Analysis of age at detection and outcomes of dense unilateral congenital cataract surgery for children on the paediatric cataract register

Abstract

Aim

Analysis of age at time of detection and surgery of dense unilateral cataract and investigation of best‐corrected visual acuity (BCVA) in a nationwide register‐based cohort study, based on the routine of maternity ward eye screening.

Methods

Data were derived from the Paediatric Cataract Register (PECARE). All children (n = 54) diagnosed with dense congenital unilateral cataract between January 2007 and September 2014 who had surgery before 1 year of age, and for whom 5‐year follow‐up records were available, were included.

Results

The majority, 35/54 (65%), were detected and operated on before age 6 weeks and 30/35 (86%) were referred from maternity wards. Visual acuity (VA) ≥ 0.5 (decimal, 0.3 logMAR) was found in 7/53 (13%) of the cohort at age 5 years; further, 19 children achieved VA ≥ 0.1 (decimal, 1.0 logMAR) (36%) and 19 children VA < 0.05 (decimal, 1.30 logMAR) (36%). Ten‐year follow‐up records were available for 17/53 (32%) children; 1/17 (6%) achieved VA ≥ 0.5 (decimal, 0.3 logMAR), 4/17 (24%) VA ≥ 0.3–<0.5 (decimal, 0.52–0.30 logMAR), 3/17 (18%) VA ≥ 0.05–0.1 (decimal, 1.30–1.0 logMAR) and 10/17 (59%) VA < 0.05 (decimal, 1.30 logMAR).

Conclusion

A total of 90% of the children were detected with cataract within 100 days of birth and 80% were operated on within this period. This study showed better visual acuity in those treated for dense unilateral cataracts than previously reported in an earlier Swedish cohort study.

Abbreviations

BCVA

best‐corrected visual acuity

GDPR

General Data Protection Regulation

HM

hand movements

IATS

Infant Aphakia Treatment Study

IOL

intraocular lens

IoLunder2

United Kingdom perspective inception cohort study of intraocular lens implantation in children aged 2 years or younger

IOP

intraocular pressure

PECARE

Paediatric cataract register

PFV

persistent foetal vasculature

VA

visual acuity

VAO

visual axis opacification

WHO

World Health Organization

Key Notes.

• Swedish congenital cataracts are detected early thanks to a well‐established maternity‐ward screening programme, making early surgery possible.

• Overall, 90% of the children in the study were detected with cataracts within 100 days of birth and 80% were operated on within this period; 37% achieved a best‐corrected visual acuity >= 0.1.

• This study showed better visual acuity in those treated for dense unilateral cataracts than previously reported in an earlier Swedish cohort study.

1. INTRODUCTION

In Sweden, approximately 40 newborns are diagnosed (36/100000 births) with congenital cataract each year ¹ and worldwide, cataracts are the most common cause of treatable blindness in children. ² , ³ The importance of operating on dense congenital cataracts early has been well established. However, the optimum time for surgery has not yet been defined, as it must be taken into account that the rate of complications is higher the earlier surgery is performed. ⁴ , ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³

In general, the visual prognosis for unilateral cataracts is worse than for bilateral cataracts, largely because of competitive inhibition. ¹⁴ , ¹⁵ Ocular comorbidity, especially persistent foetal vasculature (PFV), is more commonly associated with unilateral cataracts and also increases the risk of worse visual outcome. ¹⁵ , ¹⁶

An assessment conducted in Sweden in 2002 showed that ocular screening carried out in the maternity ward was of great importance for early detection of congenital cataracts. ¹⁷ Subsequently, routine eye examinations were implemented at most maternity wards/neonatal units in Sweden. ¹⁸ , ¹⁹ A follow‐up prospective register study published in 2013 continued to show significant benefit from maternity ward screening; the study showed an increase from 19% to 64% in the proportion of congenital cataracts initially identified and referred from maternity wards. ¹⁸

The aim of this nationwide register study was to analyse age at time of detection and visual acuity at 5 and 10 years of age among children registered in The Paediatric Cataract Register (PECARE) who were diagnosed with dense unilateral congenital cataract and had early surgery between 2007 and 2014.

2. METHODS

PECARE is a Swedish National Quality Registry initiated in 2006 that includes all children operated on for cataracts between the ages of 0 and 8 years. ²⁰ Demographic data, age at time of diagnosis and surgery, surgical variables and reasons for patient referral, as well as the individual who initiated primary contact, are reported to PECARE. Treatment outcomes as represented by visual development and occurrence of complications at 1, 2, 5 and 10 years of age are entered for each child.

Since 2012, Swedish infantile cataract surgery has been performed in two main centres covering the whole country. These share approximately 50% of the surgeries each of children younger than 3 years of age, initiated by the Swedish National Board of Health and Welfare. These two centres are located in St Erik Eye Hospital, Stockholm, and Sahlgrenska University Hospital, Gothenburg.

Generally in Sweden, an intraocular lens is implanted in children below 1 year of age when suitable, preferably on normal‐sized eyes. The standard practice in Sweden in the case of an intraocular lens implantation is a post‐operative refractive target aiming for emmetropia at the age of 7. The excessive refraction is corrected with a contact lens overcorrected by approximately +4 dioptres corresponding to 2.8 dioptres in the spectacle plane. Early detection is fundamental for early surgery. Screening for congenital cataract at the maternity ward has been routine in Sweden since the beginning of the 21st century. ¹⁸ Early surgery was defined as surgery prior to 3 months of age in the present study.

This descriptive register study pertained to children diagnosed with dense unilateral congenital cataract whose surgical procedure was entered in PECARE. The diagnosis of dense cataract required that the pupil area had to be covered by the cataract, without being dilated, in normal room lighting and that no red reflex was obtained. Only children operated on before 1 year of age who had 5‐year follow‐up records available were included in the analysis. PECARE has been compared with the Patient Register – the National Board of Health and Welfare health data register in which all surgical procedures carried out in Sweden are entered – for comprehensiveness and has consistently been found to have a high coverage rate, specifically, 90% in the period 2014–2019. ²⁰

Cataracts were assumed to be congenital unless a clear postnatal origin could be demonstrated, such as trauma, uveitis or cortisone treatment. Children diagnosed with partial cataract were excluded. Microphthalmia was defined as axial length <16 mm.

The definition of postoperative glaucoma required surgical treatment for glaucoma due to at least two of the following parameters: intraocular pressure > 21 mmHg, optic disc cupping, corneal findings or progressive refractive shift abnormal when compared with normal growth. Visual field defects, noted when visual field tests were able to be performed, were also included as parameters. ²¹ Furthermore, the definition of visual axis opacification in the study was its presence at a level that required surgical treatment.

Visual acuity (VA) was analysed at 5 and 10 years of age (decimal values). The best‐corrected VA (BCVA) at distance of the afflicted eye was entered in PECARE. The methodology used for assessment of visual acuity included HVOT, LH, KM and KM symbols. ²² , ²³ , ²⁴

The World Health Organization (WHO) defines mild visual impairment as a BCVA ≥ 0.3–<0.5 (decimal, 0.52–0.3 logMAR), moderate visual impairment as a BCVA ≥ 0.1–<0.3, (decimal, 1.0–0.52 logMAR) severe visual impairment as a BCVA ≥ 0.05–0.1 (decimal, 1.3–1.0 logMAR) and blindness as a BCVA < 0.05 (decimal, 1.3 logMAR). The proportion of children with a BCVA ≥ 0.1 (decimal, 1.0 logMAR) was calculated for comparison with a Swedish study from the 2000s. ¹⁴

The initial amblyopia treatment regimen differed slightly between the two surgical centres of Stockholm and Gothenburg. In one of the centres, the healthy eye was patched for 1 h at 1 month of age, 2 h at 2 months of age, etc., until 6 h at 6 months of age or older; in the other centre, patching was performed every second day from morning to night, regardless of age during the first year. Data on patching regimen or evaluation of amblyopia treatment were not registered in PECARE during the study period as part of the register variables.

SPSS, version 25 for Windows (IBM Corp, New York, USA), was used for analysis of all data. Geometric mean visual acuity values were analysed. Because of the small study population containing skewed groups, statistical tests were not performed as the results could not be considered reliable.

The study was performed in accordance with the tenets of the Declaration of Helsinki as well as the General Data Protection Regulation (GDPR) and was approved by The Regional Ethical Review Board in Gothenburg, Sweden (reference number 2020–01964). Patient consent was not obtained before inclusion because of the retrospective nature of this study and was not required for approval by the Regional Board of Ethical Review Board.

3. RESULTS

Data for a total of 623 children were entered in PECARE between 2007 and 2018. A total of 120 operations were performed on children under 1 year of age. Of these, 61 children had been operated on for unilateral congenital cataract and were at least 5 years of age when the data were obtained from the register in March 2019. Seven of these children had no 5‐year follow‐up reported. Of these seven children, two were lost for follow‐up due to emigration. Finally, 54 children were included in the study. One eye was excluded due to enucleation for a suspected tumour. Consequently, the number of eyes evaluated for visual acuity and postoperative complications was 53.

The demographics of the study population are shown in Table 1. These include gender, sender of referral to ophthalmologist, presence of additional eye abnormality, age at time of surgery, and presence and type of intraocular lens. The gender distribution of 22 boys and 32 girls gives a male/female ratio of 0.69 (22/32). In all, 31/54 (57%) of the eyes had at least one additional eye abnormality, of which 13/54 (24%) had microphthalmia and 27/54 (50%) had persistent foetal vasculature (Table 2).

TABLE 1.

Demographics of the study population, n = 54

Sex	Girl	32	59%
	Boy	22	41%
Eye	Left	34	63%
	Right	20	37%
Referred by	MW	34	63%
	CHS	9	17%
	Paediatrics clinic	3	6%
	Parent	8	15%
Additional eye abnormality Δ	No	23	43%
	Yes	31	57%
Age at time of surgery	<6 weeks	35	65%
	>6 weeks	19	35%
Type of IOL	No IOL	23	43%
	AOP‐IOL	22	41%
	BIL‐IOL	8	15%
	ATP‐IOL	1	2%

Abbreviations: AOP‐IOL, Acryl one piece IOL; ATP‐IOL, Acryl three piece IOL; BIL‐IOL, bag in the lens IOL; CHS, child health services; IOL, intraocular lens; MW, Maternity ward; Δ, eye abnormalities presented in Table 1.

TABLE 2.

Characteristics on an individual basis ranked by best‐corrected visual acuity (BCVA) at age 5 years

Patient	Age at time of surgery (days)	Type of IOL	Coexisting eye abnormalities, including systemic illnesses	BCVA methodology age 5 years	BCVA age 5 years Decimal/logMAR	BCVA methodology age 10 years	BCVA age 10 years decimal/logMAR
1	15	None	Microphthalmia, PFV	NLP
2	24	None	PFV, congenital glaucoma, microphthalmia. Detachment at age 1 year	NLP		NLP
3	66	AOP‐IOL	PFV, microphthalmia, ectopic pupil, hyaloid artery	NLP
4	313	None	PFV, Vitreous haemorrhage, Enucleated (suspected tumour)	NLP
5	135	AOP‐IOL	PFV, lenticonus, dense opacification of posterior lenticular capsule >6 months	LP
6	17	None	Microphthalmia, PFV	LP
7	71	AOP‐IOL	PFV, microphthalmia	HM
8	103	AOP‐IOL	Systemic illness	FC 3 decimetres		Letter chart	0.01/2
9	14	None	Microphthalmia, PFV	Unknown	0.01/2	Not entered	0.00/>2.0
10	11	AOP‐IOL		KM	0.01/2	Letter chart	0.05/1.3
11	11	AOP‐IOL		LH	0.01/2	Not entered	0.01/2
12	20	None	Microphthalmia, PFV, Pupillary membrane	LH	0.01/2
13	216	AOP‐IOL		KM	0.01/2	Not entered	0.00/>2.0
14	16	None		LH	0.02/1.7	KM	0.30/0.52
15	17	AOP‐IOL		LH	0.02/1.7	Not entered	0.02/1.7
16	47	AOP‐IOL	PFV	HVOT	0.02/1.7
17	18	None		LH	0.03/1.52	KM	0.03/1.52
18	22	None	PFV	HVOT	0.03/1.52
19	271	AOP‐IOL		LH	0.03/1.52
20	351	BIL‐IOL	Possible developmental delay	HVOT	0.03/1.52	HVOT	0.06/1.22
21	30	None	PFV	KM	0.05/1.3	Letter chart	0.04/1.40
22	19	None	PFV	HVOT	0.05/1.3
23	30	AOP‐IOL		HVOT	0.05/1.3
24	20	AOP‐IOL	Microphthalmia, PFV	HVOT	0.05/1.3
25	320	None	PFV	HVOT	0.05/1.3	KM	0.04/1.40
26	356	AOP‐IOL	Lenticonus, surgery age 11.5 months	LH	0.05/1.3	KM	0.03/1.52
27	23	None	Microphthalmia, PFV	LH	0.06/1.22
28	55	BIL‐IOL	PFV, defect of posterior capsule	KM symbols	0.06/1.22
29	32	None	PFV	LH	0.07/1.15
30	52	None	PFV	HVOT	0.07/1.15
31	77	AOP‐IOL	PFV	HVOT	0.07/1.15
32	29	None	Microphthalmia, PFV	KM	0.08/1.1
33	24	AOP‐IOL		KM	0.08/1.1	KM	0.02/1.7
34	23	None	PFV	LH	0.08/1.1
35	70	None		HVOT	0.08/1.1
36	28	None	Microphthalmia, PFV	HVOT	0.10/1.0
37	14	None	Down's syndrome	TAC	0.12/1.92	Letter chart	0.05/1.3
38	14	None	Lens coloboma	HVOT	0.16/0.80
39	24	None		HVOT	0.30/0.52	KM	0.30/0.52
40	30	BIL‐IOL	Microphthalmia, PFV, embryotoxon	HVOT	0.30/0.52
41	21	AOP‐IOL		KM	0.30/0.52
42	152	BIL‐IOL		KM	0.30/0.52
43	80	AOP‐IOL		LH	0.32/0.49
44	32	None	Microphthalmia, Thickening of posterior capsule, adherent vitreous membrane	HVOT	0.40/0.40	KM	0.30/0.52
45	15	BIL‐IOL	PFV	HVOT	0.40/0.40
46	18	BIL‐IOL	PFV	HVOT	0.40/0.40
47	30	AOP‐IOL		Unknown	0.40/0.40
48	32	AOP‐IOL		LH	0.50/0.30
49	24	AOP‐IOL	PFV	HVOT	0.50/0.30
50	24	AOP‐IOL		KM	0.50/0.30
51	124	ATP‐IOL		HVOT	0.50/0.30	KM	0.50/0.3
52	31	BIL‐IOL	Rounded defect in posterior capsule	HVOT	0.60/0.22
53	300	AOP‐IOL		KM	0.65/0.19
54	16	BIL‐IOL		HVOT	0.70/0.15

Abbreviations: AOP‐IOL, Acryl one piece IOL; ATP‐IOL, Acryl three piece IOL; BCVA, best‐corrected visual acuity (decimal values); BIL‐IOL, bag in the lens IOL; FC, finger counting; HM, hand movements; HVOT, Recognition acuity test based on the letters H, V, O and T; IOL, intraocular lens; KM, KM Chart (Konstantin Moutakis); LH, Lea Test chart (Lea Hyvärinen); LP, light perception; PFV, persistent foetal vasculature; TAC, Teller acuity cards.

Postoperative glaucoma was found in 18/53 (34%) and visual axis opacification in 26/53 (49%). A detailed analysis of the relationship between postoperative complications, age at surgery, co‐existing eye anomalies and visual outcome will be presented in a further study in the near future.

A total of 48 of the 54 children were diagnosed with a cataract within 100 days of birth (89%) and 43/54 (80%) were operated on within 100 days of birth. Among children who were operated on prior to age 42 days, 29/35 (83%) were diagnosed with a cataract before age 7 days (mean 4.8 days, median 3 days). Of those who had surgery after age 42 days, the spread was far greater and only 4/19 (21%) had been diagnosed before age 42 days (mean 100 days, median 71 days). A large proportion of children in the study were referred to an ophthalmologist and operated on prior to age 42 days (39/54 (72%) and 35/54 (65%) respectively) (Table 3). In all, 34/54 (63%) of referrals came from maternity wards. Of those referred and operated on prior to age 42 days, 31/39 (79%) and 30/35 (86%), respectively, were referred from maternity wards.

TABLE 3.

Age at referral to ophthalmologist and age at time of surgery, by time interval

	Referral (days)				Surgery (days)
	<42	42–<100	>100	Total	<42	42–<100	>100	Total
MW	31	2	1	34	30	2	2	34
CHS	2	5	2	9	‐	4	5	9
PC	3	‐	‐	3	3	‐	‐	3
Parents	3	2	3	8	2	2	4	8
Total	39	9	6	54	35	8	11	54

Abbreviations: CHS, child health services; MW, Maternity ward; PC, Paediatric clinics.

A primary intraocular lens was implanted in the majority of eyes, 31/54 (57%). The Acryl one‐piece intraocular lens (AOP‐IOL) was the most common choice, representing 22/54 (41%) of the eyes analysed.

One child who underwent enucleation for a suspected tumour was excluded from the VA analysis. Consequently, the BCVA of 53 children, of whom 23 had no additional eye abnormality, was analysed. The BCVA values at 5 years of age are shown in Figures 1 and 2. Of the 53 children, 7/53 (13%) achieved a BCVA ≥ 0.5, (decimal, 0.3 logMAR) 19/53 (36%) a BCVA ≥ 0.1 (decimal, 1.0 logMAR), and 19/53 (36%) a BCVA < 0.05 (decimal, 1.3 logMAR) (Figure 1).

FIGURE 1.

Best‐corrected visual acuity (BCVA, decimal values and logMAR) at age 5 years, n = 49

FIGURE 2.

Best‐corrected visual acuity (BCVA), decimal values and logMAR), at age 5 years, for children without additional eye abnormalities, n = 20

The median BCVA in the 23 children without additional eye abnormalities was 0.08 (decimal, 1.1 logMAR) (min. 0.01, max. 0.7, mean 0.09 decimal, logMAR: min. 2.0, max. 0.15, mean 1.05). Figure 2 shows the BCVA for the children with no additional eye abnormalities.

The 35 children who underwent cataract surgery before age 6 weeks showed a median BCVA of 0.08 (decimal, 1.1 logMAR) (min. 0.01, max. 0.7, mean 0.1 decimal, logMAR: min. 2.0, max. 0.15, mean 1.0) and the 19 children who had surgery after age 6 weeks showed a median BCVA at age 5 years of 0.06 (decimal, 1.22 logMAR) (min. 0.01, max. 0.65, mean 0.07 decimal, logMAR: min. 2.0, max 0.19, mean 1.15). When analysing only the group of children who had no additional eye abnormalities, the 14 who had surgery prior to age 6 weeks achieved a median BCVA of 0.1 (decimal, 1.0 logMAR) (min. 0.01, max. 0.7, mean 0.09 decimal, logMAR: min. 2.0, max. 0.15, mean 1.05) at age 5 years, while a median BCVA of 0.08 (decimal, 1.1 logMAR) was achieved by the nine children who had surgery after age 6 weeks (min. 0.01, max. 0.65, mean 0.08 decimal, logMAR: min 2.0, max. 0.19, mean 1.1). Six children had a BCVA < 0.01 (decimal, 2.0 logMAR): one was assessed as HM (able to distinguish hand movements), two were assessed as P (perception, able to distinguish between light and dark) and three had no measurable vision. Of these children, three were operated on before and three after age 6 weeks.

BCVA values were entered for 17/53 children at age 10 (Table 2). Among these children, 1/17 (6%) achieved a BCVA ≥ 0.5 (decimal, 0.3 logMAR), 3/17 (18%) a BCVA ≥ 0.3–<0.5 (decimal, 0.52–0.3 logMAR), 3/17 (18%) a BCVA ≥ 0.05–0.1 (decimal, 1.3–2.0 logMAR) and 10/17 (59%) a BCVA < 0.05 (decimal, 1.3 logMAR). The median BCVA at 10 years was 0.04 (decimal, 1.4 logMAR) (min. 0,00 max. 0.5, mean 0.05 decimal, logMAR: min >2.0, max 0,3, mean 1.3).

4. DISCUSSION

The purpose of surgical treatment of unilateral cataract is to offer the child a normal field of vision, a good enough visual acuity and also to reduce the risk of developing strabismus, but the cost must not exceed the benefit. Not all children benefit from surgery. Taylor et al. emphasised that the decision whether or not to treat a monocular cataract is not the surgeon's; it belongs to the parents, who need to familiarise themselves with concepts such as amblyopia, patching and different methods of optical correction. ²⁵ Medical as well as social factors may make surgery not worthwhile. One must also take into account the risk of postoperative complications such as glaucoma, retinal detachment and endophthalmitis. The figure of 34% for postoperative glaucoma in our study represents historical data; at present the glaucoma rate seen in the PECARE has been reduced significantly as a result of new treatment strategies, which will be published in the near future.

The timing of surgery is crucial. You et al. presented data on age at detection and surgery on 309 paediatric cataracts in a study from China in 2011 and found that the mean ages at disease recognition and at surgery were 22.6 ± 30.4 months and 68.3 ± 40.0 months respectively. No patients were operated on before 3 months of age. ²⁶ The median age at surgery in a study from the Democratic Republic of Congo, of 298 children, was 5.7 years and no children were operated on before 1.4 years of age. ²⁷ In a 2020 study from Nigeria of 164 cases, the child's mother detected the cataract in 70.7% of the patients and the median age at presentation for patients with congenital cataract was 18 months. ²⁸

Eye screening is a routine protocol in 90% of Swedish maternity wards and the screening is performed by a paediatrician. ¹⁷ A large percentage of the children in the present study were diagnosed (39/54, 72%) and operated on for their cataracts (35/54, 65%) prior to age 6 weeks. The majority of the total population were referred from maternity wards (35/54, 65%). This observation is in line with the earlier PECARE study concerning congenital cataract detection, which found that 64% of referrals came from maternity wards in Sweden. ¹⁸ , ¹⁹ This screening process has led to earlier diagnosis and surgery for congenital cataract. Compared with regions in Sweden during the 1990s that did not carry out ocular screening on the maternity ward, the figure stood at 19% between 1992 and 1998. ¹⁷ However, our study only included children diagnosed with dense unilateral congenital cataract. A total of 65% were operated on before 6 weeks of age in the present study, compared to 67% in the previous PECARE register analysis published in 2013. This latter study included all types of cataracts. It was obvious in our study that, as well as the hospital paediatricians, parents and community paediatricians and general practitioners at child health services were also important for early referral before 6 weeks of age. Still, 28% were referred and operated on later than this. The reason for this is unknown. The cataracts may have been unobserved at the maternity ward screening. Another reason may be that the cataract had developed further in the days or weeks after birth, and so was not visible at the red reflex examination in the maternity ward. However, congenital cataract is such a rare disease that it is likely that a paediatrician would detect only a few during their working life. From that perspective, the proportion of 34/54 (63%) detected by a non‐ophthalmologist is quite an impressive figure. A total of 48/54 (89%, Table 3) were detected before age 100 days. The proportion is not easily comparable to studies in literature, since the study designs differ. However, Rahi et al. showed in 1999 that 36% of children with the disease in the United Kingdom had it detected at age 4 weeks, rising to 57% at age 3 months. The study measured congenital and infantile cataract detection during the course of 1 year, between October 1995 and September 1996, and included all types of cataracts. ²⁹

Visual acuity at 5 years of age among children operated on for dense unilateral congenital cataract in Sweden between 2007 and 2014 was better compared with children operated on in Stockholm between 1991 and 1996. ¹⁴ A total of 36%, compared with 20%, achieved a VA ≥ 0.1 (decimal, 1.0 logMAR) and 13%, compared with 0%, achieved a BCVA ≥ 0.5 (decimal, 0.3 logMAR). ¹⁴ The reasons for the better results are currently unknown, but may be due to earlier identification of patients through eye screening on maternity wards, which became common practice in the early 2000s. ¹⁸ Furthermore, more of the children in the present study underwent primary intraocular lens implantation than was the case in earlier studies, which may affect the result.

The median value for best‐corrected vision at 5 years of age was lower in this study compared with that measured in the IoLunder2 study, at a minimum of 5 years after cataract surgery, and in the Infant Aphakia Treatment Study (IATS) for patients aged 4.5 years. The median BCVA for this register study was 0.05 (decimal, 1.3 logMAR), for IoLunder2 it was 0.2 (decimal, 0.7 logMAR), and for IATS it was 0.13 (decimal, 0.89 logMAR). ¹² , ³⁰ , ³¹ A study by Bothun et al. of infants undergoing bilateral cataract surgery at 1 to 7 months of age compared the results to the IATS outcome for unilateral cataract surgery. ³² The authors found that the median VA of the better‐seeing eye was 20/40 in 29% of children compared with 17% in the IATS. ³² The difference may in part be due to the exclusion of children with additional eye abnormalities in the IATS and the IoLunder2 study, the results of which may be compared with a BCVA of 0.08 in our group of patients without additional eye abnormalities. ¹² , ³⁰ The IoLunder2 study also investigated BCVA 5 years after surgery, when vision may have developed further than among individuals at age 5 years. ¹²

VA at age 10 years was lower, with a median VA of 0.04 (decimal, 1.4 logMAR) in our study population. This was also lower compared with patients in the IATS, which reported a median VA of 0.12 (decimal, 1.92 logMAR) in the total cohort of patients. ³³ Nominal differences were reported in the IATS between those who underwent intraocular lens transplantation and those who were left without a lens.

More children who underwent cataract surgery prior to age 6 weeks achieved a BCVA ≥ 0.1 (decimal, 1.0 logMAR) compared with those operated on after age 6 weeks. However, the children in our study operated on prior to age 6 weeks did not achieve as good a BCVA as earlier studies in the literature have suggested, nor was the difference between groups based on age at time of surgery as apparent as previously described. ⁸ One explanation may be that children who underwent surgery later were also diagnosed later. It cannot, therefore, be assumed that the cataracts in children operated on after age 6 weeks were dense from birth. This may imply that vision among such children possibly was not as impaired during the first critical weeks of visual development as among children who were diagnosed and operated on early. Differences found among groups based on age at time of surgery may also be attributable to differences in surgical treatment.

This study was based on a comprehensive nationwide register with a high coverage rate, with more than 90% coverage in the last 5 years. Patient attrition was low. Despite the good coverage rate and low patient attrition, the statistical base was relatively small because congenital unilateral cataracts are uncommon and, quite simply, not many children were born with the condition during the relevant time period. Dense congenital cataract is often associated with additional eye abnormalities, which in itself may increase the risk of low BCVA and complications. It may therefore be difficult to interpret treatment results. Nevertheless, treatment outcome specifically for dense cataracts is of great interest because of the importance of early surgery to avoid impairment of visual development. However, it is difficult to obtain a sufficiently large group of children with the sole diagnosis of dense cataract.

Another strength of the study was that treatment outcome was based on patient age rather than on number of years after surgery, which has yielded more accurate and comparable results among individuals as their vision developed. Furthermore, only surgeons with extensive experience operating on paediatric cataracts have treated this group of patients in Sweden.

One limitation of the study was that different methods of assessing visual acuity, which are not always directly comparable, have been used at different clinics. Unfortunately, measuring visual acuity in children can be difficult, even when using uniform methodology, as the results may vary depending on the cooperation of the child at the time of the examination. ³⁴ In addition, it is reasonable to assume individual differences in how each examiner makes the assessment. Furthermore, the extent to which children had been treated with patching was not considered as this was not recorded in PECARE, which may be viewed as an additional limitation. Data regarding amblyopia treatment is planned to be collected in PECARE in the near future.

5. CONCLUSION

Eye screening at maternity wards is still routine practice in Sweden and resulted in early diagnosis and early surgery for a large proportion of the children. A total of 90% of the children were detected with cataract within 100 days of birth and 80% were operated on within this period. At the age of 5 years, 36% achieved a BCVA >= 0.1 (decimal, 1.0 logMAR).

FUNDING INFORMATION

No funding.

CONFLICT OF INTEREST

The authors have no conflicts of interest to declare.

Wackerberg D, Nyström A, Haargaard B, Rosensvärd A, Tornqvist K, Borg L, et al. Analysis of age at detection and outcomes of dense unilateral congenital cataract surgery for children on the paediatric cataract register. Acta Paediatr. 2023;112:277–285. 10.1111/apa.16591