ORIGINAL ARTICLE Year : 2017  Volume : 110  Issue : 3  Page : 8993 Correlation between the axial length and the effect of recession of horizontal rectus muscles Manar A Ghali Department of Ophthalmology, Faculty of Medicine, Zagazig University, Zagazig, Egypt Correspondence Address: Purpose The aim of this study is to determine whether the axial length (AxL) measurement would be useful in predicting the effect of horizontal rectus muscles recession. Patients and methods This study retrospectively reviewed 94 patients (52 with intermittent exotropia and 42 with infantile esotropia and partially accommodative esotropia), with age ranging from 4 to 15 years (7.63±3.2). All cases underwent bilateral lateral rectus recession for exotropia and bilateral medial recession for esotropia; there were no cases of combined vertical strabismus. There was no history of any ocular trauma or previous strabismus surgery. Preoperative angle of deviation, AxL (IOL Master), and postoperative angle of deviation at 6 months were recorded; effect of recession was calculated in all cases. Results The mean AxL for all cases was 23.39±1.73. The patients were divided into two groups: exotropia group (n=52) and esotropia group (n=42). Each group was subdivided into two subgroups: subgroup I (AxL<23.39) and subgroup II (AxL≥23.39). The effect of recession in exotropic group was 2.27±0.29; in short AxL subgroup, it was 2.42±0.17, and in long AxL subgroup, it was 1.98±0.25. In esotropic group, the effect of recession was 3.36±0.53; in subgroup I, it was 3.67±0.31, and in subgroup II, it was 2.87±0.44. Conclusion The results showed a negative correlation between AxL and effect of recession in both esotropia and exotropia groups. It is recommended to increase the amount of recession in longer AxL.
Introduction The success of strabismus surgery is influenced by a number of preoperative factors [1],[2]. The results of surgery showed great variability among patients. The investigation of preoperative and intraoperative factors would help in planning a surgical intervention [3]. Bateman et al. [4] analyzed variables such as age of onset of deviation, age at surgery, interval between onset of deviation and surgery, and accommodative convergence to accommodation (AC/A) ratio. Among those variables, preoperative deviation was found to be the strongest predictor for both patients with esotropia and those with exotropia [3]. Kushner and Vrabec [5] reported evidence that response to strabismus surgery should correlate with axial length (AxL). Kushner et al. [6] reported significant negative correlation between AxL and response for patients with esotropia and poor correlation for patients with exotropia. Rah et al. [7] concluded that in long eyes, the surgical outcome of horizontal recti recession seems to be poor than short eyes in both esotropia and exotropia. Galantuomo et al. [8] showed that recession of extraocular muscles is more effective in larger eyes than in small ones. Because of this controversy in results between previous authors, our study aimed at assessing the influence of AxL on the surgical outcome of horizontal recti recession in children. Patients and methods This was a retrospective study that reviewed 94 patients with horizontal strabismus who underwent horizontal rectus recession in the period from January 2014 to June 2015 in the ophthalmology department of Zagazig University. Institutional review board approval for this study was obtained from Faculty of Medicine, Zagazig University. The patients’ ages ranged from 4 to 15 (7.63±3.2) years. The patients were divided into exotropia group (n=52), all of them having intermittent exotropia, and esotropia group (n=42), all of them being cases of infantile esotropia and partially accommodative type with normal AC/A ratio. Only patients who underwent symmetric bilateral recessions were included. All patients did not have combined vertical deviation with no history of any ocular trauma, previous squint surgery, and systemic diseases that could interfere with motility or amblyopia. Patients with anisometropia (>twodiopters difference between both eyes) and large angle of preoperative deviation of more than 55Δ were excluded. Complete ophthalmological examination included measuring preoperative angle of deviation at near and distance with the alternate prism and cover test when possible, and when not possible, using the Krimsky method while wearing their full corrective spectacles. AxL measurement using IOL Master (Carl Zeiss, Jena, Germany) was done for all patient preoperatively. Patients with AxL difference between both eyes of more than 0.5 mm were excluded. All patients underwent bilateral symmetric recessions surgery by the same surgeon (M.A.G.) to correct squint under general anesthesia based on surgical planning table, which is based on corrective previous tables according to surgeon experience ([Table 1]).{Table 1} In all operations, we performed the anchor hangback technique for muscle recession. Conjunctival limbal incision was made, and the muscle insertion was exposed after dissection of intermuscular septum and hooked, then the insertion was secured with 6/0 polyglactin (vicryl) double armed sutures (Ethicon Inc., Somerville, New Jersey, USA). Scleral bites were taken at the decided site of recession on each side of the muscle and then the muscle was disinserted, and the vicryl sutures were taken again and secured to muscle insertion and tied. Conjunctiva was sutured with 7/0 vicryl (Ethicon Inc.). All cases were followed up for at least 6 months postoperatively. The postoperative angle of deviation was measured with the same preoperative corrective spectacles, and the effect of recession was calculated for them at the end of followup period. The effect of recession is the difference between postoperative and preoperative angle divided by total amount of recession. The collected data were coded and analyzed using SPSS (SPSS Inc, IBM company, Chicago, USA), and the level of significance was set at P value less than 0.05. The power of study was at 80–95% confidence interval. Mean, median, SD, and range were used for quantitative data summarization, and Student’s ttest and Mann–Whitney Utest were performed for their analysis. For qualitative data summarization, number and percentage were used, and χ2test was performed for analysis. Pearson correlation coefficient (r) was used to study association between mean dose response (MDR) and AxL, and logestic linear regression was used to predict the value of MDR from angle deviation and AxL. Results A total of 94 patients (65 females and 29 males) were recruited in this study, and their mean age was 7.63±3.2 years. The patients were divided into two groups: exotropia group (n=52) and esotropia group (n=42). Demographics of patients are summarized in [Table 2]. No significant statistical difference was found between both groups regarding preoperative data, except for age.{Table 2} The mean AxL of all patients was 23.39±1.73, and according to this mean, we subdivided both groups into subgroup I (AxL<23.39) and subgroup II (AxL≥23.39). In exotropia group, subgroup I had 34 patients whereas in subgroup II 18 patients were present; in esotropia group, subgroup I constituted 26 patients whereas subgroup II included 16 patients. The angle of deviation and AxL in exotropia and esotropia groups at 6 months postoperatively are shown in [Table 3].{Table 3} The effect of recession in exotropia at 6 months was 2.27±0.29; in subgroup I, it was 2.42±0.17, whereas in subgroup II, it was 1.98±0.25, with significant difference between subgroups I and II (P<0.05). The effect of recession in esotropia at 6 months was 3.36±0.53; in subgroup I, it was 3.67±0.31, whereas in subgroup II, it was 2.87±0.44, with no significant difference between subgroups I and II (P<0.05). The effect of recession of both groups is shown in [Table 4].{Table 4} [Table 5] and [Table 6] and [Figure 1], [Figure 2], [Figure 3], [Figure 4] show the correlation and regression analysis between MDR and both AxL and preoperative angle in both groups.{Table 5}{Table 6}{Figure 1}{Figure 2}{Figure 3}{Figure 4} Discussion Most surgical formulas for the management of strabismus use the number of millimeters of muscles recession solely on the preoperative angle of deviation [9],[10]. Although some researchers tested a surgical formula that took AxL into account [11],[12],[13]. Yet there is still controversy about its effect on results of recessions in both esotropia and exotropia. We excluded patients with high AC/A ratio and nonaccommodative convergence excess, as previous studies have shown that the response of surgery is influenced by the amount by which the near esotropia exceeded the distance exotropia [14]. Anchor hangback recession surgical technique was performed in all cases, as it is safe and provides the most accurate results with the least amount of complications according to our experience. In this study, the mean AxL was 23.39±1.73, which is comparable with previous study of Rah et al. [7], in which the AxL was 23.21±1.38. There was a negative correlation between both AxL and effect of recession in both groups (esotropic and exotropic), which did not agree with the results of Kushner et al. [6] who reported a negative correlation in esotropic but not in exotropic group. This difference in results may be attributed to that in our study there was no significant difference between esotropic and exotropic groups regarding AxL (23.32±1.69 vs. 23.4±1.78), whereas in the study by Kushner and colleagues, there is a statistical difference, as the esotropic group has relatively lesser mean AxL, which made their results unfair. However, the results obtained in this work agreed with those of Rah et al. [7] who reported negative correlation in both groups. This agreement is mainly because in both studies the AxL of both groups was nearly comparable. Correlation analysis in both groups showed negative correlation between AxL and effect of recession (MDR) and positive correlation between preoperative angle and MDR. For each group, a formula was concluded to predict the effect of recession and therefore recommend amount of recession needed for each AxL. In exotropia: MDR=4.28−(0.11×AxL)+(0.019×preoperative angle). So if the preoperative angle was 30 prism diopter (PD) and the AxL was 23 mm, MDR will be 2.32 PD/mm, which means that we need to recess each lateral rectus 6.5 mm, whereas if the same preoperative angle exists in patient with AxL 26 mm, MDR will be 1.99, which means that we have to recess each lateral rectus by 7.5 mm. In esotropia: MDR=4.93−(0.091×AxL)+(0.016×preoperative angle). So if the preoperative angle was 30 PD and the AxL was 23 mm, MDR will be 3.32 PD/mm, which means that we need to recess each medial rectus 4.5 mm, whereas if the same preoperative angle exists in patient with AxL 26 mm, MDR will be 3 PD/mm, which means that we have to recess each medial rectus by 5 mm. Glantuomo et al. [8] reported positive correlation between AxL and effect of recession in patients with exotropia, which completely disagreed with our results. This may be attributed to the small sample size they investigated (only 28 patients) and the short followup period of 3 months. Intraoperative biometry could prevent errors of AxL measurements caused by restlessness, so it leads to more accurate surgery [15]. This study had some limitations: small sample size, the relatively short followup period, and we did not measure either the limbus insertion distance or the tendon width of the muscles, which were reported to affect the results in previous studies [16],[17]. More future studies with larger sample size and longer followup periods taking other factors in account need to be done. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. References


