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Paediatric Ophthalmology & Adult Strabismus

Audit and Research  

Strabismus (eye misalignment) surgery

Audits of child and adult strabismus surgery were done in the years 2008, 2009, 2011, 2012 and 2013, and included 1,608 patients. The aims of surgery ranged from improving ocular alignment, cosmesis, eliminating diplopia (double vision) and improving head posture.

Successful ocular alignment was defined as a post-operative esotropia (inward deviation) or exotropia (outward deviation) of 0-10PD or vertical deviation of < 5PD. Cosmesis was achieved if patients and doctors were happy with appearance, and no further surgery was required.

Direct comparisons of success rates between studies is difficult because of differences in how success was defined, and variations in types and degree of strabismus in different studies.

Among the cases done in children (<16 years), our audit showed that the most common types of strabismus were intermittent exotropia (51%), followed by infantile estropia (15%), accommodative esotropia (10%), and superior oblique palsy (6%).

Children with intermittent exotropia and accommodative esotropia achieved ocular alignment in 72%-76%, and cosmesis in 87%-88%; this is compared to success quoted in other studies of 48%-78%. Children with infantile esotropia achieved ocular alignment in 52% and cosmesis in 75%; compared to success rates 30%-80% (with different definitions) noted in other studies.

Among adult strabismus cases, the most common types of surgery included childhood or decompensated comittant strabismus (58%), sensory strabismus due to poor vision in one eye (11%), paralytic strabismus (10%), thyroid eye disease (8%) and residue or consecutive strabismus (i.e. persistent strabismus after past strabismus operation) (6%).

For adults with childhood or decompensated strabismus, ocular alignment was achieved in 75%, and cosmesis in 83%-90%. In those with paralytic strabismus, outcome depended on type (3rd, 4th and 6th nerve palsy) and degree of paralysis, with overall alignment and cosmesis was achieved in 65% and 90%, respectively, while in thyroid eye disease the results were 80% and 84%, respectively. In persons with residue or consecutive strabismus, alignment and cosmesis was achieved in 60% and 80%, respectively.

This compares to success rates of ocular alignment ranging from 68%-85% in other adult strabismus surgery studies. When the reason of performing surgery was to relief diplopia, complete success was achieved in 76% and partial success in 17%; compared to success ranges of 45%-100% in other studies.


Amblyopia

The amblyopia audit was performed in 2010 and included 200 children presenting with amblyopia between 2008 and 2009.

Amblyopia was refractive (79%), strabismic (6%), combined refractive/strabismic (14%), deprivation (1%); and it was unilateral (59%) and bilateral (41%). The most common refractive error was astigmatism (78%), and the most common strabismus was exotropia (60%).

Children with refractive error were more likely to require glasses only, and compliance was best in these children (70%). Children with strabismus and combined refractive/strabismus were more likely to require patching or combined glasses/patches. Compliance in this group fell to 30%-60%; and these children were also more likely to be lost to follow-up. Overall, by nine to 12 months, outcome was good (VA 6/6 or 6/7.5) in 49%, fair (improved by 2 or more lines but not 6/7.5) in 21%, and poor (improved by less than 2 lines) in 9%.

Outcome was best in refractive amblyopia (good-fair in 77%). In combined refractive/strabismus and strabismic amblyopia, outcome was good-fair in 53% and 35%, respectively. This audit helps emphasise the importance of parental education to encourage compliance and patient follow-up.


Atropine for the treatment of Myopia

An audit on the first 386 children started on low dose atropine 0.01% between October 2013 and July 2014 was presented in 2015. The mean age of children at start of treatment was 8.9+/-1.9years, and 88% of children were of Chinese ethnicity. The average myopic degree in these children was -4.94+/-1.91D; and the estimated myopic progression in the last year was 1.98+/-1.16D.

The mean increase of myopia at six and 12 months was -0.53+/-0.73D and -0.59+/-0.80D; similar to that noted in the first year in the Atropine of Treatment of Myopia (ATOM2) study. About 20%-25% progressed >1D over 1 year; a figure which was slightly higher than in ATOM2  (18%).

Younger children and those with less outdoor activity appeared to be at higher risk of myopic progression. Compliance was good in 88.9%. Adverse effect was noted in 9.5% and included glare (6.3%) or stinging of drops (1.9%).
Progress in this group of children will be monitored over the next 1 to 2 years with results to be presented in a future audit.


Paediatric (Childhood) Cataract

This clinical audit was performed annually on all children aged 16 years and younger who underwent cataract surgery at SNEC and KKH; and has included results from 108 children (134 eyes) who had attained the age of at least eight years of age (the age when vision was deemed to be visually mature).

Of these, 72 children were eight years of age or older at time of surgery (Group 1), and 36 children (51 eyes) had cataract surgery before eight years of age (Group 2). Final visual acuity recorded was when child was after two months of surgery (Group 1), or when child had reached eight years of age (Group 2).

The mean age at which children underwent cataract surgery was 6.6 years (range 20 days to 16 years).  Congenital cataracts were the most common type of cataracts (37.5%), followed by developmental (35.9%), traumatic (11.5%) and steroid-related cataracts (8.3%).

In Group 1, 68.6%, 55.7% and 45.7% of children achieved Snellen best-corrected visual acuity of at least or better than 6/18, 6/12 and 6/9 respectively. 

For the children in Group 2, 77.8%, 55.6%, and 50% achieved Snellen best-corrected visual acuity of 6/18, 6/12 and 6/9 respectively. The visual outcome of children who had cataract surgery before two years of age were also similar to those who underwent surgery from two to seven years old (70% vs 75.6% for visual acuity of 6/18 or better).

The visual outcome at the age of eight years was better for bilateral cataracts compared to unilateral cataracts (84.8% vs 55.6% for visual acuity 6/18 or better) and better for developmental cataracts compared to congenital cataracts (68.8% vs 89.7% for visual acuity of 6/18 or better).

Complications within one year of follow up included posterior capsule opacification (14.5%), glaucoma (4.6%) and retinal detachment (1.2%). In Group 1, complications included glaucoma (1.2%), amblyopia (7.2%), and posterior capsule opacification (7.2%).

In Group 2, complications included glaucoma (7.8%), amblyopia (11.7%), and posterior capsule opacification (5.8%). Other causes of poor vision in the group include pre-existing retinal detachment, fibrin formation in intraocular lens (IOL) and a subluxed IOL.

Comparison with other studies is difficult because of difference in age and case-mix. Overall, a best-corrected visual acuity of 6/18 or better was achieved in about 75% of the children in our audit, which compares favourably to other studies, which range between 19% and 63.4%.


Retinopathy of Prematurity (ROP)

The ROP audit of 2007 reviewed 454 premature babies screened for ROP by paediatric ophthalmologists at KKH between 2002 and 2005. 30.8% of babies developed ROP and 5.3% required laser treatment for ROP.
The mean gestational age and birth weights of babies requiring treatment was 25.9+/-1.5weeks and 785+/-12.2g respectively; and the mean age at which babies were treated was at 36.2+/-2.1 weeks. 1.3% of babies progressed to the more severe stage 4-5 ROP.

Over the longer term, children who required laser treatment were more likely to develop amblyopia (2-5x), myopia and astigmatism (2x) than children who did not receive treatment. A repeat audit including babies born between 2005 and 2010 was due in 2016.


Paediatric Electrophysiology

Children who had undergone electrophysiology tests (electroretinogram and visual evoked potentials) between 2003 and 2013 were audited in 2014.

This audit involved 586 children with mean age of 8.2+/-4.3 years (range 3months to 16years). The main reasons for referrals included poor vision of unknown cause (40%), poor vision with suspected retina/optic nerve pathology (17%), confirmation of retina/optic nerve dysfunction (12%), investigation of nystagmus (14%), investigation of visual symptoms (e.g. photosensitivity, night blindness, or visual imagery) (5%), and for screening of drug toxicity (e.g. vigabatrin or hydroxychloroquine), familial genetic disease or assessment of visual potential (12%).

Most children (50%) were found to have a retina problem (e.g. rod-cone, cone, cone-rod dysfunction/dystrophy or maculopathy). 14% had findings suggestive an optic nerve or cortical pathology, 30% returned normal responses, while 6% of results were inconclusive. Overall, this audit found that visual electrophysiology was helpful in the diagnosis and management in children.

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