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Acquired Toxoplasmic Infection as the Cause of Toxoplasmic Retinochoroiditis in Families
362
September, 1988
AMERICAN JOURNAL OF OPHTHALMOLOGY
w h o d e v e l o p e d e n d o p h t h a l m i t i s after a cat s c r a t c h e d t h e cornea of his eye, 1 a n d a 51-yearold m a n w h o suffered e n d o p h t h a l m i t i s from a cat bite that p e n e t r a t e d his globe. 2 A t h r e e - y e a r r e t r o s p e c t i v e s t u d y of infectious e n d o p h t h a l mitis from a tertiary referral c e n t e r r e p o r t e d o n e case c a u s e d by Pasteurella species after corneal laceration by a cat. 5 Analysis of Pasteu rella infections not related to a n i m a l bites s h o w s four ocular infections d u r i n g a 3 4 - m o n t h p e r i o d . T h e s e i n c l u d e two cases of conjunctivi tis, o n e case each of keratitis a n d a n t e r i o r uveitis, a n d o n e case of p r o p t o s i s w i t h p a n s i nusitis e r o d i n g into t h e orbit. 6 Bacteremia is a n i n f r e q u e n t complication of Pasteurella infec t i o n s , b u t w h e n f o u n d , it often occurs in i m m u n o c o m p r o m i s e d p a t i e n t s w i t h cirrhosis or ma lignancy. C o m m o n s o u r c e s of b a c t e r e m i a i n c l u d e i n t r a - a b d o m i n a l infection, m e n i n g i t i s , p n e u m o n i t i s , a n d soft tissue infections. 7 Skin infections w i t h P. multocida evoke a n i n t e n s e i n f l a m m a t o r y r e s p o n s e w i t h m u c h local e r y t h e ma, w a r m t h , swelling, a n d t e n d e r n e s s . T r e a t m e n t of p r e v i o u s l y r e p o r t e d ocular in fections i n c l u d e d medical a n d surgical inter v e n t i o n . Galloway a n d R o b i n s o n 3 d e s c r i b e d a t r e a t m e n t r e g i m e n of topical a n d s y s t e m i c a n t i biotics. Their p a t i e n t u n d e r w e n t e n u c l e a t i o n at 16 d a y s b e c a u s e of c o n t i n u e d fever. Purcell a n d Krachmer 4 u s e d topical t h e r a p y w i t h p r e s e r v a tion of t h e eye, b u t corneal scarring, cataract formation, a n d d e c r e a s e d visual acuity result ed. Weber a n d associates 1 r e p o r t e d p r e s e r v e d vision after topical a n d systemic antibiotics w e r e u s e d . Yokoyama a n d associates 2 u s e d ag gressive surgical m a n a g e m e n t t o g e t h e r w i t h systemic a n d intravitreal antibiotics t h a t led to a visual acuity of 40/200 in their p a t i e n t . O u r p a t i e n t r e s p o n d e d to i n t r a v e n o u s a n d topical antibiotics. Pasteurella multocida is s u s c e p t i b l e to m o s t antibiotics i n c l u d i n g penicillin G, the c e p h a l o s p o r i n s , ticarcillin, piperacillin s o d i u m , chlor a m p h e n i c o l , tetracycline, a n d g e n t a m i c i n . The antibiotic of choice is penicillin or ticarcillin. In p a t i e n t s allergic to penicillin, c h l o r a m p h e n i c o l or tetracycline are useful a l t e r n a t i v e s . T h e u n u s u a l a s p e c t of this case w a s t h e isola tion of P. multocida from the blood a n d t h e d i s c h a r g e from t h e eye in t h e a b s e n c e of a n o p e n w o u n d . A d d i t i o n a l l y , only t h e eye w i t h t h e i n t r a o c u l a r lens i m p l a n t w a s involved w i t h infection. This case e x t e n d s the s p e c t r u m of ocular infections c a u s e d by P. multocida to in clude orbital a n d periorbital cellulitis. Early a d m i n i s t r a t i o n of antibiotics r e s u l t e d in a favor
able o u t c o m e for o u r p a t i e n t . O c u l a r infection w i t h P. multocida is m o s t likely c a u s e d by a n a n i m a l scratch or lick over t h e eye, a n e v e n t often o v e r l o o k e d by p a t i e n t s . Pasteurella multocida s h o u l d b e c o n s i d e r e d in t h e differen tial d i a g n o s i s of ocular infections a n d a h i s t o r y of c o n t a c t w i t h a n i m a l s s h o u l d be o b t a i n e d .
References 1. Weber, D. J., Wolfson, J. S., Swartz, M. N., and Hooper, D. C : Pasteurella multocida infections. Re port of 34 cases and review of the literature. Medi cine 63:133, 1984. 2. Yokoyama, T., Hara, S., Funakubo, H., and Sato, N.: Pasteurella multocida endophthalmitis after a cat bite. Ophthalmic Surg. 18:520, 1987. 3. Galloway, N. A., and Robinson, G. E.: Panophthalmitis due to Pasteurella septica. Br. J. Ophthalmol. 57:153, 1973. 4. Purcell, J. J., Jr., and Krachmer, J. H.: Corneal ulcer caused by Pasteurella multocida. Am. J. Ophthal mol. 83:540, 1977. 5. Puliafito, C. A., Baker, A. S., Haaf, J., and Foster, C. S.: Infectious endophthalmitis. Review of 36 cases. Ophthalmology 89:921, 1982. 6. Hubbert, W. T., and Rosen, M. N.: Pasteurella multocida infection in man unrelated to animal bite. Am. J. Public Health 60:1109, 1970. 7. Raffi, F., Barrier, J., Baron, D., Drugeon, H. B., Nicolas, F., and Courtieu, A. L.: Pasteurella multocida bacteremia. Report of 13 cases over 12 years and review of the literature. Scand. J. Infect. Dis. 19:385, 1987.
Acquired Toxoplasmic Infection as the Cause of Toxoplasmic Retinochoroiditis in Families Claudio Silveira, M . D . , R u b e n s B e l f o r t , Jr., M . D . , M i g u e l B u r n i e r , Jr., M . D . , and Robert Nussenblatt, M . D . Clinica Silveria (C.S.); Departments of Ophthalmolo gy and Pathology, Escola Paulista de Medicina (R.B. and M.B.); and the National Eye Institute, National Institutes of Health (R.N.). Inquiries to Rubens Belfort, Jr., M.D., Caixa Postal 4086, CEP 01051 Sao Paulo, Brazil. T h e p r e s e n c e of active or inactive focal toxo p l a s m i c r e t i n o c h o r o i d i t i s reflects a c o n g e n i t a l
Vol. 106, No. 3
Letters to the Journal
infection in essentially all cases, 1 and occurs in the fetus only when the mother acquires active disease during pregnancy. Subsequent siblings are thought to be protected by the mother's acquired immunologic defense mechanism. Therefore, one would not expect the siblings of a child with ocular toxoplasmosis to be at risk of contracting the same ocular disease. 2 Ocular toxoplamosis comprises approximate ly 50% of all uveitis seen in Brazil. Familial ocular toxoplasmosis is frequently observed in the southern part of Brazil (Alto Uruguai re gion) where the ingestion of raw pork contami nated with toxoplasmic cysts is common, which causes repeated reinfection. 3 We studied the occurrence of ocular toxoplas mosis in 112 families from the city of Erexim (Rio Grande do Sul, Brazil). All patients had positive serologic findings for toxoplasmosis, a clinical picture typical of ocular toxoplasmosis with a necrotizing retinochoroiditis often asso ciated with satellite lesions, and the exclusion of other known causes of focal retinochoroidi tis, such as syphilis and tuberculosis. Various familial patterns of ocular toxoplas mosis have been noted, including a mother and one child in nine families; a mother and two children in one family; a mother and three children in four families; a mother and four children in one family; a mother and six chil dren in one family; and a mother and eight children in one family. Ocular toxoplasmosis was present also in two siblings of 60 families, three siblings in 18 families, four siblings in six families, five siblings in three families, and six siblings in four families. All of these families had nontwin siblings. The clinical picture typi cal of ocular toxoplasmosis has been seen also in three successive generations of female pa tients in some of the families (Fig. 1). A large number of toxoplasma cysts have been identified in the retinas of enucleated eyes
Fig. 1 (Silveira and associates). Family with ocular toxoplasmosis in the mother, seven sons, one daugh ter, and one granddaughter. The fully blackened symbols denote bilateral disease, while the half blackened square denotes unilateral disease.
363
eosin, x 1,000). from two nontwin siblings with ocular toxo plasmosis (Fig. 2).4 The rate of miscarriage in this population is similar to that observed in other parts of Brazil. A survey of 100 children 10 to 15 years of age in a public school of Erexim showed that only two did not have serum antibodies to toxoplasmo sis. Many of them also had IgM serum antibod ies to the parasite, suggesting a recently ac quired infection. The evaluation of patients with acute necro tizing retinochoroiditis for circulating IgM antitoxoplasma antibodies has shown positive results in several of these patients. In other cases, patients with ocular toxoplasmosis had a past episode of systemic toxoplasmosis proven by positive IgM antibodies to the organism. In most patients, the systemic disease was rela tively mild, characterized by a flu-like episode associated with lymphadenopathy. We have examined three other families with homozygotic twins where ocular toxoplasmosis was found only in the eye of one of the twins. Serum IgG antitoxoplasma antibodies were found only in the twins with the retinal lesions. The meaning of these observations is not totally clear. This may be a highly unusual congenital form of the disease or more likely, it is evidence of the important role of acquired Toxoplasma infection in the pathogenesis of this ocular disease. This latter explanation has also been suggested by Ziobrowski. 5 We can only summarize that the incidence of acquired subclinical toxoplasmic infection that causes late, or recurrent necrotizing retinocho roiditis is probably much more frequent than previously believed.
364
AMERICAN JOURNAL OF OPHTHALMOLOGY
September, 1988
References 1. Perkins, E. S.: Ocular toxoplasmosis. Br. J. Ophthalmol. 57:1, 1973. 2. Sunness, J. S.: The pregnant woman's eye. Surv. Ophthalmol. 32:219, 1988. 3. Silveira, C. S., Belfort, R., Jr., and Burnier, M., Jr.: Toxoplasmose ocular. Identificacao de cistos de Toxoplasma gondii na retina de irmaos gemeos com diagnostico de toxoplasmose ocular recidivante. Primeiro caso mundial. Arq. Bras. Oftalmol. 50:215, 1987. 4. Silveira, C , Belfort, R., Jr., Burnier, M , Jr., Nussenblatt, R., Martins, M. C , Jamra, L., Rigueiro, M., Imamura, P., and Takahashi, W.: New findings in ocular toxoplasmosis. Arq. Bras. Oftalmol. 51:25, 1988. 5. Ziobrowski, S.: Familial occurrence of toxoplas mosis. Klin. Oczma. 87:210, 1985.
A Technique for Repairing Strabismus After Scleral Buckling Surgery Robert A. Mallette, M.D., Jung Yoon Kwon, M.D., and David L. Guyton, M.D. Wilmer Ophthalmological Institute, the Johns Hop kins University School of Medicine. Presented in part as a poster exhibit at the annual meeting of the American Association of Pediatric Ophthalmology and Strabismus, May 18, 1988, Boston, Massachu setts. Inquiries to David L. Guyton, M.D., Wilmer Institute, Bl-35, Johns Hopkins Hospital, Baltimore, MD 21205. Repair of s t r a b i s m u s after scleral b u c k l i n g can be difficult a n d u n p r e d i c t a b l e b e c a u s e of scar t i s s u e a n d interference by t h e i m p l a n t e d material w i t h c u s t o m a r y surgical t e c h n i q u e s . We describe a simplified t e c h n i q u e for repair ing s t r a b i s m u s after scleral b u c k l i n g p r o c e d u r e s . This t e c h n i q u e offers a d v a n t a g e s over previously described approaches.1,2 A cul-de-sac conjunctival incision is m a d e in t h e a p p r o p r i a t e scleral q u a d r a n t in a n a r c , par allel to t h e folds of t i s s u e in t h e fornix. Dissec tion t h r o u g h T e n o n ' s c a p s u l e is carried d o w n to t h e b a r e sclera p o s t e r i o r to t h e b u c k l e , b e i n g careful n o t to d i s t u r b t h e fibrous c a p s u l e sur r o u n d i n g t h e e x o p l a n t . T h e m u s c l e is t h e n isolated w i t h a m u s c l e h o o k p o s t e r i o r to t h e e x o p l a n t , l e a v i n g intact t h e fibrous scar tissue
Figure (Mallette, Kwon, and Guyton). Surgical procedure, avoiding the fibrous capsule surrounding the exoplant. Top, Exposure of the "new insertion" at the posterior edge of the capsule surrounding the exoplant. A double-armed 6-0 Vicryl suture secures the muscle before tenotomy. Middle, For recession, the sutures are passed anterior to the original inser tion of the muscle, and the muscle is allowed to hang back a measured amount from its original position. The sutures are brought out through the conjunctiva, and a noose is placed around them for later adjust ment. Bottom, For advancement, the disinserted muscle is advanced the desired amount over the scar tissue/muscle stump. Alternatively, a straightfor ward resection may be done with advancement of the resected margin to the posterior edge of the buckle. In either case the sutures course forward over the old muscle stump.
September, 1988
AMERICAN JOURNAL OF OPHTHALMOLOGY
w h o d e v e l o p e d e n d o p h t h a l m i t i s after a cat s c r a t c h e d t h e cornea of his eye, 1 a n d a 51-yearold m a n w h o suffered e n d o p h t h a l m i t i s from a cat bite that p e n e t r a t e d his globe. 2 A t h r e e - y e a r r e t r o s p e c t i v e s t u d y of infectious e n d o p h t h a l mitis from a tertiary referral c e n t e r r e p o r t e d o n e case c a u s e d by Pasteurella species after corneal laceration by a cat. 5 Analysis of Pasteu rella infections not related to a n i m a l bites s h o w s four ocular infections d u r i n g a 3 4 - m o n t h p e r i o d . T h e s e i n c l u d e two cases of conjunctivi tis, o n e case each of keratitis a n d a n t e r i o r uveitis, a n d o n e case of p r o p t o s i s w i t h p a n s i nusitis e r o d i n g into t h e orbit. 6 Bacteremia is a n i n f r e q u e n t complication of Pasteurella infec t i o n s , b u t w h e n f o u n d , it often occurs in i m m u n o c o m p r o m i s e d p a t i e n t s w i t h cirrhosis or ma lignancy. C o m m o n s o u r c e s of b a c t e r e m i a i n c l u d e i n t r a - a b d o m i n a l infection, m e n i n g i t i s , p n e u m o n i t i s , a n d soft tissue infections. 7 Skin infections w i t h P. multocida evoke a n i n t e n s e i n f l a m m a t o r y r e s p o n s e w i t h m u c h local e r y t h e ma, w a r m t h , swelling, a n d t e n d e r n e s s . T r e a t m e n t of p r e v i o u s l y r e p o r t e d ocular in fections i n c l u d e d medical a n d surgical inter v e n t i o n . Galloway a n d R o b i n s o n 3 d e s c r i b e d a t r e a t m e n t r e g i m e n of topical a n d s y s t e m i c a n t i biotics. Their p a t i e n t u n d e r w e n t e n u c l e a t i o n at 16 d a y s b e c a u s e of c o n t i n u e d fever. Purcell a n d Krachmer 4 u s e d topical t h e r a p y w i t h p r e s e r v a tion of t h e eye, b u t corneal scarring, cataract formation, a n d d e c r e a s e d visual acuity result ed. Weber a n d associates 1 r e p o r t e d p r e s e r v e d vision after topical a n d systemic antibiotics w e r e u s e d . Yokoyama a n d associates 2 u s e d ag gressive surgical m a n a g e m e n t t o g e t h e r w i t h systemic a n d intravitreal antibiotics t h a t led to a visual acuity of 40/200 in their p a t i e n t . O u r p a t i e n t r e s p o n d e d to i n t r a v e n o u s a n d topical antibiotics. Pasteurella multocida is s u s c e p t i b l e to m o s t antibiotics i n c l u d i n g penicillin G, the c e p h a l o s p o r i n s , ticarcillin, piperacillin s o d i u m , chlor a m p h e n i c o l , tetracycline, a n d g e n t a m i c i n . The antibiotic of choice is penicillin or ticarcillin. In p a t i e n t s allergic to penicillin, c h l o r a m p h e n i c o l or tetracycline are useful a l t e r n a t i v e s . T h e u n u s u a l a s p e c t of this case w a s t h e isola tion of P. multocida from the blood a n d t h e d i s c h a r g e from t h e eye in t h e a b s e n c e of a n o p e n w o u n d . A d d i t i o n a l l y , only t h e eye w i t h t h e i n t r a o c u l a r lens i m p l a n t w a s involved w i t h infection. This case e x t e n d s the s p e c t r u m of ocular infections c a u s e d by P. multocida to in clude orbital a n d periorbital cellulitis. Early a d m i n i s t r a t i o n of antibiotics r e s u l t e d in a favor
able o u t c o m e for o u r p a t i e n t . O c u l a r infection w i t h P. multocida is m o s t likely c a u s e d by a n a n i m a l scratch or lick over t h e eye, a n e v e n t often o v e r l o o k e d by p a t i e n t s . Pasteurella multocida s h o u l d b e c o n s i d e r e d in t h e differen tial d i a g n o s i s of ocular infections a n d a h i s t o r y of c o n t a c t w i t h a n i m a l s s h o u l d be o b t a i n e d .
References 1. Weber, D. J., Wolfson, J. S., Swartz, M. N., and Hooper, D. C : Pasteurella multocida infections. Re port of 34 cases and review of the literature. Medi cine 63:133, 1984. 2. Yokoyama, T., Hara, S., Funakubo, H., and Sato, N.: Pasteurella multocida endophthalmitis after a cat bite. Ophthalmic Surg. 18:520, 1987. 3. Galloway, N. A., and Robinson, G. E.: Panophthalmitis due to Pasteurella septica. Br. J. Ophthalmol. 57:153, 1973. 4. Purcell, J. J., Jr., and Krachmer, J. H.: Corneal ulcer caused by Pasteurella multocida. Am. J. Ophthal mol. 83:540, 1977. 5. Puliafito, C. A., Baker, A. S., Haaf, J., and Foster, C. S.: Infectious endophthalmitis. Review of 36 cases. Ophthalmology 89:921, 1982. 6. Hubbert, W. T., and Rosen, M. N.: Pasteurella multocida infection in man unrelated to animal bite. Am. J. Public Health 60:1109, 1970. 7. Raffi, F., Barrier, J., Baron, D., Drugeon, H. B., Nicolas, F., and Courtieu, A. L.: Pasteurella multocida bacteremia. Report of 13 cases over 12 years and review of the literature. Scand. J. Infect. Dis. 19:385, 1987.
Acquired Toxoplasmic Infection as the Cause of Toxoplasmic Retinochoroiditis in Families Claudio Silveira, M . D . , R u b e n s B e l f o r t , Jr., M . D . , M i g u e l B u r n i e r , Jr., M . D . , and Robert Nussenblatt, M . D . Clinica Silveria (C.S.); Departments of Ophthalmolo gy and Pathology, Escola Paulista de Medicina (R.B. and M.B.); and the National Eye Institute, National Institutes of Health (R.N.). Inquiries to Rubens Belfort, Jr., M.D., Caixa Postal 4086, CEP 01051 Sao Paulo, Brazil. T h e p r e s e n c e of active or inactive focal toxo p l a s m i c r e t i n o c h o r o i d i t i s reflects a c o n g e n i t a l
Vol. 106, No. 3
Letters to the Journal
infection in essentially all cases, 1 and occurs in the fetus only when the mother acquires active disease during pregnancy. Subsequent siblings are thought to be protected by the mother's acquired immunologic defense mechanism. Therefore, one would not expect the siblings of a child with ocular toxoplasmosis to be at risk of contracting the same ocular disease. 2 Ocular toxoplamosis comprises approximate ly 50% of all uveitis seen in Brazil. Familial ocular toxoplasmosis is frequently observed in the southern part of Brazil (Alto Uruguai re gion) where the ingestion of raw pork contami nated with toxoplasmic cysts is common, which causes repeated reinfection. 3 We studied the occurrence of ocular toxoplas mosis in 112 families from the city of Erexim (Rio Grande do Sul, Brazil). All patients had positive serologic findings for toxoplasmosis, a clinical picture typical of ocular toxoplasmosis with a necrotizing retinochoroiditis often asso ciated with satellite lesions, and the exclusion of other known causes of focal retinochoroidi tis, such as syphilis and tuberculosis. Various familial patterns of ocular toxoplas mosis have been noted, including a mother and one child in nine families; a mother and two children in one family; a mother and three children in four families; a mother and four children in one family; a mother and six chil dren in one family; and a mother and eight children in one family. Ocular toxoplasmosis was present also in two siblings of 60 families, three siblings in 18 families, four siblings in six families, five siblings in three families, and six siblings in four families. All of these families had nontwin siblings. The clinical picture typi cal of ocular toxoplasmosis has been seen also in three successive generations of female pa tients in some of the families (Fig. 1). A large number of toxoplasma cysts have been identified in the retinas of enucleated eyes
Fig. 1 (Silveira and associates). Family with ocular toxoplasmosis in the mother, seven sons, one daugh ter, and one granddaughter. The fully blackened symbols denote bilateral disease, while the half blackened square denotes unilateral disease.
363
eosin, x 1,000). from two nontwin siblings with ocular toxo plasmosis (Fig. 2).4 The rate of miscarriage in this population is similar to that observed in other parts of Brazil. A survey of 100 children 10 to 15 years of age in a public school of Erexim showed that only two did not have serum antibodies to toxoplasmo sis. Many of them also had IgM serum antibod ies to the parasite, suggesting a recently ac quired infection. The evaluation of patients with acute necro tizing retinochoroiditis for circulating IgM antitoxoplasma antibodies has shown positive results in several of these patients. In other cases, patients with ocular toxoplasmosis had a past episode of systemic toxoplasmosis proven by positive IgM antibodies to the organism. In most patients, the systemic disease was rela tively mild, characterized by a flu-like episode associated with lymphadenopathy. We have examined three other families with homozygotic twins where ocular toxoplasmosis was found only in the eye of one of the twins. Serum IgG antitoxoplasma antibodies were found only in the twins with the retinal lesions. The meaning of these observations is not totally clear. This may be a highly unusual congenital form of the disease or more likely, it is evidence of the important role of acquired Toxoplasma infection in the pathogenesis of this ocular disease. This latter explanation has also been suggested by Ziobrowski. 5 We can only summarize that the incidence of acquired subclinical toxoplasmic infection that causes late, or recurrent necrotizing retinocho roiditis is probably much more frequent than previously believed.
364
AMERICAN JOURNAL OF OPHTHALMOLOGY
September, 1988
References 1. Perkins, E. S.: Ocular toxoplasmosis. Br. J. Ophthalmol. 57:1, 1973. 2. Sunness, J. S.: The pregnant woman's eye. Surv. Ophthalmol. 32:219, 1988. 3. Silveira, C. S., Belfort, R., Jr., and Burnier, M., Jr.: Toxoplasmose ocular. Identificacao de cistos de Toxoplasma gondii na retina de irmaos gemeos com diagnostico de toxoplasmose ocular recidivante. Primeiro caso mundial. Arq. Bras. Oftalmol. 50:215, 1987. 4. Silveira, C , Belfort, R., Jr., Burnier, M , Jr., Nussenblatt, R., Martins, M. C , Jamra, L., Rigueiro, M., Imamura, P., and Takahashi, W.: New findings in ocular toxoplasmosis. Arq. Bras. Oftalmol. 51:25, 1988. 5. Ziobrowski, S.: Familial occurrence of toxoplas mosis. Klin. Oczma. 87:210, 1985.
A Technique for Repairing Strabismus After Scleral Buckling Surgery Robert A. Mallette, M.D., Jung Yoon Kwon, M.D., and David L. Guyton, M.D. Wilmer Ophthalmological Institute, the Johns Hop kins University School of Medicine. Presented in part as a poster exhibit at the annual meeting of the American Association of Pediatric Ophthalmology and Strabismus, May 18, 1988, Boston, Massachu setts. Inquiries to David L. Guyton, M.D., Wilmer Institute, Bl-35, Johns Hopkins Hospital, Baltimore, MD 21205. Repair of s t r a b i s m u s after scleral b u c k l i n g can be difficult a n d u n p r e d i c t a b l e b e c a u s e of scar t i s s u e a n d interference by t h e i m p l a n t e d material w i t h c u s t o m a r y surgical t e c h n i q u e s . We describe a simplified t e c h n i q u e for repair ing s t r a b i s m u s after scleral b u c k l i n g p r o c e d u r e s . This t e c h n i q u e offers a d v a n t a g e s over previously described approaches.1,2 A cul-de-sac conjunctival incision is m a d e in t h e a p p r o p r i a t e scleral q u a d r a n t in a n a r c , par allel to t h e folds of t i s s u e in t h e fornix. Dissec tion t h r o u g h T e n o n ' s c a p s u l e is carried d o w n to t h e b a r e sclera p o s t e r i o r to t h e b u c k l e , b e i n g careful n o t to d i s t u r b t h e fibrous c a p s u l e sur r o u n d i n g t h e e x o p l a n t . T h e m u s c l e is t h e n isolated w i t h a m u s c l e h o o k p o s t e r i o r to t h e e x o p l a n t , l e a v i n g intact t h e fibrous scar tissue
Figure (Mallette, Kwon, and Guyton). Surgical procedure, avoiding the fibrous capsule surrounding the exoplant. Top, Exposure of the "new insertion" at the posterior edge of the capsule surrounding the exoplant. A double-armed 6-0 Vicryl suture secures the muscle before tenotomy. Middle, For recession, the sutures are passed anterior to the original inser tion of the muscle, and the muscle is allowed to hang back a measured amount from its original position. The sutures are brought out through the conjunctiva, and a noose is placed around them for later adjust ment. Bottom, For advancement, the disinserted muscle is advanced the desired amount over the scar tissue/muscle stump. Alternatively, a straightfor ward resection may be done with advancement of the resected margin to the posterior edge of the buckle. In either case the sutures course forward over the old muscle stump.