- Journal of refractive surgery (Thorofare, N.J. : 1995)
- Published over 5 years ago
To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures.
In this brief review we will discuss the reasoning and evolution of our current use of combined very high-fluence collagen crosslinking and laser in situ keratomileusis. Several presentations and pertinent publications are reviewed, along with the key steps of the enhanced LASIK procedure. Long term outcome data support the safety and efficacy of LASIK Xtra in stabilizing myopic but also hyperopic LASIK results.In conclusion, we have compelling evidence that LASIK Xtra is a safe and effective adjunct.
Comparison between treatment with wavefront optimized and custom-Q laser-assisted in situ keratomileusis (LASIK) ablations. Our study included 400 eyes of 200 patients divided into two equal groups. All patients were treated for myopia and myopic astigmatism with LASIK. The first group was treated with wavefront optimized ablation and the second group with custom-Q ablation. They were examined preoperatively and postoperatively to assess asphericity, image quality, and other classical outcome parameters. The wavefront optimized ablation group comprised 200 eyes with a mean spherical equivalent refraction (SE) of -5.2188 diopters (D) (range: -1.15 to -10.50 D); the mean Q-value changed from 0.30 preoperatively to 0.06 postoperatively. The custom-Q ablation group also comprised 200 eyes with a mean SE of -5.1575 D (range: -1.35 to -9.00 D); the mean Q-value changed from 0.32 preoperatively to 0.03 postoperatively. A statistically significant difference in postoperative change in Q-values (P = 0.02) and in postoperative visual acuity (P = 0.42) between the two groups was noted. There was no difference between the two groups regarding refractive correction. There was a marginally significant change in BSCVA (best spectacle-corrected visual acuity) between the two groups, and less impairment in the corneal asphericity in the custom-Q group.
- Optometry and vision science : official publication of the American Academy of Optometry
- Published about 5 years ago
PURPOSE: To investigate the relationship between parental refractive error and the nearwork-induced transient myopia (NITM) characteristics of their children. METHODS: Three hundred sixty children (173 boys and 187 girls) aged 6 to 17 years were tested. Initial NITM and its decay time (DT) were assessed objectively (WAM-5500, Grand-Seiko) immediately after binocularly viewing and performing a sustained near task (5 diopters [D]) for 5 minutes, incorporating a cognitive demand with full distance refractive correction in place. The NITM was classified into three categories: low (<0.15 D), moderate (0.15 to 0.30 D), or high (≥0.30 D), whereas its decay was classified into two categories, namely, complete or incomplete. In addition, the children were divided into three groups based on the number of myopic parents (none, one, or two) and into four groups based on the level of parental myopia (no, low, moderate, or high). RESULTS: Neither paternal nor maternal refractive error was associated with either their children's initial NITM magnitude or its DT in the myopic, emmetropic, or hyperopic groups or the combined group. No significant differences (p > 0.05) in the NITM magnitude, DT, or decay time constant were found as related to the number of myopic parents or level of parental myopia. Multiple odds ratio for incomplete decay of NITM did not change significantly (p > 0.05) with either an increase in number of myopic parents or level of parental myopia. CONCLUSIONS: There was no association between parental refractive error and their children’s NITM characteristics. This suggests a primary environmental basis for the NITM characteristics in the children.
A cross-sectional study was undertaken in Nakuru, Kenya to assess the prevalence of refractive error and the spectacle coverage in a population aged ≥50 years. Of the 5,010 subjects who were eligible, 4,414 underwent examination (response rate 88.1 %). LogMAR visual acuity was assessed in all participants and refractive error was measured in both eyes using a Topcon auto refractor RM8800. Detailed interviews were undertaken and ownership of spectacles was assessed. Refractive error was responsible for 51.7 % of overall visual impairment (VI), 85.3 % (n = 191) of subjects with mild VI, 42.7 % (n = 152) of subjects with moderate VI, 16.7 % (n = 3) of subjects with severe VI and no cases of blindness. Myopia was more common than hyperopia affecting 59.5 % of those with refractive error compared to 27.4 % for hyperopia. High myopia (<-5.0 DS) was also more common than extreme hyperopia (>+5.0 DS). Of those who needed distance spectacles (spectacle coverage), 25.5 % owned spectacles. In conclusion, the oldest, most poor and least educated are most likely to have no spectacles and they should be specifically targeted when refractive services are put in place.
To compare early literacy of 4- and 5-year-old uncorrected hyperopic children with that of emmetropic children.
To compare the postoperative higher-order-aberrations (HOAs) after hyperopic small incision lenticule extraction (SMILE), hyperopic laser-assisted in situ keratomileusis(LASIK), and lenticule implantation for correction of hyperopia.
During postnatal refractive development, an emmetropization mechanism uses refractive error to modulate the growth rate of the eye. Hyperopia (image focused behind the retina) produces what has been described as “GO” signaling that increases growth. Myopia (image focused in front of the retina) produces “STOP” signaling that slows growth. The interaction between GO and STOP conditions is non-linear; brief daily exposure to STOP counteracts long periods of GO. In young tree shrews, long-wavelength (red) light, presented 14 h per day, also appears to produce STOP signals. We asked if red light also shows temporal non-linearity; does brief exposure slow the normal decrease in hyperopia in infant animals? At 11 days after eye opening (DVE), infant tree shrews (n=5/group) began 13 days of daily treatment (red LEDs, 624±10 or 636±10nm half peak intensity bandwidth) at durations of 0 h (normal animals, n=7) or 1, 2, 4, or 7 h. Following each daily red period, colony lighting resumed. A 14 h red group had no colony lights. Refractive state was measured daily; ocular component dimensions at the end of the 13-day red-light period. Even 1 h of red light exposure produced some hyperopia. The average hyperopic shift from normal rose exponentially with duration (time constant 2.5 h). Vitreous chamber depth decreased non-linearly with duration (time constant, 3.3 h). After red treatment was discontinued, refractions in colony lighting recovered toward normal; the initial rate was linearly related to the amount of hyperopia. The red light may produce STOP signaling similar to myopic refractive error.
Hyperopia is a common refractive error, apparent in 25% of Europeans. Treatments include spectacles, contact lenses, laser interventions and surgery including implantable contact lenses and lens extraction. Laser treatment offers an expedient and reliable means of correcting ametropia. LASIK is well-established however SMILE (small-incision lenticule extraction) or lenticule implantation (derived from myopic laser-correction) are newer options. In this study we compared the outcomes of hyperopic LASIK, SMILE and lenticule re-implantation in a primate model at +2D/+4D treatment. While re-implantation showed the greatest regression, broadly comparable refractive results were seen at 3-months with SMILE and LASIK (<1.4D of intended), but a greater tendency to regression in +2D lenticule reimplantation. Central corneal thickness showed greater variation at +2D treatment, but central thickening during lenticule reimplantation at +4D treatment was seen (-17± 27μm LASIK, -45 ± 18μm SMILE and 28 ± 17μm Re-implantation; p <0.01) with expected paracentral thinning following SMILE. Although in vivo confocal microscopy appeared to show higher reflectivity in all +4D treatment groups, there were minimal and inconsistent changes in inflammatory responses between modalities. SMILE and lenticule re-implantation may represent a safe and viable method for treating hyperopia, but further optimization for lower hyperopic treatments is warranted.