| CHAPTER | 26 | Eye Surgery |
▃Lid Surgery
■Entropion
Treatment of entropion includes medical and surgical therapy. Medical therapy: It includes a temporary treatment with lubricants, taping and soft bandage contact lens. The aim of surgery for involutional entropion is to correct the underlying problems involved in its pathogenesis. The surgery for involutional entropion may involve a combination of more than one procedure.
•Horizontal lid laxity is corrected with resection and reconstruction of lateral canthal tendon and preferred over purely tarsal resection performed in central eyelid, as the evidence suggests that the dysfunction resides in the canthal tendon and its attachment rather than in the tarsal plate itself.
•Orbicularis muscle dysfunction is corrected by creating a fibrous barrier between the skin and the deeper eye lid structures at the junction of the pretarsal and preseptal orbicularis. This can be achieved through full-thickness horizontal lid splitting at this level and the insertion of everting sutures (Wies procedure). The stimulation of fibrosis through the use of sutures creates a barrier between preseptal and pretarsal orbicularis, preventing the overriding of preseptal over pretarsal orbicularis (Fig. 26.1).
•Vertical lid instability is best corrected by reattachment or tightening of the lower eyelid retractors (Jones procedure). The capsulo-palpebral fascia is advanced or reattached to the inferior tarsal border via a transcutaneous approach (Fig. 26.2).
Fig. 26.1 Wies procedure.
Fig. 26.2 Jones procedure.
Spastic Entropion
It is due to the spasm of orbicularis oculi which can be induced by local irritation or infection. Spastic entropion is almost always restricted to the lower lid. Spastic entropion is thought to be a subset of involution entropion, as the spasm of orbicularis oculi can unmask the symptomatic involutional changes that allow the orbicularis to ride up in front of tarsal plate and approximate the lid margins and turn them inward, resulting in temporary entropion. The condition is found particularly in old age and may be caused by tight bandaging. It is favored by narrowness of palpebral aperture (blepharophimosis).
Treatment
The cause for the spastic entropion must be identified and treated:
•If it is due to blepharitis, it is treated by eyelid hygiene, antibiotics and corticosteroids.
•If it is due to bandaging, it can be cured by removing the bandage.
•If the entropion persists, small amounts of botulinum toxin (BOTOX, 5U) may be injected into the pretarsal plate orbicularis and overriding is prevented by weakening it.
•Patients with cicatricial entropion secondary to ocular cicatricial pemphigoid may benefit from systemic chemotherapy, usually dapsone.
Cicatricial Entropion
Cicatricial entropion can be distinguished from involutional entropion by:
•The patient’s history.
•Digital traction on eye lid: It will correct the abnormal margin position in involution entropion but not in cicatricial entropion.
•Inspection of posterior aspect of eye lid reveals scarring of tarsal conjunctiva in cases of cicatricial entropion.
Treatment
Medical treatment– Bandage contact lenses keep the lashes away from the cornea.
Surgical treatment: The repair of cicatricial entropion will depend on the degree of scarring and entropion, etiology of cicatricial changes, and status of tarsal plate. The basic principles governing the various operations are restoration of the normal direction of lashes and tarsal rotation.
Mild case can be treated with a transverse tarsotomy (tarsal fracture) and anterior rotation of lid margin (Fig. 26.3).
Fig. 26.3 Tarsal fracture.
More extensive scarring may require the replacement of conjunctiva by a mucous membrane (e.g., buccal mucosa). Assess the status of tarsal plate in all cases of cicatricial entropion. If it is distorted, excision of the distorted portion of the tarsal plate is replaced by a cartilage (ear cartilage), hard palate grafts and chondromucosal grafts.
■Ectropion
Treatment
The treatment depends predominantly on the location of ectropion.
•If the ectropion is generalized, it is treated with horizontal lid shortening by excision of a full-thickness pentagon of the lid. It corrects the ectropion completely. It can be performed at any point on the lower lid, but the preferred site is usually in the lateral third (Fig. 26.4a).
•Medial ectropion (involving punctal area) can be treated with medial tarsoconjunctival diamond excision. A diamond-shaped segment of tarsus and conjunctiva is resected directly below the punctum (edge of the diamond is placed 2 mm below the lid margin to protect the canaliculi). A suture is placed untied which rotates the medial lid margin and punctum inward (Fig. 26.4b).
Fig. 26.4 (a) Horizontal lid shortening. (b) Medial tarsoconjunctival diamond excision. (c) Lazy-T procedure. (d) Kuhnt–Szymanowski procedure.
If the medial ectropion with punctal eversion is associated with predominantly medial horizontal lid laxity, medial diamond excision is done with horizontal lid shortening (Lazy-T procedure) (Fig. 26.4c).
•If the ectropion is severe and more marked over the lateral half of the lower lid, a Kuhnt–Szymanowski procedure modified by Bryon Smith is performed. This procedure involves shortening of the eyelid with elevation of temporal margin. In this procedure, a tarsoconjunctival excision is made from the middle part of the lower lid. A line is drawn 3 mm inferior to the lid margin, following the contour of the lower lid. An incision is made 2 to 3 mm inferior to the lid margin. A skin flap is prepared and an appropriate triangular piece of skin is resected at the outer canthus. The wound is closed and the lid margin is mobilized upward and outward to cover the skin incision (Fig. 26.4d).
Cicatricial Ectropion
It is caused by burns, trauma and chronic inflammations of skin, resulting in scarring of the skin and underlying tissues which pulls the eyelid away from the globe.
Treatment
Localized areas with scarring can be released by Z-plasty or V–Y operation.
Z-plasty: The three stages of Z-plasty include:
•Incisions making triangular flaps.
•Flaps are moved into their new positions.
•Flaps are interlocked and wound is closed.
The middle line of the “Z”-shaped incision is made along the line of greatest tension or contraction, and the triangular flaps are raised on the opposite sides of two ends and transposed (Fig. 26.5a).
V–Y plasty: A “V”-shaped incision with its apex away from the lid margin is made to release the scarred tissue. The skin is undermined and sutured in a “Y”-shaped manner (Fig. 26.5b).
Fig. 26.5 (a) Z-plasty. (b) V–Y plasty.
Severe generalized scars require skin grafts. Scars are excised and the surrounding skin is released from the underlying adhesions before the application of a skin graft. The sources of skin graft are the upper lid and behind the ear or inner upper arm.
■Ptosis
The management of ptosis is variable according to the cause. In neurogenic ptosis, the patient should be reviewed periodically for any spontaneous recovery. In complete paralysis of III nerve, surgery is usually contraindicated, as elevation of the ptotic eye leads to diplopia due to ophthalmoplegia. The proper choice of operation for the various types and degrees of ptosis is performed.
Age for Surgery
The ideal time for surgery is when a sufficiently accurate preoperative examination can be made. If ptosis is partial, 4 to 5 years of age is probably an ideal age. If the lid covers the visual axis due to ptosis, a temporary placement of nonabsorbable sutures (for lid elevation by brow suspension) may be indicated as soon as possible to avoid sensory deprivation amblyopia. At the age of 4 to 5 years, sutures are removed to re-evaluate the ptosis and to do a more definitive operation.
Type of Surgery
It is determined by amount of ptosis, levator function and associated anomalies (e.g., Marcus–Gunn phenomenon).
•Amount of ptosis: Table 26.1 highlights the amount of ptosis as per the eyelid droop.
•Levator function: It is termed good if it is 8 mm or more (≥8 mm), fair if it is 5 to 7 mm and poor if it is 4 mm or less (≤4 mm).
Table 26.1 Determination of the amount of ptosis | |
Amount of ptosis | Droop of eyelid |
Mild Moderate Severe | If the eyelid droops 2 mm or less (≤2 mm) from its normal level. If the eyelid droops 3 mm. If the eyelid droops 4mm or more (≥4 mm). |
Levator Palpebrae Superioris (LPS) Resection
A definitive preoperative determination of the amount of levator to be resected is required. A millimeter caliper is used at surgery to measure the resection.
A resection of: | 10–13 mm is termed small |
14–17 mm is termed as moderate. | |
18–22 mm is termed as large | |
and LPS resection of | 23 mm or more (≥ 23 mm) is termed as maximum. |
The result of any resection can be enhanced slightly by advancement on the anterior surface of tarsus in skin-approach resection or tarsal resection when the conjunctival approach is used. A tarsal resection should not amount to more than half of its vertical width.
In treating “congenital” ptosis, it is well to choose the large resection because overcorrection is easier to treat than undercorrection. In treating “acquired” ptosis, the levator resection must be more conservative because more postoperative lift is expected after the surgical correction of these cases, that is, overcorrection is easy to obtain but may be disastrous.
Standard Ptosis Procedures
A basic set of procedures includes:
•Vertical lid shortening (Fasanella–Servat operation).
•LPS resection (conjunctival/skin approach).
•Aponeurosis advancement and tucking.
•Brow-suspension ptosis repair.
Fasanella–Servat Operation
It is chiefly a tarsal resection. The amount of LPS tendon excised is so small that no lifting effect could be expected from it. It is rather a tarsectomy and shortening of Müller’s muscle and conjunctiva only.
Indication: Mild ptosis (1.5–2 mm) with good LPS function.
Procedure: Following are the steps involved to carry out Fasanella–Servat operation (Fig. 26.6):
Fig. 26.6 Steps involved in Fasanella–Servat operation.
1.Upper lid is everted. Two curved hemostats are applied grasping the conjunctiva, tarsus. Müller’s muscle and LPS.
2.Upper tarsus is excised by 4 to 5 mm.
3.The running suture is placed. A small skin incision is made in the lid crease immediately above the lateral canthus. The two ends of suture are made through the skin incision and tied. The knot is buried beneath the skin surface.
LPS Resection
The muscle can be resected either through the conjunctival approach (Blaskovics operation) or skin approach (Everbusch’s operation).
The steps involved in Blaskovics operation are as follows:
•Upper lid is doubly everted over Desmarre lid retractor.
•An incision is made at the upper border of tarsal plate through conjunctiva.
•Conjunctiva is reflected by sutures.
•Levator aponeurosis is identified and undermined with scissors.
•A ptosis clamp is inserted and LPS aponeurosis is freed from its attachments.
•1 to 2 mm of upper border of tarsal plate is excised.
•The amount of LPS to be resected is measured with a caliper and three double-armed 5–0 vicryl sutures are passed through the aponeurosis.
•The aponeurosis is cut distal to the sutures.
•The cut end is anchored to the upper border of tarsal plate.
•The sutures are merged through the muscle and skin in a line to make the lid fold.
•The conjunctiva is closed with continuous suture.
Since the sutures used are tied exteriorly, they can be removed early in the event of overcorrection. For this reason, it should be employed in most reoperations for undercorrection of congenital ptosis, in which overcorrection is a true hazard.
Everbusch’s operation (skin approach levator resection).
Advantages:
•It should be used when ptosis is congenital and severe. LPS is better exposed through skin approach and is recommended in patients who require larger LPS resections.
•The suture can be fixed somewhat lower on the tarsus. The resulting advancement enhances the elevating effect of resection appreciably.
The steps involved in Everbusch’s operation are as follows:
•A skin incision is made in the future lid fold.
•The dissection is carried under the orbicularis muscle to expose the orbital septum.
•A vertical incision is made in the orbital septum and the levator aponeurosis is exposed.
•Conjunctiva is separated from the Müller muscle and aponeurosis.
•A ptosis clamp is placed, grasping the aponeurosis.
•The amount of LPS aponeurosis to be resected is measured with a caliper, and three double-armed sutures are passed through the aponeurosis.
•The aponeurosis is cut distal to the sutures and anchored to the upper tarsal border. The sutures are tied.
Levator Advancement
Procedure: The steps involved in levator advancement are as follows:
•A skin incision is made along the lid fold.
•The levator aponeurosis is identified and detached.
•The lower edge of aponeurosis is attached to the anterior surface of tarsus.
•The skin incision is closed.
Levator Aponeurosis Tuck (Tucking/Levator Plication)
In this procedure, the levator, instead of being resected, is double-breasted over itself. It is done in mild to moderate ptosis with good or fair levator function. In severe ptosis, the results are poor as compared with LPS resection (Fig. 26.7).
Fig. 26.7 Aponeurosis tuck.
•The levator aponeurosis is approached by a lid crease incision.
•Three mattress sutures are placed. Upper bites are placed in the aponeurosis and the lower bites engage the tarsus.
•Sutures are tied, and the skin incision is closed.
Frontalis (Brow) Suspension
Indication: It is used for severe ptosis (>4 mm) with very poor levator function (<4 mm).
Procedure: The steps involved in frontalis suspension are as follows: The tarsal plate is suspended from the frontalis muscle with a sling consisting of autologous fascia lata or nonabsorbable sutures (prolene). The best material available is autologous fascia lata. For most brow suspension procedures, a strip, which is 6 to 7 cm in length, should be sufficient.
Two incisions at the lid margin are considered appropriate for young children as it prevents postoperative bending of the eyelid. Three incisions are made approximately 4 mm from the lid margin. Two incisions are made 5 mm above the medial and lateral portions of the brow. The third brow incision is made midway between the two brow incisions, 15 to 16 mm above them. One fascia lata strip or suture (supramid or prolene) is passed through the openings in the lid and then upward, emerging with two ends in each of the openings above the brow. The end of each strip is carried beneath the brow to the central brow incision, and a ligature is fixed deep in the upper brow incision. The brow incisions are closed and the lid incisions are not sutured. The frost suture is placed in the lower lid and taped to the forehead for corneal protection (Fig. 26.8).
Fig. 26.8 Frontalis (brow) suspension.
Choice of Operation
Congenital Ptosis
Table 26.2 highlights the choice of cooperation for the treatment of congenital ptosis.
Table 26.2 Choice of operation in congenital ptosis | ||
Degree | LPS function | Operative procedure |
Mild (1.5–2 mm) | Always good LPS function | Fasanella-Servat operation or Small (10–13 mm) LPS resection |
Moderate (3 mm) LPS function is good or fair. In moderate ptosis LPS function of <5 mm is extremely rare. | If LPS function is good (≥8 mm) If LPS function is fair (5–7 mm) If LPS function of <5 mm is encountered | Moderate (14–17 mm) LPS resection. Larger (18–22 mm) LPS resection. Maximum (≥23 mm) LPS resection by skin approach should be done. |
Severe (≥4 mm) Sometimes, this type of ptosis has a fair LPS function but usually LPS function is poor. | If LPS function is fair (5–7 mm) If, as is usual, LPS function is poor (≤4 mm) | Maximum (≥23 mm) LPS resection by skin approach should be done. The levator muscles should be well advanced on the anterior surfaces of the tarsi. Bilateral fascia lata brow suspension is done if the ptosis is bilateral. If ptosis is unilateral, a maximum (≥23 mm) LPS resection by skin approach should be done. The levator muscle should be well advanced on the anterior surfaces of the tarsus. The alternative that has usually been done is a unilateral brow suspension procedure. |
Abbreviation: LPS, levator palpebrae superioris. | ||
Acquired Ptosis
In acquired ptosis, laterality, severity, LPS function, and the cause of ptosis is taken into account.
Neurogenic ptosis
In all neurogenic ptosis, the patient should be reviewed periodically for any spontaneous recovery and stabilization of ptosis.
•In complete III nerve paralysis, surgery should not be done, since raising the eyelid produces a troublesome diplopia due to strabismus.
•Neurogenic ptosis due to Horner’s syndrome is ideally suited for the Fasanella–Servat operation, since LPS function is normal in these cases and lid motility remains unimpaired.
Myogenic Ptosis
In myogenic ptosis, treatment of the primary disorder should be undertaken first, followed by crutch spectacles to help lift the lid.
Aponeurotic Ptosis
It is due to weakness or disinsertion of the LPS aponeurosis from the anterior tarsal surface. Treatment of aponeurotic ptosis consists of reinsertion of levator aponeurosis into the anterior tarsal surface with appropriate resection of LPS.
Mechanical ptosis
In mechanical ptosis, the treatment is that of the cause.
▃Lacrimal Sac Surgery
■Dacryocystorhinostomy (DCR)
DCR involves anastomosis between lacrimal sac and nasal mucosa of middle nasal meatus to bypass the obstructed nasolacrimal duct (NLD). It is indicated for the obstruction beyond the opening of the canaliculus. DCR can be performed by:
•Conventional external DCR.
•Endonasal DCR.
•Transcanalicular laser DCR.
Endonasal DCR is cosmetically superior to external DCR. Differentiating features of external and endoscopic DCR are listed in Table 26.3.
Table 26.3 Difference between external and endoscopic DCR | ||
Criteria | External DCR | Endoscopic DCR |
Cutaneous scarring | Yes | No |
Bleeding | More | Bloodless surgery |
Time consumption | More | Less |
Skill requirement | No need for endoscopic skill Easy to perform | Requires skill Better visualization |
Success rate | More | Less |
Cost factors | Cheap | Expensive |
Morbidity | More post-operative morbidity | No post-operative morbidity |
Abbreviation: DCR, dacryocystorhinostomy. | ||
Conventional External DCR
Indications
DCR is indicated in chronic dacryocystitis and mucocele of the lacrimal sac.
Preoperative Requisites
The following information needs to be in hand before going in for conventional external DCR:
•Hemoglobin levels.
•Bleeding and clotting times.
•Blood pressure measurement.
•Random blood sugars.
•ENT evaluation.
•Additional general anesthesia investigations when required.
Procedure
•Nasal packing: It is done to keep the mucosa taut and reduce bleeding. Instill 4% topical lignocaine in the ipsilateral nostril, followed by insertion of nasal pack (roller gauze soaked in 2% lignocaine-adrenaline jelly) superiorly then posteriorly and inferiorly with the help of nasal packing forceps.
•Anesthesia: It may be general or local anesthesia (2% Lignocaine with 0.5% Bupivacaine with or without adrenaline) by infiltration. It blocks infratrochlear nerve first which supplies the lacrimal apparatus.
•Skin incision: A curved incision along lacrimal crest is made. Angular vessels should be avoided. Orbicularis is split and retracted with skin by a lacrimal retractor (Fig. 26.9).
•Exposure of medial palpebral ligament (MPL) and anterior lacrimal crest: MPL is exposed and disinserted at the anterior lacrimal crest. It opens up the periosteum which is now separated along the entire length of the incision with periosteum elevator. Periosteum is elevated posteriorly till the lamina papyracea, which is a thin bone.
•Exposure of nasal mucosa: Osteotomy (12 × 10 mm) is done with a bone punch, removing the lacrimal crest and lamina papyracea to expose the nasal mucosa.
•Preparation of flaps of sac: A probe is introduced into the sac through the lower canaliculus. A vertical incision is made in the medial wall of the lacrimal sac and converted into H-shape to prepare anterior and posterior flaps.
•Preparation of nasal mucosal flaps: The two flaps of nasal mucosa are made by an H-shaped incision with the horizontal incision in the middle.
•Suturing of flaps: The posterior flaps of the sac and nasal mucosa are sutured. The anterior nasal flap is now sutured to the anterior sac flap with 6–0 vicryl sutures.
•Closure: The medial palpebral ligament is reposited and sutured with periosteum. The orbicularis oculi muscle is also sutured with 6–0 vicryl and the skin incision is closed with 6–0 silk suture.
•Postoperative care: Complete bed rest for 24 hours:
◊Patients are asked to avoid blowing of nose.
◊Oral antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs) are given routinely for 5 days.
◊Nasal pack is removed after 24 hours.
◊Local treatment includes otrivin-P nasal drops twice daily, antibiotic ointment on the wound twice daily, and antibiotic with steroid eye drop four times daily.
◊The syringing should be done on third day postoperatively.
◊Sutures are removed after 1 week.
Fig. 26.9 (a, b) Conventional DCR. Abbreviation: DCR, dacryocystorhinostomy.
Causes of Failure
•Unrecognized common canalicular obstruction.
•Scarring.
•“Sump syndrome,” in which the surgical opening in the lacrimal bone is too small and too high. Thus, there is collection of secretions in lacrimal sac below the level of inferior margin of the ostium, which is unable to gain access to the nasal cavity.
Complications
Bleeding may occur from the vascular nasal mucosa postoperatively. Postoperative infection is rarely seen.
Endoscopic Transnasal DCR
It is indicated in patients of chronic dacryocystitis with associated nasal disorder.
Procedure
A slender light pipe is passed through the lacrimal puncta and canaliculi into the lacrimal sac and viewed from within the nasal cavity with an endoscope. The remainder of the procedure is performed via the nose:
•The mucosa over the frontal process of the maxilla is stripped.
•A part of the nasal process of the maxilla is removed.
•The lacrimal bone is broken off piecemeal.
•The lacrimal sac is opened.
•Silicone tubes are passed through the upper and lower puncta, pulled out through the ostium, and tied within the nose.
Endolaser DCR
It is a relatively rapid procedure and can be performed under local anesthesia. It is therefore particularly suitable for elderly patients. It is performed with a Holmium: YAG laser which is used to ablate the mucosa and thin lacrimal bone. It has a lower success rate (70%) due to smaller bony opening (4–6 mm) in comparison to conventional DCR.
Dacryocystectomy
It is the removal of lacrimal sac. Postoperative epiphora is common.
Indications
It is indicated in granulomatous lesions of sac, tumors of the lacrimal sac and chronic fibrotic dacryocystitis.
Procedure
•The initial steps are similar to DCR in order to expose the lacrimal sac.
•After exposing the sac, it is separated from surrounding structures by blunt dissection.
•Lacrimal sac is removed by cutting its connections with lacrimal canaliculi.
•It is then held with artery forceps, twisted 3 to 4 times, and severed from the NLD.
•The incision is closed by sutures similar to DCR.
Conjunctivodacryocystorhinostomy
Indication
It is helpful when both the canaliculi are blocked with or without the NLD obstruction. When there is <7 mm of patent canaliculus, it is difficult to anastomose the remaining canaliculi to lacrimal sac, that is, canaliculo dacryocystorhinostomy (CDCR) is impossible.
Procedure
In this procedure, a free communication is established between the lacrimal lake at the inner canthus and middle meatus of the nose using Lester Jones tube. The initial steps are identical to those of DCR.
▃Strabismus (Squint) Surgery
■Aims of Strabismus Surgery
Strabismus surgery is done to correct misalignment, restore binocular single vision, and reduce abnormal head posture.
The surgical correction of childhood strabismus should be undertaken after correction of any significant refractive error and/or treatment of amblyopia. Treatment of amblyopia includes patching or penalization (with Atropine 1%) in the normal eye and orthoptic exercises to stimulate the amblyopic eye. Once the visual acuity improves to its maximum, the residual deviation is treated surgically. In long-standing cases, amblyopia develops and the strabismus surgery is done for cosmetic purpose.
■Procedures
The three main types of procedure are:
•Weakening procedures.
•Strengthening procedures.
•Transposition/repositioning procedures.
Weakening Procedures
These include recession, disinsertion (or myectomy) or posterior fixation suture.
Recession
In recession, the muscle is disinserted and reattached behind its insertion, which weakens the action of muscle. It may be done on rectus muscles or inferior oblique muscle.
Recession can be performed on any muscle except the superior oblique, as it is the most important vertically acting muscle in the position of depressed convergence and essential to avoid weakening the superior oblique.
Recession of Horizontal Rectus Muscles
Recession of medial rectus (MR) muscles should not exceed 5 mm. Larger recessions are likely to disturb the balance between the opposing muscle forces; the unopposed lateral rectus (LR) pulls the eye toward abduction and may develop discomfort during reading. However, if both MR and LR are recessed, the balance between the opposing muscle forces remains undisturbed. LR muscles are recessed as much as 10 mm behind its insertion. Larger recessions of LR muscles are usually necessary. Even if a 10 mm recession puts the insertion behind the anatomic equator of the eye, the LR muscle will remain in contact with the globe behind the equator and thus continue to exert rotational force on contraction.
Procedure:
•A vertical incision in conjunctiva is made in front of the muscle insertion.
•Muscle is exposed covered by Tenon’s capsule.
•Slit incisions are made in Tenon’s capsule along the upper and lower borders of the muscle. The part of the capsule covering the muscle should be preserved.
•The squint hook is passed under the muscle just behind the insertion.
•Two absorbable sutures are passed through the upper and lower edges of the tendon 2 mm behind its insertion.
•The desired amount of recession is measured and marked on the sclera with calipers.
•The tendon is disinserted from the sclera.
•The detached end of the tendon is sutured to the sclera at the points already marked as the new insertion. The sutures are passed through the superficial layers of the sclera at right angles to the long axis of the muscle.
•The sutures are tied and the conjunctival incision is closed (Fig. 26.10).
Fig. 26.10 Recession of horizontal rectus muscles.
Recession of Vertical Rectus Muscles
Recession of vertical recti includes visualization and preservation of the neighboring oblique muscles before the procedure. The frenulum between superior rectus and superior oblique, and common facial attachments between inferior rectus and inferior oblique muscles are visualized and incised to avoid undesired effects on oblique muscle functions.
Recession of Inferior Oblique Muscle
•An inferotemporal fornix incision is made and the muscle belly is exposed.
•A squint hook is passed behind the posterior border of the muscle.
•An absorbable suture is passed through the muscle at its insertion.
•The muscle is disinserted.
•The muscle is reattached to the sclera 3 mm posterior and temporal (lateral) to the temporal edge of the inferior rectus insertion.
Weakening of Superior Oblique Muscle
Tenotomy or tenectomy procedures can be performed for superior oblique tendon to weaken the action of superior oblique muscle.
Procedure
•The incision is made through conjunctiva and Tenon’s capsule between the MR and superior rectus muscles, 4 to 5 mm behind the limbus.
•A muscle hook is introduced under the superior rectus muscle, the eye is turned downward and outward, and Tenon’s capsule is retracted superiorly.
•The superior oblique is visualized 8 mm posterior to the nasal border of superior rectus insertion.
•The intermuscular septum between superior rectus and superior oblique muscle is incised and the superior oblique is isolated.
•The tendon of superior oblique is visualized, and the tendon sheath is incised.
•The tendon is pulled from the sheath at this point and cut (tenotomy).
•To remove a piece of tendon, including its sheath (tenectomy), the tendon is spread between two hemostats and clamped, after which a section is removed with scissors.
•The wound is now closed.
Disinsertion (or Myectomy)
In disinsertion, a muscle is detached from its insertion but not reattached. Therefore, the technique is identical to recession, except that the muscle is not sutured. It is commonly used to weaken an overacting inferior oblique muscle.
Posterior Fixation Suture (Faden Operation)
The word Faden is German for thread or suture and is derived from the use of sutures to attach the muscle to the sclera. This operation is also designated posterior fixation suture or retropexy of an extraocular muscle (EOM). In this procedure, the muscle belly is sutured (with a nonabsorbable suture) to the sclera posteriorly, approximately 12 mm behind its insertion. Thus, the pull of the muscle in its field of action is decreased with no effect in the primary position. The Faden procedure may be used:
•On MR in convergence excess esotropia (to reduce convergence).
•On superior rectus in dissociated vertical deviation (DVD).
Strengthening Procedures
These include resection, tucking of a muscle or tendon, and advancement of the muscle.
Resection
It shortens the length of muscle and enhance its effective pull. Excessive resection may mechanically restrict movement of the globe in the opposite direction and, therefore, must be avoided. It is suitable only for a rectus muscle.
The maximum amount of resection for MR is 7 to 8 mm and for LR is 10 mm. When more correction is desired, the muscle is advanced toward the cornea.
Many technical problems occur with the resection of inferior oblique muscle. Therefore, weakening the action of superior rectus muscle in the fellow eye or tenotomy of ipsilateral superior oblique muscle (in case of inferior oblique paralysis) must be preferred.
Procedure
•A vertical incision in conjunctiva is made in front of the muscle insertion.
•Muscle exposed is covered by Tenon’s capsule.
•Slit incisions are made in Tenon’s capsule along the upper and lower borders of the muscle. The part of the capsule covering the muscle should be preserved.
•The squint hook is passed under the muscle just behind the insertion.
•The length of muscle and tendon for resection is determined and marked.
•Two absorbable sutures are passed through upper and lower edges of the muscle behind the mark.
•The muscle is held in a muscle clamp and cut at the insertion.
•The needles of suture are passed through the original insertion and the muscle anterior to the suture is excised.
•The muscle is drawn forward, sutures are tied, and conjunctival incision is closed (Fig. 26.11).
Fig. 26.11 Resection of a muscle.
For resection of vertical recti muscles, the functions of neighboring oblique muscles must be preserved before the procedure is performed and the fascial attachments must be visualized and removed.
•Recession of the MR is more effective than recession of the LR.
•Resection of the LR has a relatively greater effect than of the MR.
Tucking of a Muscle
Tucking (pleating) of the tendon of the superior oblique for its underaction is preferred to resection. Thus, it is usually confined to enhance the action of superior oblique muscle.
Procedure
•An incision is made through the conjunctiva and Tenon’s capsule horizontally from the temporal edge of superior rectus.
•A muscle hook is placed under the superior rectus insertion, and the eye is rotated further downward with the hook.
•The temporal border of superior rectus is lifted with the hook, and the superior oblique tendon is exposed with a sweeping motion of a second hook.
•A tendon tucker is introduced beneath the superior oblique tendon. The folded tendon is drawn into the tucker.
•After achieving a desired amount of tucking (usually between 6 and 12 mm), the blades of the instrument are closed.
•Forced ductions are now performed to determine the degree of restriction when elevating the adducted eye. Mild restriction is desirable and should result in a good effect from the operation. Severe restriction necessitates undoing the tuck and tucking a lesser portion of the tendon.
•The wound is then closed with one interrupted stitch of 7–0 vicryl.
Advancement of the Muscle
A previously recessed rectus muscle can be advanced nearer to the limbus to enhance its action.
Transposition/Repositioning Procedures
It is the repositioning of one or more EOMs to substitute the action of a deficient muscle (Fig. 26.12).
Fig. 26.12 Actions of EOMs. Abbreviation: EOM, extraocular muscle; IO, inferior oblique; IR, inferior rectus; LR, lateral rectus; SO, superior oblique; SR, superior rectus.
Indications
It is indicated in acquired VIth cranial nerve (CN) nerve palsy, resulting in LR weakness, A–V patterns, Duane syndrome, and monocular elevation deficit.
Procedures
•Vertical rectus muscles in the treatment of horizontal strabismus: Transposition of strips of the superior rectus and inferior rectus muscles are used in the correction of total LR and MR paralyses. It is also necessary to recess the ipsilateral opponent of the paralyzed muscle. For esotropia (total LR palsy), temporal transposition of vertical rectus muscles is recommended. The superior rectus and inferior rectus are split along their length and join to the adjacent halves of the similarly split LR. A suture ties the half muscles together at the level of equator. Similarly, the vertical muscles are transposed nasally for exotropia (total MR palsy).
•Horizontal rectus muscles in the treatment of vertical strabismus: The horizontal rectus muscles (MR and LR) are vertically transposed in the treatment of vertical strabismus. To lower an eye in hypertropia, the insertions are lowered and to raise an eye in hypertropia, they are raised.
A muscle transposition should never be performed unless passive movement of the eye is unrestricted in the paretic field of gaze.
•Horizontal and vertical rectus muscles in the treatment of A–V patterns: The A-V patterns of movement are primarily due to altered oblique muscle actions in most cases. The horizontal deviation is measured in up and down gaze. The surgical procedure for horizontal strabismus is combined with weakening or strengthening procedures on the oblique muscles in most patients with A and V patterns.
■Choice of Surgical Procedure
For Esotropia
As a general rule, surgical treatment of unilateral esotropia must be undertaken early and as soon as the child cooperates in postoperative orthoptic treatment (usually 4–5 years of age). It may be undertaken as early as 18 months of age for better binocular vision. If surgery is undertaken late (≥10 years of age), it will result in permanent amblyopia, and binocular vision fails to establish.
Surgery includes weakening of MR muscle (recession) and/or strengthening of LR muscle (resection) (Table 26.4).
Table 26.4 Surgical procedures for different types of esotropia | |
Type of esotropia | Surgical procedure of choice |
•Uniocular esotropia | Both MR and LR muscles of same eye are operated on (MR recession and LR resection). In the higher degree of esotropia, one or two of the muscles of the other eye may also require surgery. |
•Alternating comitant esotropia | Recession of both medial rectus (MR) |
•Basic esotropia | MR recession and LR resection are combined on the same eye. |
•Near esotropia (convergence excess) | Bilateral MR recession of 4mm each (when on accommodation esotropia is 25 degrees). For esotropia of high degree, it is preferable to do a MR recession and a LR resection on one eye and later a recession of MR of the other eye if necessary, for this gives a better result than bilateral MR recession and later LR resection. |
•Distance esotropia (divergence insufficiency) | Bilateral LR resection |
•Cross-fixation pattern | Bilateral medial rectus (MR) recession and lateral rectus (LR) resection of non-dominant eye. |
For Exotropia
The surgical procedure includes weakening of LR muscle (recession) and strengthening of MR muscle (resection) (Table 26.5). The exodeviation is rarely completely eliminated by a surgery; therefore, slight overcorrection is indicated for these eyes which have a strong tendency to revert to exotropia.
Table 26.5 Surgical procedures for different types of exotropia | |
Type of exotropia | Surgical procedure of choice |
•Early-onset exotropia •Distance exotropia (divergence excess) •Basic exotropia (Non-specific exotropia) •Near exotropia (convergence insufficiency) | •LR recession and MR resection •Bilateral LR recession •Unilateral LR recession and MR resection •Unilateral LR recession and MR resection |
Abbreviations: LR, lateral rectus; MR, medial rectus. | |
For A–V Pattern
There is no unanimity concerning the pathophysiology of A and V patterns and several schools of thoughts have evolved. According to few, A or V patterns may be caused by primary anomalies in the function of the vertical rectus muscles; while, according to others, overaction and underaction of the oblique muscles are frequently associated with A or V patterns. In general, oblique muscles are more significant than superior rectus and inferior rectus muscles in the production of A–V patterns. Therefore, weakening or strengthening of oblique muscles influence the correction of A–V patterns.
“A”–pattern develops following paresis or underaction of inferior muscles (inferior oblique and inferior rectus muscles).
“V”–pattern develops following paresis or underaction of superior muscles (superior oblique and superior rectus muscles). Therefore, overaction of inferior oblique muscle or weakness of superior oblique muscle results in “V” pattern, and overaction of superior oblique muscle or weakness of inferior oblique muscle results in “A” pattern.
•When dysfunction of oblique muscles is evident: Inferior oblique muscle is an abductor and elevator, while superior oblique muscle is an abductor and depressor. Weakness of superior oblique muscle leads to absence of abduction in depression. Overaction of inferior oblique muscle leads to more divergent position in upgaze. Both of these result in “V” pattern. Therefore, “V” esotropia/“V” exotropia with oblique muscle dysfunction (overaction of inferior oblique muscle) is treated by bilateral weakening of inferior oblique muscle. Weakness of inferior oblique muscle leads to absence of abduction in upgaze, and overaction of superior oblique muscle leads to more divergent position in downgaze. Both of these result in “A” pattern. Hence, “A” esotropia/“A” exotropia with oblique muscle dysfunction (overaction of superior oblique muscle) is treated by bilateral weakening of superior oblique muscle, that is, superior oblique posterior tenotomy.
•When dysfunction of oblique muscles is not evident: SR muscle is an adductor and elevator. If superior rectus underacts, in upgaze, adduction is diminished, and the eyes will diverge because of secondary overaction of inferior oblique muscle. In downgaze, secondary overaction of inferior rectus muscle results in increased adduction of eyes. Both of these result in “V” pattern.
Surgery on horizontal rectus muscles alone may effectively reduce vertical incomitance and both MR muscles are moved toward the closed end. Both LR muscles are moved toward the open end (A or V pattern). The following points are needed to be considered while treating A or V patterns:
•“A” esotropia without oblique muscle dysfunction is treated by bilateral MR recession with upward transposition of insertion.
•“A” exotropia without oblique muscle dysfunction is treated by bilateral LR recession with downward transposition of insertion.
•“V” esotropia without oblique muscle dysfunction is treated by bilateral MR recession with downward transposition of insertion.
•“V” exotropia without oblique muscle dysfunction is treated by bilateral LR recession with upward transposition of insertion.
For Paralytic Strabismus
In long-standing paralysis, the following changes takes place:
•The contracture of ipsilateral antagonist muscle.
•Overaction of contralateral synergist.
•Inhibitional palsy of contralateral antagonists.
For example, in case of left LR palsy: Contracture of left MR, overaction of right MR muscle, and inhibitional palsy of right LR muscle are encountered.
In paralytic strabismus, the treatment with prisms is rarely of much use due to variation in the amount of deviation in the different positions of eyes. Therefore, surgery is done when the deviation has become stabilized.
A unilateral EOM palsy may be treated by one or several of the operations listed in Table 26.6.
Table 26.6 Operations on Extraocular muscles for long standing paralysis | |
Changes in long standing paralysis | Operations on extraocular muscle |
•The contracture of ipsilateral antagonist muscle. •Over action of contralateral synergist. •Inhibitional palsy of contralateral antagonists. | •Recession of the overacting and subsequently contracted direct (ipsilateral) antagonist. •Recession of the overacting contralateral synergist. •Resection of the contralateral antagonist, particularly if it is affected by disuse palsy. •Resection of the weak and stretched palsied muscle. |
Often, it seems necessary to plan the surgical treatment in more than one stage to assess the effects of each.
■Complications of Squint Surgery
Complications following strabismus surgery include:
•Anterior segment ischemia.
•Undercorrection or overcorrection.
•Postoperative diplopia.
•Scleral perforation.
•Postoperative infections.
•Foreign body granuloma.
•Conjunctival inclusion cysts.
•Slipped or lost muscle.
•Suture reactions.
•Corneal dellen.
Particular caution is required in patients with thin sclera (such as in myopes or having a history of scleritis). The surgeon must be aware of the location of vortex vein, especially during oblique muscle surgery.
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