[Purpose] To evaluate the usefulness of a newly developed red filter ladder ( "the Yamamoto's filters" ; Yamamoto Kogaku Co., Ltd., Osaka, Japan) in measuring phoria maintenance ability, we used the Yamamoto's filters and the existing Bagolini's red filter bar ( "the SBISA's filters" ; SBISA INDUSTRIALE SPA, Firenze, Italy) to assess patients' abilities to maintain phoria and compared the performance of the two series of filters.

[Subjects and Methods] Inclusion criteria for subjects were: age 3 to 15 years, best corrected visual acuity of ≤ 1.0 in both eyes, diagnosed as intermittent exotropia [X(T)], and maintained phoria at near (30 cm) and far (5 m) distances. Exclusion criteria were dissociated vertical deviation, unable to respond to subjective examinations, and ocular diseases except X(T). We enrolled 31 subjects (14 boys and 17 girls) aged from 5 to 15 years (mean ± standard deviation, 10.5 ± 2.7 years). With refraction correction, the subject was instructed to fixate on a small light source and a red filter ladder was placed in front of the non-dominant eye. Starting with filter No. 1 with the highest luminous transmittance rate, the filter strength was increased up to filter No. 17 with the lowest luminous transmittance rate. As the load on the eye was increased, the red filter number immediately before the eye changed to tropia was determined as the patient's phoria maintenance ability. The tests by the Yamamoto's and SBISA's filters were performed in a random order and a 10-minute recess was given. The performance of both filter series was compared using the luminous transmittance rate as an indicator of the phoria maintenance ability.

[Results] Within the range where the two series of filters had the same luminous transmittance rate, no significant difference in the measured phoria maintenance ability was observed between the Yamamoto's and SBISA's filters (Wilcoxon signed-rank test, Near, p = 0.14; Far, p = 0.37).

[Conclusion] The Yamamoto's red filter ladder is as useful as the SBISA's filters in quantifying phoria maintenance ability.

The accuracies of four intraocular lens power calculation formulas, SRK/T, Haigis, Holladay I, and Hoffer Q, were ascertained for long axial length eye measurement during perioperative stages. The axial length, keratometric data, and anterior chamber depth were measured using an IOL Master^TM, and the refractive errors of each formula were compared in consecutive cases in eyes with an axial length greater than 26.0 mm. The refractive errors in the early postoperative period obtained using SRK/T, Haigis, Holladay I, and Hoffer Q were +0.32±0.58 D, +0.42±0.60 D, +0.83±0.63 D, and +0.89±0.63 D, respectively. These results suggested that the SRK/T or Haigis formulas should be used for intraocular lens power calculation in eyes with a long axial length.