Preoperative Prism Adaptation Research Articles

Effect of 4-week preoperative prism adaptation in preventing postoperative residual esotropia.

Preoperative prism adaptation (PPA) simulates postoperative status and possibly can predict postoperative undercorrection before surgery in esotropia. The present study aimed to assess the effect of 4-week PPA in preventing postoperative residual esotropia. Seventy-five (75) esotropes who had undergone surgery at a single strabismus center were retrospectively enrolled. They included 25 basic, 31 acute comitant, 10 partially accommodative, and 9 recurrent esotropia patients. The preoperative deviation angle, which had been determined using the alternating prism and cover test, was fully corrected with press-on prisms 4 weeks before surgery. If there was an increase of 5 PD or more of esodeviation, the prisms were changed accordingly at 2 weeks. The deviation angle measured at 4 weeks was determined as the surgical target angle. Patients were then divided into increase (≥ 5 PD increase of angle during 4-week PPA) and non-increase groups. Success was defined as either esodeviation of 8 PD or under or exodeviation of 5 PD or under at distance at postoperative 6 months. The increase group included 44 patients (58.7%). The mean deviation angle before PPA was 27.4 PD, and after the 4-week PPA, there was an average increase of 9.4 PD. The success rate was 90.9% in the increase group and 96.8% in the non-increase group (p = 0.316). There were no intergroup differences in preoperative clinical characteristics, esotropia types, postoperative deviation angle or postoperative near stereopsis (p > 0.05). The results of this study indicated a beneficial effect of 4-week PPA in esotropia of various types, specifically by uncovering the hidden esodeviation in the increase group and simulating the postoperative alignment in both the increase and the non-increase groups.

Prism adaptation test before strabismus surgery in patients with decompensated esophoria and decompensated microesotropia

PurposeTo evaluate the effect of Prism adaptation test (PAT) on the angle of squint in decompensated esophoria (decEPH) and decompensated microesotropia (decMET).MethodsIn this single-center retrospective study we reviewed the medical records of patients with the diagnosis of decEPH or decMET, aged at least 12 years, who were treated by strabismus surgery for the first time. The maximum Angle of squint (AOS) for far (F) and near (N) fixation and PAT results before surgery, as well as AOS (F) and AOS (N) after surgery and results of binocular function tests were considered. PAT included wearing a prism based on the largest angle for over 60 min.Results100 patients (mean age 37 ± 17 years) were included in the decEPH group, 82 patients (mean age 30 ± 13 years) in the decMET group. For decEPH, before surgery AOS was 25.5 ± 8.8 pdpt (F) and 23.5 ± 9.8 pdpt (N). During PAT the AOS increased significantly by 2.7 ± 4.3 to 28.2 ± 8.6 pdpt (F) and by 4.9 ± 4.5 to 28.3 ± 9.5 pdpt (N). Altogether, in 82% of decEPH patients AOS (F) and/ or AOS (N) in- or decreased by at least 3 pdpt. For decMET, before surgery AOS was 28.6 ± 10.8 pdpt for far (F) and 30.9 ± 11.8 pdpt for near fixation (N). During PAT the AOS increased significantly by 4.2 ± 5.8 to 32.5 ± 9.5 pdpt (F) and by 3.7 ± 6.1 to 34.4 ± 9.5 pdpt (N). Altogether, in 51% of decMET patients, AOS (F) and/ or AOS (N) increased by at least 10 pdpt, therefore more than 5° which would have been maximally expected from mictrotropia, or decreased by at least 3 pdpt.ConclusionsThe Prism adaptation test (PAT) showed remarkable changes in AOS in both decEPH and decMET. In patients with decEPH, the preoperative assessment of the “true AOS” under PAT reflects a pivotal requirement for successful strabismus surgery, as 82% had dose relevant angle changes ≥ 3 pdpt. For patients with decMET the preoperative prism adaptation test is especially of diagnostic value, but also 51% of decMET patients had changes in AOS beyond the expected microtropic angle (≥ 10 pdpt) or even a dose relevant angle decrease (≥ 3pdpt).

A comparative study of various prism adaptation forms in the surgical management of esophoria

PurposeTo evaluate the outcome in participants who underwent surgery for esophoria following one of three different methods of preoperative prism adaptation test (PAT).MethodsThis prospective, multicentre study was carried out at five eye departments from 2012 to 2019. 116 participants were included and allocated to three groups as per investigator choice: Group 1 (n = 55) had a short prism adaptation period ranging from 1 to 5 hours during their visit at the clinic. Group 2 (n = 36) underwent partial prism correction for at least 4 weeks before surgery. Group 3 (n = 25) underwent full prism correction for at least 4 weeks before surgery. Motoric success was determined by postoperative angle of deviation (AOD), and sensoric success was evaluated with Lang and Bagolini striated lens test.ResultsA significant increase (p < 0.001) in AOD after PAT was observed in all groups, with no significant difference between groups (distance: p = 0.22; near: p = 0.31). Motoric and sensoric success was comparable between groups 3 months (p = 0.52; p = 0.55) and 1 year (p = 0.53; p = 0.29) after surgery. Prolonged prism adaptation (n = 24) for more than 365 days was not associated with better results.ConclusionOur study indicates that the postoperative result is independent from the duration and amount (partial or full correction) of prism adaptation before surgery at least up to one year of follow‐up. Prolonged prism adaptation (>365 days) before surgery does not improve the results.

Efficacies of preoperative prism adaptation test and monocular occlusion for detecting the maximum angle of deviation in intermittent exotropia

BackgroundThe efficacies of prism adaptation test (PAT) and monocular occlusion (MO) and their optimal test durations to detect the maximum angles of deviation at near and distance in eyes with intermittent exotropia (IXT) were assessed and compared.MethodsWe retrospectively reviewed the medical records of 72 patients with IXT. All the patients had undergone the initial strabismus surgery between April 2015 and October 2018 and had been preoperatively tested by both PAT and MO performed on different days for 30 and 60 min. Near and distance deviations after 30 and 60 min of PAT and MO were compared to their baseline measurements obtained immediately after prism wear and before occlusion by alternate prism cover test. The near/distance measurements and required test duration to reveal the maximum deviation angle were also compared between PAT and MO.ResultsCompared with the baseline, the near deviation by PAT significantly increased after 30 (P < 0.05) and 60 (P < 0.01) minutes but not the distance deviation. However, the increase after 30 min was not significant. By MO, neither near nor distance deviation showed a significant difference from the baseline after 30 and 60 min. PAT showed a significantly larger near deviation than MO at 30 and 60 min, but a larger distance deviation by PAT was only observed at 30 min.ConclusionsIn patients with basic and convergence insufficiency types of IXT, a 30-minute PAT appears to be more effective than MO in revealing the maximum angle of deviation before strabismus surgery.

Long-term surgical outcomes of preoperative prism adaptation in patients with partially accommodative esotropia.

To determine the long-term surgical outcomes of preoperative prism adaptation test (PAT) in patients with partially accommodative esotropia. PAT was performed for the remaining esotropia after full correction of hyperopia. Prism adaptation (PA) responders were defined as patients with stable esodeviation between 0 and 8 prism diopters (PD) while developing sensory fusion throughout the prism adaptation period. Surgical success was defined as a deviation within 8 PD of both the far and near deviation angles at the last follow-up examination. Of the 102 patients, 43 (42.2%) were PA responders, and 59 were PA non-responders (57.8%). After a mean follow-up duration of 6 years after surgery, the surgical success rate was significantly higher in PA responders (76.7% vs. 54.2%, p = 0.023). By multivariate analysis, good stereoacuity at near before surgery significantly correlated with successful outcomes after surgery (p = 0.001, β = 4.466). The risk factors of undercorrection were preoperative esotropia >35 PD (OR 3.067, p = 0.041), and preoperative hyperopia >+5.25 diopters (OR 3.099, p = 0.049). Among undercorrected patients, the annual decrease of esodeviation was significantly greater in PA responders (p = 0.043). PA responders showed a better long-term success rate than in PA nonresponders. Patients with high hyperopia and large esotropia had a higher risk of undercorrection. Undercorrected patients eventually achieved good motor outcome with postoperative prism correction if they were PA responders before surgery.

The impact of prism adaptation test on surgical outcomes in patients with primary exotropia

BackgroundWe aimed to determine the impact of the preoperative prism adaptation test (PAT) on surgical outcomes in patients with primary exotropia.MethodsThirty‐eight consecutive patients with primary exotropia were enrolled. Pre‐operative PAT was performed in 18 randomly selected patients (Group 1). Surgery was based on the angle of deviation at distance measured after PAT. The remaining 20 patients in whom PAT was not performed comprised Group 2. Surgery was based on the angle of deviation at distance in these patients. Surgical success was defined as ocular alignment within eight prism dioptres (PD) of orthophoria.ResultsSatisfactory motor alignment (± 8 PD) was achieved in 16 Group 1 patients (88.9 per cent) and 16 Group 2 patients (80 per cent) one year after surgery (p = 0.6; chi‐square test). There were no statistically significant differences in demographic parameters, pre‐operative and post‐operative angle of deviation between the two groups (p > 0.05; Mann‐Whitney U and chi‐square tests). Nine patients in Group 1 (50 per cent) and two patients in Group 2 (10 per cent) had increased binocular vision one year post‐operatively. A statistically significant difference was determined in terms of change in binocular single vision between the two groups (p = 0.01; chi‐square test).ConclusionAlthough the prism adaptation test did not lead to a significant increment in motor success, it may be helpful in achieving a more favourable functional surgical outcome in patients with primary exotropia.

A Pilot Study of the Value of Prism Adaptation in Planning Strabismus Reoperations

To evaluate the value of prism adaptation in planning strabismus reoperations. Of 15 patients with persistent strabismus, 9 underwent prism adaptation prior to strabismus reoperation and 6 underwent strabismus reoperation without preoperative prism adaptation. Corrective surgery was performed on the same or new muscles. Follow-up ranged from 3 months to 2 years. A horizontal deviation of 10 prism diopters or less was considered a successful outcome. Statistical analysis of the results was done. Of the 9 patients who had prism adaptation, 3 (33%) were responders and 6 (67%) were nonresponders. A successful outcome was achieved in 6 patients (67%) who had prism adaptation and 3 patients (50%) who did not. The difference between groups was statistically insignificant (P > .05). These results suggest that the benefits of prism adaptation are not significant enough to justify the time consumption and expenses of this test when planning strabismus reoperations, but a larger group of patients should be studied.

Maximum motor fusion combined with one-hour preoperative prism adaptation test in patients with acquired esotropia

Preoperative prism adaptation and the maximum motor fusion test reduce the risk of postoperative undercorrection, overcorrection, and bifocal requirements in acquired esotropia. The purpose of our study is to determine the efficacy of the maximum motor fusion test followed by a short prism adaptation test in patients with acquired esotropia undergoing bilateral medial rectus muscle recession. We undertook a retrospective review of 29 subjects with acquired esotropia without history of amblyopia, previous strabismus surgery, use of bifocals, pattern anisotropia, dissociated vertical deviation, or oblique muscle dysfunction. All subjects underwent bilateral medial rectus muscle recessions based on the distance angle of deviation measured with the maximum motor fusion test followed by prism adaptation test. Alternate prism and cover testing was performed after 1 hour of prism adaptation to determine the angle of deviation for surgical correction. The age at surgery was 4.5 +/- 1 years. The preoperative angle of deviation at distance was 20.4 +/- 4.2(delta). It increased to 36.2 +/- 4.2(delta) after the maximum motor fusion test followed by 1 hour of prism adaptation testing. The final preoperative angle of deviation post motor fusion test-prism adaptation test was significantly larger than the initial angle of deviation (p < 0.0001). The final postoperative deviation at distance was 1.3 +/- 3.3(delta), and 5.2 +/- 1.5(delta) at near. Postoperative follow up was 18 +/- 2.6 months (range, 13-24 months). The combination of maximum motor fusion and preoperative prism adaptation allowed increased amounts of medial rectus muscle muscle recession, decreasing the risk of postoperative undercorrection without increasing the risk of overcorrection.

Prism adaptation in visually mature patients with esotropia of childhood onset

Objective To investigate the role of prism adaptation in the visually mature population with esotropia onset before visual maturation. Design Retrospective, noncomparative case series. Participants Eighty-five patients, 26 prism adapted for near (PAN) and 59 prism adapted for distance (PAD), were included in the study. Methods Patients included in this study were older than 9 years and had esotropia with an onset before age 9. Mean follow-up was 30 months (range = 6 weeks–164 months). All patients had prism adaptation and subsequent surgical correction. Surgical success was defined as peripheral fusion on the Worth 4-dot test and ≤8 Δ deviation at near and distance on the simultaneous prism and cover test. Main outcome measures Response to preoperative prism adaptation and postoperative alignment and sensory results were examined. Results Twenty-six of the 85 patients had previous surgical esotropia correction. In the PAD group, 41 were responders. Seventeen of these had built their deviation ≥10 Δ with prism adaptation. All responders had surgery for their prism-adapted angle. Postoperatively, 34 of 41 (83%) responders and 6 of 18 (33%) nonresponders had fusion. In the PAN group, 17 were responders. Nine of these built their deviation with prisms. Postoperatively, 16 of 17 (94%) responders and builders and 1 of 9 (11%) nonresponders had successful surgery with sensory and motor fusion. Conclusions Adults with esotropia onset before visual maturation can be prism adapted and surgically treated with a predictable outcome of sensory and motor fusion. Those prism adapted for near with response can be successfully treated with surgery for the near deviation. Prism adaptation also aids in determining those who would benefit from larger amounts of surgery.

Preoperative prism adaptation in acquired esotropia with convergence excess

Purpose The prism adaptation test (PAT) is used preoperatively to determine the surgical target angle for acquired esotropia. We assessed the surgical outcomes for children with convergence-excess esotropia (near esotropia greater than distance esotropia by 10 prism diopters [PD] or more) whose target angle was based on the results of the PAT geared to the near deviation. Methods We reviewed the charts for all of one surgeon’s patients who underwent the PAT for near convergence-excess esotropia and who were followed-up for at least 6 months after surgery. Patients who wore prisms were classified as PAT responders (esotropia <= 8 PD at distance and near with four-dot fusion at near) or nonresponders (exotropia at distance or lack of four 4-dot fusion at near). Responders underwent surgery for the adapted angle at near. The nonresponders who had exotropia at distance had surgery for an angle between the near and distance angles. Nonresponders with esotropia angles <= 8 PD at distance and near underwent surgery for the total near deviation. Results Fifty-four (83%) of the 65 children were PAT responders. Thirty-nine (72%) of the 54 responders and 6 (55%) of 11 nonresponders had excellent results (heterotropia <= 8 PD at distance and near with four-dot fusion at near). All 13 responders whose angles built with prism had excellent results. Among 61 patients who had an esotropia <= 8 PD at near with prisms preoperatively, only 4 (6.6%) developed overcorrections at distance by the latest follow-up examination; 3 were responders and 1 a nonresponder. Conclusions PAT for the near deviation in children who have convergence-excess esotropia is a useful test in estimating the target angle for surgery. Responders whose angles built with prism had a particularly high success rate. Surgery geared to the near-adapted angle has a low risk of creating an overcorrection in the distance regardless of the response to PAT.

Preoperative prism adaptation for acquired esotropia: Long-term results

Purpose: The efficacy of preoperative prism adaptation in subjects with acquired esotropia has been established at 6 and 12 months postoperatively. We evaluated the outcomes of subjects with acquired esotropia who had preoperative prism adaptation and were followed longer than 12 months. Methods: A retrospective analysis was undertaken of 2 groups of subjects with acquired esotropia who underwent bilateral medial rectus recessions based on the distance angle of deviation and were followed more than 12 months postoperatively. Group A subjects had preoperative prism adaptation to determine the target angle for corrective surgery. In Group B subjects, surgery was based on the maximum angle of strabismus at distance, determined by alternate prism cover test without preoperative prism adaptation. Results: We compared 17 subjects in Group A and 19 subjects in Group B. The postoperative follow-up period was 3 ± 1.7 years in Group A and 4.8 ± 1.8 years in Group B. The age at the last visit was 9.1 ± 2 years in Group A and 10 ± 2 years in Group B. Postoperative residual esotropia was 2.6 ± 2.5 PD at distance in Group A patients and 6.6 ± 5.9 PD in group B patients (P =.002). Residual esotropia at near was 3 ± 3.8 PD in Group A and 11.5 ± 8.12 PD in Group B (P <.01). More Group B subjects required bifocal spectacles to achieve optimal alignment at near (P =.001). Conclusion: Acquired esotropia subjects operated on for their distance prism-adapted angle maintained better motor alignment over a long-term follow-up period when compared with nonprism-adapted subjects operated on for their distance angle. (J AAPOS 2002;6:168-73)

A randomized comparison of prism adaptation and augmented surgery in the surgical management of esotropia associated with hypermetropia: One-year surgical outcomes

Objective: To compare motor and sensory 1-year surgical outcomes in patients with hypermetropic esotropia, managed with either augmented surgery based on the average of the near deviation with and without correction or preoperative prism adaptation. Methods: Forty-three patients with hypermetropic esotropia without distance-near disparity entered a randomized prospective evaluation of augmented surgery (group A, 27 patients) versus prism adaptation (group P, 16 patients). The formula for augmenting the amount of the rectus muscle recession was based on the average of the near deviation with and without correction in group A and the prism-adapted angle of deviation in group P. During prism adaptation, 9 of 16 patients in group P responded to prism. Motor and sensory outcomes of the Worth 4-dot test at 6 and 0.33 m and the Titmus stereotest were evaluated 1, 3, 6, and 12 months after surgery. Results: Postoperative deviations of 8 PD or less at distance were achieved in 24 of 27 patients (89%) of group A and in 7 of the remaining 8 patients (88%) of prism responders and in all 7 prism nonresponders (100%) in group P. No significant difference existed between groups A and P, as well as between the prism responders and prism nonresponders in group P in terms of near and distance deviation 1 year after surgery. The sensory outcomes improved over time in group A and prism responders. Conclusion: There were no significant differences in the surgical outcomes between each group. However, the small sample size may limit the power to detect any statistically significant differences. (J AAPOS 2001;5:31-4)

Prognostic factors for successful surgical outcome with preoperative prism adaptation test in patients with superior oblique palsy

This study evaluated the surgical outcome of patients managed with preoperative prism adaptation test (PAT) and investigated prognostic factors for successful motor alignment in adult patients with superior oblique palsy. Prospective study of preoperative PAT was performed. Fifty-seven patients with superior oblique palsy, aged 16 to 81 years, participated in this study. Patients were assigned to surgery with the target angle based on either the original angle or the prism compensated angle. When the amount of neutralizing prism exceeded 4delta or more compared to the original angle of deviation, the patient was defined as having prism compensation, and the target angle for surgery was based on the amount of neutralizing prism. The motor success rate was compared between the 2 groups at the 3-month postoperative follow-up. The prism responders group showed a superior outcome compared to that of the prism non-responders group (77% successful outcome compared with 46%, p = 0.0397). The presence of prism compensation and the amount of vertical deviation were significant prognostic factors for successful motor alignment. Preoperative PAT is a useful prognostic indicator of successful surgical outcome in patients with superior oblique palsy.

Prism Adaptation in Strabismus

Prisms have both diagnostic and therapeutic uses in strabismus. Many clinicians have popularized the use of prisms preoperatively to determine the target angle for surgery in esotropic patients. A review of the literature shows that preoperative prism adaptation, and the prism adaptation test is effective in predicting postoperative sensory and motor fusion in patients with acquired esotropia. Other patients may also benefit from prism adaptation.

Preoperative prism correction in patients with acquired esotropia

We performed a prospective study of preoperative prism adaptation in 77 patients with acquired esotropia. Sixty-three of them increased their angle of squint when wearing Fresnel press-on prisms for 5-7 days. After the angle had stabilized to a point that did not exceed the press-on prisms by more than 10 prism D, they were randomly divided into two groups. Thirty-two patients underwent surgery based on the prism-adapted angle. The other 31 patients underwent surgery based on their initially measured angle. Fourteen patients who did not respond to prism correction underwent surgery based on the angle before prism correction. Success rates with deviations between 0 and 10 prism diopters measured 1 year after surgery were highest in those in whom surgery was based on the prism-determined angle and were lowest in the nonresponders, who had no fusion response to the prisms.

Preoperative prism adaptation in acquired esotropia.

41 patients with acquired esotropia who did not have preoperative prism adaptation were compared to 50 patients who were prism-adapted prior to surgery. Surgical success was evaluated at a postoperative period of 6 months. 82% of the patients who responded to prism adaptation had a successful surgical result as compared to only 51% of the patients who did not wear prisms preoperatively.