Rigid Gas-permeable Contact Lens Wear Research Articles

Impact of soft and rigid gas-permeable contact lenses on visual performance in mesopic conditions.

Evaluation of visual quality in soft and rigid gas-permeable contact lens wearers, with an emphasis on twilight vision. To assess the visual acuity and visual performance at dusk before and after soft and rigid gas-permeable contact lens (CL) correction in healthy subjects. This prospective study was conducted in a tertiary eye-care center. Sixty eyes corrected with soft contact lenses (SCLs) and 30 eyes with rigid gas-permeable contact lenses (RGPCLs) were enrolled in this study. Patients underwent corrected distance visual acuity with spectacles (CDVAs), corrected distance visual acuity with contact lenses (CDVAcl), and twilight vision (TV) testing (Vista Vision Far-Pola, DMD MedTech charts). Parameters were evaluated before and after the CL fitting and repeated 3 months after the baseline visit. MedCalc for Windows, version 11.4 (MedCalc Software, Ostend, Belgium). Rigid gas-permeable CL wear showed significant improvement in CDVAcl compared to wearing spectacles on both visits ( P = 0.0039 and P = 0.0003, respectively). TV with CLs was significantly better in both groups compared to the TV with spectacles at the baseline visit ( P = 0.0011 in SCL group; P = 0.0001 in RGPCL group), and at the follow-up visit, this significance was proven for the RGPCL group ( P = 0.001). Also, spectacle TV showed a significant improvement on the follow-up visit ( P = 0.0022 in SCL group; P = 0.0269 in RGPCL group). Contact lens wear improves visual performance compared to spectacles. TV results showed superiority of CLs compared to the spectacles, without a statistical difference regarding the CL type.

Parental Corneal Tomographic and Biomechanical Characteristics of Patients With Keratoconus

To investigate the hereditability of corneal tomographic and biomechanical parameters in keratoconus (KC). Prospective cohort study. This study was conducted at Qingdao Eye Hospital of Shandong First Medical University in Qingdao, China. Forty-four patients with KC and their biological parents (n=88) were recruited as the study group. The control group consisted of 84 healthy adults with matched age and gender. Both eyes of each participant underwent clinical examinations, and 1 eye was selected for statistical analysis. Exclusion criteria were as follows: individuals with glaucoma, ocular surgery, systemic diseases known to affect the eyes, or poor cooperation during examination. Subjects were asked to discontinue soft contact lens (CL) wear for 2 weeks and rigid gas permeable CL wear for 4 weeks before ocular examination. All participants underwent a comprehensive assessment including Pentacam Scheimpflug tomography, Corvis ST, visual acuity, refraction examination, axial length, and slitlamp examination for both eyes. Individuals presenting with KC manifestations in at least 1 eye were classified as having KC. A total of 9 Pentacam indices including keratometry in the flat/steep meridian (K1/K2), maximal keratometry (Kmax), thinnest point pachymetry (TP), and maximum/average Ambrósio relational thickness (ARTmax/ARTave), anterior and posterior surfaces elevation of the cornea (Ef/Eb) and total deviation value (Final D), and 21 biomechanical indices were collected. Associations of these factors with KC were evaluated using multiple comparison and binary logistics regression analyses. Two parents (2.27%) from 2 different families were diagnosed with KC. Parents of patients with KC had thinner corneas with altered corneal biomechanical parameters compared with healthy controls (P < .05). The combined tomographic and biomechanical index demonstrated the highest discriminatory power (area under the receiver operating characteristic curve 0.785) and strong specificity (84.5%). Parental corneal tomographic and biomechanical index, Corvis biomechanical index, and TP were identified as the major influential factors for KC in their offspring by logistic regression analysis, with a 73.3% accuracy in identifying offspring with KC. Parental corneal tomographic and biomechanical properties of patients with KC suggest a possible predisposition to KC. A combination of tomography and corneal biomechanics can be helpful in predicting the incidence rate of KC in the offspring of patients with subclinical KC.

A proposed methodology for conducting a remote rigid gas permeable contact lens consultation

PurposeCOVID-19 spread to numerous countries, overwhelming healthcare systems and economies worldwide. COVID-19 restrictions have prevented patients from attending consultations in person and led to the further development of telemedicine to provide health care. The situation also applies to contact lens (CL) practitioners and their patients; telemedicine enables practitioners to provide patients with regular and continuing care. This study aimed to investigate available tools to enable continuing care for rigid gas permeable (RGP) CL wearers who are unable to attend face-to-face consultations. MethodsThe study consists of three components. Firstly, an approach to enable the assessment of a patient’s CL fitting and cornea remotely. Secondly, to find an affordable and reliable method to obtain a patient’s visual acuity (VA), and thirdly, to develop a questionnaire to provide practitioners with information to deliver optimal patient care. ResultsThe use of a macro lens, smartphone, and auxiliary materials enables high-quality images of the anterior eye and RGP CL to be obtained. Two free and validated smartphone applications (apps) for VA measurements were identified which are available on Android and iOS systems. Two questionnaires were also developed to enable practitioners to obtain additional patient information to facilitate optimal patient care. ConclusionThis study has developed the components of a remote CL consultation to enable patients who cannot attend scheduled appointments to receive care and advice to ensure the safety of their RGP CL wear. The tools involved in this study are low-cost, affordable, and an adjunct, not a substitute, for face-to-face consultations.

Investigation of contrast visual acuity with rigid gas permeable contact lenses after penetrating Keratoplasty

BackgroundTo investigate the effects of rigid gas permeable contact lens (RGP-CL) wear on contrast visual acuity in patients after penetrating keratoplasty.MethodsNineteen patients (19 eyes), aged 30.45 ± 5.83 years, who had received penetrating keratoplasty and were successfully fitted with RGP-CLs at our hospital from July 2017 to June 2018 were included. Contrast visual acuities at 100%, 25%, and 10% with spectacles and RGP-CLs were analyzed using the Chi-square test. The wavefront aberrations at the anterior surface of the cornea before and 1 month after RGP-CL wear were compared using the matched sample t-test.ResultsThe mean best spectacle-corrected visual acuities were 0.390 ± 0.135 logMAR, 0.706 ± 0.182 logMAR, and 0.952 ± 0.223 logMAR at the 100%, 25%, and 10% contrast levels, respectively, which were significantly lower than the RGP-CL-corrected visions at the three levels (0.255 ± 0.133 logMAR, 0.488 ± 0.168 logMAR, and 0.737 ± 0.159 logMAR; all P < 0.001). The vision losses with RGP-CLs were 0.231 ± 0.099 logMAR and 0.466 ± 0.094 logMAR at the 25% and 10% contrast levels, respectively. The Zernike spherical aberration Z04 was reduced from 3.734 ± 1.061 μm to 2.622 ± 0.725 μm after wearing the RGP-CLs (P ≤ 0.001). The astigmatism parameters of Z− 22 and Z22 were also reduced from 3.761 ± 2.309 μm and 3.316 ± 2.147 μm to 2.637 ± 1.722 μm and 2.016 ± 1.184 μm, respectively (P < 0.05).ConclusionFor post-keratoplasty patients, RGP-CLs can help to improve visual performance, especially low contrast visual acuity. The improvement may be related to the reduction of corneal aberrations, mainly the spherical and astigmatism aberrations.

Factors Affecting Long-Term Compliance with Rigid Gas-Permeable Contact Lens Wear in Patients with Keratoconus.

The purpose of the study was to investigate the factors affecting long-term compliance with rigid gas-permeable contact lens (RGPCL) wear in patients with keratoconus (KC). A total of 189 patients with KC (374 eyes) were included in the study, and were divided into two groups: the compliant group and the non-compliant group. Corneal topographic measurements, refractive results, and RGPCL parameters were compared between the two groups. A vision-related quality of life questionnaire was completed by all of the patients. The results demonstrated that patients diagnosed with bilateral KC were more compliant with RGPCL wear than patients diagnosed with unilateral KC (p = 0.0167). There were no significant differences between the compliant and non-compliant groups in terms of their corneal topographic measurements, refractive results, RGPCL parameters, or corneal cross-linking surgery history (all p > 0.05). In contrast, KC patients’ subjective experience with RGPCL wear—including visual acuity (p = 0.006), overall satisfaction (p < 0.001), quality of life (p < 0.001), and good adaptation during the short-term (p < 0.001)—had a significant effect on the long-term compliance with RGPCL wear. In conclusion, patients’ subjective experiences, rather than their ocular biometrics, significantly influence their long-term compliance with RGPCL wear.

Corneal tomographic changes during corneal rigid gas-permeable contact lens wear in keratoconic eyes

Background/AimsWe aimed to investigate the refractive changes in the posterior corneal surface in keratoconus (KC) associated with wearing spherical corneal rigid gas-permeable contact lenses (corneal GPs) with apical touch or...

The Challenge of Contact Lens Visual Rehabilitation for Open Globe Injuries in Children Under 5 Years of Age.

To investigate the clinical course of children younger than 5 years old who underwent rigid gas-permeable (RGP) contact lens (CL) wearing as visual rehabilitation of open globe injuries (OGIs) in Japan. This retrospective case series involved six eyes of six children (four boys and two girls) with OGIs. The mean patient age at injury was 4.0±0.83 SD (range: 2.5-5 years), and the mean follow-up period was 42.9 months (range: 31.6-52.8 months). In each child, data regarding injury type, ocular surgery performed, outcomes of amblyopia management (including best-corrected visual acuity [BCVA] with RGP CL or spectacles), the RGP CL-wear training period, and rate of continuous RGP CL-wear were analyzed. Trauma type was penetrating injury (four eyes) and globe rupture (two eyes). All six cases showed lens penetration, and underwent corneal suture, lensectomy, and pars plana vitrectomy under general anesthesia. The mean RGP CL-wear training period was 3.5 months, and only one of the six cases discontinued RGP CL use. The mean BCVA with spectacles and with RGP CL was LogMAR: 1.52±0.41 (range 1.00-2.00) and 0.73±0.41 (range: 0.30-1.15), respectively. In all patients, except in one case in which strabismus developed, BCVA improved with RGP CL wear more than 0.2 logMAR compared with that with spectacles. Although the training period for RGP CL-wear is long in pediatric patients with OGIs, the treatment can be effective for refractive problems and for preventing the development of strabismus.

Effect of long-term rigid gas-permeable contact lens wear on keratoconus progression

Background/aimsTo investigate the chronological corneal changes associated with long-term rigid gas-permeable contact lens (RGP-CL) wear in patients with keratoconus (KC).MethodsClinical records of 405 patients with KC or with KC suspect...

Profile and Performance of Rigid Gas Permeable and Scleral Lenses on Keratoconic Patients in the Developing Contact Lens Practice Settings

Purpose: To present the profile of keratoconic contact lens wearers, alongside with performance of corneal and scleral rigid gas permeable (RGP) at different stages of keratoconus based on limited diagnostic resources. Methods: 5-year Clinical records of keratoconic corneal and scleral RGP contact lens wearers were retrieved. Data on age, gender, visual acuity (VA), refraction (RE), stage of keratoconus and mode of correction among other variables were obtained for analysis. Information pertaining to the outcome in pre and post-fit at different severity was determined. Results: A total of 124 medical records were analyzed, with the age (20.86 ± 9.50 years), gender (58.9% male and 41.1% female), Laterality (57.3% bilateral, 26.6% right eye and left eye as 16.1%) and ethnicity (91.1% Africans and 8.9% Asians). There were no significant differences in effects of lenses (RGP and Scleral lenses) across three stages in visual acuity and in three stages of severity HRGP (2) = 1.05, p = 0.59; HScleral (1) = 2.24, p = 0.134. Similar non-significant effect was observed in refractive error correction HRGP (2) = 1.62, p = 0.44: HScleral (1) = 1.143, p = 0.285. Conclusion: The profile of KC contact lens wearer was comparable to other studies in developing setting. Keratoconic grading should be based on available resources. Corneal rigid gas permeable and scleral lenses were beneficial to keratoconic patients in respect of refractive error correction and visual improvement to keratoconic patient.

Effects of Corneal Scars and Their Treatment With Rigid Contact Lenses on Quality of Vision.

To study the effects of corneal scars and the treatment of these scars with rigid gas-permeable (RGP) contact lenses on quality of vision including straylight. Visual effects were related to scar characteristics such as size and grade. Straylight and best-corrected visual acuity were measured in 23 patients with corneal scars during and after RGP contact lens wear. Contralateral eyes were used as controls, and age-normal values in case of bilateral scars. Straylight measurements were performed using the compensation comparison method of the Oculus C-Quant instrument. Scarred eye straylight values were 1.53 log(s) without contact lens and 1.60 log(s) with contact lens (P=0.043). Healthy eyes without contact lens had a mean straylight value of 1.13 log(s), corresponding to age-normal values. Contact lens wear increased straylight in healthy eyes to 1.26 log(s) (P<0.001). Visual acuity improved from 0.66 logarithm of minimal angle of resolution (logMAR) to 0.19 logMAR with contact lens wear in eyes with a corneal scar (P<0.001). Corneal scars can have a strong effect on quality of vision by diminishing visual acuity and increasing straylight. The increase in straylight from corneal scars on its own can lead to a serious visual handicap. Contact lens treatment did not improve straylight, but showed a slight worsening. As the recovery of visual acuity with contact lens wear far exceeded straylight increase, contact lenses remain a clinically useful treatment option in most patients with corneal scars.

Patient-related barriers to Rigid Gas Permeable (RGP) lens wear among keratoconus patients in Jordan.

To assess potential patient-related barriers to rigid gas permeable (RGP) lens wear for vision rehabilitation in a sample of keratoconus (KC) patients in Jordan. Barriers for RGP contact lens wear among KC patients were discussed and specified by a focus group which consisted of five optometrists who are involved in contact lens practice. The focus group addressed potential barriers for RGP lens wear from the patient's perspective. The identified barriers were then used to design the final questionnaire used in the study. The questionnaire consisted of 8 questions which ask the participant to rate, within a 5-points scale (1: strongly disagree to 5: strongly agree), how each suggested item is considered a barrier for RGP lens wear. 204 KC patients (86 females, 118 males) were involved in a semi-structured interview to answer the questionnaire. The average age of participants was 30.85 (±8.74) years old and ranged from 18 to 62 years. The average age of diagnosis of KC (±standard deviation) is 21.96 (±7.22) years old with a range of 12-52 years. All participants reported that they had never tried RGP lenses for their vision rehabilitation; however, other management options were reported such as glasses, keratoplasty, collagen cross linking and Intacs. The mean score of total barriers to RGP wear was high at 3.8 (±0.4) (out of 5). The major identified barriers were: lack of awareness of the benefits of RGP lenses, fear of possible lens complications, lack of medical insurance and high cost of the lens. The study reveals that several barriers were identified as prevalent. Consequently, there is an imperative need to adopt better planning strategies for management protocol of KC in order to assure best eye care service for KC patients in Jordan.

The influence of rigid gas permeable lens wear on the concentrations of dinucleotides in tears and the effect on dry eye signs and symptoms in keratoconus.

To evaluate the signs and symptoms of dry eye and dinucleotide secretion in tears of keratoconus patients (KC) and the potential effect of rigid gas permeable (RGP) contact lens wear. Twenty-three KC patients and forty control subjects were enrolled in this study. Signs of dry eye including tear volume, tear stability and corneal staining along with symptoms were assessed using the McMonnies questionnaire. Tears were collected using Schirmer strips, and dinucleotide concentrations in collected tears measured using high pressure liquid chromatography. Values obtained in KC and controls were compared. The effect of contact lens wear in KC was also assessed. KC eyes showed a significantly lower tear volume compared to controls, shorter tear break up time (TBUT), higher corneal staining and higher McMonnies dry eye questionnaire scores (p<0.05). When compared with non-wearers, KC contact lens wearers showed significantly higher symptoms, lower Schirmer and TBUT values (p<0.05). Concentration of Ap4A (0.695±0.304μM vs. 0.185±0.178μM) and Ap5A (0.132±0.128μM vs. 0.045±0.036μM) were higher in KC compared to controls (p<0.001) and only Ap4A was statistically higher in RGP wearers compared to non-wearers (0.794±0.478μM vs. 0.417±0.313μM) (p<0.05). Signs and symptoms of dry eye as well as concentrations of Ap4A and Ap5A were markedly increased in KC patients compared to controls. Moreover, Ap4A and symptoms of dry eye were statistically higher in RGP wearers compared to non-wearers. This seems to indicate that factors such as RGP contact lens wear might exacerbate the clinical condition of dry eye.

Acanthamoeba Keratitis among Rigid Gas Permeable Contact Lens Wearers in the United States, 2005 through 2011

To describe the clinical presentation and outcomes of Acanthamoeba keratitis (AK) in rigid gas permeable (RGP) contact lens wearers and to identify modifiable risk factors. Case-control investigation. Patients were RGP contact lens-wearing United States residents with a diagnosis of AK from 2005 through 2011. Controls were RGP contact lens wearers with no history of AK who were at least 12 years ofage. Patients were identified during 2 multistate AK outbreak investigations. Controls from the first investigation in 2007 were identified using a reverse address directory. In the second investigation, controls were recruited from participating ophthalmology and optometry practices. Patients and controls were interviewed by phone using a standardized questionnaire. Odds ratios (ORs) and Fisher exact P values were calculated to assess risk factors associated with infection. Acanthamoeba keratitis, a rare eye disease primarily affecting contact lens wearers, is caused by free-living amebae, Acanthamoeba species. We identified 37 patients in the 2 investigations, 10 (27%) from the 2007 investigation and 27 (73%) from 2011. There were 17 healthy controls, 9 (53%) from 2007 and 8 (47%) from 2011. Among patients, 9 (24%) wore RGP lenses for orthokeratology or therapeutic indication; no controls wore RGP lenses for these indications. Significant risk factors for AK were wearing lenses for orthokeratology (OR, undefined; P= 0.02), sleeping while wearing lenses (OR, 8.00; P= 0.04), storing lenses in tap water (OR, 16.00; P= 0.001), and topping off contact lens solution in the case (OR, 4.80; P= 0.01). After stratifying by use of RGP lenses for orthokeratology, storing lenses in tap water and topping off remained significant exposures. Nearly one quarter of patients were orthokeratology wearers. Using tap water to store RGP lenses and topping off solution in the lens case were modifiable risk behaviors identified in RGP wearers who wore lenses for both orthokeratology and nonorthokeratology indications. Rigid gas permeable wearers should avoid exposing their lenses to tap water and should empty their cases and use fresh lens solution each time they take out their lenses.

Assessment of Anterior, Posterior, and Total Central Corneal Astigmatism in Eyes With Keratoconus

To investigate the magnitudes and the axis orientations of anterior, posterior, and total central corneal astigmatism in eyes with keratoconus. Retrospective case series. This study comprised 137 eyes of 137 keratoconic patients (97 men and 40 women; mean age ± standard deviation, 36.9 ± 12.2 years). The magnitude and the axis orientation of each corneal astigmatism were determined with a rotating Scheimpflug system. The mean magnitudes of anterior, posterior, and total central corneal astigmatism were 3.93 ± 2.74 diopters (D), 0.93 ± 0.64 D, and 3.90 ± 2.75 D, respectively. With-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism of the anterior corneal surface was found in 90 eyes (65.7%), 33 eyes (24.1%), and 14 eyes (10.2%), respectively, whereas the corresponding astigmatism of the posterior corneal surface was found in 14 eyes (10.2%), 15 eyes (10.9%), and 108 eyes (78.8%), respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r= 0.769, P< .001). The mean magnitudes of anterior and posterior corneal astigmatism were approximately 4 D and 1 D, respectively, in eyes with keratoconus. Approximately 65% and 80% of eyes showed that WTR anterior astigmatism and ATR posterior astigmatism, respectively. The presence of posterior corneal astigmatism is not necessarily negligible for the accurate astigmatic correction of toric intraocular lens implantation or rigid gas-permeable contact lens wear for keratoconus.

Effects of rigid contact lenses on optical coherence tomographic parameters in eyes with keratoconus

BackgroundThe aim was to evaluate the effect of irregular astigmatism on the retinal nerve fibre layer (RNFL), macular thickness and ganglion cell analysis obtained by spectral domain optical coherence tomography (OCT) in eyes with keratoconus.MethodsFifty‐two eyes of 31 patients (20 females) with keratoconus that required correction of irregular astigmatism with rigid gas‐permeable (RGP) contact lenses were included to this study. The average, superior, nasal, inferior, temporal and 12 clock hour sector's RNFL, ganglion cell and macular thickness analyses before and 30-minutes after RGP contact lens (Rose K2 ‐Menicon Z material, David Thomas Contact Lenses Ltd, Northampton, United Kingdom) wear were performed to all patients with Cirrus HD spectral domain optical coherence tomography.ResultsThe average thickness of the retinal nerve fibre layer, the thickness at the nasal quadrants and 1‐2‐3‐4 o'clock hour sectors and mean signal strength were increased significantly by RGP contact lens wearing independent of the stage of keratoconus. Central sub‐field thickness increased after correction with RGP contact lens (p = 0.037). After wearing RGP contact lenses, changes on ganglion cell analysis were not significant (all p values ≥ 0.111).ConclusionsOCT is a widely used device for retinal nerve fibre layer and macular thickness evaluation in patients with glaucoma and macular diseases. The study demonstrates that OCT parameters such as retinal nerve fibre layer, central sub‐field thickness and mean signal strength are affected by irregular astigmatism. Correction of irregular astigmatism with RGP contact lenses should be recommended before analysing keratoconic eyes to obtain optimum results on OCT measurements.

Evaluation of Contact Lens–Induced Changes in Keratoconic Corneas Using In Vivo Confocal Microscopy

To quantitatively analyze laser scanning in vivo confocal microscopy (IVCM) images of all corneal layers in contact lens-wearing and noncontact lens-wearing keratoconus patients. The study population included rigid gas permeable (RGP) contact lens-wearing keratoconus patients (group 1; N = 29), keratoconus patients who did not wear contact lenses (group 2; N = 30), and subjects who neither had keratoconus nor wore contact lenses (group 3; N = 30), with groups 2 and 3 matched to group 1 by age and sex. The central cornea was examined with IVCM in all subjects. The mean duration of contact lens wear was 5.50 ± 3.68 years (range, 2-15 years). Eyes with keratoconus showed significantly lower basal epithelial cell and anterior and posterior stromal keratocyte densities, as well as subbasal nerve fiber density, nerve branch density, and nerve fiber length compared with healthy control subjects. Furthermore, compared with group 2, group 1 had significantly lower basal epithelial cell density (4920 ± 476 cells/mm(2) vs. 4503 ± 461 cells/mm(2), P = 0.001) and anterior stromal keratocyte density (561 ± 91 cells/mm(2) vs. 464 ± 55 cells/mm(2), P < 0.001), but there was no significant difference for posterior stromal keratocyte density (P = 0.808), endothelial cell density (P = 0.699), or subbasal nerve fiber density (P = 0.142), nerve branch density (P = 0.614), and nerve fiber length (P = 0.850). Significant corneal microstructural abnormalities were observed in eyes with keratoconus. RGP contact lens wear was associated with a further reduction in the basal epithelial cell and anterior stromal keratocyte densities, but with no effect on posterior stromal keratocyte density, endothelial cell density, or corneal nerve morphology.

ZERNIKE ASTIGMATISM AND VISUAL PERFORMANCE IN MYOPIC EYES BY RIGID GAS PERMEABLE CONTACT LENSES WEAR

Purpose: To investigate the effects of rigid-gas-permeable contact lens (RGP-CL) wear on Zernike astigmatism and visual performance in myopic eyes. Methods: A wavefront sensor was used to evaluate Zernike astigmatism for 21 eyes with minimum astigmatism and 18 eyes with moderate astigmatism under three different modes of refractive correction: the RGP-CL, spectacle lens correcting spherical equivalent (SL) and spectacle lens fully correcting spherical error and astigmatism (fSL). Contrast visual acuity was assessed with a VA tester at four contrast levels and two luminance backgrounds. Results: Compared to the SL wear, RGP-CL wear changed the main axis astigmatism [Formula: see text] from -0.09 ± 0.34 to 0.34 ± 0.22 for the minimum astigmatism group, while the contrast VA was improved about 0.05 LogMAR (F = 8.06, p &lt; 0.01). For the group with moderate astigmatism, significant reduction in [Formula: see text] was found for both fSL wear (t = 4.78, p &lt; 0.001) and RGP-CL wear (t = 6.29, p &lt; 0.0001). The changes in astigmatism were significantly correlated between the fSL and RGP-CL wears (r = 0.897, p &lt; 0.0001 for [Formula: see text]; and r = 0.643, p = 0.004 for [Formula: see text]. Contrast VA was significantly improved for both fSL and RGP-CL wears and the improvements were significantly correlated between each other for all four contrast levels and two backgrounds. Conclusion: RGP-CL wear induces astigmatism for the eyes with minor astigmatism probably due to a correction of corneal astigmatism and thus a manifesting of the lens astigmatism. For the astigmatic eyes, RGP-CL wear has similar effect on correcting astigmatism as the spectacle lens wear with spherical-cylinder correction and also produces similar visual improvement.

Cataractes congénitales : correction de l’aphaquie par lentilles de contact rigides

To describe follow-up and evaluate functional results of rigid gas-permeable contact lens wear for the correction of aphakia in infants after surgery for congenital cataract. This retrospective study was performed on 23 eyes of 17 children (12 boys and five girls), between three days and 36 months of age (median 3.5 months), undergoing cataract extraction without primary intraocular lens implantation and fitted only with Menicon(®) Z material contact lenses. Initial fitting visits included history and family education. Subsequent examinations were performed at eight days, 15 days, 1 month, 6 months and 1 year. The four main parameters studied were fit characteristics, ease of manipulation, ocular integrity and lens integrity. Concurrently, functional results (visual acuity, oculomotor balance) and various prognostic factors (associated pathology, age at time of surgery, cataract density, unilaterality versus bilaterality, postoperative complications) were evaluated. Rigorous systematic amblyopia rehabilitation was performed. At the one-month exam, 60% of parents demonstrated proficiency with manipulating the lens. On one-year follow-up, three cases of failure were attributable to difficulties with lens manipulation. At one year, one infectious complication was detected. The lens material demonstrated good resistance to breakage (9% at one month) and only a mild tendency toward deposits (few or no deposits in 95% of cases at 1 month). With regard to visual outcome, among the children old enough to cooperate, visual acuity was better than 3/10 for nine out of 12 eyes, of which five eyes were 10/10. With regard to alignment, we noted 12 cases (70.6%) of strabismus postoperatively (ten esotropia, two exotropia). The factors predictive of good visual acuity correlated with those described in the literature: partial cataract, bilateral cataract, and absence of postoperative oculomotor disturbance. The characteristics of rigid gas-permeable contact lenses provide safety and efficacy in aphakic infant eyes. They represent an attractive alternative to primary intraocular lens implantation in congenital cataract.

Changes in Refraction, Ocular Aberrations, and Corneal Structure After Suspending Rigid Gas-Permeable Contact Lens Wear in Keratoconus

This study reports on changes in visual acuity, ocular higher-order aberrations, and refraction after suspending rigid gas-permeable lens wear for 1 week in 15 patients with moderate to severe keratoconus. Alterations in the anterior surface, central corneal powers and axes, and central corneal thickness were also explored. Scheimpflug photography and Hartmann-Shack aberrometry were performed at 2 visits, 7 days apart, after the patients had removed their habitual contact lenses. Subjective refraction and both high- and low-contrast logarithm of the minimum angle of resolution visual acuities were also recorded at both visits. Reductions in both high-contrast visual acuity (P = 0.001) and low-contrast visual acuity (P = 0.002), along with an increase in third-order root mean square aberrations (P = 0.008), occurred after rigid gas-permeable lens wear was suspended in these patients with keratoconus. However, no significant changes in subjective refraction were found over the 1-week period (P ≥ 0.10). Significant correlations were observed between third-order coma root mean square aberrations and the measured high-contrast (r(p) ≥ 0.59; P ≤ 0.02) and low-contrast visual acuities (r(P) ≥ 0.61; P ≤ 0.015). In addition to increases in the anterior surface central corneal powers (P ≤ 0.02), a reduction in central corneal thickness also was found between the 2 visits (P = 0.00016). Changes in the optical and structural parameters of the keratoconic cornea occur after suspending rigid gas-permeable contact lens wear. This information may be of interest to practitioners concerned with prescribing aberration-controlling soft contact lenses for such patients.

The short-term effects of PMMA and RGP contact lens wear on keratometric behaviour: a pilot study*

This article represents the preliminary findings of a larger study that included 24 subjects that were equally divided into three groups, namely, the PMMA (polymethyl methacrylate) group, the RGP(rigid gas permeable) group and the control group. The aim of this study was to establish the short term effects (if any) of PMMA and RGP contact lens wear on keratometric behaviour. A controlsubject was also included in the study to establish a reference fornormal diurnal changes in keratometric behaviour. Fifty successive auto-keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the first subject in the PMMA group and the first subject in the RGP group (experimental samples). Fifty successive auto-keratometric measurements were also taken on the first subject of the control group before and immediately after three hours of no lens wear (control sample). Data collected were analysed using multivariate statistical methods that in the past have been used infrequently in this area of study. This investigation revealed that, at least in these two randomly selected subjects, rigid contact lens wear appears to influence keratometric behaviour (PMMA contact lenses more so than RGP contact lenses). (S Afr Optom 2010 69(4) 173-181)