Rigid Gas Permeable Research Articles

Symptoms and Signs in Rigid Gas Permeable Lens Wearers During Adaptation Period

To evaluate neophyte contact lens wearers' fitting to rigid gas permeable (RGP) contact lenses in terms of wearing time, tear volume, stability, corneal staining, and subjective ratings, over a 1-month period of time. Twenty-two young healthy subjects were enrolled for wearing RGP on a daily wear basis. The participants included in this study never wore contact lenses and showed a value under 10 in McMonnies Questionnaire. Contact Lens Dry Eye Questionnaire, Visual Analog Scales, Schirmer test, tear film break-up time (BUT), and corneal staining grading were performed. Follow-up visits were scheduled at 1, 7, 15, and 28 days. Six subjects dropped out due to discomfort from the study before 1 month (27% of discontinuation rate). Successful RGP wearers (16 participants) achieved high levels of subjective vision and reported comfort scores of approximately 9 of 10 between 10 and 15 days. They reported wearing their lenses for an average of 10.12±2.43 hr after 1 month of wear. Conversely, unsuccessful wearers discontinued wearing the lenses after the first 10 to 15 days, showing comfort scores and wearing time significantly lower compared with the first day of wear. Schirmer test showed a significant increase at 10 days (P<0.001), and the BUT trends decreased after the first week of wear in unsuccessful group. Symptomatology related with dryness and discomfort, detected during the first 10 days of the adaptation, may help the clinician to predict those participants who will potentially fail to adapt to RGP lens wear.

A retrospective analysis of vision correction and safety in keratoconus patients wearing Toris K soft contact lenses.

The purpose of this study was to investigate the efficacy and safety of the Toris K silicone hydrogel contact lens (SwissLens; Prilly, Switzerland) in keratoconus patients. A database with information on 50 keratoconus patients (64 eyes) fitted with Toris K soft contact lenses over a 2-year period was retrospectively reviewed. Demographic data, prefitting refraction, the reason for choosing the Toris K soft contact lens, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best-corrected visual acuity with a rigid gas permeable lens (BCVA RGP), best-corrected visual acuity with the Toris K lens (BCVA Toris K), and complications were evaluated. The mean age±standard deviation at the time of fitting was 27.92±9.86years. The mean spherical refractive power was -4.62±6.53 dioptres, and the mean cylinder was -3.78±2.43 dioptres. The most common reason for using Toris K soft contact lenses was an inability to fit the patient with a RGP contact lens. There was a statistically significant difference between UCVA and BCVA Toris K (p=0.0001), as well as between BSCVA and BCVA Toris K (p=0.0001). However, there was no statistically significant difference between BCVA Toris K and BCVA RGP (p=0.20). Superficial punctate keratitis and giant papillary conjunctivitis were the most common complications. The Toris K contact lens is a viable alternative for the optical management of all grades of keratoconus. The Toris K soft contact lens is a promising alternative for the visual rehabilitation of keratoconus patients who cannot tolerate RGP lenses or achieve a good fit.

Effects of multipurpose solutions on the adhesion of Acanthamoeba to rigid gas permeable contact lenses.

To evaluate the effect of multipurpose contact lens care solutions (MPSs) on the adhesion of Acanthamoeba to rigid gas permeable (RGP) contact lenses. Acanthamoeba castellanii (AC) trophozoites were inoculated onto untreated RGP contact lenses (FP, Extra, or Menicon Z), and numbers of trophozoites adhering to lenses were counted under a phase contrast microscope at 18h post-inoculation (controls). Similarly, adhering trophozoites were counted at 6h post-inoculation on each of the three RGP lens types with one of three MPSs (Boston Simplus, Menicare Plus, and O2 Care). Scanning electron microscopic examinations were performed to compare lens surfaces. Adhesion of AC trophozoites to untreated FP was greater than to untreated Extra or Menicon Z. Surfaces of Extra and Menicon Z lenses were waxier, smoother, and more homogeneous than those of FP lenses. After treatment with Boston Simplus, adhesion of AC trophozoites was significantly reduced for all lens types as compared with controls (p<0.0001). Treatments with Menicare Plus or O2 Care reduced the number of adherent AC trophozoites significantly on FP lenses only as compared with controls (p<0.0001). The adhesion rates of AC trophozoites to RGP lenses depended on lens surfaces. Boston Simplus reduced the adhesion rate of AC trophozoites more than Menicare Plus or O2 Care. Appropriate RGP lens and MPS selection could decrease the prevalence of Acanthamoeba keratitis.

Clinical study on rigid gas permeable lenses decreasing the children's anisometropia caused by hyperopia

Clinical study on rigid gas permeable lenses decreasing the children's anisometropia caused by hyperopia

Comparison of Changes in Ocular Surface Status after Wearing Orthokeratologic and Rigid Gas Permeable Lens

Purpose: To evaluate the differences in dry eye and meibomian gland dysfunction (MGD) by comparing ocular surface status before and after wearing an orthokeratologic (OK) lens and rigid gas permeable (RGP) lens made of the same material. Methods: The ocular surface and meibomian gland statuses of 12 eyes of 12 OK lens wearers (OK lens group) and 16 eyes of 16 RGP wearers (RGP lens group) were evaluated before and 1 and 3 months after lens wearing. Ocular surface disease index (OSDI), tear film break-up time (TBUT), Schirmer’s test I, and ocular surface staining score were evaluated for ocular surface parameters. Meibomian gland function was evaluated by assessing lid margin abnormality, meibomian gland expressibility, and meibum quality. Results: TBUT and ocular surface staining score after 1 and 3 months of wearing an OK lens were significantly aggravated (p = 0.004, p < 0.001). The MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were aggravated after 1 and 3 months of wearing an OK lens (p < 0.001, p < 0.001, p < 0.001, p = 0.002). After 1 and 3 months of wearing an RGP lens, OSDI, TBUT, and ocular surface staining score were aggravated (all p < 0.001). The MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were aggravated after 1 and 3 months of wearing an RGP lens (all p < 0.001). MGD grade, lid margin abnormality, meibomian gland expressibility, and meibum quality were significantly more aggravated in the RGP lens group than in the OK lens group after 3 months (p < 0.001, p < 0.001, p = 0.001, p < 0.001). Conclusions: Use of OK and RGP lenses affects ocular surface status. Especially, meibomian gland parameters and OSDI showed greater changes in RGP lens wearers than OK lens wearers. J Korean Ophthalmol Soc 2016;57(4):546-554

Characteristics of Keratoconic Patients Attending a Specialist Contact Lens Clinic in Kenya.

PURPOSE:To describe the characteristics of keratoconus (KC) patients seen in a contact lens clinic of a children's hospital in Kenya.RESULTS:A total of 254 patients’ records were analyzed. Mean age at presentation to the clinic was 20.97 ± 11.13 year (range, 6–84 years) with 75% between the ages of 6 and 25 years. There was a preponderance of males (59.8%). Most patients were referred by an ophthalmologist. All patients were Africans. The most common complaints were blurred vision (50%), poor visual acuity with spectacles (33.5%), contact lens intolerance (11.8%), and other (unspecified). Most cases were severe (71%) followed by moderate (22.9%) and mild (6.2%). Mean BCVA was 0.24 ± 0.23 (6/11). An optical correction was provided in 98% of cases; 34.6% with spectacles, 31.1% with gas permeable lenses and the remaining with both. Referral for keratoplasty was warranted in 16.5%.CONCLUSION:This is the first study of KC conducted in Kenya. KC presented at a very early age and tended to be severe. Ophthalmologists were the main source of referral. The main presenting symptom was reduced vision. Optical correction was the most common management and the percentage of patients referred for surgery concurred with other studies.

Does the presence of QAC genes in staphylococci affect the efficacy of disinfecting solutions used by orthokeratology lens wearers?

Background/aimThere has been increasing evidence of the emergence of antiseptic resistance mediated by quaternary ammonium compound (QAC) resistance genes, which may reduce the efficacy of disinfection. Although the presence of...

Penggunaan Lensa Kontak untuk Astigmatisma Paska Keratoplasti

Background: Fitting Contact Lenses for post penetrating keratoplasty patiens can be a great challenges to contact lens practitioner. Despite advances in surgical techniques for penetrating keratoplasty, post- operative ametropia and high irregular astigmatism still remain common. Patients who have such those problems may need contact lenses to achieve optimal vision.Case Illustration: Case 1. A 12 years old boy have a high myop and astigmatism after undergone penetrating keratoplasty combined with traumatic cataract extraction and IOL implantation. His right eye vision was 6/24 with corrections of S – 8.00 C – 6.50 x 150. His right eye was fitted with RGP contact lens with Base curve of 7.20 mm, Power of – 10.25 D, and diameter of 8.80 mm. His RE vision with RGP contact lens was 6/12; Case 2. Female, 18 years old, was diagnosed with compound high myopia astigmatism of right eye due to disfigured cornea post keratoplasty and high astigmatism of the left eye due to corneal scar. Piggyback contact lens system is then used to treat her right eye.The patient’s uncorrected visual acuity on the right eye was half meter counting finger, became 6/40 with spectacle and 2 meters counting finger became 3/60 with spectacle on the left eye. With piggyback contact lens consisting of soft contact lens 8.60/-10.00/14.20 and RGP lens 7.20/-4.00/8.8 on the right eye, and RGP lens 7.90/-5.00/9.2 on left eye, her visual acuity became 6/12 on her right eye became 6/9 on the left eye.Conclusion: Rigid gas-permeable and combination of rigid gas permeable and soft contact lenses can be fitted with piggy-back system successfully in patients unable to achieve optimal vision with spectacle correction after penetrating keratoplasty

Contact lens impact on quality of life in keratoconus patients: rigid gas permeable versus soft silicone-hydrogel keratoconus lenses.

To determine the impact of rigid gas permeable (RGP) and silicone-hydrogel keratoconus lenses on the quality of life (QoL) in keratoconus (KCN) patients using the self-reported results from the Contact Lens Impact on Quality of Life (CLIQ) Questionnaire. From January 2013 to April 2013, 27 consecutive KCN patients who wore RGP contact lenses (conflexair100 UV KE Zeiss-Wöhlk) or soft silicone-hydrogel contact lenses (SHCLs) for KCN (KeraSoft IC- Bausch&Lomb or Hydrocone Toris K-Swiss lens) completed the CLIQ questionnaire. The mean age of 27 patients was 29.6±8.0y. Fifteen patients were RGP user. The groups were comparable with respect to the mean patient age, sex, and mean K values (P=0.1, P=0.8 and P=0.1, respectively). The mean CLIQperson measure was 42.8±5.5 in RGP group and 39.6±5.5 in SHCLs for KCN group (P=0.06). CLIQperson measure was positively correlated with steep K value (r=0.301, P=0.04). When eyes were stratified by visual acuity with contact lenses, the mean CLIQperson measure was 42.01±5.6 in eyes with a visual acuity of 20/20-20/25 (n=44) and 38.4±5.26 in eyes with a visual acuity of 20/32 or less (n=10; P=0.097). RGP lenses and SHCLs for KCN have similar impact on QoL.

Effectiveness and safety of overnight orthokeratology with Boston XO2 high-permeability lens material: A 24 week follow-up study.

To examine the effectiveness of overnight orthokeratology lenses made with Boston XO2, highly gas-permeable lens material for the temporary correction of myopia. Myopic individuals from 9 to 62 years of age were eligible. Participants ≤ 12 years of age were required to have myopia ≤-4.00 D and astigmatism ≤ 1.50 D, and for those 13-62 years of age myopia ≤-5.00 D and astigmatism ≤ 3.00 D. All participants were required to have normal healthy eyes and not be receiving any ocular medications or systemic medications likely to affect the results of visual acuity. Participants wore the lenses for a minimum of 7h during sleep, and were evaluated on day 1 and weeks 1, 2, 4, 12, and 24. Success was defined as LogMAR ≤ 0.1. A total of 126 participants (63.5% females) with a mean age of 20.4 ± 11.5 years were recruited. Baseline LogMAR, and vertical and horizontal corneal curvature were 0.8, 7.7 mm, and 7.9 mm, respectively, in both eyes. A consistent decrease in LogMAR was noted from day 1 to week 12. The success rate increased with length of time (from 33.9% to 100% for the right eye and from 35.5% to 100% for the left eye from day 1 to week 24). No severe complications were noted. Overnight orthokeratology with lenses made of Boston XO2 material are effective and safe for the temporary reduction of myopia.

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.

Therapeutic treatment of keratoconus: a survey of local optometric practice criteria

BackgroundDefining the threshold for therapeutic and surgical intervention in patients with keratoconus presents a considerable challenge given the lack of clear, evidence‐based data. Little is known about the patterns of practice and referral criteria of optometrists within Australia.MethodsAll members of the NSW branch of Optometrist Association Australia were invited to complete an online survey in January 2013. This survey was designed to elicit practice information regarding the evaluation and therapeutic treatment of patients with keratoconus in the optometric setting.ResultsResponses were received from 71 optometrists, of whom 65.2 per cent had 15 years or greater experience as an optometrist. Many (35.4 per cent) responded that they prescribed soft contact lenses daily. This percentage dropped to 9.2 per cent for rigid gas‐permeable lenses (RGP), although 47.7 per cent said they would prescribe RGP lenses at least once per month. The main barriers to prescribing were experience with fitting RGP lenses, time and low market demand. In terms of patient referral to an ophthalmologist, the results were variable, with 34.4 per cent stating that they would refer on progression of corneal signs, 23.4 per cent suggesting no set time and 7.8 per cent would refer on initial diagnosis. Many optometrists (62.9 per cent) would refer a patient for possible surgery, when visual acuity dropped to between 6/9 and 6/12. The size or location of the practice was not associated with the number of newly diagnosed cases of keratoconus. Optometrists with greater experience were more likely to prescribe RGP lenses and co‐manage patients with ophthalmologists. Ownership of a corneal topographic unit suggested an increased likelihood of prescribing RGP lenses but did not appear to alter referral patterns.ConclusionOptometrists have an integral role in the diagnosis and management of patients with keratoconus. Our survey provides a basic snapshot of current, local practice. Additionally, ophthalmology should continue to work with optometry to develop guidelines for referral and co‐management to optimise future outcomes for our patients.

각막형상 및 각막난시도가 RGP렌즈와 각막사이의 눈물양에 미치는 영향

목적: 구면 및 비구면 RGP렌즈의 양호한 피팅상태에서 각막형상과 각막난시도에 따른 각막과 렌즈 사이의 부분별 눈물의 차이를 알아보고자 하였다. 방법: 20~30대 77명(135안)을 대상으로 양호한 상태로 피팅된 구면 및 비구면 RGP렌즈를 중심부, 중간주변부, 주변부로 나눠 플루레신으로 염색된 눈물의 농도를 분석하여 눈물양을 정량화하였다. 결과: 모든 각막형상에서 구면 RGP렌즈는 부분별 눈물양의 차이가 존재하였다. 비구면 RGP렌즈 피팅 시 대칭나비형과 비대칭나비형 각막에서는 부분별 눈물양의 차이가 있었으나, 원형과 타원형 각막은 중심부에서 주변부까지 눈물이 고르게 분포하였다. 1.25 D 이하의 각막난시군에 구면 RGP렌즈를 피팅하였을 때는 중심부와 주변부, 중간주변부와 주변부간의 눈물양 차이가 존재하였으나 1.50 D 이상의 각막난시군에서는 부분별 눈물양의 차이가 나타나지 않았다. 또한, 각막난시가 증가할수록 구면 및 비구면 RGP렌즈 모두 중심부 및 중간주변부의 눈물양이 비례하여 증가하였으며, 비구면 RGP렌즈의 경우가 증가폭이 더 컸다. 결론: 본 연구 결과, 구면 RGP렌즈에 비해 비구면 RGP렌즈와 각막 사이의 눈물양 차이가 적었으며, 각막형상과 난시도에 따라 각막과 렌즈사이의 눈물양에 차이가 있음을 밝혔다. 또한, 본 연구를 통해 정립된 RGP렌즈와 각막사이의 상대눈물양을 측정하는 방법이 콘택트렌즈와 각막 사이의 눈물양 평가에 사용될 수 있을 것으로 보인다. Purpose: In the present study, a difference in tear volume between the cornea and the rigid gas permeable (RGP) lens relative to corneal shape and corneal astigmatism was investigated by the alignment fitting status of spherical and aspherical RGP lenses. Methods: Spherical and aspherical RGP lenses were fitted with alignment in 77 subjects (135 eyes) who were in their 20~30s. Tear volume stained with fluorescein was qualitatively analyzed by dividing cornea into center, mid-peripheral and peripheral parts. Results: For the spherical RGP lens fitting, tear volume differences were found in each part in all corneal types. For the aspherical RGP lens fitting, tear volume differences were in each corneal part in symmetric bow tie- and asymmetric bow tie-type corneas. However, the tear was equally distributed from the center to the peripheral part in round- and oval-type corneas. In the group with corneal astigmatism lower than 1.25 D, tear volume between center and peripheral parts, and mid-peripheral and peripheral parts, was different when a spherical RGP lens was fitted. However, tear volume in each part was not different in the group with corneal astigmatism over 1.50 D. Moreover, the tear volumes of the central and mid-peripheral parts were proportionally increased with increasing corneal astigmatism in both spherical and aspherical RGP lenses. Furthermore, aspherical RGP lenses showed greater increments than spherical RGP lenses. Conclusions: The results revealed that the difference in tear volume between aspherical RGP lens and cornea was less than spherical RGP lens, and the difference in tear volume varied according to corneal shape and astigmatism. In addition, the method of measuring relative tear volume between RGP lens and cornea that was established in the present study can be used to evaluate tear volume between contact lens and cornea.

UV-B 반복노출에 따른 항산화효소의 변성 및 활성저하와 RGP렌즈의 차단효과

목적: 본 연구는 안구에 존재하는 항산화효소인 superoxide dismutase(SOD)와 catalase(CAT)가 UV-B에 반복적으로 노출되었을 때 유발되는 구조변성 및 활성저하의 상관관계를 밝히며, 자외선 차단 RGP렌즈의 사용으로 효소의 변성과 활성저하가 효율적으로 차단되는가를 알아보기 위하여 수행되었다. 방법: SOD와 CAT의 표준품으로 각각의 효소용액을 제조하고 하루 30분, 1시간 및 2시간씩 312 nm의 UV-B에 1, 2, 3, 4 및 5일 동안 반복적으로 노출시켰다. 이 때 UV-B에 직접 노출시킨 항산화효소의 구조 및 활성변화를 자외선 차단기능이 있는 RGP렌즈로 UV-B를 차단시킨 경우와 비교하였다. UV-B 반복노출에 따른 SOD와 CAT의 구조변성은 전기영동분석으로 확인하였으며, 이들 효소활성은 분석키트를 이용하여 비색분석법으로 측정하였다. 결과: UV-B에 반복노출된 SOD는 일일 30분 조사조건으로 반복노출되었을 때에도 전기영동분석에서 효소다중화(polymerization)가 관찰되었으나 활성의 변화는 10% 이내로 나타났다. 반면 UV-B에 반복노출된 CAT은 전기영동 시 효소밴드크기나 진하기가 감소하여 구조변성이 나타났음을 확인할 수 있었으며, 반복노출시간이 긴 경우 CAT은 전기영동분석에서 효소밴드를 보임에도 불구하고 그 활성은 완전히 소실되었다. 또한 UV-B 조사로 인한 CAT의 변성은 63.7%의 UV-B 차단기능을 가진 RGP렌즈의 사용으로 어느 정도 억제되었으나 완전히 억제되는 것은 아니었다. 결론: 이상의 결과로 UV-B 반복노출에 따른 항산화효소의 구조변성은 그 종류에 따라 효소활성의 감소정도와 반드시 일치하는 것은 아님을 알 수 있었다. 따라서 자외선으로 인한 항산화효소의 손상을 막기 위하여서는 콘택트렌즈를 착용한 상태에서 자외선 노출시간을 최소화하거나, FDA Class I 차단제에 해당하는 UV 차단율을 가지는 콘택트렌즈를 착용 또는 이에 상응하는 UV차단율을 가지는 선글라스를 덧착용할 것을 권장한다. Purpose: The present study was conducted to reveal the correlation of structural denaturation and decrease of enzyme activity when the antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT) were repeatedly exposed to UV-B, and further investigate whether the denaturation and inactivation of those enzymes can be effectively blocked by using UV-inhibitory RGP lens. Methods: Each enzyme solution was prepared from the standardized SOD and CAT, and repeatedly exposed to UV-B of 312 nm for 30 minutes, 1 hour and 2 hours a day over 1, 2, 3, 4 and 5 days. Structural denaturation of SOD and CAT induced by repeat UV-B irradiation was confirmed by the electrophoretic analysis, and their enzyme activity was determined by the colorimetric assay using the proper assay kit. At that time, the change in structure and activity of the antioxidant enzymes directly exposed to UV-B was compared to the case that UV-B was blocked by UV-inhibitory RGP lens. Results: SOD exposed repeatedly to UV-B showed the polymerization pattern in the electrophoretic analysis when it repeatedly exposed for 30 min a day, however, the change of its activity was less than 10%. On the other hand, CAT repeatedly exposed to UV-B reduced size and density of the electrophoretic band which indicated a structure denaturation, and its activity was significantly decreased. In the case that the repeat exposure time was longer, CAT activity was completely lost even though some enzyme band occurred in the electrphoretic analysis. In addition, the degeneration of CAT due to UV-B irradiation was inhibited to some extent by using RGP lens with a UV-B blocking of 63.7%, however, it was not completely inhibited. Conclusions: From these results, it was revealed that the structural denaturation of antioxidative enzymes was not perfectly correlated with the reduction in enzyme activity according to the type of enzyme. It is recommended to minimize the exposure time to UV when wearing contact lens, or wear the contact lenses having UV blocking rate of the FDA Class I blocker or the sunglasses having equivalent UV-blocking rate for reducing the damage of antioxidative enzymes induced by UV.

A program to analyse optical coherence tomography images of the ciliary muscle.

To describe and validate bespoke software designed to extract morphometric data from ciliary muscle Visante Anterior Segment Optical Coherence Tomography (AS-OCT) images. Initially, to ensure the software was capable of appropriately applying tiered refractive index corrections and accurately measuring orthogonal and oblique parameters, 5 sets of custom-made rigid gas-permeable lenses aligned to simulate the sclera and ciliary muscle were imaged by the Visante AS-OCT and were analysed by the software. Human temporal ciliary muscle data from 50 participants extracted via the internal Visante AS-OCT caliper method and the software were compared. The repeatability of the software was also investigated by imaging the temporal ciliary muscle of 10 participants on 2 occasions. The mean difference between the software and the absolute thickness measurements of the rigid gas-permeable lenses were not statistically significantly different from 0 (t=-1.458, p=0.151). Good correspondence was observed between human ciliary muscle measurements obtained by the software and the internal Visante AS-OCT calipers (maximum thickness t=-0.864, p=0.392, total length t=0.860, p=0.394). The software extracted highly repeatable ciliary muscle measurements (variability ≤6% of mean value). The bespoke software is capable of extracting accurate and repeatable ciliary muscle measurements and is suitable for analysing large data sets.

Efficacy of a Gas Permeable Contact Lens to Induce Peripheral Myopic Defocus

The purpose of this work was to evaluate the potential of a novel custom-designed rigid gas permeable (RGP) contact lens to modify the relative peripheral refractive error in a sample of myopic patients. Fifty-two right eyes of 52 myopic patients (mean [±SD] age, 21 [±2] years) with spherical refractive errors ranging from -0.75 to -8.00 diopters (D) and refractive astigmatism of 1.00 D or less were fitted with a novel experimental RGP (ExpRGP) lens designed to create myopic defocus in the peripheral retina. A standard RGP (StdRGP) lens was used as a control in the same eye. The relative peripheral refractive error was measured without the lens and with each of two lenses (StdRGP and ExpRGP) using an open-field autorefractometer from 30 degrees nasal to 30 degrees temporal, in 5-degree steps. The effectiveness of the lens design was evaluated as the amount of relative peripheral refractive error difference induced by the ExpRGP compared with no lens and with StdRGP conditions at 30 degrees in the nasal and temporal (averaged) peripheral visual fields. Experimental RGP lens induced a significant change in relative peripheral refractive error compared with the no-lens condition (baseline), beyond the 10 degrees of eccentricity to the nasal and temporal side of the visual field (p < 0.05). The maximum effect was achieved at 30 degrees. Wearing the ExpRGP lens, 60% of the eyes had peripheral myopia exceeding -1.00 D, whereas none of the eyes presented with this feature at baseline. There was no significant correlation (r = 0.04; p = 0.756) between the degree of myopia induced at 30 degrees of eccentricity of the visual field with the ExpRGP lens and the baseline refractive error. Custom-designed RGP contact lenses can generate a significant degree of relative peripheral myopia in myopic patients regardless of their baseline spherical equivalent refractive error.

Rigid gas‐permeable contact lens related life quality in keratoconic patients with different grades of severity

PurposeThe aim was to compare the impact of rigid gas‐permeable (RGP) contact lenses on vision‐related quality of life (VR-QOL) in keratoconic patients with different grades of severity.MethodsThis comparative study was conducted from December 2012 to September 2013 on 46 patients with bilateral keratoconus. Patients were divided into three groups according to the average of the steep keratometry (K) readings in the two eyes of each patient. Main outcome measures included binocular visual acuity (VA), lens wearing time, the 25‐item National Eye Institute Visual Function Questionnaire (NEI-VFQ‐25), foreign body (FB) sensation, comfort and overall satisfaction.ResultsPatients with severe keratoconus showed significantly reduced wearing time compared with the other two groups (4.8 ± 2.5 hours per day). Regarding the subjective criteria, there was no significant difference on NEI-VFQ‐25 scores, foreign body sensation, comfort and overall satisfaction between mild and moderate keratoconus groups but scores in the group with severe keratoconus were significantly lower than the other two groups. Binocular VA strongly correlated with NEI-VFQ‐25 scores; however, NEI-VFQ‐25 scores had no significant correlations with different disease severities.ConclusionsAppropriate correction with RGP lenses contributes to good VR-QOL for keratoconic patients; however, as the disease progresses to a steep keratometric value of more than 52 dioptres (6.50 mm), RGP lenses did not guarantee a relatively good VR-QOL. Other lens options with new designs might bring better life quality for these patients with severe keratoconus.

Postkeratoplasty Astigmatism

The success of penetrating keratoplasty in terms of graft survival is excellent but visual rehabilitation continues to be a significant issue primarily due to astigmatism. Factors contributing to postoperative astigmatism can be related to preoperative etiology, suturing techniques and the postoperative healing process and timing of surgery. The large number of options available to address postoperative astigmatism only serves to highlight the complex nature of the problem. This review offers an up-to-date account of the various options available to manage postkeratoplasty astigmatism. Spectacles and rigid gas-permeable (RGP) contact lenses offer the earliest and easiest forms of visual rehabilitation. Spectacle correction may be limited by astigmatic anisometropia. Rigid gas-permeable contact lenses are an effective alternative to spectacles but limited by fitting and handling issues. Suture adjustment and suture removal are the initial options for reducing postoperative astigmatism. Careful attention to suture techniques intraoperatively and timely removal of appropriate sutures in the postoperative period can decrease astigmatism to tolerable levels. For the management of residual astigmatism after suture removal, a plethora of choices exist. Relaxing incisions, astigmatic keratotomy, compression sutures and wedge resections are well explored techniques offering effective but unpredictable results. Photorefractive keratectomy and laser in situ keratomileusis are newer options available to correct both spherical and astigmatic errors, but outcomes are variably affected by the healing process. The current availability of phakic and toric intraocular lenses has also been explored for the correction of postkeratoplasty astigmatism with promising results. Intra-corneal ring segments used for the management of astigmatism in keratoconus finds a new application in postkeratoplasty astigmatism. The femtosecond laser has opened up ways to perform procedures such as astigmatic keratotomy, the placement of intra-corneal ring segments, and creation of flaps for laser in situ keratomileusis, with very good precision and accuracy.

Corneal cell morphology of keratoconus patients in Malaysia—A confocal microscopy observation

Purpose: To compare visual functions (visual acuity (VA) and contrast sensitivity (CS)) and aberration patterns of keratoconus (KC) patients using spectacles and specific design contact lenses (rigid gas permeable and silicone hydrogel). The outcomes will improve the Optometric management of the disease. Method: This is a pilot study involving 13 eyes from 9 newly diagnosed keratoconus subjects. Subjects were fittedwith RGP and SH contact lenses. The VA and CS were measured using Snellen and Pelli-Robson charts respectively. Ocular aberrationsweremeasured using OPD scan II. All measurements were conducted before (during spectacles wear) and after contact lens wear. Results: Significantly better VA was obtained with RGP than spectacle or SH (P<0.001). Insignificant difference was detected in CS values between RGP and SH (P=0.06). Both SH and RGP significantly reduced total ocular and higher-order aberrations (HOAs) (P<0.001) than spectacles but RGP reduced trefoil, coma and spherical aberrations more than SH. Insignificant difference was also detected in astigmatic aberrations between RGP and SH (P=0.12). Negative correlation was noted between VA and coma aberration (P=0.04) and CS showed strong negative correlations with HOAs, coma, trefoil and astigmatic aberrations. Conclusions: The RGP lenses provided better VA and greater reduction of aberrations than spectacles or SH lenses in keratoconic eyes. However, more data is needed to confirm these findings. Dr. Bariah Mohd-Ali is a Professor and Optometrist at the Optometry and Vision Science Program, University Kebangsaan Malaysia. She is involved in teaching contact lens courses for undergraduate and postgraduate students and is fundamental in the development of specialty contact lens clinic within the university.

Visual performance and aberration in keratoconus: A comparison between rigid gas-permeable and soft contact lenses—A pilot study

Purpose: To compare visual functions (visual acuity (VA) and contrast sensitivity (CS)) and aberration patterns of keratoconus (KC) patients using spectacles and specific design contact lenses (rigid gas permeable and silicone hydrogel). The outcomes will improve the Optometric management of the disease. Method: This is a pilot study involving 13 eyes from 9 newly diagnosed keratoconus subjects. Subjects were fittedwith RGP and SH contact lenses. The VA and CS were measured using Snellen and Pelli-Robson charts respectively. Ocular aberrationsweremeasured using OPD scan II. All measurements were conducted before (during spectacles wear) and after contact lens wear. Results: Significantly better VA was obtained with RGP than spectacle or SH (P<0.001). Insignificant difference was detected in CS values between RGP and SH (P=0.06). Both SH and RGP significantly reduced total ocular and higher-order aberrations (HOAs) (P<0.001) than spectacles but RGP reduced trefoil, coma and spherical aberrations more than SH. Insignificant difference was also detected in astigmatic aberrations between RGP and SH (P=0.12). Negative correlation was noted between VA and coma aberration (P=0.04) and CS showed strong negative correlations with HOAs, coma, trefoil and astigmatic aberrations. Conclusions: The RGP lenses provided better VA and greater reduction of aberrations than spectacles or SH lenses in keratoconic eyes. However, more data is needed to confirm these findings. Dr. Bariah Mohd-Ali is a Professor and Optometrist at the Optometry and Vision Science Program, University Kebangsaan Malaysia. She is involved in teaching contact lens courses for undergraduate and postgraduate students and is fundamental in the development of specialty contact lens clinic within the university.