The Prism Adaptation Study (PAS)

2014-08-27 04:00:17 | BioPortfolio


To determine whether the preoperative use of prisms in eyeglasses can improve the outcome of surgery for acquired esotropia, a type of strabismus.

To determine whether patients who respond to prism adaptation by developing a new stable angle of -deviation have a better surgical result than do patients who do not respond to prism adaptation.

To determine whether patients who respond to prism adaptation are more accurately corrected by operating for the prism-adapted angle or the original angle of deviation.

To determine the usefulness of certain input variables (e.g., age at the time of surgery, size of the deviation, visual acuity, binocular function, refractive error) in predicting which patients are more likely to benefit from prism adaptation.


Acquired esotropia (crossed eyes that develop after a child reaches the age of 6 months) accounts for 25 percent of all patients with misaligned eyes. Surgery to correct esotropia is done primarily to attain functional use of the two eyes together. The cosmetic aspect of the surgery is secondary. In 40 to 50 percent of cases, more than one operation is needed to accomplish the primary goal, and in some cases even three and four operations are needed.

Preliminary studies from two eye care centers reported that the use of prisms on eyeglasses for about a month before surgery led to good results after a single operation in more than 90 percent of patients. These uncontrolled preliminary studies pointed to the need for a multicenter, randomized, controlled clinical trial designed to prove or disprove scientifically the beneficial effect of prisms.

The Prism Adaptation Study was a double randomization trial involving 286 patients. Three-fifths of the patients were randomly selected for prism adaptation before surgery. Of the patients who responded to the prisms, one-half were randomly selected to have surgery based on the amount of prism required to stabilize the deviation, and the other half had surgery based on the amount of esotropia originally measured. Patients who did not respond to the prisms also had surgery based on the amount of esotropia measured, as did the two-fifths of the patients who did not undergo prism adaptation.

Patients were examined postoperatively at 1 week, 1 month, 3 months, 6 months, and 1 year. An independent examiner, masked to the treatment assignment, evaluated the patient at the 6-month followup. The results were analyzed to determine whether the outcome was better in patients who underwent prism adaptation or in those who underwent conventional treatment. Because the examiner did not know what type of treatment a patient had received, he or she would have no bias in evaluating the results.

Study Design

Allocation: Randomized, Endpoint Classification: Efficacy Study, Primary Purpose: Treatment




Prisms in Eyeglasses




National Eye Institute (NEI)

Results (where available)

View Results


Published on BioPortfolio: 2014-08-27T04:00:17-0400

Clinical Trials [16 Associated Clinical Trials listed on BioPortfolio]

Congenital Esotropia Observational Study (CEOS)

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Smart Autofocusing Eyeglasses

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PubMed Articles [29 Associated PubMed Articles listed on BioPortfolio]

Acute Onset Esotropia From Excessive Smartphone Use in a Teenager.

Acute acquired comitant esotropia secondary to smart-phone use is a newly described phenomenon. This case report describes a boy with acute acquired comitant esotropia due to prolonged smartphone use ...

A Cluster of Cyclic Esotropia: White Matter Changes on MRI and Surgical Outcomes.

To report a series of patients with cyclic esotropia, their surgical outcomes, and incidental findings.

Lateral rectus sag and recurrent esotropia in children.

To describe the clinical and intraoperative findings of an anatomic abnormality in children that resembles sagging eye syndrome documented in older adults and that led to recurrent esotropia after sur...

The Effect of Vertically Yoked Prisms on Binocular Vision and Accommodation.

Vertically yoked prisms have been used in treatment of binocular vision dysfunction despite minimal supporting evidence. In people with normal binocular vision, the impact on phorias has been assessed...

Infrared photographs with a selective wavelength filter to diagnose small-angle esotropia in young children.

To validate the effectiveness of the selective wavelength filter analysis with infrared photographs for diagnosing small-angle esotropia in children under age 4.

Medical and Biotech [MESH] Definitions

Cylindrical epithelial cells in the innermost layer of the ENAMEL ORGAN. Their functions include contribution to the development of the dentinoenamel junction by the deposition of a layer of the matrix, thus producing the foundation for the prisms (the structural units of the DENTAL ENAMEL), and production of the matrix for the enamel prisms and interprismatic substance. (From Jablonski's Dictionary of Dentistry, 1992)

A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.

A form of ocular misalignment characterized by an excessive convergence of the visual axes, resulting in a "cross-eye" appearance. An example of this condition occurs when paralysis of the lateral rectus muscle causes an abnormal inward deviation of one eye on attempted gaze.

Sterile solutions, essentially free from foreign particles and suitably compounded and dispensed, for instillation into the eye. It does not include solutions for cleaning eyeglasses or CONTACT LENS SOLUTIONS. (From Dorland, 27th ed)

Products or parts of products used to detect, manipulate, or analyze light, such as LENSES, refractors, mirrors, filters, prisms, and OPTICAL FIBERS.

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