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Year : 2019  |  Volume : 57  |  Issue : 3  |  Page : 233-236

Augmented inverse knapp procedure with inferior rectus plication – A treatment option for large hypertropia

Department of Pediatric Ophthalmology and Strabismus, Aravind Eye Hospital, Coimbatore, Tamil Nadu, India

Date of Submission02-May-2019
Date of Acceptance09-Jul-2019
Date of Web Publication11-Nov-2019

Correspondence Address:
Dr. D S Srushti
No. 21, Department of Pediatric Ophthalmology and Strabismus, Aravind Eye Hospital, Coimbatore, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjosr.tjosr_42_19

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In this case report, we present a novel surgical technique of combining horizontal recess–resect procedure with an inverse Knapp procedure and augmenting the desired effect using augmentation sutures. Apart from improvement in the field of binocular vision, this procedure had the added advantage of preserving the anterior ciliary circulation by involving not more than two rectus muscles (inferior rectus plication being a vessel-sparing procedure). This could be a helpful option in large hypertropia with negative forced duction/generation test (for vertical recti).

Keywords: Augmentation sutures, diplopia, hypertropia, inferior rectus paresis, inverse Knapp procedure

How to cite this article:
Ganesh SC, Srushti D S, Ramawat E, Narendran K. Augmented inverse knapp procedure with inferior rectus plication – A treatment option for large hypertropia. TNOA J Ophthalmic Sci Res 2019;57:233-6

How to cite this URL:
Ganesh SC, Srushti D S, Ramawat E, Narendran K. Augmented inverse knapp procedure with inferior rectus plication – A treatment option for large hypertropia. TNOA J Ophthalmic Sci Res [serial online] 2019 [cited 2023 Feb 3];57:233-6. Available from: https://www.tnoajosr.com/text.asp?2019/57/3/233/270689

  Introduction Top

Inverse Knapp procedure is performed to correct hypertropia of various etiologies. There are very few reports available[1],[2],[3],[4] documenting its efficacy. We report the successful surgical alignment and diplopia relief achieved in a patient with acquired hypertropia due to inferior rectus (IR) palsy with augmented inverse Knapp procedure combined with IR plication.

  Case Report Top

A 28-year-old man presented to our strabismus clinic with a chief complaint of misalignment of his eyes and binocular double vision in all gazes following injury to his right eye (RE) with a cricket ball 2 years ago. He was diagnosed then with right orbital floor fracture with orbital imaging suggestive of impingement of IR muscle within the fracture. The fracture repair was done soon after with IR muscle release, but his complaints persisted as before.

On examination, his uncorrected Snellen visual acuity was 6/6 in either eye. Hirschberg corneal reflex test showed right exotropia (RXT) 15° with right hypertropia (RHT) 15° [Figure 1]. Prism cover test (PCT) measured a primary deviation of RXT 35 PD with RHT 30 PD in primary gaze for distance and RXT 35 PD and RHT 45 PD in downgaze. He had a −4 limitation of his RE to dextrodepression and a +3 overaction on dextroelevation and normal horizontal versions. Hess charting showed marked underaction of right IR action with secondary overaction of the right superior rectus muscle. Crossed vertical diplopia was demonstrated on Worth 4-dot test for distance and near. Anterior segment evaluation of both eyes including pupil reactions was normal. He was diagnosed to have RXT and RHT due to IR palsy post trauma. Forced duction test showed no restriction to depression or elevation of his RE, and forced generation test was negative for right IR action. He was posted for surgical correction as he wanted diplopia relief and improved cosmesis.
Figure 1: Preoperative 9-gaze photograph. Note the exotropia and hypertropia in primary gaze and the − 4 limitation to dextrodepression (circled)

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Under sub-Tenon's block, after limbal peritomy, a recess–resect procedure of the horizontal recti muscles (7/5) was done, along with full-tendon transfer (infraplacement) of both the muscle insertions along the spiral of Tillaux (inverse Knapp procedure). The resected edge of medial rectus was refixed to the sclera such that its inferior edge was close to the nasal side of IR insertion and its superior edge near the inferior stump of its original insertion. The lateral rectus was recessed by 7 mm and infraplaced lateral to IR muscle. The IR muscle was then plicated by 3 mm. Since the hypertropia was large, the infraplacement effect was further augmented using a nonabsorbable 5-0 Ethibond (polyethylene terephthalate) suture passed through the belly of horizontal recti and IR muscle, 15 mm from the limbus, including one-third thickness of the muscles and not including the sclera. The conjunctiva was then closed with 8-0 Vicryl (polyglactin) sutures [Figure 2].
Figure 2: Steps of surgery. (a and b) LR recessed and infraplaced. (c and d) MR resected and infraplaced. (e and f) Augmentation suture between MR and inferior rectus (black arrow). (g and h) Augmentation suture between LR and inferior rectus (black arrow). (i-k) plication of the inferior rectus

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On the first postoperative day, the patient was diplopia free in primary gaze. PCT measured R(X) 5 PD/R (H) 9 PD in primary gaze (6 m target) and RHT 20 PD in reading position. There was an improvement in depression, and he had a −2 limitation to dextrodepression.

At postoperative follow-up visit (1- month post surgery), he maintained orthotropia. PCT measured R(H) 5 PD for distance in primary gaze and RHT 15 PD in downgaze. He had a mild (-2) limitation of his RE to dextrodepression. He was diplopia free in all gazes except in downgaze [Figure 3].
Figure 3: Postoperative 9-gaze photograph – note the orthophoria in primary gaze and the improvement in dextrodepression (−2)

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  Discussion Top

Classically, the inverse Knapp procedure has been described by Cooper and Greenspan[5] and Dunlap[6] for the treatment of congenital depressor deficiency and double depressor underaction, respectively. This procedure is also described for the treatment of congenital or acquired IR paresis.[1],[2],[7]

A large retrospective case review on inverse Knapp procedure was published by Lee et al. Seventeen case records were identified, 9 with ocular trauma. He reported a significant improvement in mean vertical primary deviation from 16.06 PD (preoperative) to 7.35 PD (postoperative), and a similar improvement was also noted in downgaze. The authors recommended this for complete palsy of IR, either congenital or acquired, and for large residual hypertropia in patients who have poor binocular vision. They did not recommend this procedure for IR paresis due to risk of overcorrection. In this situation, a recess–resect of vertical recti is recommended.

Another advantage of the inverse Knapp procedure is the improvement in the binocular field of vision in primary position, downgaze, and surprisingly, also in upgaze, as documented by Lipton et al.[1] Using the Woodruff scoring template, they showed that the field of binocular single vision increases from an average of 31% (4%–68%) presurgery to 52% (16%–84%) 1 week postsurgery for the complete field.[8]

We had performed a recess–resect procedure along with “inverse Knapp” to correct the horizontal misalignment and also included augmentation sutures and IR plication. IR plication was chosen over resection for reversibility and to preserve anterior ciliary circulation. This patient did not show any sign of anterior segment ischemia in his follow-up visits. Although this was a case of total palsy of IR, we did a plication just for a presumed mechanical advantage limiting elevation, thus contributing for hypertropia correction. We analyzed that if there was a postoperative overcorrection, the augmentation and/or the plication could be easily cut and reversed. This was not required as our patient had a good cosmetic and functional outcome.

In conclusion, “inverse Knapp” procedure with augmentation and/or plication of IR can be considered as a good vessel sparing and reversible treatment option in selective cases of largely acquired hypertropia, with good outcomes.

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 Top

Lipton JR, Page AB, Lee JP. Management of diplopia on down-gaze following orbital trauma. Eye (Lond) 1990;4 (Pt 4):535-7.  Back to cited text no. 1
Burke JP, Keech RV. Effectiveness of inferior transposition of the horizontal rectus muscles for acquired inferior rectus paresis. J Pediatr Ophthalmol Strabismus 1995;32:172-7.  Back to cited text no. 2
Maurino V, Kwan AS, Lee JP. Review of the inverse knapp procedure: Indications, effectiveness and results. Eye (Lond) 2001;15:7-11.  Back to cited text no. 3
Metz HS. Saccades with limited downward gaze. Arch Ophthalmol 1980;98:2204-5.  Back to cited text no. 4
Cooper EL, Greenspan JA. Congenital absence of the inferior rectus muscle. Arch Ophthalmol 1971;86:451-4.  Back to cited text no. 5
Dunlap EA. Vertical displacement of the horizontal recti. Pac Med Surg 1964;72:360-2.  Back to cited text no. 6
Denning AM, Ansons AM, Spencer AL, Kranemann C. Does the degree of inferior rectus palsy influence the effectiveness of the inverse Knapp procedure? Trans Eur Strabismus Assoc 1997;24:97-102.  Back to cited text no. 7
Woodruff G, O'Reilly C, Kraft SP. Functional scoring of the field of binocular single vision in patients with diplopia. Ophthalmology 1987;94:1554-61.  Back to cited text no. 8


  [Figure 1], [Figure 2], [Figure 3]


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