[Reis-Buckler dystrophy: therapeutic photo-ablation with the excimer laser]

PURPOSE

Reis-Buckler's corneal dystrophy consist of superficial reticulated opacities with recurring attacks of corneal erosion. Lamellar and penetrating keratoplasties were the traditional surgical means of improving recurrent erosions and vision but the dystrophy recurs following surgery. Phototherapeutic keratectomy (PTK) is now the standard method of managing this anterior corneal disease when intervention is required.

MATERIAL AND METHODS

We have treated ten eyes with Reis-Buckler's dystrophy using Excimer laser PTK.

RESULTS

All of patients achieved visual improvement (preoperative corrected visual acuity: average 0.3 +/- 0.2 SD, postoperative at one month 0.6 +/- 0.3 SD and 0.7 +/- 0.2 SD at one year. The refractive shift changed from a spherical equivalent of -0.92 D to a postoperative refraction of +1.80 D at one month and +1.65 D at one year.

PMMA model of steep central islands induced by excimer laser photorefractive keratectomy

We designed a polymethyl methacrylate (PMMA) model of refractive steep central islands (CIs) induced by PRK. A standardized photorefractive ablation procedure was performed using seven different excimer lasers on test PMMA specimens including 70 flat plates and 98 convex contact lenses. The resulting surface was analyzed by high-resolution confocal microscopy and computerized videokeratoscopy using both TMS-1 and CAS-2000 systems. A total of 50 (54.9%) CIs were observed using computerized videokeratoscopy. The rate of occurrence of CIs was significantly reduced by shock wave absorption (P = 0.0001), aspiration of fumes (P = 0.0044), and smaller diameter ablation (P = 0.0296). The diameter of the CIIs was significantly increased for broad-beam mode ablation (P = 0.016) and for larger ablation zones, (P = 0.042). The refractive power of CIs was significantly increased in the absence of a shock wave absorption system (P = 0.001). Only 20 (40%) of the CIs detected by the TMS-1 device were identified on CAS-2000 at a 0.5 diopter (D) scale resolution level. Shock wave induced deformation and subsequent dynamic alteration of convection forces applied to emitted particles may be the primary mechanism underlying the formation of CIs after PRK, regardless of any biological response of the ablated tissue. Reported rates and characteristics of CIs may largely depend upon the specific design of videokeratoscopes.

[Computerized video-keratoscopic analysis and cataract surgery by phacoemulsification. Predictive calculation of the power of the intraocular implant]

PURPOSE

The authors present the results of a prospective study of 125 consecutive cases of phacoemulsification, performed by a single surgeon, to assess the benefit of computerised videokeratoscopy for the improvement of the predictive calculation of the power of intraocular lenses (IOL).

METHODS

Preoperative keratometry was determined by means of 3 concurrent techniques, including automated kerato-refractometry (AKR 2000, Nidek) and videokeratoscopy by TMS-1 (Tomey) and CAS-1 (EyeSys). The results of the IOL calculation by these 3 methods was compared postoperatively to the power of the actual IOL yielding emmetropia as calculated by the optical method based on the postop, refraction at the various time-points.

RESULTS

Simulated values obtained with videokeratoscopy significantly reduced the refractive error at 1 postop, week (p = 0.001), one month (p = 0.002) and 3 months (p = 0.002) for the CAS1 and at 3 months (p = 0.002) for the TMS1, as compared to values obtained with conventional automated keratometry. The refractive error was significantly reduced with the CAS1 at one month (p = 0.001) and 3 months (p = 0.019) as compared to TMS1.

CONCLUSION

The determination of the anterior curvature of the entrance pupil by videokeratoscopy significantly improves the predictive calculation of the IOL power.

Ultrasound Biomicroscopy of Baikoff Anterior Chamber Phakic Intraocular Lenses

BACKGROUND

The purpose of the study was to analyze qualitatively and quantitatively anatomic relationships of anterior chamber Baikoff phakic intraocular lenses (IOL) to the cornea, angle, iris, and lens in myopic eyes.

METHODS

Thirteen phakic myopic eyes (-9.00 to -15.00 diopters) corrected by minus power, angle-supported, anterior chamber intraocular lenses of the ZB5M style (Chiron-Domilens), with a mean follow-up of 25 months (range 18 to 36 months), were examined clinically and by ultrasound biomicroscopy.

RESULTS

The mean distance (+/- SD) between the central cornea and the IOL was 2.05 +/- 0.18 mm (range 1.8 to 2.47 mm); mean distance between the corneal periphery and the IOL was 1.56 +/- 0.17 mm (range 1.33 to 1.95 mm); and the mean distance between the IOL and the lens was 0.58 +/- 0.12 mm (range 0.48 to 0.81 mm). IOL footplates seemed to be correctly positioned in the angle in all eyes. We observed no goniosynechiae. In six eyes, we found localized posterior indentation of the iris caused by the haptics. Four of these six eyes exhibited oval pupils associated with an oversized IOL.

CONCLUSIONS

High frequency ultrasound biomicroscopy can define anatomic relationships of anterior chamber phakic IOLs, and help analyze the mechanisms of corneal and iris complications.

[Posterior scleral reinforcement surgery]

Scleral reinforcement is proposed to stabilize the visual acuity in patients with macular myopic staphyloma. Although many patients have been treated, this procedure is still debated.

PURPOSE

Evaluation of the feasibility of scleral reinforcement and the operative risk of this procedure.

PATIENTS AND METHODS

Patients were eligible for this prospective study patients with a clinical history of visual loss, staphyloma concerning the macular area associated with atrophic lesion and or lacquer cracks. Sixteen eyes in 13 successive patients have been operated on with a single band of PTFE.

RESULTS

At the last examination, visual acuity was unchanged for 14 cases. In one case, an improvement of the vision was related to the disappearing of a macular detachment by shortening of the axial length. In one case, vision decline was associated with inadequate band position. Diplopia occurred in 2 cases. A choroidal detachment, and a vitreous haemorrhage disappeared without sequelae.

CONCLUSION

An accurate technique is necessary to avoid operative risk. Further long term studies are needed to assess the benefit of scleral reinforcement.

Full panretinal photocoagulation and early vitrectomy improve prognosis of florid diabetic retinopathy

BACKGROUND

Florid diabetic retinopathy (FDR) is a rare form of proliferative diabetic retinopathy (PDR) that is characterized by a bilateral rapidly progressive, very severe ischemic retinopathy. Florid diabetic retinopathy was reported to carry a high risk of blindness. This study was conducted to determine whether visual prognosis of FDR can be improved by appropriate photocoagulation and surgical management.

METHODS

The authors retrospectively studied 20 patients (40 eyes) who were treated from October 1978 to February 1994. Systemic risk factors, visual acuity, complete ocular examination, and fundus findings, as well as fluorescein angiography, were analyzed with respect to photocoagulation and surgical management. Mean follow-up was 3.6 years.

RESULTS

All patients had poorly controlled type I diabetes (mean duration, 13.5 years), which often was associated with systemic complications. Mean initial visual acuity was equal to or better than 20/40 in 32 eyes (80%). During the course of the study, high-risk PDR was observed in 38 eyes (95%) and vitreous hemorrhage occurred in 26 eyes (65%). Extensive full subconfluent panretinal photocoagulation was performed completely in 37 eyes (92.5%). Vitrectomy was necessary in 15 eyes (37.5%). Macular edema was present in 30 eyes (75%). Major complications included retinal detachment that required surgery (2 eyes, 5%) and neovascular glaucoma (2 eyes, 5%). However, final visual acuity was equal to or better than 20/40 in 23 eyes (57.5%) and less than 5/200 in only 4 eyes (10%).

CONCLUSION

These results suggest that aggressive treatment of FDR with extensive panretinal photocoagulation and early vitrectomy, when necessary, may result in a much better prognosis than has been reported previously.

Effect of platelet-derived growth factor on rabbit corneal wound healing

Human recombinant platelet-derived growth factor was evaluated with the use of wound healing models in New Zealand albino rabbits. The efficacy of the platelet-derived growth factor dimers, AA, AB, and BB, was determined in corneal reepithelialization and anterior keratectomy models which examined the healing response in the presence or absence of the basement membrane. All dimers increased the rate of wound healing in both models at 100 microg/ml when compared with control; however, the platelet-derived growth factor-BB isoform showed the most dramatic increase in both studies. The strength of the healing stroma after incision was evaluated by means of a tensile strength model. Histologic evaluation of the stromal wound area after 9 days of healing showed a marked increase in the number of keratocytes within the wound bed of the corneas treated with platelet-derived growth factor-BB when compared with control corneas. In addition, at 9 days, the epithelial plug was still present in the control corneas but had been extruded to the surface by the granulation tissue in the platelet-derived growth factor-BB-treated corneas. These results are indicative of a more advanced stage of healing in treated versus control wounds at 9 days after the operation. A 30% increase in corneal tensile strength versus control was noted after 21 days of healing. Finally, in an in vitro gel contraction assay, platelet-derived growth factor exhibited a dose-dependent effect on the contraction of fibroblasts for doses ranging from 0.01 to 10 ng/ml. These results indicate that platelet-derived growth factor is active in the corneal wound healing process.

Synthetic scleral reinforcement materials: I. Development and in vivo tissue biocompatibility response

The surgical treatment of pathological myopia involves the placement of a band cut from donor sclera around the back of the globe to provide support and to prevent elongation that leads to retinal detachment and blindness. In the search for a synthetic material that would overcome the disadvantages of the donor tissue band, we tested 11 types of bands made from 14 polymers in rabbit eyes. Bands were cut from porous and solid materials, as well as porous materials coated with solids and solid materials with porous patches affixed to the posterior surface. Criteria for suitability and biocompatibility included ease of placement and suturing, stable positioning, and absence of long-term tissue response on a cellular level. Testing included evaluation by the surgeons performing the implantations, measurement of the distance between the band and the globe, determination of fibrous capsule thickness and amount of collagen deposition, and enumeration of macrophages accumulated at the band/capsule interface. Based on the results of these studies, two of the porous materials (expanded polytetrafluoroethylene and porous polyurethane fabric) and two of the composite materials (porous polyurethane fabric coated with polyacrylonitrile and silicone with microvilli cut into the posterior surface) were selected for further study.