Comparison of Whole Eye versus First-Surface Astigmatism in Down Syndrome.

PURPOSE: Subjects with Down syndrome have structural differences in the cornea and lens, as compared with the general population. This study investigates objectively measured refractive and corneal astigmatism, as well as calculated internal astigmatism in subjects with and without Down syndrome. METHODS: Refractive (Grand Seiko autorefraction) and anterior corneal astigmatism (difference between steep and flat keratometry obtained with Zeiss Atlas corneal topography) were measured in 128 subjects with Down syndrome (mean [±SD] age, 24.8 [±8.7] years) and 137 control subjects without Down syndrome (mean [±SD] age, 24.9 [±9.9] years), with one eye randomly selected for analysis per subject. Refractive astigmatism and corneal astigmatism were converted to vector notation (J0, J45) to calculate internal astigmatism (Refractive - Corneal) and then converted back to minus cylinder form. RESULTS: Mean [±SD] refractive astigmatism was significantly greater in subjects with Down syndrome than in control subjects (-1.94 [±1.30] DC vs. -0.66 [±0.60] DC, t = -10.16, p < 0.001), as were mean corneal astigmatism (1.70 [±1.04] DC vs. 1.02 [±0.63] DC, t = 6.38, p < 0.001) and mean internal astigmatism (-1.07 [±0.68] DC vs. -0.77 [±0.41] DC, t = -4.21, p < 0.001). A positive linear correlation between corneal and refractive astigmatism was observed for both study populations for both the J0 and J45 vectors (p < 0.001 for all comparisons; R(2) range, 0.31 to 0.74). The distributions of astigmatism orientation differed significantly between the two study populations for comparisons of corneal and calculated internal astigmatism (χ(2), p < 0.007), but not refractive astigmatism (p = 0.46). CONCLUSIONS: This study demonstrates that corneal astigmatism is predictive of overall refractive astigmatism in subjects with Down syndrome, as it is in the general population. The greater magnitudes of astigmatism and wider variation of astigmatism orientation in subjects with Down syndrome for refractive, corneal, and calculated internal astigmatism are likely attributable to previously reported differences in the structure of the cornea and internal optical components of the eye from that of the general population.

Central and peripheral corneal thinning in keratoconus.

PURPOSE: Recent data regarding the mid-peripheral portion of the removed corneal button in transplant surgery indicate histopathologically that keratoconus was present also in the peripheral portion of the button. The intent of this study was therefore to investigate if peripheral changes could also be detected clinically by measuring the central and peripheral corneal thickness of KC patients. METHODS: Corneal pachymetry was measured with the Visante optical coherence tomography and Orbscan II. Of 52 subjects, 26 were KC subjects and 26 were age- and sex-matched control subjects. RESULTS: Corneal thickness, in KC patients, was significantly reduced in all areas compared with corneal thickness among controls with both the Visante optical coherence tomography and Orbscan II. CONCLUSION: The results of the present study have provided clinical evidence that KC is a disease affecting a wider area of the cornea. Although the KC cornea shows the greatest change in thickness in the ectatic region, this attenuation declines toward the periphery. The presence of peripheral thinning indicated that KC may be a "pancorneal" pathology and not limited to the ectatic portion.

Morphology of contact lens-induced conjunctival epithelial flaps: a pilot study.

PURPOSE: Conjunctival epithelial flap (CEF) is a conjunctival condition most commonly seen in silicone hydrogel contact lens wearers. This study utilized impression cytology to investigate the cellular composition and health of CEFs. METHODS: Nine (9) subjects were enrolled - 3 non-lens wearers, 3 contact lens wearers without CEF, and 3 contact lens wearers with CEFs wearing 8.4/13.8 lotrafilcon A lenses. Impression cytology samples were collected from the flap or similar locations, if CEF was absent, using rectangular 5 mm × 2 mm Millipore HAWP02500 membrane filters. The filters were gently pressed onto the conjunctiva, subsequently fixed in 95% alcohol, stained with hematoxylin-eosin and evaluated under an Olympus IX70 microscope. Measurements of the longest cell and nucleus dimensions were measured on 40 cells from each filter by utilizing NIH Image 1.63. RESULTS: CEF consisted of multilayers of epithelial and goblet cells and were devoid of inflammatory cells, basement membrane material and stromal tissue. The cytoplasmic and nuclear dimensions were similar within the groups and the cytoplasm-to-nucleus ratio was not different between the flap group and the non-lens wearing group. CONCLUSION: The CEF appeared to be formed by healthy epithelial and goblet cells that have been dislocated from their normal location along the conjunctival surface by the lens edge. No inflammatory cells were present in this contact lens induced condition, which is reported to be associated most commonly with the silicone hydrogel material.

Clinical benefits of a new multipurpose disinfecting solution in silicone hydrogel and soft contact lens users.

OBJECTIVES: To evaluate the safety and efficacy of a new multipurpose disinfecting solution (MPDS) containing a diblock copolymer, poly(oxyethylene)-poly(oxybutylene), designed to improve the wetting properties of silicone-hydrogel lenses. METHODS: This 90-day, randomized, concurrently controlled, double-masked, multisite study involved 573 subjects at 30 investigational sites in the United states. Existing lens wearers were randomly assigned to either regimen 1 (OPTI-FREE PureMoist, a newly developed formulation, Alcon Laboratories Inc., Fort Worth, TX) or regimen 2 (renu fresh, Bausch and Lomb Inc., Rochester, NY). At baseline, days 7, 30, 60, and 90, the subjects recorded subjective evaluations relating to lens acceptability and comfort, wearing time, and rewetting drop frequency, whereas investigators assessed slitlamp findings (including corneal fluorescein staining), lens deposits (modified Rudko), visual acuity, and adverse events. Group IV lenses were collected for ex vivo measurement of lysozyme deposits. RESULTS: Differences favoring regimen 1 were noted on day 90 for subjective evaluations of lens comfort (insertion, removal, overall); lens moisture and freshness; gentle on eye; clear vision; and lens handling (all P<0.004). Corneal fluorescein staining severity and area and lysozyme deposits (group IV lenses) were lower with regimen 1 (P<0.0001). CONCLUSIONS: This 90-day study shows that the new MPDS designed for silicone-hydrogel lenses is safe and effective when used by both silicone-hydrogel and traditional soft lens wearers. By improving comfort and decreasing lysozyme deposits and corneal fluorescein staining, the new MPDS enhances patients' wearing experience and helps maintain optimal lens performance.

Corneal and conjunctival epithelial staining in hydrogel contact lens wearers.

OBJECTIVES: The purpose of this study was to investigate the prevalence of conjunctival and corneal epithelial staining in soft contact lens wearers and to see if staining could be associated with factors such as type of lens worn, wearing time, care system, age, and sex. METHODS: The records of 338 adapted hydrogel contact lens wearers were examined retrospectively. RESULTS: Conjunctival staining was found to be present in 32.5% of the subjects and corneal staining was found to be present in 19.5% of subjects. None of the subjects had staining above grade 2 using the Cornea and Contact Lens Research Unit scale. Because of the low prevalence of staining, the low grading of staining found and the large variation in refractive power, lens type worn, wearing modality, and solution used statistical analysis for association between staining and different factors could only be performed for the association between sex and staining and between corneal and conjunctival staining. However, no statistical significant association could be demonstrated. DISCUSSION: Despite the low prevalence of staining the conjunctiva and cornea should be examined carefully in contact lens wearers and prospective wearers because the conjunctival and corneal epithelium serve as protective barriers for the underlying layers of the cornea and conjunctiva. To allow comparison of data obtained in different studies assessing corneal staining, it is recommended that clinicians develop and adopt a universal standard protocol for this measure.

Empirical advanced orthokeratology through corneal topography: the University of Houston clinical study.

PURPOSE: Traditionally, orthokeratology has used diagnostic lenses to determine the best fit. The purpose of this study was to determine the efficacy of fitting empirically from corneal topography, without the use of diagnostic lenses. METHODS: Twenty-nine subjects, 18 to 37 years old, with myopia of 1.00 to 4.00 diopters (D) and astigmatism of no more than 1.50 D, were entered into this 6-month study. Corneal topography, scanning slit topography and corneal thickness (Orbscan), confocal microscopy, ultrasound corneal thickness, aberrometry, and biomicroscopy were used to assess corneal changes. Unaided logMAR high-contrast visual acuity, subjective refraction, and questionnaires were used to monitor vision and symptoms. Follow-up visits were scheduled after 1 day, 1 week, 2 weeks, 1 month, 3 months, and 6 months. RESULTS: For 6-month data, unaided logMAR acuity improved from 0.78 +/- 0.26 in the right eye and 0.75 +/- 0.22 in the left eye to 0.06 +/- 0.18 in the right eye and 0.04 +/- 0.16 in the left eye. Myopia decreased from -2.55 +/- 0.87 D in the right eye and -2.47 +/- 0.89 D in the left eye to +0.45 +/- 0.74 D in the right eye and -0.17 +/- 0.69 D in the left eye. Shape factor, using corneal topography, increased from 0.85 +/- 0.13 in the right eye and 0.85 +/- 0.15 in the left eye to 1.28 +/- 0.32 in the right eye and 1.30 +/- 0.29 in the left eye. Both eyes showed a decrease in lower-order aberrations (i.e., defocus) and an increase in higher-order aberrations (i.e., spherical aberrations and coma). CONCLUSIONS: Myopia reduction after 1 week was clinically insignificant from the 1-month results, indicating that the full effect is achieved by 1 week. Neither total nor epithelial corneal thickness varied significantly from baseline measurements.

The diagnosis and characteristics of moderate dry eye in non-contact lens wearers.

PURPOSE: To identify and characterize moderate dry eye in non-contact lens wearers with a new scoring system-based dry eye questionnaire and to determine which objective tests better differentiate patients with moderate dry eye from healthy patients. METHODS: Fifty-two healthy subjects (21 women and 31 men with a mean age of 27.8 +/- 9.2 years) and 37 subjects with moderate dry eye (33 women and 4 men with a mean age of 36.4 +/- 12.9 years) completed a 42-item dry eye questionnaire. Seventeen healthy subjects (11 women and 6 men with a mean age of 30.5 +/- 9.7 years) and 28 subjects with moderate dry eye (24 women and 4 men with a mean age of 38.50 +/- 3.8 years) underwent additional objective assessment of ocular surface health, tear osmolality, tear stability, and tear volume. RESULTS: Subjects with moderate dry eye scored significantly higher (49.8 +/- 20.3, P<0.0001) on the dry eye questionnaire than did normal subjects (11.7 +/- 10.3). Ocular irritation symptoms worsened with progression of time of day in both groups of subjects. Internal reliability (0.95 Cronbach alpha) was excellent, and concurrent validity (Spearman rho 0.507) was acceptable when compared to the McMonnies and Ho dry eye questionnaire. Significant differences in tear osmolality (P<0.00001), invasive tear breakup time (P<0.034), and corneal vital dye staining (P<0.0001) were detected between the two groups of subjects. A stepwise linear regression on objective clinical tests, however, did not account for 77% of the total variance in the questionnaire scores. CONCLUSIONS: A unique scoring system-based dry eye questionnaire was validated to separate non-contact lens wearers with moderate dry eye from healthy subjects. Objective tests of tear osmolality and stability and ocular surface integrity were better than other clinical measures at identifying differences between the two subject groups. The results strongly support the evidence that the diagnosis and treatment of moderate dry eye requires a detailed assessment of self-perceived symptoms and that objective clinical testing alone may be insufficient.

Reverse-geometry gas-permeable lens design for pellucid marginal degeneration.

PURPOSE: To report a case of treating a patient with pellucid marginal degeneration (PMD) by using a reverse-geometry gas-permeable lens design. METHODS: A 38-year-old Hispanic man was referred for having reduced visual acuity secondary to distorted corneas. The patient was diagnosed with PMD after an extensive slitlamp examination showed a thinning of the inferior peripheral cornea in both eyes. Corneal topography (Orbscan II) was performed to help confirm the diagnosis. A Reverse Aspheric Ortho Focus (RAOF) gas-permeable lens was fitted on this patient. RESULTS: The Orbscan II corneal topography showed distinct peripheral steepening, a pronounced astigmatic pattern (greater in the left eye than in the right), and thinner corneas in the inferior periphery than centrally. The fluorescein pattern of the RAOF 5 lenses showed central alignment, good edge lift 360 degrees, mid peripheral bearing with 0.5 mm vertical movement on blinking, and good centration. The patient's distance visual acuity with the lenses was 20/20-1 in the right eye and 20/20 in the left. CONCLUSIONS: The Orbscan II was an important tool in making the diagnosis of early PMD, because few clinical signs were observed. Not only does the Orbscan II provide the clinician with a topographic map of the cornea, but it also measures the corneal thickness, which aided in the diagnosis of this patient. In addition, the posterior float measurement provided by the Orbscan II may be instrumental in making a differential diagnosis. A reverse-geometry gas-permeable lens provided the patient with improved peripheral fit over conventional designs, adequate comfort, and optimal visual acuity.

A comparison of tear volume (by tear meniscus height and phenol red thread test) and tear fluid osmolality measures in non-lens wearers and in contact lens wearers.

PURPOSE: Various measures are available to assess the tear film, yet little specific information is available on how they relate to each other. An exploratory study was undertaken to assess three measures and their relationship in non-contact lens wearers and in contact lens wearers. METHODS: Forty-three young subjects (mean age, 25.0 +/- 3.1 years; 19 men and 24 women) without overt ocular disease were recruited and categorized into four similarly sized groups based on contact lens wear (no lens wear, conventional daily wear hydrogels, silicone hydrogel lenses worn on a continuous basis, and gas-permeable contact lenses). Sets of measures, in random order and from both eyes whenever possible, were made using a phenol red thread (PRT) test over 15 seconds (open eye), biomicroscopy to assess tear meniscus height (TMH) from a perpendicular perspective using a 0.05-mm resolution graticule, and a borosilicate glass micropipette used to collect a 5-microL sample of tears for assessment of osmolality by vapor pressure measures. RESULTS: For the complete group of subjects, the TMH data averaged 0.22 +/- 0.07 mm; the average PRT wetting length was 18.0 +/- 6.1 mm; and the tear osmolality averaged 317 +/- 28 mOsm/kg. The intereye differences averaged 0.04 mm for TMH, 3.7 mm for PRT, and 15 mOsm/kg for tear osmolality. There were no detectable sex-related differences in the measures. Compared with the control group (average, 0.25 mm), the TMH data showed a trend to be lower in daily hydrogel (0.21 mm) and silicone hydrogel (0.20 mm) lens wearers, but not in gas-permeable lens wearers (0.24 mm). PRT data was bimodally distributed, with the control group showing slightly higher (average, 21.1 mm) wetting compared with hydrogel lens wearers (16.7 and 17.4 mm) and gas-permeable lens wearers (average, 17.3 mm). Hydrogel (319 mOsm/kg for both groups) and gas-permeable lens wearers (average, 324 mOsm/kg) had higher tear osmolality measures compared with the control group (average, 305 mOsm/kg). Although some of the differences approached statistical significance, any statistical differences were evident only after outliers were removed. However, on pooling all data, there was a statistically significant positive correlation between TMH and open-eye PRT measures (P < 0.001) and an indication of a negative correlation between open-eye PRT and tear osmolality measures. CONCLUSIONS: Even contemporary contact lens wear can have a small but measurable impact on the precorneal tear film osmolality or volume. The changes are internally consistent and, overall, support the idea that the PRT test provides a useful measure of tear meniscus volume.

Applying wavefront sensors and corneal topography to keratoconus.

We report preliminary results from a study to create custom optics (contact lenses) for persons with the eye disease Keratoconus. Custom optics are intended to correct for higher order aberrations which cannot currently be corrected with conventional contact lenses. A lens design algorithm has been developed that utilizes both wavefront sensor data and corneal topography data. The lenses will be formed from thick, pre-fabricated soft contact lenses using laser ablation. Preliminary ablation of these lenses is demonstrated using a femptosecond Ti: Sapphire (Ti:Al2O3) laser system.