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Biomedical subjects

I G Bryce

Publications and source records attributed to I G Bryce.

10 recordsLinked to original sources
PubMed1996

Natural history of central topographic islands following excimer laser photorefractive keratectomy.

PURPOSE: To assess the incidence and natural history of central corneal topographic islands following excimer laser photorefractive keratectomy (PRK) and photoastigmatic refractive keratectomy (PARK). SETTING: A dedicated corneal diseases and refractive surgery unit within a National Health Service Trust ophthalmology unit in the United Kingdom. METHODS: Corneal topographic analysis was performed in a prospective study of 100 eyes of 75 consecutive patients who had PRK. All PRK/PARK excimer laser photorefractive procedures were performed by two surgeons observing a standardized protocol using a VISX 20/20 excimer laser. Mean preoperative myopic error was 5.54 diopters (D) +/- 3.44 (SD). Corneal topographic analysis was performed on all eyes preoperatively, 1 week postoperatively, and monthly thereafter for a minimum of 6 months or until central islands, if present, resolved. All patients had a minimum 12 months follow-up. RESULTS: Postoperatively, 29 eyes (29%) demonstrated central corneal topographic islands of greater than 3.00 D topographic power by computerized videokeratography (CVK). All central islands were identified in the first 4 weeks postoperatively. In all cases the differential dioptric power, created by the central islands within the ablation zone, decreased rapidly; within 6 months, 26 (90%) central islands had fully resolved without further treatment, and the remaining 3 (10%) resolved within 1 year of photorefractive surgery. The occurrence of central islands was related to higher preoperative myopic spherical equivalent (P = .01), greater attempted laser correction (P = .01), and greater projected depth of ablation (P = .01) (Student's two-tailed t-test). CONCLUSIONS: Central corneal topographic islands occurred in a significantly higher proportion of eyes having excimer laser photorefractive surgery than previously believed. The islands were associated with decreased unaided vision, reduced best spectacle-corrected acuity, and other troublesome visual symptoms; however, the central islands, along with their associated visual effects, usually resolved without surgical intervention within 6 months postoperatively.

Adult↗
PubMed1996

Decentration of photorefractive keratectomy ablation zones after excimer laser surgery for myopia.

PURPOSE: To devise a method for measuring excimer laser photorefractive keratectomy (PRK) ablation zone decentration. SETTING: Excimer Laser Clinic, Sunderland Eye Infirmary, Sunderland Tyne and Wear, England. METHODS: Fifty-three eyes of 53 consecutive patients having PRK for a spherical myopic refractive error were studied. Preoperative and postoperative corneal topographic maps and differential subtraction maps were produced for each cornea. Using these maps, the distance between ablation zone centers and pupil centers was measured. All measurements were repeated by a second observer. RESULTS: Mean ablation zone decentration was 0.46 mm from the pupil center; 69% of cases decentered 0.50 mm or less. The difference between the two independent measurements was 0.05 +/- 0.06 mm (mean +/- SD). A trend toward superonasal displacement was noted. CONCLUSION: This simple method of measuring zone decentration can be used to compare the refractive results of PRK with those of other procedures.

Cornea↗
PubMed1996

Corneal topographic lagoons: a potential new marker for post-traumatic recurrent corneal erosion syndrome.

BACKGROUND: Post-traumatic recurrent corneal erosion syndrome is a common clinical problem in which a definitive diagnosis is not always possible based solely upon biomicroscopic corneal signs. Indeed, in some cases archetypical symptoms or a preceding history of epithelial trauma cannot always be elucidated. METHODS: Four groups of patients underwent corneal analysis using computer videokeratography. Group 1 (n = 11), subjects who presented with simple corneal epithelial trauma approximately three months before the study. Group 2 (n = 11), prospective analysis of subjects presenting with simple corneal epithelial trauma. Group 3 (n = 12), prospective analysis subjects with an established diagnosis of post-traumatic recurrent erosion syndrome. Group 4 (n = 135), prospective analysis of healthy control subjects. RESULTS: Small, well delineated areas (1.0 to 1.5 mm in diameter) of markedly reduced corneal dioptric power (greater than 2 dioptres), which we have termed 'corneal topographic lagoons', were identified more commonly in eyes with recurrent corneal erosion syndrome and in eyes that had recently sustained corneal epithelial trauma; being found in 18.2% of Group 1, 9.1% of Group 2, 58.3% of Group 3 but only 1.5% of Group 4 (control). CONCLUSIONS: The identification of areas of focal abnormality in the corneas of patients with post-traumatic recurrent corneal erosion syndrome remains a significant clinical problem. Corneal topographic analysis has demonstrated a focal abnormality, the 'corneal topographic lagoon', which is much more prevalent in cases of recent corneal trauma and recurrent corneal erosion syndrome than in the 'normal' population. Computerised videokeratography therefore adds a new tool to the armamentarium of the clinician seeking to identify and locate abnormalities in these difficult cases.

Adolescent↗
PubMed1996

Deep corneal stromal opacities associated with long term contact lens wear.

BACKGROUND: One male and three female long term contact lens wearers (mean age 30.3 years; range 26-33) demonstrated unusual deep corneal stromal opacities which were predominantly just anterior to Descemet's membrane. None had any history of corneal dystrophy. These opacities were more common centrally, but were also identified in the corneal periphery. METHODS: All patients underwent routine ophthalmic examinations and, where appropriate, slit-lamp photography and specular microscopy. RESULTS: Mean lens wear in years and hours per day was 14.3 (range 10-17) and 14.3 (range 12-16) respectively. Specular microscopy disclosed cell densities within normal limits (mean 3041.5 cells per mm2) and coefficient of variation of mean cell area; COV = 0.31. Refractive errors ranged from -12.25 D to +6.25 best vision sphere and all four subjects attained at least 6/9 Snellen visual acuity. The subjects' contact lens wearing history included low water content hydroxymethylmethacrylate (HEMA) contact lenses and high water content HEMA contact lenses. Stromal opacity density was observed to diminish over a period of months on cessation of contact lens wear in two cases. CONCLUSION: The possible causes of these rarely reported opacities are discussed.

Adult↗
PubMed1996

Psychological aspects of excimer laser surgery for myopia: reasons for seeking treatment and patient satisfaction.

AIMS: To determine the reasons patients seek excimer laser treatment for myopia and to measure levels of patient satisfaction with each phase of this relatively new treatment. METHODS: A unique 38 item visual analogue questionnaire was developed and applied to 100 consecutive patients (n = 100) who had undergone excimer laser photorefractive keratectomy for myopia or myopic astigmatism at a single centre. All subjects underwent extensive ophthalmic assessment and patient education before treatment. RESULTS: A 90% response rate was achieved (n = 90). Improved unaided vision (85.6%), freedom from spectacles (83.3%), and difficulties with contact lens wear (72.7%) were the most common reasons for seeking treatment. The majority of patients felt that the quality of their life had improved (85.5%) and 82% felt that the quality of their unaided vision was as good as they had anticipated. overall, 95.5% of patients were pleased that they had undergone this procedure. The vast majority (98.9%) of patients felt that they fully understood the operation pretreatment but almost one quarter (23.9%) found the actual operation distressing. Only 15.7% found postoperative pain did not respond adequately to prescribed analgesia. CONCLUSIONS: This study demonstrates a very high level of patient satisfaction after excimer laser treatment for myopia and myopic astigmatism. It suggests that most patients seek treatment to enjoy better vision free from optical aids and that a high level of patient education preoperatively may establish realistic expectations and satisfaction with overall outcome.

Adult↗
PubMed1995

Corneal tattooing revisited: excimer laser in the treatment of unsightly leucomata.

BACKGROUND: Corneal tattooing, a procedure first used by Galen in the treatment of unsightly leucomata, has in recent times received relatively little attention due to major advances in intraocular and corneal surgery. Resurrection of the technique, however, may be reasonably considered in 'high risk' cases of leucomata or leucocoria where corneal transplantation would lead to rejection and failure, or, in eyes with no visual potential, where removal of cosmetically unacceptable dense, white cataracts carries an unreasonable risk of phthisis bulbi or sympathetic ophthalmitis. METHODS: Corneal tattooing requires the accurate and limited removal of corneal epithelium to act as the tattoo bed and unfortunately, if removal of the epithelium exceeds, or goes beyond the circumference of, the chosen area, a ragged cosmetically less pleasing 'pupil' is created. The excimer laser appears to be an ideal tool to create a perfectly circular corneal bed to improve upon older techniques. CONCLUSION: We report, for the first time, an updated, simple and improved technique for successful corneal tattooing using excimer laser technology.

Adult↗
PubMed1995

Hazy days? The refractive outlook of photo-refractive keratectomy/photo-astigmatic keratectomy.

The refractive outcome of 100 healthy myopic eyes which had undergone excimer laser (VISX 20/20) was evaluated at 6 months post-treatment. Patients were subdivided into Group A (n = 51, < -5.00 D spherical equivalent (SE)), Group B (n = 38, -5.00 to < -10.00 D SE) and Group C (n = 11, > -10.00 D SE). The mean myopic sphere decreased from -2.88 to -0.22 DS, -5.94 to -0.43 DS and -12.61 to -1.83 DS, respectively. Cylinder reduction ranged from 23 to 53%, effectiveness: decreasing with increasing associated myopia. Sixty-six percent of all subjects attained an SE correction within 1.00 D of that attempted, however, 80% actually achieved vision of 6/12 or better. At 6 months only six eyes were not within one line of their pre-operative best spectacle visual acuity (BSVA) and four of these exhibited haze greater than Grade 1. In low myopia, photorefractive keratectomy (PRK) appears to be highly successful with 93% of subjects with an initial myopia of < -5.00 D SE obtaining 6/12 or better vision. However, photo-astigmatic refractive keratectomy (PARK) was variable within all groups.

Adult↗
PubMedDate not supplied

Visual loss in infantile osteopetrosis.

Osteopetrosis should be considered in an infant with unexplained visual loss. In particular, the possibility of this diagnosis must be intimated to the radiologist involved in the investigation of the child.

Blindness↗