The dimensions of the palpebral opening increase nearly 50% in width and 20% in height between infancy and adulthood. Configuration varies with a person’s physical and racial characteristics (Figure 1). The size and shape of the palpebral opening should be considered at the outset of extraocular muscle surgery. To start with, a lid speculum appropriate to the size of the palpebral opening should be used (Figure 2). In addition, the surgeon should expect to encounter more difficulty with exposure and suture placement in medial rectus recession and also in patients with a small palpebral fissure or deeply-set eyes. However, measured recession can be accomplished even with the smallest lid fissure opening in an infant beginning at 4 months. Limited working area is not an adequate reason for doing a marginal myotomy as an initial weakening procedure of a medial rectus muscle in congenital esotropia simply because a marginal myotomy is thought to be easier to accomplish than a measured recession. Extraocular muscle surgery in an adult with deeply-set eyes and a smaller than average palpebral opening can be more difficult than such surgery in a 3- or 4-year-old child with a normal or larger than normal palpebral opening (Figure 3, 4). Ptosis, pseudo ptosis, lid retraction, exophthalmos, and enophthalmos all represent lid and palpebral fissure variations that will be encountered and must be both understood and dealt with in the gamut of strabismus management. These issues will be dealt with in more detail during the discussion of clinical examples.