Amblyopia is the most common cause of impaired vision in children, and childhood cataract is a significant cause of it. Correction of aphakia and visual rehabilitation are important steps in the management of childhood cataract.
Many surgeons implant a posterior chamber intraocular lens (PC IOL) to correct aphakia in children.1–8 This method is especially useful in unilateral cases. Posterior capsule opacification (PCO), if the capsule remains intact, occurs in 51% to 100% of cases in pediatric cataract surgery and prevents visual rehabilitation.3–5,9–11 A neodymium:YAG (Nd:YAG) capsulotomy does not provide a long-lasting clear visual axis because the anterior hyaloid face acts as a scaffold for the growth of lens epithelial cells (LECs).12,13 The transformation of residual LECs results in dense membranes on the anterior hyaloid surface, visual axis reocclusion, haptic displacement, and iris capture.12–14 To provide better conditions for visual rehabilitation, primary posterior capsulotomy and anterior vitrectomy have been recommended.3,5,7,15,16
There are 2 approaches to primary posterior capsulectomy and anterior vitrectomy: through the limbus3,7 and through the pars plana.5 We conducted a clinical trial to compare the results of these 2 approaches.
Patients and Methods
A sequential, matched, randomized, double-masked clinical trial was performed. The indications for cataract surgery in children were defined as any lens opacity that caused decreased visual acuity (20/60 or worse), stereopsis disturbance, deviation of the eyes, or all 3. The eyes were randomly assigned to be operated on using Technique A (limbal approach) or Technique B (pars plana approach).
Cases of developmental cataract were subdivided into 2 groups: (1) zonular cataract; (2) other variations of developmental cataract. Cases of traumatic cataract were also subdivided into 2 groups: (1) associated with corneal laceration; (2) unassociated with corneal damage.
In cases of bilateral developmental cataract, each eye was the control of the fellow eye. The randomization schedule determined which technique was to be used in the first eye having surgery. In unilateral cases, a randomization schedule also determined the approach.
Four statistical frames were prepared: (1) traumatic cataract without corneal damage; (2) traumatic cataract with corneal damage; (3) developmental cataract of zonular type; (4) developmental cataract of other types. The eligible cases were entered sequentially in related frames according to the type of cataract and the results of randomization.
Cases of bilateral or unilateral developmental cataract or traumatic cataract were sequentially included in the study. The indication for cataract surgery was approved by at least 2 physicians independently. The minimum age was 3 years in unilateral cases and 5 years in bilateral cases. The maximum age was 10 years in both unilateral and bilateral cases. Traumatic cases with a history of surgery other than primary repair and cases with ocular hypotony were excluded. Eyes with scleral laceration, vitreous prolapse into the anterior chamber, signs of endophthalmitis and intraocular foreign bodies, or cataract associated with ocular or systemic disease were excluded. The presence of posterior synechias did not result in exclusion.
An A-scan was used for PC IOL power calculation to achieve emmetropia postoperatively. The refraction in the fellow eye was considered, and anisometropia of more than 3.0 diopters (D) was avoided. The PC IOL type was identical in all cases: single-piece poly(methyl methacrylate).
All cases were operated on using general anesthesia and were performed by 1 of 3 surgeons (M.A.J., B.E., F.K.). Mydriatic drops, instilled before surgery, included tropicamide 1% (3 times) and phenylephrine 2.5% to 5% (1 time). A fornix-based peritomy was done and a 100 degree midlimbal groove made. Two stab incisions were created 120 to 150 degrees apart. An anterior capsulotomy was made with a needle and enlarged to 6.0 mm with a vitrectomy probe. Lens material was aspirated. This part of the procedure was similar in all cases, but the surgery then continued differently based on the technique used.
Posterior capsulotomy was done with a 23 gauge needle and then enlarged to 3.0 to 4.0 mm with a vitrectomy probe. An anterior vitrectomy was done through the posterior capsulotomy site. It was confirmed that no vitreous was present at the level of the pupillary area. Then, a limbal groove was opened into the anterior chamber with corneal scissors. After injection of a viscoelastic material, the IOL was implanted in the capsular bag. Peripheral iridectomy was done, and the wound was closed with interrupted 10-0 nylon sutures.
The limbal groove was opened into the anterior chamber with corneal scissors. After injection of a viscoelastic material, the IOL was implanted in the capsular bag. The wound was temporarily closed with 3 separate 8-0 silk X-sutures. A sclerotomy was made 2.5 mm from the limbus in 1 superior quadrant. The infusion cannula was placed in the anterior chamber and the vitrectomy probe in the anterior vitreous cavity. A 3.0 to 4.0 mm posterior capsulectomy was made and an anterior vitrectomy performed, after which the sclerotomy site was repaired with a 7-0 polyglactin (Vicryl®) X-suture. The temporary X-sutures of the cataract wound were removed, a peripheral iridectomy was done, and the wound was closed with interrupted 10-0 nylon sutures.
In all cases, a subconjunctival injection of 20 mg of gentamicin and 4 mg of betamethasone and a sub-Tenon's injection of methylprednisolone acetate 20 mg were given.
Follow-up, which was 1 year, was done by 1 physician who was masked to the surgical technique used. Written consent was obtained from all patients before enrollment, but they too were masked concerning technique. Follow-up forms were completed 1 and 3 days, 1, 3, and 6 weeks, 3 and 6 months, and 1 year after surgery.
The type and dosage of postoperative medications, especially the frequency of topical steroids and necessity for systemic steroids, depended on the degree of inflammatory reaction in each eye. Medications on the first postoperative day were a betamethasone drop every 1 to 4 hours according to the severity of inflammation, sulfacetamide 10% every 6 hours, short-acting mydriatics if needed, and oral prednisolone if needed (1 mg/kg a day).
In all cases, fluorescein angioscopy was performed using general anesthesia 4 to 6 weeks after surgery by2 physicians (M.H.D., A.M.) masked as to surgical technique. An intravenous injection of 5 cc fluorescein sodium 10% was given. Indirect ophthalmoscopy was performed with a blue filter and a 20.0 D lens. Fundoscopy and refraction were done during the same session. Suture removal was performed according to the results of refraction and keratometry.
Eyes were classified according to the visual acuity: (1) light perception (LP)/hand movement (HM); (2) finger counting (CF); (3) 20/200 to 20/120; (4) 20/80 to 20/40; (5) 20/30 or better. Changes in visual acuity were evaluated by comparing preoperative and postoperative visual acuities, with the difference determined by the degree of visual acuity improvement postoperatively, which was shown by a plus (+) sign. For example, a preoperative visual acuity of HM changing to postoperative acuity of CF was a +1 improvement and preoperative visual acuity of HM changing to postoperative acuity of 20/120 was a +2 improvement. Thus, the range of improvement was +1 to +4.
Eyes were also classified according to the estimated red reflex: (1) LP or HM; (2) CF; (3) 20/200 to 20/50; (4) 20/40 to 20/25; (5) 20/25 or better. The estimated postoperative red reflex was compared with the estimated preoperative red reflex, and the difference determined the degree of improvement. Improvement in postoperative red reflex was shown as a plus sign in the same manner as the visual acuity evaluation.
Occlusion therapy was used to treat amblyopia. Therapy began before the surgery if possible. If not, it started within 1 week after surgery. Therapy comprised 1 week per 1 year of age of full-time patching followed by maintenance therapy. Every 3 months, full-time patching was repeated on the same schedule according to patient response.
The study included 45 eyes of 31 patients, 14 of whom had bilateral surgery. In the other 17 patients, the cataract was unilateral, or if bilateral, surgery was indicated in 1 eye only. Mean patient age was 6.3 years ± 2 (SD).
A t test showed no statistically significant difference between the 2 groups in age. Nineteen patients were girls. Chi-square analysis showed no significant difference between the 2 groups in sex.
Of the 45 eyes, 39 eyes of 25 patients had developmental cataract and 6 patients had unilateral traumatic cataracts. Of 39 eyes with developmental cataract, 20 had zonular cataract. All traumatic cataracts were associated with corneal damage. Repair of corneal laceration was not required in 2 eyes because the small laceration self-sealed. The interval between primary repair of corneal laceration and lensectomy was 3 to 6 weeks except in 1 case with an intumescent lens, in which cataract surgery was done 10 days after corneal laceration repair.
Of 45 eyes, 2 (1 each in Techniques A and B) were excluded because of postoperative trauma necessitating deep vitrectomy and IOL removal. Five patients were excluded for inadequate follow-up. Distribution of the remaining 38 cases was as follows: 20 eyes with developmental cataract of zonular type, 14 with developmental cataract of other types, and 4 with traumatic cataract associated with corneal laceration (Table 1).
The 38 matched cases were compared according to visual acuity and estimated red reflex before and after surgery, postoperative intraocular inflammation (fibrin formation in the anterior chamber), posterior synechias, IOL position, corneal status, glaucoma, cystoid macular edema (CME), anterior vitrectomy and posterior capsulectomy quality, status of retinal periphery, and postoperative refraction.
The postoperative increase in visual acuity was significant in both groups. Of the 27 eyes of 19 patients who could cooperate in visual acuity determination with an E-chart before and after surgery (16 and 11 eyes in Techniques A and B, respectively), 24 had a visual acuity worse than 20/200 before surgery, whereas 1 eye had this acuity after surgery. The cause of decreased visual acuity in this case was deep amblyopia unresponsive to proper occlusion therapy. Table 2 shows visual acuity according to the 2 techniques used. There were no statistically significant differences between the 2 techniques in visual acuity improvement.
The improvement in estimated red reflex was also significant. Red reflex was evaluated in 45 eyes. Red reflex worse than 20/200 was present in 41 eyes before surgery. After surgery, red reflex was better than 20/40 in all eyes. Table 3 shows the effect on red reflex based on technique. There was no statistically significant difference between the techniques in improvement.
In no case did complications such as CME, glaucoma, retinal tear, IOL dislocation, corneal edema, or an increased cup-to-disc ratio occur. Iris capture occurred in 1 case (zonular cataract, Technique B). One eye in each group developed posterior synechias of less than2 clock hours. Although fibrin formation was more common with Technique B than A, chi-square analysis showed that the difference was not statistically significant (Table 4).
Posterior capsulectomy smaller than 3.0 mm was considered inadequate. In the Technique A group, the visual axis was occluded in 1 eye. In other cases with small capsulectomy size, refraction was difficult but did not interfere with vision. The case with the occluded visual axis had an Nd:YAG capsulotomy 3 months after surgery. Inadequate capsulectomy was 3 times more common with Technique A than Technique B; however, the Fisher exact test showed the difference was not statistically significant (Table 5).
Refraction was performed at the last examination. In all cases, mean astigmatism after surgery was 1.75 D, with the type being with the rule. Postoperative mean spherical equivalent with Technique A was –0.64 ± 1.02 D and Technique B, –0.76 ± 1.59 D. A t test analysis showed the difference was not statistically significant.
The most important goal in pediatric cataract surgery is to provide ideal visual rehabilitation. There is an increasing tendency toward IOL implantation in children to correct aphakia. The success rate of such implantation is improving and the complication rate decreasing because of new surgical techniques and improved IOL quality.
Even though more recent studies have shown encouraging results of pediatric IOL implantation, caution in selecting patients for this procedure is crucial, especially in very young children. Visual rehabilitation of unilateral aphakic children is more challenging than bilateral cases. Thus, the minimum age for which IOL implantation should be considered in unilateral cases of pediatric cataract is lower than that for bilateral cases.2,9,12,17 In a survey, the mean age for IOL implantation in children was 3 years in unilateral cases and 5 years in bilateral cases.17 The minimum ages in our series were the same. The maximum age was 10 years in both unilateral and bilateral cases.
In calculating IOL power, we aimed for emmetropia and minimizing anisometropia. This is an important factor in visual rehabilitation in children. The correct IOL power leads to more successful amblyopia treatment and increases the chance of binocularity in this critical age period. In other series, however, different approaches have been considered in IOL power calculation. In 1 study, 5 undercorrection was the goal in patients younger than 9 years. In another,7 undercorrection was considered only in children 4 years or younger. The undercorrection was an attempt to neutralize the myopic shift that can occur in growing children.
Other authors believe that achievement of emmetropia is vital in patients with a pliable visual system and that its benefits outweigh the consequence of subsequent myopia.3,4 The growth of the globe is almost complete at 2 years of age.18 Thus, the myopic shift in children 3 years and older would be expected to be less. In our series, postoperative refraction was within the range of emmetropia, as planned, and there was no statistically significant difference between the 2 techniques in postoperative refraction.
To provide a clear media for visual rehabilitation, primary posterior capsulectomy has been recently recommended. Several approaches to prevent or delay PCO have been studied. Primary posterior capsulotomy with a needle or a vitrectomy cutting device, a limbal or pars plana approach anterior vitrectomy, and primary posterior continuous curvilinear capsulorhexis (PCCC) are some techniques that have been evaluated.5,7,15,16,19,20 The capsulotomy edge produced by continuous curvilinear capsulorhexis is smooth.21 Nevertheless, performing PCCC is technically difficult.16 Capsulorhexis of the anterior capsule in young patients is even more difficult than PCCC.16 We used a vitrector to perform capsulectomies in both capsules, followed by anterior vitrectomy. We found this technique easy and reproducible.
There is no agreement whether the IOL should be implanted before or after the primary posterior capsulectomy and anterior vitrectomy. Some advocate removing the posterior capsule and anterior vitreous before IOL implantation.3,7 This can be performed by an anterior segment surgeon or a pediatric ophthalmologist. The anterior vitrectomy can be done in a well-controlled manner under good visibility.15 When the anterior vitrectomy is done, in-the-bag IOL implantation is easily achieved. Dahan and Salmenson3 found no serious complications using this technique in 80 children.
Other surgeons prefer to have the IOL in place before removing the posterior capsule5 to allow for an adequate posterior capsulectomy and a better anterior vitrectomy. The advantage of implanting the IOL before the posterior capsulectomy is that the IOL can be safely fixated in the desired plane. The risk of the IOL being pushed out of the capsular bag may be minimized by keeping the infusion in the anterior chamber. Buckley et al.,5 in a prospective study, used a technique that involved endocapsular cataract extraction and PC IOL implantation. However, the posterior capsulotomy and anterior vitrectomy were performed through the pars plana in the 20 patients, all with unilateral cataract. Visual axis clarity was rapidly restored in all patients without further intervention. The authors concluded that there was a considerable advantage to having the lens in place before removing the posterior capsule.
In an attempt to determine whether the IOL should be implanted before or after posterior capsulectomy and anterior vitrectomy, an experimental study was done using pediatric autopsy eyes.22 This study found that both techniques were feasible in a clinical setting. We compared the limbal and pars plana approaches in a clinical trial. In our study, the visual results were encouraging, and there was no significant difference between the 2 techniques in postoperative improvement in visual acuity. As well as providing a clear media and optical correction, the aggressive amblyopia therapy was an important factor in achieving such results in our patients.
Estimation of the red reflex is a valuable method of evaluating media clarity. There was considerable improvement in red reflex after the surgery and no difference between the 2 techniques in improvement in postoperative estimated red reflex.
There is usually a considerable amount of inflammatory reaction after cataract surgery and IOL implantation in children.2,7,15 To reduce postoperative inflammation, we gave a sub-Tenon's injection of methylprednisolone acetate at the end of surgery in all cases. Nevertheless, fibrin formed in 9 eyes in the early postoperative days. The inflammatory reaction was controlled with frequent instillation of topical steroids and oral prednisolone. The technique used had no significant influence on the amount of postoperative inflammation.
Iris capture, adhesion of the iris to the IOL, and posterior synechias have been reported frequently after pediatric cataract surgery and PC IOL implantation when the procedure is not associated with primary posterior capsulectomy and anterior vitrectomy.2,8,23 Anterior vitrectomy reduces the rate of such complications,5,7 which were uncommon in our series. There was no significant difference between the 2 techniques in the occurrence of such complications.
One objective of primary posterior capsulectomy and anterior vitrectomy is providing long-term clarity of the visual axis. We considered the primary posterior capsulectomy inadequate if it was smaller than 3.0 mm in diameter. This was observed in 4 cases, but only 1 eye required an Nd:YAG capsulotomy. This complication was more common in the limbal approach group, but the difference between techniques was not statistically significant.
The advent of the vitrectomy machine reduced the rate of retinal detachment as a late complication of pediatric cataract surgery. Keech and coauthors24 reported 1 case of retinal detachment 6 years after translimbal lensectomy and anterior vitrectomy. No retinal detachment was observed in our series. To properly evaluate the effect of technique on the occurrence of retinal detachment, long-term follow-up is needed.
Cystoid macular edema has an effect on visual rehabilitation of children who have lensectomy and IOL implantation. Hoyt and Nickel25 observed CME in 10 of 27 cases of developmental cataract after lensectomy and vitrectomy. Poer and coauthors26 observed no CME in a study of 25 eyes of 18 patients after surgery for management of infantile cataract. Gilbard and coauthors27 reported no CME in 25 eyes of 17 children who had pars plicata lensectomy and vitrectomy. In a study by Pinchoff and coauthors,28 fluorescein angiography performed 4 to 16 weeks after translimbal lensectomy and vitrectomy revealed no CME. Morgan and Franklin29 performed oral fluorescein angiography 3, 6, and 24 weeks after the surgery in patients from 2 months to 7 years and observed no macular leakage. In our series, fluorescein angioscopy was performed 4 to 6 weeks after the surgery, with no CME observed.
Different mechanisms for glaucoma in children after cataract surgery have been proposed. Performing lensectomy and vitrectomy permits complete removal of lens material and minimizes postoperative inflammation and consequent pupillary block. In a study with short-term follow-up, no case of glaucoma was observed in children having lensectomy with a vitrectomy machine. When the follow-up was continued, it became obvious that glaucoma may threaten the vision of children who have lensectomy and vitrectomy years after the surgery.30,31 Recent studies show that the incidence of glaucoma after surgical management of infantile and developmental cataract depends on the duration of follow-up.30,32 In our study, there was no difference between the 2 techniques in the occurrence of glaucoma. Nevertheless, long-term follow-up is needed to make a judgment about the possible effect of technique on the occurrence of glaucoma.
In conclusion, when the intervening and background variables were matched there were no statistically significant differences between the limbal and pars plana approaches and the visual and anatomic results were encouraging in both groups. In addition, the rate of complications was minimal and did not differ significantly between techniques.
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