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Dr.Aashi Bansal, B16653, Dr.Pramod Sadashiorao Bhende, Dr.Meenakshi Swaminathan, Dr.Ekta Rishi

Abstract:

TITLE:

Refractive change after buckle removal/division in infants with retinopathy of prematurity (ROP). PURPOSE: To determine change in spherical equivalent (SE) after buckle removal/division in infants who underwent encircling buckle surgery (ESB) for ROP. METHODS:  Eighteen eyes of 13 infants were retrospectively analysed. Gestational age, birth weight, stage of ROP, SE following ESB and buckle removal/division was noted. RESULTS: Mean post menstrual age at presentation was 40.41 weeks (SD=5.76), mean gestational age was 29.9 months (SD=2.37), and mean birth weight was 1.36 kg (SD=0.42).). Mean post menstrual age at ESB was 42.47 weeks (SD=4.54). Median age at removal of buckle was 14.97 months .Median change in SE following removal/division of buckle was 1(p=0.003). Median follow-up was 6.02 years (range=2-9). Conclusion: Following ESB for ROP, buckle removal/division causes significant decrease in myopia without a risk of re-detachment, overall success rate being 94.4%

Keywords: Encircling scleral buckle, myopia, retinopathy of prematurity

Introduction:

Retinopathy of prematurity(ROP) ,a vasoproliferative disorder of low birth weight premature infants accounts for 3% of vision loss in children.(1)As reported in Early treatment of ROP study, despite screening and early intervention ,  12%  eyes develop retinal detachment  before age of 9 months . (2) Encircling scleral buckle(ESB) by eliminating the vitreo-retinal traction and decreasing neovascular activity decreases the progression of ROP .(3)But ESB also contributes to the myopia, postulated mechanism being axial elongation, changes in lens position and corneal curvature and effects on ocular growth. (4)Thus many authors recommend buckle removal after retinal reattachment for better visual outcome.(4,5) In this study we assess the change in refraction following removal/division of the buckle.

Methods:

Data of 18 eyes of 14 infants having ROP who presented between 2008 and 2013, and underwent ESB surgery and subsequent removal or division of the buckle was retrospectively analysed. Staging of ROP was done based on international classification of ROP. Informed consent was taken from the guardians of all infants before any surgical intervention. Following information was collected: Age, sex, birth history (including birth weight, gestational age,type of delivery ,complications and intervention required),stage of ROP at ESB .

Technique of encircling scleral buckle surgery was as follows-Under all aseptic precautions, 360 degree conjunctivalperitomy was done. All four recti were tagged. Partial thickness scleral tunnels were made in all 4 quadrants. Encircling band was passed through the scleral tunnel and underneath the recti. Seven O’ polyester suture was used to tie the buckle knot. Refraction was done under tropicamide(0.5%) and phenylephrine (2.5%) six weeks following the procedure .

Buckle removal was planned at 9-12 month of age ,even earlier in infants with high myopia and later in those with hypemetropic SE. Procedure was as follows; limited conjunctival opening was made in the area of buckle tie and the buckle was either cut/or pulled out .Refraction at six weeks following removal/division and subsequent follow up was noted.

Statistical analysis:

For statistical analysis, SPSS for Windows version 14.0 SPSS was used and p value less than 0.05 was considered statistically significant. As the data was not distributed normally, non-parametric tests were used.

Results:

Eighteen eyes of 13 patients were included. Six (46.2%) of them were males and seven (53.8%) were females. Mean postmenstrual age at presentation was 40.41 weeks (SD=5.76). Mean gestational age at birth was 29.72(SD=2.37 months) .Mean birth weight was 1.36 kg (SD=0.42) .All except one had postnatal respiratory distress syndrome and received supplemental oxygen therapy. Six out of 13 (46.2%) children underwent phototherapy for neonatal jaundice and two (12.5) received blood transfusion.  History of seizures, sepsis and hypothyroidism was present in one patient each. Six eyes (33.3%) received laser photocoagulation (LPC) alone, two (11.1%) received intravitreal injection of anti-vascular endothelial growth factor (Anti-VEGF) alone and five (27.8%) received combination of LPC and anti VEGF prior to ESB surgery. In five eyes (27.8%) no prior intervention was done before ESB. At the time of surgery, all the eyes had ROP stage 4A, with associated APROP in two eyes and plus disease in two eyes. Along with ESB, injection accentrix was given in two patients and Trans scleral cryotherapy was done in 3 patients.

Mean post menstrual age at ESB was 42.47 weeks (SD=4.54) .Silicon band 240 was used in all except three eyes in which 40, 41, 42 band was used. Out of the 18 eyes only 1 eye (5.6%) required Lens sparing vitrectomy six months post ESB, due to traction retinal detachment.

Median age at removal of buckle was 14.97 months .Median interval between the surgery and buckle removal/division was 11.95 months (range =5– 26 months).None of the eyes developed re-detachment following removal/division. Buckle was removed in Toto in all except two eyes in which buckle division was done.

Median follow up was 6.02 years (range 2 -10).

Visual acuity at final follow up was available in 15 eye measured either by Snellens or Lea’s symbol chart. Three eyes with only 2 year follow up had light fixation and following of objects. Nine eyes (60%) had vision better than 6/60. Only two (11.1%) eyes had visual acuity better than 6/12.

ESB was done in both eyes of 5 infants. Other eye of five of the rest eight infants had ROP stage V with no perception/only perception of light. In two of the three infants who had good vision in other eye, anisometropia of 8.75 and 7.5 was observed.

Discussion:

Pre term infants are known to have a myopic refractive state due to their highly curved cornea, shallow anterior chamber, and more spherical lens as compared to full term infants who are hypermetropic .(6) Higher incidence of myopia is also associated with ROP especially beyond stage 3.(7) (8)(9) ESB has also been known to induce myopia , effect being even more pronounced in eyes of premature infants . Thus, despite the well documented anatomical success rates of ESB in ROP, particularly in stage 4A, visual outcomes have been quite disappointing.

Reported retinal reattachment rate following encircling buckle for stage 4A are 67%  by Beyrau et al(9),70% (12 of 17 eyes) by Trese et al (4) , 75% (6 of 8 eyes) by Hinz et al (11)and 100% by  Ratanasukon et al(all eight eyes)(12) and Chow et al(four eyes)(13) .In the present study all except one had successful reattachment following ESB.(94.4%) .

Removal of the buckle after retinal attachment has been advocated by many authors. Trese et al recommend removal 3 months after surgery (4),Mcpherson et al at 6-12 months of age (14) and Choi et al (5) suggested removal in eyes with high myopia with distortion of globe on USG. In this study buckle removal was done at median age of 14.97 months (range 8- 28).

Change in SE with reduction in myopia has been reported earlier in case series by Choi et al and Chow et al. Choi et al did not observe significant change in axial length after buckle removal, and hypothesized that the decrease in myopia could be a result of change in corneal curvature and anterior chamber depth.(5) (13)

Although numerous studies report comparative refractive outcomes of different modalities of treatment for ROP, no study till date has compared the refractive outcome following ESB with laser, LSV or cryoptherapy.

Agarkar S et al, in a study done at the same institute, compared the refractive outcomes after laser in one eye and subsequent lens sparing vitrectomy(LSV) in the fellow eye of 14 infants .Mean birth weight, gestational age and post menstrual age at intervention was comparable with the present study with p values 0.6, 0.723, 0.11 respectively. Refraction at two years in eyes that underwent scleral buckle was not significantly different. (p value for laser 0.978 and  LSV 0.99).(15)

Limitations:

The major limitations of this study were the retrospective nature and small sample size. Definite conclusion regarding the factors contributing to change in SE post buckle removal could not be made due to the lack of biometric analysis. Also a controlled comparison with eyes without scleral buckle removal should have been done but was not possible as buckle removal was done in all the eyes.

Conclusion:

Encircling scleral buckle for ROP stage 4A has excellent anatomical outcome, but unsatisfactory visual outcome. Removal of buckle by significant decrease in myopia may contribute to better functional results. Regular refraction and close follow-up by a paediatric ophthalmologist is required to prevent amblyopia.

References:

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