Patterns of oculomotor nerve distribution to the levator palpebrae superioris muscle, and correlation to temporary ptosis after blepharoplasty

Blepharoptosis Repair: External Versus Posterior Approach Surgery: Why I Select One over the Other

Ptosis surgery is performed via an anterior/external or posterior/internal approach, primarily defined by the eyelid elevator muscle surgically addressed: the levator complex anteriorly or Muller muscle posteriorly. Posterior ptosis surgery via Muller muscle conjunctival resection is an excellent first choice for cases of mild to moderate ptosis with good levator function, as it is predictable, provides a reliable cosmetic outcome, requires no patient cooperation during surgery, portends a lower rate of reoperation, and rarely leads to lagophthalmos and/or eyelid retraction postoperatively. External levator resection is preferred in patients with severe ocular surface/cicatricial conjunctival disease, shortened fornices, and lesser levator function.

Anatomical variations of the levator palpebrae superioris, including observations on its innervation and intramuscular nerves' distribution pattern

BACKGROUND

The levator palpebrae superioris muscle (LPS) acts as the upper eyelid's major elevator and retractor and is innervated by the oculomotor nerve. The muscle's paralysis is manifested by ptosis.

MATERIAL AND METHODS

70 orbits were dissected. After removing the orbital roof, the LPS' shape and anatomical variations (i.e., the presence of accessory muscular bands or atypical formation of the muscle) were assessed. To visualize the distribution of the oculomotor nerve's intramuscular sub-branches, the isolated levator palpebrae superioris muscles were stained using Sihler's staining technique.

RESULTS

Several LPS anatomical variations were observed in the specimens examined, in seven of which (7/70; 10%) additional delicate muscular slips arose from the LPS' lateral border and reached the lacrimal gland. Histological examination confirmed the presence of striated skeletal muscle fibers in all those cases. In three other specimens (3/70; 4.28%), supernumerary muscular bands ("tensor trochleae") were found that linked the levator with the superior oblique muscle's trochlea. In the next case, the LPS' origin was double and the muscle was bipartite on its proximal half. In most cases (55/70; 78.6%), muscular branches formed a single bundle that wrapped around the superior rectus muscle's medial border to reach the levator's inferior surface. Intramuscular sub-branches were distributed largely within the proximal two-thirds of the LPS and formed an irregular, tree-like pattern. However, thin sub-branches and small retrograde sub-branches extended as far as the muscle's insertion.

CONCLUSIONS

Plastic surgeons and ophthalmologists should be aware of the levator palpebrae superioris muscle's anatomic variations both in planning and conducting surgeries on the upper eyelid.

Change in Eyelid Position Following Muller's Muscle Conjunctival Resection With a Standard Versus Variable Resection Length

PURPOSE

This study compares the use of a standard 7 mm resection length to a variable 4:1 ratio of resection length to desired elevation nomogram when performing Muller's muscle conjunctival resection surgery.

METHODS

In this cross-sectional case control study, 2 groups were defined. The first underwent Muller's muscle conjunctival resection surgery with a standard 7 mm resection length and the second underwent the same surgery with a variable resection length determined by a 4:1 ratio of resection length to desired elevation nomogram. Groups were matched for age (within 5 years) and sex. Pre- and postoperative photographs were measured digitally. Change in upper marginal reflex distance 1 (MRD1) and final MRD1 were the primary outcome measures. The study was powered to detect a 1 mm difference in MRD1 to a beta error of 0.95.

RESULTS

No significant preoperative differences between the groups were noted. No significant difference in final MRD1 (0.1 mm; p = 0.74) or change in MRD1 (0.2 mm; p = 0.52) was noted. Mean resection length to elevation ratios were 3.9:1 for standard group and 4.3:1 for the variable group (p = 0.54).

CONCLUSION

The authors were not able to detect a significant difference in final MRD1 or change in MRD1 for patients undergoing Muller's muscle conjunctival resection surgery with standard or variable resection lengths. These results tend to argue against a purely mechanical mechanism for Muller's muscle conjunctival resection surgery.

Surgical anatomy of the upper eyelid relating to upper blepharoplasty or blepharoptosis surgery

Eyelid anatomy, including thickness measurements, was examined in numerous age groups. The thickest part of the upper eyelid is just below the eyebrow (1.127±238 µm), and the thinnest near the ciliary margin (320±49 µm). The thickness of skin at 7 mm above the eyelashes was 860±305 µm. The results revealed no significant differences among the age groups. Fast fibers (87.8±3.7%) occupied a significantly larger portion of the orbicularis oculi muscle (OOM) than nonfast fibers (12.2±3.7%). The frontalis muscle passed through and was inserted into the bundles of the OOM on the superior border of the eyebrow at the middle and medial portions of the upper eyelid. Laterally, the frontalis muscle inserted about 0.5 cm below the superior border of the eyebrow. Fast fibers occupied a significantly larger portion of the OOM than did non-fast fibers. The oculomotor nerve ends that extend forward to the distal third of the levator muscle are exposed and vulnerable to local anesthetics and may be numbed during blepharoplasty. The orbital septum consists of 2 layers. The outer layer of loose connective tissue descends to interdigitate with the levator aponeurosis and disperses inferiorly. The inner layer follows the outer layer, then reflects and continues posteriorly with the levator sheath. Widths of the tarsal plate at its lower border, mid-height, and upper border were 21.8±1.8, 16.2±1.6, and 8.3±1.0 mm, respectively. The widths of the levator aponeurosis were 32.0±2.2, 29.2±3.5, and 27.2±3.9 mm, respectively. Below the levator, the "conjoint fascial sheath" (CFS) is attached to the conjunctival fornix. The CFS was 12.2±2.0 mm anteroposterior length and 1.1±0.1 mm thick. The shape was equilateral trapezoid with a longer base anteriorly. The superior palpebral muscle was trapezoidal. The lengths of its sides were 15.58±1.82 and 22.30±5.25 mm, and its height was 13.70±2.74 mm. The width of the levator aponeurosis was approximately 4 mm wider than the superior palpebral muscle.

Blepharoptosis following anterior segment surgery: a new theory for an old problem

Blepharoptosis is a well-known complication following anterior segment surgery. However, its precise aetiology remains elusive. There are currently two widely held views on the pathogenesis of persistent postoperative ptosis, namely the speculum and bridle suture theories. However, both suggested explanations fail to address important anatomical and epidemiological features of this condition. Until now, the majority of published literature describing persistent postoperative ptosis following anterior segment surgery has largely concentrated on dehiscence of the levator aponeurosis as the common mechanism underlying this postoperative complication. However, numerous studies have failed to show any correlation between pre or postoperative skin crease positions in such patients. This review article discusses previously proposed mechanisms responsible for both transient and persistent ptosis. Furthermore, we propose an alternative mechanism for the development of ptosis following anterior segment surgery, namely horizontal stretch of the upper eyelid induced by the use of the speculum. This mechanism also provides a plausible explanation for less commonly described oculoplastic complications, such as lower lid malpositions, following anterior segment surgery. Postoperative ptosis may also act as a paradigm for the development of involutional ptosis in general. In view of the frequency with which ophthalmologists perform anterior segment procedures such as cataract surgery, postoperative ptosis represents a significant concern for all ocular surgeons. Identifying the underlying mechanism is imperative, not only to identify those patients at greatest risk, but also to perhaps provide novel surgical approaches to the management of this complication.

Myoneural Junctions of Extraocular Muscles: Distances from the Orbital Rim and Widths

PURPOSE

To examine both the distances from the orbital rim to the myoneural junctions (MNJs) and the widths of the MNJs of all extraocular muscles.

METHODS

Six orbits of 3 post-mortem cadavers were used. The cadavers (1 female and 2 males) were all Japanese with an average age of 76.3 years. The MNJs of the extraocular muscles and their motor nerves were exposed, and then the distance from the orbital rim to each MNJ and the width of each MNJ were examined.

RESULTS

The distance from the orbital rim to each MNJ in the 6 extraocular muscles ranged from 24.4 to 33.6 mm and the width of each MNJ ranged from 5.0 to 8.5 mm.

CONCLUSIONS

It is essential for orbital surgeons to understand both the distance from the orbital rim to MNJs and the widths of MNJs. This information not only aids the understanding of MNJ damage, but also prevents iatrogenic nerve impairment during orbital surgery.

Efferent and afferent innervations of Mueller's muscle related to involuntary contraction of the levator muscle: important for avoiding injury during eyelid surgery

Because stretching of Mueller's muscle induces involuntary contraction of the levator muscle, we hypothesised that Mueller's muscle functions as a serial kind of muscle spindle of the levator muscle. To confirm the presence and location of efferent and afferent innervations of Mueller's muscle, cadavers' eyelids were microscopically and macroscopically examined, and the resultant findings were physiologically confirmed in patients' eyelids during surgery. Fine neural myelinated structures acting as a mechanoreceptor were found in the proximal Mueller's muscle. Mueller's muscle is doubly innervated by the unmyelinated sympathetic efferent nerve and the myelinated trigeminal proprioceptive afferent nerve, both of which run transversely on the proximal Mueller's muscle to join the lacrimal nerve. Electrical stimulation of the transverse nerve fibres induced involuntary contraction of both the levator muscle as the Hoffmann reflex and Mueller's muscle. Surgical injury to these nerve fibres should be avoided to preserve involuntary contraction of the levator muscle.

Ptosis after cataract surgery

An often over-looked complication of routine cataract surgery is post-operative ptosis. This form of ptosis is often transient, although persistent ptosis may require surgical intervention. The causes include eyelid edema and hematoma, anesthesia myotoxicity, and use of a lid speculum or bridle suture. This review demonstrates that a thorough evaluation of the patient and determination of etiology of post-operative ptosis can help direct the need and timing for intervention.