Biomedical subjects
Publications and source records attributed to M W Preslan.
We treated two siblings, a sister and brother, who had features of septo-optic dysplasia, including bilateral optic nerve hypoplasia, absent septum pellucidum, and partial pituitary insufficiency. Additionally, midline central nervous system abnormalities of the corpus callosum and cerebellum were shown. The familial occurrence of this disorder raises the possibility of autosomal-recessive inheritance.
We studied 44 patients who underwent strabismus surgery with the use of adjustable sutures to determine the occurrence of the oculocardiac reflex during the postoperative adjustment process. We defined the reflex as at least a 10% decrease in the baseline heart rate. Only two patients (4.5%) displayed an oculocardiac reflex during the adjustment. We did not identify any preadjustment factors that would increase the susceptibility to develop the reflex.
We conducted a prospective, randomized, masked comparison of two treatments for the nonaccommodative element in esotropic patients with a high accommodative convergence-accommodation ratio. One group received symmetric medial rectus recessions with posterior fixation sutures; the other received symmetric medial rectus recessions without posterior fixation sutures but augmented according to formula taking into account the near deviation. Previous experience had suggested that our surgical formula based solely on the distance deviation would lead to excessive undercorrections. A higher percentage of the augmented recession group achieved satisfactory alignment and were able to discontinue wearing bifocals postoperatively than the posterior fixation group. The data also showed a trend (though not statistically significant) suggesting that more members of the augmented recession group were able to discontinue wearing spectacles entirely. We concluded that the posterior fixation suture technique is not as effective as the augmented recession technique for the treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio.
The treatment of accommodative esotropia requires a thorough evaluation at first presentation to elucidate all factors involved. The degree of hypermetropia, character of the esodeviation (i.e., intermittent or constant), presence or absence of amblyopia, and the AC/A ratio are all important in the initial management of these patients. In addition, the binocular status can be of prognostic value. Close follow-up is needed to ensure maintenance of binocularity and appropriate early intervention to modify the course before bifixation is lost.
Several different artifacts can induce errors in measurements obtained during strabismus surgery. Fixating the severed rectus muscle stump with forceps during strabismus surgery can result in a temporary anterior displacement of the insertion. This may result in inaccuracies in determining the site to which the muscle is to be recessed. This displacement was quantified in a prospective masked manner and was found in some patients to result in as much as 1 mm of error. It can be prevented by measuring the recession prior to fixating the insertion stump with forceps; however, it cannot always be prevented by measuring from the limbus, which also introduces other artifacts due to geometric principles. An "advancement effect" occurs during a rectus muscle recession due to the mechanics of suture placement in the muscle. It was quantified in a masked manner and found to be approximately .5 mm in most cases. A "V" shaped deformity of the insertion stump may occur immediately adjacent to the forceps. This deformity frequently distorts the insertion by as much as several millimeters.
Several uncontrolled, retrospective studies have suggested that permanent changes in refractive error can be seen following strabismus surgery. We prospectively enrolled 68 patients undergoing strabismus surgery for evaluation of pre- and postoperative cycloplegic refraction. In addition, the adult patients had computerized corneal topography recorded using the Corneal Modeling System, (Computed Anatomy, Inc, New York, NY). Pre- and postoperative refractions were compared using spherical equivalent and meridional equivalent (90- and 180-degree meridian). We found no significant change in the spherical equivalent between the pre- and postoperative measurements. However, a significant increase in the astigmatic power at 180 degrees (meridional equivalent at 180 degrees) was detected in both pediatric and adult patients. We did not observe any qualitative change in the corneal topography pre- and postoperatively. The change in astigmatic power at 180 degrees is equivalent to additional plus-cylinder correction at 90 degrees and was persistent throughout the 4-month postoperative period.