Evanne J. Casson

Laser vision correction for low hyperopia. An 18-month assessment of safety and efficacy.

OBJECTIVE This study aimed to assess the efficacy and safety of hyperopic photorefractive keratectomy (PRK) and to evaluate the effect of degree of hyperopia, two epithelial removal methods, and various postoperative patient management techniques on clinical outcomes. DESIGN Prospective, nonrandomized, open-label clinical trial. PARTICIPANTS A total of 38 patients with mean follow-up of 13.9 months (n = 65 eyes with hyperopia from +1.00 diopter [D] to +4.00 D) participated. INTERVENTION Hyperopic PRK with the VISX STAR Excimer Laser System was performed. MAIN OUTCOME MEASURES Spherical equivalent (SE) including vector analysis of SE; uncorrected visual acuity (UCVA); best-spectacle corrected visual acuity (BSCVA); low-, medium- and high-contrast visual acuities; topography; keratometry; pachymetry; and intraocular pressure, haze, and all other potential complications were measured. RESULTS A total of 80% of eyes were within +/- 0.5 D and all but 1 eye (98%) were within +/- 1.0 D of intended manifest SE at 1 year. There was no induced astigmatism at 1 year. At 12 months, 72% of eyes had UCVA of 20/25 or better and 70% had achieved preoperative BSCVA, with no eye seeing worse than 20/25. These results remained constant at 18 months. There was a tendency toward regression between months 1 and 6 with stabilization of SEs between months 6 and 12. Thereafter, up to 18 months, there was some regression with a mean of +0.31 D, but the number of patients was small. There was one mild decentration and very slight decreases in mean intraocular pressure and central corneal thickness. One patient had grade 1.0 haze develop in both eyes at 12 and 18 months; all other patients experienced trace or no haze. There were no significant complications. CONCLUSIONS The results of this study support the hypothesis that laser vision correction is safe and effective for treating low hyperopia. The predictability of the hyperopic laser vision correction procedure used in this study was very good. Other than the slower recovery of BSCVA and UCVA seen with this procedure, as compared with myopic PRK, there were no significant complications. The trend toward some later regression needs to be further evaluated in a larger number of patients. Overall, patients were very pleased with the treatment, even in the first 6 months.

The impact of visual field loss on driving performance: evidence from on-road driving assessments

Purpose. The purpose of this study was to investigate the relationship between visual field loss and driving performance as determined by on-road driving assessments. Methods. We reviewed the files of 1350 patients enrolled in a rehabilitation program at the Bloorview MacMillan Rehabilitation Centre, Toronto, Canada. We identified 131 patients with visual field loss who had undergone an on-road driving assessment. These patients had a primary diagnosis of visual impairment or a primary diagnosis of cerebral vascular accident (CVA) with a secondary diagnosis of visual impairment. None of these patients had documentation of neglect, substantial motor or cognitive deficits. We report the data obtained from 13 hemianopics, 7 quadrantanopics, 25 patients with monocular vision, 10 patients with moderate peripheral losses (<135° of horizontal visual field measured at the midline), and 76 patients with mild peripheral losses (between 135° and 186° of horizontal visual field). The on-road assessment consisted of driving in the area surrounding the rehabilitation center, and the outcome was based on performance on a number of tasks commonly encountered in daily driving. For the purposes of this study, the assessment outcomes were classified as safe, unknown, or unsafe. Results. Overall, the extent of visual field loss did not have a significant impact on driving performance (&khgr;2 = 4.37, p = 0.358). However, hemianopia tended to have a worse impact on driving performance than quadrantanopia with a marginally significant result (&khgr;2 = 3.33, p = 0.068). Overall, the location of the visual loss was not significantly related to driving fitness (&khgr;2 = 1.05, p = 0.30). However, localized defects in the left hemifield (&khgr;2 = 9.561, p = 0.002) and diffuse visual loss in the right hemifield (&khgr;2 = 10.395, p = 0.001) seemed to be associated with driving impairments. A large proportion of monocular drivers were safe drivers and the location of their deficit had no significant impact. Conclusions. Although the extent of visual field defects appears to be related to driving performance as determined by an on-road driving assessment, large individual differences were observed. This highlights the need for individualized on-road assessments for patients with visual field defects.

Vision standards for driving in Canada and the United States. A review for the Canadian Ophthalmological Society.

We review the vision requirements for driving with the goal of revising current Canadian Ophthalmological Society (COS) recommendations for vision standards for driving. The report comprises two sections. In the first section we report the results of a survey of transportation authorities in Canada and the United States conducted on behalf of the COS to determine the current standards and medical review procedures. The results suggest that although the standards in Canada are more consistent than those in the United States, few of the standards in either country are evidence-based. In the second section we review the recent literature on visual function and driving. We conclude from this review that adequate contrast sensitivity is as important as, if not more important than, good visual acuity for driving and that there is little evidence to support a monocular standard for acuity, contrast sensitivity or visual field. Although there is evidence that the extent of a visual field defect is related to the ability to perform driving tasks, there is little evidence to suggest a relation between the location of the visual field defect and fitness to drive.

The temporal order judgment paradigm : subcortical attentional contribution under exogenous and endogenous cueing conditions

The role of subcortical attentional processing was investigated under exogenous and endogenous cueing conditions. As retinotectal projections arise predominantly from the nasal retina i.e., temporal hemifield, subcortical attention should be distributed asymmetrically under monocular viewing conditions with a temporal hemifield advantage. We compared the results of monocular and binocular viewing conditions using a temporal order judgment (TOJ) paradigm. Subjects fixated a centrally located cross and two stimuli were presented with a variable onset asynchrony. Three experiments were conducted: no cue, exogenous cue and endogenous cue. Subjects reported which stimulus seemed to appear first. An effect consistent with subcortical processing was found under exogenous cueing conditions. No such effect was found under endogenous cueing conditions. We believe that subcortical attentional processing in response to an exogenous cue facilitates rapid shifts in attention towards environmental stimuli. We found no evidence for subcortical processing in voluntary directed attention and believe this process to be cortical in nature.

Excimer laser photorefractive keratectomy for low hyperopia: Safety and efficacy

Purpose: To assess the safety and efficacy of photorefractive keratectomy (PRK) to correct low hyperopia. Setting: University of Ottawa Eye Institute, Ottawa General Hospital, Ontario, Canada. Methods: Twenty‐five eyes with refractions of +1.00 to +4.00 diopters (D) and cylinder of 1.00 D or less were treated for hyperopia with the VISX Star excimer laser system using a refined ablation architecture. Thorough visual assessments were performed preoperatively (baseline) and 1, 3, and 6 months postoperatively. Complications were recorded and the level of patient satisfaction was noted. Results: Mean spherical equivalent at 6 months was +0.27 D ± 0.55 (SD), which was an 89% reduction over baseline. Eighty‐four percent of patients gained two to seven lines of near uncorrected visual acuity (UCVA) and 1 patient (4%) lost more than one line. Eight percent achieved 20/25 or better UCVA. Approximately half realized their preoperative distance best corrected visual acuity (BCVA) by 1 month. By the end of the study, all patients had improved, achieved, or were within one line of their baseline distance BCVA. There were some slight reductions in lower contrast acuity at 6 months, although dim lighting conditions did not further reduce these acuities. Most patients had no clinically meaningful change in cylinder. The most common complications included early, transient corneal surface irregularities and visual symptoms and trace haze (grade ≤0.5) in 14 of 23 patients at 6 months. All but 1 patient expressed a high degree of satisfaction. Conclusions: These results support the hypothesis that PRK shows great promise as a safe and effective treatment for low hyperopia. There were no significant complications and no decentered ablations. The slight regression occurred with or without the presence of trace haze. Overall, refractive stability was encouraging, although longer follow‐up is needed.

An investigation of the visual disturbances experienced by patients on clomiphene citrate

OBJECTIVE To evaluate the impact of clomiphene citrate on vision. DESIGN Observational study. SETTING Patients were referred to the University of Ottawa Eye Institute ophthalmology clinic from the Department of Obstetrics and Gynaecology of the Ottawa Hospital-General Campus. PATIENT(S) Eight adult females taking clomiphene citrate and experiencing visual disturbances. INTERVENTION(S) Patients received a comprehensive visual evaluation twice: once during a washout period, and once during an active clomiphene citrate treatment. MAIN OUTCOME MEASURE(S) Ophthalmologic examination, color vision, visual acuity, contrast sensitivity, visual fields using standard automated perimetry, and foveal flicker sensitivity at high (32 Hz) and low (8 Hz) temporal frequencies. RESULT(S) We found no differences between the washout and clomiphene citrate conditions for color vision, visual acuity, contrast sensitivity, and visual fields. The only statistically significant difference was found for foveal flicker sensitivity at 32 Hz in the right eye, with a similar trend in the left eye and at 8 Hz in both eyes. CONCLUSION(S) The effect of clomiphene citrate on vision was minimal, and the visual disturbances were reversible in all patients. A bilateral reduction in flicker sensitivity was the only observed visual disturbance. Women who experience visual symptoms associated with clomiphene citrate should be monitored, but therapy can usually be maintained.