Experts debate the best approach for high AC:A ratio accommodative esotropia – surgical or non-surgical
Clinicians debated the relative merits of non-surgical management versus surgical management for high AC:A ratio accommodative esotropia at a session of the World Congress of Paediatric Ophthalmology and Strabismus in Hyderabad, India.
Dr David Newsham, Head of Orthoptics and Vision Science, University of Liverpool, UK, arguing in favour of non-surgical treatment, said that the first aim was to establish diagnosis and classification, determine refractive error (predominantly hypermetropia – usually between 1.5-5 dioptres), measure visual acuity (usually equal in both eyes and without amblyopia unless anisometropia is present), check for amblyopia and establish the level of control of binocular vision, all of which determine the type of management chosen.
Though non-surgical management includes miotics, prisms, botulinum toxin and contact lenses, the most effective option is single-vision lenses and bifocals, he said. Orthoptic exercises are a useful adjuvant. He also said that it was important to fully correct hypermetropia, as even one dioptre of undercorrection could increase the angle of deviation, more so in cases of high AC:A ratio.
In case of bifocals, the minimum reading correction should be started with (about +1D) and then increased by 0.50D, so that binocular single vision is maintained and the print is seen clearly. A binocular visual acuity test is used to assess control and to see if extra add is required.
He summed up by saying that bifocals had advantages of being effective in decreasing the angle of deviation, giving fusion while being inexpensive, non-invasive and readily available. He said that if well controlled and tolerated, they could be gradually reduced and stopped, and if poorly tolerated or controlled or in case of recurrence of esotropia after gradual reduction of bifocals, the option of surgical treatment could be exercised next without any negative effect.
Dr Newsham argued that with success rates of about 70% in surgical group and 66% with bifocals, a non-surgical option made sense as the first option.
Dr Mustafa Mehyar, a consultant paediatric ophthalmologist from Amman, Jordan, on the other hand, preferred surgical treatment, stating that less than half of patients with convergence excess esotropia would respond to additional plus lenses in clinic so as to qualify for bifocals. He also argued that if long-term failure rate from optical treatment was high, there was no reason to subject the patients to difficulties for years.
He quoted a 10-year study where only 61% could be weaned off glasses after five years, and further, surgical correction of deteriorated accommodative esotropia was needed in 50% of those weaned off glasses and one-third of those who continued to wear glasses.
Several studies of surgical correction of convergence excess esotropia show a success rate of motor alignment with one operation of approximately 70-95%. Nearly half were able to eliminate glasses completely.
Disadvantages of optical correction included difficulty in getting the segment to bisect the pupil, difficulty in adjusting to the bifocal segment; having to assume a chin-up position for near work, blurring in downgaze; possibility of reduced near point of accommodation, cosmetic issues, especially with executive lenses, unsatisfactory correction for intermediate and very close distances, disruptions to emmetropisation etc. All of these factors may reduce the time glasses are used during the day and hence cause other visual problems.
Dr Mehyar admitted that in younger children, when it is difficult to take accurate measurements, glasses could be used if it was understood that at one point surgery would be needed to treat the condition.
David Newsham: D.Newsham@liverpool.ac.uk; Mustafa Mehyar: email@example.com