The impact of intravitreal tamponing agents used in vitrectomy on the duration of cataract formation and phaco parameters

INTRODUCTION

Vitreoretinal surgery, commonly referred to as pars plana vitrectomy, is a microsurgical technique that involves the removal of the vitreous gel from the eye.^[1] Intraocular tamponades are vital in vitreoretinal surgery, as they help to maintain the volume of the vitreous cavity, displace fluid from retinal breaks and close these gaps, allowing the retina to reattach to the underlying retinal pigment epithelium.^[2]

Silicone oil serves as a long-term tamponading agent in the management of mainly retinal detachments. The primary indications include large retinal tears, proliferative vitreoretinopathy, extensive posterior pole tears and tears in the superior quadrant. Silicone oil is typically preferred in cases where patients need to take a flight postoperatively, cannot hold a specific head position (such as children or patients with mental disabilities), or have a functional single eye that requires early visual rehabilitation. The primary drawback of silicone oil is that its removal necessitates a second surgical procedure.^[3,4]

The three most commonly used gases in vitreoretinal surgery are air, sulphur hexafluoride (SF6) and perfluoropropane (C3F8). The selection of the gas to be used is based on the surgeon’s experience and expertise, as well as the required duration of effective tamponade and patient compliance. For detachments caused by tears limited to a single quadrant and located in the upper half, short-acting gases such as SF6 can be used. If tamponade is aimed at a larger area, such as tears that extend beyond a single quadrant, have a wide distribution, or are located in the lower half, gases with a longer duration of effect, such as C3F8, can be used at higher concentrations. The gas tamponades are also a good option for posterior pole surgeries such as macular holes and epiretinal membranes. But also, gases have several drawbacks as intraocular tamponades. First, they do not allow effective visual rehabilitation while they are present. Moreover, the patients need to remain in a head position for a while, as in posterior pole surgeries. Second, they can cause damage to the lens.^[5,6] Third, they prevent air travel, especially large air bubbles. Finally, they are not permanent.^[7]

The development or progression of preexisting cataracts is the most common and often inevitable complication following vitreoretinal surgery. While the exact cause of cataract formation remains unclear, post-vitrectomy cataracts have been associated with several factors, including advanced age, diabetes, the duration of surgery, prolonged exposure to intravitreal light sources, the type of infusion fluid, cannula size and the use of intraocular tamponades. Most notably, direct trauma to the peripheral or posterior lens capsule by surgical instruments plays a major role in the development of post-vitrectomy cataracts. Accidental contact with the lens surface can rupture the posterior capsule, allowing cortical hydration and resulting in rapid progression to a nearly white cataract opacity.^[8,9]

The cumulative dissipated energy (CDE) is an integrated measurement feature of the Alcon Infiniti® Vision System (Alcon Labs, Hünenberg, Switzerland), a phacoemulsification device specifically designed to allow surgeons to monitor the energy delivered during phacoemulsification. An increased CDE value is associated with enhanced damage to intraocular structures, particularly affecting the corneal endothelium.^[10] Using lower CDE during cataract surgery indicates reduced energy consumption and is regarded as more favourable for corneal healing. The level of CDE used is influenced by several factors, such as lens density, the chosen fragmentation technique and the surgeon’s skill.^[11]

We suggested that the timing of cataract formation after vitrectomy surgery may be influenced by the type of intraocular tamponade used, and the intraocular tamponades can affect the CDE.

MATERIALS AND METHODS

This retrospective comparative study was conducted in a single tertiary referral centre. All procedures adhered to the tenets of the Declaration of Helsinki for research involving human subjects. The study protocol was reviewed and approved by the local medical research ethics committee (AESH-BADEK-2024-145). Written informed consent was obtained from each patient before any invasive procedures. All patients were examined at the University of Health Sciences, Etlik City Hospital. Cataract surgeries were performed using the same phacoemulsification device (Alcon Centurion with Active Sentry) under similar operative conditions. A standard balanced salt solution was used as the irrigating fluid in all cases. Patients were excluded if they had undergone any ophthalmic surgery other than vitrectomy, such as keratoplasty, perforation repair, or glaucoma surgery. Some patients were excluded due to accidental contact with the lens surface by surgical instruments. No patient had a cataract before vitreoretinal surgery. Monthly follow-up examinations were conducted by the same surgeon, and patients who developed grade 3–4 cataract during follow-up were included based on evaluations performed with maximal illumination and magnification on the same slit lamp according to the lens opacity classification system III. A total of 137 patients were included in this study. Cataract development time (CDT) was compared between the eyes that had undergone vitrectomy with different intraocular tamponades. All 137 patients who developed cataracts were informed about the option of cataract surgery. Some preferred to undergo surgery at hospitals in their hometowns, while others declined surgery due to serious systemic health conditions. In addition, some patients were satisfied with their visual function despite having varying degrees of lens opacification. A total of 78 patients underwent cataract surgery performed by the same surgeon using the same phacoemulsification device. The CDE used during surgery was compared among the groups that had received different tamponade agents during prior vitrectomy.

The study data were analysed using the Statistical Package for the Social Sciences 23.0 software (IBM Corp., NY, USA). Descriptive statistics were presented as mean ± standard deviations (SD) (minimum–maximum values). CDT data were evaluated statistically using the Welch test and post hoc comparisons between groups. CDE data were evaluated using the Kruskal–Wallis test due to the number of patients in each group being fewer than thirty.

RESULTS

During vitrectomy, silicone oil tamponade was applied in 50 cases, C3F8 in 48 cases and SF6 in 39 cases. The normality of patients’ ages was assessed by examining the skewness and kurtosis values across the three groups. The homogeneity of variances was tested, and the data were found to be homogeneous. Therefore, a one-way ANOVA test was performed to compare the three patient groups, and no statistically significant difference was found among them (P = 0.081) [Table 1 and Graph 1].

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Graph 1:

The distribution graph of the patients’ ages.

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In patients who received silicone oil tamponade, cataracts developed on average after 7.8 months (SD: 4.08), the minimum CDT was 1 month, and the maximum is 18 months. In some monocular patients, silicone oil was not removed due to the high surgical risk and removal was performed only after emulsification. Forty-eight patients received C3F8 as a tamponade agent during vitrectomy. On average, cataracts developed in these patients after 8.5 months (SD: 6.7), the minimum CDT was 1 month, and the maximum was 24 months. In vitrectomy surgery, 39 patients received SF6 as a tamponade material. On average, cataracts developed in these patients after 4.6 months (SD: 3.1), the minimum CDT was 1 month, and the maximum was 12 months [Table 2 and Graph 2].

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Graph 2:

The distribution graph of the patients’ cataract development time (CDT) values.

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The duration of cataract development followed a normal distribution, as assessed by the skewness and kurtosis values of the three groups.

We assessed the homogeneity of variances and found that the data were not homogeneous. Therefore, the Welch test was performed to compare the three patient groups, revealing a statistically significant difference between them (P < 0.001) [Table 3].

We performed Tamhane’s T2 test as a post hoc analysis to investigate the source of the difference found in the Welch test. In the binary comparison of the three groups using Tamphane’s T2 test, a significant difference was found between C3F8 and SF6 (P = 0.002). This indicates that cataracts developed over a longer duration in the eyes treated with C3F8 compared to those treated with SF6 [Table 3].

When we compared SF6 and silicone oil using the post hoc test, a significant difference was found between the silicone oil tamponade and SF6 gas (P < 0.001). This indicates that cataracts developed over a longer duration in the eyes treated with silicone oil compared to those treated with SF6 [Table 3].

In the comparison of C3F8 and silicone using Tamphane’s T2 test, no significant difference was found between the groups (P > 0.016) [Table 3].

A total of 78 eyes underwent cataract surgery: 23 eyes received silicone oil tamponade, 25 eyes were in the C3F8 group, and 30 eyes were in the SF6 group. In the silicone oil group, the median CDE was 11 (min: 4.40, max: 55.43). In the C3F8 group, the median CDE was 12.96 (min: 1.54, max: 61.6). In the SF6 group, the median CDE was 9.4 (min: 1.8, max: 72.6) [Table 2 and Graph 3].

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Graph 3:

The distribution graph of the patients’ cumulative dissipated energy (CDE) values.

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The statistical distribution of the CDE followed a normal distribution, as assessed by the skewness and kurtosis values of the three groups. We analysed the CDE values using the Kruskal–Wallis test. No significant difference was found in the CDE values between the different tamponades (P = 0.824) [Table 4].

DISCUSSION

Nuclear cataract and posterior subcapsular cataract are the most common types of cataracts associated with vitrectomy. Thompson et al. found that nuclear sclerosis increased in grade over an average follow-up period of 12.4 months in 56 eyes with macular holes treated with vitrectomy, gas tamponade, and transforming growth factor beta-2.^[12] In this study, the progression of nuclear sclerosis was not related to transforming growth factor beta-2, as no significant difference was observed in the progression across the three doses of transforming growth factor beta-2 used. In addition, in this study, posterior subcapsular cataract increased by 0.25 grades over 19.8 months. Cherfan et al. examined the development of nuclear sclerosis in 100 eyes receiving vitrectomy without tamponade for idiopathic epiretinal membranes.^[13] Of these, 80 vitrectomised eyes and 24 fellow eyes developed visually significant nuclear sclerosis or underwent cataract surgery, with the risk increasing in those older than 50 years.^[13]

In our study, no preoperative cataract was present. In the postoperative period, most of the patients who received gas tamponade developed posterior subcapsular cataract, whereas a few developed corticonuclear cataract. No cases, including those with silicone oil, demonstrated posterior capsular plaque formation. Only posterior capsular polishing was performed in the cases where it was deemed necessary. CDT and phaco power showed a normal distribution. Although no statistically significant difference was found between C3F8 gas and silicone oil, cataracts were observed to develop significantly earlier in eyes treated with SF6 compared to those treated with C3F8 and silicone oil. The fact that SF6 gas causes cataracts earlier than C3F8 gas despite staying in the eye for a shorter duration suggests that other factors, aside from the tamponade material, may influence cataract development. Similarly, the prolonged presence of silicone oil, a long-term tamponade material unless surgically removed, suggests that factors other than the tamponade duration might also affect cataract development.

The development of postvitrectomy cataract appears to be multifactorial and may be more related to the complexity of the ocular condition than to the intraocular tamponades. Among patients under 50-year-old, only 7% developed significant lens opacity in the surgical eye compared to the non-surgical eye over the course of 2 years. In patients over 50-year-old, 79% experienced significant lens opacity in the surgical eye compared to their non-surgical eye during the same period.^[14] This suggests that age is an important factor in cataract formation after pars plana vitrectomy. One of the strengths of our study is that there was no significant age difference between the groups, thereby eliminating any potential age-related bias.

In addition, in patients with diabetic retinopathy, trauma, proliferative vitreoretinopathy, or endophthalmitis, the development of post-vitrectomy cataracts may be influenced by the underlying disease and the presence of inflammation. Patients with epiretinal membranes, macular holes, or haemorrhage due to choroidal neovascular membranes may have a reduced risk of developing post-vitrectomy cataracts, regardless of the type of intraocular tamponade used, as these conditions typically involve shorter surgery times and tend to be less inflammatory.^[15] However, patients with proliferative vitreoretinopathy or trauma have a higher risk of developing post-vitrectomy cataracts due to longer surgery times and a tendency for excessive inflammation.

Cataract surgery in a vitrectomised eye carries risks of potential complications, such as posterior capsule rupture and nucleus drop, due to the absence of vitreous support, which causes instability of both the zonules and posterior capsule.^[16] The development of new techniques in cataract surgery aims to decrease complications and reduce the risk of tissue damage and endothelial cell loss, particularly during prolonged surgical interventions.^[10] A lower CDE in phacoemulsification during cataract surgery indicates less energy usage, which is considered more favourable for corneal recovery. In a study where cataract surgery was performed in combination with vitrectomy, it was observed that the CDE values were significantly higher in the combined group. The mean CDE was 11.60 ± 7.8 (range: 0.01–44.72) in eyes that underwent only phacoemulsification, while it was 15.07 ± 8.04 (range: 0.01–29.72) in the combined phacovitrectomy group.^[17] The use of various tamponading agents in vitreoretinal surgery and the development of new techniques in cataract surgery have made it customary to investigate the impact of these tamponading agents on CDE. In our study, the CDE values demonstrated a wide range but followed a normal distribution. There was no statistically significant difference in CDE values between the resorbable gas tamponades and silicone oil, which provides a permanent tamponade effect. These findings suggest that the type of tamponade used during vitrectomy has a similar impact on CDE values.

CONCLUSION

Studies have shown that cataract development is one of the complications associated with vitreoretinal surgery. Our study investigates the effects of tamponade materials on cataract formation. The observation that SF6 tamponade remains in the eye for a shorter duration yet leads to faster cataract formation suggests the presence of additional risk factors. These factors may contribute to cataract development independent of the tamponade material’s retention time in the eye. Furthermore, the second part of our study, which reveals no significant difference in CDE values between the groups, indicates that, despite cataract surgery being more challenging after vitreoretinal surgery, CDE is independent of the tamponade materials used.

We acknowledge several limitations of this study. It is well known that accompanying systemic diseases can also influence cataract development. Gas tamponades are more commonly used in cases of epiretinal membrane (ERM), macular holes and vitreous haemorrhages, whereas silicone oil is typically preferred in cases of large retinal tears and endophthalmitis. However, in our study, we did not categorise patients based on the indications for vitrectomy. As a result, we were unable to evaluate cataract development separately according to the underlying indications.

A notable strength of this study lies in the fact that all surgical procedures were performed by the same experienced surgeon using the same phacoemulsification device, thereby ensuring consistency in surgical technique and minimising operator-related variability. Furthermore, we were unable to find any study comparing the CDE in eyes with different tamponades, which makes this study unique. In conclusion, the development of cataracts and the phacoemulsification parameters in eyes that previously underwent vitreoretinal surgery appear to be more closely associated with the complexity of the case, rather than the sole use of intraocular tamponades. This finding can aid vitreoretinal surgeons in both surgical planning and counselling patients undergoing phakic vitreoretinal surgery.