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PubMed2004

Short-term physiologic response in neophyte subjects fitted with hydrogel and silicone hydrogel contact lenses.

PURPOSE: To investigate the short-term physiologic response to three soft lens materials with different oxygen permeability characteristics. METHODS: Forty-three neophytes were randomly prescribed Acuvue 2, Acuvue Advance (Johnson & Johnson Vision Care), or Focus Night & Day (CIBA Vision) for 4 weeks on a daily-wear basis. A further 19 subjects did not wear lenses (control). Experimental and control subjects were examined 2 and 4 weeks after dispensing. Ocular physiologic response was measured with a slitlamp biomicroscope in a strictly masked fashion. RESULTS: Limbal redness increased in the Acuvue 2 group compared with the other two groups. Conjunctival redness increased more in the Acuvue 2 group than in the Acuvue Advance group. More conjunctival staining was seen with the Acuvue Advance and Focus Night & Day groups compared with the Acuvue 2 group. Increased scores for papillary conjunctivitis were seen in the Focus Night & Day group compared with the Acuvue Advance group. CONCLUSIONS: The reduced level of limbal redness seen with the Acuvue Advance and Focus Night & Day groups suggests that these lenses provide more oxygen to the ocular surface than the Acuvue 2 lens to a degree that can be observed clinically. The conjunctival staining response was similar for the Acuvue Advance and Focus Night & Day groups. The results for the Acuvue Advance and Focus Night & Day groups for papillary conjunctivitis may reflect differences in their material and surface properties.

Adult↗
PubMed2000

Clinical performance and periodontal outcome of temporary crowns and fixed partial dentures: A randomized clinical trial.

STATEMENT OF PROBLEM: Different materials (autopolymerizing, dual curing, and light initiated) are used for fabricating provisional restorations during prosthetic treatment. Randomized clinical trials that have evaluated these provisional materials have not been published. PURPOSE: This clinical trial compared the handling, fitting, plaque adherence, gingivitis, color stability, and the subjective assessment of the provisional materials by the patient and the dentist for 2 autopolymerizing (Protemp, Luxatemp), 1 dual-curing (Provipont), and 1 light-initiated (Triad-VLC) material for the manufacturing of temporary crowns and fixed partial dentures. MATERIAL AND METHODS: Thirty subjects in need of 2 similar fixed prosthetic restorations (single crowns ¿20, three-quarter crowns ¿2, connected crowns ¿9, or fixed partial dentures ¿30) were treated with 1 temporary restoration of Protemp II (control) and one randomly selected from Luxatemp, Provipont, or Triad-VLC materials. The mean time of treatment was 37.5 days (minimum 2 days, maximum 156 days). All restorations were manufactured intraorally with a vacuum-formed template. RESULTS: Mechanical and retentive characteristics revealed a high level of clinical reliability. Plaque adherence of the teeth with temporary restorations was significantly increased (P =.0039) compared with the untreated mesial reference teeth. CONCLUSION: The advantageous mechanical properties of the light-curing and dual-curing materials reviewed in dental literature were clinically offset by disadvantages in handling.

Chi-Square Distribution↗
PubMed2001

A comparison of the cost effectiveness of pressure-indicating materials and their ability to detect pressure areas in complete dentures.

Pressure areas on the fitting surfaces of dentures can cause great discomfort and pain to denture wearers if not detected and removed. Pressure-indicating materials are commonly used to detect these areas, and several commercial varieties are available, but these tend to be expensive. The cost effectiveness of these materials has not been investigated, nor has this been linked to their efficacy and ease of use. The aim of this study therefore, was to compare the different pressure-indicating materials available commercially with that of a home-made paste. An assumption of efficacy was made by the number and size of pressure areas revealed, by taking standardised photographs and analysing the images. User friendliness was determined by the time taken to mix, apply and remove the material. Cost was determined by a cost per unit calculation based on the average or minimum quantity required for each material. The results indicated that a home-made paste made of equal quantities of hand lanolin (BP) and zinc oxide powder was not only the most effective, but was also the cheapest, being only 3% of the cost of the most expensive of the materials.

Alginates↗
PubMed2004

Improved tibial cutting accuracy in knee arthroplasty.

Initial stability and development of long-term fixation for cementless tibial components at the knee both depend on the accuracy of fit between implanted components and prepared bone surfaces. Tibial surfaces prepared for total knee replacement with conventional saw-blades and guides were shown by Toksvig-Larsen to vary by over 2 mm, from a flat surface at the point of maximum variation, and all points varied with a standard deviation of up to 0.4 mm. Surface cutting errors are caused by flexion of the saw-blade and blade angulation from the ideal alignment, due to poor guidance or control by the saw-block or guide. Most conventional knee instrumentation relies on flat surface or slotted cutting blocks, constraining the moving saw-blade against one or two guide surfaces. Improved cutting action was achieved by constraining the saw from the pivot point of the blade, and controlling motion of this constraint with parallel action slides. Using this saw-guide and an improved saw-blade, tibial cuts were made in mock arthroplasty procedures on twenty four cadaveric tibiae in mortuo. Analysis of Variance and Tukey's HSD test showed that the improved saw technique yielded significantly better flatness (p < 0.03) and greatly improved roughness (p < 0.0005).

Adult↗
PubMed2006

Combining perimodiolar electrode placement and atraumatic insertion properties in cochlear implantation -- fact or fantasy?

CONCLUSIONS: Except for basal cochlear traumatization, all specimens implanted into scala tympani showed atraumatic insertion properties and good perimodiolar electrode positioning. Cochleostomy preparation and placement can have a significant impact on levels of basal cochlear trauma. OBJECTIVE: In the past, perimodiolar cochlear implant electrodes increased the risk for intracochlear traumatization when compared to free-fitting arrays. Recently, however, clinical evidence for atraumatic perimodiolar implantations with preservation of residual hearing has been described. The aim of this paper was to histologically evaluate a perimodiolar cochlear implant array for its insertion properties in cadaver human temporal bones. Surgical and electrode factors, as well as preparation artifacts influencing intracochlear trauma, were considered in the evaluation. MATERIALS AND METHODS: Sixteen human temporal bones were harvested up to 24 hours post mortem and implanted immediately with the Nucleus 24 Contour Advance cochlear implant electrode array. Implantations were either performed using a regular caudal approach cochleostomy or through the round window membrane. After implantation, all bones underwent special histological processing, which allowed sectioning of undecalcified bone. Insertion properties were evaluated according to a grading system. RESULTS: Fourteen specimens were implanted into scala tympani and only two exhibited basal trauma attributable to electrode insertion characteristics. Two bones were implanted into scala vestibuli after causing trauma in the region of the cochleostomy. Insertion depths ranged from 180 degrees to 400 degrees. All bones showed good perimodiolar electrode positioning. Basal trauma due to surgical issues and histological artifacts was present in 10 of 16 bones.

Auditory Threshold↗
PubMed2000

Mandibular matrix implant system: a method to restore skeletal support to the lower face.

Disharmony between the skeletal support and the softtissue envelope is a common cause of aesthetic concerns regarding the lower face. A loss of volume or a genetically small mandible affects the aesthetics and function of the mouth, chin, and neck. Because of the limitations of correcting such problems with current implants made of silicone or porous polyethylene, the author developed an implant system and a method of restoring the entire volume of the mandible called the mandibular matrix implant system. This implant system is made of high-density porous polyethylene and is composed of an articulated wraparound geniomandibular implant and a wraparound gonial angle implant. A prejowl implant can be integrated in the system as an addition or as a replacement for a chin implant. This implant system has different sizes and projections, and it can be modified by carving to fit the requirements of most patients. Carving is done using an appropriate sizer. This implant system is indicated for use in patients with a congenitally small mandible, edentulous patients, and patients requesting facial enhancement. The mandibular matrix implant system is implanted either during a single procedure or simultaneously with a facial rejuvenation. The extended geniomandibular implant is introduced through an anterior oral sulcus incision or a submental incision. The mandibular angle implant is introduced through a retromolar incision. The posterior end of the chin implant overlaps the anterior end of the gonial implant, and screw fixation of each chin component helps to stabilize the entire system. Antibiotics, irrigation, and closure of the incisions are performed before any additional operative procedure. The complete system has been used in 13 patients; one additional patient had the complete system plus an overlapping additional left prejowl implant for correction of asymmetry. Complications were manageable; these included one mandibular angle implant displacement and one infection. The implant displacement required a reoperation to reset the implant. The infection was treated with irrigation and closed system suction; the implant was salvaged. The satisfaction of patients has been high, and the author can now solve aesthetic problems that in the past were considered unsolvable.

Chin↗
PubMed2006

Use of intralimbal rigid gas-permeable lenses for pellucid marginal degeneration, keratoconus, and after penetrating keratoplasty.

PURPOSE: To discuss the results of fitting Dyna Intra-Limbal lenses (Lens Dynamics, Inc., Golden, CO) (DIL) for pellucid marginal degeneration (PMD), keratoconus, and after penetrating keratoplasty (PK). METHODS: The charts of patients fitted with DILs between January 2003 and December 2004 were retrospectively reviewed. Ocular diagnosis, indication for DIL, flat and steep curvatures by corneal topography, and age at the time of initial fitting were noted. The DIL data included initial base curve, power, and the number of changes made in parameters during the follow-up. The outcome data included visual acuity and the duration of follow-up and lens wear. Complications and complaints were also noted. RESULTS: Twenty-seven eyes of 22 patients were reviewed. Fourteen eyes had PMD; seven had keratoconus; and six eyes had undergone PK. The mean age of patients was 52.7 +/- 13.1 years. The mean follow-up was 8.9 +/- 7.4 months. Nine (33.3%) eyes achieved 20/20 visual acuity; 13 (48.1%) eyes achieved 20/25 to 20/40; and five (18.5%) eyes achieved 20/50 to 20/70. Fifteen (55.6%) eyes achieved visual improvement (two lines or more). The mean number of refits was 1.1 +/- 0.9. No infection or neovascularization was noted; a corneal abrasion occurred in one eye. Good wearing time was achieved in 18 (66.7%) eyes of 13 patients, who were still wearing DILs at the last follow-up. CONCLUSIONS: DILs may be a good alternative in selected patients with flat central and superior corneas and inferior peripheral steepening.

Adult↗
PubMed2005

An in-vitro investigation of the accuracy of fit of Procera and Empress crowns.

The current study aimed to investigate the accuracy of fit and the reproducibility of inner crown profile for two types of high strength ceramics, IPS Empress and Procera. Procera and Empress crowns with four different morphologies were cemented to dies using zinc phosphate dental cement. Vertical and horizontal sections were made through each of the crown/die preparations and images of the vertical sections were compared for curvature reproduction by alignment using image processing. Measurements were made on horizontal sections to determine cement layer thickness. Alignment of the crowns using image analysis identified quantifiable variations in the inner surface profile compared with the outer surface of the die. The largest differences occurred from the cusp tips to the occlusal adaptation area and differences in surface profile were less pronounced for Procera than Empress crowns. Marginal gap varied independently of ceramic or internal crown shape from 7-529 microm for Procera and 26-548 microm for Empress. IPS Empress has a superior ability to reproduce the inner surface profile of the crown morphologies investigated compared with Procera. The reduced reproduction of surface profile was associated with an increased cement thickness at the occlusal contact area that may inadvertently lead to failure of the crowns functional characteristics.

Crowns↗
PubMed2004

Influence of stimulus frequency on NRT recordings.

Research in neural response telemetry (NRT) with the Cochlear 'Nucleus' CI24M Implant began a few years ago, using the first NRT software version (2.04). It has been demonstrated that NRT offers possibilities for fitting the implant speech processor. NRT sessions, however, remain lengthy for the patients, especially for children, and NRT research is seeking to reduce session time. The new version of the NRT software (3.0) allows implant stimulation up to 400 Hz, whereas the previous version stimulated only up to 80 Hz. The time gained is very significant. The goal of the present study was to observe and assess the modifications in NRT produced by these higher stimulus frequencies. Growth functions were measured in six adult patients for electrodes 5-10-15-20 at frequencies of 20, 80, 150, 250 and 365 Hz to determine NRT thresholds (NRT-T). Subjective detection thresholds (T) were also measured for the same electrodes and frequencies. The results showed that the number of valid responses, like the quality and amplitude of the NRT response, quickly decreased at these higher rates. Consequently, the number of measurement points used for the growth function decreased with frequency. Moreover, when frequency increased, the T value decreased while NRT-T increased: the gap between the two thresholds increased with frequency in a linear manner common to all patients. The growth function slopes did not change significantly with frequency.

Auditory Perception↗
PubMed1999

Relaxed versus activated stump muscles during casting for trans-tibial prostheses.

In prosthetic practice, the question often arises as to whether the hand cast should be made from a contracted or from a non-contracted amputation stump. To elucidate this question, the authors have performed a study to quantify the volume difference between these 2 conditions, and to relate the differences to prosthetic fitting. Sixteen (16) trans-tibial amputees participated in the study. All of them were fitted with an ICEROSS silicone socket. Electromyographic studies, with electrodes attached to the anterior tibial and medial gastrocnemius muscles, were carried out to determine muscle contraction levels. Volume determinations were made with the CAPOD laser scanning system. Measurements were performed with and without the silicone liner on the stump. Without a silicone liner, the volume of the stump increased by 5.8% (SD=5.3) as the muscles contracted. This increase was statistically significant. With the liner donned the volume increased 3.5% (SD=3.3). This increase was also statistically significant. The volume of the prosthetic socket was also compared with the stump volume with a silicone liner on. For the relaxed stump, the difference was 1.8% (SD=10.1), and for the contracted stump -1.7% (SD=11.3). Neither difference was statistically significant. The importance of these volume changes and how they influence stiffness of the coupling between the stump and the socket are discussed. It is concluded, that the observed difference in volume between a contracted and a non-contracted stump are large enough to be considered by the prosthetist in his decision on how to make a hand cast.

Aged↗
PubMed2002

Laboratory and clinical tests of a prototype pressure sensor for clincial assessment of prosthetic socket fit.

Lower limb prosthetic socket fabrication is a highly refined process relying on the prosthetist's skill and experience. Despite their best efforts, patients often return with complications. Additionally, clinical application of technological advances for the quantification of biomechanical factors at the socket interface has not changed in practice. Measuring pressure levels at the stump/socket interface could provide valuable information in the process of prosthetic socket fabrication, fit and modification. This paper presents findings on the performance of a prototype capacitance pressure sensor designed for prosthetic socket use. Bench tests using compressed air were performed to measure accuracy, hysteresis and drift responses in both a flatbed chamber and a custom-modified pressure vessel. For the contoured testing, the sensors were placed on nine sites on a positive trans-tibial stump mould and enveloped with a silicone liner. Additionally, a preliminary clinical evaluation was performed with two trans-tibial amputee subjects at the nine sites during normal ambulation. Bench test results showed that the prototype capacitance sensor performed well in all categories, exhibiting a 2.42% (flatbed) and 9.96% (contoured) accuracy error, a 12.93% (flatbed) and 12.95% (contoured) hysteresis error, and a 4.40% (flatbed) and 6.20% (contoured) drift error. The clinical study showed that after three hours of continual use, no noticeable sensor drift occurred between pre and post-test calibration values. The results from this study were encouraging and the authors hope to conduct further laboratory and clinical trials to assess the influence of shear force and dynamic loading on sensor response.

Ambulatory Care Facilities↗
PubMed2004

Impact of manufacturing technology and material composition on the clinical performance of hydrogel lenses.

PURPOSE: To establish the clinical impact of three different methods of manufacture used to produce soft contact lenses. METHODS: Clinical performance of five lens types was investigated by undertaking a prospective, double-masked, randomized, crossover study. Three of the lenses were made from poly(hydroxyethyl methacrylate) (pHEMA) by three different manufacturing processes (lathing, spin casting, and cast molding), and the remaining two lenses were cast molded from different materials-hydroxyethyl methacrylate/methacrylic acid and hydroxyethyl methacrylate/glycerol methacrylate (HEMA/GMA). All lenses were specially fabricated for this work at the same manufacturing plant. Thirty-four soft contact lens wearers wore each lens for 1 month on a daily-wear basis. Several clinical variables, such as ocular response, visual acuity, lens fitting, prelens tear film, lens surface dehydration, subjective response, and protein deposition, were measured. RESULTS: In general, the spun-cast pHEMA lens performed inferiorly compared with the other pHEMA lenses. This lens induced significantly more limbal and conjunctival hyperemia than the cast-molded lens and provided poorer low contrast visual acuity (LCVA) than the other two lenses. It dehydrated more and had the least on-eye movement. However, the spun-cast lens deposited the least protein of the pHEMA lenses. In general, the HEMA/GMA lens performed inferiorly compared with the other cast-molded lenses. LCVA was worse with this lens, and subjective responses showed that this lens was thought to give the worst visual performance of the cast-molded lenses. It was also thought to be the most difficult lens to handle. Significantly more breakages occurred with this lens than any other. CONCLUSIONS: Overall, this work has shown that manufacturing method and material composition have a fundamental effect on many clinical properties of a lens. Therefore, method of manufacture is also an important consideration in the overall production of a soft lens.

Adult↗
PubMed1997

Differences in performance between Oticon MultiFocus Compact and ReSound BT2-E hearing aids.

Differences in performance were evaluated between binaural fittings of the Oticon MultiFocus (MF) and ReSound BT2-E on 25 hearing-impaired subjects across two sites. Subjects were initially fit using each manufacturer's algorithm and adjustments were made at 1 week based on subjects' responses to diary questions. Performance was assessed after a 4- to 6-week trial period with each hearing aid set using the Speech Perception in Noise (SPIN) test administered at 50, 65, and 80 dB SPL, the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire, loudness judgments of female connected discourse at 65 and 80 dB SPL, and an overall preference selection. The MF yielded significantly better SPIN scores at 50 and 65 dB SPL, while the BT2-E yielded a significantly better score at 80 dB SPL. No statistically significant differences were found in the APHAB benefit scores between the hearing aid sets, but both sets were significantly better than the subjects' own hearing aids on three of the four subscales. The MF produced slightly higher mean loudness judgments at both input levels than the BT2-E. Finally, 12 subjects preferred the BT2-E, 10 subjects preferred the MF, and three subjects stated no preference. The results are discussed in terms of audiogram effects on preference and effects of differences in signal processing approaches between the devices.

Audiometry↗
PubMed2002

Practice of orthokeratology by a group of contact lens practitioners in Hong Kong--Part 1. General overview.

PURPOSE: To describe orthokeratology (ortho-k) as practised by a number of practitioners in Hong Kong. METHODS: Twelve optometrists who had been practising ortho-k for between 2.5 and four years were interviewed in the period 1 March to 30 June 2001. RESULTS: The number of ortho-k cases seen by each practitioner ranged from 50 to 800, and the main reason for fitting was myopia control in children. All practitioners were using advanced ortho-k lens designs and most recommended night therapy. In general, patients were accepted if they had less than five dioptres of myopia; one or two lenses were required for a myopia reduction of four dioptres or less, whereas two to four lenses were required to achieve reduction of more than four dioptres. Success, defined as the percentage of the target reduction agreed with patients that was actually achieved, was reported as better than 80 per cent for most practitioners. The time for trial lens wear was from 15 minutes to four hours and was 30 minutes in most cases. Suction holders were generally used for lens removal. Foggy vision was the most frequently reported adverse symptom and mild corneal staining the most frequent sign. CONCLUSIONS: It is clear that there is considerable variation in the practice of ortho-k in Hong Kong even among the relatively experienced practitioners interviewed here. The skills of contact lens practitioners in Hong Kong vary considerably because of the nature of the registration arrangements. We suggest that a statement of best clinical practice for ortho-k should be developed to assist practitioners to carry out this procedure effectively and safely.

Contact Lenses↗
PubMed1994

Soft lens movement: temporal characteristics.

The time-course of on-eye hydrogel lens movement has not been carefully scrutinized, despite the importance of lens movement in optimizing lens fit and corneal physiology. We conducted a study to define the time-course of soft lens movement using 26 subjects. Video slitlamp recordings were made of lens movement at 5-min intervals for 30-min wear and after 8-h wear of 38 or 67% water content lenses (N = 14 and 12, respectively). Lens mobility profiles were statistically indistinguishable for high and low water content lenses, and for experienced and neophyte lens wearers. Lens movement displayed biphasic temporal characteristics, decreasing significantly over the first 25 min from a median of 0.6 to 0.3 mm (Wilcoxon matched-pairs signed-rank test, p = 0.002), then increasing significantly to 0.5 mm after 8 h of wear (p = 0.03). Although some subjects exhibited little alteration in lens movement, 31% showed a decrease in lens movement > 0.25 mm during the first half-hour of wear. Optimal predictability of lens mobility after 8-h wear was achieved 5 min after insertion, with 77% of subjects displaying lens movement within +/- 0.25 mm of the final value. In-office assessment of lens movement is best achieved 5 min after insertion, although clinical and real world lens mobility will differ significantly in about one in four patients.

Blinking↗
PubMed1998

Effect of patient personality profile and verbal presentation on successful rigid contact lens adaptation, satisfaction and compliance.

BACKGROUND: Rigid gas permeable (RGP) lenses have numerous benefits, including quality of vision, ocular health, and reduction of myopic progression in young people. Nevertheless, RGP lens use is not increasing in the United States. It is possible that certain patient personality characteristics and/or how a practitioner presents RGP lenses to a new patient may affect satisfaction and success. The purpose of this study was to evaluate the effect of individual patient's personality and the practitioner's method of presenting RGP lenses to new patients on their ability to adapt to these lenses. METHODS: Forty-nine subjects, all noncontact lens wearers, were entered into this 1-month study, which was conducted at both the University of Missouri-St. Louis School of Optometry and the Pacific University College of Optometry. All subjects initially completed standardized questionnaires pertaining to locus of control, openness to new experiences, and motivation/expectations. After diagnostic fitting with a RGP lens material, the subjects were placed into one of the following three groups: (1) Fear-Arousing Non-Enthused; (2) Neutral Content Non-Enthused; or (3) Neutral Content Enthused. They observed one of three video presentations on RGP lens wear. Subjects submitted daily questionnaires providing their evaluation of such factors as comfort, wearing time, and handling. RESULTS: The results showed that there was a significant difference (chi(2) = 6.99; p < 0.05) among the different groups in the number of dropouts: 6/19 with the Fear-Arousing Non-Enthused group, 2/17 with the Neutral Content Non-Enthused group, and 0/13 with the Neutral Content Enthused group. There was also a significant difference (ANOVA F = 4.1, p < 0.05) among the groups on compliance, with the Neutral Content Enthused group demonstrating greater compliance. In terms of satisfaction, there was no significant difference among presentation groups. CONCLUSION: It was concluded that the method of presentation is important for successful RGP contact lens wear. If presented with genuine interest and a positive and realistic attitude, patients are more likely to succeed in RGP lens wear during the initial critical period.

Adaptation, Physiological↗
PubMed1999

Clinical performance of an innovative back surface multifocal contact lens in correcting presbyopia.

PURPOSE: This prospective study was designed to subjectively and objectively evaluate the performance of an aspheric multifocal back surface rigid gas permeable (RGP) contact lens. The multifocal element of this lens design consisted of an aspheric optical zone that varied according to the patient's ametropia, corneal topography, and required reading addition. METHODS: We fit 28 presbyopic subjects with an aspheric multifocal back surface RGP contact lens (age range: 45 to 68 years). Reading additions ranged from +0.75 D to +2.50 D. Subjects were assessed initially and at 2, 6, and 12 weeks for ocular changes, visual performance, and subjective responses. RESULTS: We required 116 RGP lenses to achieve an acceptable fit and visual acuity in 28 subjects (55 eyes). At the final visit, the distance logMAR acuity with the multifocal contact lens (+0.12 +/- 0.10) was not statistically different (t = -0.623, P = -0.5388) from spectacle acuity at the initial visit (+0.10 +/- 0.12). The near logMAR acuity with the multifocal contact lens at the final visit (0.36 +/- 0.12) was not statistically different from that for near acuity with spectacles at the initial visit (0.33 +/- 0.13). No slit lamp signs worsened during the study. A reduction in myopia of 0.67 D was noted by the final visit. Spectacle blur was noted if the acuity at the initial refraction was compared to the acuity with the same refraction at the final visit (t = -3.287, P = 0.0028) but not when the refractive changes were incorporated (t = 1.058, P = 0.3127). All subjects rated the performance of the lenses very highly: comfort, 86%; distance acuity, 83%; near acuity, 73%; and stability of vision, 74%. Twenty-four subjects (86%) chose the multifocal contact lens as their preference. CONCLUSION: We demonstrated that a multifocal design is able to provide acceptable distance and near correction for presbyopic patients. The aspheric geometry required can be optimized for a given patient by considering his/her degree of ametropia, as well as the corneal topography.

Aged↗
PubMed2002

Management of pellucid marginal corneal degeneration with rigid gas permeable contact lenses.

PURPOSE: To study the clinical performance of rigid gas permeable contact lenses (RGPCL) in patients with pellucid marginal corneal degeneration (PMCD). METHODS: This retrospective study consisted of 15 patients with clinical PMCD, confirmed by videokeratography (TMS-1, Computed Anatomy, Inc., New York, NY). Information collected from the medical records included patient demographic data, uncorrected visual acuity, refraction, best-corrected spectacle visual acuity, and topographic details, including kerotometry. Twenty-seven of 30 eyes were subjected to several contact lens trials using polymethylmethacrylate (PMMA) contact lenses, using a systematic and consistent approach. After successful contact lens trials, data regarding number of trials, trial time, final contact lens choice parameters, and best-corrected contact lens visual acuity were noted for each patient. During follow-up, visual acuity with RGPCLs, lens fit, and average wearing time were noted. RESULTS: Fifteen patients (30 eyes) with typically inferiorly located pellucid marginal corneal degeneration were included in this study. There were 12 men and 3 women, with a mean age of 39.73 years. Twenty-seven eyes of 15 patients were identified as subjects for multiple contact lens trials, and 24 (88.8%) eyes were successfully fitted with RGPCLs. Best-corrected visual acuity of 6/12 or better with spectacles was achieved in 14 (46.66%) eyes. The average astigmatism was -8.56D, and a majority of the patients with PMCD who were in the contact lens trial had an against-the-rule astigmatism (63.3%). The mean trial time for attempted eyes (i.e., patients with PMCD who successfully underwent the contact lens trials) was 77.7 minutes, and the number of trials required to finalize the choice of contact lenses ranged between 2 and 7. The median base curve for RGP lenses was 7.57, and median diameter was 10.00 mm. Best-corrected visual acuity of 6/12 or better with the final contact lens was achieved in 95.4% of the subjects. After an average follow-up of 22.91 months, one patient was lost to follow-up, and 2 eyes required discontinuation of the contact lenses. The average wearing time among the contact lens wearers at their last follow-up visits was 9.58 hours. Final visual acuity of 6/12 or better was observed in 77.3% of eyes at the end of 22.91 months. CONCLUSION: Large-diameter RGPCLs are better tolerated and lead to significant improvement in visual acuity in inferior PMCD.

Adolescent↗