Amy L. Sheppard

Clinical evaluation of the Grand Seiko Auto Ref/Keratometer WAM-5500

Purpose:  A clinical evaluation of the Grand Seiko Auto Ref/Keratometer WAM‐5500 (Japan) was performed to evaluate validity and repeatability compared with non‐cycloplegic subjective refraction and Javal–Schiotz keratometry. An investigation into the dynamic recording capabilities of the instrument was also conducted.

Visual outcomes and subjective experience after bilateral implantation of a new diffractive trifocal intraocular lens

Purpose To assess clinical outcomes and subjective experience after bilateral implantation of a diffractive trifocal intraocular lens (IOL). Setting Midland Eye Institute, Solihull, United Kingdom. Design Cohort study. Methods Patients had bilateral implantation of Finevision trifocal IOLs. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), and manifest refraction were measured 2 months postoperatively. Defocus curves were assessed under photopic and mesopic conditions over a range of +1.50 to −4.00 diopters (D) in 0.50 D steps. Contrast sensitivity function was assessed under photopic conditions. Halometry was used to measure the angular size of monocular and binocular photopic scotomas arising from a glare source. Patient satisfaction with uncorrected near vision was assessed using the Near Activity Visual Questionnaire (NAVQ). Results The mean monocular CDVA was 0.08 logMAR ± 0.08 (SD) and the mean binocular CDVA, 0.06 ± 0.08 logMAR. Defocus curve testing showed an extended range of clear vision from +1.00 to −2.50 D defocus, with a significant difference in acuity between photopic conditions and mesopic conditions at −1.50 D defocus only. Photopic contrast sensitivity was significantly better binocularly than monocularly at all spatial frequencies. Halometry showed a glare scotoma of a mean size similar to that in previous studies of multifocal and accommodating IOLs; there were no subjective complaints of dysphotopsia. The mean NAVQ Rasch score for satisfaction with near vision was 15.9 ± 10.7 logits. Conclusions The trifocal IOL implanted binocularly produced good distance visual acuity and near and intermediate visual function. Patients were very satisfied with their uncorrected near vision. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Accommodating intraocular lenses: a review of design concepts, usage and assessment methods

The correction of presbyopia and restoration of true accommodative function to the ageing eye is the focus of much ongoing research and clinical work. A range of accommodating intraocular lenses (AIOLs) implanted during cataract surgery has been developed and they are designed to change either their position or shape in response to ciliary muscle contraction to generate an increase in dioptric power. Two main design concepts exist. First, axial shift concepts rely on anterior axial movement of one or two optics creating accommodative ability. Second, curvature change designs are designed to provide significant amplitudes of accommodation with little physical displacement. Single‐optic devices have been used most widely, although the true accommodative ability provided by forward shift of the optic appears limited and recent findings indicate that alternative factors such as flexing of the optic to alter ocular aberrations may be responsible for the enhanced near vision reported in published studies. Techniques for analysing the performance of AIOLs have not been standardised and clinical studies have reported findings using a wide range of both subjective and objective methods, making it difficult to gauge the success of these implants. There is a need for longitudinal studies using objective methods to assess long‐term performance of AIOLs and to determine if true accommodation is restored by the designs available. While dual‐optic and curvature change IOLs are designed to provide greater amplitudes of accommodation than is possible with single‐optic devices, several of these implants are in the early stages of development and require significant further work before human use is possible. A number of challenges remain and must be addressed before the ultimate goal of restoring youthful levels of accommodation to the presbyopic eye can be achieved.

Three-Dimensional Magnetic Resonance Imaging of the Phakic Crystalline Lens during Accommodation

PURPOSE To quantify changes in crystalline lens curvature, thickness, equatorial diameter, surface area, and volume during accommodation using a novel two-dimensional magnetic resonance imaging (MRI) paradigm to generate a complete three-dimensional crystalline lens surface model. METHODS Nineteen volunteers, aged 19 to 30 years, were recruited. T(2)-weighted MRIs, optimized to show fluid-filled chambers of the eye, were acquired using an eight-channel radio frequency head coil. Twenty-four oblique-axial slices of 0.8 mm thickness, with no interslice gaps, were acquired to visualize the crystalline lens. Three Maltese cross-type accommodative stimuli (at 0.17, 4.0, and 8.0 D) were presented randomly to the subjects in the MRI to examine lenticular changes with accommodation. MRIs were analyzed to generate a three-dimensional surface model. RESULTS During accommodation, mean crystalline lens thickness increased (F = 33.39, P < 0.001), whereas lens equatorial diameter (F = 24.00, P < 0.001) and surface radii both decreased (anterior surface, F = 21.78, P < 0.001; posterior surface, F = 13.81, P < 0.001). Over the same stimulus range, mean crystalline lens surface area decreased (F = 7.04, P < 0.005) with a corresponding increase in lens volume (F = 6.06, P = 0.005). These biometric changes represent a 1.82% decrease and 2.30% increase in crystalline lens surface area and volume, respectively. CONCLUSIONS; The results indicate that the capsular bag undergoes elastic deformation during accommodation, causing reduced surface area, and the observed volumetric changes oppose the theory that the lens is incompressible.

The effect of ageing on in vivo human ciliary muscle morphology and contractility

PURPOSE To assess the effect of ageing on in vivo human ciliary muscle morphology and contractility during accommodation. METHODS Seventy-nine subjects, aged 19-70 years were recruited. High-resolution images were acquired of nasal and temporal ciliary muscle in the relaxed state, and at stimulus vergence levels of -4 and -8 D, using anterior segment optical coherence tomography (AS-OCT). Objective refractions and axial lengths were also recorded. Linear regression analysis was performed to determine the effect of age on nasal and temporal ciliary muscle morphologic characteristics. RESULTS Ciliary muscle anterior length decreased significantly with age both nasally (R = 0.461, P = 0.001) and temporally (R = 0.619, P < 0.001) in emmetropic eyes. In a subset of 37 participants, ciliary muscle maximum width increased significantly with age, by 2.8 μm/year nasally (R = 0.54, P < 0.001) and 3.0 μm/year temporally (R = 0.44, P = 0.007), while the distance from the inner apex of the ciliary muscle to the scleral spur decreased significantly with age on both the nasal and temporal aspects (R = 0.47; P = 0.004 and R = 0.43; P = 0.009, respectively). During accommodation, changes to ciliary muscle thickness and length remained constant throughout life. CONCLUSIONS The human ciliary muscle undergoes age-dependent changes in morphology that suggest an antero-inwards displacement of muscle mass, particularly in emmetropic eyes. However, the morphologic changes observed appear not to affect the ability of the muscle to contract during accommodation, even in established presbyopes, thus supporting a lenticular model of presbyopia development.

In vivo analysis of ciliary muscle morphologic changes with accommodation and axial ametropia

PURPOSE To use anterior segment optical coherence tomography (AS-OCT) to analyze ciliary muscle morphology and changes with accommodation and axial ametropia. METHODS Fifty prepresbyopic volunteers, aged 19 to 34 years were recruited. High-resolution images were acquired of nasal and temporal ciliary muscles in the relaxed state and at stimulus vergence levels of -4 and -8 D. Objective accommodative responses and axial lengths were also recorded. Two-way, mixed-factor analyses of variance (ANOVAs) were used to assess the changes in ciliary muscle parameters with accommodation and determine whether these changes are dependent on the nasal-temporal aspect or axial length, whereas linear regression analysis was used to analyze the relationship between axial length and ciliary muscle length. RESULTS The ciliary muscle was longer (r = 0.34, P = 0.02), but not significantly thicker (F = 2.84, P = 0.06), in eyes with greater axial length. With accommodation, the ciliary muscle showed a contractile shortening (F = 42.9. P < 0.001), particularly anteriorly (F = 177.2, P < 0.001), and a thickening of the anterior portion (F= 46.2, P < 0.001). The ciliary muscle was thicker (F = 17.8, P < 0.001) and showed a greater contractile response on the temporal side. CONCLUSIONS The accommodative changes observed support an anterior, as well as centripetal, contractile shift of ciliary muscle mass.

Clinical outcomes after implantation of a new hydrophobic acrylic toric IOL during routine cataract surgery

Purpose To assess the clinical outcomes after implantation of a new hydrophobic acrylic toric intraocular lens (IOL) to correct preexisting corneal astigmatism in patients having routine cataract surgery. Setting Four hospital eye clinics throughout Europe. Design Cohort study. Methods This study included eyes with at least 0.75 diopter (D) of preexisting corneal astigmatism having routine cataract surgery. Phacoemulsification was performed followed by insertion and alignment of a Tecnis toric IOL. Patients were examined 4 to 8 weeks postoperatively; uncorrected distance visual acuity (UDVA), corrected distance visual acuity, manifest refraction, and keratometry were measured. Individual patient satisfaction with uncorrected vision and the surgeon’s assessment of ease of handling and performance of the IOL were also documented. The cylinder axis of the toric IOL was determined by dilated slitlamp examination. Results The study enrolled 67 eyes of 60 patients. Four to 8 weeks postoperatively, the mean UDVA was 0.15 logMAR ± 0.17 (SD) and the UDVA was 20/40 or better in 88% of eyes. The mean refractive cylinder decreased significantly postoperatively, from −1.91 ± 1.07 D to −0.67 ± 0.54 D. No significant change in keratometric cylinder was observed. The mean absolute IOL misalignment from the intended axis was 3.4 degrees (range 0 to 12 degrees). The good UDVA resulted in high levels of patient satisfaction. Conclusion Implantation of the new toric IOL was an effective, safe, and predictable method to manage corneal astigmatism in patients having routine cataract surgery. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Exploring the optimum step size for defocus curves

Purpose To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified. Setting Midland Eye, Solihull, United Kingdom. Design Evaluation of a technique. Methods Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and −5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear‐focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add‐specific profile (ie, distance, half the near add, and the full near‐add powers). Results A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear‐focus or area metrics for each of the multifocal designs examined when the defocus‐curve step size was increased (P<.05). Conclusion Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Impact of Soft Contact Lens Edge Design and Midperipheral Lens Shape on the Epithelium and Its Indentation With Lens Mobility

PURPOSE To evaluate the influence of soft contact lens midperipheral shape profile and edge design on the apparent epithelial thickness and indentation of the ocular surface with lens movement. METHODS Four soft contact lens designs comprising of two different plano midperipheral shape profiles and two edge designs (chiseled and knife edge) of silicone-hydrogel material were examined in 26 subjects aged 24.7 ± 4.6 years, each worn bilaterally in randomized order. Lens movement was imaged enface on insertion, at 2 and 4 hours with a high-speed, high-resolution camera simultaneous to the cross-section of the edge of the contact lens interaction with the ocular surface captured using optical coherence tomography (OCT) nasally, temporally, and inferiorly. Optical imaging distortions were individually corrected for by imaging the apparent distortion of a glass slide surface by the removed lens. RESULTS Apparent epithelial thickness varied with edge position (P < 0.001). When distortion was corrected for, epithelial indentation decreased with time after insertion (P = 0.010), changed after a blink (P < 0.001), and varied with position on the lens edge (P < 0.001), with the latter being affected by midperipheral lens shape profile and edge design. Horizontal and vertical lens movement did not change with time postinsertion. Vertical motion was affected by midperipheral lens shape profile (P < 0.001) and edge design (P < 0.001). Lens movement was associated with physiologic epithelium thickness for lens midperipheral shape profile and edge designs. CONCLUSIONS Dynamic OCT coupled with high-resolution video demonstrated that soft contact lens movement and image-corrected ocular surface indentation were influenced by both lens edge design and midperipheral lens shape profiles.

Accommodative amplitude required for sustained near work

Citation information: Wolffsohn JS, Sheppard AL, Vakani S & Davies LN. Accommodative amplitude required for sustained near work. Ophthalmic Physiol Opt 2011, 31, 480–486. doi: 10.1111/j.1475‐1313.2011.00847.x