Accuracy of the refractive prediction determined by multiple currently available intraocular lens power calculation formulas in small eyes

Phacoemulsification in Nanophthalmic Eye, a Way to Manage Glaucoma: Case Report

A rare condition called nanophthalmos causes variable degrees of vision impairment. One may present with nanophthalmos as a hereditary or sporadic condition. There have been documented cases of nanophthalmos treated with bilateral cataract extraction and intraocular lens (IOL) implantation for intractable secondary glaucoma or chronic angle-closure glaucoma. We describe a case of closed-angle glaucoma in a nanophthalmic eye with increased intraocular pressure (IOP) on full medical treatment, along with concurrent drug side effects. As a first surgical procedure, we recommend phacoemulsification of the clear lens + IOL. The challenge in treating nanophthalmic eyes lies in managing the possibility of developing glaucoma in an eye where anatomical conditions make surgery extremely risky. This must be balanced against the advantages of lessening exposure contact in the trabecular meshwork and optimizing the anterior chamber for potential future glaucoma surgery, which can improve the prognosis in these cases. Lastly, it is critical to have a thorough conversation with the patient about the aims, risks, and advantages. The patient's understanding and expectations should also be crystal apparent. The primary objective should always be to enhance the circumstances for the most effective glaucoma therapy, not to perform refractive surgery.

Zonular dialysis and cataract surgery: results from a UK tertiary eye care referral centre

OBJECTIVE

Zonular dialysis (ZD), referred to as the presence of a deficient zonular support for the lenticular capsule, might be the result of several causes and be detected only at the time of cataract surgery. The aim of this study was to evaluate pre-, intra-, and postoperative features of eyes with ZD regardless of the etiology detected during cataract surgery.

METHODS

A single-centre retrospective observational cohort study was performed at Moorfields Eye Hospital (NHS Foundation Trust, London, U.K.) to identify patients who underwent cataract surgery whose procedure was intraoperatively described as being complicated by ZD between January 1, 2014, and August 22, 2019. Patient characteristics, intraoperative clinical findings, visual and refractive outcomes, and postoperative complications were recorded.

RESULTS

ZD was identified intraoperatively in 447 eyes. In most cases (213 of 223; 96.8%), patients underwent a phacoemulsification procedure, not requiring any conversion to intracapsular or extracapsular extraction technique. Intraoperative complications increased to 46.2% (103 of 223), with no significant correlation with ZD width. Capsular tension rings (CTRs) were implanted in 43.4% of patients (97 of 223). The use of CTRs correlated with better postoperative visual and refractive outcomes.

CONCLUSIONS

ZD is a serious complication of cataract surgery requiring prompt intraoperative diagnosis and proper management. While it tends to worsen cataract surgery outcomes, the implantation of CTRs during the surgical procedure seems to be associated with better postoperative visual and refractive results.

Immediate sequential vs delayed sequential bilateral cataract surgery: systematic review and meta-analysis

The main aim of this systematic review and meta-analysis was to evaluate the safety and efficacy profile of immediate sequential bilateral cataract surgery (ISBCS) compared with delayed sequential bilateral cataract surgery (DSBCS). MEDLINE Ovid, EMBASE, and CENTRAL databases were searched. Outcome measures were postoperative visual acuity, postoperative spherical equivalent (refractive outcome), endophthalmitis, corneal edema, pseudophakic macular edema, and posterior capsule rupture (PCR). 13 articles met criteria for final inclusion. A total of 11 068 622 participants (18 802 043 eyes) were included. No statistically significant differences between ISBCS and DSBCS were identified in all the postoperative outcomes evaluated. However, a higher risk for PCR was identified in the ISBCS group from the pooled analysis of nonrandomized studies (risk ratio, 1.34, 95% CI, 1.08-1.67, P = .0081). In our view, the ISBCS approach has an acceptable safety-efficacy profile, comparable with DSBCS. Future investigations are warranted, with a focus on the analysis of risk factors for surgical complications, patient-reported outcome-measures, and cost effectiveness.

A Comparative Study on the Accuracy of IOL Calculation Formulas in Nanophthalmos and Relative Anterior Microphthalmos

PURPOSE

We sought to compare the prediction accuracy of 6 intraocular lens (IOL) formulas, namely, the Haigis, Hoffer Q, Holladay I, SRK/T, Barrett Universal II and Hoffer QST formulas, in microphthalmic eyes, including those with nanophthalmos and relative anterior microphthalmos (RAM).

DESIGN

Retrospective case series.

METHODS

Twenty-six eyes with nanophthalmos (axial length [AL] 16.84 ± 1.36 mm, range 15.25 mm-19.82 mm) and 12 eyes with RAM (corneal diameter 8.41 ± 0.92 mm, range 7.00 mm-9.50 mm) receiving cataract surgery were included. The IOL Master 500 was used for biometry; thus, lens thickness (LT) was omitted in the IOL power calculation. The mean and median arithmetic and absolute prediction errors (PEs) of the 6 original calculation formulas, the absolute PEs of the 6 formulas after optimization, and the proportion of PEs within ±0.25 diopters (D), ±0.5 D, ±1 D, and ±2 D with each formula were compared. The factors influencing PE were analyzed by multivariate regression.

RESULTS

In the nanophthalmos group, the overall prediction results were shifted to myopia. The original Haigis formula had the smallest median absolute PE (1.61 D, P < 0.001), and the optimized Haigis formula had the highest proportion of PEs within ±0.25 D, ±0.5 D, and ±1 D. In the RAM group, the overall prediction results were not significantly different from 0 (P > .05). No significant difference was found among the formulas before optimization (P = .146) and after optimization (P = .161), but the optimized Barrett Universal II formula had the highest proportion of PEs within ±1 D and ±2 D.

CONCLUSIONS

When omitting the LT parameter in the calculation, the Haigis formula was the most accurate in cataract patients with nanophthalmos (AL <20 mm) among the 6 IOL calculation formulas, and the Barrett Universal II formula had the highest accuracy in cataract patients with RAM (corneal diameter ≤9.5 mm).

Comparison of the Barrett Universal II, Kane and VRF-G formulas with existing intraocular lens calculation formulas in eyes with short axial lengths

BACKGROUND

To compare the accuracy of recently developed modern intraocular lens (IOL) power formulas (Barrett Universal II, Kane and VRF-G) with existing IOL power formulas in eyes with an axial length (AL) ≤ 22 mm.

METHODS

This analysis comprised 172 eyes of 172 patients operated on by one surgeon (LT) with one IQ SN60WF (Alcon Labs, Fort Worth, TX, USA) hydrophobic lens. Ten IOL formulas were evaluated: Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, Holladay 2, Kane, SRK/T, T2, VRF and VRF-G. The median absolute error (MedAE), mean absolute error (MAE), standard deviation (SD) and all descriptive statistics were evaluated. Percentages of eyes with a prediction error within ±0.25 D, ±0.50 D, ±0.75 D and ±1.00 D were calculated using standard optimised constants for the entire range of axial lengths.

RESULTS

The VRF-G, Haigis and Kane produced the smallest MedAE among all formulas (0.242 D, 0.247 D and 0.263 D, respectively) and had the highest percentage of eyes with a PE within ±0.50 D (75.67%, 73.84% and 75.16%, respectively). The Barrett was less accurate (0.298 D and 68.02%, respectively). Statistically significant differences were found predominantly between the VRF-G (P < 0.05), Kane (P < 0.05) and Haigis (P < 0.05) and all other formulas. The percentage of eyes with a PE within ±0.50 D ranged from 66.28% to 75.67%.

CONCLUSIONS

In eyes with AL ≤ 22.0 mm, the VRF-G, Haigis and Kane were the most accurate predictors of postoperative refraction, and the Barrett formula was less predictable.

Effectiveness, Sensitivity, and Specificity of Intraocular Lens Power Calculation Formulas for Short Eyes

Objectives:

Materials and Methods:

Results:

Conclusion:

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.

THE EXACTNESS OF INTRAOCULAR LENS POWER CALCULATION FORMULAS FOR SHORT EYES AND CORRELATION BETWEEN METHOD ACCURACY AND EYEBALL AXIAL LENGTH

PURPOSE

To compare the accuracy of intraocular lens power calculation formulas and to examine the correlation of this exactness with the axial length for eyes shorter than 22.00 mm Methods: The data of hyperopic patients who underwent uneventful phacoemulsification between October 2015 and June 2019 were reviewed. The intraocular lens power for each patient was calculated using 6 formulas (Holladay1, SRK/T, Hoffer Q, Holladay 2, Haigis and Barrett Universal II) before cataract surgery. Postoperative refraction was measured, and refractive prediction error was calculated 3 months after phacoemulsification. The correlation between axial length and absolute error was evaluated.

RESULTS

Fifty-six patients (62 eyes) whose ocular axial length ranged between 20.58 mm and 21.97 mm were included in the study. The Hoffer Q formula achieved the lowest mean absolute error of 0.09 (±0.08 D). A significant correlation for the Hoffer Q (&#961; = -0.329, p = 0.009) and the SRK/T (&#961; = 0.321, p = 0.011) formula was observed.

CONCLUSIONS

1. The Hoffer Q formula obtained the lowest absolute error and was recommended for intraocular lens power calculation for eyeballs with axial length shorter than 22.0 mm. 2. The correlation between axial length and absolute error is a factor which should be considered when calculating intraocular lens power.

Cataract Surgery in Short Eyes, Including Nanophthalmos: Visual Outcomes, Complications and Refractive Results

Background

To report the visual outcomes, complications and refractive results of phacoemulsification surgery and intraocular lens implantation in a large series of adult patients with short and nanophthalmic eyes.

Methods

The records of all patients with axial length <21.0 mm undergoing phacoemulsification with intraocular lens implantation at an adult teaching hospital were retrospectively reviewed. The main outcome measures were corrected distance visual acuity and refraction at 90 days after surgery and intra- and postoperative complications occurring during the follow-up period.

Results

A total of 71 eyes of 51 patients (median age 71 years, interquartile range 62–75.5) were included. Surgery resulted in an improvement in corrected distance visual acuity in 53 eyes (74.6%) (95% confidence interval, logMAR 0.11–0.29) and was logMAR 0.30 or better in 47 eyes (66.2%). Worsening of corrected distance visual acuity occurred in 9 eyes (12.7%). Median postoperative refractive error was −0.75 dioptres. SRK/T and Kane formula were more accurate in predicting postoperative refraction than Barrett Universal II and Hoffer Q when based on mean absolute error (P < 0.005). Complications occurred in 18 eyes (25.4%). The most frequent complications were iris prolapse, Descemet’s membrane and/or endothelial trauma, transient severe corneal edema and cystoid macular edema. There was no statistically significant difference in complication rates between senior surgeons and senior trainees (P = 0.66).

Conclusion

Cataract surgery in short and nanophthalmic eyes is challenging with a higher complication rate than routine cataract surgery, but frequently results in good visual outcomes. Postoperative refractive outcomes are more difficult to predict in this cohort.

Clinical Accuracy of 18 IOL Power Formulas in 241 Short Eyes

PURPOSE

To analyze the accuracy of 18 intraocular lens (IOL) power calculation formulas in eyes with axial length (AL) ≤ 22 mm.

METHODS

We analyzed 241 eyes of 241 patients. Eighteen formulas were evaluated: Barrett Universal II (BUII), EVO 2.0, Haigis, Hoffer Q, Holladay 1 and 2, Cooke K6, Kane, LadasSuperFormula AI, Naeser 2, Olsen, Panacea, Pearl-DGS, RBF 2.0, SRK/T, T2, VRF and VRF-G. Optical biometry was performed with an IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). With lens constants optimized for the whole range of AL, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE) and the percentage of eyes with PEs within ±0.25 D, ±0.50 D and <±1.00 D were calculated.

RESULTS

Post-hoc analysis of the absolute PE revealed statistically significant differences (P < .05) between some of the newer formulas (K6, Kane, Naeser 2, Olsen and VRF-G), which obtained the lowest MedAE (respectively, 0.308, 0.300, 0.277, 0.310 and 0.276 D) and the remaining ones. These formulas yielded also the highest percentage of eyes with a PE within ±0.50 D (70.54%, 72.20%, 71.37%, 70.95% and 73.03%, respectively), whereas Panacea and SRK/T yielded the lowest percentage (62.24%), with a stastically significant difference (P < .05) with respect to most formulas.

CONCLUSION

In eyes with AL ≤22.0 mm, new formulas (K6, Kane, Naeser 2, Olsen and VRF-G) offer the most accurate predictions of postoperative refraction.

Recurring themes during cataract assessment and surgery

The aim of this review was to discuss frequently encountered themes such as cataract surgery in presence of age-related macular degeneration (AMD), dementia, Immediate Sequential Bilateral Cataract Surgery (ISBCS), discussing non-standard intraocular lens (IOL) options during consultation in the National Health Services (NHS) and the choice of the biometric formulae based on axial length. Individual groups of authors worked independently on each topic. We found that cataract surgery does improve visual acuity in AMD patients but the need for cataract surgery should be individualised. In patients with dementia, cataract surgery should be considered 'sooner rather than later' as progression may prevent individuals presenting for surgery. This should be planned after discussion of patients' best interests with any carers; multifocal IOLs are not proven to be the best option in these patients. ISBCS gives comparable outcomes to delayed sequential surgeries with a low risk of bilateral endophthalmitis and it can be cost-saving and efficient. Patients are entitled to know all suitable IOL options that can improve their quality of life. Deliberately withholding this information or pressuring patients to choose a non-standard IOL is inappropriate. However, one should be mindful of the not spending inappropriate amounts of time discussing these in the NHS setting which may affect care of other NHS patients. Evidence suggests Hoffer Q, Haigis, Hill-RBF and Kane formulae for shorter eyes; Barrett Universal II (BU II), Holladay II, Haigis and Kane formulae for longer eyes and BU II, Hill-RBF and Kane formulae for medium axial length eyes.

Bilateral implantation of +56 and +58 diopter custom-made intraocular lenses in patient with extreme nanophthalmos

Purpose

To present the case of a 60-year-old patient with severe nanophthalmic eyes, who underwent cataract surgery with a bilateral implantation of custom-made high-power intraocular lenses (IOLs).

Observations

The axial length was 14.94 and 15.05 mm of the right and the left eye, respectively. The preoperative corrected distance visual acuity (CDVA) was +0.46 logMAR (20/63) in the right eye and +0.58 logMAR (20/80) in the left eye with rigid contact lenses of +17.5 D bilaterally. The calculated IOL power for emmetropia with different formulas ranged from +55.28 to +70.09 D. The IOL power selection was based on the average value from four formulas (Haigis, Holladay 1, Holladay 2, SRK/T) with the target refraction of emmetropia. Custom-made +56.0 and + 58.0 D Aspira-aAY IOLs (HumanOptics AG, Erlangen, Germany) were implanted without any complications. The postoperative CDVA was +0.40 logMAR (20/50) and +0.60 logMAR (20/80). The manifest refraction spherical equivalents were +0.625 D and −0.375 D.

Conclusions and importance

Even in eyes with the axial length of only 15 mm, cataract surgery can be successfully performed after adequate preparation. High-power customized IOLs allow complete correction of hyperopia but caution is required with the results from different IOL power calculation formulas, which can be misleading.

Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review

The refractive outcome of cataract surgery is influenced by the choice of intraocular lens (IOL) power formula and the accuracy of the various devices used to measure the eye (including intraoperative aberrometry [IA]). This review aimed to cover the breadth of literature over the previous 10 years, focusing on 3 main questions: (1) What IOL power formulas currently are available and which is the most accurate? (2) What biometry devices are available, do the measurements they obtain differ from one another, and will this cause a clinically significant change in IOL power selection? and (3) Does IA improve refractive outcomes? A literature review was performed by searching the PubMed database for articles on each of these topics that identified 1313 articles, of which 166 were included in the review. For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups. Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment. All biometry devices delivered highly reproducible measurements, and most comparative studies showed little difference in the average measures for all the biometric variables between devices. The differences seen resulted in minimal clinically significant effects on IOL power selection. The main difference found between devices was the ability to measure successfully through dense cataracts, with swept-source OCT-based machines performing better than partial coherence interferometry and optical low-coherence reflectometry devices. Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.

Accuracy of biometric formulae for intraocular lens power calculation in a teaching hospital

AIM

To evaluate the accuracy of three commonly used biometric formulae across different axial lengths (ALs) at one United States Veterans Affairs teaching hospital.

METHODS

A retrospective chart review was conducted from November 2013 to May 2018. One eye of each patient who underwent cataract surgery with a monofocal intraocular lens (IOL) was included. The range of postoperative follow-up period was from 3wk to 4mo. The Holladay 2, Barrett Universal II, and Hill-Radial Basis Function (Hill-RBF) formulae were used to predict the postoperative refraction for all cataract surgeries. For each formula, we calculated the prediction errors [including mean absolute prediction error (MAE)] and the percentage of eyes within ±0.25 diopter (D) and ±0.5 D of predicted refraction. We performed subgroup analyses for short (AL<22.0 mm), medium (AL 22.0-25.0 mm), and long eyes (AL>25.0 mm).

RESULTS

A total of 1131 patients were screened, and 909 met the inclusion criteria. Resident ophthalmologists were the primary surgeons in 710 (78.1%) cases. We found no statistically significant difference in predictive accuracy among the three formulae over the entire AL range or in the short, medium, and long eye subgroups. Across the entire AL range, the Hill-RBF formula resulted in the lowest MAE (0.384 D) and the highest percentage of eyes with postoperative refraction within ±0.25 D (42.7%) and ±0.5 D (75.5%) of predicted. All three formulae had the highest MAEs (>0.5 D) and lowest percentage within ±0.5 D of predicted refraction (<55%) in short eyes.

CONCLUSION

In cataract surgery patients at our teaching hospital, three commonly used biometric formulae demonstrate similar refractive accuracy across all ALs. Short eyes pose the greatest challenge to predicting postoperative refractive error.

Visual Function after Implantation of a Presbyopia-Correcting Trifocal Intraocular Lens

PURPOSE

To evaluate distance, intermediate, and near visual performance in patients implanted with a trifocal aspheric presbyopia-correcting intraocular lens (IOL).

METHODS

Forty patients were bilaterally implanted with the AcrySofIQ PanOptix IOL after femtosecond laser-assisted lens surgery. Binocular best corrected distance visual acuity (CDVA) (4 m), best distance-corrected near visual acuity (DCNVA) (40 and 30 cm), best corrected distance intermediate visual acuity (DCIVA) (70, 60, and 50 cm), binocular distance contrast sensitivity under photopic conditions (85 cd/m2), and defocus curves were evaluated at 6-months.

RESULTS

Six months postoperatively, the mean binocular Snellen decimal CDVA and DCNVA were 0.94 ± 0.10 (ranging from 0.70 to 1.25) and 0.85 ± 0.13 (ranging from 0.63 to 1.00), respectively. At a distance, all patients showed a cumulative binocular distance-corrected visual acuity of 0.8 or better, and about 80% (n = 31) of the patients had a value of 1.0 (20/20). At near and intermediate distances, all patients showed a cumulative distance-corrected visual acuity of 0.5 (20/40) or better at 30, 40, 50, 60, and 70 cm. Specifically, 50 cm showed the highest percentage of patients with larger values of visual acuity (60% [n = 26] with 20/20). Defocus curve showed a wide range of useful vision with two peaks of best visual acuity at distance and at 50 cm, and the binocular distance contrast sensitivity was within normal limits.

CONCLUSIONS

The outcomes of the present study show that the visual performance obtained with bilateral implantation of the trifocal aspheric AcrySofIQ PanOptix IOL is good at far, intermediate, and near distances.

[Calculation of intraocular lens power in surgical treatment of extreme hyperopia]

Accuracy of calculation of the intraocular lens (IOL) power in eyes with short axial length is inferior to one in emmetropic eyes. Most studies focus on relatively standard eyes.

PURPOSE

To assess the accuracy of power calculation for IOL used to correct extreme hyperopia and to compare available formulas based on their predictive capacity.

MATERIAL AND METHODS

Results of 13 implantations involving IOLs of at least 40 Diopters (D) in power were retrospectively evaluated. IOL power was calculated using five formulas: Haigis, Hoffer Q, HolladayI, SRKII, SRK/T. Mean numerical refractive prediction error (RPE) and mean absolute refractive prediction error (ARPE) were calculated. Mean and median ARPE were computed after optimizing the A₀ constant. Proportions of eyes within certain RPE limits were compared between the formulas.

RESULTS

Mean RPE ranged from 1.43 to 11.71 D before adjustment and from 1.08 to 5.34 D after adjustment (p<0.0001). Haigis formula produced the least RPE, and SRKII - the most. Pairwise comparison by mean ARPE after adjustment revealed no statistically significant difference between Haigis and Hoffer Q formulas. Comparison of formulas by percentage of eyes with minimal RPE identified Haigis and Hoffer Q as the most accurate, while the difference between the two was not statistically significant. The difference between the most accurate formulas (Haigis and Hoffer Q) and the least accurate (SRKII) was statistically significant.

CONCLUSION

In eyes with extremely short anterior-posterior axis, prediction errors in IOL power calculations are relatively frequent (only 31-46% of eyes are within ±0.5 D) and warrant reduction. Among the evaluated formulas, Haigis and Hoffer Q are the most accurate. In order to improve the accuracy of IOL power calculations, it is necessary to employ personalized constants.

Intraoperative optical coherence tomography measurements of aphakic eyes to predict postoperative position of 2 intraocular lens designs

PURPOSE

To evaluate intraoperative anterior chamber depth (ACD) measurements of the aphakic eye to predict the postoperative ACD and compare 2 intraocular lens (IOL) designs.

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective study.

METHODS

In this prospective study, patients scheduled for cataract surgery received a plate-haptic IOL (Asphina, Carl Zeiss Meditec AG) or an open-loop haptic IOL (ZCB00, Johnson & Johnson). Preoperatively, optical biometry (IOLMaster 700, CZM, or Lenstar, Haag-Streit) was performed. Intraoperatively, a prototype setup was used to perform time-domain OCT scans of the anterior eye segment (Visante connected to OPMI Lumera 200, both CZM). The intraoperative ACD was measured and used to predict the postoperative IOL position. Optical biometry and subjective refraction and autorefraction (RM 8800, Topcon) were performed 2 months postoperatively.

RESULTS

The study comprised 203 eyes of 203 patients. A partial least-square regression model for ACD generated 2 months postoperatively showed that the predictive power of the intraoperative ACD (0.48) was highest followed by the axial eye length (0.45) and then the preoperatively measured ACD (0.30). These findings were confirmed in a bootstrapping model. Regression models combining the preoperative ACD and intraoperative ACD resulted in further significant improvement.

CONCLUSIONS

Intraoperative ACD measurements predicted the postoperative position of open-loop IOLs and plate-haptic IOLs better than preoperative ACD measurements. Combining preoperative and intraoperative ACD measurements further improved the prediction.

Estimation of intraocular lens position from full crystalline lens geometry: towards a new generation of intraocular lens power calculation formulas

In a cataract surgery, the opacified crystalline lens is replaced by an artificial intraocular lens (IOL). To optimize the visual quality after surgery, the intraocular lens to be implanted must be selected preoperatively for every individual patient. Different generations of formulas have been proposed for selecting the intraocular lens dioptric power as a function of its estimated postoperative position. However, very few formulas include crystalline lens information, in most cases only one-dimensional. The present study proposes a new formula to preoperatively estimate the postoperative IOL position (ELP) based on information of the 3-dimensional full shape of the crystalline lens, obtained from quantitative eye anterior segment optical coherence tomography imaging. Real patients were measured before and after cataract surgery (IOL implantation). The IOL position and the postoperative refraction estimation errors were calculated by subtracting the preoperative estimations from the actual values measured after surgery. The proposed ELP formula produced lower estimation errors for both parameters -ELP and refraction- than the predictions obtained with standard state-of-the-art methods, and opens new avenues to the development of new generation IOL power calculation formulas that improve refractive and visual outcomes.

[Is Holladay 2 formula acurate enough for calculating intraocular lens power in non-standard eyes?]

PURPOSE

To evaluate the benefit of the Holladay 2 formula versus the 3rd generation formulae in calculating the IOL power in eyes with non-standard axial length or keratometry before cataract surgery.

PATIENTS

Retrospectiv study from January to December 2015. The inclusion critaeria were axial length (AL) <22mm or >26mm, or average keratometry <42 D or >46 D, dividing the patients in 4 groups respectively. The 7 parameters required to calculate the Holladay 2 formula were collected. The final refractive result was turned into spherical equivalent to calculate the optimal power retrospectively. Then, the results obtained using the other formulae were compared with the optimal IOL power.

RESULTS

One hundred and twenty-six eyes operated by two surgeons were included. In the high AL group (n=32), the SRK/T was the most accurate formula; regarding the low AL group (n=36), the Hoffer Q and Holladay 2 formulae performed better; for the steep cornea group (n=27), the Hoffer Q, Haigis, Holladay 1 and 2 formulae were not different; last, the Holladay 1 and 2 were more accurate in the flat cornea group (n=33).

CONCLUSION

In our study, the Holladay 2 formula does not seem to be better than the others for calculating IOL power in non-standard eyes. Preoperative eye features in such non-standard cases should be taken into account before the surgery to choose the more suitable formula.

Predictability of formulae for intraocular lens power calculation according to the age of implantation in paediatric cataract

Aims

To analyse the predictability of diverse intraocular lens (IOL) power calculation formulae in paediatric patients with congenital cataract.

Methods

The medical records of patients who underwent cataract surgery and posterior chamber IOL implantation (in-the-bag) for congenital cataract before 17 years of age were reviewed retrospectively. Target refractions calculated by Sanders-Retzlaff-Kraff (SRK)/II, SRK/T and Hoffer-Q formulae were compared with the actual refraction. Patients were subgroup according to the age at IOL implantation (age group 0–24 months, 25–60 months, 61–120 months, 121–203 months), and we compared mean prediction error (PE) and mean absolute error (AE) for each formula. Corrected AE was obtained by linear regression analysis.

Results

Totally 481 eyes were included in the final analysis. Both SRK/II and SRK/T yielded the lowest mean AE in the age group 0–24 months and SRK/II yielded the lowest mean AE in the age group 25–60 months. For every formula, the mean PE was positive during the first five years of age, which converged to zero according to age as IOL implantation increases. The tendency for immediate postoperative overcorrection in younger patients (<6 years) could be improved by corrected formulae based on the linear regression equation.

Conclusions

Patients with congenital cataract who underwent IOL implantation within 5 years of age showed higher AE than the older ones did. Among the three formulae evaluated, SRK/II consistently provided the best predictive result in these patients. For patients aged >10 years, all three formulae showed favourable predictive abilities.

Comparison of Hill-radial basis function, Barrett Universal and current third generation formulas for the calculation of intraocular lens power during cataract surgery

IMPORTANCE

This study represents a novel comparison of recently introduced intraocular lens power calculation formulas.

BACKGROUND

To compare current new generation formulas for calculating the intraocular lens power for a standard cohort of patients undergoing cataract and lens replacement surgery in a private group practice in Australia.

DESIGN

Retrospective case series comparison.

PARTICIPANTS

Postoperative results from 400 consecutive patients undergoing implantation of an SN60WF intraocular lens post cataract removal by 12 surgeons were used.

METHODS

Refractive outcomes were compared with expected targets to determine the predicted refractive outcomes using the Hill-radial basis function, Barrett Universal II and readily available third or fourth generation intraocular lens power calculation formulas.

MAIN OUTCOME MEASURE

Mean absolute predicted error.

RESULTS

The mean absolute predicted difference ranged from 0.30 to 0.34 D. There was no overall significant difference in the predicted difference or variance between formulas. All formulas achieved greater than 78.3% of eyes within ±0.5 D of intended refraction. The Hill-radial basis function and Barrett formulas provided the lowest mean numerical error compared with existing formulas in short and long eyes, respectively. The Barrett Universal II formula had the lowest percentage of refractive surprises (>1 D from predicted error) across all axial lengths.

CONCLUSIONS AND RELEVANCE

Acceptable outcomes can be achieved with optical biometry, consistent surgical technique and use of current intraocular lens power calculation formulas. The Barrett Universal II formula may provide the lowest risk of refractive surprise compared with other intraocular lens power calculation formulas.

Anterior segment configuration as a predictive factor for refractive outcome after cataract surgery in patients with glaucoma

Background

To compare refractive outcomes after cataract surgery between patients with closed-angle and open-angle glaucoma and evaluate the influence of preoperative factors on refractive outcomes in patients with glaucoma.

Methods

Patients diagnosed with glaucoma and who underwent uncomplicated cataract surgery were enrolled in this retrospective observational study. We collected data including age, history of prior laser peripheral iridotomy and trabeculectomy, type of glaucoma, manifest refraction, intraocular pressure, axial length, and various anterior segment parameters using anterior-segment optical coherence tomography. Factors associated with unsatisfactory refractive outcome at postoperative 6 month were evaluated.

Results

A total of 143 eyes (143 subjects) were included. Of these, 49 and 94 had closed-angle and open-angle glaucoma, respectively. At postoperative-6 month evaluation, the mean absolute error (MAE) predicted by the SRK-II and SRK-T formulae was 0.67 ± 0.61 and 0.81 ± 0.66 diopters (D), respectively. The overall predictability of achieving within ± 1.0 D of target was 76.92 % and 72.73 %, respectively. At a cutoff value of 1.0 D for MAE, there was no statistical significant difference in refractive outcome between the closed-angle and open-angle glaucoma groups. Logistic regression modeling showed that large lens vault (LV) was a significant predictor of unsatisfactory refractive outcome after cataract surgery in patients with glaucoma.

Conclusions

When considering cataract surgery in patients with glaucoma, surgeons should recognize that the refractive outcomes may be unsatisfactory in eyes with large LV.

Influence of Patient Age on Intraocular Lens Power Prediction Error

PURPOSE

To examine whether intraocular lens (IOL) power prediction error (PE) after cataract surgery differs according to patient age.

DESIGN

Prospective cohort study.

METHODS

We consecutively enrolled 75 eyes of 75 patients 59 years of age or younger, and 150 eyes of 150 patients in each of 3 age groups (60-69, 70-79, and 80-89 years), for whom phacoemulsification and implantation of a single-piece acrylic IOL was planned. The IOL power was calculated using the optimized SRK/T formula. Objective refraction was measured using an autorefractometer at approximately 3 months postoperatively, and the mean arithmetic PE and median absolute PE were compared among age groups.

RESULTS

The mean preoperative refractive error predicted by the SRK/T formula was similar among age groups (P = .4179). The mean postoperative spherical equivalent was significantly more myopic in younger patients (P < .0001). Mean PE was -0.24 diopters (D) in those ≤59 years of age, -0.17 D in those 60-69 years of age, -0.11 D in those 70-79 years of age, and -0.05 D in those 80-89 years of age; the mean PE was less myopic in older patients (P = .0008). The median absolute PE did not differ significantly among groups (P = .6192). Mean PE was positively correlated with age (P < .0001). Multiple regression analysis revealed that age, preoperative axial length, average corneal curvature, and anterior chamber depth were independent predictors of the age-related difference in PE.

CONCLUSION

PE was less myopic by approximately 0.06 D per decade as age increased, suggesting that patient age should be considered when selecting IOL power.

Cataract surgery in the small eye

The surgical management of cataract in the small eye presents the ophthalmic surgeon with numerous challenges. An understanding of the anatomic classification in addition to a thorough preoperative assessment will help individualize each case and enable the surgeon to better prepare for the obstacles that might be encountered during surgery. Small eyes are especially challenging in terms of intraocular lens (IOL) calculations and possible current limitations of available IOL powers, which could necessitate alternative means of achieving emmetropia. Surgical strategies for minimizing complications and maximizing good outcomes can be developed from knowledge of the anatomic differences between various small-eye conditions and the pathologies that may be associated with each. A thorough understanding of the challenges inherent in these cases and the management of intraoperative and postoperative complications will ensure that surgeons approaching the correction of these eyes will achieve the best possible surgical results.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Mensurações do bulbo ocular e cálculo do poder dióptrico da lente intraocular em miniporcos

Objetivou-se com este trabalho determinar o poder dióptrico da lente intraocular (LIO) em miniporco e as dimensões do bulbo do olho. Foram utilizados 17 miniporcos, sadios, adultos, machos e fêmeas, com peso médio de 70kg. Em todos os olhos foram realizadas a ultrassonografia modo A, a ceratometria e a medida da distância limbo a limbo. O cálculo do poder dióptrico da LIO foi obtido utilizando-se as fórmulas Haigis, Hoffer Q, SRK/T, Holladay I e Holladay II e o software Holladay IOL Consultant(r). Na comparação entre o sexo e a lateralidade do olho, não houve diferença nas variáveis biométricas e poder da LIO. A aplicação das fórmulas (Haigis, Holladay II, Holladay I, SRK/T e Hoffer Q) possibilitou o cálculo do poder da LIO. A Holladay II, fórmula que melhor individualiza o bulbo do olho do miniporco, estima valor dióptrico ao redor de 41 D. Os miniporcos têm potencial como modelo experimental em oftalmologia, relacionado ao seu menor porte e à facilidade no manejo, especialmente em experimentos de longa duração.