Axial Length Change in Pseudophakic Eyes Measured by IOLMaster 700

Comparative analysis of axial length measurement method for eyes with submacular hemorrhage

PURPOSE

To identify a method for comparing preoperative axial length (AL) measurements with postoperative AL in submacular hemorrhage (SMH).

STUDY DESIGN

Retrospective.

METHODS

This study included 30 patients who underwent vitrectomy for SMH (January 2016-January 2023) with preoperative and postoperative AL data. Preoperative AL was obtained using ultrasonography for the affected eye (aUS-AL) and compared to those measured using optical biometry (OB) for the affected and fellow eyes (aOB-AL and fOB-AL, respectively). Postoperative AL (aPost-AL) was defined as the AL of the affected eye by OB. The absolute differences between the preoperative AL (aUS-AL, aOB-AL, and fOB-AL) and aPost-AL were assessed.

RESULTS

aUS-AL, aOB-AL, and fOB-AL values were 23.50 ± 1.41 mm, 23.32 ± 1.40 mm, and 23.66 ± 1.45 mm, respectively, correlating strongly with aPost-AL (23.54 ± 1.37 mm) (all R > 0.95). fOB-AL exceeded aPost-AL significantly (P = 0.02). In all 30 eyes, absolute differences between preoperative AL and aPost-AL were 0.19 ± 0.18 mm, 0.28 ± 0.32 mm, and 0.21 ± 0.22 mm, respectively, which were not significantly different from each other (all P > 0.05). In nine eyes with SMH height > 1000 μm or unmeasurable, the absolute difference between aOB-AL and aPost-AL (0.42 ± 0.33 mm) exceeded that of aUS-AL and aPost-AL (0.10 ± 0.09 mm) (P = 0.003).

CONCLUSION

Although aUS-AL, aOB-AL, and fOB-AL correlated well with postoperative AL in patients with SMH, fOB-AL may be measured longer and aOB-AL shorter in some cases. Therefore, aUS-AL may be considered primarily in determining IOL power of cataract surgery performed in combination with SMH displacement.

Accuracy of ultrasound vs. Fourier-domain optic biometry for measuring preoperative axial length in cases of rhegmatogenous retinal detachment

PURPOSE

To identify a method for accurately measuring preoperative axial length (AL) in cases of rhegmatogenous retinal detachment (RRD).

STUDY DESIGN

Retrospective study.

METHODS

This retrospective study included 83 eyes of 83 patients who underwent vitrectomy for RRD and had both preoperative and postoperative data for AL. Preoperative AL measurements for the affected eye were obtained using ultrasound (aUS-AL) and compared with those for affected and fellow eyes measured using optical biometry (aOB-AL and fOB-AL, respectively). Absolute differences between preoperative aUS-AL, aOB-AL, or fOB-AL measurements and postoperative AL (aPost-AL) were examined.

RESULTS

In the 41 eyes without macular detachment, the absolute difference between aOB-AL and aPost-AL (0.06±0.07 mm) was significantly smaller than between aUS-AL and aPost-AL (0.21±0.18 mm) and that between fOB-AL and aPost-AL (0.29±0.35 mm) (P = 0.017 and P < 0.001, respectively). In the 42 eyes with macular detachment, the absolute difference between aOB-AL and aPost-AL (1.22±2.40 mm) was significantly larger than between aUS-AL and aPost-AL (0.24±0.24 mm) and between fOB-AL and aPost-AL (0.35±0.49 mm) (P = 0.006, P = 0.016, respectively).

CONCLUSION

The current findings suggest that aOB-AL is more accurate than aUS-AL or fOB-AL in cases of RRD without macular detachment, while aUS-AL or fOB-AL is more accurate than aOB-AL in cases with macular detachment.

Refractive outcomes after immediate primary phacoemulsification for acute primary angle closure

This study investigated the refractive outcomes of 64 eyes overall including 32 immediate primary phacoemulsification in acute primary angle closure (APAC) eyes and 32 of their fellow eyes. We investigated best-corrected visual acuity, intraocular pressure (IOP), average keratometric diopter (K), spherical equivalent, axial length (AL), central corneal thickness, and anterior chamber depth (ACD) at preoperative examination (Pre) and more than 1-month post-phacoemulsification (1 m), and changes in values. Using SRK/T, Barrett Universal II (Barrett), Hill-Radial Basis Function Version 3.0 (RBF 3.0), and Kane formulas, we calculated and compared refractive prediction error (PE), absolute value of PE (AE), and changes in K, AL, and ACD from Pre to 1 m between APAC and fellow eyes. From Pre to 1 m, K remained similar in APAC and fellow eyes (p = 0.069 and p = 0.082); AL significantly decreased in APAC and in fellow eyes (both p < 0.001); and ACD significantly increased in APAC and in fellow eyes (both p < 0.001). The change in AL differed significantly between the two groups (p = 0.007). Compared to the fellow eyes, PE with SRK/T and Barret formulas (p = 0.0496 and p = 0.039) and AE with Barrett and RBF 3.0 formula (p = 0.001 and p = 0.024) were significantly larger in the APAC eyes. Thus, attention should be paid to refractive prediction error in immediate primary phacoemulsification for APAC eyes caused by preoperative AL elongation due to high IOP.

Dual study on the sum-of-segments method for axial length measurement: is it better?

PURPOSE

To evaluate the sum-of-segments (SOS) method for optical axial length (AL) measurements.

SETTING

Department of Ophthalmology, University of Aarhus, Denmark, and Private practice, Copenhagen, Denmark.

DESIGN

Retrospective observational study.

METHODS

2 retrospective datasets were included. The first dataset comprised 1491 university cataract cases measured with the LENSTAR LS900 preoperatively and 1 to 4 months postoperatively. The second dataset comprised 904 lens surgery cases with refractive follow-up to study the accuracy of intraocular lens power calculation. The prediction accuracy was evaluated as the difference between the observed and the expected refraction.

RESULTS

The mean difference between the preoperative and the postoperative AL readings was -0.06 mm and -0.020 mm for the standard and the SOS AL method, respectively, however with a larger variation for the SOS AL method ( P < .01). For the second dataset, the SOS method was found to increase the accuracy of the SRK/T and the Holladay formulas. With the Olsen formula, the SOS method was found to be worse ( P < .01). The highest accuracy was found using standard AL with the Olsen formula, with a mean absolute error of 0.24 diopter (D) and 89.8% of the cases within ±0.5 D.

CONCLUSIONS

The SOS method improved the accuracy of the classical formulas probably because the optical path is a better representative of the true AL. The Olsen formula already incorporates an optical path correction, and this may be the reason for the lack of improvement with the SOS method.

A formula to improve the reliability of optical axial length measurement in IOL power calculation

To verify the influence of axial length (AL) variations after cataract surgery in IOL power calculation. Patients underwent ophthalmic evaluation before surgery, including optical biometry with IOLMaster 500. Same exams were repeated 2 months after surgery: AL of operated eye was evaluated using two modes (pseudophakic/aphakic options). Mean Keratometry and AL changes were analyzed. Furthermore, refractive prediction error (PE) was back-calculated with Barrett Universal-II, Hoffer-Q, Holladay-1 and SRK/T formulas. To eliminate any systematic error, the mean error (ME) was zeroed-out for each formula. MEs and median absolute errors (MedAEs) of PEs were analyzed. Two-hundred-one operated eyes of 201 patients and 201 opposite eyes were evaluated. In operated eyes, mean AL difference was - 0.11 ± 0.07 mm (p < 0.001) with pseudophakic option and 0.00 ± 0.07 mm (p = 0.922) with aphakic option. There were not-statistically significant differences between MedAE of PEs calculated after zeroing-out the ME with different ALs (p > 0.05). Instead, only MEs of PEs obtained with postoperative ALs-pseudophakic option were not-statistically different from zero (p > 0.05). AL measurement change after cataract surgery is probably due to a systematic error in optical biometer in case of phakic eyes. A correction factor applied to preoperative AL could eliminate any systematic error in IOL power calculation without modifying the lens constant.