Partial coherence laser interferometry vs conventional ultrasound biometry in intraocular lens power calculations

Axial length adjustment in eyes with silicone oil endotamponade reduces overestimation by a swept-source optical coherence tomography-based biometer

BACKGROUND

To assess changes in ocular biometry of the phakic eye after pars-plana-vitrectomy (PPV) and silicone oil (SO) endotamponade in eyes with a retinal detachment.

METHODS

This retrospective, consecutive case series included 72 eyes of 72 patients who underwent PPV with 5000-centistokes SO endotamponade between July 2018 and June 2023. Pseudophakic eyes and eyes with a combined phacovitrectomy were excluded. Primary endpoints were keratometry values, anterior chamber depth (ACD), lens thickness (LT), horizontal corneal diameter (HCD), and axial length (AL) measured by swept-source optical coherence tomography-based biometry (IOLMaster 700) preoperatively and six weeks postoperatively. A recently described formula was used to adjust the AL (aAL) in eyes with SO endotamponade and a theoretical intraocular lens (IOL) calculation was performed.

RESULTS

The mean age was 62.1 ± 8.3 years (range: 37-85). After PPV with SO fill, there was an increase in Kmean (0.19 ± 0.51D), while ACD (0.05 ± 0.13 mm), LT (0.03 ± 0.14 mm), and HCD (0.02 ± 0.24 mm) decreased. Preoperatively, the mean AL was 25.22 ± 1.78 mm, while postoperatively the AL was overestimated by 0.12 ± 0.42 mm on average (p = 0.04). By adjusting the AL, the mean difference could be reduced to -0.002 ± 0.41 mm. The aAL resulted in a difference in the refractive outcome in eyes with an AL > 25 mm of 0.34 ± 0.10D in the IOL calculation.

CONCLUSIONS

While changes in biometry after PPV with SO endotamponade in the anterior segment are clinically less relevant, a considerable overestimation of AL with IOLMaster 700 was found. We recommend the use of a recently introduced formula for adjusting AL in eyes with SO, allowing overestimation to be minimised considerably.

Efficacy of cataract surgeries performed during blindness prevention programs in Chongqing, China: a multicenter prospective study

OBJECTIVE

To determine the efficacy of cataract surgeries in blindness prevention programs in Chongqing.

METHODS

During February-December 2019, we prospectively enrolled 487 patients (592 eyes) undergoing cataract surgery during blindness prevention programs in 6 Chongqing district/county hospitals (experimental group) and 481 patients (609 eyes) undergoing cataract surgery in the First Affiliated Hospital of Chongqing Medical University (controls). Uncorrected visual acuity (UCVA), refractive status, best corrected visual acuity (BCVA), slit lamp examination, and visual function/quality of life (VF-QOL) questionnaire scores were evaluated preoperatively, and at 1 and 6 months postoperatively.

RESULTS

In the experimental group, UCVA, BCVA, and VF-QOL scores at 1 and 6 months were better than the preoperative values (P < 0.05), but lower than the control-group values (P < 0.05). Rates of good UCVA and BCVA outcomes (≤ 0.5 logMAR) in the experimental group were 76.2% and 87.6%, respectively, at 1 month and 68.9% and 83.1%, respectively, at 6 months. Most eyes in the experimental (82.1%) and control (89.5%) groups had refractive errors within ± 1 D at 1 month. At 6 months, posterior capsule opacification (PCO) was more common in the experimental group (20.9% vs. 15.0%, P < 0.05). At 6 months, the main causes of visual impairment (UCVA > 0.5 logMAR) in the experimental group were uncorrected refractive errors (33.0%), PCO (29.5%), and fundus diseases (33.9%).

CONCLUSION

Cataract surgeries in blindness prevention programs in Chongqing significantly improved visual acuity, VF, and QOL, but underperformed compared to surgeries in the tertiary teaching hospital.

Evaluation of Ocular Biometric Parameters Following Cataract Surgery

Background: The aim of this study was to highlight the structural changes in patients with cataract following surgery and the repercussions on the anterior pole. Methods: A total of 83 patients diagnosed with cataract who underwent uneventful phacoemulsification was included. Every patient was examined one week prior to and two weeks after the surgery. Pre- and postoperative assessment included examination of the anterior and posterior segment, keratometry, and optical biometry. Results: The pre- vs. postoperative axial length (AL) mean difference was 0.07 ± 0.18 mm (p < 0.001).The mean difference of the postoperative anterior chamber depth (ACD) vs. preoperative ACD values (1.11 ± 0.50 mm) was also statistically significant (p < 0.001). The linear regression function postoperative central corneal thickness (CCT) = 0.9004 × (preoperative CCT) + 0.0668, where it characterized a reduced positive correlation (R2) of 68.89% between the postoperative CCT and preoperative CCT. The mean pre-/post-operative differences in the K1 values were 0.08 ± 0.38 D, with a statistically significant difference between the two datasets (p = 0.0152). The mean pre/postoperative difference in the K2 values was 0.002 ± 0.58 D (p = 0.4854). Conclusions: ACD deepened significantly postoperatively. Regarding AL, there was a decrease after surgery, and a very good positive correlation between the post and preoperative values. The CCT values decreased with age. The 2.2-mm corneal incision during cataract surgery resulted in a relatively small postoperative residual astigmatism.

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.

Comparison of visual outcomes of a diffractive trifocal intraocular lens and a refractive bifocal intraocular lens in eyes with axial myopia: a prospective cohort study

Background

To assess and compare the efficacy, safety, accuracy, predictability and visual quality of a diffractive trifocal intraocular lens (IOL) and a refractive rotationally asymmetric bifocal IOL in eyes with axial myopia.

Methods

This prospective cohort study enrolled patients with implantation of the diffractive trifocal IOL or the refractive bifocal IOL. Eyes were divided into four groups according to the IOL implanted and axial length. Manifest refraction, uncorrected and corrected visual acuity at far, intermediate and near distances, prediction error of spherical equivalent (SE), contrast sensitivity and aberrations were evaluated three months after surgery.

Results

In total, 80 eyes of 80 patients were included: 20 eyes in each group. Three months postoperatively, the corrected distance visual acuity of two trifocal groups were significantly better than the axial myopia bifocal group (P = 0.007 and 0.043). There was no significant difference of postoperative SE (P = 0.478), but the SE predictability of the trifocal IOL was better, whether in axial myopia groups (P = 0.015) or in control groups (P = 0.027). The contrast sensitivity was similar among four groups. The total aberration, higher order aberration and trefoil aberration of bifocal groups were significantly higher (all P < 0.001).

Conclusions

The diffractive trifocal IOL and the refractive bifocal IOL both provided good efficacy, accuracy, predictability and safety for eyes with axial myopia. By contrast, the trifocal IOL had a better performance in corrected distance visual acuity and visual quality.

Trial registration

The study was retrospectively registered and posted on clinicaltrials.gov at 12/02/2020 (NCT04265846).

Assessment of the Refractive Error and Stabilisation of Refraction after Cataract Surgery in Relation to the Length of the Eyeball

The aim of this study was to analyse the changes in refraction, depending on the length of the eyeball, in patients who had undergone cataract surgery using the phacoemulsification method and to assess the stability of refraction. A total of 90 patients (46 to 85 years of age) took part in the study and were divided into three groups: emmetropic, hypermetropic, and myopic. Two types of intraocular lenses were used: Bausch (Akreos AO) and Rayner (C-flex). In conclusion, stabilization of refraction was achieved in the third week in 91% of the emmetropic, 77% of the myopic, and 46% of the hypermetropic patients, respectively. The correct postoperative refraction was achieved using optical biometry and the Barrett Universal II formula to calculate the power of the lens implant.

Outcomes of combined phacoemulsification/intraocular lens implantation and silicon oil removal

PURPOSE

To evaluate the outcomes and complications of simultaneous silicon oil removal (SOR) and phacoemulsification and intra ocular lens implantation.

METHODS

In this retrospective non-comparative case series, the visual, refractive and anatomical outcomes of patients who underwent combined phacoemulsification/silicone oil removal (5700 centistokes) surgery between 2017 and 2019 in a single center were evaluated.

RESULTS

Forty-four eyes of 44 patients (eighteen males) were included. The mean age of the patients was 51.45 ± 11.59 years. The primary pathology was tractional retinal detachment (TRD) secondary to diabetic retinopathy in 36 eyes and rhegmatogenous retinal detachment (RRD) in 8 eyes. The median time period between silicone oil tamponade and removal was 9 months. There was no statistically significant difference between best corrected visual acuity (-0.14 ± 0.69 LogMAR, p= 0.19) and intraocular pressure (p= 0.26) before and after the surgery. Mean post-operative spherical equivalent (SE) at last visit was 0.36 ± 1.64 which was different from the target refraction (- 0.5D). After cataract/SOR surgery, one eye (2.3%) developed retinal re-detachment in RRD patient. Vitreous hemorrhage occurred in nine eyes (20.5%) which all had TRD as the primary pathology.

CONCLUSION

Combined phacoemulsification, silicone oil and IOL implantation removal surgery seems to be a safe and useful procedure with high success rate and acceptable visual, refractive and anatomical outcomes.

COMPARISON OF OPTICAL BIOMETERS ARGOS AND IOL MASTER 700

PURPOSE

To compare the biometric data obtained by the new optical biometer Argos and the conventionally used biometer IOL Master 700.

PATIENTS AND METHODS

Retrospective analysis of the biometric data of 57 patients (106 eyes) who were examined at TANA Ophthalmology Clinic s.r.o in Olomouc. Patient measurements were carried out on both devices on the same day by the same optometrist within the standard preoperative calculation of the intraocular lens before cataract surgery. Evaluated and statistically analyzed biometric data were axial lenght, anterior chamber depth, average keratometry and lens thickness.

RESULTS

The correlation between all compared data was high, with statistical significance p &lt; 0.01. Bland-Altman plots showed good agreement with a 95% limit of agreement. Axial lenght, average keratometry and lens thickens did not show significant differences (p = 0.941; p = 0.773; p = 0.860). IOL Master 700 showed flatter average keratometry, however, the differences were numerically small and insignificant. Anterior chamber depths obtained by Argos were longer, with a significance p &lt; 0.05.

CONCLUSION

The segmental refractive index technology used by Argos caused differences in anterior chamber depths. Overall axial length was, however, not, in our cohort of patients, affected by this. In general, the optical biometers Argos and IOL Master 700 show excellent agreement in the measured biometric data.

Refractive Outcomes after Cataract Surgery

A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients’ vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients’ vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small “error budget” (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients’ refractory status after cataract surgery.

Effect of Lens Vault on the Accuracy of Intraocular Lens Calculation Formulas in Shallow Anterior Chamber Eyes

PURPOSE

To explore the impact of preoperative lens vault (LV) on the accuracy of the Barrett Universal Ⅱ, Haigis, Hoffer Q, Hoffer QST, Holladay 1, Kane, and SRK/T formulas in eyes with a shallow anterior chamber.

DESIGN

Retrospective case series.

METHODS

Included were 409 eyes with anterior chamber depth (ACD) shallower than 3.0 mm that underwent phacoemulsification. Eyes were divided into a short axial length (AL) group (<22.00 mm) and a normal AL group (22.00 ≤ AL < 24.50 mm). Each group was further divided into a small LV subgroup (LV <0.95 mm) and a large LV subgroup (LV ≥0.95 mm) according to the median of the preoperative LV. Postoperative refraction was measured 3 months after surgery. Mean absolute error (MAE) was calculated and compared for each formula. The correlation between LV and the mean numeric error predicted by each formula was analyzed.

RESULTS

Overall, the Barrett and Kane formulas generated the smallest MAE in both short AL and normal AL groups (P < .05 for both). In short AL eyes with small LV, the Haigis formula performed better than other traditional formulas (P < .05 for all). In normal AL eyes with a small LV, the Barrett and Kane formulas showed higher accuracy (P < .05 for all), and other formulas were comparable. In either subgroup with a large LV, the Haigis formula created a significant higher MAE (P < .001 for all), followed by Hoffer QST. Positive correlations were found between LV and mean numeric errors predicted by all formulas, except for Barrett and Kane formulas (P < .001 for all), indicating a postoperative hyperopic shift with an increased LV.

CONCLUSIONS

In shallow anterior chamber eyes with a large LV, the Haigis and Hoffer QST formulas taking preoperative ACD into calculation surprisingly showed a larger prediction error. However, the Barrett and the Kane formulas, which include both ACD and lens thickness as predictive parameters, showed good accuracy in both small and large LV subgroups. Therefore, although formulas referring to preoperative ACD are generally believed to achieve better refractive results in patients with a shallow anterior chamber, LV may be valuable to consider when choosing an IOL power calculation formula.

Ocular biometry in dense cataracts: Comparison of partial-coherence interferometry, swept-source optical coherence tomography and immersion ultrasound

Purpose:

To assess the axial length (AL) measurement failure rate using partial-coherence interferometry (PCI) and swept-source optical coherence tomography (SS-OCT) in dense cataracts. As a secondary outcome, the SS-OCT biometry was compared to immersion ultrasound.

Methods:

This is a prospective cross-sectional and comparative study. Seventy eyes from 70 patients with dense cataracts were enrolled in this study. Dense cataract was defined according to the Lens Opacities Classification System III (LOCS III) scores equal to or more than NO4, NC4, C4, and P3. The failure rate of AL measurement was evaluated using PCI and SS-OCT. Anterior chamber depth (ACD), lens thickness (LT), and AL measurements obtained by SS-OCT were compared with IUS.

Results:

AL measurement failure rate with PCI was 68.57% and 21.43% with SS-OCT (P = 0.007). AL measurement was achieved in 69.23% of NO4, 66.6% of P3, and 15.3% of mixed cataracts using PCI, while SS-OCT was achieved in 100% of NO4, NO5, P3, and P5 and 76.9% of mixed cataracts. Cortical cataracts alone did not influence AL measurement. Biometric data of ACD, LT, and AL were statistically different comparing US and SS-OCT with a good correlation of AL.

Conclusion:

SS-OCT significantly improves the rate of successful AL measurements when compared to PCI in dense cataracts. The LOCS III clinical cut-off for the use of SS-OCT ocular biometry may well be up to P4 and NO5.

Scleral-fixated intraocular lens implants-evolution of surgical techniques and future developments

Varied options are available for the implantation of secondary intraocular lens implants in the absence of zonular or capsular support. Loss of the capsule can occur in the context of complicated cataract surgery, trauma or inherited conditions such as Marfan syndrome or pseudoexfoliation. Approaches to overcome this include optical measures such as the use of spectacles or contact lenses, and surgical therapy incorporating the use of anterior chamber, iris-fixated or scleral-fixated lenses. Surgical techniques to implant scleral-fixated lenses have undergone various modifications, since the first publication of sutured intrascleral fixation described in the 1980s. However, despite the advances in surgical techniques, studies are limited either by their retrospective nature, small sample size and most importantly small duration of follow-up. This comprehensive review aims to amalgamate the evolution of various surgical techniques with regards to intrascleral lens fixation and suggests areas for future development.

The measurement of ocular axial length in normal human eyes based on an improved Twyman-Green interferometer

In order to meet the demands of myopia prevention, as well as the increasing needs of measurement for refractive and cataract operations in China, a new axial length (AL) measurement system combining an improved Twyman-Green interferometer with digital signal processing has been established. The ALs of 33 eyes of different optical refractive subjects (-8.50 ~ 0.50 D) were measured with the New AL and intraocular lens (IOL) master. The repeatability of measurements with the New AL was assessed using coefficient of variation (CoV) and intra-group correlation coefficient (ICC). Comparison, correlation, linear regression and agreement of AL between devices were analyzed. There was good repeatability (CoV = 0.0617%, ICC = 0.9999) with the New AL and great agreement has been obtained with both devices. These show that the New AL is capable of providing precise AL values over the normal AL range compared to the IOL master, and indicate that the New AL developed can be used for routine clinical AL measurements.

Intraocular Lens Power Calculation According to the Difference between Anterior and Total Keratometry Using Scheimpflug Imaging

Purpose: We investigated the change in the absolute error according to the difference between anterior and total keratometry, to determine the criterion for the difference in keratometry, and to determine the indication for using total keratometry. Methods: Sagittal and total refractive power were measured with 2-, 3-, and 4-mm Pentacam^® rings, and the absolute error of each was calculated in patients who underwent cataract surgery in our hospital. The correlation between the difference value the sagittal minus the total refractive power and each absolute error was analyzed by simple regression analysis. The analysis was performed by dividing the patients into two groups based on 0.6, which is the average of the difference between the sagittal and total refractive power for the 3-mm ring. Results: Sagittal power was larger than total refractive power for all rings and the absolute error obtained by applying the total refractive power was larger than the sagittal power for the 2- and 4-mm rings (<i>p</i> < 0.001). The simple regression analysis revealed that the absolute error using sagittal power was positively correlated with the difference between sagittal power and total refractive power. In the group with less than 0.6, the absolute error using the total refractive power of all rings was larger than the sagittal power (<i>p</i> < 0.001). In the group exceeding 0.6, the absolute error using the total refractive power was less than using the sagittal power for the 3 mm ring (<i>p</i> = 0.028). Conclusions: The greater the difference between sagittal and total refractive power, the greater the absolute error using sagittal power. Accuracy was higher in the group exceeding 0.6 after applying total refractive power measured at the 3 mm ring compared to sagittal power.

Evaluation of intra-operative aphakic axial eye length measurements using swept source optical coherence tomography

PURPOSE

Evaluation of intra-operative aphakic axial eye length (AL) measurements using swept source optical coherence tomography.

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective single-center study.

METHODS

Patients scheduled for cataract surgery were measured using swept-source optical coherence tomography (ss-OCT, IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany) to assess the axial eye length. Intra-operatively, swept source optical coherence tomography (ss-OCT) measurements were performed with a prototype device (IOLMaster 700 connected to an OPMI Lumera 700 microscope, CZM) at the beginning of cataract surgery furthermore of the aphakic eye and 2 months after surgery.

RESULTS

Of the 59 eyes of 59 patients, the phakic median AL pre-operatively (pre-OP) and intra operatively (intra-OP) were 23.61 mm ± 0.96 (SD) and 23.51 mm ± 0.96 (SD). Absolute median difference was 0.028 ± 0.02 (SD) (p=0.049). Median phakic AL intra-OP versus 2 months post operatively (post-OP) was 23.51 mm ± 0.97 (SD) vs 23.49 mm ± 0.95 (SD). Absolute median difference was 0.049 ± 0.04 (SD) (p=0.000).Median AL intra-OP aphakic versus vs 2 months post-Op pseudophakic were 23.42 mm ± 0.97 (SD) versus 23.42 mm ± 0.97 (SD). Absolute median difference was 0.038 ± 0.04 (SD) (p=0.379).

CONCLUSIONS

Intra-OP swept source OCT technology of the phakic and aphakic eye shows excellent comparability to pre- and post-operative measurements. This technique allows axial eye length measurements with high precision in cases where pre-op biometric measurements are not possible.

POSITION OF IN-THE-BAG POSTERIOR CHAMBER INTRAOCULAR LENSES RELATIVE TO THE LIMBUS: Applications to Scleral-Sutured Lenses

PURPOSE

To characterize the true position of in-the-bag intraocular lenses (IOLs) relative to the limbus using ultrasound biomicroscopy and estimate scleral-sutured IOL positioning.

METHODS

This prospective single-center study included 70 eyes of 41 patients with in-the-bag posterior chamber IOLs. Four vertical ultrasound biomicroscopy captures were performed in each eye in the superior, inferior, nasal, and temporal quadrants. Postoperative biometric data were collected. The primary outcome was the vertical distance of the in-the-bag IOL from the sclerocorneal limbus. Secondary outcomes included anterior shift and refractive change of a theoretical scleral-sutured IOL using sclerotomies at 2.5 mm and 3 mm posterior to the limbus.

RESULTS

A total of 265 ultrasound biomicroscopy images were analyzed, including 64 superior, 69 inferior, 66 nasal, and 66 temporal. The true in-the-bag IOL position measured as distance posterior to the sclerocorneal limbus was 4.23 ± 0.56 mm superiorly, 4.22 ± 0.46 mm inferiorly, 3.95 ± 0.48 mm nasally, and 3.86 ± 0.52 mm temporally. The anterior shift of a theoretical scleral-sutured IOL was 0.60 mm for a 3-mm sclerotomy and 0.93 mm for a 2.5-mm sclerotomy, resulting in a theoretical myopic shift of 0.45 diopter (D) and 0.79 D, respectively, assuming a 15-D IOL. Larger biometric measurements correlated with a more posterior in-the-bag position.

CONCLUSION

True in-the-bag IOL position was found to be more posterior than estimates of scleral-sutured IOLs. Additional corrections in scleral-sutured IOL calculations may improve refractive outcomes.

Axial Length Change in Pseudophakic Eyes Measured by IOLMaster 700

Purpose

The purpose of this study was to investigate the change in axial length (AL) after cataract surgery measured by swept source optical coherence tomography (IOLMaster 700), and explore ways to eliminate this AL measurement error in pseudophakic eyes.

Methods

Patients with cataract who underwent unilateral phacoemulsification with four types of intraocular lens (IOLs) implantation (Asphina 509M, Tecnis PCB00, enVista MX60, and Acrysof SN60WF) were enrolled. Bilateral AL measurements were performed before and 1 month after cataract surgery utilizing IOLMaster 700. The postoperative AL of the operated eye was evaluated using three different modes (phakic, aphakic, and pseudophakic), and the fellow eye was measured by phakic mode. Associations among the AL change and cataract grade, lens thickness, preoperative AL, or refractive index of IOL were investigated using stepwise multivariate linear regression.

Results

A total of 305 patients with cataract with mean age of 65.97 ± 13.39 years were recruited. The mean postoperative AL was 0.10 mm and 0.21 mm shorter than the pre-operative AL utilizing pseudophakic and phakic modes, respectively (P < 0.001). No significant difference was observed between pre-operative and postoperative AL using aphakic mode (P = 0.264). There were no significant associations among AL change in pseudophakic eye and cataract grade, lens thickness, pre-operative AL, or refractive index of IOL (P > 0.05).

Conclusions

A correction factor of 0.10 mm is suggested to eliminate AL measurement error of IOLMaster 700 in pseudophakic eyes before further improvement of AL measurement accuracy.

Translational Relevance

Our study may help to eliminate the AL measurement error of IOLMaster 700 in pseudophakic eyes.

Relationship between Axial Length and Corneo-Scleral Topography: A Preliminary Study

The main objective of the current study was to investigate further the relationship of the overall length of the eye with a great variety of anterior segment parameters, including scleral geometry. A total of 64 eyes of 32 participants with ages from 12 to 52 years were included in this prospective non-randomized single-center study. All participants underwent a complete eye examination, including an analysis of corneo-scleral shape with a Fourier-domain profilometer. A strong negative correlation was found between axial length and temporal-nasal ocular sagittal height difference for different chord lengths. For the right eye, a consistent and stable linear model was obtained to predict the axial length from the spherical equivalent, the corneal diameter, the high-order aberrations root mean square, and the minimum sagittal height for 13- and 14-mm chord. For the left eye, a model was obtained to predict the axial length from the spherical equivalent and the mean corneal curvature, including other parameters such as corneal diameter or high-order aberrations, depending on the chord length, considered for estimating the sagittal height values. More studies with larger samples are needed to confirm these preliminary outcomes.

Refractive outcomes after vitrectomy combined with phacoemulsification of idiopathic macular holes

AIM

To report the refractive outcomes after vitrectomy combined with phacoemulsification and intraocular lens (IOL) implantation (phaco-vitrectomy) in idiopathic macular holes (IMH).

METHODS

A total of 56 eyes with IMH (IMH group) that underwent phaco-vitrectomy and 44 eyes with age-related cataract (ARC group) that underwent cataract surgery were retrospectively reviewed. The best corrective visual acuity (BCVA), predicted refractive error (PRE), actual refractive error (ARE), axial length (AL), were measured in both groups before and 6mo after operation. The power calculation of IOL and the predicted refractive error (PRE) were calculated according to the SRK/T formula. The difference of PRE and ARE between the two groups were compared and analyzed.

RESULTS

In the IMH group, the diameters of macular holes were 271.73±75.85 µm, the closure rate was 100%. The pre- and post-operative BCVA were 0.80±0.35 and 0.40±0.35 logMAR. The PRE of A-ultrasound and IOL Master in the IMH group was -0.27±0.25 and 0.10±0.66 D. The postoperative mean absolute prediction error (MAE) was observed to be 0.58±0.65 and 0.53±0.37 D in the IOL Master and A-ultrasound (P=0.758). The PRE and ARE of the IMH group were 0.10±0.66 D and -0.19±0.64 D (P=0.102). The PRE and ARE of the ARC group was -0.43±0.95 and -0.31±0.93 D (P=0.383). The difference between PRE and ARE was -0.33±0.81 and 0.09±0.64 D in the IMH and ARC groups (P=0.021). The proportion of myopic shift was 67.9% in the IMH group and 27.3% in the ARC group (P=0.004).

CONCLUSION

The myopic shift can be observed in patients with IMH after phaco-vitrectomy.

Accuracy of partial coherence interferometry in patients with large inter-eye axial length difference

Background

To determine accuracy of partial coherence interferometry (PCI) in patients with large inter-eye axial eye length (AEL) difference.

Methods

Patients undergoing cataract surgery at two academic medical centers with an inter-eye axial eye length (AEL) difference of > 0.30 mm were identified and were matched to control patients without inter-eye AEL difference > 0.30 mm on the basis of age, sex, and AEL. The expected post-operative refraction for the implanted IOL was calculated using SRK/T, Holladay II, and Hoffer Q formulae. The main outcome measures were the refractive prediction error and the equivalence of the refractive outcomes between the subjects and controls.

Results

Review of 2212 eyes from 1617 patients found 131 eyes of 93 patients which met inclusion criteria. These were matched to 131 control eyes of 115 patients. The mean AEL was 24.92 ± 1.50 mm. The mean absolute error (MAE) ranged from 0.47 D to 0.69 D, and was not statistically different between subjects and controls. The refractive prediction error was equivalent between the cases and controls, with no significant difference between the MAE for any formula, nor in the number of cases vs. controls with a refractive prediction error of at least 0.50 D or 1.00 D.

Conclusions

Among eyes in our study population, good-quality PCI data was equally accurate in patients with or without an inter-eye AEL difference > 0.30 mm. Confirmatory AEL measurements using different AEL measuring modalities in patients with a large inter-eye AEL difference may not be necessary.

Preoperative measurements for cataract surgery: a comparison of ultrasound and optical biometric devices

PURPOSE

To evaluate differences in preoperative measurements and refractive outcomes between ultrasound and optical biometry when using the Barrett Universal II intraocular lens (IOL) power formula.

METHODS

In this consecutive case series, cataract extraction and IOL implantation cases from two surgical centers in Toronto, Canada, were recruited between January 2015 and July 2017. Differences between ultrasound (applanation or immersion A-scan) and optical biometry (IOLMaster 500) were compared for axial length (AL), anterior chamber depth and refractive outcomes. The primary outcome was the percentage of cases in each cohort within ± 0.50D of refractive error.

RESULTS

In total, 527 cataract cases underwent IOLMaster testing. Of these, 329 eyes (62.4%) were also measured by applanation A-scan, and the other 198 eyes (37.6%) received immersion A-scan testing. Applanation ultrasound led to 5.8%, 16.0% and 46.4% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 48.5%, 77.1% and 94.9%, respectively (n = 293, ± 0.50D: p < 0.001). Immersion ultrasound led to 31.2%, 57.6% and 91.2% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 42.4%, 72.0% and 92.0%, respectively (n = 125, ± 0.50D: p = 0.001). Applanation (n = 329, A-scan AL: 23.64 ± 1.67 mm, IOLMaster AL: 24.20 ± 1.70 mm, p < 0.001) and immersion ultrasound (n = 198, A-scan AL: 25.01 ± 2.06 mm, IOLMaster AL: 25.08 ± 2.13 mm, p = 0.002) yielded significantly lower AL values compared to optical biometry measurements.

CONCLUSIONS

Optical biometry yielded a significantly larger percentage of cases within ± 0.50D of refractive error compared to ultrasound biometry when using the Barrett Universal II IOL power formula.

Comparative Analysis of Swept-Source Optical Coherence Tomography and Partial Coherence Interferometry Biometers in the Prediction of Cataract Surgery Refractive Outcomes

Purpose

To compare the accuracy of pre-operative corneal measurements obtained with four devices, and the refractive outcomes of two optical biometers.

Setting

Private practice.

Design

Retrospective.

Methods

Data taken from biometric measurements on 299 consecutive eyes prior to cataract surgery were retrospectively analyzed using the Argos SS-Optical Biometer and the Lenstar LS900 PCI optical biometer. As part of the standard cataract surgery pre-operative exam, patients also underwent placido disk topography and Scheimpflug tomography. Keratometry, anterior chamber depth, corneal diameter, pupil diameter, central corneal thickness and axial length were all measured. The comparable measurements were compared. Finally, for those eyes where cataract surgery was performed, the post-operative refractive results were compared to the predictive results of the two biometers.

Results

The SS-OCT Argos was able to measure all eyes, while five eyes could not be measured with the Lenstar LS900 PCI. Axial length measurements were performed only with the Argos and Lenstar devices. The eyes that could not be measured by the Lenstar LS900 PCI included dense grade IV nuclear sclerosis and large posterior subcapsular cataracts. In the primary endpoints, there was strong correlation between the Argos and the Lenstar devices in eyes with an axial length between 20 and 30 mm.

Conclusion

The predictive accuracies of the Argos Optical Biometer and Lenstar LS900 PCI are similar, except in medium and long eyes, in which the predictive accuracy of Argos SS-OCT biometry was higher. The Argos system was found easier to use by technicians when compared to the other biometry devices.

Comparison of composite and segmental methods for acquiring optical axial length with swept-source optical coherence tomography

This study compared the optical axial length (AL) obtained by composite and segmental methods using swept-source optical coherence tomography (SS-OCT) devices, and demonstrated its effects on the post-operative refractive errors (RE) one month after cataract surgery. Conventional AL measured with the composite method used the mean refractive index. The segmented-AL method used individual refractive indices for each ocular medium. The composite AL (24.52 ± 2.03 mm) was significantly longer (P < 0.001) than the segmented AL (24.49 ± 1.97 mm) among a total of 374 eyes of 374 patients. Bland–Altman analysis revealed a negative proportional bias for the differences between composite and segmented ALs. Although there was no significant difference in the RE obtained by the composite and segmental methods (0.42 ± 0.38 D vs 0.41 ± 0.36 D, respectively, P = 0.35), subgroup analysis of extremely long eyes implanted with a low power intraocular lens indicated that predicted RE was significantly smaller with the segmental method (0.45 ± 0.86 D) than that with the composite method (0.80 ± 0.86 D, P < 0.001). Segmented AL with SS-OCT is more accurate than composite AL in eyes with extremely long AL and can improve post-operative hyperopic shifts in such eyes.

T2 formula in a highly myopic population, comparison with other methods and description of an improved approach for estimating corneal height

BACKGROUND

To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible ways to improve the estimation of corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia.

METHODS

In this retrospective case series, optical biometer measurements were taken for 63 highly myopic patients (> 25 mm) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ±0.50 D, ± 1.00 D, and greater than ±2.00 D. A method to improve the corneal height calculation is described.

RESULTS

The SRK/T formula (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone.

CONCLUSIONS

The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. An improved corneal height estimation method is described for the the T2 formula.

Accuracy of intraocular lens calculations based on fellow-eye biometry for phacovitrectomy for macula-off rhegmatogenous retinal detachments

OBJECTIVES

To determine the accuracy of using fellow-eye biometry for intraocular lens calculations for phacovitrectomy for macula off rhegmatogenous retinal detachments.

METHODS

Retrospective case review of phacovitrectomies for consecutive macula off retinal detachments over 10 years. Optical and/or ultrasound biometry was performed for affected and fellow eyes. Prediction error was determined by calculating the difference between predicted and actual refractive outcomes. Results from fellow- and same-eye biometry were compared.

RESULTS

Forty-two eyes were included. The mean prediction errors for fellow- and same-eye biometry were -0.01 ± 1.09 and -1.22 ± 2.32 dioptres, respectively, indicating a myopic shift for same eye biometry calculations. The mean absolute prediction errors for fellow and same eye biometry were 0.73 ± 0.80 and 1.57 ± 2.08 dioptres, respectively. The difference was statistically significant (P = 0.016).

CONCLUSIONS

When appropriate, intraocular lens calculations using fellow-eye biometry for phacovitrectomy for macula off rhegmatogenous retinal detachments are accurate and better than those from same-eye biometry.

Improved Refractive Outcomes of Small-Incision Extracapsular Cataract Surgery after Implementation of a Biometry Training Course

PURPOSE:

To determine whether a biometry training course could improve refractive outcomes of patients undergoing manual small-incision extracapsular cataract surgery (SICS).

MATERIALS AND METHODS:

This was a prospective, interventional, cohort study at the Pacific Eye Institute, Fiji. SICS refractive outcomes were evaluated before and after a structured biometry teaching course. Eyes that underwent evaluation and subsequent SICS with placement of a posterior chamber intraocular lens (IOL) were included. Axial length measurements were obtained using A-scan applanation ultrasound and keratometry with a handheld keratometer. Main outcome measures included mean absolute prediction error of IOL calculations, percentage of eyes within ±0.5 D and ±1.0 D of intended spherical equivalent, and proportion of eyes with ≥6/18 uncorrected visual acuity.

RESULTS:

A total of 240 eyes were analyzed: 120 eyes before and 120 eyes after the structured biometry training. The mean absolute prediction error was 50% lower following the training (1.13 ± 0.84 D pre vs. 0.56 ± 0.44 D post; P < 0.001). A higher percentage of the eyes had a postoperative spherical equivalent within ±0.5 D (26.7% pre vs. 52.5% post; P < 0.001) and ±1.0 D (55.0% pre vs. 90.0% post; P < 0.001) of the intended target. A higher proportion of the eyes achieved ≥6/18 uncorrected visual acuity (77.5% pre vs. 91.7% post, P = 0.004), while the proportion with ≥6/18 corrected visual acuity was similar (94.4% pre vs. 98.3% post; P = 0.28).

CONCLUSIONS:

A structured biometry training course may improve the accuracy of preoperative IOL calculations to achieve the postoperative refractive target. Ophthalmology training programs should include structured biometry teaching in their curricula.

Axial Length Shortening After Cataract Surgery: New Approach to Solve the Question

Purpose

To check if optical biometry can detect eventual corneal power (Km) and axial length (AL) cataract surgery-related changes that could influence the refractive outcome.

Methods

Patients scheduled for sequential bilateral cataract surgery between January and September 2017 were included in the present study. One hundred ninety-six eyes of 98 patients (48 males) were selected. Before surgery of the first eye, patients underwent a complete ophthalmic examination, including IOLMaster biometry; the same evaluations were repeated in both eyes the day before the fellow eye cataract surgery, performed at least 2 months after the first one. The differences in Km and AL in the first operated eyes were evaluated, and the fellow eyes were used as controls.

Results

Km differences in the operated eyes ranged from −1.97 to +0.98 diopter (D) (mean = −0.02 ± 0.36 D) (P = 0.89); in the nonoperated eyes they ranged from −0.6 to +0.7 D (mean = 0 ± 0.20 D) (P = 0.91). The AL differences (pseudophakic option) in the operated eyes ranged from −0.35 to +0.15 mm (mean = −0.10 ± 0.08 mm) (P < 0.001); with the aphakic option they ranged from −0.24 to + 0.26 mm (mean = 0.01 ± 0.08 mm) (P= 0.38). In the nonoperated eyes, the AL differences ranged from −0.04 to +0.06 mm (mean= 0 ± 0.02 mm) (P = 0.02).

Conclusions

The modern phaco-technique seems not to induce changes in Km and AL, supporting the hypothesis that the differences in AL are due to an incorrect estimation in pseudophakic eyes.

Translational Relevance

The results of our study may improve the AL measurements in pseudophakic eyes.

Comparison of optical biometry versus ultrasound biometry in cases with borderline signal-to-noise ratio

Purpose

To ascertain if optical biometry determination of axial length (AL) and intraocular lens (IOL) power is significantly different compared to ultrasound (US) biometry in cases with borderline signal-to-noise ratio (SNR).

Patients and methods

Sixty patients who had cataract and IOL Master biometry with borderline SNR (1.6–2.0) were included. A retrospective chart review was performed to compare data collected with optical biometry and US biometry in cataract cases with borderline SNR.

Results

Results showed that optical biometry IOL and AL measurements were not significantly different from the US measurements. Analysis also demonstrated good agreement between the two methods.

Conclusion

Our study suggests that, in cases of borderline quality data, IOL power and AL measurements with optical biometry are still useful in surgical planning and that additional US measurements may be used more as a corroborative tool.

Comparison of three optical biometers: IOLMaster 500, Lenstar LS 900 and Aladdin

PURPOSE

To evaluate the results of optical biometry using the IOLMaster 500, Lenstar LS 900 and Aladdin in eyes with cataract.

METHODS

In 231 eyes of 152 patients with cataract, the measurements of 3 different biometers were retrospectively compared. Paired comparisons were performed for axial length (AL), mean keratometry (mean K) and anterior chamber depth (ACD).

RESULTS

In only 197 of the 231 eyes (85.3%), it was possible to obtain reliable measurements of AL with all the three devices. It was not possible to determine AL in 16 eyes (6.9%) with Lenstar LS 900; in 19 eyes (8.2%) with Aladdin; and in 20 eyes (8.6%) with IOLMaster 500 possibly related to the severity of lens opacification (the corneas had good transparency in the eyes included in the study). There was a statistically significant difference in AL between IOLMaster 500 and the remaining two biometers (P = 0.03). However, the amount of difference was considered clinically not significant (0.04 mm). The mean keratometry (mean K) was determined in 203 eyes (87.9%) with all the three devices. Differences in mean K were between - 0.1 and 0.06 Diopters (D), which were considered neither statistically (P > 0.05) nor clinically significant. The anterior chamber depth (ACD) was determined in 197 eyes (85.28%) with all the three biometers. The differences between the three devices (0.03 to 0.13 mm) were not statistically significant and considered also clinically not significant.

CONCLUSIONS

There were no clinically significant differences between these 3 biometers in AL, mean K and ACD.

Accuracy of axial length measurements obtained by optical biometry and acoustic biometry in rhegmatogenous retinal detachment: a prospective study

Purpose

We compared the accuracy of axial length (AL) measurement obtained by optical biometry with that obtained by acoustic biometry in eyes with rhegmatogenous retinal detachment (RRD).

Patients and methods

This prospective descriptive analytic study measured the AL of eyes with RRD preoperatively and 3 months postoperatively using optical biometry (intraocular lens [IOL] master group) and acoustic biometry (immersion A-scan group). Preoperative and postoperative measurements were compared by paired t-test. The agreement between preoperative and postoperative measurements was analyzed using a Bland–Altman plot. Subgroup analysis of macular involvement status was performed.

Results

Twenty-seven eyes were analyzed in this study. The mean AL in the IOL master group was 23.58±0.97 mm preoperatively and 24.17±1.16 mm postoperatively; the mean difference was −0.59±0.90 mm (P = 0.007). The mean AL in the immersion A-scan group was 24.29±1.59 mm preoperatively and 24.27±1.69 mm postoperatively; the mean difference was 0.02±0.48 mm (P = 0.827). Bland–Altman analysis revealed disagreement between preoperative and postoperative AL measurements in both techniques. In subgroup analysis of macula with RRD, there were significant differences between preoperative and postoperative AL measurements in the IOL master group (P = 0.014).

Conclusion

Significant underestimation of AL measurement was observed when using the IOL master in eyes with RRD with macular involvement, which could affect IOL power selection.

Long-term Effect of Scleral Encircling on Axial Elongation

PURPOSE

To determine the long-term effect of scleral encircling on the progression of myopia.

DESIGN

Retrospective clinical cohort study.

METHODS

Setting: Single-center academic hospital (Severance Hospital).

STUDY POPULATION

The study included 76 eyes of 38 patients (mean age 37.21 ± 15.76) who had undergone retinal detachment surgery with scleral encircling. Observational Procedures: Axial length was measured preoperatively, at 6 months after surgery, and at the most recent visit. Patients were followed up for at least 12 months.

MAIN OUTCOME MEASURE

The changes of axial length per month between operated eyes and contralateral eyes (control group).

RESULTS

The operated group showed more rapid changes in axial length from 6 months after surgery to the time of the last follow-up than did the control group (0.020 ± 0.033 mm/month vs 0.002 ± 0.002 mm/month, P = .002; mean follow-up, 26.05 ± 11.39 months). Similar trends were observed during the entire follow-up period (0.065 ± 0.062 mm/month vs 0.008 ± 0.020 mm/month, P < .001). Subgroup analysis showed that both the myopic and highly myopic group showed no significant difference of change in rate of axial length during the first 6 postoperative months (P = .267), from 6 months after surgery to the final assessment point (P = .144), or over the entire observation period (P = .507).

CONCLUSIONS

Encircling the sclera may accelerate progression of myopia by significantly increasing axial length. The degree of myopia itself does not contribute to a significant difference in the increased axial length.

Epiretinal membrane surgery: an analysis of 2-step sequential- or combined phacovitrectomy surgery on refraction and macular anatomy in a prospective trial

PURPOSE

To assess the impact of combined phacoemulsification-vitrectomy and sequential surgery for idiopathic epiretinal membrane (ERM) on refractive error (RE) and macular morphology.

METHODS

In this prospective clinical trial, we allocated phakic eyes with ERM to (1) cataract surgery and subsequent pars plana vitrectomy (PPV) (CAT group), (2) PPV and subsequent cataract surgery (VIT group) or (3) phaco-vitrectomy (COMBI group). Examinations were at baseline, one month after each surgery, and at 3 months and 12 months of follow-up. Primary outcome was the RE (the difference between predicted and achieved spherical equivalent); secondary outcomes were best-corrected visual acuity (BCVA), and incidence of cystoid macular oedema (CME) defined as >10% increment of central subfield macular thickness (CSMT).

RESULTS

Sixty-two eyes were enrolled. The mean RE showed a small myopic shift of -0.36D in all groups 1 month after surgery, decreasing after 12 months to -0.17D. The absolute value of the RE (ARE) ranged 0.49-0.68D after 12 months. In the immediate postoperative period, there was a higher incidence of CME in the CAT group. There was no significant difference in final RE, ARE, BCVA and CSMT between the groups. Four cases (17%) in the CAT group had resolved visual complaints and improved BCVA after cataract surgery resulting in no need for PPV within the follow-up period.

CONCLUSION

Surgery for idiopathic ERM in phakic eyes with either phaco-vitrectomy or sequential surgery are equal approaches with respect to functional- (RE, BCVA) and anatomical outcomes (CME, CSMT). However, if starting with cataract surgery, 17% of the cases may not need subsequent PPV.

Enhanced Penetration for Axial Length Measurement of Eyes with Dense Cataracts Using Swept Source Optical Coherence Tomography: A Consecutive Observational Study

Introduction

The aim of this study was to find cases in which the axial eye length could not be measured with partial coherence interferometry (PCI) technology and to assess if it could be measured using swept source optical coherence tomography (ss-OCT) technology.

Methods

All patients were measured at their pre-assessment visit 1 week prior to cataract surgery using conventional optical biometry (PCI technology, IOLMaster 500, Carl Zeiss Meditec AG, Jena, Germany). Patients in whom one or both eyes could not be measured using PCI technology were invited to participate in the study and to be measured with the ss-OCT (IOL Master 700, Carl Zeiss Meditec AG, Jena, Germany) device.

Results

Altogether, 1226 eyes of 613 patients were measured consecutively, and 78 eyes were not measured successfully with PCI technology. Among those with unsuccessfully measured eyes, 23 patients were willing to participate in the study, and two of those were also unsuccessfully measured with the ss-OCT device (8.7%, 2/23). However, 91.3% (21/23) of the eyes that were unsuccessfully scanned with PCI technology were measurable with the ss-OCT device. The estimated overall rate of unsuccessful scans with the ss-OCT device was 0.5% (6/1226) (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p_{{\chi^{2} }} $$\end{document}pχ2 < 0.01).

Conclusion

ss-OCT technology significantly improves the rate of attainable axial eye length measurements, especially in eyes with posterior subcapsular cataracts, but also in eyes with dense nuclear cataracts, except for white cataracts.

Predicting the refractive outcome and accuracy of IOL power calculation after phacoemulsification using the SRK/T formula with ultrasound biometry in medium axial lengths

PURPOSE

To evaluate the accuracy of the SRK/T formula using ultrasound (US) biometry in predicting a target postoperative refraction of ±1.00D in eyes with medium axial length (AL) that underwent phacoemulsification.

METHODS

The present study was a retrospective analysis, which included 538 eyes with an AL from 22.0 to 24.60 mm that underwent phacoemulsification and foldable intraocular lens (IOL) implantation (six different IOLs) in the bag. Preoperative AL was measured by US biometry and IOL power (IOLp) was calculated with the SRK/T formula. Patients had a complete ophthalmic examination, preoperatively and 1, 7, and 30 days after surgery. The achieved spherical equivalent (SE) and the prediction error (PE) were calculated. The prediction error was defined as the difference between attempted predicted target refraction and the achieved postoperative SE refraction. Statistical analysis was performed with SPSS V21.

RESULTS

The mean age of the patients was 66.96±9.67 years, the mean AL was 23.29±0.62 mm, the mean K1 was 43.62±1.49D, the mean K2 was 43.69±1.53D, the mean IOL power was 21.066±1.464D, the mean attempted (predicted) SE was -0.178±0.266D, and the mean achieved SE was -0.252±0.562D. The mean PE (difference between predicted and achieved SE) showed a relatively hyperopic shift (mean ± standard deviation: 0.074±0.542D, ranging from -1.855 to 2.170D, P=0.001). A total of 93.87% of eyes were within ±1.00D of the PE and 92.75% of eyes within ±1.00D of achieved postoperative refraction. A total of 39 eyes (7.25%) had a refractive surprise. A total of 32 of 39 eyes were more myopic than -1.00D and 7 of them were more hypermetropic than +1.00D. There was no correlation between the mean PE and IOL type, AL, K1, K2, and IOLp. There were a positive statistically significant correlation between PE and age (r=0.095; P=0.028) and a negative statistically significant correlation between achieved SE and AL (Spearman's r=-0.125; P=0.04), and age (r=-0.141; P=0.01).

CONCLUSION

The IOLp calculation using the SRK/T formula with US biometry may demonstrate very good postoperative refractive outcomes in medium eyes with a few refractive surprises.

Optical Biometry Derived Axial Length Measurements Following Intravitreal Anti-Vascular Endothelial Growth Factor Treatment for Macular Edema

PURPOSE

To evaluate axial length (AL) alterations in patients with macular disease over the course of intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment.

METHODS

In this prospective, comparative study, 33 patients with macular edema underwent unilaterally intravitreal anti-VEGF therapy and were followed for two months; the contralateral eyes were considered as controls. Central retinal thickness (CRT) was measured with spectral-domain optical coherence tomography and AL with an IOL-Master optical biometer.

RESULTS

CRT of the treated eyes decreased by 35.33 ± 65.59 μm (range, -222.00-67 μm), while AL increased by 0.008 ± 0.062 mm (range, -0.11-0.18 mm). CRT of the control group decreased by 9.82 ± 65.40 μm (range, -203-182 μm), and AL increased by 0.011 ± 0.129 mm (range, -0.20-0.67 mm). No significant correlation was detected between CRT and AL parameters (rhos=0.026, P=0.882).

CONCLUSIONS

Anti-VEGF administration has no significant impact on optical biometry-derived AL measurements.

Prediction accuracy of intraocular lens power calculation methods after laser refractive surgery

Background

This study aimed to evaluate the prediction accuracy of postoperative refractions using partial coherence interferometry (IOL-Master) and applanation ultrasound (AL-3000) assisted with corneal topography (TMS-4) in eyes that had undergone myopic laser-assisted in situ keratomileusis (LASIK).

Methods

Haigis-L formula, Koch–Maloney method using Haigis formula, Shammas clinically derived K-value (simulated keratometric value) correction (Shammas c.d.) using Haigis formula, and Shammas post-LASIK (Shammas-PL) formula were used in eyes with myopic LASIK. Constants were derived from the optimized constants in 133 virgin eyes. Refractive outcomes were determined by streak retinoscopy and subjective manifest refraction. Methods and formulas were evaluated by mean error (ME), standard deviation (SD), range of error, mean absolute error (MAE), median absolute error, 95% confidence interval of MAE, and percentage of eyes within ±0.5 diopter (D), ±1.0 D, and ±1.5 D of prediction.

Results

SDs of the Haigis-L, Koch-Maloney method using the Haigis formula, Shammas c.d. using the Haigis formula, and the Shammas-PL formula using IOL-Master were 0.721, 0.695, 0.695, and 0.698; and those using AL-3000 assisted with TMS-4 were 0.782, 0.741, 0.743, and 0.778, respectively.

Conclusions

No-history methods that corrected corneal power with measurements using IOL-Master were promising in myopic post-LASIK eyes, but still a gap in prediction accuracy exists between virgin eyes and post-LASIK eyes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-017-0439-x) contains supplementary material, which is available to authorized users.

Circumferential silicone sponge scleral buckling induced axial length changes: case series and comparison to literature

Background

This study compared axial length changes induced by circumferential scleral buckling using a silicone sponge with literature reports for solid silicone rubber.

Methods

Records of patients treated with scleral buckling in 2009–2013 using a silicone sponge, with preoperative axial length biometry measurements were reviewed. Additional information included age, type of surgery, additional surgeries, phakic status and anatomical success of reattachment. Patients underwent repeat biometry. The medical literature was reviewed for articles describing axial length changes induced by circumferential buckling using solid silicone rubber.

Results

Twenty-eight patients (mean age 49.7 years, range 16–72) met the inclusion criteria. Mean axial length was 25.38 mm preoperatively and 26.12 mm at least 6 months postoperatively (SD 0.50 ± 0.09, p < 0.001); a mean increase of 0.74 mm. Half the patients subsequently underwent cataract surgery. Post-operative changes were not significant compared to pre-surgical refraction and corneal astigmatism. Axial length change was not significant between sexes (9 women and 19 men).

Conclusions

Axial length changes induced by circumferential scleral buckling using silicone sponge exclusively are similar to those reported in the literature for solid silicone rubber buckles. Scleral buckling using a silicone sponge, which may offer several surgical advantages, induces an acceptable axial length change similar to that seen with widely-used solid silicone rubber buckles.

Comparison of Biometric Values and Intraocular Lens Power Calculations Obtained by Ultrasound and Optical Biometry

This study sought to compare the biometric values and intraocular lens (IOL) power obtained by standard ultrasound and optical biometry.

We examined 29 eyes in preparation for cataract surgery. None of the patients had refractive surgery or corneal anomaly. In all patients, the horizontal and vertical refractive power of the cornea was determined using a keratometer (Bausch&Lomb). The axial length of the eye was determined via A-scan ultrasound (BVI-compact-V-plus) using Hollady’s formula. The IOL power and complete biometric measurements were obtained via an IOL Master-500-Zeiss using the Hollady-2 formula. All obtained values were compared and analysed using the statistical program SPSS 20.

The average age of treated patients was 71.21±1.68 years. In 16 patients with dense cataracts (55.17%), it was not possible to determine the IOL power by optical biometry. Optical biometry obtained significantly increased axial length values of 24.04±0.29 mm compared with those obtained with ultrasound biometry (23.89±0.28 mm, p=0.003). The mean refractive cornea power values of the horizontal meridian measured using a keratometer (42.50±0.47 D) and an IOL Master (42.69±0.49 D) were not statistically different (p=0.187). The mean values of the refractive cornea power of the vertical meridian obtained using a keratometer (42.62±0.48D) and an IOL Master (43.36±0.51 D) exhibited a statistically significant difference (p=0.000). The keratometer obtained statistically significant lower mean values of corneal refractive power (42.73±0.32 D) compared with those obtained with optical biometry (43.22±0.35 D, p=0.000). Ultrasound biometry obtained significantly increased the mean values of IOL power (20.19±0.48D) compared with those obtained with optical biometry (19.71±0.48 D, p=0.018).

The large number of patients who receive an operation for dense cataracts indicate the need for representation of both biometric methods in our clinical practice.

Scheimpflug camera combined with placido-disk corneal topography and optical biometry for intraocular lens power calculation

The purpose of this study was to compare the keratometry (K) values obtained by the Scheimpflug camera combined with placido-disk corneal topography (Sirius) and optical biometry (Lenstar) for intraocular lens (IOL) power calculation before the cataract surgery, and to evaluate the accuracy of postoperative refraction. 50 eyes of 40 patients were scheduled to have phacoemulsification with the implantation of a posterior chamber intraocular lens. The IOL power was calculated using the SRK/T formula with Lenstar K and K readings from Sirius. Simulated K (SimK), K at 3-, 5-, and 7-mm zones from Sirius were compared with Lenstar K readings. The accuracy of these parameters was determined by calculating the mean absolute error (MAE). The mean Lenstar K value was 44.05 diopters (D) ±1.93 (SD) and SimK, K at 3-, 5-, and 7-mm zones were 43.85 ± 1.91, 43.88 ± 1.9, 43.84 ± 1.9, 43.66 ± 1.85 D, respectively. There was no statistically significant difference between the K readings (P = 0.901). When Lenstar was used for the corneal power measurements, MAE was 0.42 ± 0.33 D, but when simK of Sirius was used, it was 0.37 ± 0.32 D (the lowest MAE (0.36 ± 0.32 D) was achieved as a result of 5 mm K measurement), but it was not statistically significant (P = 0.892). Of all the K readings of Sirius and Lenstar, Sirius 5-mm zone K readings were the best in predicting a more precise IOL power. The corneal power measurements with the Scheimpflug camera combined with placido-disk corneal topography can be safely used for IOL power calculation.

High myopia and cataract surgery

PURPOSE OF REVIEW

Cataract surgery in high myopes is challenging. Using third-generation intraocular lens (IOL) formulas, without adjustments, hyperopic refractive outcomes are common. We discuss these issues, focusing on the various lens formulas and transformations that have improved postoperative accuracy.

RECENT FINDINGS

Axial length measurement error has been largely overcome by the use of optical interferometry. Despite this, consistent hyperopic errors are still reported. We reviewed the postoperative refraction results compared with the predicted refractions using: standard formulas (Holladay 1, SRK/T, Hoffer Q, and Haigis) with manufacturers' optical lens constants, the User Group for Laser Interference Biometry (ULIB) constants, manufacturers' constants with axial length adjustment method, and fourth-generation IOL formulas (Barrett Universal II, Holladay 2, and Olsen).

SUMMARY

Improved predictive results is obtained with the Barrett Universal II (software constants), Haigis (ULIB), SRK/T, Holladay 2 (software constants), and Olsen (software constants) formulas in eyes with axial lengths greater than 26.0 mm and IOL powers greater than 6.0 D. In eyes with axial lengths greater than 26.0 mm and IOL less than 6.0 D, the Barrett Universal II formula (software constants) and the Haigis (axial length adjusted) and Holladay 1 formulas (axial length-adjusted) should be used.

Comparison of ocular biometry measurements by applanation and immersion A-scan techniques

Purpose

The study compared ocular biometry values using applanation and immersion techniques to determine the most applicable method for our tertiary training centre where personnel with different levels of experience and expertise in biometry take measurements used in calculation of required intraocular lens before cataract surgery.

Methods

The study was a prospective cross-sectional comparative study of different techniques of ocular biometry from diagnostic equipment (biometry probe 10 MHz Sonomed^® A-scan (PACSCAN 300A, USA). Measurement variables were obtained among children and adults undergoing cataract surgery. Scleral (Prager) shell was used for the immersion technique followed by the contact technique by the same examiner.

Results

The biometry values of 92 eyes of 92 adult were taken. Their ages ranged from 18 to 95 years with a mean of 64.7 (SD ± 12.9) years. There were 55 (59.8%) males and 37 (40.2%) females, with a male to female ratio of 1.5:1.

Average axial length (22.0–24.4 mm) eyes were the most common eyes measured in 75 (81.5%) of the cases. The means of the axial lengths biometry values with immersion and contact technique were 23.66(±1.36) and 23.46 mm (±1.46); the axial length differences was 0.2 ± 0.26 mm (range 0.0–0.94 mm) and statistically significant (95% CI of the Difference 0.15 to 0.26, p = 0.000). The Standard deviation SD (mm) of Individual Eye Axial Length showed a mean of 0.03 ± 0.04 (0.0–0.3) mm for immersion and for contact technique 0.14 ± 0.12(0.0–0.6)mm.

Conclusion

There was a significant difference in ocular biometry measurement with the contact and immersion ultrasound techniques. The immersion technique had better repeatability, thus it is ideal in a training hospital setting in a typical in sub-Saharan Africa who have limited resources to employ a dedicated person to do biometry; and where the different operators of A-scan machines have different levels of experience and expertise.

Comparison of the biometric formulas used for applanation A-scan ultrasound biometry

The purpose of the study was to compare the accuracy of various biometric formulas for predicting postoperative refraction determined using applanation A-scan ultrasound. This retrospective comparative study included 485 eyes that underwent uneventful phacoemulsification with intraocular lens (IOL) implantation. Applanation A-scan ultrasound biometry and postoperative manifest refraction were obtained in all eyes. Biometric data were entered into each of the five IOL power calculation formulas: SRK-II, SRK/T, Holladay I, Hoffer Q, and Binkhorst II. All eyes were divided into three groups according to axial length: short (≤22.0 mm), average (22.0-25.0 mm), and long (≥25.0 mm) eyes. The postoperative spherical equivalent was calculated and compared with the predicted refractive error using each biometric formula. The results showed that all formulas had significantly lower mean absolute error (MAE) in comparison with Binkhorst II formula (P < 0.01). The lowest MAE was obtained with the SRK-II for average (0.49 ± 0.40 D) and short (0.67 ± 0.54 D) eyes and the SRK/T for long (0.61 ± 0.50 D) eyes. The highest postoperative hyperopic shift was seen with the SRK-II for average (46.8 %), short (28.1 %), and long (48.4 %) eyes. The highest postoperative myopic shift was seen with the Holladay I for average (66.4 %) and long (71.0 %) eyes and the SRK/T for short eyes (80.6 %). In conclusion, the SRK-II formula produced the lowest MAE in average and short eyes and the SRK/T formula produced the lowest MAE in long eyes. The SRK-II has the highest postoperative hyperopic shift in all eyes. The highest postoperative myopic shift is with the Holladay I for average and long eyes and SRK/T for short eyes.