The cornerstone of surgical intervention in stage 4 ROP is a combination of anatomic retinal reattachment and recession of vascular activity for optimal functional outcome [7, 10].
SB surgery was the treatment of choice for stage 4 ROP in the past [11, 12]. With the advent of new, more sophisticated technologies in vitreoretinal instrumentation, small-gauge LSV has largely replaced SB in stage 4 ROP, as there is evidence that it releases vitreoretinal traction more effectively [13]. Anatomic success after SB has been reported between 46% and 75%, [11, 12, 14, 15, 17] whereas after LSV between 80–90% depending on the stage of ROP, 4A or 4B [4, 13, 16–18]. The advantages of vitrectomy include releasing of vitreoretinal tractions, removal of endogenous vasodilators and angiogenic factors from the vitreous scaffold and prevention of fibrovascular membrane formation [5]. On the other hand, access to specialized equipment for pediatric vitrectomy is not universal and SB surgery may still have a role in the management of ROP-related retinal detachments with peripheral traction.
This study investigated the effectiveness of SB in stage 4A and 4B ROP in infants who did not undergo vitrectomy, due to lack of pediatric vitrectomy instrumentation. In all seven eyes, SB led to regression of vascular activity, which was evident by disappearance of the neovascular tufts in the detached ridge and recession of plus disease. Gradually the retina reattached and the funduscopic appearance remained stable for several months after SB removal. The anatomic outcome was favorable in all cases. At last follow-up there was complete retinal reattachment in five eyes and residual small peripheral retinal detachments without evidence of traction in two eyes. One eye had macular and disc dragging and one eye had a macular traction fold. Regarding the functional outcome, five of seven eyes achieved a fix and follow vision, one eye had central steady and maintained fixation and one eye had central steady and unmaintained fixation. The anatomic result was maintained for an average postoperative follow-up time of 26.4 months.
The favorable outcomes of this study are probably related to the location and type of retinal detachments in this cohort of premature infants. In all five eyes with stage 4A ROP, retinal traction was evident in the peripheral retina. Several studies have suggested that the effect of SB in stage 4 ROP is to mechanically minimize traction by scleral indentation and to reduce neovascular activity of peripheral proliferation [6, 20]. Due to previous laser treatment and the presence of tractional retinal forces in six of seven eyes, no further intravitreal anti-VEGF injections were performed, in order to avoid further fibrosis and worsening of traction [21]. Apart from the mechanical effect of SB on reducing the tractional retinal forces, fluorescence angiography has shown that SB additionally stabilizes the neovascular activity of fibrovascular tissue [20]. It has been suggested that SB leads to VEGF downregulation by relieving mechanical stress and by improving the oxygen supply from the choroid to the retina [20].
Retinal reattachment was also achieved in infant #4, who presented with stage 4B ROP after ranibizumab injection and had no evidence of traction. Although no peripheral break was found in funduscopy, it cannot be excluded that the inferior retinal detachment in this case was rhegmatogenous. Peripheral retinal breaks in ROP may occur from traction on the thin retina, in atrophic areas such as laser spots, or as a consequence of intravitreal injections [7]. SB is indeed indicated in rhegmatogenous retinal detachments from peripheral breaks, as it supports peripheral traction with indentation of the globe and promotes consequent retinal reattachment without removing the lens [22]. SB was also effective in infant #3, who was initially treated with systemic steroids for management of post-laser exudative retinal detachment [23, 24].
Apart from the indications of SB surgery in ROP, the main reason for employing this technique in the present study, is that SB surgery requires minimal equipment and is associated with more affordable costs [25]. The economic crisis has posed a considerable burden on the Greek public healthcare system, and even tertiary referral centers face severe shortages of medical equipment. On the other hand, vitrectomy requires more specialized and costly equipment. A comparison of the costs of scleral buckling and pars-plana vitrectomy (PPV) for adult retinal detachments found that, considering all costs, including eventual cataract surgery, scleral buckling procedures were 10.7% less expensive than PPV for retinal detachment repair in phakic patients [25]. Of note, our tertiary referral center is the only public center in Greece that offers pediatric vitreoretinal surgery.
On the other hand, SB surgery has several disadvantages. There are intraoperative complications, such as risk of scleral perforation due to the reduced thickness of the infant sclera [11, 12]. Removal or division of the buckle with a second surgery is required after 3–6 months, in order to reduce myopia and promote eye growth [11, 12]. Axial elongation and forward shift of the lens lead to axial and lenticular high myopia, which predisposes to amblyopia [26]. The average postoperative refractive error in adults undergoing encircling SB is -2.75 D [26]. However, postoperative myopia in infants with ROP is much greater (mean, − 22 D), which often improves by about 5 D following sectioning of the buckle [8, 27]. It has been reported that the refractive error after SB removal in infants with ROP ranges from + 1.25 D to -20 D [8, 26, 27]. Consistent with previous studies, the average final myopic error after buckle removal in the present series was − 7.5 D, ranging from − 3 D to -14 D [8, 28]. High myopia may cause ametropic and anisometropic amblyopia in unilateral cases, as in infants #2 and #4.
Regarding the functional outcome, five of seven eyes achieved a fix and follow vision, one eye had central steady and maintained fixation and one eye had central steady and unmaintained fixation. Although these findings are in general favorable, longer follow-up is needed to provide more accurate estimates of visual acuity. Most authors agree that scleral buckling can successfully reattach the retina in stages 4A and 4B, but the functional results are variable and often disappointing. Hinz et al. reported a 75% success rate after SB surgery in 4A ROP eyes, with two eyes having a light perception (LP) acuity and five eyes achieving vision better than LP [28]. Visual acuity at 4.5-years by Gilbert et al. for eyes that were stage 4A at 3 months were extremely poor, with only 6 (18%) of 34 having better than 20/200 visual acuity and 22 (65%) being termed “blind” (light perception, no light perception, hand motions) [1].
One of the causes for reduced visual function in this series was optic atrophy. Two of seven eyes (infants #1 and #3) developed temporal optic disc pallor. Optic atrophy in premature infants with ROP-related retinal detachments may result from prematurity, or as a sequelae of laser ablation, ocular surgery, or postoperative inflammation in the developing retina. In a study of 272 children with optic atrophy, complications from premature birth were the most frequent etiology of optic atrophy (n = 44, 16%), with 68% of premature infants having a history of intraventricular hemorrhage [29].
Additionally, poor ocular perfusion pressure (due to reduced mean blood pressure under anesthesia and elevated intraocular pressure during ocular surgery) may also lead to optic atrophy [30]. Furthermore, it is unclear if the detached retina and incomplete vascularization may lead to retinal degeneration due to poor diffusion of nutrients, especially when the macula is detached [30]. Further macular pathology of the premature retina, such as cystoid macular edema in infant #3 (Fig. 2), which may go undetected in routine fundoscopy, can also contribute to reduced vision.
This study should be viewed in the light of some limitations, such as non-randomization. ROP is a multifactorial disease and the heterogeneity in patient population makes the comparison of studies extremely difficult, and partly explains the differences in success rates and visual outcomes. Due to its unique nature and the complexity of therapeutic approaches there is no prospective study that directly compares SB and LSV. This study did not aim to compare anatomic outcomes between two different surgical methods, but to highlight the outcome in cases where SB was the only available treatment. Further study is needed to determine the effect of this surgical approach on long-term visual development.
In summary, the choice of surgical method depends on severity of ROP, presence of plus disease or neovascularization (the vascular activity of the disease), retrolental involvement, nature of vitreoretinal traction and type of retinal detachment (exudative or rhegmatogenous component). This study focuses on the management of retinal detachments with peripheral traction in premature infants with comorbidities, where SB was the only available surgical modality. In this mini case series, anatomic reattachment was achieved in all eyes after SB and the result was maintained for the next 2 years. We conclude that SB continues to deserve a place in the armamentarium for ROP-related retinal detachment repair. SB is effective in appropriately selected cases, it involves no intraocular surgery, results in no cataract formation, and is economically cost-effective. Characteristics and comorbidities of premature infants as well as the available resources are potential factors associated with treatment of choice and general outcomes.