Pantoscopic tilt in spectacle-corrected myopia and its effect on peripheral refraction

Does visual acuity predict visual preference in progressive addition lenses?

PURPOSE

We aimed to determine if visual acuity (VA) could differentiate the quality of vision with two ophthalmic lenses with unwanted astigmatism.

METHODS

Twenty presbyopic subjects (48 to 62 years old; VA better than 0.0 logMAR) graded the magnitude of their preference between two progressive addition lenses (plano addition 2.00D) and their visual acuities were measured with both lenses at various eccentricities from -12 to +12 mm from the near vision point every 3 mm in controlled conditions.

RESULTS

The Lens with the least peripheral astigmatism was preferred by 75% of the subjects. VA measured at the near vision point was statistically worse (p<0.01) with this lens whereas the contrary was observed in the periphery (± 12 and -9 mm of eccentricity). The Friedman test shows that the eccentricity (p<0.001) has a significant effect on visual acuity. However, the lens did not show any significant effect (p=0.76). The choice of the favorite lens was predicted for only 35% when considering central VA (up to 6mm) and 80% of the subjects when considering peripheral VA (9 to 12mm). However, the magnitude of the difference could be predicted by peripheral VA in only 60% of the subjects.

CONCLUSION

High contrast Visual acuity was clearly able to differentiate the 2 lens designs tested in our experiment. However, even under the controlled conditions of this study, it was not possible to predict the quality of vision, as measured by a subjective appreciation, through progressive addition lenses at various eccentricities from the near vision with an addition of 2.0D.

The impact of different corneal refractive surgeries on binocular dynamic visual acuity

Purpose

To investigate the influence of different corneal refractive surgeries on dynamic visual acuity (DVA), and explore its potential influence factors.

Methods

This was a prospective non-randomized study. Adult myopic patients undergoing bilateral laser-assisted sub-epithelial keratomileusis (LASEK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or small incision lenticule extraction (SMILE) with Plano refraction target were enrolled. Uncorrected and corrected distance visual acuity (UDVA/CDVA), manifest refraction and binocular optotype-moving DVA of 40 and 80 degrees per second (dps) were evaluated pre-operatively and post-operatively up to 3 months.

Results

The study included 264 eyes of 132 subjects, with an average age of 27.0 ± 6.7 years, and females accounted for 59% of the participants. Significant improvement was observed at the 3-month visit for 40 dps (SMILE, P = 0.001; LASEK, P = 0.006; FS-LASIK, P = 0.010) and 80 dps (SMILE, P = 0.011; LASEK, P = 0.025; FS-LASIK, P = 0.012) DVA. Adjusting for pre-operative DVA, there was no significant difference in DVA among groups at 3 months post-operatively (P > 0.05 for multiple comparisons). Overall, multiple linear models demonstrated that post-operative DVA at 3 months was correlated with pre-operative DVA (40 dps, β = 0.349, P = 0.001; 80 dps, β = 0.447, P < 0.001), pre-operative spherical equivalent (40 dps, β = 0.311, P = 0.003; 80 dps, β = 0.261, P = 0.009) and post-operative UDVA (40 dps, β = -0.224, P = 0.024; 80 dps, β = -0.188, P = 0.05).

Conclusion

Dynamic visual acuity at 3 months post-operatively of the three corneal refractive surgeries was better than that before the surgery in adult myopic patients, and there was no significant difference among different surgical techniques. Post-operative DVA at 3 months was found correlated with pre-operative DVA, pre-operative SE, and post-operative UDVA. With further improvement, DVA could be a promising functional visual indicator for myopic patients undergoing refractive surgeries.

Measurement and Analysis of Whole-surface Power Distribution in Single Tilted Spectacle Lenses

SIGNIFICANCE

Face-form tilt spectacles are sometimes tilted such that the optical properties of the embedded prescription lenses and the lens power change. If the lens power is not plano, the vision quality of the wearer may be affected.

PURPOSE

This study aimed to measure the whole-surface power distributions of tilted spectacle lenses for different lens powers and tilt angles.

METHODS

Spherical spectacle lenses with a refractive index of 1.56 and powers of -4.00 D, -2.00 D, plano, +2.00 D, and +4.00 D were measured. Their whole-surface power distributions were measured at different tilt angles, up to 20°, using a commercially available Hartmann wavefront aberrometer. The measured data were limited within a 40-mm diameter and analyzed to obtain contour plots of the spherical equivalent (M) and astigmatism (J).

RESULTS

The measured whole-surface power profiles of the nontilted lenses showed both M and J as being symmetrical and increasing outward up to -0.52 and +0.24 D, respectively, for the -4.00 D lens and +0.22 and +0.05 D, respectively, for the +4.00 D lens, corresponding to the spherical design. The profiles of the tilted lenses showed both M and J as unevenly increasing from the center to the peripheral area along the downward tilt direction; however, the plano lens exhibited no effect of tilt on both M and J. The powers at the optical center of the lens increased with tilt angle and lens power. The maximum differences for M and J at a 15° tilt angle in the -4.00 D lens were -2.46 and +1.43 D, respectively. Conversely, at a 17° tilt angle, the maximum differences in the +4.00 D lens were +0.96 D in M and +0.46 D in J.

CONCLUSIONS

Tilt angle and lens power strongly affect the power profiles of tilted spectacle lenses.

Alterations in peripheral refraction with spectacles, soft contact lenses and orthokeratology during near viewing: implications for myopia control

CLINICAL RELEVANCE

The peripheral refraction profile in myopes with different corrective modalities varies significantly for both distance and near viewing and will have implications in managing myopia.

BACKGROUND

This study investigated how the magnitude of peripheral myopic defocus induced by Ortho-K varies with and without accommodation, and how this compares to single vision spectacles and soft-contact-lenses (SCL).

METHODS

Relative peripheral refraction (RPR) of 18 young adults (spherical equivalent -1.00 D to -4.50 D) was determined along the horizontal meridian (±10°, ±20°, ±25°) during distance (3-metres) and near viewing (0.2-metres), and along vertical meridian (±10°, ±15°) for distance viewing alone. Measurements were obtained in an uncorrected state and with single vision spectacles, soft contact lens and Ortho-K. Changes in RPR and astigmatic components were compared between distance and near viewing with all different modalities.

RESULTS

A significant interaction (p = 0.02) between relative peripheral refraction and the target distance (distance and near viewing) was found among different refractive modalities. Single overnight Ortho-K lens wear alone led to relative peripheral myopia for both distance (mean RPR ± SE: -0.92 ± 0.21D and -1.04 ± 0.22D) and near viewing (-0.71 ± 0.17D and -0.76 ± 0.20D). Comparisons of relative peripheral refraction between different corrective modalities at each eccentricity indicated statistical significance of RPR at extreme locations along both temporal and nasal meridian (±20 and ±25°, p < 0.05). RPR with soft contact lenses and spectacles were similar for both distance and near viewing (p > 0.05).

CONCLUSION

Single overnight Ortho-K lens wear alone shifted the RPR in the myopic direction for both distance and near viewing in comparison with single vision spectacles and soft contact lenses. The Ortho-K lens designs that offer a large amount of mid-peripheral corneal steeping, in-turn leading to high relative peripheral myopia for both distance and near viewing and might offer beneficial effects on myopia control.

Comparing sports vision among three groups of soft tennis adolescent athletes: Normal vision, refractive errors with and without correction

BACKGROUND

The effect of correcting static vision on sports vision is still not clear.

AIM

To examine whether sports vision (depth perception [DP], dynamic visual acuity [DVA], eye movement [EM], peripheral vision [PV], and momentary vision [MV],) were different among soft tennis adolescent athletes with normal vision (Group A), with refractive error and corrected with (Group B) and without eyeglasses (Group C).

SETTING AND DESIGN

A cross-section study was conducted. Soft tennis athletes aged 10-13 who played softball tennis for 2-5 years, and who were without any ocular diseases and without visual training for the past 3 months were recruited.

MATERIALS AND METHODS

DPs were measured in an absolute deviation (mm) between a moving rod and fixing rod (approaching at 25 mm/s, receding at 25 mm/s, approaching at 50 mm/s, receding at 50 mm/s) using electric DP tester. A smaller deviation represented better DP. DVA, EM, PV, and MV were measured on a scale from 1 (worse) to 10 (best) using ATHLEVISION software.

STATISTICAL ANALYSIS

Chi-square test and Kruskal-Wallis test was used to compare the data among the three study groups.

RESULTS

A total of 73 athletes (37 in Group A, 8 in Group B, 28 in Group C) were enrolled in this study. All four items of DP showed significant difference among the three study groups (P = 0.0051, 0.0004, 0.0095, 0.0021). PV displayed significant difference among the three study groups (P = 0.0044). There was no significant difference in DVA, EM, and MV among the three study groups.

CONCLUSIONS

Significant better DP and PV were seen among soft tennis adolescent athletes with normal vision than those with refractive error regardless whether they had eyeglasses corrected. On the other hand, DVA, EM, and MV were similar among the three study groups.

Peripheral refraction with eye and head rotation with contact lenses

PURPOSE

To evaluate the impact of eye and head rotation in the measurement of peripheral refraction with an open-field autorefractometer in myopic eyes wearing two different center-distance designs of multifocal contact lenses (MFCLs).

METHODS

Nineteen right eyes from 19 myopic patients (average central M ± SD = -2.67 ± 1.66 D) aged 20-27 years (mean ± SD = 23.2 ± 3.3 years) were evaluated using a Grand-Seiko autorefractometer. Patients were fitted with one multifocal aspheric center-distance contact lens (Biofinity Multifocal D(®)) and with one multi-concentric MFCL (Acuvue Oasys for Presbyopia). Axial and peripheral refraction were evaluated by eye rotation and by head rotation under naked eye condition and with each MFCL fitted randomly and in independent sessions.

RESULTS

For the naked eye, refractive pattern (M, J0 and J45) across the central 60° of the horizontal visual field values did not show significant changes measured by rotating the eye or rotating the head (p > 0.05). Similar results were obtained wearing the Biofinity D, for both testing methods, no obtaining significant differences to M, J0 and J45 values (p > 0.05). For Acuvue Oasys for presbyopia, also no differences were found when comparing measurements obtained by eye and head rotation (p > 0.05). Multivariate analysis did not showed a significant interaction between testing method and lens type neither with measuring locations (MANOVA, p > 0.05). There were significant differences in M and J0 values between naked eyes and each MFCL.

CONCLUSION

Measurements of peripheral refraction by rotating the eye or rotating the head in myopic patients wearing dominant design or multi-concentric multifocal silicone hydrogel contact lens are comparable.

Peripheral refraction with dominant design multifocal contact lenses in young myopes

Purpose

The purpose of this study was to show the potential of a commercial center-distance multifocal soft contact lens to induce relative peripheral myopic defocus in myopic eyes.

Methods

Twenty-eight myopic right eyes from 28 patients (mean age: 22.0 ± 2.0 years) were evaluated. The measurements of axial and off-axis refraction were made using a Grand-Seiko WAM-5500 open-field autorefractometer without lens and with multifocal contact lenses (Proclear Multifocal D^® Design) of +2.00 D and +3.00 D add power applied randomly. Central mean spherical equivalent refraction was −2.24 ± 1.33 D. Ocular refraction was measured at center and at eccentricities between 35° nasal and 35° temporal (in 5° steps).

Results

Baseline relative peripheral refractive error (RPRE) as spherical equivalent (M) was −0.69 ± 1.14 D and −0.46 ± 1.38 D at 35° in the nasal and temporal degrees of visual field, respectively. Both add powers increased the relative peripheral myopic defocus up to −0.82 ± 1.23 D (p = 0.002) and −1.42 ± 1.45 D (p < 0.001) at 35° in the nasal field; and −0.87 ± 1.42 D (p = 0.003) and −2.00 ± 1.48 D (p < 0.001) at 35° in the temporal retina with +2.00 D and +3.00 D add lenses, respectively. Differences between +2.00 and +3.00 D add lenses were statistically significant beyond 20° in the nasal visual field and 10° in the temporal visual field.

Conclusion

It is possible to induce significant changes in the pattern of relative peripheral refraction in the myopic direction with commercially available dominant design multifocal contact lenses. The higher add (+3.00 D) induced an significantly higher effect than the +2.00 D add lens, although an increase of 1 D in add power does not correspond to the same amount of increase in RPRE.

Theoretical analysis of the effect of pupil size, initial myopic level, and optical zone on quality of vision after corneal refractive surgery

PURPOSE

To analyze the theoretical effect that pupil size, optical zone, and initial myopic level have on the final retinal image after corneal refractive surgery.

METHODS

A schematic myopic eye model corrected by the Munnerlyn formula was used to analyze the optical quality of the final retinal image. Root-mean-square radius spot and modulation transfer function were cal- culated by ray tracing to evaluate retinal image quality.

RESULTS

Pupil size had a negative effect on the retinal image only when it was greater than the diameter of the optical zone. In addition, the greater the initial myopic level, the more the pupil size affected image quality. Thus, a clear dependence exists between the initial myopic level and effect that the pupil size can have on the retinal image after laser refractive surgery.

CONCLUSIONS

Pupil size may be a risk factor for night vision disturbances, but only when it is larger than the theoretical optical zones utilized in this study. Its effect depends not only on the optical zone size, but also on the initial "myopic level. Therefore, this relationship should be taken into account during patient selection for refractive surgery

Peripheral myopization using a dominant design multifocal contact lens

Purpose

The purpose of this study was to characterize the central and peripheral refraction across the horizontal meridian of the visual field without and with a multifocal dominant design soft contact lens of different add powers (+1.00 D to +4.00 D) in emmetropic eyes.

Methods

Twenty right eyes from 20 emmetropic patients (mean spherical equivalent central refraction –0.06 ± 0.54 D) with a mean age of 21.6 ± 2.3 years were fitted with Proclear Multifocal dominant design (Coopervision, Pleasanton, CA, USA). Lenses had add powers from +1.00 to +4.00 D in 1.00 D steps. The central and peripheral refraction was measured along the horizontal meridian up to 35° of eccentricity in the nasal and temporal retinal area in 5° steps using a open-field autorefractometer.

Results

Only the +3.00 and +4.00 D add powers generated a significant change in the peripheral refractive pattern compared to central refraction and compared with the no-lens wearing situation. The average myopic increase with these lenses was –3.00 D and –5.00 (p < 0.001) at the margins of inspected nasal and temporal visual field, respectively.

Conclusions

Multifocal dominant design soft contact lenses are able to change the peripheral refractive profile in emmetropic eyes increasing relative peripheral myopia. Lenses with +3.00 D add power seem to be the best option to create such effect due to significant peripheral myopization.

Physical human model eye and methods of its use to analyse optical performance of soft contact lenses

A bench-top physical model eye that closely replicates both anatomical and optical properties of an average human eye was designed and constructed. The cornea was sourced from a flouro-polymer with refractive index (RI) of 1.376 and crystalline lenses were made of Boston RGP polymers, EO and Equalens II, with an equivalent RI of 1.429 and 1.423 respectively. These materials served to make crystalline lens components of different age groups and accommodative states. De-Ionized water, with RI of 1.334 represented both aqueous and vitreous humor. The complementary metal-oxide sensor of a PixelLink digital camera with a resolution of 5MP and a 2.2 microm pixel pitch, hosted on a motor-base, served as the 'acting' retina. The translation and rotary functions of the motor-base facilitated the simulation of different states of ametropia and assessment of peripheral visual function, respectively. We validated one of its configurations to suit normal viewing conditions and results from the on and off-axis optical quality measurements are presented. As a demonstration of potential practical uses, several corrective soft contact lenses were placed on the model eye and their optical performance evaluated.

Peripheral defocus with single-vision spectacle lenses in myopic children

PURPOSE

To determine the impact of wearing single-vision spectacle lenses (SVLs) on the refractive errors at the periphery of the retina in myopic eyes of Chinese children.

METHODS

Twenty-eight children (8 to 15 years) were divided into two groups: one (n = 17) comprising children with low myopia (spherical equivalent between -0.75 D and -3.00 D inclusive) and the other (n = 11), with moderate myopia (spherical equivalent between -3.25 D and -6.00 D inclusive). Cycloplegic autorefraction from right eyes was measured at the fovea and at 20, 30, and 40 degrees in the temporal and nasal visual fields. Measurements were taken on each subject both while uncorrected and while wearing SVLs.

RESULTS

Hyperopic peripheral defocus was found with SVLs in both the low and moderate myopia groups. However, the increase in relative peripheral hyperopic defocus when wearing spectacle correction, when compared with the uncorrected state was statistically significant for the moderate myopia group only. In the moderate myopia group, relative peripheral hyperopic defocus when wearing spectacle correction was statistically significantly greater vs. the low myopia group at 40 degrees in the nasal field and at both 30 and 40 degrees in the temporal field (p < 0.038). An increase in astigmatism with correction was observed for J45 (p < 0.05) was also seen in eyes with moderate myopia, but this was limited to the nasal field.

CONCLUSIONS

Previous investigators have suggested that peripheral hyperopic defocus may play a role in the development and progression of myopia. We have shown that SVLs used to correct myopia can result in increased hyperopic defocus at the peripheral retina in the eyes of Chinese children. The magnitude of this increase tends to escalate with increasing refractive error and eccentricity, especially in cases with moderate levels of myopia.

Effects of myopic spectacle correction and radial refractive gradient spectacles on peripheral refraction

The recent observation that central refractive development might be controlled by the refractive errors in the periphery, also in primates, revived the interest in the peripheral optics of the eye. We optimized an eccentric photorefractor to measure the peripheral refractive error in the vertical pupil meridian over the horizontal visual field (from -45 degrees to 45 degrees ), with and without myopic spectacle correction. Furthermore, a newly designed radial refractive gradient lens (RRG lens) that induces increasing myopia in all radial directions from the center was tested. We found that for the geometry of our measurement setup conventional spectacles induced significant relative hyperopia in the periphery, although its magnitude varied greatly among different spectacle designs and subjects. In contrast, the newly designed RRG lens induced relative peripheral myopia. These results are of interest to analyze the effect that different optical corrections might have on the emmetropization process.

Do Peripheral Refraction and Aberration Profiles Vary with the Type of Myopia? - An Illustration Using a Ray-Tracing Approach

Purpose

Myopia is considered to be the most common refractive error occurring in children and young adults, around the world. Motivated to elucidate how the process of emmetropization is disrupted, potentially causing myopia and its progression, researchers have shown great interest in peripheral refraction. This study assessed the effect of the myopia type, either refractive or axial, on peripheral refraction and aberration profiles.

Methods

Using customized schematic eye models for myopia in a ray tracing algorithm, peripheral aberrations, including the refractive error, were calculated as a function of myopia type.

Results

In all the selected models, hyperopic shifts in the mean spherical equivalent (MSE) component were found whose magnitude seemed to be largely dependent on the field angle. The MSE profiles showed larger hyperopic shifts for the axial type of myopic models than the refractive ones and were evident in -4 and -6 D prescriptions. Additionally, greater levels of astigmatic component (J180) were also seen in axial-length-dependent models, while refractive models showed higher levels of spherical aberration and coma.

Conclusion

This study has indicated that myopic eyes with primarily an axial component may have a greater risk of progression than their refractive counterparts albeit with the same degree of refractive error. This prediction emerges from the presented theoretical ray tracing model and, therefore, requires clinical confirmation.