Strabismus management in India encompasses a wide range of surgical and nonsurgical approaches. Numerous studies from our country and around the world have significantly influenced our current management of strabismus. Although a variety of options are available to us, the optimal management strategy must be tailored to individual cases. The goals of strabismus management have broadened, with emphasis now placed not only on achieving good visual acuity in both eyes but also on restoring optimal binocular function. Occlusion therapy continues to be the gold standard for amblyopia management. Refractive correction, along with amblyopia therapy, remains the cornerstone of management; however, sequential rather than simultaneous treatment was found to be more beneficial for improvement in stereopsis.1 To offset the challenges of traditional patching treatment, newer technologies—such as liquid crystal occlusion glasses—are being evaluated.2 Classical teaching is to treat amblyopia before planning surgical intervention; however, in acquired esotropia, comparable success rates have been reported regardless of whether amblyopia management is initiated before or after strabismus surgery. Therefore, proceeding with surgery is generally reasonable in such cases, even when amblyopia persists, with amblyopia therapy continued postoperatively.3 Nevertheless, growing evidence suggests that binocular dysfunction also plays a significant role in amblyopia. Dichoptic stimulation and dichoptic contrast manipulation are being explored in various modalities to enable simultaneous use of both eyes and improve binocular visual function Fig. 1.4 A low-cost and effective therapy in the form of television video games, along with occlusion, may be considered favorable for visual development in amblyopic children.5Figure 1: Clinical photograph depicting dichoptic exercise while playing a mobile game to treat unilateral amblyopiaAnother challenge is treating patients with amblyopia who have eccentric fixation. A recent study conducted at our center evaluated the role of inverse occlusion in the management of amblyopia with eccentric fixation. Our findings indicate that this approach can effectively improve central fixation in patients with amblyopia, demonstrating better outcomes compared to conventional methods.6 Investigative modalities in strabismus have traditionally been limited as the diagnosis is primarily clinical. However, magnetic resonance imaging (MRI), anterior segment optical coherence tomography (AS-OCT), and ultrasound biomicroscopy (UBM) have proven useful in planning strabismus surgery. Visualization of static and dynamic configuration of the extraocular muscles, along with their pulleys, can be obtained on MRI scans. Paralytic cases can show atrophy of the affected muscle. Sagging eye and heavy eye syndrome are characterized by displacement of the LR-SR connective tissue band, which is easily evident on MRI.7 Recent imaging studies in patients with Duane retraction syndrome (DRS) show different characteristic appearances on MRI based on the type of DRS. Type 1 DRS was associated with the absence of the abducens nerve, hypertrophy of the oculomotor nerve, reduced lateral rectus muscle volume, and a thicker medial rectus muscle on the affected side.8 Genetic considerations in strabismus include the substantial heritability of esotropia in twins,9 polymorphism in the WRB gene associated with all strabismus subtypes, and divergent strabismus, whereas polymorphism in TSPAN10 was found to be associated with all subtypes, convergent and divergent strabismus.10 Under preoperative planning, the Prism Adaptation Test (PAT) has proven particularly useful in cases of intermittent divergent squint. It is more effective than monocular occlusion in determining the maximum angle of deviation before surgery.11 Usefulness of PAT in acute acquired comitant esotropia (AACE) has likewise been established, Surgical outcomes in AACE are more favorable when surgical planning is guided by preoperative PAT compared to surgery performed without it. Patients undergoing PAT-based planning demonstrate better postoperative motor alignment, with fewer instances of under- or overcorrection, as well as superior sensory outcomes, including greater improvement in stereopsis Fig. 2.12Figure 2: Clinical photograph showing prism adaptation test (PAT) being used in a case of AACE for preoperative planningManagement of strabismus has evolved with the introduction of several innovative approaches. While the role of botulinum toxin is well established, the use of the anesthetic agent bupivacaine has gained attention for improving ocular alignment through an opposite mechanism. Bupivacaine is injected directly into the extraocular muscle, leading to muscle fiber contraction and subsequent strengthening, thereby enhancing alignment.13 Studies have demonstrated its promising effects in small-angle horizontal strabismus, although outcomes have been less favorable in long-standing cranial nerve palsies.13 Monocular elevation deficiency (MED) is traditionally managed by horizontal recti transposition. However, in cases of MED having horizontal deviation, a modified Knapp’s procedure can be performed by transposition of the superior half of equally divided (up to 15 mm) medial and lateral recti for vertical deviation and the inferior half after suitable recession or resection for horizontal deviation. We recommend a modified Knapp’s procedure for MED with horizontal deviation ranging up to 20 PD.14 A recent study conducted at our center was the first study to assess the role of Modified Nishida’s procedure in a case series of MED. We found that Modified Nishida’s procedure improves vertical deviation and elevation deficit significantly in cases of MED. We recommend Nishida’s procedure in cases of MED with a vertical deviation less than 30 PD and FDT negative for IR.15 Esotropic DRS can be managed by full tendon or half tendon vertical rectus transposition (VRT) with lateral fixation suture, which improves abduction.16 Another option is superior rectus transposition (SRT) with MR recession which may induce torsion, but the risks of torsional diplopia remain low.17 VRT toward MR can be done in DRS with mild globe retraction and residual exotropia, after LR recession.18 A new approach to managing complete third nerve palsy has come to light in which medial and lateral rectus reunion can be done. The medial rectus muscle is sutured as posteriorly as possible from its insertion and subsequently cut. Its distal stump was divided into two halves, and each half is anastomosed with the corresponding superior and inferior halves of the lateral rectus muscle. Finally, the proximal portion of the medial rectus muscle was reattached to its original insertion.19 This technique helps in correcting large exodeviations and can be used as a reoperation procedure. A study conducted at our center on patients of complete third nerve palsy, who underwent MR-LR reunion, showed that there was a significant improvement in the horizontal deviation; however, there was limited vertical correction (Unpublished Study). The cosmetic aspect of strabismus surgery has gained increasing attention in recent years, with surgical approaches evolving from traditional limbal-based incisions to minimally invasive strabismus surgery (MISS). Postoperative redness, swelling, scarring, and the risk of infection at the incision site have underscored the importance of minimizing incision size to reduce complications. MISS employs smaller incisions with less tissue disruption while achieving comparable surgical outcomes. In the MISS technique, two small keyhole radial cuts are made superior and inferior to the muscle insertion margin. The keyhole incision length is approximately 1 mm less than the amount of muscle recessed or resected. Studies utilizing MISS for horizontal rectus muscle surgery have demonstrated superior outcomes compared to conventional techniques, particularly regarding postoperative pain, swelling, and conjunctival congestion.20–22 Recently, MISS has also been successfully applied to inferior oblique recession, with comparative studies reporting promising results.23 Furthermore, the concept of Half-MISS, involving a single paramuscular incision, has been introduced as a refinement of the technique Fig. 3.24Figure 3: Intraoperative photograph depicting hemi-minimally invasive strabismus surgery (MISS) being done for rectus muscle recessionIn conclusion, while notable advancements continue to enhance our understanding and management of amblyopia and strabismus, it is imperative that these innovations are integrated with fundamental clinical principles to deliver comprehensive and optimal patient care. The way forward lies in integrating rigorous evidence-based practice with the latest research and technological innovations to achieve optimal patient care. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.About the authorProf. Subhash Dadeya Dr. (Prof). Subhash did his MBBS from Medical College Rohtak in 1991. He did his M.D. (Ophthalmology) from Dr. R. P. Center A.I.I.M.S in 1995. He did his Senior Residency from Guru Nanak Eye Center, Maulana Azad Medical College Delhi he is active member of Delhi Ophthalmological society. He was executive member of DOS (2008-10) Library Officer of Delhi Ophthalmological Society (2011-12). He has been Secretary 2017 to 2019 and President DOS 2020 to 2021. He is active member of AIOS & has written CME series on amblyopia. He is executive member of DMA also. He has more than 100 publications to his credit in various regional, national and international journals. He has attended various conferences at regional, national and international level (Asia pacific academy of ophthalmology at Bangkok, Singapore Malaysia, Indonesia& China & South Korea & World Congress of ophthalmology at Canada, the Netherlands, Sydney Hongkong & UAE & American academy of ophthalmology & European society of cataract and refractive surgery conference at Portugal & ROP conference at Lithuania. He has been invited guest speaker at various regional, national and international conferences in various capacities. He was secretary during his MBBS course and was President Resident Doctors Association at AIIMS & President and Secretary Faculty association of MAMC & Associated Hospitals.
Subhash Dadeya (Thu,) studied this question.