Reverse geometry contact lens wear after photorefractive keratectomy, radial keratotomy, or penetrating keratoplasty

CLEAR - Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.

The impact of the Boston ocular surface prosthesis on wavefront higher-order aberrations

PURPOSE

To evaluate the effect of the Boston Ocular Surface Prosthesis (Boston Foundation for Sight) on higher-order wavefront aberrations in eyes with keratoconus, eyes that have undergone penetrating keratoplasty, eyes that have undergone refractive surgery, and eyes with ocular surface diseases.

DESIGN

Prospective, clinical study.

METHODS

The study evaluated 56 eyes of 39 patients with irregular astigmatism who were treated with the Boston Ocular Surface Prosthesis when conventional treatments failed. Patients were sorted into 4 clinical groups based on the underlying cause of irregular astigmatism, including keratoconus (group 1), post-penetrating keratoplasty (group 2), post-refractive surgery (group 3), and ocular surface diseases (group 4). Another 6 eyes of 5 patients who were treated with rigid gas permeable lenses also were evaluated. Best-corrected visual acuity; topographic refractive indices, including spherical, cylindrical, spherical equivalent values; and higher-order and total wavefront aberration errors were noted at baseline and after fitting the lens.

RESULTS

In all groups, higher-order wavefront aberration error was noted to decrease significantly in eyes wearing the Boston Ocular Surface Prosthesis (P<.001, P=.001, P=.002, and P=.001, respectively). By post hoc analysis, significant differences in the level of higher-order aberrations were observed only between groups 1 and 4 (P=.012) and groups 1 and 2 (P=.033). In the overall group, mean correction rate of higher-order aberration error with the Boston Ocular Surface Prosthesis was 72.3%. However, in eyes with rigid gas permeable lenses, 2 eyes demonstrated increased higher-order aberration error, whereas the mean correction rate in other 4 eyes was only 42.5%.

CONCLUSIONS

With its unique structure, the Boston Ocular Surface Prosthesis was found to be very effective in reducing higher-order wavefront aberrations in patients with irregular astigmatism resulting from a number of corneal and ocular surface conditions who had not responded satisfactorily to conventional methods of optical correction.

Incidence of Rigid Gas-Permeable Contact Lens Wear After Keratoplasty for Keratoconus

PURPOSE

To review retrospectively the charts of all 190 patients who underwent penetrating keratoplasty for keratoconus in one hospital during a 5-year period (1995-2000), with special attention paid to contact lens fitting.

METHODS

The frequency of postoperative contact lens use, the time to fit lenses after grafting, tolerance and visual acuity, and postoperative risks for the graft were studied.

RESULTS

The authors successfully fitted large-diameter (12 mm) tricurve rigid gas-permeable contact lenses for 90 (47%) of 190 penetrating keratoplasty patients with good tolerance. There were nine dropouts, and 91 eyes were corrected in another way. Fitting contact lenses after grafting usually started after 8.5 months (range, 1-60 months). The average tolerance was 9.2 hours a day (range, 2-12 hours), and best-corrected visual acuity was 20/25 (range, 20/16-20/200). The average follow-up was at least half a year. The average age of the patient at the first lens fitting was 36.2 years (range, 14-75 years). There was no increased risk in graft rejection.

CONCLUSIONS

Twelve-millimeter rigid gas-permeable contact lens wear was successful in 47% of patients who underwent penetrating keratoplasty for keratoconus. It does not interfere with the use of chronic postoperative topical medication, nor does it increase the risk of corneal graft rejection. It is necessary to recommend likely use of contact lenses to patients who have undergone grafting surgery.

Correlations Between Central and Peripheral Changes in Anterior Corneal Topography After Myopic LASIK and Their Implications in Postsurgical Contact Lens Fitting

PURPOSE

To investigate the changes in central and peripheral anterior corneal curvatures after myopic laser in situ keratomileusis (LASIK) and to correlate them with the manifest refractive change to discuss how such results could affect post-LASIK corneal topography profiles and midterm stability and their implications in postsurgical contact lens fitting.

METHODS

Topographic and refractive data from 18 eyes of 11 patients that had undergone myopic LASIK were collected for 6 months after surgery. Short-term and midterm topographic responses were investigated and correlated with spherical equivalent manifest refractive changes.

RESULTS

There was a strong correlation between eccentricity changes and manifest refractive change 15 days after surgery (r = 0.753, P < 0.001), with no significant changes thereafter for the following 6 months (r = 0.148, P = 0.114). A strong linear relationship was found between baseline manifest refraction and changes in corneal curvature at the center (r = 0.810, P < 0.001), 4-mm chord (r = 0.895, P < 0.001), and 6-mm chord (r = 0.696, P < 0.001). Statistically significant changes were also found after the first 15 days (P < 0.005) and showed a regression effect that affects the three zones. In this case, a weaker relationship was found between curvature regression and the final refractive change for the central location (r = 0.412, P = 0.004), 4-mm chord area (r = 0.430, P = 0.003), and 6-mm chord area (r = 0.283, P = 0.023). CONCLUSIONS.: After myopic LASIK, the anterior corneal dioptric power is expected to change, on average, approximately 77% of the attempted spherical equivalent correction at the center; 60% at the 4-mm chord region, where the stronger correlation between topographic and refractive change is found; and 30% at the 6-mm chord area. The paracentral area 4 mm from the center seems to be more likely to predict baseline corneal curvature from manifest refractive change. Some degree of regression in the midterm period is expected to occur after myopic LASIK, which shows a significant correlation with the manifest refractive change. Again, this effect is more evident and more accurately predicted at the 4-mm chord area. The results of the current study are of interest for those fitting contact lenses after myopic LASIK.

Contact lenses and special back surface design after penetrating keratoplasty to improve contact lens fit and visual outcome

AIMS

To describe the fitting of patients with high or irregular astigmatism following penetrating keratoplasty with contact lenses and to answer the question whether or not contact lenses with special back surface design can improve visual acuity in complex cases after penetrating keratoplasty.

METHODS

28 eyes were included. They were fitted with contact lenses with a special back surface that was designed for optical rehabilitation after penetrating keratoplasty. Four different types of these lenses (tricurve, keratoconus, reverse, oblong) were used selectively depending on abnormal eccentricity determined by videokeratoscope. The patients were followed up for an average period of 15.5 months. Lens tolerance and corrected visual acuity were evaluated and compared with that corrected with spectacles.

RESULTS

The visual acuity was significantly improved in nearly all eyes with an average increase of 3.6 lines (maximal nine lines) accompanied by good contact lens tolerance and satisfactory contact lens fit. No noticeable complications were observed.

CONCLUSION

Contact lenses with special back surface design can improve visual results and lens tolerance, and minimise problems in contact lens fitting. This is in favour of contact lenses as an alternative to surgical procedures for correction of high or irregular astigmatism after penetrating keratoplasty. This procedure is recommended especially in cases of patients who decline further operative interventions.

Comparison of Axial and Tangential Topographic Algorithms for Contact Lens Fitting After LASIK

PURPOSE

Computerized videokeratography (CVK) has become the standard method for measuring the corneal curvature after refractive surgery. However, few resources exist on the use of CVK data for postoperative contact lens fitting, and no recommendations exist on the selection of the best topographic algorithm relevant to gas-permeable (GP) lens fitting. This study assessed the optimal use of topographic data to fit spherical GP contact lenses on patients who have undergone laser in situ keratomileusis.

METHODS

A retrospective analysis of CVK maps from eight post-LASIK eyes fitted with spherical GP lenses was performed in the Contact Lens Service of the Department of Ophthalmology at Case Western Reserve University and University Hospitals of Cleveland. Axial and tangential maps from the Dicon CT 200 (version 3.50) or Humphrey Atlas (version A8) topographer were analyzed. Averaged dioptric curvatures from different locations (inferior, superior, and temporal) at various distances (2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, and 4.0 mm) from the vertex normal of each eye were compared with the base curves of the prescribed GP contact lenses.

RESULTS

One-way analysis of variance, Pearson correlation analysis, and paired t tests showed that the best topographic predictors of a successful GP base curve were the average curvatures at the 4.0 mm distance on the axial maps (r=0.8078, P=0.05) and at the 2.0 mm distance on the tangential maps (r=0.9738, P=0.0002). The mean dioptric powers of the GP base curve, axial map 4.0 mm curvature, and tangential map 2.0 mm curvature were 41.50 diopters (D), 42.65 D, and 42.67 D, respectively.

CONCLUSION

To simplify and guide GP fitting after LASIK, the average dioptric curvature 4.0 mm from the vertex normal on axial maps or 2.0 mm from the vertex normal on tangential maps are the best predictors of accurate GP base curve selection.

Optimization of contact lens fitting in keratectasia patients after laser in situ keratomileusis

PURPOSE

To evaluate the clinical outcomes of contact lens fitting in eyes with keratectasia after laser in situ keratomileusis (LASIK) to optimize the performance of the contact lenses.

SETTING

Contact Lens Clinic, Seoul National University Hospital, Seoul, Korea.

METHODS

Six eyes of 4 patients with keratectasia were examined. Keratectasia was diagnosed based on abnormal topographic findings, progressive myopic changes, and uncorrected visual acuity with glasses. A multicurve lens or reverse-geometry lens (RGL) was selected based on the anterior elevation map. The base curve radius and peripheral parameters were determined based on the axial map and the evaluation of the fluorescein pattern of the lens. The contact lens fitting characteristics and visual acuity were evaluated. Patients were interviewed about their level of comfort, daily contact lens wear time, and glare.

RESULTS

Multicurve lenses and RGLs were fitted in 4 eyes and 2 eyes, respectively. The base curve radius of the multicurve lenses ranged from 7.2 to 7.5 mm; the alignment curve radius of RGLs was 7.6 mm in both cases. The radii of peripheral curves were customized to enhance tear interchange. Visual acuity improved to 20/30 or better in all eyes. All patients were completely satisfied with the comfort of the fitting. The mean daily wearing time was 12.7 hours. One patient reported tolerable glare in the eye after being fitted with an RGL.

CONCLUSION

Proper contact lens fitting based on topographic data and slitlamp evaluation allowed good visual rehabilitation and comfortable extended daily wear in patients with keratectasia after LASIK.

Management options for the flat corneal graft

The post-penetrating keratoplasty (PK) corneal profile may be unpredictable and visual rehabilitation can be difficult. A case series of 11 such patients with flat corneal topography is presented and their management described. Suture removal may not provide a sufficient re-modelling effect to restore convexity of the cornea to enable satisfactory contact lens fitting and reverse geometry (RG) lenses have an important role.

Contact lens fitting following unsuccessful refractive surgery

A retrospective review of case notes of consecutive patients referred to a contact lens clinic after unsuccessful refractive surgery was carried out to determine the success of contact lens fitting. The main outcome variables in determining success were visual improvement, contact lens tolerance, fitting characteristics and wearing time. Thirteen eyes were fitted with conventional rigid gas permeable (CRGP), 10 with soft and 19 with reverse geometry rigid gas permeable contact lenses (RVG). The mean spectacle visual acuity (VA) was 6/9 (20/30) [range: 6/24 (20/80) to 6/5 (20/15)] and the mean VA after contact lens fitting was 6/6 (20/20) [range: 6/18 (20/60) to 6/5 (20/15)]. Of the 42 eyes, the contact lens VA was better than spectacle acuity in 25 (59.5%) eyes, equal in 14 (33.3%) and worse in three (7.1%). A total of 33 (78.6%) eyes were still wearing their lenses at the last visit. Contact lenses can be a valuable method of managing poor VA after refractive surgery.

RK4 (reverse-geometry) contact lens fitting after penetrating keratoplasty

PURPOSE

We evaluated the performance of the RK4 (reverse-geometry) contact lens in patients with flat central and steep peripheral corneal topography after penetrating keratoplasty (PK).

METHODS

A retrospective study was performed of post-PK patients fitted with RK4 lenses on the Cornea Service at Wills Eye Hospital, between March 2000 and February 2002.

RESULTS

Fifteen eyes of 13 post-PK patients were fitted with RK4 lenses and monitored for more than two months (range, 2.1-23.5 months; mean, 8.1 +/- 7.0 months). The average number of lens refits per eye was 1.0 +/- 1.2 (range, 0-4). Ninety-three percent (14/15) of the eyes that were fitted achieved at least 20/30 visual acuity, and 53% (8/15) of eyes achieved 20/20 visual acuity. A comparison of prefitted and post-fitted corrected visual acuity demonstrated a statistically significant improvement (P < 0.01). RK4 lenses were successfully worn full time or part time in all cases.

CONCLUSIONS

The RK4 lens can provide well-tolerated visual correction in cases with central flat, peripheral steep corneal contour following PK.

Night vision disturbances after corneal refractive surgery

A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.