|Year : 2016 | Volume
| Issue : 1 | Page : 38-42
Effectiveness of prisms in relieving diplopia in superior oblique palsies
R Neena1, A Giridhar2
1 Paediatric Ophthalmology and Adult Strabismus Services, Giridhar Eye Institute, Kochi, Kerala, India
2 Medical Director, Vitreoretina Services, Giridhar Eye Institute, Kochi, Kerala, India
|Date of Web Publication||11-Nov-2016|
Giridhar Eye Institute, Kadavanthara, Cochin - 682 020, Kerala
Source of Support: None, Conflict of Interest: None
Aim: To study the effectiveness of prisms in relieving diplopia in patients with superior oblique palsies.
Materials and Methods: This was a retrospective study of all patients with superior oblique palsies who were prescribed prisms for relief of symptomatic diplopia in our institute from September 2013 to March 2015. A detailed analysis was performed of demographic features of the patients; nature, onset, duration, and course of diplopia; measurement of deviation in all gazes; diplopia charting; assessment of torsion; systemic risk factors; and amount and type of prism given. The effectiveness of prisms was measured by an objective score by the examiner as well as a subjective score reported by the patient.
Results: Among the total 25 patients, 21 patients had acquired superior oblique palsies and 4 patients had congenital causes. Males outnumbered females. Majority had unilateral involvement. Deviation in primary position ranged from 3 Prism Dioptre to 25 PD with 80% having less than 10 PD. Seventy-six percent had less than 10° torsion in primary gaze. Eighty-eight percent were given less than 10 PD prisms, 12% were given more than 10 PD, of which two were Fresnel Prisms. Seventy-six percent were satisfied with the prisms. Fifty-two percent had spontaneous improvement whereas 16% needed surgery.
Conclusion: Prisms were effective in relieving diplopia in most of the acquired unilateral superior oblique palsies where the primary deviation was less than 10 PD and torsion was less than 10°.
Keywords: Diplopia; prisms; superior oblique palsy.
|How to cite this article:|
Neena R, Giridhar A. Effectiveness of prisms in relieving diplopia in superior oblique palsies. Kerala J Ophthalmol 2016;28:38-42
| Introduction|| |
Superior oblique Palsy is the most common cause for an isolated vertical deviation, and is also the most common cyclovertical muscle palsy encountered by the ophthalmologist. It can cause intolerable diplopia, which may be vertical, diagonal, and or torsional. Very often, the diagnosis is delayed as clinical signs are very subtle and can be easily missed by the general practitioner.
An ophthalmic prism  is a transparent triangular wedge of refracting material. Because of their optical properties, prisms can be used to realign the visual axis and correct diplopia when present. Prisms are generally recommended for optical correction of symptomatic binocular diplopia. They alleviate diplopia by altering the path of light rays and aligning the image on the fovea of the deviating eye. The main goals of prism prescription in incomitant deviations are to relieve the patient of diplopia, to correct a significant abnormal head posture, and to allow single vision in primary and down gazes. Prisms can be dispensed as “ground in” prisms or “stuck on” Fresnel prisms.,,
To study the effectiveness of prisms in relieving diplopia in patients with superior oblique palsies.
| Materials and Methods|| |
This was a retrospective study of all patients with superior oblique palsies, who were prescribed prisms for relief of symptomatic diplopia in our institute from September 2013 to March 2015. The study excluded patients with multiple cranial nerve palsies, although bilateral superior oblique palsies were included.
The diagnosis of superior oblique palsy was based on:
(1) Symptoms of vertical/torsional binocular diplopia; (2) presence of abnormal head posture (head tilt/face turn to opposites side/chin down posture); (3) positive Parks–Bielschowsky test; (4) prism bar cover test for distance and near, as well as in all 6 diagnostic gazes; (5) diplopia charting; (6) double Maddox Rod (DMR) tests; (7) presence of inferior oblique overaction with or without superior oblique underaction.
Apart from these, diagnosis of congenital superior oblique palsy  was made based on presence of:
(1) Long-standing contralateral head tilt (as noted from old photographs; (2) facial asymmetry (seen in 75% patients with face on side of head tilt hypoplastic and smaller; being dependent); (3) large vertical fusional amplitudes (even up to 35 PD); (4) lack of extorsional diplopia; (5) lack of extorsion by maddox rod.
Diagnosis of acquired superior oblique palsy was made on the features of:
(1) Recent duration; (2) small vertical fusional amplitudes; (3) symptomatic vertical/extorsional binocular diplopia; (4) Extorsion on DMR; (5) history of closed head trauma/presence of precipitating systemic risk factors.
Bilateral Superior Oblique palsies were diagnosed based on:
(1) Chin down posture; (2) symptomatic torsional binocular diplopia; (3) H/o closed head trauma with loss of consciousness (LOC); (4) “V” pattern esotropia; (5) reversing hypertropia on side gazes; (6) alternating hypertropia on head tilt; (7) torsion more than 12°.
We analyzed the demographic features of the patients such as age, sex, eye involvement, features of diplopia such as nature, onset, duration, and course, presence of abnormal head posture, measurement of deviation in all gazes, diplopia charting, assessment of torsion by DMR, systemic risk factors, and amount and type of prism dispensed.
Prisms were prescribed to patients after a meticulous prism trial. One-third of the total measured deviation in primary position was put in front of the affected eye after giving appropriate refractive correction. The patient was asked to read the 20/400 (6/60) line and prismatic power was slowly increased/decreased till the patient reported freedom from diplopia. Distance, near, and down gaze positions were tested. Up to 6 PD, prisms were ground in glasses. If the prisms exceeded 6 PD, then it was split in front of both eyes or Fresnel prisms were tried in front of the affected eye. Patients were informed about the advantages and possible disadvantages such as reduction in visual acuity, reduction in contrast, optical aberrations, and scattering of light. The possibility of spontaneous recovery over a course of time was explained to all patients with acquired superior oblique palsies.
Indications of Fresnel prisms were:
(1) Prismatic correction >12 PD; (2) intolerance to prism in good eye; (3) temporary usage.
Advantages were being light weight and cosmetically acceptable. Disadvantages were cost, blurred vision due to light scattering, and loss of contrast.
Patients were followed-up at 1 month, 3 months, 6 months, and 1 year from prescribing prisms, for at least a period of 3 months. They were given a feedback form at 1-month follow-up to chart their experience with prism glasses. The effectiveness of prisms was measured by an objective score [Table 1] by the examiner as well as by a subjective score [Table 2], as reported by the patient in the feedback form. A total score of 8 or more was taken as satisfactory (A) and total score less than 8 was taken as unsatisfactory (B) on the objective scoring of prismatic glasses. In the subjective scoring of prismatic glasses by the patients, (A) was taken as satisfied with prisms and (B) as not satisfied with prisms.
|Table 2: Patient satisfaction score of prismatic glasses-subjective scoring|
Click here to view
| Results|| |
There were a total of 25 patients included in the study, of which 21 (84%) were males and 4 (16%) were females. The mean age was 52.08 years and standard deviation was 15.21. Majority (92%) had unilateral involvement (48% OD and 44% OS), with only 2 (8%) patients with bilateral involvement. All of them had a contralateral head tilt, except 1 patient with bilateral superior oblique palsy, who had a chin down posture. Among the total 25 patients, 21 patients (84%) had acquired superior oblique palsiy, and 4 patients (16%) had congenital causes. Ischemic causes of diabetes mellitus, hypertension, hyperlipidemia, etc., accounted for a majority of acquired superior oblique palsies (57.14%) [Figure 1]. Closed head trauma from road traffic accidents (38.09%) and intracranial space occupying lesion (4.76%) were responsible for the remaining acquired cases. Vertical deviation in primary gaze ranged from 3 PD to 25 PD, with 80% having less than 10 PD. The mean vertical deviation was 7.64 PD (prism dioptre) [Figure 2]. Seventy-six percent had less than 10° torsion in primary gaze by DMR test. The mean torsion was 5.48°. Eighty-eight percent were given less than 10 PD prisms, 12% were given more than 10 PD, of which two were Fresnel Prisms [Figure 3]. The mean vertical prismatic prescription was 6.4 PD. One patient was given total 10 PD vertical prism which was split between the two eyes (6PD BD OS, 4PD BU OD), and 1 patient had to be given additional horizontal prism in the other eye (4 PD BI OD, 4 PD BD OS). The average total objective prism satisfaction score was 11.52. Nineteen patients (76%) were satisfied with the prisms, both by subjective and objective score analysis [Figure 4], [Figure 5], [Figure 6]. There was good agreement between the two scoring systems as per Kappa standard analysis (P < 0.001) [Table 3]. We analyzed if the patient age had any influence on successful prism use, but failed to get any statistical significance by Chi-square test [Table 4]a and [Table 4]b. Majority of the patients, who were happy with prisms, had acquired unilateral superior oblique palsies (78.95%), where the primary deviation was less than 10 PD and torsion was less than 10° [Figure 4] and [Figure 5]. Though all the 4 patients with congenital superior oblique palsy were satisfied with prisms, 2 (50%) opted for surgery after 6 months. Among the total 25 patients, 13 patients (52%) had spontaneous improvement with average recovery time of 4.61 months, 4 patients (16%) opted for muscle surgery, 4 patients (16%) continued to use prism glasses, and 4 patients (16%) neither recovered spontaneously nor opted for surgery, and were not happy with prisms.
| Discussion|| |
In this retrospective study of patients with symptomatic superior oblique palsies, we found prisms to be an effective tool in relieving binocular diplopia. Seventy six patients reported satisfaction with them. Previously, Roodhooft and VanRens  and Bixenman  have reported cases of patients with fourth nerve palsy who were satisfied with prisms. In a comparable study, Tamhankar et al. reported overall 92% satisfaction with the use of prisms.
In our study, majority of the patients, who were happy with prisms had acquired unilateral superior oblique palsies (78.95%) as compared to the study by Tamhankar et al. who reported a higher success rate for congenital palsies. Most (57%) of the acquired ischemic palsies in our series recovered, however, majority (62.5%) of those with closed head trauma failed to recover spontaneously. Patients with congenital superior oblique palsies needed only 50% of their primary deviation as prismatic correction, whereas those with acquired palsies needed nearly full prismatic correction, possibly due to greater fusional amplitudes in the former. This was similar to the recommendations by Tamhankar et al. in their study in which they recommended prism prescription equal to 50% of primary deviation for congenital superior oblique palsies and higher prism prescription almost equal to primary position deviation in acquired palsies.
Though majority of the patients (52%) in our series, especially those with acquired palsies recovered, the diplopia was troublesome enough for them to opt for prisms rather than wait for spontaneous recovery.
Limitations of our study include small sample size, retrospective nature of the study, and short duration of follow up.
| Conclusion|| |
Prisms were most effective in relieving diplopia in most of the acquired unilateral superior oblique palsies, where the primary deviation was less than 10 PD and torsion was less than 10°. We recommend that prisms be offered as a primary treatment for all patients with symptomatic superior oblique palsy.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Parks MM. Isolated cyclovertical palsy. Arch Ophthalmol 1958;60:1027-35.
Suzanne V'eronneau-Troutman. Prisms in the Medical and Surgical Management of Strabismus. Chapter 1. Mosby. p. 3.
Knapp P. Recent advances in strabismus management. Use of membrane prisms. Trans Sect Ophthalmol Am Acad Ophthalmol Otolaryngol 1975;79:718-21.
Véronneau-Troutman S. Fresnel prism membrane in the treatment of strabismus. Can J Ophthalmol 1971;6:249-57.
Flanders M, Sarkis N. Fresnel membrane prisms: Clinical experience. Can J Ophthalmol 1999;34:335-40.
Paysee EA, Coats DK, Plager DA. Facial asymmetry and tendon laxity in superior oblique palsy. J Pediatr Ophthalmol Strabismus 1995;32:158-61.
Roodhooft J, Van Rens G. A prism is a useful tool in the treatment of vertical diplopia. Bull Soc Belge Ophtalmol 1998;268:215-22.
Bixenman WW. Vertical prisms. Why avoid them? Surv Ophthalmol 1984;29:70-8.
Tamhankar MA, Ying GS, Volpe NJ. Success of Prisms in the Management of Diplopia Due to Fourth Nerve Palsy:J Neuroophthalmol 2011;31:206-9.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]