The role of preoperative biometry in selecting initial contact lens power in the Infant Aphakia Treatment Study

• Authors: Rupal H. Trivedi, Medical University of South Carolina; Scott Lambert, Emory University; Michael Lynn, Emory University; M. Edward Wilson, Medical University of South Carolina
• Journal Title: Journal of AAPOS
• Volume: Volume 18, Number 3
• Publisher: Elsevier | 2014-06-01, Pages 251-254
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1016/j.jaapos.2014.01.012
• Subjects: Health Sciences, Opthamology; Health Sciences, Medicine and Surgery; Biology, Biostatistics
• Keywords: Science & Technology; Life Sciences & Biomedicine; Ophthalmology; Pediatrics

Abstract

Purpose: To investigate the role of preoperative biometry for selecting initial contact lens power. Methods: Patients randomized to receive contact lenses in the Infant Aphakia Treatment Study (IATS) were retrospectively analyzed. Inclusion criteria were availability of both a preoperative immersion axial length measurement and a 1-month postoperative refractive value. The target contact lens power for distance was determined using 1-month postoperative spherical equivalent refraction (after adjusting for a vertex distance) over the known contact lens power. We compared targeted contact lens power for distance with three other treatment techniques: (1) 30 D contact lens (32 D minus 2 D overcorrection for near vision based on IATS protocol); (2) regression-estimated contact lens power of 84.4 - 3.2 × axial length; and (3) IOL power calculated using the Sanders-Retzlaff-Kraff (SRK/T) regression formula with a modified A-constant (112.176). Prediction error (targeted minus estimated contact lens power) and its absolute values were calculated. Results: A total of 34 eyes of 34 patients met inclusion criteria. Age at the time of cataract surgery was 2.4 ± 1.7 months. Follow-up refraction was performed at 31 ± 3 days after surgery. Target contact lens power for distance was 26.0 ± 4.5 D for the IATS cohort (which excluded infants with corneal diameter <9 mm). The mean prediction error was -4.0, -1.0, and -2.0 D and mean absolute prediction error was 4.4, 2.2, and 2.9 D, respectively, for 30 D contact lens, regression, and SRK/T-estimated power. Conclusions: Preoperative biometry can be used to estimate contact lens power for distance if an accurate refraction cannot be obtained initially.