Correlation Between Axial Length and Anterior Chamber Depth in Normal Eyes, Long Eyes, and Extremely Long Eyes

Clinical Accuracy of 6 Intraocular Lens Power Calculation Formulas in Elongated Eyes, According to Anterior Chamber Depth

PURPOSE

To investigate the influence of anterior chamber depth (ACD) on the accuracy of the Kane, EVO 2.0, Barrett Universal II (BU II), Olsen, SRK/T, and Haigis formulas in patients with elongated eyes.

DESIGN

Retrospective case series study.

METHODS

A total of 106 patients (106 eyes) diagnosed with high myopia (axial length ≥26 mm) were enrolled and divided into 3 subgroups according to preoperative ACD. Mean refractive error (ME), mean absolute refractive error (MAE), median absolute refractive error (MedAE), and proportions of eyes within ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were calculated.

RESULTS

In all patients, the MedAE was lowest for the Kane formula (0.28 D), followed by the BU II (0.34 D). In the shallow ACD subgroup, EVO 2.0 formula produced the lowest MedAE (0.22 D), and the highest proportion of eyes within ±0.25 D (58%); the BU II (0.23 D, 50%) and Kane (0.25 D, 50%) formulas produced similar proportions. In the deep ACD group, the MedAEs of the Haigis and SRK/T formulas (0.68 D and 0.50 D, respectively) were significantly higher than those of the EVO 2.0 (0.37 D), Kane (0.30 D), BU II (0.43 D), and Olsen (0.34 D) formulas (P < 0.05).

CONCLUSIONS

Overall, the Kane and EVO 2.0 formulas had the highest accuracy. EVO 2.0 and BU II formulas are recommended for patients with shallow ACD; the Kane formula is recommended for patients with deep ACD (especially patients with extremely elongated eyes). The SRK/T and Haigis formulas should be avoided as much as possible.

Association of refraction and ocular biometry in highly myopic eyes

Clinical relevance: Ocular biometry is key to understanding the determinants of ocular development and pathology changes, especially for the thriving myopic population in Asia. Investigating biometric data in highly myopic eyes within a wide age spectrum is therefore of high importance.Background: To report the magnitude of change in spherical equivalent for each unit of change in the ocular biometry parameters in a highly myopic population in China.Methods: Highly myopic patients aged 7 to 70 years were recruited from the Zhongshan Ophthalmic Center, China. Each patient had a cycloplegic refraction and a measurement of ocular biometry.Results: Data from 823 right eyes were available for analysis, with a mean age of 22.7 years and a median spherical equivalent of -8.88 D. Axial length and lens thickness increased with age, while anterior chamber depth (ACD) decreased in older subjects. There was a significant trend of increasing axial length, lens thickness, vitreous chamber depth (VCD) and decreasing ACD and calculated lens power over spherical equivalent quartiles (all p < 0.001). The univariate linear regression models showed that 1-D change in refraction equalled to a 0.33- to 0.34-mm increase of axial length, and a 0.32 to 0.33-mm increase of VCD in highly myopic eyes. Among the three components of axial length, lens thickness was associated with myopia shift in the groups of 7-18 years and 19-39 years (both p < 0.001), and VCD was significant in all groups (all p < 0.001), while ACD was not significant in any age group.Conclusion: The associations between refraction and axial length were consistent in children, young adults and the elderly with high myopia. Lens thickening with a higher degree of myopia appeared at a very early age, and vitreous chamber depth remained to be a prominent factor of refraction change in highly myopic eyes throughout seven to 70 years of age.

Effect of the ratio of axial length to keratometry on SRK/T intraocular lens power calculations for eyes with long axial lengths

This retrospective study explored the effect of the ratio of axial length (AL) to average keratometry (K) on intraocular lens power calculation in long eyes. The clinical records of eyes that had an AL of 26.0 mm or longer, and underwent cataract surgery with intraocular lens implantations, were reviewed. This study was approved by the institutional review board of Miyata Eye Hospital. Preoperative biometry data were obtained using optical low-coherence reflectometry. Prediction errors in the use of the SRK/T formulas were obtained from manifest refraction spherical equivalents one month postoperatively. Significant factors inducing prediction errors were examined using stepwise multiple regression analysis with descriptive factors of AL, K value, and their ratio (AL/K). Clinical records related to 49 long eyes of 49 patients, and 93 eyes of 93 patients with normal AL, were evaluated. Stepwise multiple regression analysis revealed that the AL/K was a significant factor increasing the prediction errors (P = 0.0003). With the regression equation, 98% of prediction errors with the use of the SRK/T formula were within ±1.00 D of differences. For our sample of 49 long eyes, the ratio of AL to K was a significant factor inducing hyperopic prediction errors with the use of SRK/T for long eyes.

Comparison of the trabecular meshwork length between open and closed angle with evaluation of the scleral spur location

This study analysed the trabecular meshwork (TM) length in open and closed angle patients and presented a better method for locating the scleral spur using Schwalbe’s line method in anterior segment optical coherence tomography (AS-OCT). Patients who underwent AS-OCT at Yonsei University Gangnam Severance Hospital we enrolled; 58 and 57 open and closed angle eyes, respectively. We measured the distance from the scleral spur to Schwalbe’s line as the TM length and compared it between open and closed angle patients, and to previous studies. TM length was applied to locate the scleral spur using Schwalbe’s line method. Mean TM lengths were 811 ± 83 μm and 575 ± 96 μm in the open and closed angle groups, respectively (p < 0.001). Comparing the actual TM heights using Schwalbe’s line method with an updated reference distance significantly increased accuracy to locate the scleral spur (open: 811 μm, closed: 575 μm) when compared with the 1000 μm reference distance (p < 0.001). TM length was significantly different between open and closed angle patients. Further, the reference distance for Schwalbe’s line method should be distinguished according to open and closed angle eyes in order that the scleral spur can be located properly.

Effect of anterior chamber depth on the choice of intraocular lens calculation formula

Purpose

To investigate the effect of anterior chamber depth (ACD) on the refractive outcomes of the SRK/T, Holladay 1, Hoffer Q and Haigis formulae in short, normal, long and extremely long eyes.

Methods

This retrospective study involved patients who had uncomplicated cataract surgery. Preoperative axial length (AL) was divided into four subgroups: short (< 22.00 mm), normal (22.00–24.49 mm), long (24.50–25.99 mm), extremely long (≥ 26.00 mm). Preoperative ACD was divided into three subgroups: < 2.5, 2.50–3.49, and ≥ 3.5 mm. Median absolute errors (MedAEs) predicted by the SRK/T, Holladay 1, Hoffer Q and Haigis formulae were compared with the Friedman test. Post-hoc analysis involved the Wilcoxon signed rank test with a Bonferroni adjustment. Correlations between ACD and the predictive refractive errors of the four formulas were analyzed.

Results

In short eyes with an ACD < 2.5 mm, the Haigis formula revealed the highest MedAE. The difference in MedAE with the Hoffer Q formula (which had the lowest MedAE) was statistically significant (P = 0.002). In normal eyes, the Haigis formula significantly differed from the Holladay 1 (P = 0.002) and Hoffer Q (P = 0.005) formulae in the ACD < 2.5 mm group. In long eyes and extremely long eyes with an ACD ≥ 3.5 mm, the differences in MedAEs were statistically significant (P = 0.018, P = 0.001, respectively) and the Haigis formula had the lowest MedAEs in both subgroups (0.29 D, 0.30 D, respectively). In the total of 1,123 eyes, refractive errors predicted by the Haigis formula showed a significant negative correlation with the ACD (R² = 0.002, P = 0.047).

Conclusions

The Hoffer Q formula is preferred over other formulae in short eyes with an ACD shallower than 2.5 mm. In short and normal eyes with an ACD < 2.5 mm the Haigis formula might underestimate ELP. The Haigis formula is the preferred choice in eyes with an AL ≥ 24.5 mm and an ACD ≥ 3.5 mm.

Comparison of early changes in and factors affecting vault following posterior chamber phakic Implantable Collamer Lens implantation without and with a central hole (ICL V4 and ICL V4c)

Background

To objectively compare the early changes in vault over time following implantation of an Implantable Collamer Lens without (ICL V4) and with (ICL V4c) a central hole and the respective factors affecting vault change in moderate to high myopia.

Methods

This prospective study comprised of 38 eyes of 38 patients implanted with ICL V4 and 39 eyes of 39 patients implanted with ICL V4c intraocular lenses. We quantitatively assessed the postoperative values of vault and pupil size at 1 day, 1 week, and 1 month following implantation using a rotating Scheimpflug camera (Pentacam). We compared these postoperative values within and between the two groups and identified the factors affecting vault change.

Results

The mean vaults at 1 day, 1 week, and 1 month following ICL V4 implantation were 303.68 ± 185.11, 517.89 ± 160.07 and 521.32 ± 155.72 μm respectively, and those following ICL V4c were 316.67 ± 186.89, 495.13 ± 180.84 and 510.77 ± 175.51 μm, respectively. There was a significant difference in vault between 1 day and 1 week postoperatively. There was a significant association between the vault change and the pupil size change in both groups from 1 day to 1 month postoperatively (Pearman correlation coefficient; ICL V4: r = 0.585, P = 0.001; ICL V4c: r = 0.588, P <0.001). The vault value 1 month after implantation of ICL V4 and ICL V4c was associated with the preoperative anterior chamber depth, horizontal corneal diameter, horizontal and vertical sulcus-to-sulcus.

Conclusions

Pupil movement is a critical factor in vault change, with increasing vault observed postoperatively from 1 day to 1 week associated with the declining effects of pharmacological miosis and increasing pupil size. The anterior chamber depth, horizontal corneal diameter, horizontal and vertical sulcus-to-sulcus show some correlation with vault.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-016-0336-8) contains supplementary material, which is available to authorized users.