|Year : 2018 | Volume
| Issue : 2 | Page : 153-158
Minimally invasive strabismus surgery versus fornix-based incision technique
Nermeen M Badawi
Ophthalmology Department, Menoufia University, Shebin El-Kom, Menoufia Governorate, Egypt
|Date of Submission||29-Aug-2017|
|Date of Acceptance||24-Dec-2017|
|Date of Web Publication||7-Jun-2018|
Nermeen M Badawi
FRCS Ophthalmology (Glasgow), Compound Lake View, 90th Street, Villa 3/1, New Cairo 11835, Cairo Governorate
Source of Support: None, Conflict of Interest: None
Purpose The aim of the present study was to compare the minimally invasive strabismus surgery (MISS) and the Parks’ fornix-based incision technique.
Patients and methods A total of 60 horizontal muscles of 50 eyes of 30 consecutive patients in need for horizontal rectus muscle surgery were included in the present study. They were divided into two groups: group A included surgeries performed with the MISS technique and group B included those performed using the fornix-based incision technique. The comparison addresses both the surgical techniques and the postoperative results, with a follow-up period of 6 months.
Results The operative time was relatively longer in cases of MISS (51.79 min) compared with the fornix incision (30.71 min, P<0.05). The wound size and the number of sutures required to close the wounds were 2–4 sutures (1–2 for each incision) in MISS surgeries, whereas 1–2 sutures were required in the fornix incision technique (P>0.05). Regarding postoperative visibility of the conjunctival signs, signs were hardly visible in 75% of small-sized incisions of MISS cases and in 100% of small-sized incisions in cases of fornix-based incision cases (P<0.05). In medium-sized incisions, both techniques were comparable to each other with moderate signs (P>0.05). Finally, in large-sized incisions, the MISS technique showed better results with less visibility of severe postoperative conjunctival signs (66.7%) than those of fornix-based incision (96%, P<0.05). By the end of the follow-up period, 13 (86.6%) of 15 cases became orthophoric (i.e. angle of deviation less than 10 diopters) in group A, whereas 14 (93.3%) of 15 cases became orthophoric in group B (P>0.05).
Conclusion Each of the two techniques has its advantages. A definite superiority cannot be confirmed. However, it may be safer to use the MISS in elderly people with inelastic conjunctival tissue.
Keywords: esotopia, exotropia, fornix, incisions, minimally invasive strabismus surgery, recti, strabismus
|How to cite this article:|
Badawi NM. Minimally invasive strabismus surgery versus fornix-based incision technique. Delta J Ophthalmol 2018;19:153-8
| Introduction|| |
Conjunctival incision size is one of the main factors influencing postoperative strabismus surgeries outcome . Harms’ limbal incision , which was popularized by Von Noorden ,, causes complications such as suture irritation, Dellen formation , stem cell loss , and scarring . These complications were avoided by the Park’s fornix-based incision , which improved the postoperative outcome  by avoiding the corneal proximity and by decreasing the incisional size ,,,. The incisional size reduction that was presented by Gobin and Bierlaagh  and adopted by Mojon ,, accessed the muscle borders through keyhole openings and was termed ‘minimally invasive strabismus surgery’ (MISS).
The aim of the present study was to compare the technique and outcome of MISS and fornix incision.
| Patients and methods|| |
The study was approved by the Local Ethical Committee of Menoufia University and followed the Helsinki declaration. A written informed consent was obtained from all patients or their guardians before participating in the study.
This is a prospective study performed on 60 muscles of 50 eyes of 30 consecutive patients in need for horizontal rectus muscle surgery to correct either esotropia or exotropia. The patients were divided into two groups: group A was operated on by the MISS technique and included 15 cases, with nine cases being esotropic and six cases exotropic, whereas group B was operated on by the fornix incision technique and included 15 cases, with 10 cases being esotropic and five cases exotropic.
Patients were selected to have a horizontal ocular deviation in need for a double muscle surgery (unifying the number of the muscles to be operated upon was intended to be able to compare the operative time).
The exclusion criteria included the following: history of strabismus surgery, presence of vertical deviation, need of muscle recession of more than 9 mm, planned muscle transposition, indicated retroequatorial fixation sutures, or any medical condition that might increase the bleeding levels.
All surgeries were performed under general anesthesia by the same surgeon.
In group A, recession was performed on 24 muscles, and plication was performed on six muscles. All muscles in group A were accessed through the MISS technique, whereas in group B, recession was performed on 25 muscles, and plication was performed on five muscles. All the muscles in group B were accessed through the fornix-based conjunctival incision.
The minimally invasive strabismus surgery technique
The eyeball was rotated away from the field of surgery using a limbal traction suture ([Figure 1]a). Direct contact with the cornea was avoided. Two small horizontal keyhole incisions were made along the superior and the inferior borders of the muscle. The anterior end of the incision starts at the site of the muscle insertion, and its extent depends on the intended amount of muscle displacement (planning that the opening measures 1 mm less than the amount of muscle to be displaced, [Figure 1]b). The two incisions were used as access points to separate the episcleral tissues from the muscle sheath and the sclera ([Figure 1]c). If necessary, the incisions were prolonged anteriorly and joined with the limbal cut at any time during surgery. The muscle was hooked after identifying its borders. The check ligaments and intermuscular membranes were dissected 6–7 mm behind the insertion creating a tunnel that allows recession or plication to be performed ([Figure 1]d). To perform a recession, two sutures (vicryl 6-0; Ethicon, Forthworth, Texas, USA) were applied at the superior and inferior borders of the muscle tendon as close as possible to the insertion ([Figure 1]e). The tendon was detached using Wescott scissors ([Figure 1]f). Hemostasis was performed at this stage if necessary. The muscle tendon was stretched to avoid central bowing, and then it was resutured to the sclera after measuring the amount of recession ([Figure 1]g).
As for plication, two sutures using vicryl 6-0 (Ethicon) were applied to the upper and lower muscle borders at the distance from the tendon insertion site corresponding to the amount of plication, and then the sutures were passed at the superior and inferior tendon insertions. An iris spatula was inserted between the tendon and the sutures, and the muscle was plicated.
The two incisions were closed at the end the surgery using 8/0 virgin silk (Ethicon) ([Figure 1]h).
Fornix-based conjunctival incision technique
The eyeball was rotated away from the field of surgery using a limbal traction suture. The conjunctival incision was placed parallel to the fornix 7–8 mm from the limbus, either inferotemporally in case of lateral rectus muscle surgery or inferonasally in case of medial rectus muscle surgery midway between the muscles insertions. A Tenon’s capsule incision was made perpendicular to the conjunctival incision. The muscle was hooked, and the conjunctiva was reflected over the muscle incision. The muscle was either recessed or plicated through the incision according to the plan.
At the end of the procedure, TobraDex eye ointment (Alcon, USA) was applied immediately postoperatively. TobraDex eye suspension (Alcon) four times daily and TobraDex eye ointment at bed time were applied for 2 weeks postoperatively.
The two techniques were compared regarding field exposure, final incision size, operative time, and postoperative results, with a follow-up period of 6 months.
The collected postoperative data were postoperative conjunctival swelling and visibility of the incision in the primary gaze that were divided into the following: hardly visible (intact conjunctiva and inability to see the incision in primary gaze), discrete (mildly swollen conjunctiva with inability to see the incision in primary gaze), moderate (moderately swollen conjunctiva with visible incision in primary gaze) and severe (markedly swollen conjunctiva and gapping of the incision with or without subconjunctival hemorrhage). The postoperative angle of deviation was also evaluated.
Data were collected, tabulated, and analyzed using the paired t-test.
| Results|| |
Group A included 25 eyes of 13 (52%) male and 12 (48%) female patients, whereas group B included 25 eyes of 15 (60%) male and 10 (40%) female patients.
The mean age of group A was 23.57±15.57 years (ranging from 7 to 50 years), whereas that of group B was 22.50±16.76 years (ranging from 8 to 46 years).
The mean ocular deviation of group A eyes was 46.40±12.31 prism diopters (PD) [55.60±14.34 PD for esotropic patients (nine patients) and 35.64±13.45 PD for exotropic patients (six patients)] and that of group B was 42.91±11.50 PD [50±18.34 PD for esotropic patients (10 patients) and 38.13±12.32 PD for exotropic patients (five patients)].
Regarding the field exposure, the muscle as a whole was exposed during the operation in case of the fornix-based incision, whereas poor exposure of the field was a problem that was encountered in cases of the MISS technique.
The incisional size in cases of the MISS technique (having two incisions) remained the same all through the operation (size of muscle displacement − 1 mm). It ranged from 4.0–8.0 mm (mean=5.50±1.03 mm). Two to four buried stitches (1–2 for each incision according to the size) were used for conjunctival closure. As for the fornix-based incision, the final incision size was within 4.0–5.0 mm in 80% of cases, which needed only one stitch for closure. However, the wound underwent extension up to 8.0 mm in 20% of cases especially in elderly people with inelastic conjunctiva, which needed two sutures for closure. So, the final incision size ranged between 4.5 and 8.0 mm (mean=5.36±0.91 mm) in all fornix-based cases (P>0.05, [Figure 2]).
By calculating the total size of incisions in cases of MISS technique, the mean size was 11.00±2.05 mm, whereas the mean incisional size (i.e. the size of incision in case of gapping) of fornix-based incision was 5.36±0.91 mm (P<0.05, [Figure 3]).
The operative time for a two-muscle surgery was longer in MISS technique as it was 51.79±6.39 min, whereas in the fornix incision technique, it was 30.71±6.46 min (P<0.05, [Figure 4]).
As for the postoperative conjunctival swelling and visibility of the incision in the primary gaze, these signs were compared in both groups ([Figure 5]) and plotted to the incisional size ([Figure 6]), which showed that in case of small incisions sized 4.0–5.0 mm, conjunctival signs were hardly visible in 75% of cases of MISS, whereas they were hardly visible in 100% of fornix-based incisions (P<0.05). In medium-sized incisions (5.0–6.0 mm), signs were moderate in 100% of MISS cases compared with 97% of fornix-based cases, with 3% of them showing discrete signs (P>0.05). In incisional size equal to or more than 6.0 mm, 66.7% of MISS cases showed severe conjunctival signs and the remaining cases showed moderate signs, whereas in cases of the fornix-based technique, 96% of the cases showed severe signs, with only 4% showing moderate signs (P<0.05, [Figure 6]). All these signs resolved within 2 weeks.
By the end of the follow-up period, 13 (86.6%) of 15 cases were orthophoric (i.e. ocular deviation<10 PD) in group A, and the remaining two cases (13.4%, originally esotropic) had a residual angle more than 10 PD, whereas 14 (93.3%) of 15 cases were orthophoric in group B, and the remaining case (originally exotropic) had a consecutive angle more than 10 PD (P>0.05).
| Discussion|| |
In recent decades, a leading trend throughout all surgical specialties has been to reduce the size of the incision and the area of manipulation, following the ‘less is more’ rule . This trend led to the introduction of a new term to strabismus surgery, small incision or mini techniques. These terms are now widely used by many surgeons to describe their techniques ,. However, the term MISS became associated with Mojon’s minimally invasive technique.
The present study compared two surgical techniques for accessing the muscle in strabismus surgery aiming at decreasing the size of the conjunctival incision in strabismus surgery, hence decreasing conjunctival complications, tissue disruption, and postoperative discomfort: (a) MISS and (b) fornix-based conjunctival incision. Although Mojon  stated that some surgical instruments might be helpful for performing the new technique, no special surgical instruments were needed neither by the author nor by Pavlou  to perform MISS. However, as Mojon  noted, no surgical assistance was needed during the procedure, thereby leading to some advantage over the fornix-based technique. It was still notable that the time needed to perform the MISS (51.79±6.39 min) was longer than that needed to perform the surgery through a fornix-based incision (30.71±6.46 min). This may be influenced by the surgeon’s longer experience with the fornix incision. However, creating two preplanned conjunctival incisions of a specific length and closing them by 2–4 sutures added to the less exposed operative field are parameters that may lead to consumption of a relatively longer time compared with the fornix-based technique.
As the main aim of these two techniques was to reduce the size of conjunctival incision, comparing the sizes of conjunctival incisions of both techniques and its effect on the postoperative signs was a main parameter in evaluating both techniques. The mean final size of the incision in the fornix incision technique ranged from 4.5 to 8.0 mm if accidently extended (in cases of inelastic conjunctiva), with a mean of 5.36±0.91 mm, and was closed by 1–2 sutures. This was comparable to the results of Pérez-Flores , whose fornix-based incisions were closed by a mean of 1.39±0.46 sutures. However, in the MISS cases, in the present study, two incisions were created, each of them ranging from 4.0 to 8.0 mm (according to the amount of recession or plication), with a mean of 5.50±1.03 mm, for a single incision. So, the total incised area was 11.00±2.05 mm closed by 2–4 sutures, that is, double that of the fornix-based incision. Yet, the size of the incision in MISS cases was preplanned and regular whereas that of fornix-based incision was subject to gapping and extension as it depends on the conjunctival elasticity. This is particularly noteworthy in elderly cases, where conjunctival elasticity decreases, and this increases the incidence of gapping with more conjunctival manipulations.
The postoperative visibility of the conjunctival signs was related to the size of the incision. It was notable that with small-sized incisions (<4.00 mm), the fornix-based technique had better results. However, with medium-sized incisions (4.00–6.00 mm), the two techniques had comparable results with mild-to-moderate signs. However, in case of incisions larger than 6.00 mm, the fornix-based incision showed more severe cases (96%) than those caused by the MISS (66.7%) as the large size of the incision in case of fornix-based incision was owing to gapping with more conjunctival manipulations rather than the regular preplanned incision in case of MISS.
No Tenon’s capsule-related difficulties were experienced with either one of the two groups. This might be related to the age group of the study, as Tenon’s capsule-related difficulties are expected in infants and young children.
| Conclusion|| |
Each of the two techniques has its advantages; a definite superiority cannot be confirmed. However, it may be better to use the MISS technique in elderly people as it needs less manipulation to the inelastic conjunctival tissues.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]