Correction of myopia and astigmatism using laser in situ keratomileusis

Patients and methods: In order to better define the potential advantages and risks of laser in situ keratomileusis (LASIK), we designed a prospective study including 73 eyes. Results: After 6 months, 62 eyes were examined. Myopia was corrected from –6.10 ± 3.12 (mean ± standard deviation) to + 0.04 ± 0.66 D, with 54 eyes (87.1 %) being within ± 1.00 D of emmetropia. Astigmatism was corrected from –1.07 ± 1.02 to –0.32 ± 0.89 D. Uncorrected visual acuity was 0.5 or better in 59 eyes (95.2 %) and 1.0 or better in 27 eyes (43.5 %) 6 months postoperatively. More than one line in best-corrected visual acuity was lost by 6 eyes (9.7 %), with most of these eyes being highly myopic. There was no change or a gain in lines in best corrected visual acuity in 42 eyes (66.1 %). Intraoperative complications arose in two eyes (2.7 %); in one eye, visual acuity was temporarily decreased. More treatments were performed in 7 eyes (9.6 %). Postoperatively, no haze, scars or central islands were detected. Patient satisfaction after LASIK was high: 97.3 % were pleased or very pleased with the result. Conclusions: In conclusion, LASIK is effective in the correction of myopia and myopic astigmatism. Although complications more frequently occurred in the correction of higher refractive errors, LASIK seems to be relatively safe compared with other refractive methods.      

Laser in situ keratomileusis (LASIK) in myopia: 2-year results

Background: Long-term results on LASIK are not available to date. We therefore evaluated the predictability, stability and complication rate after LASIK in moderate – to-high myopia. Patients and methods: We treated 70 eyes (41 patients) using the Automatic Corneal Shaper and the Keracor 116 excimer laser. Patients were followed for 1, 6, 12 and 24 months. Spectacle refraction, visual acuity, rate of retreatment, and patient satisfaction were evaluated. Results: At 24 months the results were as follows: Myopia −5 to −9.9 D (n =18): 94 % within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 6 % (6 %); uncorrected acuity 20/40 or better in 83 %; no loss of 2 ore more lines of visual acuity; 89 % highly satisfied. Myopia −10 to −14.9 D (n = 12): 88 % within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 20 % (0 %) ; uncorrected acuity 20/40 or better in 72 %; 4 % lost 2 or more lines of visual acuity; 96 % highly satisfied. Myopia −15 to −29 D (n = 22): 33 % within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 41 % (18 %); uncorrected acuity 20/40 or better in 7 %; no loss of 2 or more lines of visual acuity; 67 % highly satisfied. Conclusion: LASIK is an accurate, effective and stable procedure for correcting myopia of −5 to −10 D. Results are less precise in myopia up to −15 D, and some visual loss occurs in a number of patients. In myopia > −15 D, results are not satisfactory because of poor accuracy and low stability.      

Correction of myopic astigmatism by combined treatment with PRK and T-incision and photoastigmatic refractive keratectomy

Background: In contrast to the correction of simple myopia there is no widely accepted technique for the correction of myopic astigmatism. Currently two techniques are available: the photoastigmatic refractive keratectomy (PARK) and the combination of arcuate keratotomies with standard PRK (PRK-T). Methods: In two groups, 67 patients underwent a correction of myopic astigmatism in a total of 87 eyes (19 by PRK-T and 68 by PARK), and were followed for 1 year. The spherical equivalent was − 6.7 D in both groups and the refractive astigmatism ranged from − 1.0 to − 6.5 D. The PARK procedure was performed by means of an elliptic ablation (Kertom I, Schwind) with a 5.8 × 8.1 mm zone. The PRK-T technique consisted of two arcuate keratotomies with a free optical zone of 7 mm and a standard myopic PRK at least 6 weeks later. Results: The 1 year follow-up was completed in 57 out of 87 eyes included in the study. At 1 year post-operation, 83 % of the PRK-T group and 80 % of the PARK group had an uncorrected visual acuity of 20/40 or better. The refractive astigmatism was reduced by 76 % in the PRK-T group and by 67 % in the PARK group. The spherical equivalent was − 0.59 ± 1.1 D at 1 year after PRK-T and − 0.28 ± 1.04 D after PARK. In three eyes of the PARK group (6.7 %) a visual loss of more than one Snellen line occured. Two of these eyes had a preoperative myopia of more than − 6 diopters. Conclusion: Both techniques have the potential to reduce myopic astigmatism, however, the success rate is not as high compared to spherical PRK. Also, the complication rate of 2.5 % in corrections to − 6 D is significantly higher than that with spherical myopic PRK.      

Intraoperative and postoperative complications after laser in situ keratomileusis (LASIK)

Purpose: To quantify the incidence and type of complications after LASIK for the correction of myopia with special consideration to the time lapse after surgery and the possible consequences regarding high-contrast sensitivity and other modalities of visual acuity. Material and methods: Between January 1995 and April 1997, 125 eyes of 88 patients with myopia greater than −6.0 D who could not wear contact lenses were operated on at our institute. In this prospective study the patients were examined consecutively preoperatively as well as postoperatively at day 4 and months 1, 3 and 6. The complications were divided into three groups (intraoperative, early postoperative and late postoperative). Results: Our complication rate was 7.2 % (loss of 2 lines of visual acuity) – with cutting artifacts related to the microkeratome, wrinkling of the flap and epthelial ingrowth. Conclusions: LASIK is a microsurgical procedure that requires adequate experience and the desire by the surgeon for self-evaluation. In spite of the good clinical results in the correction of high myopia the complication rates seems still to be too high. This should be the objective for further improvement primarily related to the microkeratomes.      

Deep lamellar keratoplasty with the guided trephine system for transplanting fullthickness donor tissue

Background: Despite the fact that deep lamellar keratoplasty (DLKP) is less invasive than to penetrating keratoplasty (PKP), this procedure is rarely performed. We therefore investigated whether or not the DLKP technique we employed can achieve stable improvement of visual acuity. Materials and methods: Thirty-three eyes underwent TLKP for treatment of superficial corneal pathology. The donor tissue transplanted was suitable for PKP. The donor lenticule was obtained on the artificial chamber of the guided trephine system (GTS). The recipient cornea was trephined with the same trephine to a depth of 680 μm. Manual dissection was performed with a bevel-up blade. The donor lenticule with the endothelium peeled off was then sutured in with a 10 × 0 nylon double-running antitorque suture. Cortisone-antibiotic eye drops were administered postoperatively. Results: Throughout the series no complications occurred. The mean best corrected visual acuity (BSCVA) over glasses was 0.29 ( ± 0.21) preoperatively, 0.1 ( ± 0.11) at 1 week, 0.33 ( ± 0.14) at 1 month, 0.5 ( ± 0.13) at 6 months, 0.61 ( ± 0.16) at 1 year and 0.63 ( ± 0.15) at 2 years. Clinically, we observed two subpopulations. In the first group of 87 % of the cases, mean BSCVA was 0.67 ( ± 0.07) at 6 months. The remaining cases (BSCVA ≤ 0.25 at 6 months) achieved a mean BSCVA of only 0.2 ( ± 0.04) at 1 year. Mean corneal astigmatism measured 2.93 D ( ± 1.62) preoperatively, 2.69 D ( ± 1.18) at 1 month, 2.09 D ( ± 1.07) at 1 year, and 2.22 D ( ± 1.11) at 2 years. We did not observe any graft rejection. Conclusion: The technique reported for DLKP provides excellent matching of donor lenticule and recipient bed. Separation of donor and recipient stroma prevents interface healing. DLKP appears to be a safe procedure for the surgical treatment of superficial corneal pathology and may offer a clinically applicable alternative to PKP.      

A prospective study investigating the long-term stability of changes in astigmatism following arcuate lamellar keratotomy (ALK): 3-year results

Introduction: The correction of low to moderate astigmatism is possible today by means of photoablation (PRK), while the treatment of moderate and higher astigmatism still involves refractive keratotomy. Experience has shown that cataract surgery, using modern tunnel techniques with self-healing incisions, results in earlier stability in both the refractive outcome and wound healing. In this study, we attempted to combine the advantages of lamellar keratotomy with those of a pair-wise T-incision as arcuate lamellar keratotomy (ALK). Patients and methods: The clinical outcome of 41 patients who underwent ALK was investigate in a prospective study over a period of 3 years. The pre- and postoperative investigations undertaken included the measurement of astigmatism using a Zeiss keratometer, uncorrected visual acuity, and corrected glare vision using a Humphrey autorefractor. All patients had astigmatism between 2.0 and 7.0 D. Together with a uniform arcuate incision, we used 7 mm (n = 26) and 8 mm (n = 15) mm zones for correction. Results: The average preoperative astigmatism was 4.01 ± 1.90 (median, 3.50) D. After a 3-year follow-up the average postoperative astigmatism was 1.59 ± 1.29 (median, 1.38) D. The astigmatic change induced (Jaffé) after 3 years was about 3.23 ± 2.23 (median, 3.16) D. The average uncorrected visual acuity (log MAR) before ALK was 0.20 ± 0.12 (median, 0.22) and after follow-up, 0.41 ± 0.14 (median, 0.39). Corrected glare vision before surgery was 0.23 ± 0.19 (median, 0.10) and afterwards, 0.25 ± 0.22 (median, 0.14). Conclusions: Arcuate lamellar keratomy (ALK) stood the test as a routine clinical procedure for correction of moderate astigmatism with stable postoperative functional outcomes. We did not find impairment of glare vision following this procedure.      

A prospective comparison of two multifocal lens models

Summary Background: The functional results of two different types of multifocal intraocular lenses (based on the diffractive and refractive principle, respectively) were investigated prospectively. Materials and methods: Altogether 50 patients who had a multifocal lens implanted were examined 4–6 weeks postoperatively. Visual acuity for distance and near vision, contrast sensivity, low contrast visual acuity and glare visual acuity were investigated. Results: Distance visual acuity, contrast sensitivity, low contrast visual acuity and glare visual acuity did not show significantly different results. Near visual acuity was statistically significantly better with the diffractive type of multifocal lens (because of a stronger adjustment for near vision). When the focus depth was tested by defocus curves, both lenses had better results within different areas of defocus. Conclusions: All patients in both groups showed satisfactory results. When choosing a multifocal intraocular lens, the individual needs of each patient should be taken into consideration.      

Laser of complications in in situ keratomileusis (LASIK)

Background: The incidence and course of intraoperative and postoperative complications of LASIK were investigated. Patients and methods: We consecutively treated 598 eyes (316 patients) using the Automatic Corneal Shaper and the Keracor 117 C excimer laser. One hundred and sixty-three eyes were also available at 12 months. The preoperative spherical equivalent was − 5.31 ± 5.49 D (+ 9 to − 23 D). We evaluated intra- and postoperative complications. Results: Intraoperative complications of keratotomy were observed in 1.3 % (irregular cut, n = 5; free cap, n = 2; incomplete cap, n = 1), and other intraoperative complications in 1.7 % (epithelial defects, n = 7; flap dislocation, n = 1; lateral kanthotomy required, n = 2). None of these complications caused any long-term effects or loss of two or more lines of visual acuity. Postoperative complications were observed in 0.9 % (peripheral epithelial ingrowth, n = 4; keratectasia, n = 1; subretinal neovascularisation, n = 1). Conclusions: The rate of complications in LASIK is low, and intraoperative complications did not cause any significant loss of vision. We observed keratectasia in one eye, which suggests that deep ablations should be avoided, which limits the amount of correction possible.      

Phototherapeutic keratectomy (PTK) – a successful treatment for Thiel-Behnke dystrophy and its recurrences

Summary In recent years good results after treatment of different superficial corneal pathologies with the excimer laser 193 nm have been reported. Thiel-Behnke dystrophy is a hereditary form of anterior stromal dystrophy, a promising layer for successful phototherapeutic keratectomy (PTK). This type of dystrophy was first described in 1967 in Kiel. Patients and methods: Ten members of the original family of 1967 were re-examined at the University Eye Hospital, Kiel. A phototherapeutic keratectomy was performed in six eyes because of the typical honeycomb corneal surface irregularity and superficial haze. Two of these eyes had a recurrence of the primary disease on the graft. Four eyes had been untreated so far. The best spectacle corrected visual acuity preoperatively was between 20/200 and 20/40. For all treatments the MEL 60 excimer laser (Aesculap Meditec) was used. To even out the peaks and valleys of the irregular surfaces, modulating agents were applied in decreasing concentrations. The follow-up period is now between 8 months and 4 years. Results: All eyes showed significant visual improvement postoperatively with a best spectacle corrected visual acuity of 20/32 and higher. In one of the postkeratoplasty eyes with the longest follow-up after PTK, the original disease has begun to recur. Conclusions: Phototherapeutic keratectomy is a successful therapy for Thiel-Behnke dystrophy; it results in quick recovery of patients and their vision. Stable visual acuity and corneal transparency have been observed that last for years. Recurrences after penetrating keratoplasty or after PTK can be positively retreated. A (re-) keratoplasty may be postponed or avoided.      

Cataract surgery at the Virchow Clinic in Berlin. Review of the last 16 years

Purpose: The aim was to compare the different techniques of cataract surgery regarding early postoperative astigmatism and visual acuity. Patients and methods: The data of three groups of patients (100 eyes) were analyzed retrospectively (1980–1982; 1987–1990; 1991–1993). Three different techniques of cataract surgery were used. Included in the prospective study were the data for 285 eyes, which underwent phacoemulsification, self-sealing incision and controlled induction of astigmatism. Results: In the time period retrospectively investigated, we found that because of the advancements in operation methods, there was a reduction in the amount of surgically induced astigmatism. From 1980 to 1995 there was a clear increase in the number of patients with early low-grade postoperative astigmatism < 1 D (1980–1982: 6 %, 1987–1990: 19 %, 1991–1993: 64 %, 1994–1995: 84 %). There was an improvement in postoperative vision (with correction > 0.5) of 16 % in 1980–1982 to 45 % from 1987 to 1990, 58 % from 1991 to 1993, and to 76 % in 1994–1995. Conclusions: Surgically induced astigmatism, which was considered to be a sign of unwanted increased postoperative astigmatism, was reduced from 1980 to 1993. Through controlled induction of astigmatism it was possible to compensate for preoperative astigmatism in the prospective group. Improved surgical techniques led to improvements in early postoperative visual acuity.      

Classification of corneal topography after penetrating keratoplasty

Background: Semiquantitative classification of corneal topography after penetrating keratoplasty has the potential for focusing information about the areal dioptric power of the cornea. The purpose of this study was to objectify the procedure of manual semiquantitative classification using a Fourier transform of corneal topography power data and to correlate both methods. Patients and methods: Fifty patients each (30 keratoconus, 20 Fuchs dystrophy) underwent nonmechanical trephination (excimer laser MEL60, Aesculap-Meditec, Jena) in penetrating keratoplasty. All procedures (7.5-mm trephination diameter in Fuchs, 8.0 mm in keratoconus, double-running 10–0 nylon suture) were done by one surgeon. Pre-, intra- and postoperative treatment were identical. At the follow-up examinations, the keratometric astigmatism, qualitative and quantitative criteria of the automatic videokeratography, visual acuity and refraction were assessed. Corneal topography was classified both manually and based on Fourier coefficients. Results: After a mean follow-up of 24 ± 5 months, keratometric net astigmatism was 3.0 and 2.7 D with keratoconus and Fuchs dystrophy. Corneal topography analysis showed a higher orthogonality of the bow-tie shape and less asymmetry between opposite hemimeridians with increasing follow-up after keratoplasty. The semiquantitative classification showed a statistically significant correlation with the classification based on Fourier coefficients, especially with higher astigmatism and after suture removal (P = 0.04/0.01 before/after suture removal). Discussion: After nonmechanical trephination, the semiquantitative classification of corneal topography can be synthetized using Fourier analysis of corneal dioptric power data. In the future, this method may be favored for prediction of potential best-corrected visual acuity after penetrating keratoplasty.      

Clinical use of reversal of mydriasis by dapiprazole

Background: Dapiprazole hydrochloride is an alpha-1-adrenergic inhibitor that anticipates the mydriatic effect of phenylephrine in dilator muscle receptors in a competitive way. The aim of this study was to determine for which indications for mydriasis pupil dilation by phenylephrine alone is sufficient and if the reversal by dapiprazole is convenient and the practical. Material and method: In 286 eyes of 147 outpatients, the pupil was dilated for fluorescein angiography – FLA (100 eyes of 50 patients), examination of the fundus – Fd (99 eyes of 52 patients), central argon laser coagulation – cALC (64 eyes of 32 patients), peripheral argon laser coagulation – pALC (16 eyes of 9 patients) and Nd:YAG capsulotomy (7 eyes of 4 patients) with phenylephrine 10 % eye drops, followed by reversal by dapiprazole 0.5 %. The width and mobility of the pupil were tested at intervals of 10 min. When mydriasis by phenylephrine was insufficient, tropicamide was applied additionally. Results: In 98 % of FLA with scanning laser ophthalmoscope, 75 % of cALC, 76 % of Fd, 62 % FLA with fundus camera and 38 % of pALC, mydriasis could be reached that was sufficient for the indication. Diabetics showed significantly more sluggish pupil mobility (t1/2: P < 0.05 mydriasis, P < 0.005 reversal). The mean duration after using dapiprazole until reaching the starting value ( ± 1 mm) of the pupil was 44.3 ± 26.3 min. In 86 % of the examined eyes, the pupil reached its starting value within 1 h. The subjective degree of satisfaction with the application of dapiprazole was “satisfied” to “very satisfied” (5.4 ± 1.4 points on a scale from 1 to 7 points). Discussion and conclusion: In fundus examination, fluorescein angiography by a laser scanner, diagnostic retinal examination and central laser coagulation, the combination phenylephrine/dapiprazole was most suitable. In our opinion, the combination is less suitable for peripheral argon laser coagulation and fluorescein angiography using a fundus camera.      

Comparative laser flare measurement and fluorophotometry in anterior and posterior uveitis

Summary Recent studies have sought to quantify aqueous flare by laser flare measurement. An increase in aqueous flare caused by a rise of protein concentration was frequently found both in anterior and posterior segment disease. This has been interpreted as a breakdown of the blood – aqueous barrier (BAB). By measuring the diffusion coefficient of the BAB compared to the aqueous flare value in patients with anterior and posterior uveitis, the extent to which the increase in flare value was related to a possible break down of the BAB was examined. Patients: Thirty-nine normal eyes (23–78 years; 41.6 ± 18.6), 18 eyes with anterior uveitis (iritis, iridocyclitis; 18–57 years; 35.2 ± 12.4) and 29 eyes with posterior uveitis (chorioretinitis or retinochorioiditis; 18–51 years; 31.7 ± 10.5). The diffusion coefficient P(a) of the BAB was measured fluorophotometrically, while the flare value was quantified by laser flare measurement. Results: Flare values (1/ms) were found to be significantly increased (p < 0.001) compared to normal eyes (4.6 ± 1.7) both in anterior uveitis (20.9 ± 8.5) and in posterior uveitis (17.4 ± 8.3) but did not significantly differ between them (p = 0.43). The diffusion coefficient P(a) (10^–3/min) of the BAB was not significantly different (p > 0.05) between normal eyes (0.5 ± 0.2) and eyes with posterior uveitis (0.9 ± 0.7), whereas it was significantly increased (p < 0.001) in anterior uveitis (6.5 ± 5.4) compared to the other groups. Conclusions: (1) In posterior uveitis, an increased flare value is not necessarily correlated with a breakdown of the BAB; proteins may enter the aqueous from posterior. (2) Assessing the function of the BAB in posterior segment disease using laser measurement should be carried out with caution; if possible, permeability measurements of the BAB should be undertaken seperately.      

Ability to drive after surgery for retinal detachment

Background: After vitreoretinal surgery the patient is at least temporarily unable to drive. Buckling procedures may cause refractive changes, reduced motility or impaired binocular vision. We examined the ability of these patients to drive a car according to German law after retinal surgery. Patients and methods: The frequency and extent of changes interfering with driving ability were examined in 112 unselected patients 3.5 years (2–5 years) after successful buckling procedures. We used half-round buckling elements of 3–11 mm diameter or encircling bands (2–3 mm). We examined visual acuity, frequency of permanent diplopia and field of normal binocular vision. Driving ability was considered as impaired, when visual acuity was below 0.4 in the better eye or 0.2 in the worse eye, or when diplopia occurred within a gazing field of 20 ° of diameter. Results: Eighteen of 112 (16 %) patients reported diplopia within the first 3 months, so they were temporarily unable to drive. Two to five years later 14 of 112 patients did not have sufficient visual acuity according to the German requirements. Another 2 patients had an impaired binocular vision, resulting in driving disability. Conclusion: Driving ability may be temporarily restricted by double vision in 15 % of patients after successful buckling for retinal detachment. Permanent driving ability is mainly impaired by macular involvement in retinal detachment. The type of buckling procedure is of minor importance.      

YAG laser capsulotomy in multifocal intraocular lenses

Introduction: Multifocal intraocular lenses (MIOLs) have been implanted with good results for several years. Because the light is distributed between two or more focuses, there is slight light reduction for every picture. Capsular fibrosis can cause additional reduction of the amount of light to the retina. Patients and methods: A diffractive MIOL 811X from Pharmacia & Upjohn was implanted in 40 eyes of 40 patients. Within 1 year postoperatively, 13 patients underwent YAG Laser capsulotomy between the 4th and the 6th month. Before and after the YAG laser the visual acuity for distance and near vision was tested. In addition, a contrast test (Ginsburg test) was performed. Results: Before YAG laser capsulotomy, the visual acuity for distance without correction was 0.5 (± 0.17) and near vision J 2.4 (± 1.4). After the YAG laser procedure, uncorrected visual acuity improved to 0.65 (± 0.21) for distance and J 1 (± 0) for near vision. With the best distance correction the distance vision was 0.85 (± 0.18) and near vision was J 1.77 (± 0.89) before capsulotomy. After the YAG laser treatment, patients reached with best correction a visual acuity of 1.1 (± 0.24) at distance and J 1 (± 0) at near vision. The contrast equivalent acuity increased from 20/70 before the YAG laser treatment to 20/40 after ward. Discussion: Patients with a MIOL feel early visual discomfort due to capsular fibrosis. In most cases the patients still have good visual acuity, but decreased contrast sensitivity. Early YAG laser capsulotomy increases the visual acuity and the contrast sensitivity significantly.      

Prospective controlled evaluation on radiotherapy of subfoveolar neovascularization

Summary Despite the successful therapy of subretinal neovascular membranes by laserphotocoagulation there are many problems to be overcome. In the case of subfoveolar neovascularization, photocoagulation leads to a sudden decrease in visual acuity.Recently radiotherapy is considered as an alternative. Complications and effectivity were evaluated in this prospective and randomized trial. The initial results are presented. Patients and methods: There are 76 patients (51 women, 25 men, average age 77.7 ± 8.6 years) included in the prospective randomized study. All of them show subfoveolar neovascular membranes in FLA and a decrease in visual acuity between 0.05 and 0.5. They were randomly assigned to either the radiotherapy or the control group. Radiotherapy was done within 6 days by 6 × 2 Gy (6 MV photons). The follow-up was at 4 weeks, after 3 months, after 6 months and then every 6 months after the end of radiotherapy. On average the follow-up is at 15.1 months. Results: Concerning age and visual acuity before therapy, the control group and the radiotherapy group were not significantly different. At 4 weeks after radiotherapy, visual acuity was 0.13 ± 0.46 (LogMAR). After 12 months, visual acuity at a distance was 0.11 ± 0.30 in the therapy group and 0.09 ± 0.13 (P = 0.838) in the control group. Patients with a preoperative visual acuity better than 0.2 improved more after radiotherapy. Metamorphopsy improved in 75 % of the therapy group. The following complications could be observed: In the control group 3 patients suffered subretinal bleeding, in the radiotherapy group 3 patients, respectively. Conclusions: At present, the follow-up is too short to recommend radiotherapy as a standard procedure in the case of subfoveolar neovascularization. The results in patients with a better preoperative visual acuity encourage us to continue this study.      

Bilateral cystoid macular edema following successful treatment of AIDS-associated CMV retinitis

Background: Cystoid macular edema (CME) in AIDS patients with inactive cytomegalovirus (CMV) retinitis is an uncommon but potentially sight-threatening complication. The pathogenesis of CME in these patients is unclear. This study tries to identify possible risk factors by analyzing the charts of five patients. Methods: Ten eyes of 5 patients that finally developed CME were followed for an average of 18 months. The initial retinal lesions, their response to antiviral treatment, the development of CME, and the patients' immune status were prospectively monitored. Results: CMV retinitis was diagnosed at a median CD4+ count of 3 cells/mm³ (range 0–11). All eyes responded to the initial systemic anti-viral treatment. At the onset of CME, CMV retinitis was controlled by antiviral maintenance therapy in all patients [ganciclovir (n = 2), cidofovir (n = 2), foscarnet (n = 1)]. The median time between diagnosis of CMV retinitis and onset of CME was 11.5 months (range 5–24). Development of CME was associated with significant visual loss: acuity ranged from 0.05 to 0.7 when CME was first noticed, compared to 0.8–1.25 at diagnosis of CMV retinitis. Duration of inflammation, size or zone of retinal necrosis did not favor the development of CME, neither did the antiviral therapy. A weak correlation of CME development and immune status (expressed as increase of CD4+ cells) was found. Due to systemic corticosteroids CME resolved. Conclusions: CME is a new visual threat to AIDS-patients with CMV retinitis whose immune status improved under the latest combined antiretroviral therapy. Therapy with oral corticosteroids may positively influence this condition.      

The effects of changed biomechanical parameters on measurements of intraocular pressure in keratoconus patients

Background: Keratoconus is associated with changes in the corneal structure, such as defects of Bowman's layer, a decrease of corneal thickness etc. They result in alterations of some of the biomechanical parameters of the cornea, namely, rigidity and elasticity. The present study was performed to examine how impression tonometry and applanation tonometry for determination of intraocular pressure (IOP) are affected by the changed biomechanical parameters associated with keratoconus. Patients and methods: We examined 20 normal subjects (40 eyes) and 17 keratoconus patients (25 eyes). The corneal thickness was measured by ultrasound pachymetry in the corneal center. In the keratoconus patients, an additional measurement was made at the conus peak. The corneal curvature was determined using the TMS keratoscope. The IOP measurements were made with the Schi?tz tonometer (10 g). For comparison, additional IOP measurements in the corneal center and, in the keratoconus group, on the conus peak were made with the applanation tonometer. Results: The normal subjects had a central corneal thickness of 548 ± 30 μm, compared to 505 ± 42 μm in the corneal center and 425 ± 41 μm on the conus peak in keratoconus patients. The average corneal curvature was 43.3 ± 1.8 D in the normal subjects and 47.8 ± 4.1 D in keratoconus patients. Applanation tonometry produced results on 11.33 ± 1.43 mm Hg in the normal group (corneal center) compared to values of 12.00 ± 2.55 mm Hg (corneal center) and 7.30 ± 1.95 mm Hg (conus peak) in the keratoconus cohort. The coefficient of rigidity was 0.0236 ± 0.0026 μl⁻¹ in the normal subjects, compared to 0.0173 ± 0.0050 μl⁻¹ in the keratoconus patients. Conclusion: The morphological changes associated with keratoconus may cause tonometry errors.      

Reduced visual function causes higher risks of traffic accidents

Background: This study was carried out to investigate the relationship between the frequency of traffic accidents and impaired vision. Materials and methods: Seven hundred and fifty-four drivers involved in accidents were recruited, in addition to 250 accident-free drivers similar in age and driving experience as an control group. The age distribution of the persons involved in traffic accidents (mean 56.3 years) was similar to that of the control group (mean 57.7 years), the difference was not statistically significant. Both groups underwent a complete ophthalmological examination. Results: All three types of accidents (night-time accidents, violations of right of way, accidents during an overtaking manoeuvre) had a statistically significantly higher incidence of reduced photopic visual acuity, mesopic vision and an increased sensitivity to glare. Some other visual functions were also abnormal, with differences according to the type of accident. In particular, there were noticeable differences between the control group and those who were involved in night-time accidents regarding mesopic vision and sensitivity to glare. Concerning mesopic vision, 15 % of the 261 persons involved in night-time accidents did not reach the contrast limit of 1 : 5; with glare, 20.7 % failed. In comparison 4 % of the control group reached this critical limit without glare and 7.6 % with glare. These differences are highly statistically significant. In contrast to these findings, many of the drivers involved in accidents assessed their own visual capability as “excellent”. Conclusions: The results of this study show that reduced mesopic vision and increased sensitivity to glare are accompanied by an increased risk of night-time accidents (for example, collisions with a non-illuminated obstacle). This emphasizes the importance of regular ophthalmological check-ups including visual functions such as mesopic vision and sensitivity to glare, which currently are not required by the traffic laws in Germany.      

Assessment of refractive change following photorefractive keratectomy: keratometry versus computerized videokeratography

Summary The purpose of this study was to determine which corneal curvature values most closely correlated to change in subjective manifest refraction following excimer laser photorefractive keratectomy (PRK). Methods: Excimer laser PRK was performed on ten eyes of ten patients (mean age: 37.3 years). Preoperative refractive errors ranged from –2.25 to –8.75 diopters. Preoperatively and 1 month postoperatively, we determined the spherical equivalent of the manifest refraction (corrected for a 12 mm vertex distance) and measured corneal power using standard keratometry (Bausch and Lomb keratometer) and computerized videokeratography (EyeSys Corneal Analysis System). We collected five corneal values: standard keratometry, videokeratography-derived simulated keratometric readings calculated using the axial, instantaneous and refractive formulas, and corneal refractive power over the central 3-mm zone (effective refractive power); apart from the traditional refractive index of the cornea (n = 1.3375), we used the refractive value of the anterior corneal stroma (n = 1.376). For each of the five corneal values, we subtracted the change in corneal power from the change in manifest refraction and calculated the means and standard deviations. Results: The mean differences between the refraction and the corneal values for a refractive index of 1.3375/1.376 were: 0.89 ± 0.54^*/1.26 ± 0.59* for standard keratometry; 1.64 ± 0.75^*/1.37 ± 0.7*, 4.03 ± 1.86^*/3.86 ± 1.87*, and 1.16 ± 0.76^*/0.91 ± 0.74* for the axial, instantaneous, and refractive videokeratography values, respectively; and 0.83 ± 1.03^*/0.39 ± 1.08 for the effective refractive power (*, p < 0.05). Conclusions: In our series, only the values for the effective refractive power, calculated with the refractive index of the anterior stroma of the cornea, were not statistically different from the change in manifest refraction.