Improvement of visual function with glare testing after photorefractive keratectomy and radial keratotomy

Evaluation of a New Controlled Point Source LED Glare Tester for Disability Glare Detection in Participants With and Without Cataracts

PURPOSE

To determine glare-induced change during visual acuity testing in patients with and without cataract using the controlled point source light-emitting diode (LED) glare tester (EpiGlare Tester; Epico, LLC, Columbus, OH), a new medical device for identification of glare disability.

METHODS

This prospective, multicenter study enrolled 40 patients (80 eyes with cataracts) and 49 control subjects (98 eyes without cataracts). Corrected distance visual acuity (CDVA) was measured with and without glare using the EpiGlare Tester as a glare source. Functional visual ability was evaluated using driving and glare subscales from the Refractive Status Vision Profile questionnaire. The primary efficacy measure was change in CDVA measurement with and without glare in patients with senile cataract compared to participants without cataract. Secondary efficacy measures included correlation of the CDVA change caused by functional glare disability and subjective patient and investigator assessments.

RESULTS

CDVA reduction was greater for patients with cataract, with a mean reduction of -0.49 ± 0.3 logMAR, than for participants without cataracts at -0.13 ± 0.2 logMAR (P < .001). This equates to a 5-line Snellen reduction (0.49 logMAR) in patients with cataracts and a 1-line reduction (-0.13 logMAR) in patients without cataracts. Among patients with cataracts, 83% stated the device accurately represented the difficulty experienced while driving at night (P < .001); among participants without cataracts, 71% reported being minimally affected by glare from the device (P = .003).

CONCLUSIONS

A new controlled point source LED glare tester demonstrated the adverse effect on visual acuity due to glare in patients with cataract, accurately simulated night driving glare issues for patients with cataracts, and was rated as easy to use and useful by investigators.

Retrospective evaluation of the influence of pupil size on visual acuity after KAMRA inlay implantation

PURPOSE

To investigate the influence of pupil size on visual acuity after KAMRA inlay (AcuFocus, Inc., Irvine, CA) implantation.

METHODS

Five hundred eighty-four presbyopic eyes of 584 patients who underwent LASIK were evaluated. Uncorrected near visual acuity (UNVA), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and corrected near visual acuity (CNVA) were measured. Two groups were classified: small pupil (pupil diameter < 6 mm) and large pupil (pupil diameter ≥ 6 mm) for both mesopic (pupil diameter < 4 mm) and photopic (pupil diameter ≥ 4 mm) pupil size parameters. The follow-up period was 6 months.

RESULTS

There were no significant differences in UNVA (P = .98) and CNVA (P = .16) between the mesopic pupil size groups; however, there were significant differences in UDVA (P = .023) and CDVA (P = .039). There was a weak correlation between pupil size and UDVA of the large mesopic pupil size group (rs = 0.129, P = .04). There were no significant differences in UNVA (P = .78), CNVA (P = .92), UDVA (P = .19), and CDVA (P = .60) for the photopic pupil size groups.

CONCLUSIONS

Pupil size does not have an influence on the resultant visual acuity after KAMRA inlay implantation. No correlation was found between preoperative and postoperative pupil size and visual acuity for the mesopic pupil groups.

Photophobia measurement in intermittent exotropia using the contrast sensitivity test

BACKGROUND

To assess the presence and extent of photophobia in children with intermittent exotropia (X[T]) using the contrast sensitivity test.

METHODS

Fifty-eight children with X(T) and 34 normal controls were studied with the functional acuity contrast test. Each participant viewed the stimuli of contrast monocularly and binocularly under photopic and mesopic conditions, performed with and without glare. Photophobia was defined as a reduction of contrast sensitivity caused by glare light. We compared the photophobia of children with X(T) to that of normal controls, and to the photophobia 3 months after muscle surgery.

RESULTS

With stimuli of glare, the contrast sensitivity of children with X(T) was suppressed at intermediate spatial frequencies under mesopic condition (p = 0.006 for 6 cycles per degree [cpd], p = 0.027 for 12 cpd), whereas that of normal controls showed no difference. It occurred when X(T) patients viewed targets binocularly, and significantly improved after strabismus surgery (p = 0.003 at 6 cpd). The measured photophobia of X(T) was strongly correlated to the photophobia symptoms reported by parents (p = 0.002).

CONCLUSIONS

The mesopic contrast sensitivity with glare can represent the photophobia of children with X(T). Contrast sensitivity may be a useful measure for monitoring symptoms related to X(T).

Principles of disability glare measurement: an ophthalmological perspective

Disability glare describes the loss of retinal image contrast as a result of intraocular light scatter, or straylight. It has increasingly important modern implications such as with cataract and refractive surgery or high-intensity lighting. However, its measurement has proven difficult despite many varying approaches. This article aims to explain the principles and problems associated with glare testing that are important for assessment and use of glare measures. After defining disability glare, this article discusses the importance of its measurement to current clinical practice. It explains the principles and mechanisms that underlie disability glare and its measurement. Finally, some examples of available glare tests are described to illustrate the principles discussed.

Pupil measurement using the Colvard pupillometer and a standard pupil card with a cobalt blue filter penlight

PURPOSE

To compare scotopic pupil measurements obtained with a Colvard pupillometer with measurements taken with a printed pupil gauge and penlight with a cobalt blue filter attachment in mesopic and scotopic luminance.

SETTING

The Illinois Eye Institute, Chicago, Illinois, USA.

METHODS

Pupil measurements were taken of both eyes of 38 patients (76 eyes). Any subject presenting with anterior segment disease, fixed or dilated pupils, iris abnormalities, or a history of eye disease or eye trauma was excluded. At a mesopic luminance of 2.11 foot-candles, pupil measurements were taken with a Bernell pupil card and penlight with a cobalt blue filter attachment. At a scotopic luminance of less than 2.00 foot-candles, pupil measurements were taken with the Bernell card system and the Colvard pupillometer.

RESULTS

In mesopic luminance, the mean pupil diameter was 5.17 mm (range 3.0 to 7.5 mm) with the Bernell card method. The mean difference between the Colvard in scotopic luminance and the Bernell card system in mesopic luminance was -0.04 mm (P = .0831). In scotopic luminance, the mean pupil diameter was 6.32 mm (range 4.0 to 8.0 mm) with the Bernell card method and 5.13 mm (range 3.0 to 7.5 mm) with the Colvard pupillometer, with a mean difference of -1.18 mm (P<.0001). The limits of agreement between the mesopic Bernell card system and the Colvard pupillometer were small (-0.32 to 0.24), whereas the limits of agreement between the scotopic measurements of both techniques were large (-2.18 to -0.18).

CONCLUSIONS

Under both illuminance conditions, the Bernell card system with the cobalt filter measured a larger pupil size than the Colvard pupillometer. The measurement differences between the techniques were most pronounced at the lower illumination. The limits of agreement were larger under the lower illumination, indicating more variation between techniques. This study suggests that the Bernell card system with cobalt illumination provides a generous measurement of the pupil size compared with the Colvard pupillometer, which makes it an appropriate and cost-effective screening tool for refractive surgery evaluation.

Reduction of Pupil Size and Halos With Minus Lenses After Laser in situ Keratomileusis

PURPOSE

To evaluate the amount of miosis induced by over-minused lenses and to assess subjective reduction of halos following laser in situ keratomileusis (LASIK) with such lenses.

METHODS

Part I: Infrared pupil diameter was assessed in 14 patients who had not had ocular surgery. The accommodative/miotic reflex was stimulated with concave trial lenses in -1.00-D increments up to -4.00 D while viewing the 20/40 acuity line. Part II. Subjective halos around a distant light were assessed in 14 patients following LASIK for myopia, with and without a -1.00-D lens over manifest refraction.

RESULTS

Part I: 100%, 79%, and 64% of patients clearly saw the 20/40 line with a -1.00-D lens, -2.00-D lens, and -3.00/-4.00-D lens, respectively. Mean pupil diameter decreased by 0.2 mm with the -1.00-D lens (P = .02), 0.5 mm with the -2.00-D lens (P = .003), 0.9 mm with the -3.00-D lens (P = .008,), and 1.1 mm with the -4.00-D lens (P = .008). Part II: 11 of 14 patients (79%) noticed a decrease in the size of the halo (30% average reduction) when over-minused by -1.00 D.

CONCLUSIONS

Pupil diameters and halos decreased with a -1.00-D overcorrection in patients following LASIK. Patients with pupil-dependent night halos after LASIK may benefit from mildly over-minused lenses.

Pupil size and the ablation zone in laser refractive surgery: Considerations based on geometric optics

PURPOSE

To determine whether the currently accepted method of selecting a minimum ablation zone size for refractive surgery based on dark-adapted pupil diameter is substantiated by geometric optical analysis.

SETTING

Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.

METHODS

An optical model of the anterior segment was developed to calculate the effective corneal refractive diameter (ECRD), which is the diameter of the area of cornea that refracts all incident light rays arising from objects along the line of sight though the physical pupil (PP). The concept of the entrance pupil (EP) was reexamined and developed, and the ECRD was calculated over a range of corneal curvatures (K), anterior chamber depths (ACDs), and EP sizes. The model was generalized to include oblique light rays. Calculations were performed using MatLab Optimization Toolbox software (The MathWorks).

RESULTS

For a given EP size, the ECRD was significantly influenced by K and slightly influenced by ACD.

CONCLUSIONS

For objects on the line of sight, the ECRD was smaller than the EP in all cases. Regarding rays from objects in the periphery, the ECRD expanded rapidly as the angle of oblique incidence increased. For objects on the line of sight, the ECRD is always smaller than the clinically measured pupil (EP) because the EP is substantially magnified relative to the PP. Ablation zones larger than the EP should, in theory, prevent scattered or defocused light rays from contributing to the foveal image. When considering objects in the periphery, the increase in ECRD is sufficiently rapid that current refractive procedures cannot stop scattered light from these objects from contributing to the retinal image.

Effect of pupil size on visual function under monocular and binocular conditions in LASIK and non-LASIK patients

PURPOSE

To compare binocular and monocular vision in patients treated with laser in situ keratomileusis (LASIK) and in non-LASIK patients.

SETTING

Jules Stein Eye Institute, Los Angeles, California, USA.

METHODS

This comparative cross-sectional study comprised 20 postoperative LASIK patients and 20 non-LASIK ametropic patients. LogMAR visual acuity, contrast sensitivity, and infrared pupillometry were tested. Outcome measures were better-eye monocular acuity, binocular acuity, better-eye contrast sensitivity, binocular contrast sensitivity, and pupil diameter under monocular and binocular conditions.

RESULTS

Binocular visual acuity and contrast sensitivity were statistically significantly better than the visual acuity in the better eye (P =.0047 to <.0001) in both patient groups. Pupil diameter was statistically significantly smaller under the binocular condition than the monocular condition (P <.0001) in both groups.

CONCLUSIONS

Monocular testing induced larger pupil diameters, which was associated with reduced vision compared to binocular measurements in LASIK and non-LASIK patients.

Night vision disturbances after corneal refractive surgery

A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.

Evaluation of corneal functional optical zone after laser in situ keratomileusis

PURPOSE

To evaluate the corneal functional optical zone (FOZ) after laser in situ keratomileusis (LASIK) using a primary 6.0 mm ablation diameter without a transition zone.

SETTING

University-based practice.

METHODS

In this retrospective study, 76 eyes of 53 patients who had LASIK for myopia were evaluated. The size of the preoperative and postoperative FOZ was compared in each eye. Preoperative refraction, attempted correction, and achieved correction were correlated with the preoperative and postoperative FOZ using regression analysis.

RESULTS

After LASIK, the FOZ decreased a mean 1.2 mm +/- 0.67 (SD) (P < 0.0001). The size of the FOZ was correlated with the preoperative manifest refraction, attempted correction, and achieved correction (P <.0001). The FOZ reduction was significantly correlated with the preoperative manifest refraction, attempted correction, and achieved correction (P <.05). Before LASIK, there was no correlation between the FOZ and the preoperative manifest refraction (P = 0.9427).

CONCLUSIONS

Spherical aberrations exist within the laser ablation zone and are related to the amount of myopic treatment. This has implications for patients with large pupil diameters under mesopic conditions. Future studies are necessary to understand the implications in patients with high refractive errors.

Choice of Spatial Frequency for Contrast Sensitivity Evaluation After Corneal Refractive Surgery

PURPOSE

To study the utility of measurements of contrast sensitivity at different spatial frequencies as an index of visual recovery following refractive surgery.

METHODS

Contrast sensitivity at 1.5, 3, 6, 12, and 18 c/deg was measured with the Stereo Optical FACT chart in 20 patients after photorefractive keratectomy (PRK) using the Nidek EC-5000 excimer laser system, and in 18 patients following laser in situ keratomileusis (LASIK). Contrast sensitivity was measured preoperatively and 1, 3, 6, and 12 months after surgery.

RESULTS

Results showed a statistically significant reduction (P<.01) in contrast sensitivity at all spatial frequencies in PRK patients during the first and third month, but contrast sensitivity recovered to preoperative values by 6 months after surgery (P>.1). In LASIK patients, decreased contrast sensitivity values 1 month after surgery were also obtained at all spatial frequencies. After 3 months, contrast sensitivity at 1.5 and 3 c/deg had recovered and did not differ significantly from preoperative values (P>.1), although contrast sensitivity at other frequencies remained reduced (P<.01). At 6 and 12 months, contrast sensitivity at all spatial frequencies did not differ from that obtained preoperatively (P>.1).

CONCLUSIONS

Contrast sensitivity measurements at 6 and 12 c/deg appear to be most useful in the assessment of patients who have undergone laser refractive surgery because defocus and optical aberrations primarily affect the higher spatial frequencies.