The prism bar—Prentice and frontal positions

Kaye, Stephen B.; Ansons, Alec M.; Green, J R; Wylie, Jennifer

doi:10.1038/eye.1989.60

Cited by 5 publications

(5 citation statements)

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“…The measurement errors in the use of optical prisms were pointed out [1][2][3][4][6][7][8][9]. However, there is no solution to this issue, and attention has not been paid to the issue since the glass prims are still widely used in some countries.…”

Section: Discussionmentioning

confidence: 99%

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Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them

Wang¹,

Pan²,

Zhang³

et al. 2021

IJOVS

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Purpose: Ophthalmic prisms are routinely used to measure ocular deviation. However, large measurement errors could be induced when a prism is not accurately positioned at its calibration position. We report a simple way to minimize the errors. Methods: We measured powers of prisms and plastic prisms at their calibration position and at angles the prism was rotated away from the calibration position. Glass prisms that have power of 20, 25, 30, 40, 50, and 60 prism diopters (PD) and plastic prisms that has power of 20, 25, 30, 35, 40, 45, 50 PD were used. To minimize the errors, we developed a pair of prism frame so that the prism can always be positioned accurately. Results: We have demonstrated large errors induced by rotating glass prisms and plastic prism away from their calibration position. Larger errors were recorded with glass prisms than with plastic prisms. The measurement errors are significant even with a small angle rotation for a large power glass prism. For instance, a 10-degrees rotation of a 50PD glass prism produces an error of 30PD. However, measurements errors were minimized when the prism frame was used. Conclusion: It suggests that the glass ophthalmic prism should be abandoned and the use of ophthalmic prisms in strabismus measurement should be standardized with assistance of the prism frame.

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Section: Discussionmentioning

confidence: 99%

“…However, measurement deviation errors can be induced when a prism is not held at a calibrated position. This problem was pointed out long time ago and all authors focused on theoretical calculation [1][2][3]. Authors in a recent review paper summarized the issues related to this problem [4].…”

Section: Introductionmentioning

confidence: 99%

Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them

Wang¹,

Pan²,

Zhang³

et al. 2021

IJOVS

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“…Each prism cover test (PCT) was repeated and if the measurements were inconsistent, the mean of the two values was then recorded. 11–13 …”

Section: Methodsmentioning

confidence: 99%

“…Each prism cover test (PCT) was repeated and if the measurements were inconsistent, the mean of the two values was then recorded. [11][12][13] Based on the best-corrected acuity of the amblyopic, eye mild amblyopia was classified as Best corrected visual acuity (BCVA) of 20/25 -20/40, moderate as BCVA of 20/40 -20/100 and severe as BCVA of ≤20/100. Surgeries were performed by the same doctor, with the patient under general anaesthesia (patients ≤18 years of age) or local anaesthesia (patients ≥18 years of age).…”

Section: Significance Of the Studymentioning

confidence: 99%

Extraocular muscle resection, recession length and surgery outcome modelling in strabismus treatment: a pilot study

et al. 2021

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BackgroundMany surgical formulas have been developed and proposed based on the experience of surgeons to improve the predictability of strabismus surgery. However, the consent among strabismus surgeons regarding the dose effect of the extraocular muscle (EOM) recession or resection was not achieved yet and the disagreement about the appropriate amount of strabismus surgery still exists.ObjectiveOur study aimed to propose an instrument for EOM resection (RsL) and recession length (RcL) estimation before the surgery and second to elaborate an postoperative angle of deviation (PAD) predictive model using simple potential predictors.Methods and AnalysisThe analytical prospective clinical study was conducted from April 2016 to July 2019, on a sample of 216 patients (aged between 2–58) with concomitant strabismus who underwent strabismus surgery in Clinical Republican Hospital ‘Timofei Mosneaga’and Children Hospital ‘Em Cotaga’ from Republic of Moldova. The correlations of patients’ age, strabismus type, amblyopia degree, RsL, RcL, preoperative angle of deviation (PreAD) with PAD were estimated using Pearson’s correlation analysis. Multiple linear regression analysis, multicollinearity analysis and residual analysis were performed.ResultsThe EOM RsL was predicted using strabismus type, patient’s age, PreAD and EOM RcL. EOM RcL, in turn, was estimated by the similar covariates set, instead of RcL being RsL. PAD modelling showed the PreAD, EOM RsL and EOM RcL predictive ability for strabismus surgery outcome prediction.ConclusionIn our study, we propose four mathematical models as potential instruments for EOM RsL, EOM RcL and PAD modelling in esotropia and exotropia surgery.

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“…The traditional prism bar is frequently held in the frontal position rather than the correct Prentice position (Kaye et al 1989). This is termed the Prentice position, for which traditional prism bars are calibrated.…”

Section: Prism Cover Test (Figure 54)mentioning

confidence: 99%

Ocular Deviation

2013

Diagnosis and Management of Ocular Motility Disorders

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The prism bar—Prentice and frontal positions

Cited by 5 publications

References 1 publication

Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them

Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them

Extraocular muscle resection, recession length and surgery outcome modelling in strabismus treatment: a pilot study

Ocular Deviation

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