Trial of new intraocular lens power calculation following phototherapeutic keratectomy]

Thirty-one men (age range, 46-76 years; mean age, 64.8 years) with intrathoracic masses suggesting possible malignancy on the basis of chest radiography or CT underwent preoperative Tc-99m MIBI SPECT examinations. Diagnosis was confirmed on pathologic examinations of samples obtained either at thoracotomy, esophagectomy, or by biopsy. Twenty-five patients had primary lung cancer, including squamous cell carcinoma, large cell carcinoma, adenocarcinoma, and small cell carcinoma. Two patients had lymphomas with spread to the mediastinum, and three patients had extrathoracic primary cancers (one squamous cell carcinoma of esophagus, one squamous cell carcinoma originating from a head and neck tumor, and one metastatic mediastinal leiomyosarcoma). One patient with a tuberculoma had negative results of the Tc-99m MIBI examination. Tc-99m MIBI had a 86.7% sensitivity rate, a 0% false-positive rate, and a 100% positive predictive value to detect malignant intrathoracic masses. There was a 13% false-negative rate, however, suggesting that MIBI-SPECT may underdiagnose malignant lesions. SPECT findings of these 31 patients can be classified as 1) mass with increased uptake, n = 23; 2) ring-like appearance of increased uptake, n = 3; 3) mass with absent uptake, n = 4; and 4) photon-deficient mass, n = 1. Absent uptake in patients with mass lesions could be explained by necrosis of the lesion (caseation necrosis or massive tumor necrosis with or without bleeding). Most malignant intrathoracic masses are Tc-99m MIBI avid and may be detected with a high degree of sensitivity and with an excellent positive predictive value. A positive MIBI scan may help in the clinical diagnosis of malignancy. The use of Tc-99m MIBI could serve not only as a tumor imaging agent, but also may be used to determine the extent of spread and potentially the chemotherapeutic responsiveness of a tumor.     

Clear lens extraction to correct high myopia

PURPOSE: To assess the refractive outcome and postoperative complications in a single surgeon series of clear lens extraction for high myopia. SETTING: Ophthalmology Department, Cornea and Refractive Surgery Unit, Vall d'Hebrón Hospital, Autónoma University of Barcelona, Spain. METHODS: Forty-six clear lens extraction procedures performed in 37 patients from November 1992 to January 1994 by one surgeon were retrospectively analyzed. Capsule tear and vitreous loss, endothelial cell loss, preoperative and postoperative best corrected visual acuity and cycloplegic refraction, and retinal detachment occurrence were looked at. RESULTS: Capsule tear with vitreous loss occurred in one eye (2.17%). Mean endothelial cell loss was 2.6% during the first postoperative year. Best corrected visual acuity was 6/12 or better in 69.4% of eyes preoperatively and in 88.5% postoperatively. Mean cycloplegic refraction was -16.05 diopters (D) preoperatively; the residual cycloplegic refraction was within 1.00 D in 48.4% of eyes and within 2.00 D in 92.5% postoperatively. CONCLUSION: Because of its high predictability, stability, and low morbidity, we believe clear lens extraction is a reasonable refractive surgery option for middle-aged patients with myopia.     

Clear lensectomy and implantation of a low-power posterior chamber intraocular lens for correction of high myopia: a four-year follow-up

PURPOSE: To evaluate the 4-year postoperative outcomes of patients who are highly myopic who underwent clear lensectomy via phacoemulsification and low power posterior chamber intraocular lens implantation. METHODS: The authors performed surgery in 52 eyes of 30 patients in which prophylactic retinal treatment, clear lensectomy, and posterior chamber intraocular lens implantation were used to treat high myopia of 12 diopters (D) or greater. A total of 49 eyes of 28 patients were evaluated at the 4-year postoperative timeframe. Visual acuity, complications, and refractive stability were assessed. RESULTS: The incidence of retinal detachment through 4 years was 1.9%. No new macular complications were observed. Two patients had posterior vitreous detachment without clinical impact between 1 and 4 years after surgery. The incidence of neodymium:YAG (Nd:YAG) capsulotomy was 36.7%. The mean postoperative spherical equivalent was -0.92 D. Four patients had a myopic shift of 0.50 D to 1.00 D from the 1- to 4-year timeframe. Corrected visual acuity of 20/40 or better was achieved in 82% of eyes that had undergone Nd:YAG capsulotomy versus 56% of untreated eyes. Uncorrected visual acuity of 20/100 or better was achieved in 82% of eyes treated with the Nd:YAG laser versus 62% of untreated eyes. CONCLUSION: Visual acuity and refractive outcomes with clear lensectomy are favorable. Retinal detachment remains the major concern of this procedure. Continuous follow-up of these patients is necessary.     

Surgical correction of high myopia in phakic eyes with Worst-Fechner myopia intraocular lenses

BACKGROUND: Implanting an anterior chamber intraocular lens in a phakic eye is an effective surgical procedure for the correction of high myopia. However, the potential risks on the anterior segment structures are not well-known. We conducted a prospective study to evaluate the effectiveness, predictability, and safety after Worst-Fechner lenses were implanted to correct high myopia. METHODS: We studied 32 eyes with preoperative myopia from -9.50 to -27.00 diopters (D) (-16.60 +/- 6.29 D). All 32 eyes were studied by clinical specular microscopy, and the endothelium was analyzed for cell density. Twenty eyes were additionally examined by fluorophotometry for lens transmittance changes. Thirty eyes were additionally examined using the flare mode of a laser flare cell photometer for anterior chamber inflammation; the patients were divided into three subgroups of ten eyes each according to when the postoperative flare measurements were done: 12 months, 18 months, and 24 months. Thirteen phakic eyes with myopia greater than -6.00 D were used as a control group for the flare study. The mean follow-up was 18.3 +/- 8 months (range 6 to 24 mo). RESULTS: Fifty-seven per cent of eyes (16 of 28) had an uncorrected visual acuity of 20/40 or better 12 months after surgery, and 58% (10 of 17 eyes) at 24 months. Spectacle-corrected visual acuity improved: 0.15 at 12 months and 0.16 at 24 months (0.1 = one line) from preoperative values. Visual acuity was stable after 3 months. Eighty per cent of eyes (25 of 31) at 6 months, 75% (21 of 28) at 12 months, and 76.5% (13 of 17) at 24 months had been correctly planned to within +/-1.00 D of emmetropia. The refractive results were stable 3 months after surgery. The mean endothelial cell loss was 7.2% at 3 months, 10.6% at 6 months, 13% at 12 months, and 17.6% at 24 months after surgery. The mean lens transmittance loss was 0.62% at 3 months, 0.72% at 6 months, 0.82% at 12 months, and 1.03% at 18 months after surgery. Flare values were significantly higher for eyes implanted with Worst-Fechner lenses than were those of the control group in all periods under consideration (Mann-Whitney test, p < 0.05). A decentration greater than 0.5 mm was present in 43% of eyes (14 of 32), and halos in 56% (18 of 32). In three eyes (9.3%), fixation of the lens to the iris was not stable. CONCLUSIONS: Our results for the Worst-Fechner myopia lens confirm earlier findings on the effectiveness of the refractive results. However, our study showed a continual decrease in endothelial cell density, a decrease in lens transmittance, and a chronic subclinical inflammation after the implantation of these lenses. Moreover, decentration was common, and the fixation of the IOL to the iris was not stable in some eyes.     

Calculating intraocular lens power in eyes with keratoconus using videokeratography

A patient with keratoconus had cataract extraction and intraocular lens (IOL) implantation in both eyes. The IOL power was determined using keratometric values (K-values) measured by standard keratometry in the right eye and videokeratography in the left eye. The ideal IOL power and the K-value that would have led to the ideal IOL power were determined from the postoperative refraction at 6 weeks. The ideal K-value was compared with the K-values derived from videokeratography and standard keratometry. Refraction at 6 weeks postoperatively was 5.60 and 1.00 diopter more myopic than the aim in the right and left eye, respectively. The mean power in ring 3 in videokeratography of the left eye was the same as the ideal K-value calculated using the Holladay formula. Determining IOL powers with videokeratography-derived K-values might be more accurate than standard keratometry in patients with keratoconus.     

Pitfalls in the determination of intraocular lens power without ultrasound

The rule is simple: An 18 diopter intraocular lens tends to restore the basic refraction. For each diopter of basic refraction to be corrected add or subtract 1.25 diopters. To determine the basic refraction a careful history and an examination of old glasses and past refraction records is necessary. When the basic refraction cannot be ascertained, capital errors may occur. Given the basic refraction, errors or several diopters are still apt to occur. Calculation of intraocular lens power based on K-readings and ultrasonic measurements is therefore always advisable and a must when there is doubt about the basic refraction.     

Clear lens extraction and implantation of negative-power posterior chamber intraocular lenses to correct extreme myopia

PURPOSE: To evaluate the effectiveness, predictability, and safety of clear lens extraction to correct extreme myopia. SETTING: Clinica de Nuestra Se?ora de la Concepción, Fundación Jiménez Díaz, Madrid, Spain. METHODS: This retrospective study comprised 26 eyes of 17 highly myopic patients who had clear lens extraction and implantation of a negative-power posterior chamber intraocular lens (IOL). The IOL power was calculated using the SRK/T formula. Analyzed were visual and refractive results and intraoperative and postoperative complications. Follow-up was at least 12 months in all cases. RESULTS: Uncorrected visual acuity improved in all cases, with 80.77% of eyes achieving 20/100 or better and 42.30%, 20/40 or better. Best spectacle-corrected visual acuity (BSCVA) improved in 23 eyes (88.46%). The percentage of eyes achieving a BSCVA of 20/100 or better increased from 73.07% preoperatively to 92.30% postoperatively and the percentage achieving 20/40 or better, from 23.07 to 73.07%. Of the 26 eyes, 76.91% were within 1.00 diopter (D) of refractive error and 96.16% were within 2.00 D. No intraoperative complications occurred. Although postoperatively 3 eyes (11.53%) developed choroidal detachment and 5 (19.23%) had an intraocular pressure greater than 25 mm Hg, all had a favorable outcome. Four eyes (15.38%) developed posterior capsule opacification and had a neodymium:YAG laser posterior capsulotomy 6 months postoperatively. No retinal detachments were observed. CONCLUSION: Clear lens extraction with negative-power IOL implantation using the SRK/T formula had good effectiveness, acceptable predictability, and a low morbidity in eyes with extreme myopia over a short follow-up. A longer follow-up with more cases is needed to assess the safety of the procedure.     

Secondary intraocular lens implantation

Mere aphakia is not an indication for secondary intraocular lens implantation. However, many patients with positive indications may be benefited most strikingly by this procedure. These indications are illustrated and results of the author's first 65 secondary implantations are analyzed.     

B-mode-guided vector-A-mode versus A-mode biometry to determine axial length and intraocular lens power

Studies of nicotine replacement by 2 mg nicotine polacrilex gum (NG) have typically found that one half to one third of plasma nicotine in recent smokers is replaced. This 5-year study sought to find the extent of nicotine replacement among ex-smokers in the longer term and to identify a mechanism for this relationship. The sample was the special intervention group (N = 3923) in the Lung Health Study, a controlled clinical trial involving smoking cessation. The extent of nicotine replacement was assessed by levels of salivary cotinine. Cotinine levels of ex-smokers using NG after 1 year (219 +/- 149 ng/ml) were similar to those in continuing smokers (290 +/- 159 ng/ml). After 5 years, cotinine levels were the same for NG-using ex-smokers (316 +/- 276 ng/ml), NG-using smokers (309 +/- 240 ng/ml), and NG-non-using smokers (311 +/- 198 ng/ml). Salivary cotinine among NG users at 1 year was only weakly correlated with baseline cotinine levels prior to smoking cessation. Although NG users appear to re-establish cotinine levels characteristic of their smoking, the mechanism by which this occurs remains unclear.     

Double zone PRK for high myopia

INTRODUCTION: Although excimer laser PRK is our operation of choice for treating myopia, the correction of myopia exceeding -8.00 dpt is still a challenge as this procedure requires a deeper keratectomy. Therefore a double zone treatment may be beneficial to reduce ablation depth. METHODS: Twenty-one eyes with myopia between -8.00 dpt and -14.00 dpt were included in this study. Twelve eyes were treated 60% of myopia by 5 mm zone and the remaining 40% in a 4 mm zone in the same session (Group 1). RESULTS: Nine eyes achieved 60% of the desired correction treated with a 4 mm zone whereas 40% correction was achieved in a 5 mm zone (Group 2). No significant difference in postoperative healing, pain, hyperopic shift, myopic regression and haze was observed at the end of the mean follow-up time (10.4 months) but photophobic complaints were less in Group 2. Best corrected visual acuity did not decrease significantly. CONCLUSIONS: Double zone treatment seems to be an interesting method for treating moderate to high myopia.     

Endothelial physiology and intraocular lens implantation

The endothelium is the cellular monolayer which lines the posterior surface of the cornea. This layer is important in clinical ophthalmology because it is vital to maintenance of the transparency of the cornea and vision through its pump and barrier functions which limit the ingress of fluid into the cornea from the aqueous. When the function of the corneal endothelium becomes compromised, the corneal stroma swells as it hydrates. Subsequently, epithelial bullae form with painful recurring epithelial erosions, and finally corneal scarring and blindness result. The relatively vulnerable position of the corneal endothelium renders it susceptible to iatrogenic injury during intraocular procedures, especially IOL implantation: the poor regenerative (mitotic) capacity of the human corneal endothelium limits its ability to recover normal function once it is injured.     

Endothelial damage from intraocular lens insertion

Previous studies have shown that approximately 40 per cent of the corneal endothelial cells can be lost at the time of intraocular lens insertion. Momentary contact between the methacrylate surface and the endothelial cells causes an adhesion between these surfaces and results in extensive cell damage upon separation of the surfaces. This type of damage appears to be due to a biophysical interaction between these surfaces and may be avoidable by altering the surface of the lens.     

Microlamellar keratectomy for correction of high myopia

We reviewed the records of 243 patients treated at 271 disc levels to determine the incidence of side effects and complications of percutaneous nucleotomy. In our early experience there were 7 technical failures (2.5% of all attempts), of which 6 were at the 5th disc level. The success rate dropped from 67% at 3 months to 60% 1 year after treatment due to recurrences in 16 patients (6.6%). Extruded or sequestered fragments were found in 6 patients (2.4%), and may have been caused by nucleotomy. However, only one was accompanied by aggravation of symptoms. Discitis was seen in 2 patients (0.8%), both treated at two separate disc levels. About half the patients experienced increased low back pain, mean duration 9 days, after treatment, and 3 (1.2%), of whom 2 also had nonorganic disorders, needed admission to hospital because of severe pain. Mild spasm and a sensation of instability were noted by 9.6% and 25% of the patients respectively. Injury to nerves, bowels, vessels or ureters or a dural leak never occurred. The study confirms earlier reports that the rate of serious complications is low.     

Secondary intraocular lens implantation in children

OBJECTIVE: The study was designed to determine the visual outcome and indication of secondary posterior chamber intraocular lens (IOL) implantation. METHODS: The operation was performed on 34 eyes with aphakia in children after separation of posterior iris synechia from posterior capsule and formation of a posterior chamber space large enough to insert an intraocular lens. Based on whether the integrity of the posterior capsule was complete or not, various techniques of secondary IOL implantation were adopted. RESULTS: The follow-up periods ranged from 6 to 24 months. The results showed that 29 of the eyes (85.29%) achieved a post-operative corrected visual acuity equal to or better than that of the best corrected visual acuity before the surgery; the postoperative uncorrected visual acuities in 16 eyes (47.06%) and corrected visual acuities in 28 eyes (82.35%) reached 0.5 or better. CONCLUSION: Secondary posterior chamber IOL implantation is a safe and effective method in children who have a complete or partial posterior capsule.     

Reduced intraocular pressure after phacoemulsification and posterior chamber intraocular lens implantation

PURPOSE: To ascertain whether phacoemulsification with posterior chamber intraocular lens (IOL) implantation causes long-term reduction in intraocular pressure (IOP). SETTING: Private practice, Kempten, Germany. METHODS: Intraocular pressure was measured in both eyes of 120 consecutive patients who were unilaterally phakic after phacoemulsification a mean of 17 months +/- 17 (SD) previously. Mean age of the 36 men and 84 women was 76 +/- 10 years. Data were analyzed using binomial distribution and the Wilcoxon signed-rank test. RESULTS: The median ratio of IOP in the pseudophakic eye to IOP in the phakic eye was 0.83. The IOP was lower in the pseudophakic eye in 96 patients (80%). The median IOP was 12 mm Hg in the pseudophakic eyes and 14 mm Hg in the phakic eyes (P < .001). As measured by the interquartile range, IOP distribution was more centered in the pseudophakic than in the phakic eyes (3 versus 4). The IOP in the pseudophakic eyes remained lower to the last measurement, 5 years postoperatively, and appeared to be independent of patient age. Lower IOP in the pseudophakic eye was consistently present in patients with higher IOP in the phakic eye (16 to 22 mm Hg). CONCLUSION: Phacoemulsification with posterior chamber IOL implantation reduced IOP in most but not all patients with a preoperative IOP of 22 mm Hg or less. This reduction was maintained over several years, with the cause yet to be established. Lower IOP may decrease the risk of subsequent glaucomatous nerve damage in these patients.     

Explantation of a foldable silicone intraocular lens

PURPOSE: We used a novel technique for explanting an improperly oriented silicone intraocular lens. METHODS: The elastomeric property of silicone was used to deform the optic and remove the intraocular lens in one piece. RESULTS: We explanted a flexible intraocular lens without compromising the integrity of the original wound, posterior lens capsule, or corneal endothelium. CONCLUSIONS: The technique offers a superior means of intraocular lens explantation while retaining the benefits of small-incision cataract surgery.