The inferior approach is useful for accessing masses that are visible or palpable in the inferior conjunctival fornix of the lower eyelid, as well as for deeper inferior extraconal or intraconal orbital masses. This approach is also commonly used to approach the orbital floor for fracture repair or decompression.
Visible scarring can be minimized by use of a subciliary blepharoplasty incision in the lower eyelid skin (Fig 7-4). The orbital septum is exposed through the preseptal orbicularis oculi muscle toward the inferior orbital rim. A cutaneous incision in the lower eyelid crease or directly over the inferior orbital rim can provide similar access but may leave a more noticeable scar and result in eyelid retraction. Once the skin–muscle flap is created, the surgeon can open the septum to expose the extraconal surgical space. Alternatively, for access to the inferior subperiosteal space, the periosteum is incised and elevated at the arcus marginalis to expose the orbital floor. Fractures of the orbital floor are reached by the subperiosteal route.
For access to tumors and fractures of the inferior and medial orbit, the transconjunctival approach (Fig 7-5) has largely replaced the transcutaneous approach. An incision is made through the inferior conjunctiva and lower eyelid retractors to reach the extraconal surgical space and the orbital floor. This incision is placed either just below the inferior tarsal border or in the conjunctival fornix, and the conjunctiva is placed on superior traction. When using cutting cautery, care should be taken to avoid causing thermal damage to the conjunctiva and tarsus. Caution should also be taken to avoid injuring the inferior oblique muscle, inferior rectus muscle, and infraorbital neurovascular bundle (see Fig 7-5C). The optical cavity can be enlarged via a lateral canthotomy and inferior cantholysis. Dissection is performed in a similar fashion on a preseptal plane inferiorly toward the orbital rim. The extraconal space can be accessed by incising the orbital septum, and the subperiosteal space can be accessed by incising at the arcus marginalis and elevating the periosteum. Further dissection between the inferior rectus and lateral rectus muscles enables access to the intraconal space.
Figure 7-4 Transcutaneous lower eyelid incision for inferior approach. A well-hidden subciliary incision is made beneath the eyelashes and allows access to the inferior orbit.
(Courtesy of Bobby S. Korn, MD, PhD.)
Figure 7-5 Transconjunctival approach to the inferior orbit. A, Conjunctival incision with or without canthotomy/cantholysis. B, Plane of dissection anterior to orbital septum. C, The conjunctiva is placed on superior traction and the orbital septum is opened to biopsy an inferior extraconal mass (asterisk).
(Parts A and B illustration by Cyndie C. H. Wooley; part C courtesy of M. Reza Vagefi, MD.)
Alternatively, an incision of the bulbar conjunctiva and Tenon capsule allows entry to the sub-Tenon surgical space. This approach is also used to gain access to the intraconal surgical space by retracting or reflecting the inferior rectus muscle from the globe.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.