Authors: Amar Pujari, Bhupender Yadav, Sujeeth Modaboyina
Categories: Surgical Technique, Ocular hypotony, scleral suture pass, strabismus surgery
Source: Indian Journal of Ophthalmology
During extraocular muscle surgery, an uneventful scleral suture pass is very essential. In presence of normal intraocular tension, the surgery is quite predictable and safe. However, in the presence of significant hypotony, it becomes challenging. Therefore, to mitigate complication rate in these cases, we have adopted a simple technique, that is, the “pinch and stretch” technique. The surgical steps of this technique are as In eyes with significant ocular hypotony, the surgery is initiated with a routine forniceal/limbal peritomy, following which the muscle is sutured and dis-inserted. Using three tissue fixation forceps, the scleral surface is stabilized. Using first forceps, the surgeon rotates the globe toward themself from the muscle stump, and with the remaining two forceps, the assistant pinches and stretches the episcleral tissue in an outward and upward direction just beneath the intended marks. This creates a flat scleral surface with significant firmness. Sutures are passed over this rigid sclera and the surgery is completed without any complications.
Keywords: Ocular hypotony, scleral suture pass, strabismus surgery
Strabismus surgery involves two crucial first, the surgical planning and second, the re-suturing of the recti on the sclera. Intraoperatively, the latter exercise requires good exposure and a better-quality sclera. Once the desired marks are placed and the sutures are passed without any concerns, then the chances of complications are very low.
In some eyes, the intraocular pressures can be very low, or the scleral rigidity can be very weak to withstand the needle pass. In such cases, the surgeon might end up with vision-threatening complications including scleral perforation, vitreous loss, and others. Therefore, in presence of lower intraocular pressures, necessary precautions must be exercised to avoid any of the aforementioned complications.
The rate of scleral perforation during extraocular muscle surgery can vary from less than 1% to 7.8% depending on the type of study.[1–8] In literature, the main reasons for perforation or penetration include recession (more than resection) surgeries, horizontal recti (more than vertical recti) surgeries, inexperienced surgeons, thin sclera, and others.[1–6] However, this is in normal eyes with acceptable intraocular tension; perforation related incidences in hypotonic eyes are unknown. This is due to the lesser prevalence of such cases and also rare surgical intervention in such eyes.
In our experience, certain forms of ocular deviations such as posttraumatic sensory exotropia or eyes on the natural path of phthisis bulbi are at increased risk of perforation (due to naturally declining ciliary body function). Here, we avoid surgeries; however, despite known risks of perforation and accelerated phthisis bulbi, patients often request surgical correction. It is a challenging scenario, but we need to address their concerns positively. In this regard, we have worked on a simple technique through which we have tried to avoid any of the suture-related complications. The patient selection criteria, intraoperative maneuvering, and the outcomes of this technique are as follows.
Patients with significant ocular hypotony and who were willing to undergo corrective surgery were screened. Following counselling on possible intraoperative complications included scleral perforation, abandonment of surgical procedure, and future inability to correct the same, a written and informed consent was obtained. Here, ethical clearance was not necessary because it was an added maneuver over well-established surgical procedures. Nevertheless, throughout patient care we strictly adhered to the tenants of the Declaration of Helsinki.
All eight patients were exotropes; after cleaning the eye, a forniceal peritomy was performed, after which the lateral rectus muscle was hooked, sutured, and dis-inserted in routine fashion. The recession marks were placed on distant sclera (up to 9 mm) [Fig. 1a and b], and at this moment, before securing scleral pass, two to three tissue fixation forceps were one in the surgeon's hand and the remaining two in the assistant's hand. Using the first forceps, the surgeons rotated the globe toward him using the dissected muscle stump [Fig. 1b]. Using two remaining forceps, the assistant made the sclera even and taut as follows.
Figure 1 (a) Significant ocular hypotony can be seen even with minimal indentation from an instrument end (white circle). (b) After dis-insertion, an active pull along the rectus muscle stump reveals an active depression along the muscle path; this confirms the presence of significant ocular hypotony (yellow arrow). On this sclera, suture placement is challenging and also carries the risk of causing perforation and hemorrhage. (c) Along the intended marks or just beneath, two fixation forceps (white asterisks) can be used to pinch and stretch the episcleral tissue in an outward and upward fashion. This brings a noticeable firmness to the scleral surface (yellow arrow). (d) The surgeon uses another pair of forceps and rotates the muscle stump toward themself. This creates a perfect triangle (yellow arrows) with rigid borders and rigid scleral surface (white asterisk represents the forceps holding sclera-episcleral tissue). (e, f) Beyond or within these borders, partial thickness scleral sutures are passed (yellow arrow) and suturing is completed (white asterisk represents the forceps holding episcleral tissue)
The two forceps were introduced just behind the intended scleral marks. After sufficient exposure, the assistant pinched and stretched the episcleral tissue in an outward and upward fashion [Fig. 1c]. This elevated the collapsed sclera and made it rigid [Fig. 1c and d]. Over this surface, the surgeon secured partial thickness sutures [Fig. 1e and f] to complete the recession procedure.
For plication procedure, the muscle was sutured and secured at a desired site, after which it was pulled upwards with the muscle hook. This naturally tightened the anterior sclera, over which sutures were passed and plication was completed.
Using this maneuver, uneventful surgery was performed in eight eyes with significant ocular hypotony (all were measured digitally as the cornea was not clear in many cases, and the non-contact tonometry was not useful). Eight lateral rectus muscles underwent recession procedure and plication procedure in the remaining eight medial rectus muscles. The surgery was quite challenging along lateral rectus muscle, where possible complications were averted using current technique. As far as the medial rectus plication is concerned, as mentioned in the technique section, it was bit easier and uneventful in all eyes.
The current technique describes a simplified approach to extraocular muscle surgery in hypotonic eyes. From our experience, we note that, in eyes with significant ocular hypotony, the main concern is less-taut sclera or its ability to fold/wrinkle on itself while passing the needle. Hence, during suturing, optimal scleral tension is essential in any given surgical scenario. As mentioned above, scleral complications are known in normal eyes, but the current technique highlights a different condition where the chances of perforation are quite high.[4,7,8] In our clinic, we often encounter patients with significant ocular hypotony, because of which, this description was essential. In our limited experience, this technique has worked well, and we were able to circumvent any form of perforations or unpredictable deep penetrations in all eyes.
During surgery, some surgeons may not notice the preexisting hypotony and may encounter it while holding the dissected muscle stump and while rotating it for the first time. At this stage, it manifests as a visible furrow or depression along the intended muscle path (in higher grades of ocular hypotony), as shown in Fig. 1. Furthermore, in other eyes, where the hypotony is of a lesser grade or when it has been missed in the initial steps, it certainly manifests during suturing as scleral wrinkling or difficulty in needle tip navigation.
In both scenarios, the risk of perforation and abandonment of surgery are relatively high. Hence, this maneuver can be adopted to complete the surgery without any hinderance. Nevertheless, in normal eyes also, when one is doubtful on scleral rigidity, this technique can be followed to avoid any complications.
To conclude, while performing extraocular muscle surgery in eyes with significant ocular hypotony, the scleral rigidity can be made favorable by simply pinching and stretching the episcleral tissue in three different directions. This way, the scleral bowing in or wrinkling can be minimized, and the risks of scleral perforation or unpredictable deep penetration can thus be mitigated.
Nil.
There are no conflicts of interest.