Optical Zone Diameter Research Articles

The analysis of influencing factors associated with night vision disturbances after implantable contact lens implantation

Objective To investigate the influencing factors of night vision disturbances after implantable contact lens implantation. Methods Fifty eyes of 25 patients who underwent implantable contact lens implantation in both eyes were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires 6 months after surgery. Univariate sample and multiple logistic regression analyses were used to detect influencing factors associated with postoperative night vision disturbances. Potential influencing factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable contact lens optic zone diameter, corneal transverse diameter, sulcus-to-sulcus diameter, and postoperative implantable contact lens vaulting. The power, size, optic zone diameter, and toridity of the implantable contact lens were also included as variables. Results The incidence of night vision disturbances was 34.00% for halos and 26.00% for glare. Halos were found to be significantly related to: (1)The difference between mesopic pupil size and implantable contact lens optic zone diameter (P=0.013); (2)The corneal transverse diameter (P=0.028); (3)The implantable contact lens optic zone diameter (P=0.030). For glare, toricity of the implantable contact lens was revealed as a significant influencing factor (P=0.047). Conclusion Conclusions Possible influencing factors for night vision disturbances include implantable contact lens optic zone diameter, the difference between mesopic pupil size and implantable contact lens optic zone diameter, and the corneal transverse diameter which can cause halos, and the toricity of the implantable contact lens which can cause glare. Key words: Lens, contact, implantable; Vision, night; Eye, phakic

Which ratio of areas improves vision quality in simultaneous focus optics?

To evaluate the impact of the center optical zone diameter (COZD) of center-near bifocal optics on the through-focus subjective quality of vision. Subjective image quality was assessed by 14 young, normally sighted subjects. Computed images of three high-contrast 20/50 letters were generated, across a range of object vergences from +2 diopters (D) to -4 D in 0.25-D steps. The center near optical zone addition power was +2.50 D, and the diameter of this center zone was varied in 10% steps to cover from 0% (single vision distance) to 90% of the 4.5-mm pupil diameter. Subjects rated image clarity of these computed images on a 0 to 5 scale, through a 3-mm pupil to limit the effect of their own aberrations. To quantify the efficiency of bifocal optics, we calculated the area under the through-focus subjective quality of vision curve. A criterion higher than 2 was judged to be an acceptable level of quality of vision, normalized by the naked eye condition. The average benefit of the optical profiles is highly subject dependent (i.e., from 0.8 to 1.9), potentially explaining why some subjects are not satisfied with simultaneous vision multifocal corrections. Averaged across subjects, the best benefit (i.e., 1.42) was obtained with a COZD covering 40% of the pupil area, whereas the 20, 30, and 50% profiles provide slightly lower benefit (i.e., ∼1.35). A COZD covering 20% of the pupil area equalized distance and near quality of vision. Quality of vision with bifocal optics is highly subject dependent. Peripheral rays do not seem to play an important role in the through-focus quality of vision, as the central pupil area is more heavily weighted in determining subjective image quality.

The treatment for capsular contraction syndrome

Objective To investigate the treatment method for capsule contraction syndrome after cataract phacoemulsification. Methods A series of 19 eyes of 19 cases with capsule contraction syndrome after cataract phacoemulsification were investigated. Patients in incipient and progressive stage of capsule contraction syndrome were treated by Nd: YAG laser anterior capsulotomy, and severe ones were treated by capsulolysis. The postoperative best corrected visual acuity, anterior chamber reaction, anterior capsule status, location of IOL and intraocular pressure(IOP) were observed during following up period of 1 to 6 months. Results The best corrected visual acuity after operation were significantly improved in all cases comparing with that before the operation, and the difference was statistically significant(P 0.05). The difference of IOP between postoperative 1 month and 6 month was not statistically significant either(P>0.05); The difference of postoperative IOP between Nd: YAG laser anterior capsulotomy and anterior capsulolysis was not statistically significant (P>0.05). The diameter of anterior capsular optical zone ranged from 5.5 to 6 mm. All intraocular lens situated within the capsular bag without decentration or tilt. Anterior chamber reaction was mild. No capsular rupture, zonule tears or other severe complication were observed. Conclusion Nd: YAG laser anterior capsulotomy and capsulolysis are safe and effective for the treatment of capsule contraction syndrome. Nd: YAG laser anterior capsulotomy is suitable for the treatment of incipient and progressive stage of capsule contraction syndrome. The capsulolysis is suitable for the treatment of severe capsule contraction syndrome. Key words: Syndrome, contraction, capsule; Capsulotomy, anterior, Nd: YAG laser; Capsulolysis

Causes of increased corneal aspherical index following LASIK for myopia

Background Laser assisted in situ keratomileusis (LASIK) for myopia will change corneal asphericity and further affect the quality of vision.However,how operating parameters such as ablation depth and optic zone diameter affect corneal asphericity is still rarely reported.Objective Aim of this study was to investigate the influence of corneal ablation depth and optic zone diameter on corneal asphericity after LASIK for myopia.Methods This prospective study comprised 175 eyes of 89 patients with the spherical equivalent of (-5.93± 1.98)D and the best corrected visual acuity (BCVA) ≥ 1.0.The flap creation with the femtosecond laser combine iris recognize guided LASIK was performed on the patients who were available for the evaluation at postoperative 6 months.Corneal aspherical index (Q value) at the central corneal 6.0 mm were measured with Orbscan IIz-corneal topography before and 6 months after operation.Corneal ablation depth and optic zone diameter were recorded in operation.The changes of visual acuity and spherical equivalent before and after surgery were compared by self-control method,and the correlations between corneal ablation depth or optic zone diameter with alteration of Q value (AQ) after LASIK were assessed using multiple regression analysis.Results The mean spherical power,cylinder diopter and spherical equivalent were (-5.57 ± 1.89) D,(-0.71 ±0.55) D and (-5.93 ± 1.98) D before surgery,and those after surgery were (-0.25 ±0.30),(-0.14±0.22)D and (-0.32±0.37)D,showing significant differences between before and 6 months after LASIK (t=-32.39,-23.91,-35.18,all at P＜0.01).The Q values at the central corneal 6.0 mm were -0.13 ± 0.09 (-0.47-0.08) in preoperation and 1.09 ± 0.54 (0.22-2.51) in postoperation,with a significant increase in postoperation (t=29.37,P＜0.01).Corneal ablation depth was (95±28) μm and optic zone diameter was (6.32±0.26)mm.Ablation depth appeared to be positive correlation with AQ (β =0.803),and optic zone diameter showed a negative correlation with AQ (β =-0.149),with a multiple regression formula AQ =1.517+0.015×ablation depth-0.3 ×optic zone diameter.Conclusions LASIK for myopia increase corneal Q value.The increase of corneal ablation depth and decrease of optic zone diameter contribute to enlargement of corneal Q value. Key words: Keratomileusis, Laser in situ; Cornea/surgery; Myopia/surgery; Prospective study; Corneal topography; Corneal aspherical index; Ablation depth; Optic zone

Can Manipulation of Orthokeratology Lens Parameters Modify Peripheral Refraction?

To investigate changes in peripheral refraction, corneal topography, and aberrations induced by changes in orthokeratology (OK) lens parameters in myopes. Subjects were fitted with standard OK lenses that were worn overnight for 2 weeks. Peripheral refraction, corneal topography, and corneal surface aberrations were measured at baseline and after 14 nights of OK lens wear. Subsequent to a 2-week washout period, subjects were refitted with another set of lenses where one eye was randomly assigned to wear an OK lens with a smaller optic zone diameter (OZD) and the other eye with a steeper peripheral tangent. Measurements were taken again at a second baseline and after 14 days of overnight wear of the second OK lens set. Standard OK lenses with a 6-mm OZD and 1/4 peripheral tangent caused significant changes in both peripheral refraction and corneal topography. Significant hyperopic shift occurred in the central visual field (VF) while a myopic shift was found at 35 degrees in the nasal VF. OK induced significant reductions in corneal power at all positions along the horizontal corneal chord except at 2.4 mm nasal where there was no significant change and at 2.8 mm nasal where there was an increase in corneal refractive power. A positive shift in spherical aberration was induced for all investigated lens designs except for the 1/2 tangent design when calculated over a 4-mm pupil. Reducing OZD and steepening the peripheral tangent did not cause significant changes in peripheral refraction or corneal topography profiles across the horizontal meridian. OK lenses caused significant changes in peripheral refraction, corneal topography, and corneal surface aberrations. Modifying OZD and peripheral tangent made no significant difference to the peripheral refraction or corneal topography profile. Attempting to customize refraction and topography changes through manipulation of OK lens parameters appears to be a difficult task.

Risk Factors Associated With Night Vision Disturbances After Phakic Intraocular Lens Implantation

To investigate the incidence and severity of night vision disturbances after implantable collamer lens surgery and to analyze the risk factors. Retrospective, noncomparative study. Medical charts from 50 eyes of 25 patients who underwent implantable collamer lens implantation were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires administered 6 months after surgery. Univariate simple and multiple logistic regression analyses were used to detect risk factors associated with postoperative night vision disturbances. Potential risk factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, white-to-white diameter, sulcus-to-sulcus diameter, and postoperative implantable collamer lens vaulting. The power, size, optic zone diameter, and toricity of the implantable collamer lens were also included as variables. The incidence of night vision disturbances was 34.0% for halos and 26.0% for glare. Halos were found to be significantly related to the difference between mesopic pupil size and implantable collamer lens optic zone diameter (P = .013), white-to-white diameter of the cornea (P = .028), and implantable collamer lens optic zone diameter (P = .030). For glare, toricity of the implantable collamer lens was revealed as a significant risk factor (P = .047). Although not severe, the incidence of night vision disturbances after implantable collamer lens implantation was not negligible. Possible risk factors for night vision disturbances include implantable collamer lens optic zone diameter, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, and white-to-white diameter of the cornea for causing halos, and the toricity of the implantable collamer lens for causing glare.

Small optical zones with aspheric profiles in laser refractive surgery for myopia: A surgical outcome and patient satisfaction study

To assess the outcomes of small optical zone (OZ) ablations used in conjunction with large transition zones (TZ) and a highly aspheric treatment profile. Interventional case series of 39 consecutive patients with myopia or myopic astigmatism. Patient data included pre and postoperative refraction and visual acuities, laser treatment settings and pre and postoperative corneal topography as well as questionnaire responses about the use of glasses and the quality of vision postoperatively. The mean preoperative spherical equivalent was -4.50±2.11 dioptres (D) and the mean OZ and TZ diameters were 4.5±0.5mm and 8.1±0.4mm, respectively. The mean patient age was 40.7±10.4 years. Manifest spherical refraction was within ±0.5D in 87% of patients (±1.0D in 99%) and cylindrical refraction within 0.5D in 79% (≤1.0D in 95%). The need to wear distance glasses postoperatively was associated with dissatisfaction with the quality of daytime vision (p=0.05) and unhappiness with night vision was associated with symptoms of halos (p=0.03) and starbursts (p=0.02). The proportion of patients reporting symptoms of dysphotopsias included: ghosting 0%; glare 2%; halos 10%; and starbursts 15%. There was a significant difference in the measured mean effective OZ diameter (4.8±0.3mm) compared to the mean programmed OZ (4.5±0.5mm, p=0.00). Small ablation zones, when used in conjunction with a large diameter TZ, do not lead to a greater incidence of unwanted visual phenomena over that reported by many studies with larger OZs.

A Contralateral, Randomized Comparison of Optimized Prolate Ablation and Conventional LASIK for Myopia With the NIDEK Excimer Laser Platform

To compare the refractive, visual acuity, topographic, and spherical aberration outcomes of LASIK using the Quest excimer laser platform with the optimized prolate ablation (OPA) profile (NIDEK Co Ltd) in one eye and conventional ablation profile in the fellow eye of the same patient. Thirty-seven myopic patients underwent LASIK bilaterally, with one eye randomized to receive OPA ablation (-3.88±1.42 diopters [D], range: -1.53 to -7.50 D) and the fellow eye to receive conventional ablation (-3.89±1.37 D, range: -1.75 to -7.00 D). Independent and paired t tests were used for testing differences between groups at last postoperative follow-up (6 or 12 months). Postoperatively, 97% (32/33) of OPA eyes and 94% (31/33) of conventional eyes saw 20/20 or better without correction (P>.05). No eyes lost 2 or more lines of distance corrected visual acuity. Manifest refraction spherical equivalent was -0.16 D in the OPA group and -0.05 D in the conventional group (P>.05). Ocular spherical aberration was -0.003 μm in the OPA group and +0.102 μm in the conventional group (P<.05). Corneal asphericity was statistically lower after OPA (0.07±0.26) compared to conventional ablation (0.30±0.26) (P<.001). The mean programmed optical zone and achieved postoperative horizontal diameter of the effective optical zone were statistically significantly larger in the OPA group (P<.05). Postoperative visual acuity and refractive outcomes were similar between groups. Laser in situ keratomileusis using the OPA profile for the correction of myopia induced significantly less corneal and ocular spherical aberration, resulted in normal postoperative asphericity in 94% of eyes, and larger horizontal diameter of the effective optical zone compared to the conventional profile.

Satisfaction Level of Physicians Who Have Undergone Corneal Refractive Surgery

PurposeTo evaluate the levels of satisfaction among physicians who have undergone corneal refractive surgery.MethodsThis study included 212 eyes of 107 consecutive patients who underwent laser in situ keratomileusis or laser sub-epithelial keratomileusis surgery. Patients were divided into two groups: one group of physicians and one group of other healthcare workers (HCWs). The physicians' group was also subdivided into two different groups: surgeons or doctors using microscopes and medical physicians. The main outcome measures were scale scores obtained by using the Visual Function Index-14 questionnaires; uncorrected distance visual acuity (UDVA), residual spherical equivalent (SE), optical zone diameter, and residual corneal thickness were also compared between the groups.ResultsNo significant differences in preoperative parameters, with the exception of the ratio of types of refractive surgery, were noted between the physicians and the HCWs group. Additionally, no differences between the groups were noted in the postoperative UDVA, residual SE, optical zone diameter, residual corneal thickness, and level of satisfaction. When comparing the two subgroups of physicians, the differences in satisfaction rates were not statistically significant, even in terms of the performance of delicate manual work.ConclusionsNo statistically significant differences in the clinical outcomes and satisfaction scores were detected after surgery between the physicians and HCWs groups, nor were any significant differences detected between the surgeons and medical physicians groups. Corneal refractive surgery can conceivably be recommended even for physicians who perform intensive near vision-dependent activities and delicate operations.

The Effect of Two-Zone Concentric Bifocal Spectacle Lenses on Refractive Error Development and Eye Growth in Young Chicks

To characterize the effects on refractive error development and eye growth in young chicks of two-zone concentric lens designs, which differentially affect the defocus experiences of central and peripheral retinal regions. Monocular defocusing lenses were worn for 5 days from 17 days of age. Four two-zone concentric lens designs (overall optical zone diameter, 10 mm) combining plano with either -5- or +5-D power were used. Lens designs were as follows: (1) +5 D center (+5C), (2) +5 D periphery (+5P), (3) -5 D center (-5C), and (4) -5 D peripheral (-5P), with plano in periphery for all C-designs and in the center for P-designs. Five central zone diameters (CZDs) were tested, ranging from 2.5 to 6.5 mm in 1-mm increments. Plano, +5- and -5-D single-vision (SV) lenses were used as the control. A minimum of six birds were included in each lens group. For the two-zone lenses, the P designs (i.e., peripheral defocus) had greater effects than the C designs (i.e., central defocus) on both on-axis eye growth and refractions. All but the 6.5-mm CZD +5P lens induced larger changes than the +5SV lens. The +5C lenses with CZD less than 5.5 mm had little effect. The two-zone -5-D lenses had less effect than the -5SV lens, and only the 6.5-mm CZD lens of the -5C series had a significant effect. The results demonstrate that peripheral defocus can influence both peripheral and central refractive development. The inhibitory effect on axial eye growth of the +5P lenses opens the possibility that appropriately designed concentric lenses may control the progression of human myopia.

Predictability and stability of refraction with increasing optical zone diameter in hyperopic LASIK

We undertook a prospective nonrandomized study to assess refractive outcome and patient satisfaction with hyperopic laser in situ keratomileusis (LASIK) using variable optical zone diameters in correction of hyperopia of more than 4.00 diopters. Fourteen adults (comprising 28 hyperopic eyes) underwent hyperopic LASIK correction for hyperopia of more than 4.00 diopters. The sample was divided into two groups. Group 1 included the right eyes of the 14 patients who underwent hyperopic LASIK using a 6.5 mm optical zone diameter. Group 2 comprised the left eyes of the same patients with the only difference being that the optical zone diameter was 6.0 mm. The mean age of the patients was 36.42 +/- 5.10 years. Group 1 eyes had a median (range) preoperative uncorrected visual acuity (UCVA) of 0.79 (0.52) and best-corrected visual acuity (BCVA) of 0.15 (0.08). Group 2 had a median preoperative UCVA of 0.79 (0.60) and BCVA of 0.15 (0.08). The median postoperative UCVA in Group 1 was 0.17 (0.21) and BCVA was 0.15 (0.13). In Group 2, the median postoperative UCVA was 0.30 (0.32) and BCVA was 0.15 (0.26). Group 1 had a median preoperative refraction of +5.37 (1.75) diopters and the median postoperative refraction at one week was -0.23 (1.25) diopters, at three months was +0.75 (0.75) diopters, and at six months was +0.75 (1.00) diopters. Group 2 had a median preoperative refraction of +5.00 (1.75) diopters, and the median postoperative refraction at one week was +0.13 (1.5) diopters, at three months was +1.00 (0.75) diopters and at six months +1.25 (1.25) diopters. The difference was statistically significant between groups 1 and 2. The difference within each group was also significant. Group 1 eyes were stabilizing after the three-month period in contrast with Group 2 in which the refractive changes continued throughout the follow-up period. Larger optical zone diameter in correction of hyperopia of more than 4.00 diopters was more predictable, stable and safe.

The use of video-keratoscopy in predicting contact lens parameters for keratoconic fitting

The purpose of this report is to demonstrate the use the video-keratoscope in determining the type and size of the cone in keratoconus and PMD patients and the final back optic zone diameter (BOZD) and total lens diameter (LD). A retrospective review of one hundred clinical records including topographic maps, of keratoconic patients (randomly selected) was performed. Cone diameter and type and final contact lens base curve and diameter were recorded. The types or variations of keratoconus were determined with the use of the tangential map to be either: centred or nipple, early oval cones, moderate oval cones, severe cones or pellucid marginal degeneration (PMD). The size of the cone was dependent on the type and the stage of progression of the cone. Inventory sets for keratoconus that had progressively smaller BOZDs as the base curve or back optic zone radius (BOZR) steepened were found to fit best when prescribed for centred or nipple cones. Inventory sets or multicurve sets that had a constant BOZD with a certain lens diameter that did not vary with the BOZR were found to perform better on oval cones. Very large cones, as with PMD benefited from lenses with very large BOZDs. Matching the size of the BOZD (and in tandem the LD) to the size of the cone as determined with the tangential topographic map may be a useful tool in aiding in contact lens fitting to increase success.

Clinical studies on Q-factor guided LASIK for the correction of myopic astigmatism

To compare the results of the Q-factor guided LASIK with the conventional LASIK for the correction of myopic astigmatism. Forty-three eyes underwent Q-factor guided LASIK and 41 eyes were received conventional LASIK. The patients were followed up for more than 3 months . Examinations included refraction, distance and near vision, noncontact tonometer, topography (provide Q value), aberrometer, ultrasonic pachymetry, contrast sensitivity function. At 3 months, 97.67% of Q-factor guided LASIK eyes attained UNCVA 1.0 or better and 97.56% eyes in the control group. The mean postoperative SE for Q-factor guided LASIK group was (-0.19 +/- 0.20) diopters (D) at 3 months and (- 0.17 +/- 0.17) diopters (D) in conventional LASIK group. The postoperative Q value of Q-factor guided LASIK was (0.50 +/- 0.28) and (0.82 +/- 0.40) in the conventional LASIK group, significant difference was noted between two groups. Both Q-factor guided LASIK and conventional LASIK significantly increased spherical aberration, the mean RMS of postoperative spherical aberration were (-0.265 +/- 0.156) microm, (-0.487 +/- 0.159) microm respectively, significant difference were noted between two groups at 3 months . Contrast sensitivity was reduced at 1 week and restored at 1 month postoperatively in Q-factor guided LASIK, while in conventional LASIK it was reduced at 1 week, 1 month and restored at 3 months. Corneal topography revealed in Q-factor guided LASIK the diameter of effective optical zone (EOZ) was (5.74 +/- 0.22) mm. However postoperative EOZ of conventional LASIK was (5.34 +/- 0.29) mm in control group. Q-factor guided LASIK is effective, safe and predictable for correction of myopic astigmatism. The postoperative visual quality of Q-factor guided LASIK is better than that of conventional LASIK due to its superiority for correction of spherical aberration.

Rigid gas permeable lens tolerance limits and their possible effect on mode of fit

Background: Rigid gas permeable corneal lenses should be manufactured according to the tolerance limits specified in the International Standard ISO 18369‐2: 2006. The purpose of this study was to model and quantify the central and edge fit provided by lenses with manufacturing errors that are at the limits of these dimensional tolerances.Methods: A spreadsheet was used to design a tri‐curve lens that provided specified values for apical tear layer thickness and axial edge clearance on corneas with three different apical radii and six different p values. The lens radii and diameters were then varied by amounts that were at the limit of the corresponding tolerances to ascertain the resultant central and edge fit of the lens.Results: Rigid gas permeable lenses made with manufacturing errors at the limits of tolerances in either the back optic zone radius (BOZR) or back optic zone diameter (BOZD) are unlikely to provide an acceptable apical tear layer thickness. When the BOZR is 0.05-mm steep and the BOZD is 0.20-mm large, a lens intended to have an apical tear layer thickness (ATLT) of 5 µm will provide an actual value between 12.3 and 19.4 µm, depending on corneal radius and shape. When the BOZR is 0.05-mm flat and the BOZD is 0.20-mm small, the value of ATLT will be zero. Lenses in which all radii and diameters have been made with such errors may allow a clinically acceptable edge clearance in most cases.Conclusion: Current tolerance limits for RGP lenses may allow the ATLT to differ significantly from that intended but the edge fit may be acceptable.While the full specifications of a RGP lens should be verified prior to its supply to a patient, it is particularly important to measure the BOZR and desirable to measure the BOZD, to ensure that resultant ATLT does not differ significantly from that intended. Minimally blended transitions, especially on trial lenses, should allow the back surface dimensions to be measured in accordance with International Standard ISO 18369‐3: 2006. Ideally, the practitioner should be aware of any differences between nominal and actual specifications of both trial lenses and those supplied to patients.

Photopic pupillometry–guided laser in situ keratomileusis for hyperopic presbyopia

To evaluate a method of surgically treating presbyopia in hyperopic patients having laser in situ keratomileusis (LASIK) by selecting excimer ablation optical zone diameters based on the photopic pupil. Private practice, Beverly Hills, California, USA. This prospective analysis comprised 46 patients having hyperopic LASIK for presbyopia. The distance-dominant eye was treated with a standard 6.0 mm optical and 9.0 mm outer zone for full distance correction with no nomogram adjustment from the final preoperative manifest refraction. In the nondominant eye, an algorithm was used to select the optical and blend zone diameters and the optical zone size-dependent programmed amount of correction augmentation. Variables evaluated at the 6-month postoperative visit included preoperative and postoperative manifest refractive spherical equivalent (MRSE), refractive cylinder, and monocular and binocular near and distance uncorrected visual acuities. Patient satisfaction and spectacle dependence were also evaluated. In the near-corrected eye, the mean preoperative and postoperative MRSE was +1.10 diopters (D) +/- 1.20 (SD) and -1.30 +/- 0.56 D, respectively, and the mean refractive cylinder, -0.76 +/- 0.91 D and -0.36 +/- 0.33 D, respectively (P<.05). The mean uncorrected near acuity in the near-corrected eye was J10 preoperatively and J1 postoperatively (P<.0001) and the binocular mean uncorrected near acuity, J10 and J1, respectively (P<.0001). The mean uncorrected logMAR distance acuity in the near-corrected eye was +0.38 +/- 0.31 (20/50) preoperatively and +0.36 +/- 0.25 (20/50) postoperatively (P>.05). The mean binocular uncorrected logMAR distance acuity was +0.30 +/- 0.30 (20/40) and +0.01 +/- 0.08 (20/20) (P<.0001), respectively. The mean overall patient satisfaction score was 8.8 (scale 1 to 10). After LASIK, no patient reported using spectacles full time for near or distance and 15% reported part-time use. Photopic pupillometry-guided LASIK may be an effective option when considering surgical treatment of presbyopia in hyperopic patients.

Comparison of two pupillometers in determining pupil size for refractive surgery

To compare a handheld and a digital pupillometer in determining pupil size in a population of refractive surgery candidates (group 1) and after implantation of an Artisan phakic intraocular lens (PIOL) for correction of myopia (group 2). Pupil size was measured with the Colvard and Procyon pupillometers in 121 eyes in group 1 and 83 eyes in group 2. Pupil sizes measured with the Colvard device were compared with the scotopic, mesopic-low and mesopic-high measurements taken with the Procyon pupillometer in both groups. Analysis of comparison between pupil measurements was performed according to methods described by Bland and Altman. The mean Colvard scotopic pupil diameter, scotopic, mesopic-low and mesopic-high Procyon pupil diameters were 5.86 +/- 0.81 mm, 6.42 +/- 0.88 mm, 5.55 +/- 0.95 mm and 4.21 +/- 0.73 mm in group 1 and 5.32 +/- 0.67 mm, 6.14 +/- 0.81 mm, 5.33 +/- 0.78 mm and 4.02 +/- 0.55 mm in group 2, respectively. The Colvard diameter compared most favourably with the Procyon mesopic-low diameter (group 2; p = 0.78). Measurements of pupil diameter with the Colvard pupillometer correlated best with measurements taken by the Procyon pupillometer under standardized mesopic-low light conditions. We believe that digital binocular infrared pupillometry is advantageous for obtaining standardized measurements of pupil size.

Factors affecting the change in lower-order and higher-order aberrations after wavefront-guided laser in situ keratomileusis for myopia with the Zyoptix 3.1 system

To identify factors that affect the change in lower- and higher-order wavefront aberrations after myopic wavefront-guided laser in situ keratomileusis (wg-LASIK). Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Sixty myopic eyes of 32 patients were treated with wg-LASIK (Zyoptix version 3.1, Bausch & Lomb) and had an uneventful follow-up of 12 months. Wavefront errors were measured preoperatively and 12 months after LASIK and were computed for pupil diameters (PDs) of 3.5 mm and 6.0 mm. Multiple stepwise regression analysis was performed to assess the influence of patient age, spherical equivalent (SE), sphere, cylinder, optical zone (OZ) diameter, and the preoperative individual Zernike coefficients on lower- and higher-order aberration (HOA) change. The mean preoperative SE was -5.59 diopters (D) +/- 2.20 (SD) (range -1.00 to -9.50 D); the mean OZ diameter was 6.70 +/- 0.68 mm (range 5.6 to 8.1 mm). Reduction in almost all Zernike coefficients was influenced significantly by the preoperative amount of the individual coefficient. The effect varied among the coefficients and was lower with the 6.0 mm PD. With the 3.5 mm PD, age, SE, sphere, cylinder, and OZ diameter did not have a significant effect on individual Zernike coefficients. With the 6.0 mm PD, SE and OZ diameter had a significant effect on the induction of Z4(0); the OZ diameter also had an effect on the induction of coma root mean square. Three groups of factors influenced the change in HOAs: The negative correlation with the magnitude of preoperative HOA values reflected the effect of the wavefront-guided algorithm. The SE and OZ diameter affected the inadvertent induction of spherical aberrations. Randomly acting effects such as decentration or flap creation, which were not included in the model, affected the induction of HOAs, particularly coma-like terms.

Changes of higher-order aberrations after LASIK surgery for myopia

目的 分析LASIK手术对高阶像差的影响,分析LASIK术前近视屈光度与LASIK术后眼的高阶像差的关系.方法采用WASCA波前像差仪测量150眼LASIK术前及术后1月及3月瞳孔直径分别为小瞳孔(3 mm)及大瞳孔(6.25mm)时的总高阶像差的均方根及第三和第四阶像差的Zernike系数,并计算出球差、慧差、第三及第四阶像差的均方根.对结果进行方差分析和直线相关分析.结果 LASIK术后,大瞳孔直径和小瞳孔直径下高阶像差均明显增高.无论瞳孔大小,术后3月较1月时高阶像差均轻微下降.大瞳孔直径下,光区直径为6.25mm时,术后球差、第四阶像差和总高阶像差与术前屈光度存在正相关.结论 LASIK术后,高阶像差明显增高,尤以球差最明显.术前屈光度越高,手术所导致的高阶像差也越大,屈光度过高的近视眼不宜采用波前像差引导的个体化屈光手术。

Influence of pupil and optical zone diameter on higher-order aberrations after wavefront-guided myopic LASIK

To investigate the influence of pupil and optical zone (OZ) diameter on higher-order aberrations (HOAs) after myopic wavefront-guided laser in situ keratomileusis (LASIK). Twenty-seven myopic eyes of 19 patients were included. The mean preoperative spherical equivalent was -6.86 diopters (D) +/- 1.24 (SD) (range -4.25 to -9.5 D); the mean planned OZ diameter was 6.26 +/- 0.45 mm (range 5.7 to 7.1 mm). All patients had uneventful wavefront-guided LASIK (Zyoptix version 3.1, Bausch & Lomb) and an uncomplicated follow-up of 12 months. Wavefront measurements were performed with a Hartmann-Shack sensor in maximum mydriasis preoperatively and 12 months after LASIK. Wavefront errors were computed for pupil diameters (PDs) of 3.0, 3.5, 4.0, 5.0, 6.0, and 7.0 mm for the individual OZ diameter and for the individual mydriatic PD (7.93 +/- 0.46 mm). The impact of the relationship between pupil diameter and OZ diameter (fractional clearance [FC]) on HOA was described and quantified using curvilinear regression with a 4th-order polynomial fit. There was a reproducible relationship between FC and the amount of induced HOA. The change in HOA root mean square and primary spherical aberration (Z(4)0) was significantly correlated with FC. If the OZ was 16.5% larger than the pupil (FC = 1.17), only half the amount of HOA was expected to be induced than if the OZ equaled the pupil. In contrast, an OZ that was 9% smaller than the pupil (FC = 0.91) resulted in an HOA induction 50% higher than at FC = 1. The OZ zone to pupil ratio (fractional clearance) had a significant impact on HOA induction after wavefront-guided LASIK.

Effective corneal refractive diameter as a function of the object tangent angle in visual space

To determine whether the currently accepted method of selecting a minimum optical zone diameter for laser refractive surgery that is equal to or slightly greater than the dark-adapted pupil diameter provides a sufficient diameter of corneal surface to focus light arising from objects in the paracentral and peripheral visual field. Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA. An optical model of the anterior segment was developed to calculate the effective corneal refractive diameter (ECRD), which is the diameter of the area of cornea that refracts all incident light rays arising from an object through the physical pupil (PP). This model incorporates the patient variables of central anterior chamber depth (ACD), central corneal curvature (K(c)), and the diameter of the apparent entrance pupil (EP). The model was expanded to incorporate distant objects off the line of sight (LOS), described by their angular displacement from the fixation object in visual space (the object tangent angle delta(ob)). Results were calculated for the 360 meridian degree visual field (ie, for all objects in visual space perceptually displaced from the fixation object by angle delta(ob)). The effect of the prolate nature of the cornea was also investigated. The ECRD expanded rapidly as a function of PP and delta(ob) but was minimally influenced by K(c). Beyond a critical object tangent angle delta(c), light rays striking the corneal vertex were not refracted through the PP, and the ECRD became an annular surface centered on the corneal vertex. The delta(c) was not a function of K, but increased as the PP increased and decreased as the ACD increased. The prolate nature of the cornea had little influence on the ECRD, even for very peripheral light rays. The ECRD expands rapidly when considering distant objects only slightly displaced from the LOS. A patient treated with an optical zone equal to or slightly greater than the dark-adapted pupil diameter may experience vision quality loss for paracentral and midperipheral objects even under conditions of ambient indoor lighting.