The measurement of intraocular pressure over positive soft contact lenses by rebound tonometry / Medición de la presión intraocular sobre lentes de contacto blandas positivas, mediante tonometría de rebote

Purpose: To investigate if the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) contact lenses (CL) is affected by the positive power of the CLs. Methods: The experimental group comprised 26 subjects, (8 male, 18 female). IOP measurements were undertaken on the subjects’ right eyes in random order using a Rebound Tonometer (ICare). The CLs had powers of +2.00D and +6.00D. Measurements were taken over each contact lens and also before and after the CLs had been worn. Results: The IOP measure obtained with both CLs was significantly lower compared to the value without CLs (t test; p<0.001) but no significant difference was found between the two powers of CLs. Conclusions: Rebound tonometry over positive hydrogel CLs leads to a certain degree of IOP underestimation. This result did not change for the two positive lenses used in the experiment, despite their large difference in power and therefore in lens thickness. Optometrists should bear this in mind when measuring IOP with the rebound tonometer over plus power contact lenses (AU)

Objetivo: Investigar si la precisión de las mediciones de la presión intraocular (PIO), utilizando la tonometría de rebote sobre las lentes de contacto (LC) desechables de hidrogel (etafilcon A), se ve afectada por la potencia positiva de dichas lentes. Métodos: El grupo experimental incluyó a 26 sujetos, (8 varones, 18 mujeres). Se realizó la medición de la PIO en los ojos derechos de los sujetos, de modo aleatorio, utilizando un Tonómetro de Rebote (ICare). Las LC tenían potencias de +2,00D y +6,00D. Se realizaron mediciones con cada lente de contacto, y también antes y después a su uso. Resultados: El valor de la PIO obtenido con ambas LC fue considerablemente menor al valor sin LC (t del test; p<0,001), aunque no se halló una diferencia significativa entre las dos potencias de las lentes. Conclusiones: La tonometría de rebote sobre las LC positivas de hidrogel origina un cierto grado de subestimación del PIO. Este resultado no sufrió variación entre las dos lentes positivas utilizadas en el experimento, a pesar de la gran diferencia de potencia, y por tanto del espesor de las lentes. Los optometristas deberían de tener en cuenta estos resultados en a la hora de medir el PIO con un tonómetro de rebote, con lentes de contacto de mayor potencia (AU)

Review of complications associated with contact lenses from unregulated sources of supply.

OBJECTIVE: To review existing studies and case reports regarding complications associated with contact lenses (CLs) from unregulated sources of supply and to identify any relevant trends. METHODS: A systematic literature search was performed to locate publications concerning complications associated with CLs obtained from unregulated sources of supply. RESULTS: A total of 23 articles were identified that represent 70 individual cases. All 8 of the pre-2006 case reports originated from the United States and the United Kingdom, whereas from 2006 onwards, only 2 of the 15 reports came from these locations. Over-the-counter supply accounted for 73% (51/70) of cases, whereas 17% (12/70) were borrowed or shared lenses and 6% (4/70) lenses were obtained through the Internet. Nearly, three quarters of patients (30/42, 71%) waited longer than 48 hours after the onset of symptoms before seeking medical attention; 10 patients waited longer than a week, and 5 longer than a month. Microbial keratitis (MK) was reported in 43 (61%) patients, with permanent damage occurring in 72% (31/43) of patients followed to conclusion. Known risk factors associated for MK were present in all cases irrespective of whether the patients developed MK. CONCLUSIONS: There are various reasons to presume that the unregulated supply of CLs might result in the use of inappropriate lenses, increase the risk of poorer lens hygiene, and militate against the prompt treatment of any consequent complications. There is some indication that the introduction of regulations to control the supply of plano CLs has alleviated the level of complications.

Contact lenses purchased over the internet place individuals potentially at risk for harmful eye care practices.

BACKGROUND: Individuals are increasingly purchasing contact lenses over the Internet. No studies exist regarding Internet purchase of contact lenses and eye care health practices. METHODS: One hundred fifty-one college students were surveyed regarding contact lenses purchase category (doctor's office, store, Internet). Pearson chi-square analyses compared purchase category with responses regarding U.S. Food and Drug Administration (FDA) recommendations for purchasing contact lenses online. Analysis of variance compared contact lenses purchase category with the Time Pressure Scale (TPS). Also, correlation analyses compared the TPS with Internet eye-health statements. RESULTS: Contact lens purchase categories included doctor's office (43.0%), store (55.0%), and Internet (22.5%), with individuals purchasing at multiple venues. With regard to the FDA recommendations, those who purchased contact lenses at a doctor's office more often adhered to the recommendations, whereas those who purchased contact lenses at a store or the Internet did so less often. Those who purchased contact lenses over the Internet had significantly higher TPS scores. In addition, higher TPS scores were significantly correlated with various statements regarding the Internet. CONCLUSIONS: Those who purchase contact lenses via the Internet or store do not follow a number of FDA contact lenses recommendations. Also, those with higher TPS scores trust possible non-evidence-based contact lenses Internet information. Implications with regard to the Fairness to Contact Lens Consumers Act are discussed.

Assessment of central corneal thickness in extreme myopic eyes

Purpose: To study the central corneal thickness values in two groups of extreme myopic patients (cycloplegic spherical equivalent refraction >=-12 diopters) and in a control group. Methods: We carried out ultrasonic pachymetry with the DGH 2000 AP ultrasonic pachymeter (DGH Technology, Inc., San Diego, CA, USA). Group I (n=45) was made up of patients with spherical equivalent refraction ranging from -12.00 to -18.00 diopters; group II (n=25) with spherical equivalent refraction > -18.00 diopters, and the control group (n = 34) was made up of patients with spherical equivalent refraction ranging from -0.25 to -3.00 diopters. Results: Mean central corneal thickness (mean±SD) was 531±42 ?m, 551±52 ?m and 538±35 ?m in groups I, II and controls, respectively (p=0.193). No significant differences between women and men were found in group I (p=0.314), group II (p=0.071) and the control group (p=0.113). No significant differences among age subgroups were found in group I (p=0.989), group II (p=0.641) or in the control group (p=0.397). Conclusions: In extreme myopic eyes there is a slight tendency for central corneal thickness to increase in the presence of higher degrees of myopia. Nevertheless, central corneal thickness in extreme myopic patients is similar to that noted in non-extreme myopic patients (AU)

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Learning the "numbers game" of today's contact lens fitting: clinical and business pearls.

A "chair time model" for contact lens pricing is a valuable administrative tool. Relative sagittal depth is an easy comparison to use when evaluating the theoretical fit of one soft lens versus another. Biological oxygen apparent transmissibility (BOAT) and a calculated value of oxygen transmissibility (Dk/L) are two totally different assessments and the significance of BOAT will need to be clinically tested over time.

Sociodemographic differences in access to vision care among adults in the United States, 1974-1975.

Access to refractive care is examined by comparing uncorrected and corrected (with eyeglasses or contact lenses) distance visual acuity across eight race-sex-economic status groups. Of those with less than 20/20 uncorrected distance visual acuity, the age-adjusted proportion using corrective lenses is examined across these sociodemographic groups to assess unmet need in vision care. Measurements of distance visual acuity were obtained for 2,828 adults aged 25-74 years from the national probability sample selected for the 1974-1975 National Health and Nutrition Examination Augmentation Survey. Questionnaire responses were collected on usual correction. Individuals were classified by race, sex, and economic status. Weighted least squares categoric data analysis showed that blacks, males, and nonpoor persons have a higher proportion with 20/20 uncorrected distance vision than whites, females, and poor persons. Individuals who are white, male, and nonpoor are more likely to have 20/20 corrected distance vision than their counterparts.

Contact lenses for laser applications.

Contact lenses for anterior and posterior segment laser applications are described. Commercially available lenses are classified according to design, application, manufacturer and cost.