A retrospective review of medical records was performed to identify all patients diagnosed with dissociated vertical deviation and treated with combined recession-resection of the superior rectus muscle. A total of 21 patients were identified in the period between 2016 and 2020 in Delta Eye Hospital in Egypt, our exclusion criteria were previous surgeries on the superior rectus muscle, simultaneous surgery on other muscles, oblique muscle dysfunction and incomplete follow-up. Sufficient follow-up was defined as attending a follow-up visit at least 6 months following the procedure. The study was carried out in accordance with the tenets of the Declaration of Helsinki of 1964, as revised in 2013 and an informed consent was obtained from all patients or their guardians before the procedure.
Preoperative data that were collected from patients records included cycloplegic refraction, best corrected visual acuity measurement (BCVA), ocular motility examination and history of previous strabismus surgeries if present. The angle of deviation was measured using a prism cover test with base-down prism held in front of the non-fixing (covered) eye with patient looking at distance and wearing his best optical correction ; the degree of DVD is determined by the prism power at which the downward refixation movement is neutralized. DVD was considered asymmetrical when there was more than 10 PD difference in DVD measurement between both eyes. The preoperative angle of stereopsis was measured using Titmus fly test.
All surgeries were performed under general anaesthesia using the standard limbal incision approach, 2.5 mm from the insertion end of the superior rectus muscle were resected first by the conventional resection technique then the muscle is recessed by an amount exceeding the resection using fixed scleral sutures. The amount of recession was calculated based on the maximum deviation angle as shown in the established nomogram previously used by Tibrewal et al (16) and presented in table 1. Bilateral surgery was performed in all patients using either symmetrical or asymmetrical amounts of recession according to the pre-existing deviation angle.
Table (1): Amount of SR recession performed for different grades of DVD (16)
DVD in PD
|
Amount of SR recession in mm
|
<10
|
6.0
|
11–15
|
8.0
|
16–20
|
9.0
|
>20
|
10.0
|
Final deviation was assessed at six months post-operatively and success was defined as absence of manifest DVD. However, any residual latent deviation was measured and the postoperative motor outcome was graded according to the residual deviation angle as measured by prism cover test as excellent (0-4 PD), good (5-9 PD), fair (10-14 PD) and poor (>14 PD) (16, 17, 18)
The postoperative stereopsis was assessed by Titmus test at 6 months following the operation; significant change in stereopsis was defined as change of at least 2 octaves from the previous preoperative examination to overcome any test-retest variability (19).
Statistical analysis:
The collected data was entered to and analysed by computer using Statistical Package of Social Services, version 25 (SPSS) (IBM, 2017).
Mean, median, standard deviation, and range were used for quantitative data summarization. For qualitative data summarization and analysis; number and percentage were used.
IBM. (2017). IBM SPSS Statistics for Windows, Version 25. Armonk, NY: IBM Corp. http://www-01.ibm.com/support/docview.wss?uid=swg27049428