Refractive and ocular biometric changes after silicone oil tamponade (SOT) in phakic eyes have been studied thoroughly; however, similar studies amongst Sudanese patients with vitreoretinal conditions were not carried out.
This study aimed to assess post-operative changes in refraction, corneal power and axial length after pars plana vitrectomy (PPV) with SOT in phakic patients.
The study was conducted at Sudan Eye Center, Khartoum, Sudan.
A cross-sectional retrospective hospital-based study was performed at Sudan Eye Center. The study included all phakic patients who underwent PPV with SOT for a variety of vitreoretinal conditions from October 2018 to January 2019. Clinical investigations included uncorrected visual acuity (VA), best-corrected VA, refraction, corneal power and axial length pre- and post-surgery. Differences in these parameters were assessed using a paired sample
Medical records of 59 consecutive patients (59 eyes, 41 men and 18 women) with ages ranging from 22 years to 75 years were studied. The findings revealed a statistically significant hypermetropic change (pre: –0.17 ± 2.44 dioptre [D] and post: +4.43 ± 2.04 D) with a
A hypermetropic shift in refraction, longer axial length and non-considerable increase in corneal power were observed amongst Sudanese phakic patients after PPV with instillation of silicone oil.
The silicone oil (SO) is an effective intraocular tamponade material used in complex vitreoretinal surgeries with a higher refractive index (1.405) in comparison with the vitreous and aqueous humour.
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In aphakic eyes, the SO produces a convex surface, thus creating a myopic refractive change the amount of myopic shift depends on the papillary aperture diameter. Based on the schematic eye calculation, a refractive shift from +12.5 D to +5.6 D has been observed in aphakic eyes filled with SO.
A retrospective cross-sectional hospital-based study was conducted in Sudan Eye Center, Khartoum, Sudan. The study included all patients who underwent PPV with SOT for a variety of vitreoretinal conditions from October 2018 to January 2019.
Subjects included in this study had undergone PPV without scleral buckling, SOT agent. Fifty-nine consecutive patients (59 eyes, 41 men, and 18 women) with ages ranging from 22 years to 75 years were recruited.
Inner and outer eye examinations were performed by ophthalmologist and optometrist with significant expertise. Data collected included demographic characteristics of patients (age, gender, laterality [operated eye right or left]) and eye examinations, which include uncorrected visual acuity (VA), objective and subjective refraction, best-corrected VA, keratometry readings and axial length of the eye. The above-mentioned examinations were performed pre- and post-surgery. The surgical procedures included the standard three-port pars plana techniques, which were carried out by one retinal consultant, , and SO injection was used in surgery. Screen Save Apramed VA test chart (E) was used to measure uncorrected VA and best-corrected VA, which was recorded in Snellen’s decimal notation. Refraction and keratometry were performed using SHIN-NIPPON (Accuref k-900) auto kerato-refractometer; however, the axial length of the eye was measured using TOMEY Ultrasonic A/B Scanner (UD-8000).
Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) Windows version 21.0 (SPSS Inc., Chicago, IL, United States). Data were reported as means ± standard deviations (s.d.). A paired sample
Ethical approval was obtained from Al-Neelain University, Khartoum, Sudan, and the study was performed according to the Declaration of Helsinki on the conduct of human research. Informed consent was waived because of the retrospective nature of the study. However, efforts were made to ensure that patients’ confidentiality was guaranteed.
The study included 59 participants (59 phakic eyes) who underwent PPV combined with SOT for different vitreoretinal conditions in one eye. Amongst them 41 (69.5%) were men and 18 (30.5%) were women with a mean age of 52.19 ± 11.74 years (range: 22–75 years). In terms of refractive error, 40.7% of the patients were hypermetropic, 33.9% myopic and 25.4% with faint reflex at baseline (before surgery). The mean uncorrected VA was 0.13 ± 0.17, whilst the mean best-corrected VA was 0.17 ± 0.20. At baseline, means of refraction, average keratometry reading and axial length of the eye were –0.17 ± 2.44 D, 43.60 ± 1.96 D and 23.61 ± 1.17 mm, respectively, as shown in
Demographic and clinical characteristics of patients.
Characteristic (59 patients, 59 eyes) | Frequency | % | Mean ± s.d. | Range | Mean | Dioptre |
---|---|---|---|---|---|---|
Age |
- |
- |
52.19 ± 11.74 |
- |
- |
- |
- | - | - | - | - | - | |
Male | 41 | 69.5 | - | - | - | - |
Female | 18 | 30.5 | - | - | - | - |
- | - | - | - | |||
Hyperopia | 24 | 40.7 | - | - | - | - |
Myopia | 20 | 33.9 | - | - | - | - |
Not detected | 15 | 25.4 | - | - | - | - |
Mean refraction | - | - | - | - | −0.17 ± 2.44 | - |
Range (D) | - | - | - | - | - | −6.00 to 4.75 |
Mean corneal power | - | - | - | - | 43.60 ± 1.96 | - |
Range (D) | - | - | - | - | - | 39.63 to 48.50 |
Mean axial length of the eye | - | - | - | - | 23.61 ± 1.17 | - |
Range (mm) | - | - | - | - | - | 22.02 to 27.37 |
Mean uncorrected VA | - | - | - | - | 0.13 ± 0.17 | - |
Range | - | - | - | - | - | 0.002 to 0.60 |
Mean best-corrected VA | - | - | - | - | 0.17 ± 0.20 | - |
Range | - | - | - | - | - | 0.002 to 0.80 |
D, dioptre; K, keratometry; VA, visual acuity; s.d., standard deviation.
Before starting this part of the analysis, assumptions for each statistical test were checked and found not violated. The findings revealed a statistically significant hypermetropic change (pre: –0.17 ± 2.44 D and post: +4.43 ± 2.04 D) with a
Pre-operative and post-operative comparison of variables.
Variable ( |
Mean ± s.d. |
||
---|---|---|---|
Pre-operative | Post-operative | ||
Refraction | −0.17 ± 2.44 | 4.43 ± 2.04 | < 0.001 |
Corneal power | 43.60 ± 1.96 | 43.63 ± 2.03 | 0.450 |
Axial length | 23.61 ± 1.17 | 23.82 ± 1.27 | < 0.001 |
Uncorrected VA | 0.13 ± 0.17 | 0.08 ± 0.07 | 0.007 |
Best-corrected VA | 0.17 ± 0.20 | 0.24 ± 0.22 | 0.010 |
VA, visual acuity; s.d., standard deviation.
Further analysis showed negative correlations between refraction and axial length of the eye pre- and post-surgery with
Correlation between the refractive status and axial length of the eye (a) pre-surgery and (b) post-surgery.
Refraction before and after surgery.
Currently, SO plays an important role in vitreoretinal surgery and is considered to be the material of choice as a long-term and stable retinal tamponade. The use of SO for vitreoretinal surgeries has many arguments with respect to its safety. Hence, the removal of SO is normally recommended.
An overall hypermetropic shift of 4.60 D in refraction was observed in this study, which was statistically significant,
The corneal power for the studied group was found to be increased slightly after the operation, However, this increment did not have a clear effect in refraction after the operation (
The current study showed a significant change in overall axial length; a longer axial length mean was reported post-operative (
Limitations of this study include the small sample size and its retrospective nature. Despite these limitations, the study was able to provide valuable information on the biometric and refractive changes after SOT in PPV. A prospective randomised future study with measurement of axial length, keratometry, ACD, and refractive state pre- and post-operatively in larger numbers of phakic eyes will be needed.
A hypermetropic shift in refraction, longer axial length and non-considerable increase in corneal curvature were observed amongst Sudanese phakic patients after PPV with instillation of SO. The hypermetropic shift in phakic eyes was because of the high refractive index of SO compared with vitreous rather than the changes in ocular biometry.
The authors are grateful to the staff of Sudan Eye Center, Khartoum who helped in data collection.
The authors declare that they have no financial or personal relationships that may have inappropriately influenced them in writing this article.
A.E.H., A.E.M.E. and N.M.F.A. designed the model and the computational framework and analysed the data. M.A.A. and S.H.A. carried out the implementation. M.A. performed the calculations. A.E.H. and A.E.M.E. wrote the manuscript with input from all authors. S.H.A. and M.A.A. conceived the study and were in charge of overall direction and planning.
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Data sharing is not applicable to this article.
The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of any affiliated agency of the authors.