Depth of focus in pseudophakic eyes

Depth of field and visual performance after implantation of a new hydrophobic trifocal intraocular lens

Purpose

To assess the depth of field (DOF) by means of defocus curve analysis applying different visual acuity criteria in patients following cataract surgery and bilateral implantation of a new trifocal diffractive intraocular lens (IOL).

Methods

Fifty eyes of 25 consecutive patients who underwent implantation of the Asqelio™ trifocal IOL (AST Products Inc., USA) were enrolled in this observational prospective study. Monocular subjective DOF was obtained from defocus curves with absolute and relative criteria of tolerance for different visual acuities values. Patient’s visual satisfaction, postoperative refraction and visual acuity at far, intermediate (67 cm) and near (40 cm) distances were also measured at 1 and 3-months post-surgery. Analysis of variance was used to assess differences in refractive error after the surgical procedure, and paired t-tests were used to assess differences in VA. Patient satisfaction results were reported as percentages.

Results

Spherical equivalent was 0.05 ± 0.23 D and residual cylinder 0.01 ± 0.23 D 3-months after the surgery. Absolute DOF obtained was 3.29 ± 0.91 D considering 0.1 LogMAR as cut-off value, and 4.82 ± 0.69 D when 0.3 logMAR as cutoff value. Relative DOF considering a drop of 0.1 logMAR from maximum visual acuity was 2.57 ± 0.82 D, and 1.27 ± 0.70 D when a drop of 0.04 logMAR was considered. Visual acuities obtained 3-months after the surgery were 0.03 ± 0.13, − 0.05 ± 0.06, 0.03 ± 0.08 and 0.04 ± 0.08 logMAR for uncorrected and best-corrected for distance, and best distance-corrected for intermediate and near distances, respectively. Average response to visual satisfaction queries was 8.24/10 at distance, 8.04/10 at intermediate, and 7.88/10 at near.

Conclusions

Patients implanted with this trifocal IOL showed a significant improvement in visual acuity at different distances providing wide absolute and relative DOF values. The outcomes demonstrate that this lens is predictable yielding good patient satisfaction rates.

Depth of field measures in pseudophakic eyes implanted with different type of presbyopia-correcting IOLS

To evaluate depth of field (DOF) provided by different presbyopia-correcting intraocular lens (IOL) designs, comparing the results obtained using different criteria for defining the defocus tolerance. A total of 150 eyes undergoing cataract surgery were enrolled and divided into 6 groups depending on the IOL implanted: AT.LISA Tri (Carl Zeiss Meditec), FineVision (PhysIOL), PanOptix (Alcon Laboratories), Tecnis Symfony (Johnson & Johnson Vision), Miniwell (SIFI MedTech) and Tecnis Synergy (Johnson & Johnson Vision). Subjective DOF was obtained from defocus curves with absolute and relative criteria of tolerance of 0.1 logMAR. Aberrometry was also measured and the visual strehl optical transference function (VSOTF) with percentage of degradation of 90%, 80% and 60% was used to quantify objectively the DOF. Tecnis Symfony, Tecnis Synergy and Panoptix IOL groups showed better subjective and objective DOF compared to the rest of IOL groups, being these differences statistically significant differences (p < 0.001). Comparison between subjective and objective DOF showed that subjective measures were higher for all IOLs, being also these differences statistically significant for all groups (p < 0.001). A moderate significant correlation was found between absolute subjective criteria and VSOTF60% (r = 0.73, p < 0.05). Objective and subjective measures of DOF are not comparable due to differences in methodologies and criterions to define the level of degradation tolerance. Nevertheless, both objective and subjective measures showed a trend to a greater DOF for Tecnis Symfony and Tecnis Synergy IOLs compared to most of trifocal diffractive designs, with the exception of PanOptix.

Effect of Cycloplegia on Corneal Biometrics and Refractive State

Purpose

To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system.

Methods

In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia.

Results

Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia (P < 0.001). The astigmatism power did not significantly change (P = 0.8), however, 26.8% of eyes with significant astigmatism experienced a change of more than 5 degrees in the axis of astigmatism. Changes in posterior corneal curvature were scant but statistically significant (P = 0.001). Moreover, corneal thickness was slightly increased in the central and paracentral regions (P < 0.001 and P < 0.001, respectively).

Conclusion

Cycloplegia causes a hyperopic shift and astigmatism axis changes, along with an increase in central and paracentral corneal thickness and change in posterior corneal curvature. The effects of cycloplegia on refraction and corneal biometrics should be considered before cataract and refractive surgeries.

Accommodative intraocular lenses: where are we and where we are going

Presbyopia still remains the last frontier of refractive surgery. Its surgical management is under constant evolution due to the limitations that exist today with respect to its management, which is probably in relation with the multifactorial basis in which presbyopia is clinically developed in the human. Until currently, virtually all surgical techniques that have been proposed for its correction are based on the induction of pseudoaccommodation in the presbyopic eye, including multifocality. However, the real restoration of accommodation is more complex, and it has been tried by the use of different, so called, “accommodative” pseudophakic intraocular lenses (AIOL). Overall, the reported results with these lenses by independent authors have been modest in relation with the restoration of the accommodative power of the eye and these modest benefits are usually lost with time due to the long term changes in the capsular bag. This fact made these lenses to be almost abandoned in the last few years, but there are currently other AIOL models being used with innovative mechanisms of action and different anatomical support outside the capsular bag that offer encouraging preliminary results that could bring a new potential of application to these types of lenses.

In this article, we will update the modern refractive surgeon about the fundamentals and provide updated information about the outcomes of AIOLs by reviewing the concept of accommodation, the different attempts that have been accomplished in the past, their demonstrated published results in human clinical trials, and the future alternatives that may arrive in the near future.

The clinical depth of field achievable with trifocal and monofocal intraocular lenses: theoretical considerations and proof of concept clinical results

BACKGROUND

To estimate the depth of field (DOF) achievable with multi-and monofocal intraocular lenses (IOLs) and compare with actual measurements of DOF in cases implanted with a trifocal IOL and biconvex monofocal IOL METHODS: I) Computer simulations were produced to describe the relationship between DOF, pupil size, preoperative ametropia, and retinal blur tolerance limit for a model eye implanted with either multi- or monofocal IOLs. II) Monocular DOF and pupil size were measured under distance viewing conditions between 3 and 6 months postoperative following uneventful cataract surgery. Cases were implanted with either i) trifocal aspheric IOL (n = 36), or ii) biconvex aspheric monofocal IOL (n = 26). DOF was also measured at 0.33 m in cases implanted with i).

RESULTS

Simulations revealed significant associations between DOF, pupil size, and retinal blur tolerance limit. The mean (±SD) DOF & pupil sizes were at distance for i)  above 2.59D (0.68) & 3.54 mm (0.377), and for ii) above 1.67D (0.51) & 2.90 mm (0.351), and for i) above 3.16D (0.46) at near. The difference between groups were significant for DOF and pupil size at distance (p < 0.001). DOF was significantly greater at near compared with distance in i) above (p < 0.001). For a pupil size of 3 mm, the simulations produce similar DOF values when the tolerance limit of retinal blur is 10 μ.

CONCLUSIONS

The DOF was significantly better after implanting the trifocal IOL compared with the monofocal IOL, and DOF is increased under near viewing conditions. The clinical results are similar to calculated DOF values when the tolerance limit of retinal blur is 10 μ.

The Predictability of Preoperative Pilocarpine-Induced Lens Shift on the Outcomes of Accommodating Intraocular Lenses Implanted in Senile Cataract Patients

Purpose. To evaluate the predictability of lens shift induced by pilocarpine (LSPilo) on the outcomes of accommodating intraocular lens (Acc-IOL) implantation. Methods. Twenty-four eyes of 24 senile cataract patients who underwent phacoemulsification and Acc-IOL implantation were enrolled. LSPilo was evaluated with anterior segment optical coherence tomography (AS-OCT). At 3 months postoperatively, the best corrected distance visual acuities (BCDVA), distance-corrected near visual acuities (DCNVA), and subjective and objective accommodations were measured. IOL shifts under accommodation stimulus (IOLSAcc) were evaluated with AS-OCT. Results. The mean LSPilo was 112.29 ± 30.72 µm. LSPilo was not associated with any preoperative parameters. The mean IOLSAcc was 130.46 ± 42.71 µm. The mean subjective and objective accommodation were 1.54 ± 0.39 D and 1.27 ± 0.41 D, respectively. The mean postoperative BCDVA and DCNVA (log MAR value) were 0.22 ± 0.11 and 0.24 ± 0.12, respectively. LSPilo positively correlated with IOLSAcc (r = 0.541; P = 0.006), subjective accommodation (r = 0.412; P = 0.022), and objective accommodation (r = 0.466; P = 0.045), respectively. Conclusion. LSPilo is an independent preoperative parameter associated with the postoperative Acc-IOL mobility and pseudophakic accommodation. It may offer valuable information for ophthalmologists in determining the suitable candidates for Acc-IOL implantation.

Measurement of amplitude of accommodation in young persons

BACKGROUND

The aim was to evaluate the amplitude of accommodation using test objects designed with constant angular size corresponding to 6/6 visual acuity.

METHODS

In total, 155 young volunteers with good ocular and systemic health aged between eight and 25 years were recruited for the study. A push-up method was conducted, with the near-vision target having a set of Landolt's broken circles. The angular size of the circles corresponded to a 6/6 visual acuity for various distances from 5.0 cm to 40 cm. To ensure precision of the object size, the electron beam lithographic technique was applied.

RESULTS

A general trend in a reduction in amplitude with the progression of age is coincident with data from previous studies; however, the magnitudes of the volume of accommodation in our study are substantially lower.

CONCLUSION

Test objects with constant angular size can increase the accuracy of 'push-up' accommodation measures.

Real and pseudoaccommodation in accommodative lenses

In the attempt to manage presbyopia, different intraocular lens designs have been proposed such as monofocal IOLs with monovision or multifocal IOLs. Even though the lenses mentioned offer satisfactory visual results, contemporary ophthalmology has not completely answered the presbyopic dilemma by simulating the accommodative properties of the crystalline lens itself. Accommodative IOLs were designed to fill this gap and provide satisfactory vision for all distances by restoring some degree of "pseudoaccommodation." Pseudo accommodative capability can be linked to monofocal IOL's as well but the results are not satisfactory enough to fully support unaided near vision. Pseudoaccommodation is a complex phenomenon that can be attributed to several static (i.e., pupil size, against-the-rule cylindrical refractive error, multifocality of the cornea) and dynamic (i.e., anterior movement of the implant itself) factors. Objective measurement of the accommodative capability offered by the accommodative IOLs is extremely difficult to obtain, and different methods such as autorefractometers, retinoscopy, and ultrasound imaging during accommodative effort, ray tracing, or pharmacological stimulation have been developed but the results are sometimes inconsistent. Despite the difficulties in measuring accommodation, accommodative IOLs represent the future in the attempt to successfully "cure" presbyopia.