The effect of pupil dilation on biometric parameters of the Lenstar 900

Effect of mydriasis on chord mu value in cataract surgery candidates

PURPOSE

This study investigates the relationship between pupil size during biometry examinations and the chord mu value in candidates for cataract surgery.

METHODS

Retrospective analysis of ocular biometry measurements was performed on consecutive cataract surgery candidates above 50 years of age, examined between 2018 and 2020 at a single tertiary referral center. Statistical analysis assessed the association between pupil size and the chord mu value. The population was categorized into groups based on pupil size, and an analysis was conducted on the barycenter positions of the iris and pupil center for each group.

RESULTS

The analysis included 2877 patients. A weak positive correlation was observed between the chord mu value and pupil size using Pearson's test (r = 0.160, p < 0.01). Group stratification by pupil size indicated temporal and inferior shifts in pupil center barycenter as pupil size increased, reflecting asymmetrical pupil dilation during mydriasis. A moderate positive correlation between the chord mu value and chord alpha value was identified (Pearson's test, r = 0.641, p < 0.01). As expected, no correlation was found between chord alpha value and pupil size.

CONCLUSIONS

Chord mu values were higher in patients with mydriatic pupils, likely due to asymmetric pupil dilation and center displacement. Evaluating chord mu values requires considering pupil status and conducting biometry under standardized lighting to prevent misinterpretation caused by pharmacological dilation. This caution is crucial to avoid erroneously excluding eligible patients from multifocal IOL implants. Alternatively, the chord alpha value could serve as a more appropriate alternative in such scenarios.

Advantageous effect of pupil dilation on the quality of optical biometry axial length measurement in individuals with dense cataract

PURPOSE

To evaluate the effect of pharmacologic pupil dilation on the quality of axial length (AL) measurement in patients with dense cataracts and previous low-quality AL measurements performed without dilation.

SETTING

Shaare-Zedek Medical Center, Jerusalem, Israel.

DESIGN

Retrospective case series.

METHODS

All participants underwent swept-source optical coherence tomographic (SS-OCT) biometry. Those with low-quality AL measurements due to dense cataract underwent an additional SS-OCT biometric evaluation after pupil dilation, and the AL measurement of the same eye was recorded.

RESULTS

2076 patients underwent SS-OCT during the study period, and 177 (8.52%) had low-quality AL measurements because of dense cataract. 79 (44.63%, mean age 72.53 ± 13.27 years, 43 females) of those 177 patients underwent repeat SS-OCT biometric imaging after pharmacologic pupil dilation, and formed the study group. After pupil dilation, high-quality AL measurements were successfully obtained in 60 (75.95%) of the 79 eyes. The mean SD of the AL measurements decreased significantly ( P &amp;lt; .001), and the number of successful OCT scans per measurement increased significantly ( P &amp;lt; .001) after pupil dilation. The mean difference of the AL before and after pupil dilation was 0.03 ± 0.07 mm ( P &amp;lt; .001).

CONCLUSIONS

Pharmacologic pupil dilation improved the quality of SS-OCT biometrically measured AL in patients with low-quality AL measurement due to dense cataract. These results could potentially improve postoperative refractive outcomes after cataract surgery and reduce the need of additional AL measurements by more complicated alternative means in this group.

EFFECT OF PHARMACOLOGICAL PUPIL DILATION ON INTRAOCULAR LENS POWER CALCULATION IN PATIENTS INDICATED FOR CATARACT SURGERY

PURPOSE

To evaluate the influence of pupil dilation on ocular parameters measured by optical biometry and the influence of pupil dilation on intraocular lens (PC IOL) power calculation by using the third-generation (SRK/T) and the fourth-generation (Haigis) formula.

METHODS

40 eyes of patients indicated for cataract surgery were included in this study. Each patient was examined by optical biometer firstly without artificial mydriasis (AM) and then after AM, which was achieved using local application of short-term acting mydriatics. Biometric data were measured by Lenstar LS 900 optical biometer, we recorded axial length of the eye (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and corneal astigmatism and optical power of cornea. These data we measured were used for calculation of the PC IOL optical power using both the SRK/T and the Haigis formula. The target postoperative refraction was set to emmetropia. Statistical analysis was performed for evaluation of influence of AM on each ocular parameter and influence of AM on the recommended PC IOL power calculated by the SRK/T and the Haigis formula.

RESULTS

No statistically significant effect of AM on AL, LT and keratometry was demonstrated. On the contrary we demonstrated significant effect on CCT and ACD. No effect of AM on the PC IOL power calculation using the SRK/T formula was proved - the PC IOL optical power before AM and after AM did not differ in any case. When using the Haigis formula for the PC IOL power calculation, the recommended optical power of the PC IOL changed by +0.5 Dpt in 9 eyes, i.e., 22.5 % of the whole group, but statistical analysis did not show this change as statistically significant.

CONCLUSION

Pharmacological dilation of the pupil significantly affects some intraocular parameters measured by optical biometer and in the case of using the Haigis formula it can influence recommended power of the PC IOL. Conversely, when using the SRK/T formula, pharmacological dilation of pupil does not affect the recommended PC IOL power.

Effect of eyedrops and applanation tonometry on optical biometry

PURPOSE

To determine whether eyedrops (phenylephrine, tropicamide, and fluorescein-proparacaine) and Goldmann applanation tonometry (GAT) have an effect on optical biometry measurements for preoperative cataract surgery workup.

SETTING

George Washington University, Washington, DC.

DESIGN

Nonrandomized controlled trial.

METHODS

Participants older than 18 years with no contraindications to eyedrops or tonometry were recruited. Optical biometry measurements were obtained on a single eye using the Lenstar LS900. One drop each of phenylephrine, tropicamide, and fluorescein-proparacaine was applied to the same eye, and measurements were repeated. GAT was performed, and measurements were repeated. For controls, the contralateral eye was also measured at each interval.

RESULTS

There was no statistically significant difference in mean predicted postoperative refraction (PPOR) keratometry (K) 1, K2, or axis postdrops and post-GAT 62 eyes (n = 62). After drops were applied, mean central corneal thickness increased from 540 to 542 µm (P = .0002), mean anterior chamber depth (ACD) increased from 3.68 to 3.70 mm (P < .0001), and lens thickness (LT) decreased from 3.66 to 3.65 (P = .001). After GAT, ACD increased to 3.76 mm (P < .0001), and LT increased to 3.60 mm (P < .0001). There was no statistically significant difference in PPOR or other parameters for the control eyes (n = 5).

CONCLUSIONS

GAT and phenylephrine, tropicamide, and fluorescein-proparacaine drops did not affect the primary outcome of PPOR. This suggests that cataract surgery candidates do not need to return for a separate preoperative visit for optical biometry.

Comparison of effects of mydriatic drops (1% cyclopentolate and 0.5% tropicamide) on anterior segment parameters

Purpose

The purpose of this study is to investigate and compare the effects of cyclopentolate and tropicamide drops on anterior segment parameters in healthy individuals.

Methods

Two hundred and fifty-eight eyes of 129 healthy volunteers were included in this randomized clinical study. Cyclopentolate 1% drop was applied to 75 (58%) participants (group 1) and tropicamide 0.5% drop was applied to 54 (42%) participants (group 2). Flat keratometry (K1), steep keratometry (K2), axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white (WTW) distance, pupil diameter, total pupil offset and intraocular lens (IOL) power were measured before and after drops, using Lenstar 900 optical biometry.

Results

The increase in CCT, ACD, pupil diameter, and pupil offset was significant in group 1 after the drop (P < 0.05), while the increase in ACD, pupil diameter, and pupil offset was significant in group 2 (P < 0.05). When the two groups were compared, there was no significant difference in K1, K2, CCT, ACD, WTW, pupil diameter, pupil offset, and IOL power (using Sanders-Retzlaff-Kraff T formula) changes after drops (P > 0.05), whereas the change in AL was significant (P = 0.01).

Conclusion

The effects of cyclopentolate and tropicamide drops on anterior segment parameters were similar; they did not make significant changes in K1, K2, AL, WTW, and third-generation IOL power calculation. However, ACD values significantly changed after these drops; thus, measuring anterior segment parameters before mydriatic agents should be taken into account particularly for fourth-generation IOL formulas and phakic IOL implantation. The change in pupil offset, which can be important in excimer laser and multifocal IOL applications, was not clinically significant.

Relationship between Myopia Progression and School Entrance Age: A 2.5-Year Longitudinal Study

Objective

To investigate the association between myopia progression and school entrance age among Chinese schoolchildren and to suggest a more appropriate school age.

Methods

1,463 children aged six to nine years from Wenzhou, China, were examined and followed up for two and a half consecutive years. Their noncycloplegic refraction was measured twice each year by using an automatic refractometer; axial length (AL) and corneal radius of curvature (CRC) were tested annually by using the IOLMaster for 2.5 years. The questionnaires were completed by the children to collect detailed information regarding risk factors. Here, myopia is defined as a spherical equivalent less than −1.0D.

Results

The changes in spherical equivalent (SE) of 7-year-old children in grade 1 and grade 2 were −0.45D and -0.56D, while changes in AL were 0.59 mm and 0.62 mm, respectively. The SE changes of 8-year-old children in grade 2 and grade 3 were −0.54D and −0.75D; meanwhile, the AL changes were 0.57 mm and 0.61 mm, respectively. Significant statistical differences were observed in ocular biological structure parameters, except for corneal radius of curvature (CRC) or anterior chamber depth (ACD), among children with the same age in different grades during this study. The prevalence of myopia was also significantly higher in higher grades for children with same age.

Conclusions

Myopia is related to children's school entrance age. Children who start school in an earlier age are more likely to suffer from myopia, and the progression of myopia can be considerably faster. Therefore, it is recommended to enter school after the age of 7.

The effect of cycloplegia on the ocular biometry and intraocular lens power based on age

BACKGROUND

To investigate the effect of cycloplegia on the ocular biometry and intraocular lens (IOL) power in different age groups.

METHODS

This cross-sectional study enrolled 240 right eyes of 240 healthy volunteers. Three groups were formed (range to years; group 1: 50-60, group 2: 30-40 and group 3: 10-20, respectively). We measured keratometry, central corneal thickness (CCT), white-to-white (WtW) distance, anterior chamber depth (ACD), and axial lentgh (AL) both before and after cycloplegia. The IOL powers were calculated using Sanders-Retzlaff-Kraff/theoretical (SRK/T), Holladay 1 and Haigis formulas. AL-Scan (Nidek Co., Gamagori, Japan) was used for all measurements.

RESULTS

There was a significant increased in keratometry, CCT, ACD, AL, and Holladay 1 after cycloplegia (p < 0.05), whereas WtW, SRK/T, and Haigis were not changed significantly in group 1 (p > 0.05). Keratometry, SRK/T, Haigis, and Holladay 1 significantly decreased; ACD and WtW significantly increased postcycloplegia (p < 0.05) but AL and CCT did not change significantly in group 2 (p > 0.05). Significant increased in ACD, CCT, WtW, and AL, significant decreased in SRK/T and Haigis were observed postcycloplegia (p < 0.05), while the changes in keratometry and Holladay 1 were not significant in group 3 (p > 0.05).

CONCLUSIONS

This study demonstrated there is significant difference in many ocular parameters and IOL power formulas before and after cycloplegia. Especially, ACD showed significant changes in all age groups. Therefore, to avoid refractive prediction errors the IOL power calculation formulas using the ACD should be considered.

Influence of pupil dilation on the Barrett universal II (new generation), Haigis (4th generation), and SRK/T (3rd generation) intraocular lens calculation formulas: a retrospective study

BACKGROUND

Despite the surge in the number of cataract surgeries, there is limited information available regarding the influence of pupil dilation on predicted postoperative refraction and its comparison with recommended various intraocular lens power calculated using the different parameters. We used three different IOL power calculation formulas: Barrett Universal II (Barrett) (5-variable formula), Haigis (3-variable formula), and SRK/T (2-variable formula), in order to investigate the potential effect of pupil dilation on the predicted postoperative refraction (PPR) and recommended intraocular lens (IOL) power calculation.

METHODS

This retrospective study included 150 eyes. All variables were measured and calculated using a ZEISS IOL Master 700. The following variables were measured before and after dilation: anterior chamber depth (ACD), lens thickness (LT), white-to-white (WTW). PPR and recommended IOL power were calculated by Barrett, Haigis, and SRK/T IOL calculation formulas. The change in each variable before and after dilation, and the correlations between all changes were analyzed using the Wilcoxon signed-rank test and the Spearman's rank-order correlation test, respectively.

RESULTS

The mean absolute change (MAC) in PPR before and after dilation was found to be highest in the Barrett formula. Significant differences were found between each MAC (P <  0.0001). Significant changes were observed before and after dilation in ACD and LT (P <  0.0001), but not in WTW. Using the Barrett and Haigis formulas, there was a significant positive correlation between the change in PPR and change in ACD (P <  0.0001), and a negative correlation between change in PPR and change in LT (P <  0.0001). The correlations were strongest with the Barret formula followed by the Haigis, particularly in terms of LT. Changes in PPR determined by the Barrett formula also demonstrated a significant positive correlation with changes in WTW (P = 0.022). The recommended IOL power determined using Barrett and Haigis changed before and after dilation in 23.3 and 19.3% cases respectively, while SRK/T showed no change.

CONCLUSIONS

In terms of PPR and recommended IOL power, pupil dilation influenced mostly the Barrett formula. Given the stronger correlation between the changes in PPR when using Barrett and the changes in ACD, LT, and WTW, changes in ACD, LT, and WTW significantly affect how dilation influences the Barrett formula. Determining how dilation influences each formula and other variables is key to improving the accuracy of IOL calculations.

Influence of pupil dilation on predicted postoperative refraction and recommended IOL to obtain target postoperative refraction calculated by using third- and fourth-generation calculation formulas

Purpose

To evaluate the influence of pupil dilation on predicted postoperative refraction (PPR) and recommended intraocular lens (IOL) power to obtain target postoperative refraction calculated by using the third- and fourth-generation IOL power calculation formulas with a new optical biometer.

Methods

This retrospective study included 162 eyes with cataract that underwent uneventful phacoemulsification with IOL implantation. PPR, recommended IOL power, anterior chamber depth (ACD), and lens thickness (LT) were measured pre- and post-pupil dilation. The change in PPR detected by using third-generation (Hoffer Q and SRK/T) and fourth-generation formulas (Haigis and Holladay 2) and the changes in ACD and LT were evaluated pre- and postdilation. The influence of dilation on the recommended IOL power calculated by each formula was analyzed.

Result

ACD and LT significantly changed from pre- to postdilation. The mean absolute change in PPR between pre- and postdilation was significantly higher for fourth-generation formulas compared with third-generation formulas. The change in PPR between pre- and postdilation showed a significantly positive correlation with change in ACD and a significantly negative correlation with change in LT with fourth-generation formulas, but not with third-generation formulas. The discrepancy rate of recommended IOL power between pre- and postdilation calculated by fourth-generation formulas was significantly higher than that calculated by third-generation formulas.

Conclusion

ACD and LT significantly changed by dilation. PPR and recommended IOL power significantly changed more by dilation when using fourth-generation formulas compared with third-generation formulas. Given the significant correlations of the change in PPR (between the pre- and postdilation) in the fourth-generation formulas and the changes in ACD and LT, the latter changes may be key in influencing dilation in the fourth-generation power calculation. Knowledge of the influence of dilation on fourth-generation formulas could help improve IOL calculation.

Effect of pupil dilation on biometric measurements and intraocular lens power calculations in schoolchildren

Purpose

To investigate the effect of pupil dilation on ocular biometric parameters and intraocular lens (IOL) power calculation in schoolchildren using the Lenstar LS 900.

Methods

One hundred forty eyes of 140 healthy schoolchildren were included in the analysis. Axial length (AL), central corneal thickness (CCT), aqueous depth (AD), anterior chamber depth (ACD), lens thickness (LT), flat keratometry (K), steep K, astigmatism, white-to-white (WTW), and iris/pupil barycenter distance were measured, before and after pupil dilation. Anterior segment length (ASL) was defined as the sum of ACD and LT, and lens position (LP) was defined as ACD plus half of the LT. The relative lens position (RLP) was defined as LP divided by AL. IOL power was calculated using the eight formulas (Hill-RBF, Barrett, Haigis, Hoffer Q, Holladay, Olsen, SRK II, and SRK/T) integrated in the Lenstar LS 900. Parameters before and after pupil dilation were compared.

Results

AL, AD, ACD, LT, ASL, LP, RLP, flat K, iris barycenter distance, pupil barycenter distance, and PD differed significantly after pupil dilation (P < 0.001 in all cases), as compared to before dilation. The Olsen formula demonstrated significant differences in the magnitude of astigmatism (P = 0.010) and IOL power (P = 0.003) after pupil dilation. Using the different formulas, 23.6–40.7% of participants had IOL power changes of more than 0.50 diopters, while 0.7–1.4% had IOL changes of more than 1.0 diopter after pupil dilation.

Conclusions

Dilated and undilated pupil size affected the Lenstar LS 900 measurement of some ocular biometric parameters, and pupil dilation led to IOL power changes exceeding 0.50 diopters with a high percentage (from 23.6% to 40.7%) in schoolchildren, which should be noticed in clinical practice.

Choroidal thickness and myopia in relation to physical activity - the CHAMPS Eye Study

PURPOSE

To describe the relationship between choroidal thickness (CT) and myopia in relation to physical activity (PA) in a population-based child cohort.

METHODS

In a prospective study of 307 children from the CHAMPS Study Denmark, we used objective data from GT3X accelerometer worn at four periods between 2009 and 2015 to determine the amount and intensity of PA. Intensity was estimated as counts/minutes, and cut-off points were defined at four intensity levels. Eye examinations were performed in 2015 and included autorefraction in cycloplegia, axial length (AL) by biometric and fovea-centred enhanced depth imaging optical coherence tomography. By a semi-automated method, we measured the CT at 17 targets per eye representing anatomically different locations (subfoveal, 1 and 3 millimetre in each direction of fovea).

RESULTS

Mean age at the eye examination was 15.4 ± 0.7 years. The mean AL was 23.5 ± 0.9 mm, and the mean subfoveal CT was 369 ± 87 μm. Choroidal thickness (CT) was 331 ± 68 μm for the overall macula, 355 ± 78 μm for the 1-mm zone and 304 ± 60 μm for the 3-mm zone. All CT measurements were thinner in myopic eyes (p < 0.0001) and in boys (p < 0.05). We found no association between total PA and the CT by either mixed model analysis (p = 0.074) or linear regression by any intensity levels (p = 0.22, p = 0.15 and p = 0.43).

CONCLUSION

Among adolescents aged 14-17 years, there was no association between objective PA exposures and the CT, AL or refractive error.

Effect of Cycloplegia on Keratometric and Biometric Parameters in Keratoconus

Purpose. To obtain information about effect of cycloplegia on keratometry and biometry in keratoconus. Methods. 48 keratoconus (Group 1) and 52 healthy subjects (Group 2) were included in the study. We measured the flat meridian of the anterior corneal surface (K1), steep meridian of the anterior corneal surface (K2), lens thickness (LT), anterior chamber depth (ACD), and axial length (AL) using the Lenstar LS 900 before and after cycloplegia. Results. The median K1 in Group 1 was 45.64 D before and 45.42 D after cycloplegia, and the difference was statistically significant (P < 0.05). The median K2 in Group 1 was 50.96 D before and 50.17 D after cycloplegia, and the difference was significant (P < 0.05). The median K1 and K2 in Group 2 were 42.84 and 44.49 D, respectively, before cycloplegia, and 42.84 and 44.56 D after cycloplegia, and the differences were not statistically significant (all P > 0.05). There were significant differences in SE, LT, ACD, and RLP between before and after cycloplegia in either Group 1 (all P < 0.05) or Group 2 (all P < 0.05). There were not statistically significant differences in AL between before cycloplegia and after cycloplegia in either Group 1 (P = 0.533) or group 2 (P = 0.529). Conclusions. Flattened corneal curvature and increase in ACD following cycloplegia in keratoconus patients were detected.

Changes in Ocular Parameters and Intraocular Lens Powers in Aging Cycloplegic Eyes

PURPOSE

Age-related changes in lens elasticity and ciliary muscle contractility can affect how ocular parameters respond to cycloplegia, and therefore intraocular lens (IOL) power measurements calculated by formulas using anterior chamber depth (ACD), lens thickness (LT), or white-to-white (WtW) for effective lens position prediction can vary. In response, using swept-source optical biometry in prepresbyopic and presbyopic eyes, we investigated changes in ocular parameters and IOL power calculations attributable to cycloplegia.

DESIGN

Cross-sectional study.

METHODS

In 38 prepresbyopic and 42 presbyopic eyes, we measured pupil diameter, radius of corneal curvature values, central corneal thickness, WtW, ACD, LT, and axial length both before and after cycloplegia. We determined IOL power calculations with the Sanders-Retzlaff-Kraff/theoretical, Holladay 2, and Haigis formulas. To pinpoint the effect of cycloplegia, we recorded refractive predictions in pre- and postdilation conditions according to the same IOL power calculations, even if postdilation IOL power calculations had changed.

RESULTS

With cycloplegia, pupil diameter changed significantly more in presbyopic eyes (P < .001). Central corneal thickness decreased in prepresbyopic eyes (P = .048), whereas WtW increased in presbyopic eyes (P = .02). In both groups, ACD and LT changed significantly (P < .001). IOL power calculations according to the Holladay 2 formula differed in prepresbyopic eyes (P = .042), and refractive predictions with the Holladay 2 and Haigis formulas differed significantly in prepresbyopic eyes (P = .043 and P = .022, respectively).

CONCLUSION

Surgeons should consider the effect of cycloplegia on refractive prediction errors and IOL power calculations determined with Haigis and Holladay 2 formulas, especially in prepresbyopic ages.

Effect of pharmacological pupil dilation on measurements and iol power calculation made using the new swept-source optical coherence tomography-based optical biometer

PURPOSE

To determine whether pupil dilation affects biometric measurements and intraocular lens (IOL) power calculation made using the new swept-source optical coherence tomography-based optical biometer (IOLMaster 700^©; Carl Zeiss Meditec, Jena, Germany).

PROCEDURES

Eighty-one eyes of 81 patients evaluated for cataract surgery were prospectively examined using the IOLMaster 700^© before and after pupil dilation with tropicamide 1%. The measurements made were: axial length (AL), central corneal thickness (CCT), aqueous chamber depth (ACD), lens thickness (LT), mean keratometry (MK), white-to-white distance (WTW) and pupil diameter (PD). Holladay II and SRK/T formulas were used to calculate IOL power. Agreement between measurement modes (with and without dilation) was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

Mean patient age was 75.17±7.54 years (range: 57-92). Of the variables determined, CCT, ACD, LT and WTW varied significantly according to pupil dilation. Excellent intraobserver correlation was observed between measurements made before and after pupil dilation. Mean IOL power calculation using the Holladay 2 and SRK/T formulas were unmodified by pupil dilation.

CONCLUSIONS

The use of pupil dilation produces statistical yet not clinically significant differences in some IOLMaster 700^© measurements. However, it does not affect mean IOL power calculation.

Effect of pupillary dilation on Haigis formula-calculated intraocular lens power measurement by using optical biometry

PURPOSE

The purpose of this study was to evaluate the effect of pupillary dilation on the Haigis formula-calculated intraocular lens (IOL) power and ocular biometry measurements by using IOLMaster(®).

METHODS

A prospective study was performed for biometry measurements of 373 eyes of 192 healthy subjects using the IOLMaster at the outpatient department of King Chulalongkorn Memorial Hospital from February 2013 to July 2013. The axial length (AL), anterior chamber depth (ACD), keratometry (K), and IOL power were measured before and after 1% tropicamide eye drop instillation. The Haigis formula was used in the IOL power calculation with the predicted target to emmetropia. Each parameter was compared by a paired t-test prior to and after pupillary dilation. Bland-Altman plots were also used to determine the agreement between each parameter.

RESULTS

The mean age of the subjects was 53.74±14.41 years (range 18-93 years). No differences in AL (P=0.03), steepest K (P=0.42), and flattest K (P=0.41) were obtained from the IOLMaster after pupillary dilation. However, ACD and IOL power were significantly different postdilation (P<0.01 and P<0.01, respectively). In ACD and IOL power measurements, the concordance rates were 93.03% and 97.05% within 95% limits of agreement (-0.48 to 0.26 mm and -1.09 to 0.88 D, respectively) in the Bland-Altman plots.

CONCLUSION

Biometry measurements in the cycloplegic stage should be considered in the IOL formulas that use parameters other than AL and K.

Effect of pupil dilation on biometry measurements with partial coherence interferometry and its effect on IOL power formula calculation

PURPOSE

To determine if there are any differences between eye parameters measured by the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) biometer before and after dilating the pupil. The effect of those changes on intraocular lens (IOL) power calculation is also analyzed.

METHODS

A prospective observational study was carried out including 107 right eyes of 107 patients with cataract and no other ocular morbidity. An IOLMaster baseline measurement included axial length (AL), mean keratometry (K), and anterior chamber depth (ACD) (corneal epithelium to lens). A second measurement was taken 45 minutes after instillation of topical tropicamide and phenylephrine. Biometric variation was analyzed and prediction for IOL power based on the Haigis and the Sanders/Retzlaff/Kraff Theoretical (SRK/T) formulas was calculated for both measurements.

RESULTS

The ACD increased significantly after dilation (+0.12 ± 0.12 mm; p&lt;0.01). The AL and K variation was not significant: +0.00 ± 0.02 mm (p = 0.62) and +0.01 ± 0.22 D (p = 0.57), respectively. Pupil dilation did not affect IOL power calculation based on SRK/T formula either targeting emmetropia (-0.02 ± 0.26, p = 0.30) or the lowest myopic residual refraction (-0.03 ± 0.34, p = 0.30). However, using the Haigis formula significantly changed calculations for emmetropia (0.07 ± 0.34, p = 0.03) and for the lowest myopic refraction (0.10 ± 0.40, p = 0.01).

CONCLUSIONS

Pupil pharmacologic dilation produces a significant increase in ACD when measured by the IOLMaster. This change results in a different IOL power prediction according to the Haigis formula, which calculates the effective lens position taking into account the ACD.