José Manuel González-Méijome

Prevalence of corneal astigmatism before cataract surgery.

PURPOSE: To analyze the prevalence and presentation patterns of corneal astigmatism in cataract surgery candidates. SETTING: University of Valencia, Valencia, Spain. METHODS: Refractive and keratometric values were measured before surgery in patients having cataract extraction. Descriptive statistics of refractive and keratometric cylinder data were analyzed and correlated by age ranges. RESULTS: Refractive and keratometric data from 4540 eyes of 2415 patients (mean age 60.59 years ± 9.87 [SD]; range 32 to 87 years) differed significantly when the patients were divided into 10‐year subsets. There was a trend toward less negative corneal astigmatism values, except the steepest corneal radius and the J45 vector component, in older groups (Kruskal‐Wallis, P<.01). In 13.2% of eyes, no corneal astigmatism was present; in 64.4%, corneal astigmatism was between 0.25 and 1.25 diopters (D) and in 22.2%, it was 1.50 D or higher. CONCLUSIONS: Corneal astigmatism less than 1.25 D was present in most cataract surgery candidates; it was higher in about 22%, with slight differences between the various age ranges. This information is useful for intraocular lens (IOL) manufacturers to evaluate which age ranges concentrate the parameters most frequently needed in sphere and cylinder powers and for surgeons to evaluate which IOLs provide the most effective power range.

Central and peripheral corneal thickness measurement with Orbscan II and topographical ultrasound pachymetry

Purpose: To compare thickness measurements of the central 6.0 mm of the cornea obtained with the Orbscan® II topography system and topographical ultrasound pachymetry. Setting: School of Optometry, University of Santiago de Compostela, Galicia, Spain. Methods: In 24 right eyes, pachymetric measurements were taken at the center and 1.2 mm and 3.0 mm on the superior and inferior hemimeridians. A 1‐sample t test was applied to assess the significance of the relationship between Orbscan II and ultrasound methods. The relationship between the 2 was assessed by analyzing regression and plotting the differences against the mean corneal thickness. Orbscan II data were analyzed in 3 ways: (1) without the application of an acoustic equivalent correction factor; (2) with a correction factor of 0.92, as recommended by the manufacturer; (3) with correction using the equations derived in this study. The data were systematically compared with those of ultrasound pachymetry. Results: Before the correction factor was applied, the Orbscan II overestimated the corneal thickness at all locations, with the mean difference (48.15 &mgr;m ± 33.74 [SD]) significantly different from zero (P < .001). Differences increased toward the periphery, and the reliability of Orbscan II readings seemed to decrease with thicker corneas. After the acoustic equivalent was applied, the differences were significantly less; however, this effect did not seem clinically significant as large differences remained. When specific corrective equations were applied for each corneal location, the level of agreement between Orbscan II and ultrasound pachymetry improved substantially; the mean (–0.11 ± 15.22 &mgr;m) was not statistically different from zero (P > .05). Conclusions: The acoustic equivalent correction factor proposed by the manufacturer to obtain corneal thickness measurements with the Orbscan II compared to those from ultrasound pachymetry was not valid for all corneal topography positions. Orbscan II measurements agreed better with those of ultrasound pachymetry when equations for the central and each peripheral location across the topography were applied.

Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population

The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare®) in comparison with the Goldmann applanation tonometer (AT).

Implantable Collamer Posterior Chamber Intraocular Lenses: A Review of Potential Complications

PURPOSE To review the peer-reviewed literature reporting postoperative complications of the most recent models of Visian Implantable Collamer posterior chamber intraocular lenses (ICL, STAAR Surgical Co). METHODS A literature search of the PubMed database was performed to identify all articles related to ICL complications. Articles were obtained and reviewed to identify those that reported complications using the latest ICL designs. RESULTS Cataract was the major postoperative complication reported: 136 (5.2%) in 2592 eyes. Of those, 43.4% (n=59) were reported within 1 year, 15.4% (n=21) between 1 and 3 years, and 35.3% (n=48) ≥ 3 years after ICL implantation. Twenty-one (15.4%) cataracts were reported as surgically induced, 46 (33.8%) eyes had poor vault (<200 μm), and cataract surgery was carried out in 27.9% (n=38) of eyes. Early acute intraocular pressure increase was also reported to be relatively frequent, whereas acute pupillary block was less frequent and mostly resolved with additional iridotomies. A total of 42 ICLs were explanted due to cataract and IOP. Reported endothelial cell loss varied from 9.9% at 2 years to 3.7% 4 years postoperatively. This loss was reported to be more pronounced within the first 1 to 2 years, with stability or lower progression after that time. CONCLUSIONS The majority of reported complications after ICL implantation are cataract formation. The improvements in lens geometry and more accurate nomograms applied to the selection of the lens to be implanted, in addition to the surgeons learning curve, might be factors in the decreased occurrence of postoperative complications reported currently.

Accuracy of the new ICare rebound tonometer vs. other portable tonometers in healthy eyes.

Purpose. The ICare (Tiolat Oy, Helsinki, Finland) is a new portable tonometer that measures intraocular pressure (IOP) with a new rebound method, in which a very light probe is used to make momentary contact with the cornea in slow motion. The purpose of this study is to assess the accuracy of the ICare IOP measurements by comparing them against other portable tonometers: Perkins applanation tonometer and Tono-Pen XL digital tonometer (Medtronic Solan, Jacksonville, FL). Methods. Sixty-five young subjects were assessed with each of the tonometers. ICare tonometry was performed first, followed by Perkins applanation tonometry and Tono-Pen XL in a random order. Regression analysis was used to evaluate the relationship between the Perkins tonometer and the remaining tonometers used in this study. Tonometers were also compared by plotting the difference between the methods against the mean. The hypothesis of zero bias was examined by a paired t test and the 95% limits of agreement (LoA) were calculated. Results. ICare and Tono-Pen XL significantly overestimate IOP when compared with Perkins applanation tonometry. The mean of the difference between Perkins and ICare and Perkins and Tono-Pen XL was (mean ± standard deviation) −3.35 ± 2.28 mm Hg and −2.78 ± 2.53 mm Hg, respectively. The 95% LoA between Perkins tonometry and ICare tonometry were between −7.81 and +1.12 and between Perkins tonometry and Tono-Pen XL tonometry between −7.74 and +2.18. Conclusions. Compared with Perkins tonometry, the ICare tonometer allows clinicians to estimate IOP with a portable, rapid, and noninvasive method with similar reliability to that offered by Tono-Pen XL. Clinicians should be aware of the systematic overestimation of IOP with the ICare. Further research is needed to evaluate the performance of rebound tonometry in populations with higher IOP and assess the reliability of this technique in the early detection and follow up of glaucomatous patients.

Posterior chamber collagen copolymer phakic intraocular lenses to correct myopia : five-year follow-up

PURPOSE: To evaluate the long‐term safety and efficacy of posterior chamber collagen copolymer phakic intraocular lens (pIOL) implantation to correct myopia. SETTING: Fernández‐Vega Ophthalmological Institute, Oviedo, Spain. DESIGN: Cohort study. METHODS: Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, pIOL vault, endothelial cell loss, and adverse events were evaluated for 5 years after implantation of the Visian Implantable Collamer Lens pIOL for moderate to high myopia. RESULTS: The mean spherical equivalent (188 eyes) decreased from −11.17 diopters (D) ± 3.40 (SD) preoperatively to −0.88 ± 0.72 D 5 years postoperatively. The mean change in refraction from 1 month to 5 years was −0.65 ± 0.65 D. The mean UDVA and CDVA (Snellen decimal) were 0.69 ± 0.26 and 0.83 ± 0.15, respectively. The mean safety and efficacy indices were 1.27 ± 0.33 and 0.89 ± 0.35, respectively. No eye lost more than 2 lines of visual acuity; 70% achieved 0.80 or better CDVA. Three eyes (1.6%) developed late anterior subcapsular cataract that was clinically significant in 1 case, leading to pIOL removal and phacoemulsification. Of the 3 eyes (1.6%) with a mild transient increase in intraocular pressure (up to 27 mm Hg), none required a second surgical procedure or prolonged topical medication. The total endothelial cell loss (considered cumulatively at consecutive intervals through 5 years) was 7.7%. There was a tendency toward decreased pIOL vault decrease over time. No vision‐threatening complications occurred. CONCLUSION: Implantation of the collagen copolymer pIOL for moderate to high myopia was safe and effective and provided long‐term predictable, stable refractive results. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Night vision disturbances after successful LASIK surgery

Objective: To evaluate the changes in correlations of higher order aberrations of the first corneal surface with halo phenomena, a form of image degradation, under night vision conditions measured objectively after successful LASIK (laser in situ keratomileusis) surgery. Methods: A prospective, observational, analytical study of 110 eyes that had undergone successful LASIK surgery for myopia and astigmatism. Preoperative sphere was (mean (SD)) −3.48 (1.70) D (0 to −8.00 D) and preoperative cylinder was −0.86 (0.87) D (0 to −4.00 D). Visual disturbance caused by halo phenomena was measured with the Starlights v1.0, and pupil size was measured with Colvard pupilometry after adaptation to a dark environment (0.17 lux). Corneal aberrations were computed for a corneal diameter representative of the eye’s entrance pupil under night vision conditions. Results: The halo disturbance index increased in this study by a factor of 2.15 after successful LASIK surgery. Total root mean square for monochromatic higher order aberration displayed a significant correlation with halo disturbance index (r = 0.42; p<0.01). However, only secondary astigmatism (r = 0.36; p<0.01), coma (r = 0.25; p = 0.02) and spherical aberration (r = 0.40; p<0.01) were responsible for such behaviour, with the remaining corneal aberrations up to the sixth order not displaying any significant correlation when considered individually. Conclusion: Patients undergoing LASIK procedures display an increase of halo phenomena around lights in night vision conditions, even when the results of the surgery are considered entirely satisfactory according to current international standards of predictability, efficacy and safety. Secondary astigmatism, coma and spherical aberration are the higher order aberrations up to the sixth order that significantly correlated with halo disturbance index.

Modern scleral contact lenses: A review

Scleral contact lenses (ScCL) have gained renewed interest during the last decade. Originally, they were primarily used for severely compromised eyes. Corneal ectasia and exposure conditions were the primary indications. However, the indication range of ScCL in contact lens practices seems to be expanding, and it now increasingly includes less severe and even non-compromised eyes, too. All lenses that partly or entirely rest on the sclera are included under the name ScCL in this paper; although the Scleral Lens Education Society recommends further classification. When a lens partly rests on the cornea (centrally or peripherally) and partly on the sclera, it is called a corneo-scleral lens. A lens that rests entirely on the sclera is classified as a scleral lens (up to 25 mm in diameter maximum). When there is full bearing on the sclera, further distinctions of the scleral lens group include mini-scleral and large-scleral lenses. This manuscript presents a review of the current applications of different ScCL (all types), their fitting methods, and their clinical outcomes including potential adverse events. Adverse events with these lenses are rare, but the clinician needs to be aware of them to avoid further damage in eyes that often are already compromised. The use of scleral lenses for non-pathological eyes is discussed in this paper.

Peripheral refraction in myopic patients after Orthokeratology

Purpose. The purpose of this study was to characterize the central and peripheral refraction across the horizontal meridian of the visual field before and after myopic corneal refractive therapy (CRT) with contact lenses. Methods. Twenty-eight right eyes from 28 subjects (mean age ± SD = 24.6 ± 6.3 years) were fitted with Paragon CRT contact lenses to treat myopia between −0.88 and −5.25 D of spherical equivalent. Along with a complete set of examination procedures to assess suitability for treatment, the central and peripheral refractions were measured along the horizontal meridian up to 35° of eccentricity in the nasal and temporal retinal area in 5° steps. Results. Baseline central average spherical equivalent (M) measured by subjective refraction changed from −1.95 ± 1.27 D to −0.38 ± 0.67 D. Changes in M component ranged between 1.42 ± 0.89 D at center and 0.43 ± 0.88 D at 20° in the temporal retina (p < 0.002). At 25° to both sides of the central refraction measurement, peripheral refraction after treatment was not statistically different from baseline values (p > 0.351). Beyond the 25° limit, M component changed in the myopic direction up to −1.11 ± 0.88 D at 35° in temporal retina (p < 0.001). Treatment induced was symmetric between nasal and temporal visual field along the horizontal meridian (p > 0.05 for all eccentricities). Furthermore, the degree of myopic increase in spherical equivalent for 30° (r2 = 0.573, p < 0.001) and 35° (r2 = 0.645, p < 0.001) eccentric refraction was highly correlated with axial spherical equivalent at baseline. Conclusions. CRT inverts the pattern of peripheral refraction in spherical equivalent refraction, creating a treatment area of myopic reduction within the central 25° of visual field, and a myopic shift beyond the 25°. In peripheral refraction for 30° and 35°, the amount of myopia induced in terms of spherical equivalent has an almost 1:1 relationship with the amount of baseline spherical equivalent refraction to be corrected.

Short-Term Changes in Light Distortion in Orthokeratology Subjects

Purpose. Quantifying adaptation to light distortion of subjects undergoing orthokeratology (OK) for myopia during the first month of treatment. Methods. Twenty-nine healthy volunteers (age: 22.34 ± 8.08 years) with mean spherical equivalent refractive error −2.10 ± 0.93D were evaluated at baseline and days 1, 7, 15, and 30 of OK treatment. Light distortion was determined using an experimental prototype. Corneal aberrations were derived from corneal topography for different pupil sizes. Contrast sensitivity function (CSF) was analyzed for frequencies of 1.50, 2.12, 3.00, 4.24, 6.00, 8.49, 12.00, 16.97, and 24.00 cpd under photopic conditions. Results. Average monocular values of all light distortion parameters measured increased significantly on day 1, returning to baseline after 1 week (P < 0.05 in all cases). Spherical-like aberration stabilized on day 7 for all pupil diameters, while coma-like for smaller pupils only. CSF was significantly reduced on day 1 for all spatial frequencies except for 1.5 cpd, returning to baseline afterwards. Significant correlation was found between light distortion and contrast sensitivity for middle and high frequencies (P < 0.05) after 15 days. Conclusion. Despite consistently increased levels of corneal aberrations, light distortion tends to return to baseline after one week of treatment, suggesting that neural adaptation is capable of overcoming optical quality degradation.