Strabismus update

Three-year observation of children, aged three to 10 with untreated intermittent exotropia

Pediatric Eye Disease Investigator Group, Cotter SA et al.

Ophthalmology 2019;126(9):1249-60

 

Design: This study analysed the observational arm of a randomised trial of short-term occlusion versus observation of children with previously untreated intermittent exotropia. Included patients had an exotropia of 15 prism diopters (PD), that was intermittent or constant at distance and intermittent or phoric at near, and near stereoacuity of at least 400 seconds of arc. Deterioration was defined as a constant exotropia of 10PD at near and distance, near stereoacuity deterioration of 2 octaves or commencing treatment without having met the study criteria for deterioration.

 

Outcome: Three-year outcomes were available in 146 of 183 participants. Cumulative probability of deterioration at three years was 15% of which 12 had started treatment without having met the criteria for deterioration. Two had motor deterioration and 11 had stereoacuity deterioration during the study but not all received treatment. At three years, outcome data for 132 untreated children demonstrated only one to have deteriorated and an overall small improvement in stereoacuity (p<0.001), distance exotropia control (p<0.001) and distance angle (p=0.002).

 

Limitation: 20% of patients were lost to follow-up and could represent deteriorations that had sought treatment outside of the study.

 

Significance: This study provides comprehensive, prospective natural history data. Deterioration was uncommon with stability or even improvement demonstrated. This provides useful information when counselling parents on prognosis and management options.

 

Incidence of strabismus and amblyopia among children initially diagnosed with pseudostrabismus using the Optum data set

Ryu WY, Lambert SR.

Am J Ophthlalmol 2020;211:98-104

 

Design: This was a population-based, retrospective, cohort study of 17,885 children aged three years or less, diagnosed with pseudostrabismus between 2003 and 2013 and later diagnosed with strabismus. This group was compared to a control group of strabismic patients without prior pseudostrabismus diagnosis.

 

Outcome: Children presented with pseudostrabismus at a median age of 1.65 years. Subsequent strabismus was diagnosed in 9.6% (median age 3.32 years) compared with 1.7% (p<0.001) of children in the control group (median age 2.28 years).

Surgical correction was performed in 21.9% of patients in the pseudostrabismus group compared with 12.1% of children in the control group (p<0.001). In the pseudostrabismus group, 48.3% developed refractive error with hypermetropia most common.

 

Limitation: This study is retrospective and at high risk of selection bias. Patients with pseudostrabismus may have conflicting factors, such as family history, that prompted initial presentation. The data was sourced from a large claims database and so limited by potential miscoding and data quality.

 

Significance: Some children with pseudostrabismus may have undiagnosed intermittent strabismus at initial presentation. Increased surgical rates may represent the later age of presentation and missed opportunity to correct accommodative esotropia with glasses. Despite the limits of the study design, the data is useful in suggesting continued monitoring of these patients.

 

Otago glaucoma surgery outcome study: examining the development of strabismus causing diplopia in patients who have received Molteno implant surgery

Borowsky T, Bevin TH, Thompson AM et al.

J Binocul Vis Ocul Motil 2020; online ahead of print

 

Design: This was a retrospective, consecutive study of all cases undergoing Molteno implant surgery at Dunedin Hospital over a 32-year period. Cases were identified from a database and excluded if they had pre-existing strabismus, monocular diplopia, scleral buckle or transient diplopia of less than one-week duration.

 

Outcome: Of 977 cases undergoing Molteno surgery, 32 cases (3.3%) developed post-operative diplopia at a median of 2.78 months lasting for a median of 3.22 months. Type of strabismic deviation was hypertropic and/or exotropic in 18 of 23 cases in whom information was available. Evidence of restrictive strabismus was present in 11 of 25 cases both for up and downgaze. Spontaneous resolution occurred in 20 cases, five required prism correction, one used optical blurring to manage diplopia and four had persistent diplopia without specific treatment recorded. Two underwent strabismus surgery without resolution of symptoms.

 

Limitation: Absolute numbers of cases were too small to determine associations with quadrant positioning of tube. Retrospective analysis of a database will have missed capturing all affected patients and, by relying on previous records, led to incomplete data.

 

Significance: This study provides useful data for consent that diplopia after Molteno surgery occurs in 3.3% and persists in 1.2% of cases.

 

Dr Sarah Hull is the current paediatric and strabismus fellow at the University of Auckland, working at Greenlane Clinical Centre and Starship Hospital. Her medical training was in London where she completed a PhD in paediatric retinal genetics.

 

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