Predicting Short-term Performance of Multifocal Contact Lenses

BCLA CLEAR Presbyopia: Management with contact lenses and spectacles

This paper seeks to outline the history, market situation, clinical management and product performance related to the correction of presbyopia with both contact lenses and spectacles. The history of the development of various optical forms of presbyopic correction are reviewed, and an overview is presented of the current market status of contact lenses and spectacles. Clinical considerations in the fitting and aftercare of presbyopic contact lens and spectacle lens wearers are presented, with general recommendations for best practice. Current options for contact lens correction of presbyopia include soft simultaneous, rigid translating and rigid simultaneous designs, in addition to monovision. Spectacle options include single vision lenses, bifocal lenses and a range of progressive addition lenses. The comparative performance of both contact lens and spectacle lens options is presented. With a significant proportion of the global population now being presbyopic, this overview is particularly timely and is designed to act as a guide for researchers, industry and eyecare practitioners alike.

Multifocal contact lens success predictability

PURPOSE

The current multi-study analysis combined data from three studies to quantify the relationship between the initial reaction to soft multifocal contact lens (MFCL) design types at dispensing and evaluate the predictability of overall vision satisfaction (OVS) and intention to purchase (ITP) after 1 week of wear.

METHOD

Three prospective studies tested MFCLs over 1-week of wear following the same protocol, using a range of potentially predictive ratings at dispensing, and both OVS and ITP at 1-week as an indicator acceptance level. In each study, two of MyDay® multifocal, clariti® 1 day multifocal, Biofinity® multifocal (worn as a daily disposable lens) or 1 DAY ACUVUE® MOIST MULTIFOCAL were dispensed for 1-week of daily wear. OVS was recorded on a 100-point VAS and ITP on a 5-point LIKERT scale. Fourteen possible predictors were entered in the statistical model, and predictability was assessed using Chi-square Automatic Interaction Detector (CHAID) statistical test.

RESULTS

A total of 210 participants (152 female & 58 male; 53.9 ± 6.5 years, range 41-71 years), representing 420 MFCL fits, equally distributed between emergent n = 65, established n = 70 and advanced n = 75 presbyopes, completed the studies. OVS on dispensing was the predictor of both OVS (p < 0.001) and ITP (p < 0.001) at 1-week. For OVS predictability, 70.8 % with OVS at dispensing > 91 points reported good OVS at 1-week and 73.4 % with OVS on dispensing ≤ 80 points reported poor OVS at 1-week. For ITP predictability, 74.6 % with OVS at dispensing > 94 points reported a positive ITP at 1-week and 65.9 % with OVS on dispensing ≤ 63 points reported negative ITP at 1-week.

CONCLUSION

Overall vision satisfaction at the time of dispensing MFCLs is a powerful indicator of both OVS and ITP after 1-week of wear. Initial patient subjective assessments provide a clinically useful indicator of the likeliness of success.

Two-Year Myopia Management Efficacy of Extended Depth of Focus Soft Contact Lenses (MYLO) in Caucasian Children

PURPOSE

To evaluate the progression of myopia as assessed by change in axial length (AL) and spherical equivalent (SE) from baseline in Caucasian children wearing extended depth of focus soft contact lenses (CLs) compared to distance single-vision spectacles.

DESIGN

Prospective non-randomized comparative clinical trial.

METHODS

A total of 90 children (6-13 years of age) with SE ranging from -0.75 to -10.00 diopters (D) were recruited. Of these children, 45 were fitted with CLs (MYLO, mark´ennovy), whereas 45 children wore spectacles. Cycloplegic refraction was measured with an auto-refractometer (Topcon-TRK-2P) and AL with an IOLMaster-700 (Zeiss) at 6-month intervals. Subjective responses after 1 month of CL wear related to vision and comfort were determined using a questionnaire with a scale from 1 (very poor) to 10 (excellent). High-contrast visual acuity (HCVA) and contrast sensitivity (CS) were evaluated at baseline, 12, and 24 months.

RESULTS

After 2 years, mean change in SE/AL in the CL group was -0.62 ± 0.30 D/0.37 ± 0.04 mm and -1.13 ± 0.20 D/0.66 ± 0.03 mm in the spectacles group (P < .001). Cumulative absolute reduction in axial elongation (CARE) was 0.29 ± 0.06 mm. Difference in SE change was -0.50 ± 0.34 D. Although 100% of CL group had an AL increase ≤0.50 mm, all participants increased ≥0.50 mm in the spectacles group. In all, 53% of the CL group and 1% in the spectacles group showed a progression in SE ≤ -0.50D. All questionnaire items showed a mean value ≥9. There was a reduction logMAR HCVA in the CL compared to the spectacles group but it was less than 1 line (P < .001).

CONCLUSIONS

Use of MYLO CLs reduced axial elongation and myopia progression compared to use of distance single-vision spectacles.

Intraocular Straylight and Multifocal Soft Contact Lens Fit With a Myopia Control Approach

OBJECTIVES

Center-distance multifocal contact lenses (MFCLs) are used to slow myopia progression. We examined the effect of two MFCLs on intraocular straylight values in myopic individuals.

METHODS

Twenty-five young myopic adults were enrolled and were fit with three contact lenses (Biofinity sphere, Biofinity Multifocal, and NaturalVue Multifocal) in a random order over two study visits. Pupil size (NeurOptics VIP-300, Laguna Hills, CA) and contact lens centration were measured. Right eye intraocular straylight measurements were collected (OCULUS C-Quant; Wetzlar, Germany) and compared with a spectacle trial lens. Log straylight (LogSL) values and straylight residuals were analyzed using repeated-measures analyses of variance with Tukey-corrected post hoc t -tests.

RESULTS

The mean participant age (±SD) was 24.1±1.5 years, and right eye spherical equivalent refractive error was -3.38±1.53 DS. There was no difference in mesopic pupil size between visits ( P =0.68) and no difference in contact lens centration between lenses ( P =0.99). LogSL values differed by lens type ( P =0.004). LogSL with the spectacle trial lens was significantly greater than with each contact lens type (all P <0.05), but there were no significant differences in LogSL between the three contact lenses (all P >0.05). There was no difference between the three contact lens designs for straylight residuals ( P =0.33).

CONCLUSIONS

Measured intraocular straylight for both MFCLs was not different than with a spherical soft contact lens. A significant increase in intraocular straylight with spectacle trial lens correction was observed compared with all contact lenses.

Content development for a new item-bank for measuring multifocal contact lens performance

BACKGROUND

Presbyopia is an age-related condition that causes a decreased ability to focus on nearby objects. Multifocal contact lenses are commonly used to address this issue. However, there seems to be a notable dissatisfaction among multifocal contact lens wearers. The absence of a reliable instrument to measure the patient's perspective, despite the widespread use of this method, highlights the need for further research in this area.

OBJECTIVE

The objective of this study is to develop an item-bank integrating all domains necessary to assess the patient's perspective on multifocal contact lens performance, offering a comprehensive measure. The item-bank will ensure a high level of content validity, be self-administered, and will initially be available in Spanish. The aim of this tool is to serve as a valuable resource for research and optometric clinics, facilitating the follow-up of patients with presbyopia who wear multifocal contact lenses or those who are newly starting to use them.

METHODOLOGY

The MCL-PRO item bank, followed a systematic and step-wise inductive approach to gather information, following the recommendations outlined in the COSMIN guidelines and similar studies. The process involved the following steps: (1) Literature review and relevant existing items identification (2) Social media review, (3) Semi-structured focus groups, (4) performing qualitative analysis, (5) refining and revising the items, and (6) generating the content of the item bank.

RESULTS

A total of 575 items were included in the item-bank hosted under 8 different domains that were found to be important for presbyopic population: visual symptoms (213), activity limitation (111), ocular symptoms (135), convenience (36), emotional well-being (33), general symptoms (16), cognitive issues (21) and economic issues (10).

CONCLUSION

The item-bank created has followed standardised methodology for its development and encloses all the aspects for MCL performance evaluation from patients perspective.

Comparison of visual performance and image quality between a myopia-control contact lens and a single-vision contact lens

OBJECTIVE

This study aimed to evaluate the visual performance and image quality of concentric dual-focus-designed contact lenses (CLs) compared with single-vision CLs in myopic Chinese people.

METHODS

Twenty myopic volunteers aged between 18 and 26 years were recruited at a university eye hospital to wear both defocus-incorporated soft contact (DISC) lenses and single-vision CLs for 1 week in random order. High- and low-contrast visual acuity (VA), contrast sensitivity (CS), ocular higher-order aberrations (HOA), Strehl ratio and the Quality of Vision (QoV) questionnaire were assessed with each type of CL at weekly follow-up.

RESULTS

Distance VA was not affected by DISC lenses compared to single-vision CLs in either high (p = 0.414) or low contrast (p = 0.431). However, there was a significant reduction in low-contrast near VA with DISC lenses compared with single-vision CLs (p = 0.011). The differences of CS between DISC lenses and single-vision CLs were significantly associated with lighting conditions and spatial frequencies (F = 128.81, P < 0.001). Compared with single-vision CLs, wavefront aberrations of DISC lenses were significantly increased in total HOA, trefoil, and spherical aberrations for either 3.0 mm or 6.0 mm pupil size. The Strehl ratio wearing DISC lenses reduced significantly compared to the single-vision CLs (p < 0.001) at a pupil diameter of 6.0 mm. QoV scores were higher overall (p = 0.026) and frequency (p = 0.019) with DISC lenses than with single-vision CLs, indicating poorer visual performance.

CONCLUSION

DISC lenses provide satisfactory distance VA. However, the higher scores of the QoV questionnaire with DISC lenses may be related to decreased CS at medium or high spatial frequencies and increased higher-order aberrations.

A comparison of vision-related quality of life between Defocus Incorporated Soft Contact (DISC) lenses and single-vision spectacles in Chinese children

OBJECTIVE

This study aimed to compare the vision-related quality of life (VRQoL) between Defocus Incorporated Soft Contact (DISC) lenses and single-vision spectacles in Chinese children, in order to evaluate their visual performance and subjective acceptance of this bifocal designed contact lenses treatment.

METHODS

Chinese participants aged 7 to 12 years, with myopia of -4.00 to -0.75 D, astigmatism < 1.50 D, and monocular best-corrected visual acuity 0.0 or better, were recruited in the study. All participants had been wearing DISC lenses, or single-vision spectacles, for the last 6 to 18 months and were requested to complete the routine ocular examination and Chinese version of the Pediatric Refractive Error Profile (PREP 2) questionnaire. The questionnaire consisted of 7 scales: vision, symptoms, appearance, activities, handling, peer perception, and overall score. According to their habitual correction modalities, fifty-four children were allocated to the DISC group and 56 to the single-vision spectacles group. A generalized linear model was fitted to assess variables associated with the PREP 2 score.

RESULTS

Participants wearing DISC lenses scored significantly higher than those wearing single-vision spectacles for vision, appearance, activities, peer perception, and overall (all P < 0.05). The improvement of VRQoL in the DISC group was mainly represented in appearance, peer perception, and activities. The quality of life improved more for older participants on scales of vision, symptoms, handling, appearance, and overall score (all P < 0.05). The interaction between treatment and age was statistically significant for the activities scale (P < 0.05).

CONCLUSION

DISC lens wear significantly improves VRQoL in Chinese children compared with single-vision spectacles for most of the survey scales, especially in the areas of appearance, peer perception, and activities. The benefits provided by DISC lenses contribute to greater satisfaction than single-vision spectacles for myopic children.

Wearer Experience and Eye Care Professional Acceptance with a 1 Day Multifocal Contact Lens

Purpose

A large observational survey was undertaken to determine eye care professional (ECP) and patient experience of stenfilcon A multifocal soft contact lens (MyDay multifocal) when prescribed in a real-world setting.

Methods

A total of 196 ECPs from eleven countries fit up to ten presbyopes with stenfilcon A multifocal. Data were collected on fit success at the initial visit, patient satisfaction with comfort, vision at distance, intermediate, and near, overall vision, overall satisfaction, and handling at the initial and follow-up visits after 1-2 weeks of wear. ECPs completed questionnaires on multifocal fitting experience and expectations before and after the fitting period.

Results

A total of 196 pre-fitting and 141 post-fitting ECP surveys were collected. A total of 1505 initial fits (mean age 53.4, range 38 to 81 years, 73% female, 27% neophytes) and 1440 follow-up visits were completed. The mean distance vision contact lens prescription was -1.32DS (range -12.00DS to +8.00DS) with Add powers: Low 56%, Medium 24%, and High 21%. At the follow-up visit 77% (n=1108) of trials were successful. Mean patient satisfaction ratings (1-10 scale, where 1 is not at all satisfied, and 10 extremely satisfied) at the initial visit were higher than eight out of ten for comfort, vision, and overall satisfaction, and were not significantly different after 1-2 weeks of wear. Stenfilcon A multifocal was preferred by 66% of patients over their habitual correction. In most cases mean satisfaction scores and the proportion of patients highly satisfied were not significantly different between myopes and hyperopes, across Add range, between new and habitual wearers, and wearers of frequently replaced and 1 day contact lenses.

Conclusion

ECPs in real-world clinical settings found stenfilcon A multifocal contact lenses easy to fit to a wide range of patients, with a high fit success rate and high levels of patient satisfaction for overall comfort, vision, satisfaction, and handling.

Addressing common myths and misconceptions in soft contact lens practice

Advances in contact lens technology over the past 50 years since the commercialisation of the first soft lenses in 1971 have been incredible, with significant changes in contact lens materials, frequency of replacement, care systems and lens designs occurring. However, despite the widespread availability of contact lenses, penetration rates for those who need vision correction remain in the low single digits and many practitioners seem to hold on to concepts around the potential value of contact lenses that appear based in the dim and distant past and are certainly no longer valid today. This review addresses 10 common 'myths and misconceptions' around soft contact lenses using an evidence-based approach that can hopefully dispel some of these incorrect assumptions.

Visual Performance of Center-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm

PURPOSE

The purpose of this study was to examine the visual performance of center-distance MFCLs in nonpresbyopic adults under different illumination and contrast conditions compared with a single-vision contact lens (SVCL).

METHODS

Twenty-five adult subjects were fit with three different lenses (CooperVision Biofinity D MFCL +2.50 add, Visioneering Technologies NaturalVue MFCL, CooperVision Biofinity sphere). Acuity and reading performance were evaluated.

RESULTS

A statistically significant difference in high-contrast distance acuity was observed (Biofinity, -0.18 ± 0.06; Biofinity MFCL, -0.14 ± 0.08; NaturalVue MFCL, -0.15 ± 0.03; repeated-measures [RM] ANOVA, P = .02). Under mesopic, high-contrast conditions, MFCLs performed worse than SVCLs (Biofinity, -0.05 ± 0.091; Biofinity MFCL, +0.03 ± 0.09; NaturalVue MFCL, +0.05 ± 0.091; RM-ANOVA, P < .0001). Under low-contrast conditions, MFCLs performed one line worse in photopic lighting and two lines worse under mesopic conditions (RM-ANOVA, P < .0001). Glare reduced acuity by 0.5 logMAR for all lenses (RM-ANOVA, P < .001). A statistically significant difference in near acuity was observed (RM-ANOVA, P = .02), but all lenses achieved acuity better than -0.1 logMAR (Biofinity, -0.16 ± 0.06; Biofinity MFCL, -0.17 ± 0.04; NaturalVue MFCL, -0.13 ± 0.08). Reading performance in words per minute (wpm) was worse with MFCLs (Biofinity MFCL, 144 ± 22 wpm; NaturalVue MFCL, 150 ± 28 wpm) than with SVCLs (156 ± 23 wpm; RM-ANOVA, P = .02) regardless of letter size (RM-ANOVA, P = .13). No difference in acuity between the MFCLs was detected (RM-ANOVA: all, P > .05).

CONCLUSIONS

Multifocal contact lenses perform similarly to SVCLs for high-contrast targets and display reduced low-contrast acuity and reading speed. Practitioners should recognize that high-contrast acuity alone does not describe MFCL visual performance.

Bifocal and Multifocal Contact Lenses for Presbyopia and Myopia Control

Bifocal and multifocal optical devices are intended to get images into focus from objects placed at different distances from the observer. Spectacles, contact lenses, and intraocular lenses can meet the requirements to provide such a solution. Contact lenses provide unique characteristics as a platform for implementing bifocality and multifocality. Compared to spectacles, they are closer to the eye, providing a wider field of view, less distortion, and their use is more consistent as they are not so easily removed along the day. In addition, contact lenses are also minimally invasive, can be easily exchangeable, and, therefore, suitable for conditions in which surgical procedures are not indicated. Contact lenses can remain centered with the eye despite eye movements, providing the possibility for simultaneous imaging from different object distances. The main current indications for bifocal and multifocal contact lenses include presbyopia correction in adult population and myopia control in children. Considering the large numbers of potential candidates for optical correction of presbyopia and the demographic trends in myopia, the potential impact of contact lenses for presbyopia and myopia applications is undoubtedly tremendous. However, the ocular characteristics and expectations vary significantly between young and older candidates and impose different challenges in fitting bifocal and multifocal contact lenses for the correction of presbyopia and myopia control. This review presents the recent developments in material platforms, optical designs, simulated visual performance, and the clinical performance assessment of bifocal and multifocal contact lenses for presbyopia correction and/or myopia progression control.

Accuracy, inter-observer and intra-observer reliability in topography assessment of multifocal contact lens centration

PURPOSE

To evaluate the accuracy and reliability (inter and intra-observer) of a method to assess multifocal contact lenses (MCLs) centration using a corneal topography unit.

METHOD

Daily-disposable MCLs (Fusion 1 day Presbyo) were fitted on both eyes of the subjects. For each lens fit a slit lamp digital picture and videokeratograph image were taken in a rapid but randomised sequence. Photo-editing software was used to assess the position of the MCL centre with respect to pupil centre as taken from the slit lamp photograph. The position of the MCL centre was automatically detected as the point of maximum curvature from the videokeratography. Three further manual and qualitative procedures to detect MCL centre, comparing a template of CLs optic zones to the videokeratographic image were performed by 4 practitioners using 3 different algorithms to represent the topographic map. Each manual reading was repeated 3 times.

RESULTS

Twenty-two subjects (11 males) aged 22.8 ± 1.9 years (range 20.8-27.0 years) were recruited. The accuracy of the 4 topographic assessments in determining the centre coordinates of the MCL with respect to SL assessment was good: no differences were found in the left eyes and although in the right eyes a more temporal and superior position of MCLs was determined (paired t-test, p < 0.05) the difference was clinically negligible (0.16 ± 0.36 mm horizontally, 0.23 ± 0.48 vertically). Amongst the 4 practitioners one-way Anova for repeated measures showed no differences for any of the 3 manual assessments. Intra-class correlation coefficient was calculated among the 3 readings for each manual procedure and was very good (between 0.75 and 0.98) in 3 practitioners and moderate (between 0.49 and 0.92) in the fourth.

CONCLUSIONS

The assessment of MCL centration by performing corneal topography over the MCL is an accurate method. Furthermore, inter and intra-practitioner reliability showed by manual procedures appeared very good.

Visual Performance of Daily-disposable Multifocal Soft Contact Lenses: A Randomized, Double-blind Clinical Trial

SIGNIFICANCE

The present study highlights the differences between modern daily-disposable multifocal soft contact lenses to assist eye care practitioners in fitting presbyopic contact lens wearers.

PURPOSE

The purpose of this study was to compare visual performance of three daily-disposable multifocal contact lenses.

METHODS

Presbyopes (n = 72) wore 1-Day Acuvue Moist Multifocal, BioTrue ONEday for Presbyopia, and Dailies AquaComfort Plus Multifocal for 1 week in a prospective, randomized, double-blind, crossover clinical trial. After 1 week, high- and low-contrast visual acuities (HCVA, LCVA) were measured between 6 m and 40 cm and stereopsis at 40 cm. Subjective performance was assessed with 1- to 10-point rating scales for clarity, ghosting, driving vision, vision stability, ease of focusing, overall vision satisfaction, and ocular comfort. Willingness to purchase was reported with categorical responses. Linear mixed models and χ tests were used for analysis, and level of significance was set at 5%.

RESULTS

BioTrue provided better HCVA and LCVA at distance than did Acuvue Moist (P ≤ .03). Subjectively, Acuvue Moist was rated lowest for distance clarity, distance ghosting, and driving vision (P ≤ .05). Acuvue Moist provided better HCVA at 70 to 40 cm and LCVA at 1 m to 40 cm than did BioTrue (P ≤ .01) and better LCVA at 1 m to 50 cm than did AquaComfort Plus (P ≤ .02). AquaComfort Plus also provided better HCVA and LCVA at 50 and 40 cm than did BioTrue (P ≤ .03). Acuvue Moist provided better stereopsis than did BioTrue (P = .02). Subjectively, BioTrue was rated lowest for near clarity (P ≤ .007) and lower than Acuvue Moist for intermediate clarity and near ghosting (P ≤ .04). No other differences were found between lenses (P > .05).

CONCLUSIONS

BioTrue had better distance performance compared with near, whereas Acuvue Moist performed conversely. AquaComfort Plus performed reasonably overall.

Vision Performance and Accommodative/Binocular Function in Children Wearing Prototype Extended Depth-of-Focus Contact Lenses

OBJECTIVE

To assess two prototype contact lenses (CLs) that extend depth of focus through deliberate manipulation of multiple spherical aberration terms (extended depth-of-focus [EDOF]) for visual performance, accommodative and binocular function, and objective static near refraction against a single-vision (SV) CL.

METHOD

This was a prospective, randomized, cross-over, single-masked (participant) clinical trial in which 16 myopic children wore 2 prototype CLs (EDOFL/EDOFH) designed for presbyopes and a SV CL, each for one week. Measurements comprised monocular and binocular high-contrast visual acuity (HCVA: 6 m, 40 cm), binocular low-contrast visual acuity (LCVA: 6 m), contrast sensitivity (CS: 6 m), phorias (3 m, 33 cm), monocular-accommodative facility (33 cm), and objective static refraction (spherical equivalent M) at zero, -3, and -5 D vergences. Measurements were taken 10 min after lens insertion. Subjective response was assessed using take-home questionnaires comprising vision clarity (distance/intermediate/near), vision quality (haloes at night/ghosting), vision stability when moving (playing sport/using stairs), and comfort.

RESULTS

Single vision was significantly better than both EDOF CLs for monocular HCVA, LCVA, and CS (6 m); vision clarity (distance), ghosting (P≤0.040), and EDOFL for binocular HCVA (6 m, P=0.047). M was significantly closer to the ideal objective static refraction at -3 and -5 D vergences (P≤0.004) with both EDOF compared with SV CLs. There were no differences between CLs for any other variable (P≥0.169).

CONCLUSION

Extended depth-of-focus CLs caused minimal disruption to the accommodative and binocular system compared with SV CLs when worn by myopic children. Future EDOF designs for children should reduce the difference between SV for distance vision and vision quality while maintaining the same performance for intermediate and near.

Predicting Short-Term Subjective Vision Performance of Contact Lenses Used in Myopia Control

OBJECTIVE

To investigate whether initial assessment of contact lenses prescribed for myopia control (MC) predicts short-term visual performance.

METHOD

Retrospective analysis of 43 participants in a double-masked, randomized, cross-over trial wearing at least one lens: single-vision (SV) lens (1-DAY ACUVUE MOIST) or MC lenses (MiSight or Proclear Multifocal-Distance +2.00D). Participants completed questionnaires at the fitting visit, a take-home questionnaire (THQ) 3 days after fitting and finally at the assessment visit (≥5 days after fitting). Questions comprised vision clarity and lack of ghosting (distance, intermediate, near at day/night time); vision stability; driving vision; overall vision satisfaction and comfort (1-10 scale, 1-point steps); and willingness to purchase based on vision and MC benefit of lens (yes/no response). Visual acuity was measured at fitting and assessment visits.

RESULTS

Vision clarity (intermediate and near) was significantly worse at assessment compared with fitting while wearing MC lenses (P<0.001), as was overall vision satisfaction (P<0.001), comfort (P<0.001), and vision stability (P=0.001) while wearing either SV or MC lenses. Participants willing to purchase at assessment visit was 84% with SV and 36% with MC lenses, increasing to 88% (SV, P=1.00) and 61% (MC, P<0.001) if the lenses slowed myopia progression. Visual acuity was no different with either MC or SV lenses at fitting or assessment (P≥0.251).

CONCLUSION

Initial performance at fitting did not predict short-term performance for SV or MC lenses. A significant increase in willingness to purchase if lenses slowed myopia progression was observed while wearing MC lenses. Educating patients on the benefits might increase acceptability of MC lenses.

Presbyopia: Effectiveness of correction strategies

Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations, due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states "presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements". Strategies for correcting presbyopia include separate optical devices located in front of the visual system (reading glasses) or a change in the direction of gaze to view through optical zones of different optical powers (bifocal, trifocal or progressive addition spectacle lenses), monovision (with contact lenses, intraocular lenses, laser refractive surgery and corneal collagen shrinkage), simultaneous images (with contact lenses, intraocular lenses and corneal inlays), pinhole depth of focus expansion (with intraocular lenses, corneal inlays and pharmaceuticals), crystalline lens softening (with lasers or pharmaceuticals) or restored dynamics (with 'accommodating' intraocular lenses, scleral expansion techniques and ciliary muscle electrostimulation); these strategies may be applied differently to the two eyes to optimise the range of clear focus for an individual's task requirements and minimise adverse visual effects. However, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is given on presbyopic correction evaluation techniques.

Advances in Carbon Nanotubes-Hydrogel Hybrids in Nanomedicine for Therapeutics

In spite of significant advancement in hydrogel technology, low mechanical strength and lack of electrical conductivity have limited their next-level biomedical applications for skeletal muscles, cardiac and neural cells. Host-guest chemistry based hybrid nanocomposites systems have gained attention as they completely overcome these pitfalls and generate bioscaffolds with tunable electrical and mechanical characteristics. In recent years, carbon nanotube (CNT)-based hybrid hydrogels have emerged as innovative candidates with diverse applications in regenerative medicines, tissue engineering, drug delivery devices, implantable devices, biosensing, and biorobotics. This article is an attempt to recapitulate the advancement in synthesis and characterization of hybrid hydrogels and provide deep insights toward their functioning and success as biomedical devices. The improved comparative performance and biocompatibility of CNT-hydrogels hybrids systems developed for targeted biomedical applications are addressed here. Recent updates toward diverse applications and limitations of CNT hybrid hydrogels is the strength of the review. This will provide a holistic approach toward understanding of CNT-based hydrogels and their applications in nanotheranostics.