[Morphological observation on the anterior ciliary vessels in the horizontal rectus muscles of patients with concomitant horizontal strabismus].

Objective: To observe the number of blood vessels and the anatomical characteristics of the anterior ciliary vessels (ACVs) in the horizontal rectus muscles of patients with concomitant horizontal strabismus. Methods: Cross-sectional study. From July 2016 to September 2019 patients with concomitant horizontal strabismus treated by realignment surgeries in Xiamen Eye Center of Xiamen University were included. Patients who had previous operations on eyes were excluded. The high resolution surgical imaging of ACVs in the horizontal rectus muscles was performed during operation. The photos of ACVs in muscles were tagged and observed to compare the distribution of the various numbers of blood vessels and morphological characteristics of the ACVs in the medial and lateral rectus muscles. In addition, muscle tissues about 4 mm with an intact sheath were gained from patients undergoing the muscle resection. The muscle sections were stained with hematoxylin-eosin staining, and the arteriovenous properties and their distribution in muscles and fascia tissues were observed. The chi-square test was used for statistical analysis. Results: A total of 387 patients with concomitant horizontal strabismus (176 with esotropia, 211 with exotropia) were enrolled in this study, among whom 198 were male and 189 were female. The age ranged from 1 to 68 years (median, 13 years). Photos of ACVs in 742 horizontal rectus muscles from 383 patients were observed. Of the 351 medial rectus muscles, 24 (6.8%) contained 1 major (or bundle of) ACV, 163 (46.4%) contained 2 major (or bundles of) ACVs, and 164 (46.7%) contained 3 or more major (or bundles of) ACVs. Of the 391 lateral rectus muscles, 161 (41.2%) contained 1 major (or bundle of) ACV, 156 (39.9%) contained 2 major (or bundles of) ACVs, and 74 (18.9%) contained 3 or more major (or bundles of) ACVs. The distribution of ACVs in the medial and lateral rectus muscles was statistically different (χ(2)=133.87, P< 0.01). According to the number and morphological characteristics of vessels, the ACVs in the medial and lateral rectus muscles were divided into 4 and 3 categories, respectively, as well as various types and subtypes. The rate of patients whose both eyes had the same type of ACVs in the medial or lateral rectus muscles was 31.6% (25/79) and 26.1% (29/111), respectively, and there was no significant difference (χ(2)=0.69, P= 0.41). However, the ACVs of the same type from both eyes of the same patient were not identical in morphology. The ACVs in the medial and lateral rectus muscles with collateral circulation accounted for 3.7% (13/351) and 24.3% (95/391), respectively, and the difference was statistically significant (χ(2)=63.07, P< 0.01). The hematoxylin-eosin staining of the medial lateral rectus tissues from 4 patients showed that the ACVs contained arteries and veins. The vessels in the medial rectus muscles were distributed in muscle tissue and fascia tissue, while the vessels in the lateral rectus muscles were only distributed in fascia tissue. Conclusions: Compared with the lateral rectus muscles, there are about 50% medial rectus muscles contain more than 3 major (or bundles of) vessels in patients with concomitant horizontal strabismus. The accompanying patterns of arteries and veins of ACVs are varied. ACVs are distributed in muscle tissue of the medial rectus muscles and in fascia tissue of the medial and lateral rectus muscles. (Chin J Ophthalmol, 2020, 56: 197-204) .