Visual Rehabilitation With Contact Lenses After Laser in situ Keratomileusis

The effect of scleral lenses on vision, refraction and aberrations in post-LASIK ectasia, keratoconus and pellucid marginal degeneration

PURPOSE

To quantify the effect of a single scleral lens design on visual acuity and ocular higher-order aberrations in eyes with post-LASIK ectasia, keratoconus and pellucid marginal degeneration (PMD) that could not achieve satisfactory vision with spectacles or soft contact lenses.

METHODS

Forty-six eyes of 28 participants fitted with diagnostic scleral lenses (KeraCare) were analysed, including 19, 15 and 12 eyes with post-LASIK ectasia, keratoconus and PMD, respectively. Corrected distance visual acuity (CDVA) and ocular aberrations were measured prior to lens wear and during lens wear after 60 min of settling. An i-Trace aberrometer was used to determine aberrations over a 4.5 mm diameter pupil.

RESULTS

Before lens wear, the median (95% confidence interval) values across all groups were: CDVA 0.30 (0.30, 0.40) logMAR, spherical equivalent refraction -2.75 (-5.25, -2.12) D, cylindrical refraction 3.75 (2.50, 5.00) D, higher-order-root-mean-square error (HO-RMS) 0.90 (0.64, 1.03) μm and vertical coma co-efficient C(3,-1) -0.32 (-0.42, -0.12) μm. RMS coma of 0.52 (0.40, 0.74) μm was higher for the keratoconus group than for the other groups (p < 0.05). During lens wear, values improved considerably across all groups: CDVA 0.0 (0.0, 0.00) logMAR, spherical equivalent refraction -0.50 (-0.75, +0.50) D, cylindrical refraction 0.50 (0.00, 0.50) D, HO-RMS 0.32 (0.26, 0.42) μm and C(3,-1) +0.12 (+0.02, +0.19) μm (all p < 0.001 compared to pre-lens wear). While reduced significantly, RMS coma remained higher in the keratoconus group at 0.35 (0.31, 0.52) μm than in the post-LASIK ectasia and PMD groups at 0.17 (0.12, 0.21) μm and 0.07 (0.02, 0.46) μm, respectively (p < 0.05).

CONCLUSIONS

The KeraCare scleral contact lens reduced ocular aberrations and improved visual acuity in patients with post-LASIK ectasia, keratoconus and PMD. The sign of vertical coma changed in keratoconus and PMD.

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.

Visual rehabilitation and outcomes for ectasia after corneal refractive surgery

PURPOSE

To analyze the visual outcomes and method of final visual correction in eyes with corneal ectasia after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

SETTING

Emory University Department of Ophthalmology and Emory Vision, Atlanta, Georgia, USA.

METHODS

This retrospective review comprised 74 eyes of 45 patients with corneal ectasia after LASIK (72 eyes) or PRK (2 eyes). Outcomes included postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best corrected visual acuity (BCVA), and refraction; method of final visual correction; and time to rigid gas-permeable (RGP) contact lens failure.

RESULTS

Corneal ectasia developed a mean of 19.2 months after surgery. Postoperatively, the mean UCVA was 20/400 and the mean BSCVA before ectasia management was 20/108. After ectasia management, the mean BCVA was 20/37 and the final BCVA was 20/40 or better in 78% of eyes. Final visual correction was achieved with RGP lenses in 77% of eyes, spectacles in 9%, collagen crosslinking in 3%, intracorneal ring segments in 1%, and penetrating keratoplasty (PKP) in 8%. Two eyes with intracorneal ring segments required segment explantation and subsequent PKP. One eye that had PKP had a graft-rejection episode; there were no graft failures. Two eyes (3%) did not require a visual device to improve visual acuity. The mean time for successful RGP lens wear was 24.8 months; 80% of cases initially managed with RGP lenses were successful with this form of treatment.

CONCLUSIONS

The majority of eyes developing postoperative corneal ectasia achieved functional visual acuity with RGP lens wear and did not require further intervention. Penetrating keratoplasty can usually be postponed or avoided by alternative methods of visual rehabilitation; however, PKP, when necessary, can provide good visual outcomes.

Oxygen Transmissibility of Piggyback Systems With Conventional Soft and Silicone Hydrogel Contact Lenses

PURPOSE

To investigate the apparent oxygen transmissibility of various piggyback systems using conventional and silicone hydrogel soft contact lenses of different water content and permeability, rigid poly(methyl methacrylate), and rigid gas-permeable lenses of medium, high, and ultrahigh oxygen permeability. The aim of the study was to establish which material (rigid or hydrogel) is more representative of the resulting oxygen performance of piggyback systems.

METHODS

The apparent oxygen transmissibility of 66 piggyback systems was measured with an electrochemical method. Eighteen of these combinations involved the use of silicone hydrogel contact lenses currently available. One hyperpermeable rigid gas-permeable contact lens (tisilfocon A) was also included in the study.

RESULTS

Measured apparent transmissibility correlates with rigid lens permeability (r = 0.403; SE = +/-3.03 barrer/cm; P < 0.001) and hydrogel lens permeability (r = 0.334; SE = +/-3.2 barrer/cm; P < 0.001). As expected, a linear model comprising permeability values from both rigid and soft materials gave a more precise estimation of the piggyback transmissibility (r = 0.736; SE = +/-2.02 barrer/cm; P < 0.001). The highest values of apparent oxygen transmissibility were found for the combination of tisilfocon A rigid material with any of the 3 silicone hydrogel lenses. Tisilfocon A material significantly improved the transmissibility of all piggyback systems even when conventional hydrogels are involved.

CONCLUSION

The combination of hypertransmissible rigid gas permeable lenses with silicone hydrogel soft materials should result in normal corneal function under daily wear conditions. When fitting piggyback systems, clinicians must be aware of material selection to optimize oxygen performance. This is of particular importance in already compromised corneas.

Contact lens overrefraction variability in corneal power estimation after refractive surgery

PURPOSE

To evaluate the accuracy and precision of the contact lens overrefraction (CLO) method in determining corneal refractive power in post-refractive-surgery eyes.

SETTING

Refractive Surgery Service and Contact Lens Service, University of Illinois, Chicago, Illinois, USA.

METHODS

Fourteen eyes of 7 subjects who had a single myopic laser in situ keratomileusis procedure within 12 months with refractive stability were included in this prospective case series. The CLO method was compared with the historical method of predicting the corneal power using 4 different lens fitting strategies and 3 refractive pupil scan sizes (3 mm, 5 mm, and total pupil). Rigid lenses included 3 9.0 mm overall diameter lenses fit flat, steep, and an average of the 2, and a 15.0 mm diameter lens steep fit. Cycloplegic CLO was performed using the autorefractor function of the Nidek OPD-Scan ARK-10000. Results with each strategy were compared with the corneal power estimated with the historical method. The bias (mean of the difference), 95% limits of agreement, and difference versus mean plots for each strategy are presented.

RESULTS

In each subject, the CLO-estimated corneal power varied based on lens fit. On average, the bias between CLO and historical methods ranged from -0.38 to +2.42 diopters (D) and was significantly different from 0 in all but 3 strategies. Substantial variability in precision existed between fitting strategies, with the range of the 95% limits of agreement approximating 0.50 D in 2 strategies and 2.59 D in the worst-case scenario. The least precise fitting strategy was use of flat-fitting 9.0 mm diameter lenses.

CONCLUSIONS

The accuracy and precision of the CLO method of estimating corneal power in post-refractive-surgery eyes was highly variable on the basis of how rigid lense were fit. One of the most commonly used fitting strategies in clinical practice--flat-fitting a 9.0 diameter lens-resulted in the poorest accuracy and precision. Results also suggest use of large-diameter lenses may improve outcomes.

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.

Management of a post-ELLKAT keratectasia with a gas permeable contact lens

BACKGROUND

The Excimer laser keratoplasty of augmented thickness for keratoconus (ELLKAT) has been proposed for the refractive management of keratoconus.

CASE REPORT

A 41-year-old man with a history of bilateral keratoconus came to the clinic for a contact lens. He had undergone an ELLKAT procedure in his right eye some months earlier in an attempt to obtain acceptable unaided vision. As the result in this eye was not positive, the surgery in the fellow eye was cancelled. On examination, I diagnosed a centrally located keratectasia (KE) in his RE. After surgery, the corneal shape presented some complications in relation to contact lens fitting. The patient was able to achieve 6/9.6 acuity with adequate comfort with a Soper lens using a "modified three-point touch" relationship.

CONCLUSIONS

The surgical procedure of ELLKAT can exhibit some advantages with regard to the penetrating keratoplasty. In this case, because a keratectasia was induced, a contact lens fitting was needed to restore vision. A gas permeable contact lens with a Soper design and with a "modified three-point touch" fitting was a viable clinical solution. The fitting of contact lenses in cases of keratectasia can be a practical solution that may avoid the need for further surgery.

Therapeutic Effects of Contact Lenses After Refractive Surgery

PURPOSE

Although highly successful, refractive surgery can have adverse effects, such as loss of best spectacle-corrected visual acuity, glare, haloes, monocular polyopia, and loss of contrast. Further surgical intervention may no longer be an adequate or appropriate response. The efficacy of rigid gas-permeable contact lenses and their therapeutic effects in managing these conditions are studied.

METHODS

A retrospective review of the records of 67 eyes of 37 patients fitted with contact lenses after different refractive surgeries was performed. The most successful lens design for each patient was evaluated. Klyce corneal statistics of surface regularity index and surface asymmetry index, mean keratometric values, and optical zone diameter were measured before and after contact lens wear using the Tomey TMS-2 topographer. Comparative wavefront aberrometry was obtained for five eyes of three patients.

RESULTS

The cohort had a mean uncorrected visual acuity of 20/40, a mean best spectacle-corrected visual acuity of 20/26, and a mean visual acuity with contact lenses of 20/20. Contact lens wear resulted in significant improvements in corneal regularity and symmetry, as indicated by Klyce corneal statistics, with concomitant improvements in visual acuity between wearing periods. The mean visual acuity on lens removal was 20/24. This lens molding effect lasted from several hours to several days. The lenses also had the effects of decreasing higher-order aberrations, as measured by wavefront aberrometry in three patients.

CONCLUSIONS

Rigid gas-permeable contact lenses can dramatically improve visual acuity and higher-order aberrations in eyes of patients with unsatisfactory refractive surgery outcomes. Contact lenses can also have a measurable therapeutic effect on vision when the lenses are not being worn or cannot be worn full time.

Survey of complications and recommendations for management in dissatisfied patients seeking a consultation after refractive surgery

PURPOSE

To review complications associated with and management options for dissatisfied patients seeking a consultation after refractive surgery performed elsewhere.

SETTING

Refractive Eye Surgery Center, The Wilmer Institute, Lutherville, Maryland, USA.

METHODS

In this retrospective review, charts of consecutive dissatisfied patients who sought a refractive consultation between June 1999 and January 2003 after refractive surgery performed elsewhere were reviewed and the following parameters were analyzed: visual acuity (uncorrected and best spectacle corrected), prior manifest refraction, complications, and recommendations. The subjective complaints, complications, and visual acuity were reviewed, and the associated historical or visual risk factors as well as treatment options were analyzed.

RESULTS

One hundred sixty-one eyes in 101 patients with ocular complaints were identified. One hundred thirty-four eyes (83.2%) had had laser in situ keratomileusis; 22 eyes, photorefractive keratectomy; 4 eyes, radial keratotomy; and 1 eye, laser thermokeratoplasty. The most common subjective complaints were blurred distance vision (59.0%), glare and night-vision disturbances (43.5%), and dry eyes (21.1%). The most common complications were overcorrection (30.4%), irregular astigmatism (29.8%), dry eyes (29.8%), glare (26.1%), difficulty with night driving (16.7%), and corneal haze (16.7%). The most common cause identified in eyes with best spectacle-corrected visual acuity worse than 20/40 was irregular astigmatism (10 of 18 eyes [55.5%]). The most common recommendation for management was medical treatment or observation (68.3%). Medical therapies recommended included lubrication, punctal plugs, topical and systemic pharmaceutical agents to modulate ocular surface, spectacles, and contact lenses. Keratoplasty (lamellar or penetrating) was recommended in 4 patients (4 eyes [2.5%]). The diagnoses included corneal ectasia in 3 eyes and severe flap complication with irregular astigmatism in 1 eye. Nine patients (5.6% eyes) required nonkeratoplasty surgery. In other patients, waiting for advances in technology, including wavefront-guided customized retreatment, was recommended.

CONCLUSIONS

A spectrum of complications associated with refractive surgery may result in patient dissatisfaction. Proper patient selection, prevention strategies, and prompt diagnosis and medical or surgical intervention may be beneficial in managing complications and improving patient satisfaction.

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.

Risk factors and prognosis for corneal ectasia after LASIK

PURPOSE

To review cases of corneal ectasia after laser in situ keratomileusis (LASIK), identify preoperative risk factors, and evaluate methods and success rates of visual rehabilitation for these cases.

DESIGN

Retrospective nonrandomized comparative trial.

PARTICIPANTS

Ten eyes from seven patients identified as developing corneal ectasia after LASIK, 33 previously reported ectasia cases, and two control groups with uneventful LASIK and normal postoperative courses: 100 consecutive cases (first control group), and 100 consecutive cases with high myopia (> 8 diopters [D]) preoperatively (second control group).

METHODS

Retrospective review of preoperative and postoperative data for each case compared with that of previously reported cases and cases with uneventful postoperative courses.

MAIN OUTCOME MEASURES

Preoperative refraction, topographic features, residual stromal bed thickness (RSB), time to the development of ectasia, number of enhancements, final best-corrected visual acuity (BCVA), and method of final correction.

RESULTS

Length of follow-up averaged 23.4 months (range, 6-48 months) after LASIK. Mean time to the development of ectasia averaged 16.3 months (range, 1-45 months). Preoperative refraction averaged -8.69 D compared with -5.37 D for the first control group (P = 0.005). Preoperatively, 88% of ectasia cases met criteria for forme fruste keratoconus, compared with 2% of the first control group (P < 0.0000001) and 4% of the second control group (P = 0.0000001). Seven eyes (70%) had RSB <250 microm, as did 16% of eyes in the first control group and 46% of the second control group. The mean RSB for ectasia cases (222.8 microm) was significantly less than that for the first control group (293.6 micro m, P = 0.0004) and the second control group (256.5 microm; P = 0.04). Seven eyes (70%) had enhancements. Only 10% of eyes lost more than one line of BCVA, and all patients eventually achieved corrected vision of 20/30 or better. One case required penetrating keratoplasty (10%), while all others required rigid gas-permeable contact lenses for correction.

CONCLUSIONS

Significant risk factors for the development of ectasia after LASIK include high myopia, forme fruste keratoconus, and low RSB. All patients had at least one risk factor other than high myopia, and significant differences remained even when controlling for myopia. Multiple enhancements were common among affected cases, but their causative role remains unknown. We did not identify any patients who developed ectasia without recognizable preoperative risk factors.