Incidence of corneal pigmented arc and factors associated with its appearance in orthokeratology.

PURPOSE: To determine the incidence of the corneal pigmented arc in orthokeratology (ortho-k) lens wearers over 12 months of lens wear and the factors associated with its appearance. METHOD: Thirty-five ortho-k subjects were recruited; refractive and corneal changes after lens wear (single-lens protocol) were monitored over 12 months. The incidence of the pigmented arc after 3, 6 and 12 months of lens wear was determined. RESULTS: The incidence of corneal pigmented arc was 17% (27%), 49% (49%) and 90% (93%) after 3, 6 and 12 months lens wear respectively in the left and right eyes. For subjects with arcs observed in the left eye within the first 6 months of lens wear, the mean +/- S.D. period of lens wear before initial detection of the arc was 14 +/- 7.4 weeks, and no correlation was found between this factor and the baseline spherical and cylindrical refractive errors (i.e. refractive sphere and cylinder, respectively), spherical equivalent refractive error (SERE), the target myopia reduction, the amount of refractive sphere (or SERE) reduction and changes in central and peripheral corneal curvatures after 6 months of lens wear. Baseline refractive sphere, baseline SERE, target, amount of myopia reduction, and change in central corneal curvature were significantly larger (p < 0.05) in those subjects with pigmented arcs after about 6 months of lens wear. The intensity of the observed pigmented arcs after about 6 months of lens wear was significantly related to the time when it was first observed (p = 0.003). Significant correlation was also found between the intensity of the arcs and the following parameters: baseline refractive sphere and SERE, target, change in central corneal curvature, and amount of myopia reduction (p < 0.006). After about 12 months of lens wear, the intensity of observed arcs was significantly related to the baseline refractive sphere, SERE and the target (p < 0.006). CONCLUSION: The incidence of ortho-k-associated pigmented arc increases from 17% after 3 months of lens wear to over 90% after 12 months of lens wear. The intensity of the arc is related to the time when the arc first appeared. Both the incidence and the intensity of the arc are related to the period of lens wear, baseline refractive sphere, SERE and the target.     

Asymmetrical increase in axial length in the two eyes of a monocular orthokeratology patient.

To report the myopia progression (change in axial length) of a boy in whom the progression was slower in the eye treated with overnight orthokeratology (ortho-k) than in the fellow eye with no visual correction. An 11-year-old boy was fitted with an ortho-k lens in his left eye in 1999 in a private practice. The refractive errors were OD -0.25 - 0.75 x 168 and OS -2.50 - 0.50 x 170 before commencing ortho-k lens wear. He participated in one of our research studies and made yearly visits to our clinic in 2001, 2002, and 2003. Logarithm of the minimum angle of resolution (logMAR) visual acuity, refraction, ocular health, and axial length were assessed at each visit. At the visit in 2003, the unaided visual acuity was OD 0.40 logMAR and OS -0.04 logMAR. Between 2001 and 2003, there was a small increase in axial length in the left eye (0.13 mm) but a significant increase in the axial length (0.34 mm) with a corresponding increase in spherical equivalent refractive error (0.75 D) in the right eye. This case suggests that myopia progression may have been slowed down by ortho-k lens wear in the eye undergoing treatment of a boy undergoing unilateral ortho-k treatment.     

Microbial flora of tears of orthokeratology patients, and microbial contamination of contact lenses and contact lens accessories.

PURPOSE: The purpose of this study is to determine if there are changes in the ocular flora of overnight orthokeratology (ortho-k) patients, and the levels of contamination of their lenses and lens accessories, and to correlate compliance with levels of contamination. METHOD: Normal ocular flora of 41 subjects was determined twice before commencing ortho-k lens wear by culture of the lower conjunctiva. Further specimens were collected on six follow-up visits after beginning lens wear, as were samples from their lenses, cases, and suction holders. A questionnaire on lens care was administered after the fifth visit. RESULTS: Three subjects provided conjunctival samples yielding Staphylococcus aureus on one occasion before lens wear, one being positive for this organism after beginning lens wear. Of 38 subjects yielding no growth or only normal eye flora before use, 28 remained free of ocular pathogens after beginning lens wear. Only four subjects had positive cultures on more than one occasion after lens wear. There was no significant difference in isolation levels of pathogens with lens wear (p = 0.423). Lens culture of 54% of subjects yielded no growth or normal flora only; lenses of 16 subjects yielded potential pathogens, including three subjects contaminated on more than one occasion. Lens isolates did not match the organisms transiently colonizing the eye. Lens case, the most frequently contaminated item, was associated with lens contamination (p < 0.001), the same organism being isolated from both items in 11 subjects. Lens suction holder was less frequently contaminated. Neither lens case nor suction holder contamination was associated with isolates from the eye. Reported good compliance correlated with lack of contamination in all but one subject. The most frequent breaches in the lens care protocol were failure to clean, disinfect, and replace the lens case. CONCLUSION: Ocular flora was not altered by ortho-k lens wear over an extended period, and patients remained free of infection. Contaminants identified were generally of a transient nature. Most patients had significant contamination of at least one item, most frequently the lens case. Lens case isolates were significantly associated with those from the lens. The majority of patients reporting good compliance had low or no contamination of their lenses and accessories.     

Prolonging contact lens wear and making contact lens wear safer

PURPOSE: To summarize the present status of safety and efficacy of contact lens wear. DESIGN: Literature review. METHODS: Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses. RESULTS: Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses. CONCLUSIONS: The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.     

White lesion in the corneal pigmented ring associated with orthokeratology

The development of the pigmented corneal arc and a white lesion near the inner margin of the arc in a girl wearing overnight orthokeratology (ortho-k) lenses for myopic control is reported. The girl was examined before and followed up every 6 months after the treatment over a 3-year period. The initial spherical equivalent refractive error and keratometric readings (flattest/steepest meridians) were -2.37 D and 45.00 D/46.75 D respectively in the right eye and -3.12 D and 45.25 D/46.00 D respectively in the left eye. She was wearing ortho-k lenses of a four-zone design made of Boston XO material on a nightly basis. The same lens design was used throughout the monitoring period. Corneal topography showed a rather well-centred treatment zone but vision varied between visits because of fluctuations in residual refractive error. The corneal condition of each eye was unremarkable except for the presence of the pigmented corneal arc first observed 6 months after the commencement of the treatment. The intensity of the arc did not change over the years in the right eye but increased in the left eye. A faint white lesion within the inner border of the left pigmented arc was first observed at the end of the second year and it became more obvious at the end of the third year. This lesion appears to be similar to those reported in intense Fleischer's rings associated with keratoconus. Although the presence of the arc may have no clinical ramification, the change in the intensity and the development of the white lesion may reflect an increased stress exerted on the cornea with continued ortho-k lens wear.     

Profile of contact lens failures in Saudi Arabia

Background : Interest in contact lenses is increasing in Saudi Arabia, as in many parts of the world, but unfortunately many patients do not remain contact lens wearers. This paper presents the findings of the first survey on failures in contact lens wear in the Kingdom of Saudi Arabia. The purpose of the survey was to identify the reasons for failure in lens wear in the kingdom. Method : Two hundred previous contact lens wearers, mostly from the university population, were given questionnaires which included, among other items, demographics, length of post-fitting lens wear experience, type of lens worn and reasons for discontinuing lens wear. Data from questionnaires were analysed and presented. Results : Data from questionnaires revealed that 61 per cent of the subjects discontinued contact lens wear due to discomfort, followed by inconvenience of lens care regimen (30.5 per cent), poor vision (5.5 per cent), economy (two per cent) and refractive surgery (one per cent). The length of post-fitting lens wear experience before discontinuation ranged from two to 36 months. The majority had been soft contact lens wearers. Conclusion : The majority failed in contact lens wear due to lens discomfort and the inconvenience of lens care systems. Identification of the reason for failure in contact lens wearers is crucial if refitting is to be considered. This will aid in the selection of the appropriate lens or lens care regimen suitable to the patient and serve as a guide in the prevention of failures in prospective contact lens wearers.)Clin Exp Optom 1996; 79: 6: 255–259)     

Effect of one overnight wear of orthokeratology lenses on tear composition.

PURPOSE: To evaluate the effect of one night of orthokeratology lens wear on ocular surface health based on the changes in tear components, including ascorbate, urate, lactate dehydrogenase (LD), lactoferrin, lipocalin, lysozyme, secretory immunoglobulin A (sIgA), and serum albumin. METHODS: Changes in tear components in eight healthy young men before and after 7-h overnight ortho-k lens wear were studied. Subjects attended on two separate occasions during a 1-week period, on one occasion wearing lens overnight and on the other wearing no lens. Tears (yawn-induced) were collected by capillary tube before lens fitting and on awakening. Tear ascorbate and urate were measured by high-performance liquid chromatography; LD was measured by a commercial kit method; tear proteins were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. RESULTS: Ascorbate, sIgA, albumin, and LD increased significantly overnight with and without overnight lens wear (p < 0.05); however, no significant increases were found in tear urate, lactoferrin, lipocalin, or lysozyme (p > 0.05). Without lens wear, tear ascorbate, sIgA, albumin, and LD increased by 21%, 34%, 9-fold, and 13-fold, respectively (p < 0.05). With ortho-k lens wear, significant flattening of the apical curvature was observed as expected, and the increases in tear ascorbate, sIgA, albumin, and LD (increases were 56%, 76%, 13-fold, and 14-fold, respectively) were significantly (p < 0.05) greater than with no lens. There was significant correlation seen between changes in albumin and LD with (r = 0.762; p = 0.037) and without (r = 0.738; p = 0.046) ortho-k lens wear. CONCLUSIONS: The result of tear ascorbate suggests that corneal cell disturbance is small after one night of ortho-k lens wear. The marked increases in albumin and LD suggest that the ocular surface is under additional hypoxic stress during overnight ortho-k lens wear.     

青少年近视患者配戴角膜塑形镜5年的有效性及安全性

目的 评价青少年近视患者长期配戴角膜塑形镜延缓近视进展的有效性及其对角膜的安全性.方法 回顾性病例系列观察研究.选取2012年1月至2013年12月于天津市眼科医院视光中心配戴角膜塑形镜且连续配戴5 a的153例(153眼)青少年近视患者,分别于戴镜前及戴镜后1a、2a、3a、4a、5a采用裂隙灯显微镜评估角膜状态,采...     

The validity of the Jessen formula in overnight orthokeratology: a retrospective study.

PURPOSE: To investigate the validity of the Jessen formula, with a compression factor of 0.75, in determining the back optic zone radius (BOZR) of an orthokeratology (ortho-k) lens for myopic reduction [i.e. BOZR = flattest K- (target reduction + 0.75)]. METHODS: One hundred and twenty-three consecutive ortho-k patient files from the Optometry Clinic of The Hong Kong Polytechnic University were reviewed. Pertinent data at the preliminary visit and at the morning visit after 2 weeks of lens wear for 63 patients who fulfilled the inclusion criteria were retrieved for analysis. All patients were either fitted with DreimLens (DreimLens Taiwan, Taiwan Macro Vision Group, Taiwan, China) or eLens (E&E Optics Ltd., Hong Kong SAR, China) designs. Only data from the right eye were analysed. The validity of the Jessen formula was evaluated by comparing the equation of the plot of myopic reduction attempted (based on the Jessen formula) and myopic reduction achieved (based on subjective refraction). RESULTS: The Jessen formula was found to underestimate the intended target of myopic reduction following ortho-k. The results suggested that the formula should be revised to BOZR = flattest K- (1.23 target reduction + 1.27). CONCLUSION: If the intention is to overcorrect the ortho-k patient by 0.75 D to allow for regression during the daytime, the Jessen formula with a compression factor of 0.75 is not valid to determine the BOZR of the ortho-k lens designs.     

Specular microscopy of hard contact lens wearers II

Specular microscopy was done on 65 long-term hard contact lens (CL) wearers and controls matched for age, sex, race, and refractive error. There was no difference in mean endothelial cell size between the two groups, although median cell area was slightly smaller in the CL group. Standard deviation and coefficient of variation increased as the duration of total wearing time increased and were greater in the CL group, as was skewness. In 15 long-term hard CL wearers who had discontinued their CL wear, there was a trend towards persistence of pleomorphism and polymegathism of cells compared with non-contact lens (NCL) wearers, but there was a suggestion of recovery compared with those continuing to wear CLs matched for duration of wear.     

Refitting long-term asymptomatic PMMA lens wearers into gas permeable lenses

Controversy exists as to whether patients who are asymptomatic, long term PMMA contact lens wearers demonstrating an acceptable clinical ocular response should be routinely refit into hard gas permeable lenses. Corneal thickness, corneal curvature, and refractive changes were measured on eight such patients when their lenses were changed to a gas permeable lens material (Boston II) while all other lens parameters were held constant. Corneal thickness decreased dramatically, corneal curvature flattened slightly, and refractive findings showed no significant changes. A simple reorder of the current lens design in the gas permeable material has been recommended as a reasonable "refitting" method for this type of patient.     

Corneal iron ring associated with orthokeratology lens wear.

A healthy 27-year-old female with a history of daily wear soft contact lenses requested orthokeratology (ortho-k) treatment and was fitted with a pair of reverse geometry lenses. Two weeks later, a faint brown pigmented arc, with fuzzy margins, extending from four to eight o'clock at the inferior midperipheral part of the corneal surface was observed in both corneas. The patient was asymptomatic and happy with the results of the ortho-k treatment, and topographical maps showed a sharp and slightly decentered bull's eye pattern that indicated a clinically acceptable ortho-k effect for both eyes. The rings extended to a near-complete ring in both eyes and became denser and more significant as lens wear continued. The rings were similar in appearance to Fleischer's rings seen in keratoconic eyes and coincided with the margin of the bull's eye observed in the topographical maps. The patient continued to be asymptomatic with unaided visual acuity of 20/20(+1) (OD) and 20/25(-1) (OS). Apart from the presence of the iron rings bilaterally, the corneal integrity and topography were stable and clinically unremarkable; the patient was allowed to continue wearing the lenses with regular aftercare scheduled on a 3-month basis. Possible etiologies of the formation of iron rings are discussed.     

Intraocular lens power calculation for lens exchange

PURPOSE: To examine patients who had intraocular lens (IOL) exchange for large postoperative refractive errors and determine the factors that contributed to the error in IOL power calculation. SETTING: Thirteen affiliated hospitals in Japan. METHODS: This study comprised 34 cases that required IOL exchange because of large refractive errors after primary lens implantation. Patients with intraoperative complications were excluded from the study. The potential contribution of axial length, corneal refractive power, IOL manufacturer, and IOL fixation to errors in the predicted power was examined retrospectively. Axial length was calculated by the SRK/T and Holladay formulas using refraction after primary IOL implantation. RESULTS: There was no statistical difference between the corneal refractive power before and after cataract surgery. The axial lengths calculated using the SRK/T and Holladay formulas were longer than the ultrasonic axial lengths in 24 and 23 cases, respectively. Using IOLs from the same manufacturer for both primary implantation and exchange reduced the error in predicted refraction. CONCLUSION: Axial length and IOL manufacturer were important factors in predicting refraction power in eyes requiring IOL exchange.     

A multi-centre study of lapsed contact lens wearers

PURPOSE: Discontinuation from contact lens wear has been identified as a contributing factor in the lack of growth of contact lens use in Europe. The purpose of this study was to determine the proportion of lapsed contact lens wearers that can be refitted successfully with contact lenses and to evaluate the reasons for discontinuation from contact lens wear. METHODS: This was a multi-site clinical study involving 15 UK investigators and 236 lapsed contact lens wearers who had previously tried contact lenses and discontinued. The reasons for discontinuation were assessed by subjects, who were then refitted with contact lenses. Investigators subsequently evaluated factors associated with their initial discontinuation. Short-term success was defined as the successful completion of 1 month of contact lens wear with absence of complications that would prevent further wear. Subjects were interviewed by telephone 6 months after being refitted to determine whether they were still wearing contact lenses. Those who were not wearing lenses were questioned about the reasons for discontinuation and their likelihood of resuming lens wear. RESULTS: A majority of subjects (51%) cited discomfort as the principal reason for having previously given up contact lens wear. Problems with vision were the second most common reason (13%), either with reading (6%) or general vision (7%). The most common type of discomfort was dryness (40%). In almost all cases (97%), the investigator's assessment of the reasons for discontinuation agreed with the subject's own assessment but investigators also cited product-related and practitioner-related factors as contributing to previous failure. The short-term success rate for refitting lapsed wearers was found to be 77% (Cl: 70-82%). The highest short-term success rates were for 2-weekly/monthly soft spherical lenses (91%) and daily disposable lenses (89%). Lower success rates were found for soft toric (69%) and soft bifocal (53%) lenses. At the 6-month stage, 73% of those who continued in lenses after the 1-month visit were still wearing contact lenses and a further 18% indicated that they were either 'very likely' or 'likely' to resume lens wear. CONCLUSIONS: A high proportion of lapsed contact lens wearers can be successfully refitted with contact lenses. The prime reason for previous discontinuation from contact lenses is discomfort and, in particular, dryness-related discomfort. In many cases, previous contact lens failure is product or practitioner-related rather than because of patient-specific problems. Once refitted with contact lenses, lapsed wearers cite vision problems rather than discomfort as the most common reason for discontinuing. This finding suggests that recent advances in contact lens material, design, replacement frequencies and care systems have improved the prospects for avoiding lens-related discomfort and for continuing contact lens wear.     

An assessment of consecutively presenting orthokeratology patients in a Hong Kong based private practice

Purpose: The aim of this study was to collect objective, subjective and demographic data on consecutively presenting orthokeratology (ortho‐k) patients who attended for routine followup examination in a Hong Kong based private practice in May 2001. Method: Sixty‐nine patients who returned to the surveyed practice for follow‐up visits during the study period (May 2001) were interviewed and relevant data extracted from their files. Data collected included identification and estimation of the extent of complications encountered by ortho‐k patients and their satisfaction with the treatment. Results: Among the 61 patients who had been wearing ortho‐k lenses for at least one month, 50 patients were younger than 16 years old. Twelve children (24 per cent) had been reluctant to wear ortho‐k lenses before undergoing the treatment but, after commencement of lens wear, only one child was not very willing to wear the ortho‐k lenses. The mean pre‐ortho‐k spherical refractive error of these patients was ‐3.93 ± 2.30 D (OS only). Of the 59 patients who wore ortho‐k lenses for at least one month and who were on night therapy, 10 patients had to wear spectacles or contact lenses in the daytime due to significant residual myopia. There was no statistically significant correlation between post‐ortho‐k unaided visual acuity and pre‐ortho‐k refractive error (spherical, cylindrical or the equivalent sphere) in the 49 patients who did not need to wear any vision correction in the daytime. Of the 61 patients, four reported eye inflammation/infection during the treatment. All recovered their ocular health without any effect on their vision or corneal health. The incidence of corneal staining that required lens wear to be stopped appeared to increase with the duration of ortho‐k lens treatment. The incidence of staining was not related to refractive error, unaided visual acuity or the age of the subjects. The most common problem reported by the patients was lens binding and there were also reports of increased redness, itching, light sensitivity and secretion of mucus in the morning after opening their eyes. More than 50 per cent of the patients experienced some distance vision blur, which was worse towards the end of the day. For most patients, these problems occurred only occasionally. Higher pre‐ortho‐k spherical refractive error was related to poor near and distance vision and worse distance vision towards the end of the day. Conclusion: The majority of the patients interviewed were children who reported being ‘happy with the results of the treatment’. Night wear is the main wearing modality and in view of the increased risk of complications in overnight wear and the fact that a large number of the patients are children, the need for strict compliance with the practitioner's instructions for lens use and care cannot be overemphasised. With careful monitoring and good compliance, complications with overnight ortho‐k wear can be minimised. In view of the high incidence of lens binding, it is essential that patients and parents of young patients know the correct method to free a bound lens.     

A comparison of two techniques of refitting long-term polymethyl methacrylate contact lens wearers

Two techniques for fitting long-term polymethyl methylcrylate (PMMA) lens wearers with a gas-permeable hard lens are compared. These are: complete cessation of all lens wear for the period necessary to achieve stability in the patient's refraction and corneal curvature, and immediate refitting with a Polycon lens. Eleven patients who had worn hard contact lenses for at least 3 years and had wearing times of at least 8 hr per day were refitted with each technique. Refitting with Polycon lenses slowed but did not otherwise inhibit the recuperative changes taking place in the cornea after PMMA lens removal; vision was better and more stable with this group.     

Comparison of reverse-geometry lens designs for overnight orthokeratology.

PURPOSE: The efficacy of overnight wear of four types of reverse-geometry lenses was compared. The length of time needed to achieve correction and any adverse events that occurred during the course of the study were recorded. METHODS: In this prospective, randomized study, 60 subjects (18 to 35 years old) with refractive error between -1.00 to -4.00 D (cyl 相似文献   

Management of the subluxed crystalline lens.

There has been a traditional reluctance to remove a subluxed (ectopic) lens because of the high surgical risk. The use of closed intraocular microsurgical techniques, however, now allows greater intraoperative control with few complications. The authors present the results of subluxed lens extraction, by limbal or pars plana lensectomy, in 44 eyes of 24 patients, in which the indication for surgery was lens subluxation causing a reduction in visual acuity or uncorrectable refractive error. Visual acuity was improved in all cases after surgery, with no significant complications. Patients with reduced visual acuity secondary to ectopic lenses have a good visual prognosis after lensectomy using a closed intraocular microsurgical technique.