Long-term Risk of Glaucoma After Congenital Cataract Surgery




Purpose


To report the long-term risk of glaucoma development in children following congenital cataract surgery.


Design


Retrospective interventional consecutive case series.


Methods


We retrospectively reviewed the records of 62 eyes of 37 children who underwent congenital cataract surgery when <7 months of age by the same surgeon using a limbal approach. The Kaplan-Meier method was used to calculate the probability of an eye’s developing glaucoma and/or becoming a glaucoma suspect over time.


Results


The median age of surgery was 2.0 months and the median follow-up after cataract surgery was 7.9 years (range, 3.2-23.5 years). Nine eyes (14.5%) developed glaucoma a median of 4.3 months after cataract surgery and an additional 16 eyes (25.8%) were diagnosed as glaucoma suspects a median of 8.0 years after cataract surgery. The probability of an eye’s developing glaucoma was estimated to be 19.5% (95% CI: 10.0%-36.1%) by 10 years after congenital cataract surgery. When the probability of glaucoma and glaucoma suspect were combined, the risk increased to 63.0% (95% CI: 43.6%-82.3%).


Conclusions


Long-term monitoring of eyes after congenital cataract surgery is important because we estimate that nearly two thirds of these eyes will develop glaucoma or become glaucoma suspects by 10 years after cataract surgery.


Glaucoma is one of the most serious complications occurring after infantile cataract surgery. It is usually open-angle and can develop during the immediate postoperative period or years later. Although early cataract surgery has been shown to be associated with improved visual outcomes, it has also been reported to increase the risk of developing glaucoma. A wide range of cumulative incidences of glaucoma has been reported following infantile cataract surgery. However, it is difficult to directly compare these studies because of their differing inclusion criteria and lengths of follow-up. Moreover, some studies used national registries or data from multiple institutions and, as a result, surgical techniques and follow-up examinations were not standardized. Furthermore, these studies differed in how they defined “glaucoma.” Some studies defined glaucoma solely on the basis of an elevated intraocular pressure (IOP), while other studies based the diagnosis on whether treatment had been initiated for glaucoma. Studies that based the diagnosis solely on elevated IOP may have over-diagnosed glaucoma, since there can be a lag between modestly elevated IOP and clinically significant optic disc deterioration or visual field abnormalities. In addition, the thicker corneas of aphakic eyes introduce a potential source of measurement error when using IOP alone as a criterion for diagnosing glaucoma.


The aim of the current study is to report the long-term cumulative incidence of glaucoma in a cohort of children who all underwent congenital cataract surgery when <7 months of age by the same surgeon (S.R.L.) using a modern surgical technique with follow-up care provided by a pediatric ophthalmologist and a pediatric glaucoma specialist.


Methods


This retrospective interventional consecutive case series was carried out with prospective approval from the Institutional Review Board at Emory University and in accordance with Health Insurance Portability and Accountability Act regulations. Informed consent was obtained from all study participants or their parents, in the event the children were minors. In addition, assent was obtained from all minors who were ≥6 years of age. Patients for the study were identified by reviewing the surgical logs of one of the authors (S.R.L.) and searching the Emory Clinic database for all patients who underwent unilateral or bilateral cataract surgery when <7 months of age between 1988 and 2010 and performed by S.R.L. The main inclusion criteria were undergoing unilateral or bilateral cataract surgery when <7 months of age with a minimum follow-up of 3 years. Exclusion criteria included participation in the Infant Aphakia Treatment Study (a randomized clinical trial that is still ongoing) and syndromes associated with an increased risk of glaucoma. Data were extracted from the medical records and then entered on case report forms. Data entered on the case report forms included birth weight, type of cataract, date of cataract surgery, laterality, primary or secondary intraocular lens (IOL) implantation, refractive error, highest IOP (Tmax), the most recent central corneal thickness (CCT), cup-to-disc (C/D) ratio when diagnosed with glaucoma, axial length, visual field findings, date and type of glaucoma surgery, length of follow-up and glaucoma medications being taken, and C/D ratio and visual acuity at the last follow-up examination. The case report forms were then faxed and entered into a database.


Surgical Procedure


All of the surgeries were performed using a limbal approach. After making 2 stab incisions, an infusion cannula was placed through 1 incision and a vitreous-cutting instrument though the other. The vitreous-cutting instrument was then used to create an anterior capsulectomy 5 mm or greater in diameter, to aspirate the lens nucleus and cortex, to create a posterior capsulectomy 4 mm or greater in diameter and to perform an anterior vitrectomy. If an IOL was implanted, the wound was enlarged and the IOL was implanted into the capsular bag. The incisions were then closed with absorbable sutures. Postoperatively, patients were treated with topical antibiotics and atropine for 1 week and corticosteroids for 4 weeks.


Diagnosis of Glaucoma and Glaucoma Suspect


Glaucoma was defined as IOP >21 mm Hg with 1 of the following anatomic changes: (1) corneal enlargement; (2) asymmetrical progressive myopic shift coupled with enlargement of the corneal diameter and/or axial length; and (3) increased optic nerve cupping, defined as an increase of ≥0.2 in the C/D ratio or the use of a surgical procedure for IOP control. Glaucoma suspect was defined as either: (1) 2 consecutive IOP measurements on different dates >21 mm Hg after topical corticosteroids had been discontinued, without the anatomic changes listed above; or (2) the use of glaucoma medications to control IOP, without the anatomic changes listed above. The date that these findings were first detected on clinical examination was defined as the onset date of glaucoma or glaucoma suspect.


Prior to 2008, IOP was measured in young children using a Tonopen (Reichert, Depew, New York, USA), pneumotonometry (Reichert), or a Perkins tonometer (Haag-Streit, Bern, Switzerland). In some cases, an examination under anesthesia was performed to measure IOP in uncooperative children. Goldmann applanation tonometry was generally used to measure the IOP in older children and some cooperative younger children. Since 2008, rebound tonometry (Icare, Helsinki, Finland) has been the preferred instrument for measuring IOP in young children at our institution. CCT was measured using a handheld pachymeter (DGH 55 Pachmate; DGH Technology, Exton, Pennsylvania, USA).


All patients diagnosed with glaucoma or glaucoma suspect were treated by a pediatric glaucoma specialist.


Statistical Analysis


Descriptive statistics were calculated for person-level characteristics on the 37 patients and for eye-level characteristics on the 62 eyes. A Kaplan-Meier method was used to calculate the probability of glaucoma and glaucoma suspect, as well as the respective 95% confidence intervals, on a per-eye basis. Prior to conducting any inferential analyses, the McNemar test was used to check for independence in glaucoma diagnosis between the left and right eyes of patients. Since no significant dependence was found ( P = .25), the eyes were treated independently. SAS 9.3 (SAS, Cary, North Carolina, USA) was used for all statistical analyses.


Visual acuity data were analyzed by converting to logMAR notation and calculating the median, which was then transformed back to the Snellen equivalent. The data were stratified by laterality. Values recorded as central, unsteady, maintained (CUSM) or central, steady, maintained (CSM) were excluded from the analyses (2 patients).




Results


The records of 85 patients who underwent unilateral or bilateral cataract surgery when <7 months of age between 1988 and 2010, performed by S.R.L., were reviewed. All of the eyes had IOP ≤21 mm Hg at the time of cataract surgery. Nine patients were excluded from the analysis because they were enrolled in the Infant Aphakia Treatment Study. Another 4 patients were excluded because they have syndromes known to be associated with an increased risk of glaucoma (Lowe syndrome, n = 3; microphthalmos, dermal aplasia, and sclerocornea [MIDAS] syndrome, n = 1). The remaining excluded patients were either receiving their ophthalmic care elsewhere (n = 34) or unwilling to sign the informed consent (n = 1). Thirty-seven patients and 62 eyes were enrolled in the study. Patients’ median birth weight was 3480 g (interquartile range, 3260-3748 g). The patients underwent cataract surgery at a median age of 58 days (range, 5-210 days). Forty-four of the cataracts were nuclear, 6 were total, 5 were posterior lentiglobus, 4 lamellar, 2 posterior polar, and persistent fetal vasculature. The median follow-up was 7.9 years (range, 3.2-23.5 years). There were 11 patients (29.7%) who underwent unilateral cataract surgery and 26 (70.3%) who underwent bilateral cataract surgery. One patient with bilateral cataracts had one eye excluded because cataract surgery was performed at >6 months of age in one eye. Six eyes underwent primary IOL implantation and the other 56 eyes were left aphakic. The aphakic eyes were initially corrected optically with contact lenses or glasses. Seventeen of these eyes later underwent secondary IOL implantation at a mean age of 4.0 ± 0.6 years. All of the IOLs implanted were Acrysof IOLs (models SA60AT, SN60AT, SN60WF, MN60AC, MA30AC) (Alcon Surgical, Fort Worth, Texas, USA). Three patients had trisomy 21. After cataract surgery, none of the eyes underwent any other intraocular surgical procedures other than the implantation of a secondary IOL or glaucoma surgery.


Nine eyes developed open-angle glaucoma ( Table 1 ). No eyes developed angle-closure glaucoma. Three patients had bilateral and 3 patients had unilateral glaucoma. Only 1 of the 3 patients with unilateral glaucoma underwent cataract surgery in both eyes. Cataract surgery was performed at a median age of 5 weeks (range, 3-13 weeks) in these eyes. Glaucoma was diagnosed in the first postoperative year in 5 eyes, at the age of 2 years in 2 eyes, and at the age of 8 years in 2 eyes. The probability of an eye’s developing glaucoma was estimated to be 19.5% (95% CI: 10.0%-36.1%) by 10 years after cataract surgery ( Figure ). We did not find a significant difference in the risk of developing glaucoma and the age at cataract surgery when stratified at ≤6 weeks vs >6 weeks, ≤2 months vs >2 months, and ≤3 months vs >3 months. However, the power to find such a difference was low because of the limited number of patients in each of these age groups.



Table 1

Clinical Findings of Glaucoma Eyes After Congenital Cataract Surgery




























































































































Patient Eye Age at Cataract Surgery (wk) Age Glaucoma Diagnosed (mo) Age at Glaucoma Surgery (mo) Buphthalmos Tmax (mm Hg) CCT (μm) Number of Glaucoma Medications at Last Examination C/D Ratio Glaucoma Diagnosed C/D Ratio at Last Examination
1 OD 5 12 13 Y 37 575 0 0.1 0.1
11 OD 8 33 37 Y 36 NA 3 0.1 0.2
11 OS 8 30 29 Y 45 NA 3 0.6 0.8
12 OD 4 2 7 Y 38 832 3 0.5 0.8
12 OS 4 2 6 Y 39 801 3 0.5 0.7
13 OD 12 7 7 Y 42 557 0 0.4 0.3
14 OD 3 3 3 Y 35 528 0 0.6 0.1
15 OD 5 100 151 N 47 644 3 0.5 0.6
15 OS 4 100 133 N 51 667 3 0.5 0.55

CCT = central corneal thickness; C/D = cup-to-disc; N = no; Tmax = highest intraocular pressure measured; Y = yes.



Figure


Kaplan-Meier curves showing cumulative probability of an eye’s developing glaucoma (dashed line) and glaucoma suspect or glaucoma (solid line) after congenital cataract surgery over time. The number of eyes at risk at each 5-year time interval are shown below the x-axis.


All of the eyes diagnosed with glaucoma were initially treated with glaucoma medications. However, because of progressive buphthalmos or glaucomatous optic neuropathy coupled with uncontrolled IOP, all of these eyes subsequently underwent glaucoma surgery. At the time of glaucoma surgery, all of these eyes had microcystic cornea edema except for those of Patient 15, who was older when he presented with glaucoma. Three eyes underwent a suture trabeculotomy and 6 eyes had an Ahmed shunt implanted (New World Medical, Rancho Cucamonga, California, USA). None of the eyes underwent any additional glaucoma surgeries. Six of the 9 eyes continue to require 3 medications to control IOP. One eye underwent primary IOL implantation at the age of 3 weeks and was diagnosed with glaucoma at age 3 months. None of the other eyes that developed glaucoma underwent primary IOL implantation. Tmax in these eyes was a median of 39 mm Hg (range, 35-51 mm Hg).


Sixteen eyes had elevated IOPs without progressive ocular enlargement or optic disc cupping and were diagnosed as glaucoma suspects ( Table 2 ). These eyes underwent cataract surgery at a median age of 7.5 weeks (range, 1-15 weeks). They were diagnosed as glaucoma suspects at a median age of 7.5 years (range, 1.5-13 years). The probability of an eye’s developing glaucoma or glaucoma suspect was estimated to be 63% (95% CI: 43.6%-82.3%) by 10 years after congenital cataract surgery ( Figure ). Tmax in the glaucoma suspect eyes was a median of 31 mm Hg (range, 25-39 mm Hg). Glaucoma medications were started to lower the IOP in all of these eyes. Fourteen of these 16 eyes currently have their IOP controlled by taking a mean of 1.78 (range, 1-4) glaucoma medications each day. The other two eyes had their medications discontinued after being treated with 1-3 glaucoma medications daily for 5-6 years; their IOP has remained in the normal range. None of these 16 eyes had increased cupping of their optic discs, and all visual fields have been normal. Four of the glaucoma suspect eyes underwent secondary IOL implantation; 2 eyes had ocular hypertension when secondary IOL implantation was performed and 2 eyes developed ocular hypertension 5 years later.



Table 2

Clinical Findings of Glaucoma Suspect Eyes After Congenital Cataract Surgery





























































































































































Patient Eye Age at Cataract Surgery (wk) Age Diagnosed Glaucoma Suspect (y) Tmax (mm Hg) CCT (μm) Number of Glaucoma Medications at Last Examination C/D Ratio at Last Examination
1 OS 6 1 1/2 25 636 0 0.1
2 OD 6 13 38 NA 1 0.1
2 OS 6 13 34 NA 1 0.1
3 OD 11 1 35 648 1 0.3
3 OS 11 3 1/2 38 626 1 0.3
4 OD 6 1/2 28 652 0 0.2
5 OD 15 7 1/2 32 634 3 0.4
5 OS 15 7 1/2 36 648 3 0.25
6 OD 13 9 28 632 1 0.65
6 OS 14 10 25 698 1 0.7
7 OD 1 7 1/2 28 723 1 0.55
7 OS 1 7 1/2 28 683 1 0.7
8 OD 4 2 28 710 2 0.3
8 OS 4 2 30 714 2 0.3
9 OD 12 9 38 737 4 0.25
10 OS 9 10 36 631 3 0.15

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Jan 9, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Long-term Risk of Glaucoma After Congenital Cataract Surgery
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