P. Sarita Soni

Overnight orthokeratology: visual and corneal changes.

Purpose. To achieve an optimal fit with reverse geometry Contex OK lenses and to determine a time course for and the stability of visual and corneal changes in achieving maximal refractive, corneal curvature, and corneal thickness changes after overnight wear of OK B and D series lenses. Methods. This investigation was conducted under an Food and Drug Administration IDE G000059. Both eyes of 10 subjects were fitted with the lenses, and uncorrected visual acuity, refractive correction, contrast sensitivity, corneal curvature, and corneal thickness were measured at baseline and at 1 day, 1week, 1 month, and 3 months after lenses were worn. Except for baseline, data were collected at four different times during the day, immediately following lens removal and 4, 8, and 12 hours after lens removal. Results. The results from eight subjects showed that uncorrected visual acuity, refractive correction, contrast sensitivity, and corneal curvature all changed significantly (P =0.01) overnight. By the end of 1 week, all corneal and visual changes had reached a maximal level and remained fairly stable during the day. These changes were sustained at 3 months. The epithelial thickness data from four subjects showed that the corneal epithelial thickness was reduced by approximately 19 &mgr;m after 3 months of lens wear. Conclusions. Successful fitting of OK B and D series lenses requires a thorough understanding of the lens–cornea relationship. Full effect of overnight orthokeratology is achieved by the end of 1 week. The visual and corneal changes remain stable for all waking hours of the day and allow patients to enjoy excellent device-free vision (20/20).

Peripheral refraction with and without contact lens correction.

Purpose. Peripheral refractive error degrades the quality of retinal images and has been hypothesized to be a stimulus for the development of refractive error. The purpose of this study was to investigate the changes in refractive error across the horizontal visual field produced by contact lenses (CLs) and to quantify the effect of CLs on peripheral image blur. Methods. A commercial Shack-Hartmann aberrometer measured ocular wavefront aberrations in 5° steps across the central 60° of visual field along the horizontal meridian before and after CLs correction. Wavefront refractions for peripheral lines-of-sight were based on the full elliptical pupil encountered in peripheral measurements. Curvature of field is the change in peripheral spherical equivalent relative to the eyes optical axis. Results. Hyperopic curvature of field in the naked eye increases with increasing amounts central myopic refractive error as predicted by Atchison (2006). For an eccentricity of E degrees, field curvature is approximately E percent of foveal refractive error. Rigid gas permeable (RGP) lenses changed field curvature in the myopic direction twice as much as soft CLs (SCLs). Both of these effects varied with CLs power. For all lens powers, SCL cut the degree of hyperopic field curvature in half whereas RGP lenses nearly eliminated field curvature. The benefit of reduced field curvature was partly offset by increased oblique astigmatism. The net reduction of retinal blur because of CLs is approximately constant across the visual field. Conclusions. Both SCL and RGP lenses reduced the degree of hyperopic field curvature present in myopic eyes, with RGP lenses having greater effect. The tradeoff between field curvature and off-axis astigmatism with RGP lenses may limit their effectiveness for control of myopia progression. These results suggest that axial growth mechanisms that depend on retinal image quality will be affected more by RGP than by SCL lenses.

Longitudinal Changes in Corneal Asphericity in Myopia

Purpose To report the change in shape of the peripheral cornea (asphericity, Q) as it relates to myopia progression in adolescence. Methods Forty-eight subjects with initial ages between 11 and 13 years of age were observed for 5 years. Each subject had participated in a variety of soft contact lens studies and all had worn daily wear soft contact lenses successfully for the 2 years before collection of the second data set. Results Myopia increased by an average of 1.46 D and was strongly correlated with a 0.56-mm increase in axial length. There was no contribution to the change in myopia from the change in central radius of the cornea. A significant (p < 0.01, one tail) correlation was found between Q and the progression of myopia. Principal axis analysis yielded a slope of −0.04 in Q per diopter of increase in myopia. Conclusion These data show a shift to a more positive Q (in the oblate direction) with increased myopia.

Proton therapy for exudative age-related macular degeneration: a randomized, sham-controlled clinical trial☆

PURPOSE To examine the effect of proton beam irradiation on subfoveal choroidal neovascular membranes (CNVM) associated with age-related macular degeneration (AMD).Randomized, prospective, sham-controlled, double-masked treatment trial. METHODS Thirty-seven subjects with subfoveal CNVM due to AMD were randomly assigned to 16-Gy proton irradiation delivered in two fractions 24 hours apart or to sham control treatment. Recruitment was halted at 37 subjects for ethical reasons regarding randomization to sham treatment when Food and Drug Administration approval of Visudyne was anticipated. RESULTS Proton irradiation was associated with a trend toward stabilization of visual acuity, but this association did not reach statistical significance. No correlations were found within the fluorescein angiography data, including greatest linear dimension of CNVM total size, area of active leakage, area of associated subretinal hemorrhage, and intensity. CONCLUSIONS With the acceptance of photodynamic therapy, future studies will require more complex design and larger sample size to determine whether radiation can play either a primary or adjunctive role in treating these lesions.

Effects of target distance and pupil size on letter contrast sensitivity with simultaneous vision bifocal contact lenses.

Using simulated presbyopia we measured the effects of target vergence and pupil size on letter contrast sensitivity while subjects wore accurately centered simultaneous vision bifocal contact lenses. These experiments examined the increase in depth of focus provided by two bifocal contact lenses, and the effects of pupil size on near and distance vision. Monocular contrast sensitivity was assessed with three different designs of soft contact lenses. First, as a single vision control, we measured contrast sensitivity with a Bausch & Lomb, Optima 38 lens corrected for distance. We then measured contrast sensitivity with an Allergan Optical, Hydron Echelon, which is a diffractive simultaneous bifocal and a CIBA Vision, Spectrum, which is a concentric design, center-near, two-zone simultaneous vision bifocal. In general both bifocal contact lenses improved contrast sensitivity at near but decreased contrast sensitivity at distance (when compared to the single vision lens). With a fixed 3.5-mm artificial pupil, the Echelon lens had two clear peaks of sensitivity, one at distance (0.00 D) and one at near (-2.00 D), but the Spectrum lens had no clear peaks. Performance of the Spectrum lens depended on its center zone size. Near (-2.00 D) and distance (0.00 D) contrast sensitivity was measured with pupil sizes that ranged from 1 to 6 mm. The results showed that visual performance with a diffractive lens was almost independent of pupil diameter up to 3 to 4 mm but, as predicted, performance with the two-zone lens depended critically on pupil size.

Ocular response to lens care systems in adolescent soft contact lens wearers

The purpose of this 3-year prospective study is to compare high school-aged subjects, randomized into wearing soft contact lenses and spectacles, in terms of ocular health, refractive status, and self-esteem. This report focuses on ocular response to the lens care systems used through the first 18 months of the investigation. Eighty-four subjects were randomly fitted with either CibaSoft Visitint or CibaSoft-Standard Visitint contact lenses. Three lens care systems, Ciba Vision AOSept Disinfection/Neutralization Solutions (AOSept), Opti-Free Rinsing, Disinfection, and Storage Solution (Opti-Free), and ReNu Multi-Purpose Solution (ReNu), were randomly prescribed to the subjects wearing contact lenses. Limbal congestion, conjunctival hyperemia, corneal staining with fluorescein, corneal edema, and corneal neovascularization were graded at dispensing and at 6-, 12-, and 18- month visits. There were no significant differences among the groups at baseline. At 6 months statistically significant difference (p=0.0131, Kruksal-Wallis) was found for fluorescein staining of the cornea among the systems. At 12 months significant differences were found for corneal edema (p=0.0404, Kruksal-Wallis) and neovascularization (p=0.0315, Kruksal-Wallis) among the systems. At 18 months generalized conjunctival hyperemia was significantly different (p=0.0234, Kruksal-Wallis) among the systems along with greater limbal congestion (p=0.0015, Kruksal-Wallis) and neovascularization (p=0.0238, Kruksal-Wallis). In conclusion, the cornea, limbal vessels and the conjunctiva respond differently to the lens care systems used in this study. Overall, patients using AOSept showed less corneal staining and inflammatory response than patients using ReNu and Opti-Free.

Variability in hypoxia-induced corneal swelling is associated with variability in corneal metabolism and endothelial function.

Purpose. To determine if the variability in contact lens-induced corneal swelling is associated with variability in corneal oxygen consumption (QC) or corneal endothelial function. Methods. Corneal swelling was induced in 30 non-contact lens wearers by 2 hours of closed-eye contact lens wear, using thick (oxygen transmission [Dk/t] = 4.0 × 10−9) and thin (Dk/t = 12 × 10−9) hydrogel lenses of identical design. Following the induction of swelling, corneal thickness was continually measured by pachymetry until open-eye steady-state (OESS) thickness was achieved. The percentage of recovery per hour was calculated as a measure of endothelial function. Tear oxygen tension (PO2) beneath the hydrogels was measured in the open eye and after 5 minutes of eye closure to obtain estimates of QC. A change in corneal pH during eye closure while wearing the hydrogels was used as a measure of hypoxic acidosis. Associations between corneal swelling and endothelial cell density or corneal epithelial thickness were also tested. Results. There were modest but significant (P < 0.05) correlations between thick-lens corneal swelling and thick-lens closed-eye PO2 (r = −0.36); thin lens corneal swelling and thin-lens closed-eye and open-eye PO2 (r = −0.40 and −0.39, respectively). Corneal swelling also increases with increasing QC (r = + 0.29 to + 0.33). Corneal swelling was associated with the decrease in pH during lens wear (r = + 0.30 and + 0.20 for thick and thin lenses, respectively). Thick- and thin-lens corneal swelling was significantly associated with percentage of recovery per hour (r = −0.40 and −0.34, respectively). Multiple regression analysis of corneal swelling with PO2 and percentage of recovery per hour suggested an additive effect, however the effects were not significant. There was a modest inverse association between corneal swelling and OESS, however there were no associations between corneal swelling and endothelial cell density or epithelial thickness. Conclusions. The variability in contact lens-induced corneal swelling is associated with both corneal metabolic activity (QC and pH) and endothelial function (percentage of recovery per hour). Our interpretation is that individuals with larger QC produce more lactic acid (i.e., more swelling) whereas stronger endothelial function resists swelling. The modest correlations, however, suggest that other factors also are involved in explaining the phenomenon of corneal swelling.

Is binocular contrast sensitivity at distance compromised with multifocal soft contact lenses used to correct presbyopia

Purpose. The purpose of this investigation was to determine whether new experimental multifocal optical designs incorporating diffractive/refractive optics for correction of presbyopia in a soft contact lens would compromise binocular contrast sensitivity at distance while achieving 20/20 binocular visual acuity at near. Methods. Thirty presbyopic volunteers were fitted with Acuvue Bifocal soft lenses, two (FO1 and 3B1) experimental diffractive/refractive multifocal soft lenses separately and in combination as a pair and soft spherical lenses. Visual performance was evaluated via binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity after 1 week of lens wear. Results. The experimental lenses FO1 and the combination FO1/3B1 performed as well for binocular contrast sensitivity, binocular distance high-contrast visual acuity, and binocular distance low-contrast visual acuity as the habitual presbyopic correction and the spherical soft distance correction. A strong correlation (r = 0.73 and 0.53, respectively) was found between binocular contrast sensitivity and binocular distance low-contrast visual acuity with experimental FO1 and FO1/3B1 lenses. However, the correlation (r = 0.37 and 0.60, respectively) between binocular contrast sensitivity and binocular distance high- and low-contrast visual acuity with FO1 was weaker than that with the combination FO1/3B1 lenses. Subjective responses support the objective data. Discussion. The data show that experimental FO1 lens and the experimental combination of the FO1/3B1 lenses can be prescribed to not compromise distance binocular contrast sensitivity.