Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Changes in corneal and conjunctival sensitivity, tear film stability, and tear secretion after strabismus surgery

J.B. Lee, J.H. Chang & S.H. Han

Department of Ophthalmology, Yonsei Institute of Vision Research, Yonsei University College of Medicine, Seoul, Korea

Y.-H. Chang

Department of Ophthalmology, Ajou University School of Medicine, Suwon, Korea

ABSTRACT: We prospectively investigated the changes in corneal and conjunctival sensitivity, tear film stability, and tear secretion after strabismus surgery. Corneal and conjunctival sensitivity test with Cochet-bonnet esthesiometer, tear film break-up time measurement, and schirmer test were performed prospectively (before operation, 1 week, 1 month and 3 months after operation) in 83 patients (124 eyes) who underwent strabismus surgery in our institution. There were no significant changes in corneal sensitivity, tear film stability, and tear secretion after strabismus surgery (p 0.05). Conjunctival sensitivity decreased significantly after strabismus surgery (p 0.05). The discomfort and dryness after strabismus surgery does not seem to be related with changes in corneal sensitivity, tear film stability, and tear secretion.

1INTRODUCTION

Some patients complain foreign body sensation, burning sensation, or dryness after strabismus surgery. It is now well recognized that the ocular surface and lacrimal gland function as an integrated unit and that the drive for lacrimal tear production and the blink mechanism that spreads and clears tears from the ocular surface is stimulation of the sensory nerves that innervate the ocular surface (Stern et al. 1998). When the afferent nerves of the ocular surface (trigeminal nerve) are stimulated in a normal individual, a reflex results in immediate blinking and secretion of tears. Sensory loss causes decreased tear secretion and reduces the blink rate (Jordan & Baum 1980). As expected, aqueous tear production and clearance have been reported to decrease in conditions where there is disease, damage, or surgical amputation of the corneal nerves (Heigle & Pflugfelder 1996).Various refractive surgical procedures have been associated with marked postoperative hypesthesia. Corneal sensitivity decreases after laser-assisted in situ keratomileusis (LASIK) because of surgical amputation and laser ablation of the nerve fibers innervating the central corneal surface (Campos et al. 1992, Wilson 1999, Perez-Santoja et al. 1999, Kauffmann et al. 1997). Corneal sensitivity after excimer laser photorefractive keratectomy has been noted to be initially reduced, but it returns to almost normal levels 3 months after surgery (Campos et al. 1992, Ishikawa et al. 1994, Trabucchi et al. 1994).

However, little information is available concerning corneal and conjunctival sensitivity, tear film stability, and tear secretion after strabismus surgery. The purpose of this study was to prospectively evaluate corneal and conjunctival sensitivity, tear film stability, and tear secretion in a series of patients before and after undergoing strabismus surgery.

2PATIENTS AND METHODS

We prospectively studied 124 eyes of 83 cooperative patients who underwent strabismus surgery in our hospital from October 2001 to March 2003. Those who had general health problems, previous

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Table 1. Type of operations.

* recession and resection.

ocular surgery, corneal diseases, glaucoma, or history of ocular trauma were excluded. The patients ranged in age from 12 to 61 years (mean 29.4 years). All strabismus surgeries were performed under topical anesthesia by the same surgeon (J.B.Lee) using limbal incision. The type of operation is summarized in Table 1.

Cornea and conjunctival sensitivity measurement with the Cochet-Bonnet esthesiometer (Luneau Ophthalmologie, Chartres Cedex, France), tear break-up time, and Schirmer II test (Schirmer test with anesthesia) were documented before and after surgery. The patients were examined at 1 week, 1 month, and 3 months after surgery. To minimize bias in measurement, all measurements were performed by the same observer. Data are presented as means SD. Statistical analysis was carried out by Wilcoxon rank test, and values of P less than 0.05 were considered statistically significant.

3RESULTS

A total of 83 consecutive patients were enrolled into the study. Thirty-three patients were male and 50 were female. Forty-one patients underwent unilateral strabismus surgery, whereas 42 patients had bilateral strabismus surgery. Results for cornea and conjunctival sensitivity test, Shirmer test, and tear break-up time measurement are shown in Table 2.

The preoperative corneal sensitivity was a mean of 58.5 2.7 mm which is similar to that of a previously reported group of noncontact lens wearing subjects (mean 58 mm) (Pflugfelder et al. 1998). Mean corneal sensitivity value was 58.1 3.2 mm at 1 week, 58.1 3.2 mm at 1 month, and 58.0 3.4 mm at 3 months. There were no significant changes in corneal sensitivity at 1 week, 1 month, 3 months postoperatively (p 0.05). Before surgery, the mean conjunctival sensitivity was 27.8 10.6 mm. Mean conjunctival sensitivity value was 22.3 12.1 mm at 1 week, 21.7 10.4 mm at 1 month, and 24.2 12.2 mm at 3 months. Conjunctival sensitivity decreased significantly after strabismus surgery (p 0.05) with slight recovery at 3 months. Patients had mean Schirmer II test scores of 13.41 3.01 mm before surgery. Mean Schimer test with anesthesia value was 13.35 2.98 mm at 1 week, 13.39 3.08 mm at 1 month, and 13.36 3.23 mm at 3 months. There were no significant changes in tear secretion after strabismus surgery (p 0.05). Patients had mean tear break-up time scores of 8.55 2.55 sec before surgery. Mean tear break-up time score was 8.56 2.76 sec at 1 week, 8.51 2.92 sec at 1 month, and 8.53 2.82 sec at 3 months. There were no significant changes in tear break-up time after strabismus surgery (p 0.05).

No statistical correlation was found between type of operation (recession or resection, horizontal or vertical) and postoperative corneal and conjunctival sensitivity, Schirmer test, and tear break-up time value at any point of follow-up (p 0.05). There was no relationship between

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Table 2. Preoperative and postoperative corneal and conjunctival sensitivity, tear film break-up time, and Schirmer test.

* Statistically significant difference (p 0.05).

number of operated muscles and postoperative corneal and conjunctival sensitivity, Schirmer test, and tear break-up time value at any point of follow-up (p 0.05).

4CONCLUSION

There were no significant changes in corneal sensitivity, tear film stability, and tear secretion after strabismus surgery (p 0.05). Conjunctival sensitivity decreased significantly after strabismus surgery (p 0.05). There was no significant difference in such parameters according to age, the type of surgeries, and number or kind of the operated muscle. The discomfort and dryness after strabismus surgery does not seem to be related with changes in corneal sensitivity, tear film stability, and tear secretion.

REFERENCES

Campos, M. et al. 1992. Corneal sensitivity after photorefractive keratectomy. Am J Ophthalmol 114: 51–4. Heigle, T.J. & Pflugfelder, S.C. 1996. Aqueous tear production in patients with neurotrophic keratitis. Cornea

15: 135–8.

Ishikawa, T. et al. 1994. Corneal sensation following excimer laser for photorefractive keratectomy in humans. J Refract Corneal Surg 10: 417–22.

Jordan, A. & Baum, J. 1980. Basic tear flow. Does it exist? Ophthalmology 87: 920–30.

Kauffmann, T. et al. 1997. Corneal reinnervation after photorefractive keratectomy and laser in situ keratomileusis: an in vivo study with a confocal videomicroscope. Ger J Ophthalmol 5: 508–12.

Perez-Santoja, J.J. et al. 1999. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. Am J Ophthalmol 127: 497–504.

Stern, M.E. et al. 1998. The pathology of dry eye: the interaction between the ocular surface and lacrimal glands [review]. Cornea 17: 584–9.

Trabucchi, G. et al. 1994. Corneal nerve damage and regeneration after excimer laser photokeratectomy in rabbit eyes. Invest Ophthalmol Vis Sci 35: 229–35.

Wilson, S.E. 1999. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. J Refract Surg 15: 603.

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Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Surgery of the inferior oblique muscle in bilateral asymmetric paralysis of the superior oblique

V. Oguz, M. Yolar, H. Tolun & S. Özkan

University of Istanbul, Cerrahpasa Medical Faculty, Istanbul, Turkey

ABSTRACT: The aim of this study is to compare the results of the symmetric surgery and the asymmetric surgery applied in the cases of bilateral asymmetric paralysis of the superior oblique muscle associated with the asymmetric overaction of the inferior oblique.

This study includes 24 patients with the bilateral asymmetric paralysis of the superior oblique, who also had a overaction of the inferior oblique less than to for one eye and to

for the other. In 11 cases out of 24, a bilateral myectomy of the inferior oblique has been applied not considering the difference of the amount of the overaction of the inferior oblique, while myectomy of the inferior oblique was applied to the eye presenting the greatest overaction of this muscle, and to the eye in which this overaction was less significant a recession of the inferior oblique was applied in the rest of the cases.

When these two methods of surgery, asymmetric and symmetric, applied in the bilateral asymmetric paralysis of the superior oblique coexisting with an asymmetric overaction of the inferior oblique, have been compared with respect to the residual overaction of the inferior oblique, the asymmetric surgery has seemed to be more effective than the symmetric surgery.

1INTRODUCTION

The paralysis of the superior oblique bilateral forms of which represents 11 to 29% of the cases, is the most frequent form of the vertical strabismus (1,2). The form of the paralysis is generally asymmetric and as long as the most affected eye is not operated involvement of the other eye may remain almost masked (almost masked paralysis of the superior oblique). Almost masked bilateral paralysis of the superior oblique is characterized by a strongly unequal overaction of the inferior oblique in almost all of the positions of gaze (3–7).

A hypertropia is present in one or two positions of gaze due to the overaction of the inferior oblique muscle. The inversion of the hypertropia is not evident in one or two positions of gaze and in general in the position of oblique gaze to the field of action in which the least overacting effect of the inferior oblique is the most evident and the overaction effect of the inferior oblique may be least pronounced. Almost masked paralysis of the superior oblique has to be suspected in every case of the unilateral apparent paralysis of the superior oblique with overaction of the controlateral inferior oblique and inversion of the hypertropia in the field of action of the overacting oblique (2,8).

The unique signs for the suspicion of the bilateral involvement are a right hypertropia at the gaze to the left and left at the gaze to the right and a positive Bielschowsky test in the two positions of gaze, by tilting the head laterally to either sides, and these findings do not exist in the cases of unilateral involvement.

However the abscence of these signs do not exclude a bilateral involvement in none of the cases. This study includes the cases with a definite asymmetric paralysis of the superior oblique who have been operated by using two different surgical methods of the inferior oblique muscle.

The purpose of this study is to compare the results of these two methods, either the symmetric or the asymmetric surgery, performed in cases of bilateral asymmetric paralysis of almost masked superior oblique, coexisting with the asymmetric overaction of the inferior oblique.

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2MATERIALS AND METHODS

Twenty four cases of bilateral asymmetric overaction of the superior oblique superior with a hypertropia between 5 and 20 PD and also a definitely asymmetric overaction of the inferior oblique being / in one eye and / in the other. All of these patients have been showing almost masked bilateral paralysis oblique superior and followed between 1989 and 2002. The criteria of diagnosis of the bilateral paralysis of the oblique superior have been as follows:

–An evident paralysis of the oblique superior diagnosed by Parks’ three steps test (9),

–Inversion of the hypertropia at the lateral gaze to the left and to the right or at positions of head tilt to either right or left,

–Asymmetric overaction of the inferior oblique.

Overaction of the inferior oblique has been graded from 1 to 4 , and the exyclotorsion has been measured with Maddox double rods.

The etiology of the bilateral paralysis of the inferior oblique was either congenital due to the disease history of the patients or was suspected considering the existence of the head-tilt for a long time and or a wide amplitude of vertical fusion.

Symmetric surgery as bilateral myectomy of the oblique inferior has been applied in 11 cases and asymmetric surgery as myectomy of the inferior oblique along with a recession of the most overacting muscle due to the amount of the overaction of the less overacting inferior oblique.

3RESULTS

The cases have been followed for 3 to 72 months, the mean time of follow up being 22,75 20,34 months. The vertical deviations in primary position was measured before the operation between 5 and 20 PD. A residual vertical deviation lower than 5 PD in primary position has been noted among 7 patients in the group of patients who have been treated by symmetric surgery and in 8 patients who have undergone the asymmetric surgery. No significant difference has been observed between these two groups of patients regarding the vertical deviation (p 0,62) while a residual overaction of the inferior oblique has been present in 7 patients of the group of symmetric surgery and 2 patients of the other, and a significant difference existed regarding the overaction of the inferior oblique (p 0,02).

4DISCUSSION

In this study the procedure of weakening of the inferior oblique has been selected due to the amount of the overaction and recession of the inferior oblique which has been applied in cases presenting a mild ( ) or moderate ( ) overaction, and a myectomy to those with an overaction of the inferior oblique of ( ) or ( ).

It has been reported that the marginal myotomy leads to satisfactory results for unilateral vertical deviations under 6°, and less satisfactory results over it (10). Additionally in a group of 6 patients presenting an asymmetric overaction of the inferior oblique with paralysis of the superior oblique showing a hyperdeviation in primary position, only one sucessful result has been obtained although various procedures have been applied (1). However in a work of Mellott and collaborators, an asymmetric surgery, as the marginal myotomy to the oblique inferior showing a moderate overaction and a myectomy or recession to the most overacting inferior oblique, 9 of 10 cases have resulted satisfactorily with a residual hypertropia of less than 5 PD at primary position (11). As we applied an asymmetric surgery concerning the recession of inferior oblique muscle with a moderate overaction, along with the myectomy of the most overacting, we have also obtained satisfactory results. Only 2 out of 13 cases had a residual hyperdeviation of more than 5 PD in primary position.

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In the same study of Mellott et al, following an asymmetric surgery, 5 cases out of 10 have presented a residual overaction while we noted a residual overaction in 5 of 13 cases after asymmetric surgery (11).

In the two groups of surgery of our study no significant difference with respect to the vertical deviation was present.

Many methods with a variable degree of success have been proposed for the treatment of the bilateral paralysis of the superior oblique with unequivalent overaction of the inferior oblique (4,9). The procedures of symmetric weakening of the inferior oblique do not eliminate the vertical deviation in primary position and an intervention on a third vertical muscle may be necessary. Therefore, some authors have proposed an unequivalent recession of the inferior oblique (12). But these experiences have shown that unequivalent recession of the inferior oblique is not sufficient for the elimination of the vertical deviation in primary position. In concordance with with these observations, recession of the controlateral inferior oblique has been carried in two cases along with the symmetric surgery and a postoperatory vertical deviation 10 PD has been obtained. Only one of 13 cases required such an intervention in the group of asymmetric surgery.

Among the 11 cases of paralysis of the superior oblique superior showing a overaction of the inferior oblique in whom a symmetric surgery has been realised, 4 showed a residual overaction of the inferior oblique which has also been observed in 2 of 13 cases having undergone an asymmetric surgery. The fact that we obtained better results with the asymmetric surgery appears to be rather sensible due to the fact that we directly aimed at the pathology from which the asymmetry has been originated (4,11).

In conclusion in the cases of asymmetric paralysis of the superior oblique showing an asymmetric overaction of the inferior oblique no difference existed in two methods of surgery, as symmetric and asymmetric, regarding the vertical deviation in primary position, whereas in respect with the residual overaction of the inferior oblique the results of the asymmetric surgery were more satisfactory than those of the symmetric one.

REFERENCES

1. Scott WE, Kraft SP. Classification and treatment of superior oblique palsies: II. Bilateral superior oblique palsies. In: Transactions of the New Orleans Academy of Ophthalmology. New York, New York Raven Press; 1986. pp 265–91

2. von Noorden GK. Binocular Vision and Ocular Motility. St.Louis, Mosby, 6th edition. 2002; 434. 3. Urist MJ. Bilateral superior oblique paralysis. Arch ophthalmol 1953; 49: 382

4. Souza Dias C. Surgical management of superior oblique paresis. In: Moore S, Mein J and Stocbridge L(eds). Ortoptics: Past, present and future. Miami, Symposia specialists, 1976, pp: 379–92

5. Hugonnier R. See-saw paralysis of the superior oblique muscle. In: Transactions of the second congress of international Strabismological association. Marseilles, Diffusion Gejal Libraire, 1976. pp. 120–22.

6. Hermann JS. Masked bilateral superior oblique paresis. J Pediatr Ophthalmol Strabismus 1981; 18: 43 7. Kraft SP, Scott WE. Masked bilateral superior oblique palsy. Clinical features and diagnosis. J Pediatr

Ophthalmol 1986; 23: 264.

8. Jampolsky A. Vertical strabismus surgery. Trans New Orleans Acad Ophthalmol 1971, p. 366

9. Parks MM. A study of the weakening procedures for eliminating overaction of the inferior oblique muscle. Am J Ophthalmol 1972; 73: 107–22

10. De Decker W, Kueper J. Inferior oblique weakening by marginal myotomy: thermo-electric weakening. Ann Ophthalmol 1973; 5: 605–13.

11. Mellott ML, Scott WE, Ganser GL, Keech RV. Marginal myotomy of the minimally overacing Inferior

Oblique Muscle In Asymmetric Biateral Superior Oblique Palsies. JAAPOS 2002; 6: 216–20. 12. Chamberlain W. Inferior oblique recession operation. Int J Ophthalmol Clin 1971; 11: 129–31.

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