better than in group I in each direction of gaze, horizontal and vertical excursions as well as mean motility as measured by the motility index (MI) [Student's unpaired t-test].
| Discussion|| |
The patients undergoing enucleation lose not just their self-esteem but also social acceptability due to poor cosmesis. The conventional method of enucleation hardly ever provides motility of the socket and patients have no choice but to accept a sub-optimal cosmesis.
Coston described suturing of extraocular muscles to the fornix. Chen (Enucleation with myoconjunctival attachment: Biomechanics of socket and prosthetic motility. t0 hesis prescribed at the Annual Scientific Symposium of the American Society of Ophthalmic Plastic and Reconsructive Surgery. Atlanta, USA, 1981) described the interrelationship of forniceal movement and prosthetic motility and together with McCord outlined the myoconjunctival technique (MCT) of enucleation. In our study, we used Nunery and Chen's modification of MCT. The technique involves the suturing of extraocular muscles to the implant [wrapped with sclera] in their respective anatomic positions, suturing of extraocular muscles subconjuctivally to their respective fornices, spacing them 25 mm apart vertically and horizontally to increase implant stability and prosthetic motility, attaching the superior oblique to the superior rectus and inferior oblique to inferior border of the lateral rectus, suturing of anterior Tenon's from opposite oblique quadrants, and suturing of conjunctiva as a separate layer.
According to Kkaltreider, et al, axial length of fellow eye (measured by ultrasonography) can be used to predict the implant size before surgery. Thaller described the use of water displacement in a graduated measuring cylinder for predicting the implant size. Optical sizers are also available for the same purpose. In order to maintain uniformity, we used same size (16 mm) and same material (pre-sterilized silicone with 4 tunnels) of the implant in all patients. We did not see any implant migration or extrusion.
According to Dortzbach, implant extrusion is caused by orbital haemorrhage, infection and lack of secure closure of Tenon's capsule. According to Peyman, a spherical implant is easier to fit with prosthesis and minimises pressure and friction points, thus preventing tissue necrosis and extrusion. Wrapping the implant with sclera prevents implant migration and extrusion., Nunery et al reported 0.84% extrusion with silicon implants.,
Our findings were in accord with those of the above mentioned authors. One case of shallow upper fornix seen in our series was due to inadequate dissection of Tenon's capsule. It was successfully treated with buccal mucosal grafting in the eighth week after which the course was uncomplicated. Dortzbach et al have already highlighted the importance of proper and adequate dissection of the Tenon's capsule.
Mild ptosis [ptosis less than or equal to 2mm] appeared in all of our patients. Some ptosis [ptosis equal to 1mm] persisted even after fitting of the prosthesis. Off-the-shelf prostheses do not conform to the exact configuration, leading to ptosis. This is not seen with custom made impression moulded casts.
A deep superior sulcus was seen in all patients. The aetiology of an anophthalmic superior sulcus defect is multifactorial and includes loss of orbital volume, diminished soft tissue support, posterior and inferior rotation of levator palpebrae superioris - superior rectus complex ,, and retraction of pre-aponeurotic fat pad., Various methods have been described to deal with this problem including conical orbital implant, sub-periosteal implant and direct augmentation of the superior sulcus. However, in the settings of our study, we could not deal with the deep superior sulcus, which was within cosmetically acceptable limits and was present in both groups.
Comparisons of implant motility were made after calculation of the motility index (MI). This is not only simple but also offers a foolproof basis for comparison. It is an objective method and reduces the inter-observer bias.
Spherical implants impart motility to the prosthesis by providing a smooth pivotal surface over which the prosthetic shell passively glides during shortening and lengthening of fornices. According to the Starling hypothesis, muscle contraction is compromised by unduly stretching the muscle beyond its original length.
In routine enucleation muscles were attached to each other in front of the implant, causing stretching of the muscles. On the other hand, in MCT, each rectus was sutured to the scleral shell around the implant and thence to the respective fornix, thus preventing any stretching.
MCT gives better motility to the prosthesis for the following reasons:
1. The extraocular muscles (EOMs) are sutured to the implant in their normal anatomic positions.
2. EOMs are sutured to the fornices to increase implant stability and prosthetic motility.
3. The implant is wrapped around sclera which provides additional volume and surface for suturing EOMs. Hence it provides better motility and also acts as an additional barrier.
4. Tenon's and conjunctiva are closed seperately in multiple layers. Our findings corroborate those of Nunery and Chen that poor prosthetic motility is due to use of the Frost and Lange , technique involving imbrication of rectus muscles over the spherical implant and that good prosthetic motility can be achieved by suturing recti independently to the implant reinforced with sclera.,  "The figures of 24 mm for horizontal fornices and 25 mm for vertical fornices during final suturing were found to be optimum for MCT."
The medial rectus insertion is separated from the lateral rectus insertion by an arc distance of approximately 24mm. Similarly, the vertical muscles are 25mm apart. The extraocular muscles retain their optimal physiologic contractile function when they are placed at an ideal length , close to its normal physiologic length-tension relationship (s0 tarling l0 aw).
Recent literature ,,, abounds in references to the use of hydroxyapatite (HAP) implants. But HAP has higher rates of exposure (11%), infection and re-operations as compared to silicon (0%). HAP is relatively expensive in India. Moreover, in the event of suspected or proven recurrence of malignancy from the optic nerve stump, the clinician must be adequately trained to interpret MRI scans with HAP implant in situ and also be equally efficient in removing the integrated HAP implant. Custers, et al reported similar motility with silicon and HAP implants.
We therefore recommend the use of MCT with silicon implant as the procedure of choice in primary enucleations, even in cases of malignancy. MCT combined with a well fitting and well painted prosthesis can make all the difference in the final cosmetic result. Results can be further augmented by use of a custom-made prosthesis.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]
[Table - 1], [Table - 2]
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