|Year : 2020 | Volume
| Issue : 3 | Page : 204-209
Evaluation of anterior segment parameters in pars plana vitrectomy and silicone oil injection
Moataz H Osman, Shaimaa A Arfeen, Ghada A Nassar
Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo, Egypt
|Date of Submission||10-Mar-2020|
|Date of Decision||02-Jun-2020|
|Date of Acceptance||05-Jul-2020|
|Date of Web Publication||23-Sep-2020|
MD Ghada A Nassar
10 Said Street, Heliopolis, Cairo 11757
Source of Support: None, Conflict of Interest: None
Purpose The aim of this study was to compare the changes in anterior segment parameters induced by pars plana vitrectomy (PPV) and silicone oil injection in phakic and pseudophakic eyes.
Patients and methods This is a prospective comparative study that included 40 eyes with rhegmatogenous retinal detachment that underwent vitrectomy and silicone oil injection. They were divided equally into two groups. Group 1 included phakic eyes and group 2 included pseudophakic eyes. Anterior segment parameters were documented by using a CSO Camera (Costruzione Strumenti Oftalmici) before and 1 month after surgery. The changes in the following parameters were compared between the two groups: anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), central corneal thickness (CCT), corneal volume (CV), horizontal anterior chamber diameter, and surgically induced astigmatism.
Results At 1 month postoperatively, in group 1, there was a significant decrease in the mean of ACA and ACV as compared with the preoperative values (P=0.024 and 0.011, respectively). In group 2, there was a significant decrease in the 1-month postoperative mean of ACD, ACA, and ACV as compared with the preoperative values (P=0.021, <0.0001 and 0.015, respectively) and a significant increase in the mean of CCT and CV values (P<0.0001 and 0.002, respectively). In group 2, there was more reduction in ACD, less reduction in ACA, and higher increase in CCT and CV as compared with group 1 (P=0.021, 0.001, <0.0001, and 0.023, respectively).
Conclusion The presence of the crystalline lens acts as a barrier which decreases the changes in the anterior segment parameters and improves the functional outcome following PPV and silicone oil injection as compared with pseudophakia. Therefore, it may be useful to stabilize the anterior segment in patients with PPV and silicone oil injection.
Keywords: anterior segment parameters, crystalline lens, pars plana vitrectomy, pseudophakia, Scheimpflug, silicone oil
|How to cite this article:|
Osman MH, Arfeen SA, Nassar GA. Evaluation of anterior segment parameters in pars plana vitrectomy and silicone oil injection. Delta J Ophthalmol 2020;21:204-9
|How to cite this URL:|
Osman MH, Arfeen SA, Nassar GA. Evaluation of anterior segment parameters in pars plana vitrectomy and silicone oil injection. Delta J Ophthalmol [serial online] 2020 [cited 2020 Oct 25];21:204-9. Available from: http://www.djo.eg.net/text.asp?2020/21/3/204/295877
| Introduction|| |
The improvement of surgical techniques and instruments in pars plana vitrectomy (PPV) have increased the anatomical success in treating vitreoretinal disorders . However, postoperative changes of the anterior segment parameters may result in postoperative complications and refractive changes affecting the functional outcome and the quality of vision ,. Such complications include glaucoma or hypotony resulting from narrowing of the anterior chamber angle (ACA), shallowing of the anterior chamber, and ciliary body detachment ,,,.
To date, there have been many studies about the anterior segment changes following vitrectomy reporting controversial results. However, to our knowledge, there have been no prospective clinical trials to assess the effect of the lens status on the changes of the anterior segment parameters using the combined Scheimpflug–Placido disk imaging system. Therefore, this study was conducted to compare the changes in anterior segment parameters following PPV and silicone oil injection in phakic and pseudophakic eyes.
| Patients and methods|| |
This is a comparative prospective study that was performed at the Ophthalmology Department of Cairo University Hospital. The study was approved by the Institutional Review Board and was conducted in compliance with the principles of Helsinki Declaration. All patients signed a written informed consent to participate in the study and for publication of data before enrollment into the study.
Forty eyes of 40 patients with rhegmatogenous retinal detachment, for whom PPV and silicone oil injection was performed, were included in the study. Patients were divided according to the lens status into two groups: Group 1 consisted of 20 phakic patients and group 2 consisted of 20 pseudophakic patients. Patients were excluded if they have a history of previous vitreoretinal surgery or other ocular surgeries except phacoemulsification. We also excluded cases that required during surgery any of the following: scleral buckle, gas tamponade injection, phacoemulsification, corneal epithelium scrapping, and sutures to close the sclerotomies.
All patients underwent a complete preoperative ophthalmic examination. An experienced optometrist (K.M.) documented the preoperative anterior segment parameters for all cases using combined the Scheimpflug–Placido disk system (Costruzione Strumenti Oftalmici, Sirius; CSO Camera Inc., Florence, Italy). The following parameters were documented: anterior chamber depth (ACD), ACA, anterior chamber volume (ACV), central corneal thickness (CCT), corneal volume (CV), horizontal anterior chamber diameter (HACD) and K-readings (amount in diopters and axis).
Pupillary dilatation was achieved by the use of cyclopentolate hydrochloride 1% eye drops (Cycloplegic eye drops; Alcon, Cusi SA, Barcelona, Spain) and tropicamide 1% eye drops (Mydrapid eye drops; Alexandria Company for Pharmaceutical and Chemical Industries, Alexandria, Egypt) within 30 min before surgery. All surgeries were performed by the same surgeon (M.H.). A standard 23-G three-port PPV was performed through two superior sclerotomies at 2 o’clock and 10 o’clock with an infusion cannula fixed in the inferotemporal quadrant. Core vitrectomy was done followed by posterior hyaloid membrane removal assisted by 40 mg/ml triamcinolone acetonide aqueous suspension (Kencort; SmithKline Beecham, Cairo, Egypt, an affiliated company to GlaxoSmithKline, Brentford, England). Retinal flattening was achieved by perfluorocarbon liquids (Purified Perfluorodecalin, 7 ml vial, BioFluor by Omnia Fluid, Bucin, Italy). Retinal breaks were treated with endo-laser photocoagulation. Air–fluid exchange was performed and 1000 centistoke (cSt) silicone oil 10 ml vial (Biosil by Omnia Fluid, Fonte Nuova, Italy) was injected. Massage was done to self-seal the sclerotomies.
All patients were examined with a CSO Sirius camera 1 month after surgery by the same optometrist to document all the above-mentioned parameters. Surgically induced astigmatism (SIA) was calculated according to keratometry values using the vector analysis software based on the method described by Alpins and Goggin . Preoperative and postoperative anterior segment parameters of each group were compared. The changes in the anterior segment parameters induced by surgery were also compared between the two groups.
Data were described in terms of mean±SD, range or frequencies (number of cases), and percentages as appropriate. The normality of the distribution for each dataset was checked using the Kolmogorov–Smirnov and Shapiro–Wilk tests. Comparison of numerical variables showing nonnormal distribution was done using nonparametric methods: Wilcoxon test for dependent samples and Mann–Whitney test for independent samples. When variables were normally distributed, independent-sample t-test or paired-sample t-test were used when appropriate. A P value of less than 0.05 was considered statistically significant. Calculations were done using SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, Illinois, USA) version 17 for Windows.
| Results|| |
Forty eyes of 40 patients were included in the study and were equally divided into two groups according to the lens status. Group 1 included phakic eyes and group 2 included pseudophakic eyes. There were no statistically significant differences between the two groups regarding demographic and clinical data. The mean age in groups 1 and 2 was 41.2±12 and 66.75±5.43 years, respectively, (P=0.068). Group 1 included five women and 15 men, while group 2 included four women and 16 men (P=0.93). The mean preoperative intraocular pressure (IOP) in group 1 and group 2 was 15.33±3.11 and 13.33±1.30 mmHg, respectively, (P=0.851).
In group 1, there was a statistically significant decrease in the 1-month postoperative means of ACA and ACV as compared with the preoperative values (P=0.024 and 0.011, respectively). The ACA was 51.6±7.8°, preoperatively and decreased to 49±6.79°, postoperatively. The ACV was 140.2±38.1 mm3, preoperatively and decreased to 95.88±37.10 mm3, postoperatively. However, there was no significant change regarding ACD, CCT, CV, and HACD ([Table 1]).
|Table 1 Preoperative and postoperative anterior segment parameters of group 1|
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In group 2, there was a statistically significant decrease in the 1-month postoperative means of ACD, ACA, and ACV as compared with the preoperative values (P=0.021, <0.0001 and 0.015, respectively) and a significant increase in the mean of CCT and CV values (P<0.0001 and 0.002, respectively). There was no significant change regarding the mean of HACD ([Table 2]).
|Table 2 Preoperative and postoperative anterior segment parameters of group 2|
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In group 2, the mean ACD significantly decreased from 4.42±0.53 to 3.97±0.44 mm. There was a significantly greater reduction in ACA in group 1 which decreased from 51.6±7.8°, preoperatively to 49±6.79°, postoperatively as compared with the reduction found in group 2 in which the mean preoperative ACA was 56.75±2.04° and the mean postoperative ACA was 55±2.00°. There was a significantly greater increase in CCT in group 2, in which the mean preoperative and postoperative CCT were 496.75±63.36 and 522.75±68.30 μm, respectively, as compared with the nonsignificant increase in CCT documented in group 1. The postoperative increase in the mean CV in group 2 was significantly higher than the increase found in group 1 (3.9±3.59 and 1.7±1.27 mm3, respectively).
Changes between preoperative and postoperative anterior segment parameters are listed in [Table 3]. There was a statistically significant difference between the two groups regarding ACD, ACA, and CCT (P=0.021, 0.001 and <0.0001, respectively). However, there was no significant difference in the ACV, CV, and HACD between the two groups.
|Table 3 Changes between preoperative and postoperative anterior segment parameters (means±SD of postoperative–preoperative values)|
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The mean SIA was 2.16±2.22 diopters (68.34°) and 0.652±0.37 diopters (84.7°) in phakic and pseudophakic groups, respectively, a statistically insignificant difference (P=0.225, [Table 3]).
| Discussion|| |
Owing to the great advances in anatomical success of PPV, it became important to study the factors affecting the functional outcome, including refractive changes and postoperative complications resulting from anterior segment parameter changes . There is a great controversy among studies in the changes in anterior segment parameters induced by posterior segment surgery. These variations may be due to the difference in lens status, anterior segment imaging timing and techniques (A-scan, UBM and Scheimpflug camera), whether retinal tamponade was used or not, and different tamponade types (silicone or gas) and also due to different vitrectomy indications ,. So, we decided to study the effect of lens status on the changes in anterior segment parameters using the CSO Sirius camera; a non-contact method which does not apply pressure that may affect the anterior segment parameters. All cases had rhegmatogenous retinal detachment (RD) and underwent 23-auge PPV and silicone oil injection by a single surgeon. Postoperative imaging of all cases was done 1 month after surgery to give enough time for temporary changes to disappear and stable parameters to be established after inflammatory mediators have disappeared and wound healing was completed.
There was a significant postoperative decrease in central ACD in the pseudophakic group as compared with the phakic group. The difference in configuration between the intraocular lens (IOL) and the crystalline lens which had a more convex posterior surface and higher anteroposterior diameter may have dampened the effect of changes of posterior segment configuration and pressure exerted by the silicone oil anterior surface on the central ACD. In addition, inability of complete anterior hyaloid removal in phakic eyes, to avoid lens injury, may result in residual retrolental layer of vitreous that acts as a barrier between silicone oil and the crystalline lens. On the other hand, meticulous shaving of the vitreous base in pseudophakic eyes may result in loss of zonular fibers that are already weakened during phacoemulsification, which allows more forward movement of the IOL pushed by the anterior convex surface of the silicone oil.
On the contrary, there was a more decrease in the postoperative ACA in the phakic group as compared with the pseudophakic group. It has been suggested that the crystalline lens makes the angle narrower than the IOL and makes it more liable to closure by supraciliary effusion, iris congestion, pressure exerted by silicone oil on iris lens diaphragm, and peripheral anterior synechiae.
The postoperative reduction in ACV, in both groups, was comparable. This reduction may result from supraciliary effusion, iris congestion, increased lens thickness, and increased corneal thickness.
The results of this study were different from many similar studies that found no significant postoperative changes in ACD, ACV, and ACA after vitrectomy and silicone oil injection ,,. Calik et al.  studied 22 cases that underwent vitrectomy and silicone oil injection using the Pentacam Scheimpflug camera before operation and a week and a month after operation. They did not specify the lens status. They reported no significant difference between the preoperative and the 1-month postoperative mean ACD, ACA, and ACV. They found that the average ACD increased from 2.6 mm before surgery to 3.01 mm in the first postoperative week and then decreased to 2.71 mm at the first month. They found that the mean ACV was 162.3±57.76, 166.27±43.95, and 165.0±35.007, preoperatively, 1 week postoperatively and 1 month postoperatively, respectively. They explained the increase in ACV in silicone-oil-injected eyes at the first week to be related to the cohesive power of the silicone oil on the posterior lens surface. Lens diaphragm is pushed back from the ciliary body by the silicone oil in patients with prone position. This effect decreases by time and ACV returns to the preoperative values. Ünsal et al.  have studied the anterior segment changes induced by PPV and silicone oil injection in pseudophakic eyes. UBM measurements were performed in the supine position before and 1 week after surgery. They reported no significant change in ACD and trabecular meshwork-iris angle (TIA). The mean preoperative and postoperative ACD were 3.37±0.76 and 3.36±0.67 mm, respectively. The mean preoperative and postoperative TIA were 24.77±9.6 and 27.44±7.2°, respectively. Ghomi and Ghassemi  studied seven phakic eyes that underwent PPV, with silicone oil being injected in five eyes, using ultrasound biomicroscopy (UBM) before and 3 months after PPV. They reported an increase in the crystalline lens anteroposterior diameter that was explained by the development of nuclear sclerotic cataract, without significant changes in the ACD, which they explained by posterior subluxation of the lens, occurring in the supine position of patients during the postoperative UBM, resulting from zonular instability after PPV and the disruption of the hyaloid face. This led to an underestimation of the ACD.
There were great variations in the results of similar studies of vitrectomy without silicone oil use. Neudorfer et al.  evaluated 28 eyes (10 of them were pseudophakic and 18 were phakic) which underwent vitrectomy. Gas tamponade was used at the end of surgery in 15 patients (seven phakic and eight pseudophakic). They found a significant decrease in ACD measured by UBM in the eyes, which had undergone gas tamponade but not in those without. They explained that by the high surface tension between the gas bubble and the intravitreal fluids that pushes the lens–pupil diaphragm outward. Byrne et al.  have studied PPV in pseudophakic eyes and noticed no significant change in ACD after vitrectomy with or without gas tamponade even in patients with refractive changes. Marigo et al.  in a UBM study of 20 patients who underwent vitrectomy without tamponade reported no statistically significant differences in the ACD and angle opening distance between preoperative measurement and 3 months after vitrectomy with no internal tamponade.
In this study, there was significant postoperative increase in CCT and CV in the pseudophakic group as compared with the phakic group. This can be explained by the compartmentalizing effect of the crystalline lens, which acts as a barrier protecting the anterior segment from the inflammatory mediators released by vitrectomy that affects the corneal endothelium which is expected to be more compromised by phacoemulsification in group 2. These results differ from those of Calik et al.  who reported a temporary increase in CCT in the first weeks postoperatively that returned to the preoperative values at 1 month. Changes in corneal thickness and volume should be taken into consideration in postoperative IOP measurement.
In this study, the lens status did not affect the amount of SIA. Calik et al.  reported a temporary increase in SIA in the first week that regressed after 1 month in the cases that underwent vitrectomy and silicone oil injection. In their study, the mean value of SIA was 3.69±2.74 D (57°) at 1 week after surgery and it regressed to 1.69±1.82 D (50°) at 1 month after surgery. The SIA at the first week can be related to the sclerotomy sites, cauterization of sclerotomies, or too tight sutures. Astigmatism regressed with wound healing and suture absorption. The amount of 1-month postoperative SIA reported by Calik and colleagues is very close to that reported in the present study.
The current study was limited by the small number of enrolled patients and the short follow-up period. Another limitation is that we did not correlate the anterior segment changes with incidence of complications and changes in refraction, which have a significant effect on visual outcome. Further studies are needed to evaluate the postoperative IOP and to find the correlation between postoperative IOP and CCT. We recommend future studies to measure the serial postoperative parameters of the anterior segment after PPV with close follow-up, for better evaluation of the persistence of the aforementioned parameter changes. Although the Scheimpflug camera is accurate in the assessment of the cornea and ACD and volume, it is not accurate in ACA imaging and showed relatively low correlation with gonioscopy .
| Conclusion|| |
Evaluation of the functional outcome and refractive changes is important in phakic or pseudophakic patients after PPV. Although PPV induced changes in anterior segment parameters that may cause refractive changes and postoperative complications, the presence of the crystalline lens might act as a barrier, which decreases these changes as compared with pseudophakia. Thus, preservation of the crystalline lens should be considered for better functional and refractive outcome.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]