Comparison of keratometric and topographic cylinder and axis measurements on normal corneas with low astigmatism.

PURPOSE: To evaluate agreement in measurements of astigmatic axis power and location between keratometry and computer assisted videokeratography (corneal topography) on normal corneas with less than 1.50 D of idiopathic astigmatism. METHODS: Keratometric readings with the 10 SL/O Zeiss ophthalmometer and corneal topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal corneas. Measurement agreement between the two instruments was evaluated in regard to steep and flat meridian power and location, and in astigmatism magnitude (D). RESULTS: The limits of agreement (d-2 SD to d+2 SD) between the two instruments were found to be broad for clinical purposes in measuring the steep meridian power (-0.16 to -1.20 D), flat meridian power (0.43 to -1.25 D), and astigmatism (0.60 to -1.12 D). A constant bias of the TMS-1 towards the 10 SL/O Zeiss ophthalmometer was found, in measuring steeper both principal meridians and higher amount of astigmatism. Mean location difference was 19 degrees (+/-190) for the steep meridian and 17 degrees (+/-20 degrees) for the flat meridian. CONCLUSIONS: Despite the differences seen in measurements between the 10 SL/O ophthalmometer and the TMS-1, these differences may be clinically small enough for the methods to be used interchangeably in measuring only the magnitude of astigmatism on normal corneas. However, the disagreement in astigmatism axes is too great to be ignored.

Diurnal intraocular pressure reduction with latanoprost 0.005% compared to timolol maleate 0.5% as monotherapy in subjects with exfoliation glaucoma.

AIMS: To compare the diurnal intraocular pressure (IOP) efficacy and safety of timolol vs latanoprost in subjects with exfoliation glaucoma (XFG). METHODS: A 3-month prospective, single-masked, active-controlled, parallel comparison performed in six centres in Greece that randomized subjects in a 1 : 1 ratio to either latanoprost in the evening (2000 hours) and placebo in the morning (0800 hours), or timolol twice daily (0800 and 2000 hours). RESULTS: In all, 103 subjects completed the study. After 3 months of chronic dosing, the latanoprost group exhibited a trend to a greater diurnal IOP reduction from an untreated baseline (24.9+/-3.2-17.4+/-2.9) compared with timolol (24.7+/-2.8-18.3+/-1.9 mmHg) (P=0.07). Latanoprost showed a significantly greater IOP reduction at 0800 hours (-8.5 vs -6.0 mm Hg for timolol, P<0.0001) whereas no difference was observed between the two medications at 1000, 1400, and 2000 hours after a Bonferroni Correction. In addition, latanoprost demonstrated a narrower range of diurnal IOP (2.4) than timolol (3.2 mmHg)(P=0.0017). Safety was similar between groups, except there was more conjunctival hyperaemia with latanoprost (n=8) than timolol (n=1)(P=0.01). CONCLUSIONS: This study suggests that latanoprost provides a statistically lower 08:00-hour IOP and better range of IOP than timolol in the treatment of XFG glaucoma.

Proposed classification for topographic patterns seen after penetrating keratoplasty.

AIMS: To create a clinically useful classification for post-keratoplasty corneas based on corneal topography. METHODS: A total of 360 topographic maps obtained with the TMS-1, from 95 eyes that had undergone penetrating keratoplasty (PKP), were reviewed independently by two examiners in a masked fashion, and were categorised according to a proposed classification scheme. RESULTS: A high interobserver agreement (88% in the first categorisation) was achieved. At 12 months post-PKP, a regular astigmatic pattern was observed in 20/85 cases (24%). This was subclassified as oval in three cases (4%), oblate symmetric bow tie in six cases (7%), prolate asymmetric bow tie in six cases (7%), and oblate asymmetric bow tie in five cases (6%). An irregular astigmatic pattern was observed in 61/85 cases (72%), subclassified as prolate irregular in five cases (6%), oblate irregular in four cases (5%), mixed in seven cases (8%), steep/flat in 11 cases (13%), localised steepness in 16 cases (19%), and triple pattern in three cases (4%). Regular astigmatic patterns were associated with significantly higher astigmatism measurements. The surface asymmetry index was significantly lower in the regular astigmatic patterns. CONCLUSIONS: In post-PKP corneas, the prevalence of irregular astigmatism is about double that of regular astigmatism, with a trend for increase of the irregular patterns over time.

Combined interrupted and continuous versus single continuous adjustable suturing in penetrating keratoplasty: a prospective, randomized study of induced astigmatism during the first postoperative year.

OBJECTIVE: To compare postoperative astigmatism induced by two different suturing techniques in penetrating keratoplasty (PKP). DESIGN: A monocenter, prospective, randomized clinical trial with a longitudinal 1-year follow-up. PARTICIPANTS: A total of 95 eyes undergoing PKP were randomized into 2 groups. Of these, 51 eyes were allocated to the combined interrupted and continuous suturing group (ICS) and 44 eyes to the single continuous adjustable suturing (SCAS) group. INTERVENTION: In the ICS group, suturing was with a combination of 12 interrupted 10-0 nylon and 1 continuous 11-0 nylon sutures. Eyes in the SCAS group had been sutured with a single running 24-bite 10-0 nylon. Selective suture removal started no earlier than 10 weeks after surgery; suture adjustment could start as soon as possible after surgery. MAIN OUTCOME MEASURES: Astigmatism was measured by topography, keratometry, and refraction at 3-, 6-, 9-, and 12-month postoperative intervals. RESULTS: The difference in mean time of suture manipulation between groups was significant (P = 0.0001), with the SCAS starting earlier. A significant decrease in astigmatism occurred by either interrupted suture removal (6.69 +/- 3.11 diopter [D] before to 4.76 +/- 2.99 D after, P = 0.0002) or suture adjustment (7.18 +/- 3.12 D before to 4.46 +/- 3.24 D after, P = 0.0001). However, the net astigmatic reduction in the SCAS group was not significantly greater (P = 0.250) than in the ICS group. Vector change was 7.40 +/- 4.17 D and 6.28 +/- 4.14 D for SCAS and ICS, respectively (P = 0.13). At no interval (3, 6, 9, or 12 months) was there significant difference in astigmatism between the two groups. Refractive astigmatism (cyl, D) at 1 year was 2.66 +/- 1.70 for the ICS and 3.12 +/- 2.62 for the SCAS, but there was no significant treatment effect (P = 0.945). Furthermore, 66% of the ICS eyes and 58% of the SCAS eyes (P = 0.295) were within the astigmatic target of the study (<3.5 D). CONCLUSIONS: Postkeratoplasty astigmatism can be decreased similarly with either adjustment of a single running suture or selective removal of interrupted sutures. No advantage of the SCAS over ICS in terms of fewer manipulations or less astigmatism was seen as suggested previously.

Surgical control of late postkeratoplasty astigmatism with or without the use of computerized video keratography: a prospective, randomized study.

OBJECTIVE: To assess the effectiveness of computerized videokeratography (CVK) in refining the surgical design and in improving predictability of surgical correction of postkeratoplasty astigmatism. DESIGN: A prospective, controlled, randomized, clinical trial. PARTICIPANTS: A total of 31 postkeratoplasty eyes, divided into 2 groups (group A, 16 eyes; group B, 15 eyes), with more than 4 diopters (D) of disabling astigmatism were studied. INTERVENTION: All eyes were treated with a combination of arcuate relaxing incisions and compression sutures. The surgical plan in group A was based on topographic information, whereas in the control group B, the surgical plan was based on information obtained by refraction and keratometry alone. MAIN OUTCOME MEASURES: Change in the surgical plan induced by the CVK information, astigmatism, topographic patterns, and factors associated with outcome were measured. RESULTS: In all 16 cases of group A, the use of CVK changed some aspect of the surgical plan. At 12 months after surgery, both groups showed a significant net reduction (P = 0.001) of baseline astigmatism. However, the reduction (47% and 41 % for groups A and B, respectively) did not differ significantly between the two groups. The topographic astigmatism at 12 months measured 4.24 +/- 0.71 D in group A and 5.60 +/- 0.51 D in group B (P = 0.139). Significant differences between the two groups at 12 months were seen only for keratometric astigmatism (3.60 +/- 0.81 D in group A vs. 5.77 +/- 0.52 D in group B, P = 0.035) and refractive astigmatism (2.34 +/- 0.37 D in group A vs. 4.88 +/- 0.52 D in group B, P = 0.000). The mean vector surgical effect was 91 % for group A and 70% for group B. Regular astigmatism patterns had a greater benefit from surgery than irregular patterns (P = 0.008). Previous refractive surgery was associated with less-favorable outcome (P = 0.045). CONCLUSIONS: The current study indicates that the use of CVK provides a benefit compared to keratometry and refraction alone in the planning and outcome of surgical treatment for high postgraft astigmatism.

Clinical evaluation of keratometry and computerised videokeratography: intraobserver and interobserver variability on normal and astigmatic corneas.

AIMS: To evaluate intra- and interobserver variability in measurements on normal and astigmatic corneas with keratometry and computerized videokeratography. METHODS: Keratometric readings with the 10 SL/O Zeiss keratometer and topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal and 33 postkeratoplasty corneas. Inter- and intraobserver coefficients of variability (COR) for measurements of steep and flat meridian power and location, in addition to the magnitude of astigmatism, were assessed. RESULTS: Compared with TMS-1, the 10 SL/O keratometer showed a superior repeatability in measuring normal corneas (intraobserver COR for keratometry and TMS-1 respectively: 0.22 and 0.30 D for steep meridian power; 0.18 and 0.44 D for flat meridian power; 0.26 and 0.40 D for astigmatism; 5 degrees and 26 degrees for steep meridian location; 5 degrees and 13 degrees for flat meridian location). Astigmatism intraobserver COR (0.20 D and 0.26 D for the two observers) and interobserver COR (0.28 D) of the keratometer for normal corneas was very good and not affected by observers' experience. Repeatability of the TMS-1 on normal corneas was found to be: (a) observer related, and (b) astigmatism related. A novice observer showed a much greater COR (1.62 D for astigmatism, 30 degrees for flat meridian location) compared with the experienced examiner (0.40 D for astigmatism, 13 degrees for flat meridian location). Higher deviation scores were observed for corneas with higher astigmatism. For the postkeratoplasty corneas, again the keratometer achieved superior reproducibility (astigmatism interobserver COR 1.12 D for keratometry, 4.06 D for TMS-1; steep meridian location interobserver COR 10 degrees for keratometry, 34 degrees for TMS-1). CONCLUSION: Keratometric readings are more reproducible than topographic data both for normal and postkeratoplasty corneas. The two instruments should not be used interchangeably especially on highly astigmatic corneas. For the TMS-1, users with the same level of experience should be employed in clinical or experimental studies.

Different therapeutic approaches and outcome in the treatment of pterygium.

PURPOSE: This study was initiated to investigate the role of different therapeutic modalities in the outcome of the surgical treatment of pterygium. METHODS: The results of treatment of pterygia with a variety of surgical techniques were studied in 56 eyes (49 patients) operated on at Bristol Eye Hospital during a period of five years. The surgical techniques included simple excision; bare sclera; conjunctival autograft; sliding conjunctival flap; lamellar keratoplasty and penetrating keratoplasty. Twelve eyes received additional beta irradiation in a fractionated total dose of 40 Gys. RESULTS: The incidence of recurrence was 23.2% for the 43 treated primary pterygia, and 23% for the 13 recurrent pterygia. All recurrences occurred between 2.5 and 11 months postoperatively. None of the 11 cases where additional beta irradiation was used showed any recurrence or other complication within the study period. In the recurrent pterygia group, the cases treated with a combination of surgical excision and beta irradiation, showed significantly lower recurrence rate (p < 0.001) compared to those cases treated with surgical excision alone. CONCLUSIONS: Beta irradiation as a complement to surgical treatment of pterygium, is successful in treating high risk cases such as reoperations, whereas for the majority of primary pterygia surgical excision alone is adequate. Additionally, follow up of one year will reveal any recurrences.

Comparison of keratometry and videokeratography after penetrating keratoplasty.

BACKGROUND: As new methods for corneal curvature measurement have evolved, users of videokeratscopes need to know the practical limitations of these instruments. We assessed agreement between keratometry and videokeratography in measuring highly astigmatic corneas. METHODS: Two independent examiners made three keratometric and videokeratographic measurements on each of 33 corneas after penetrating keratoplasty. The non-orthogonal keratometric readings obtained with a Zeiss 10 SL/O keratometer (Carl Zeiss Ltd.) were compared to the non-orthogonal simK readings (maxK, minK) calculated by the algorithms of a TMS-1 videokeratoscope (Tomey). Measurement agreement was evaluated for steep and flat meridian power and location, and astigmatism magnitude (D). RESULTS: A systematic bias of the TMS-1 in measuring steeper than keratometry for the steep meridian was demonstrated (95% confidence interval: -0.34 to -1.20 D). The limits of agreement (d - 2SD to d + 2SD) between the two instruments were found to be unacceptable for clinical purposes in measuring steep meridian power (-3.17 to +1.63 D), flat meridian power (-4.92 to +4.48 D) and astigmatism magnitude (-5.84 to +4.87 D). Clinically acceptable differences were observed in identification of steep and flat meridian location. CONCLUSIONS: The Zeiss 10 SL/O keratometer and the TMS-1 videokeratoscope showed poor measurement agreement for irregular corneal surfaces, despite the good correlation previously shown between keratometry and videokeratography in calibrated spheres and regular corneas. The TMS-1 showed a systematic bias, measuring a greater power in the steeper meridian than the Zeiss 10 SL/O keratometer. It is suggested that the two instruments cannot be used interchangeably in comparing the curvature of corneas after penetrating keratoplasty.

Cilioretinal artery occlusion following scleral reinforcement surgery.

A 12-year-old high myope girl presented with a cilioretinal artery occlusion in her left eye. Three years previously, she had undergone posterior scleral support surgery to prevent the progression of her myopia. The general medical workup of the patient did not reveal any causative factor for retinal artery occlusion. A possible relation between the cilioretinal artery obstruction and the previous scleral reinforcement surgery is postulated based on two proposed mechanisms.

Epithelial downgrowth following penetrating keratoplasty with a running adjustable suture.

A 78-year-old female patient who had a third penetrating keratoplasty for aphakic bullous keratopathy and iris fixation of a posterior chamber intraocular lens using a single, 10-0 nylon running suture technique developed a suture track leak postoperatively. Attempts to ease the tension on the suture track reduced the astigmatism and stopped the leak temporarily. Eighteen months after the procedure, epithelial downgrowth was noted on the corneal graft on both sides of the leak site and intraocular pressure was elevated. A fourth penetrating keratoplasty combined with a trabeculectomy was performed. To our knowledge, this is the first report of epithelial downgrowth associated with suture adjustment following the single, continuous suture technique.

Cyanoacrylate glue treatment for persistent aqueous leak following postkeratoplasty relaxing incisions with compression sutures.

In spite of improvements in surgical techniques, donor materials and postoperative care, high astigmatism remains a quite common problem following penetrating keratoplasty [1]. Whenever the residual astigmatism cannot be corrected with spectacles or contact lenses, surgical treatment is required. Relaxing incisions combined with compression sutures is one of the most common methods used for this purpose [2, 3]. We report herein a case of persistent aqueous leak following relaxing incisions for the correction of postkeratoplasty astigmatism. The leak failed to respond to a bandage contact lens and resuturing and was eventually successfully treated with the use of cyanoacrylate glue. A marked regression of the surgical effect was observed in this case.

Topographic analysis in pellucid marginal corneal degeneration and keratoglobus.

Pellucid marginal corneal degeneration (PMCD) is an uncommon cause of inferior peripheral corneal ectasia, affecting patients between the ages of 20 and 40 years. Although histopathologically it is considered a variant of keratoconus, it differs in that the marked corneal steepening occurs more inferiorly, above a narrow band of corneal stromal thinning concentric to the inferior limbus. Here we present two cases. The first case is a clinically typical bilateral PMCD with a characteristic pattern of irregular against-the-rule astigmatism on corneal topography. The second case had an uncommon presentation of hydrops in a clinically keratoglobic eye which showed a marked steepening of the inferior corneal periphery on corneal topography. The other eye showed both clinically and topographically the features of PMCD. Corneal topography suggested that in the second patient, PMCD may have preceded the development of keratoglobus. Keratoconus, PMCD and keratoglobus are considered to be associated as part of the spectrum of non-inflammatory corneal thinning disorders. However, although the finding of PMCD and keratoconus in fellow eyes has been reported, to the best of our knowledge progression from PMCD to keratoglobus has not previously been shown.

Acanthamoeba keratitis: risk factors and outcome.

AIMS/BACKGROUND: This study was initiated to investigate risk factors for and outcome of Acanthamoeba keratitis. METHODS: Results of treatment were studied in 22 patients (23 eyes) presenting to Bristol Eye Hospital between 1985 and February 1995. Details related to the use and disinfection of contact lenses were also obtained. An additional two patients who were seen at Bristol but mainly treated elsewhere were surveyed for contact lens related information only. RESULTS: The incidence of Acanthamoeba keratitis rose substantially in the 1990s: three patients presented before 1990, while the remaining 21 presented between January 1990 and February 1995. Eleven patients have presented since january 1994. All of the patients in this series were contact lens wearers, 16 (67%) using daily wear disposable contact lenses. Contact lens disinfection data were available in 22 patients of whom 11 (50%) were using chlorine disinfectant. Other types of disinfection were much less common. Four patients (18%) had not used any disinfectant. During the course of the series the average diagnostic delay has fallen markedly, although in 77% of patients a diagnosis of a viral keratitis, most commonly herpes simplex, was made on first presentation. All but three of the series were treated with a combination of polyhexamethylene biguanide and propamidine isethionate. Penetrating keratoplasty was performed in 9/23 eyes (39%); in all of these eyes diagnosis was delayed for at least 6 weeks. All but one of the eyes in the series achieved a visual acuity of 6/9 or better after treatment, and 18 eyes (78%) saw 6/6 or better. CONCLUSIONS: Most patients with Acanthamoeba keratitis can now expect a good visual result and cure by medical therapy alone is favoured by early diagnosis.