A Mendelian randomization study on the causal relationship between smoking, alcohol consumption, and the development of myopia and astigmatism.

The influence of environmental factors like smoking and alcohol on myopia and astigmatism is controversial. However, due to ethical concerns, alternative study designs are urgently needed to assess causal inference, as mandatory exposure to cigarettes and alcohol is unethical. Following comprehensive screenings, 326 single nucleotide polymorphisms (SNPs) related to myopia and astigmatism were included in the dataset. To validate the causal association between exposures such as cigarette smoking, alcohol consumption, and coffee intake, and outcomes namely astigmatism and myopia, five regression models were employed. These models encompassed MR-Egger regression, random-effects inverse-variance weighted (IVW), weighted median estimator (WME), weighted model, and simple model. The instrumental variables utilized in these analyses were the aforementioned SNPs. Apply Cochran's Q test to determine heterogeneity of SNPs; if heterogeneity exists, focus on IVW model results. The IVW model showed a 1.379-fold increase in the risk of astigmatism (OR = 1.379, 95%CI 0.822~2.313, P = 0.224) and a 0.963-fold increase in the risk of myopia (OR = 0.963, 95%CI 0.666~1.393, P = 0.841) for each unit increase in smoking. For each unit increase in coffee intake, the risk of astigmatism increased 1.610-fold (OR = 1.610, 95%CI 0.444~5.835, P = 0.469) and the risk of myopia increased 0.788-fold (OR = 0.788, 95%CI 0.340~1.824, P = 0.578). For each additional unit of alcohol consumption, the risk of astigmatism increased by 0.763-fold (OR = 0.763, 95%CI 0.380~1.530, P = 0.446), and none of the differences were statistically significant. However, for each unit of alcohol consumption, the risk of myopia increased by 1.597 times, and the difference was statistically significant (OR = 1.597, 95%CI 1.023~2.493, P = 0.039). The findings indicate that alcohol consumption is a risk factor for myopia but smoking and coffee intake do not affect its development. Additionally, there is no association between smoking, alcohol consumption, coffee intake, and the risk of astigmatism.

Comparison of surgically induced astigmatism between anterior and total cornea in 2.2 mm steep meridian incision cataract surgery.

BACKGROUND: This study aimed to compare surgically induced astigmatism (SIA) on the anterior and total cornea during cataract surgery through a 2.2 mm steep meridian incision. METHODS: The study included 69 left eyes of 69 patients who had undergone cataract surgery. The 69 eyes were classified into three subgroups according to the preoperative steep meridian. Following phacoemulsification, an intraocular lens was inserted into the bag. The keratometric measurements were taken 12 months postoperatively, on the anterior cornea (automated keratometer and anterior keratometry [K] from a rotating Scheimpflug camera) and total cornea (equivalent K reading [EKR] 3.0 mm, EKR 4.5 mm, total corneal refractive power (TCRP) 2.0 mm ring, TCRP 3.0 mm zone, TCRP 4.0 mm zone). The SIA was analyzed for each parameter. RESULTS: On the double-angle polar plot, the summated vector mean values of SIA determined by the automated keratometer and Scheimpflug anterior K were 0.28 diopter (axis: 177°) and 0.37 diopter (axis: 175°) in with-the-rule (WTR) astigmatism; 0.03 diopter (axis: 156°) and 0.18 diopter (axis: 177°) in oblique astigmatism; 0.15 diopter (axis: 96°) and 0.17 diopter (axis: 73°) in against-the-rule (ATR) astigmatism. The mean SIAs on the total cornea ranged from 0.31 to 0.42 diopter in WTR astigmatism; from 0.16 to 0.27 diopter in oblique astigmatism; from 0.04 to 0.11 diopter in ATR astigmatism. Mean magnitude SIA ranged from 0.41 to 0.46 diopter on anterior corneal surface and 0.50 to 0.62 diopter on total cornea. J0 and J45 of the posterior cornea showed no significant changes after cataract surgery, and the changes in J0 and J45 did not show any statistical differences between the anterior and total cornea (all p > 0.05). CONCLUSIONS: There were no differences in the summed vector mean values of SIA between the anterior cornea and the total cornea.

Short-term effects on ocular variables immediately after hyperbaric oxygen exposures.

PURPOSE: To determine ocular refraction, corneal thickness, corneal radius, corneal power, corneal astigmatism and intraocular pressure in patients before and immediately after repeated hyperbaric oxygen (HBO2) exposures twice a week during six weeks of HBO2 therapy. METHODS: 23 patients received HBO2 therapy at 2.4 ATA for 90 minutes daily in monoplace chambers for six weeks, five days a week. The Topcon TRK-1P instrument was installed next to the hyperbaric chambers to record the ocular measurements. RESULTS: A gross myopic shift developed at -0.95 ± 0.54 D (P ⟨ 0.001) in the right eye and -0.95 ± 0.53 D (P ⟨ 0.001) in the left eye during the six weeks of treatment. Myopic shift reversion, corneal thinning and reduced intraocular pressure appeared as immediate effects after a single HBO2 exposure, but resolved before the patients attended for the next measurement visit. CONCLUSIONS: Ocular variables were influenced by both cumulative and transient short-term effects during the HBO2 therapy. The short-term effects showed that the point of time for performing the ocular measurements after HBO2 exposure might influence the result and must be considered before making relevant comparisons among studies.

Combined astigmatic keratotomy and conductive keratoplasty to correct high corneal astigmatism.

PURPOSE: To determine the safety, efficacy, and predictability of combined astigmatic keratotomy (AK) and conductive keratoplasty (CK) for treating high corneal astigmatism. SETTING: University of California-Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: From January 1, 2004, to December 31, 2009, AK and CK were performed in eyes with corneal astigmatism of 5.0 diopters (D) or more after keratoplasty or trauma. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), defocus equivalent, mean astigmatism, efficacy index, and complications were evaluated. RESULTS: In 11 eyes of 11 patients, the mean UDVA improved from 1.54 logMAR ± 0.50 (SD) preoperatively to 0.69 ± 0.62 logMAR 3 months postoperatively (P < .001) and the mean CDVA from 0.55 ± 0.62 logMAR to 0.12 ± 0.11 logMAR (P = .028). The mean SE and mean defocus equivalent decreased from -1.25 ± 5.06 D to 3.13 ± 3.06 D (P = .15) and from 7.98 ± 4.41 D to 6.97 ± 3.73 D (P = .45), respectively; these changes were not statistically significant. The mean absolute astigmatism decreased from 10.25 ± 4.71 D to 4.31 ± 2.34 D (P < .001). The mean absolute orthogonal and mean oblique astigmatism showed a statistically significant decrease. The efficacy index was 0.82. One case of wound gape after AK required suturing. No infectious keratitis, corneal perforation, or graft rejection occurred. CONCLUSIONS: Results indicate that combined AK and CK is safe and effective for correcting high corneal astigmatism after surgery or trauma.

Customized topography-guided photorefractive keratectomy with the MEL-70 platform and mitomycin C to correct hyperopia after radial keratotomy.

PURPOSE: To evaluate topography-guided photorefractive keratectomy (PRK) for correcting hyperopia and astigmatism after radial keratotomy (RK). METHODS: Prospective study of 12 consecutive patients (19 eyes) who were treated with topography-guided PRK with 0.02% mitomycin C using an Asclepion-Meditec MEL-70 excimer laser with a 9.5-mm ablation zone. All eyes were operated by the same surgeon and followed for 1 year. RESULTS: Thirteen eyes had complete epithelialization by day 7 and all eyes by day 10. At 1 year, uncorrected visual acuity was 20/25 or better in 42.1% of eyes and 20/40 or better in 68.4%. Preoperative mean spherical equivalent refraction was +3.80+/-2.47 diopters (D) and +0.24+/-2.36 D (P<.001) 1 year postoperative, with 47.4% of eyes being within +/-1.00 D and 73.7% within +/-2.00 D. Preoperative mean cylinder was -2.30+/-1.41 D and -0.62+/-0.73 D (P<.001) 1 year postoperative. At 1 year, 68.4% of eyes gained at least 1 line of best-spectacle corrected visual acuity, 36.8% gained more than 1 line, and only 2 eyes lost 1 line (one due to corneal haze). Three eyes developed central haze. Mean regression from 6 to 12 months in these 3 eyes was +1.83 D and in the remaining 16 eyes was -0.50 D. CONCLUSIONS: Topography-guided PRK with mitomycin C was safe and reasonably effective for the treatment of hyperopia after RK.

Optics of conductive keratoplasty: implications for presbyopia management.

PURPOSE: To define the corneal optics of conductive keratoplasty (CK) and assess the clinical implications for hyperopia and presbyopia management. METHODS: Four analyses were done. (1) Multifocal effects: In a prospective study of CK, uncorrected visual acuity (UCVA) for a given refractive error in 72 postoperative eyes was compared to control eyes. (2) Surgically induced astigmatism (SIA): 203 eyes were analyzed for magnitude and axis of SIA. (3) Higher-order optical aberrations: Corneal higher-order optical aberrations were assessed for 36 eyes after CK and a similar patient population after hyperopic laser in situ keratomileusis (LASIK). (4) Presbyopia clinical trial: Visual acuity, refractive result, and patient questionnaires were analyzed for 150 subjects in a prospective, multicenter clinical trial of presbyopia management with CK. RESULTS: (1) 63% and 82% of eyes after CK had better UCVA at distance and near, respectively, than controls. (2) The mean SIA was 0.23 diopter (D) steepening at 175 degrees (P < .001); mean magnitude was 0.66 D (SD, 0.43 D). (3) After CK, composite fourth- and sixth-order spherical aberration increased; change in (Z12) spherical aberration alone was not statistically significant. When compared to hyperopic LASIK, there was a statistically significant increase in composite fourth- and sixth-order spherical aberration (P < .01) and spherical aberration (Z12) alone (P < .02); spherical aberration change was more prolate after CK. (4) After the CK monovision procedure, 80% of patients had J3 or better binocular UCVA at near; 84% of patients were satisfied. Satisfaction was associated with near UCVA of J3 or better in the monovision eye (P = .001) and subjectively good postoperative depth perception (P = .038). CONCLUSIONS: CK seems to produce functional corneal multifocality with definable introduction of SIA and higher-order optical aberrations, and development of a more prolate corneal contour. These optical factors may militate toward improved near vision function.

Nucleus fragmentation in a scleral pocket for small incision extracapsular cataract extraction.

We present a technique for planned manual extracapsular cataract extraction (ECCE) incorporating a modification of mini-nuc ECCE in which the scleral tunnel is made wide enough to allow a nucleus of any size to settle in the tunnel. A 5.0 mm, inverted-V chevron incision is used in which the exposed part of the nucleus lodged in the scleral pocket can be manually picked and fragmented until it is small enough to be removed through the incision. The chevron incision is flexible enough to allow a medium-sized nucleus to be extracted without fragmentation and implantation of a rigid 6.0 mm poly(methyl methacrylate) lens. Vector analysis of preoperative and 3 month postoperative keratometric results in 30 patients showed that the surgically induced vector was 0.54 diopter (D) +/- 0.58 (SD). Mean reduction in astigmatism was 0.08 +/- 0.39 D. The sutureless technique is fast and safe, allows a nucleus of any size to be extracted through a constant size 5.0 mm incision, and results in minimal postoperative astigmatism.

[Intracorneal suture. A simple procedure for the correction of astigmatism after cataract operation]. / La suture intracornéenne. Un procédé simple de cure d'astigmatisme après intervention de cataracte.

A simple surgical procedure to cure post cataract-surgery astigmatism is reported. Corneo-corneal (sometimes corneo-scleral), 9-0 polyamide monofilament sutures are put in radially at the end (or at the two ends) of the flattest meridian to increase its curvature and therefore its refractive power. 14 eyes were treated by this procedure, 11 of them for an "against the rule" astigmatism (1st group) and the 3 others for a "with the rule" astigmatism (2nd group). No corneal incision or resection is performed before suturing. Surgery has been efficient in all cases. As compared to a mean pre-op against the rule astigmatism of 6.55 +/- 2.20 diopters, the post-op residual astigmatism was no more than 3.16 +/- 1.94, 2.66 +/- 1.17, 2.69 +/- 1.33 and 2.80 +/- 1.74 diopters, respectively 8 days, 3 months, 6 months, 12 months after the surgery. The average axis of the effect of the surgery was almost perpendicular to the initial axis of the astigmatism. The visual acuity also improved but was dependent on other factors in addition to the refractive surgery. The results were stable from 3 months after surgery and remained unchanged in those cases where the follow-up period was 18 months or more. No significative complications have been observed and side effects have been negligible. In our opinion, the results that we have obtained open the way to the intracorneal suture, without any section of the cornea, as a potential treatment for excessive astigmatism.