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PubMed2004

Astigmatism after small-incision clear corneal cataract extraction and intraocular lens implantation in children.

PURPOSE: To investigate the magnitude of postoperative astigmatism in children having cataract extraction with intraocular lens (IOL) implantation through a 3.0 mm superior clear corneal incision. SETTING: Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, USA. METHODS: This retrospective chart review comprised all pediatric patients having cataract surgery with IOL implantation through a 3.0 mm clear corneal incision from 1997 to 2002. One hundred two eyes of 75 patients were included. All refractions were performed manually by an experienced pediatric ophthalmologist. RESULTS: The mean postoperative retinoscopic cylinder in all patients was 0.63 diopter (D) (range 0.0 to 4.50 D) at 1 month, 0.40 D (range 0.0 to 1.75 D) at 6 months, and 0.51 D (range 0.0 to 2.50 D) at 1 year. Patients aged 0 to 36 months at the time of surgery had a mean postoperative cylinder of 0.22 D at 1 month, 0.03 D at 6 months, and 0.21 D at 1 year. Patients between 36 months and 6 years of age at surgery had a mean refractive cylinder of 0.50 D, 0.38 D, and 0.75 D, respectively. Patients older than 6 years at surgery had a mean refractive cylinder of 0.94 D, 0.75 D, and 0.76 D, respectively. CONCLUSIONS: Small-incision clear corneal cataract extraction with IOL implantation in children led to minimal postoperative astigmatism that remained stable over time. Less astigmatism was observed in children having surgery before they were 36 months old.

Adolescent↗
PubMed2005

Intraoperative optical refractive biometry for intraocular lens power estimation without axial length and keratometry measurements.

PURPOSE: To correlate intraoperative aphakic autorefraction to conventional emmetropic intraocular lens (IOL) calculations and derive an empiric predictive model for IOL estimation based on optical refractive biometry without axial length and keratometry measurements. SETTING: Institutional Review Board of the University of Southern California, Los Angeles County General Hospital, Los Angeles, California, USA. METHODS: A pilot group of 22 eyes of 22 patients scheduled for cataract surgery were enrolled in a prospective trial. All patients had a standard preoperative workup with subsequent cataract extraction and IOL implantation according to conventional biometric measurements and IOL calculations. Intraoperative autorefractive retinoscopy was used to obtain aphakic autorefraction and to measure the aphakic spherical equivalent before lens implantation. A linear regression analysis was used to correlate the aphakic spherical equivalent to the final adjusted emmetropic IOL power to empirically derive a refractive formula for IOL calculation (optical refractive biometry method). A second validation series of 16 eyes was used in a head-to-head comparison between the optical refractive biometry and the conventional IOL formulas. A subset of 6 eyes from the validation series were post-refractive cases having subsequent cataract surgery. RESULTS: Intraoperative retinoscopic autorefraction was successfully obtained in all 22 patients in the pilot group and all 16 patients in the validation group. The spherical equivalent of the aphakic autorefraction correlated linearly with the final adjusted emmetropic IOL power (P<.0001, with adjusted r(2)=.9985). The relationship was sustained over an axial length range of 21.43 to 25.25 mm and an IOL power range of 12.0 to 25.5 diopters (D). In a subsequent validation series of 10 standard and 6 post-laser in situ keratomileusis (LASIK) cataract cases, the optical refractive biometry method proved to be a better predictive model for IOL estimation than conventional formulas; 83% of the LASIK eyes and 100% of the normal eyes were within +/-1.0 D of the final IOL power when aphakic autorefraction was used, compared with 67% of LASIK eyes and 100% of the normal eyes, using the conventional methodology. CONCLUSIONS: A new model for IOL power calculation was derived based on an optical refractive methodology that breaks away from the conventional art introduced by Fyodorov in the 1960s. A purely refractive algorithm is used to predict the power of the IOL at the time of surgery without the need for axial length and keratometry measurements. This method bypasses some limitations of conventional biometry and shows promise in the post-refractive cataract cases.

Biometry↗
PubMed2006

Optical aberrations in the mouse eye.

PURPOSE: The mouse eye is a widely used model for retinal disease and has potential to become a model for myopia. Studies of retinal disease will benefit from imaging the fundus in vivo. Experimental models of myopia often rely on manipulation of the visual experience. In both cases, knowledge of the optical quality of the eye, and in particular, the retinal image quality degradation imposed by the ocular aberrations is essential. In this study, we measured the ocular aberrations in the wild type mouse. METHODS: Twelve eyes from six four-week old black C57BL/6 wild type mice were studied. Measurements were done on awake animals, one being also measured under anesthesia for comparative purposes. Ocular aberrations were measured using a custom-built Hartmann-Shack system (using 680-nm illumination). Wave aberrations are reported up to fourth order Zernike polynomials. Spherical equivalent and astigmatism were obtained from the 2nd order Zernike terms. Modulation Transfer Functions (MTF) were estimated for the best focus, and through-focus, to estimate depth-of-focus. All reported data were for 1.5-mm pupils. RESULTS: Hartmann-Shack refractions were consistently hyperopic (10.12+/-1.41 D, mean and standard deviation) and astigmatism was present in many of the eyes (3.64+/-3.70 D, on average). Spherical aberration was positive in all eyes (0.15+/-0.07 microm) and coma terms RMS were significantly high compared to other Zernike terms (0.10+/-0.03 microm). MTFs estimated from wave aberrations show a modulation of 0.4 at 2c/deg, for best focus (and 0.15 without cancelling the measured defocus). For that spatial frequency, depth-of-focus estimated from through-focus modulation data using the Rayleigh criterion was 6D. Aberrations in the eye of one anesthetized mouse were higher than in the same eye of the awake animal. CONCLUSIONS: Hyperopic refractions in the mouse eye are consistent with previous retinoscopic data. The optics of the mouse eye is far from being diffraction-limited at 1.5-mm pupil, with significant amounts of spherical aberration and coma. However, estimates of MTFs from wave aberrations are higher than previously reported using a double-pass technique, resulting in smaller depth-of-field predictions. Despite the large degradation imposed by the aberrations these are lower than the amount of aberrations typically corrected by available correction techniques (i.e., adaptive optics). On the other hand, aberrations do not seem to be the limiting factor in the mouse spatial resolution. While the mouse optics are much more degraded than in other experimental models of myopia, its tolerance to large amounts of defocus does not seem to be determined entirely by the ocular aberrations.

Animals↗
PubMed1979

Physiology of monocular aphakia.

The refraction of the unilateral aphakic patient has been aided by recent improvements in the ophthalmometer. New techniques simplify retinoscopic assessment of the patient. Choice of the type of correction, ie, spectacle, contact lens, contact lens-spectacle combination, or intraocular lens, depends on several factors. One factor is image size difference in aphakic and phakic eyes, particularly if removal of a second cataract is not imminent and vision is good in both eyes. Simple approaches that allow approximate size correction and effective restoration of binocularity are described. The current status of correction of vision in unilateral aphakic infants and young children is also discussed.

Adult↗
PubMed1986

Photographic detection of amblyogenic factors.

Refractive errors were determined photographically in a group of infants and children and were compared to conventional cycloplegic retinoscopy. The refractor consisted of a mirror telephoto lens and strobe flash designed to mimic the action of a retinoscope. Significant amblyogenic conditions such as anisometropia and high isoametropia were detectable. Strabismus and media opacities were also recordable. The technique provides a potential mass suited for infants.

Amblyopia↗
PubMed1989

Subjective and objective findings after radial keratotomy.

Monocular diplopia secondary to radial keratotomy was investigated in a 42-year-old ophthalmologist. Under certain conditions, the patient observed a ghost image, loss of contrast, and variability in the subjective refraction. The objective findings were scissoring of the retinoscopic reflex, a prominent iron line, and localized flattening of the cornea.

Adult↗
PubMed1993

A prototype erodible mask delivery system for the excimer laser.

PURPOSE: The authors developed an erodible mask delivery system for the argon-fluoride 193-nm excimer laser, which offers the possibility of correcting hyperopia and astigmatism as well as myopia. METHOD: Masks were made of polymethylmethacrylate on a quartz window, with intended corrections for myopia and hyperopia of 2.5 and 5 diopters (D). Ablations using the mask and control ablations using an expanding diaphragm were performed in 30 eyes of 15 pigmented rabbits with an Excimed UV200 laser (Summit Technology, Inc, Waltham, MA). The rabbits were followed for 134 days with regular biomicroscopy and retinoscopic examination by two observers. RESULTS: Ablations with the mask to correct myopia were successful and produced stable corrections, although the higher-power mask produced undercorrections. Hyperopic masks produced paradoxic myopic corrections, possibly due to the lack of a transition zone at the edge of the mask. Corneas ablated with the mask had less sub-epithelial haze than those ablated with the diaphragm at all examinations. Results of histopathologic examination showed epithelial hyperplasia over the ablation zone in all eyes. Dichlorotriazinyl aminofluorescein collagen staining showed subepithelial new collagen in all eyes, but there was no relation between the depth of ablation at any point on the cornea and the amount of new collagen deposited there. CONCLUSIONS: Myopic ablations are feasible with the erodible mask, although additional calibration is needed. Hyperopic ablations were unsuccessful with the current design. Corneas ablated with the mask may be clearer than corneas ablated with the diaphragm, possibly due to a smoother ablated surface. Regression of effect after laser ablation in the rabbit model is likely due more to epithelial hyperplasia than to stromal remodeling.

Animals↗
PubMed1996

Two infant vision screening programmes: prediction and prevention of strabismus and amblyopia from photo- and videorefractive screening.

Two infant vision screening programmes on total populations in the Cambridge Health District have been designed to identify manifest strabismus and strabismogenic and amblyogenic refractive errors at 7-9 months of age. The first, completed, programme used the isotropic photorefractor with cycloplegia together with a standard orthoptic examination. The second, current, programme uses the VRP-1 isotropic videorefractor to identify infants with accommodative lags which are followed up by refraction under cycloplegia. Both programmes show good agreement between infants identified at screening and retinoscopic refractions at follow-up, showing that photo- and videorefraction (with or without cycloplegia) can be effective methods for screening for ametropia in infants and young children. In each programme 5-6% of infants showed abnormal levels of hyperopia (> or = 3.5 D in any meridian), less than 1% showed anisometropia > or = 1.5 D; very few infants (0.25%) showed -3D myopia or greater. Less than 1% showed manifest strabismus. Hyperopic and anisometropic children entered a randomised controlled trial of partial refractive correction. All children identified at screening, alongside appropriate control groups, are extensively followed up to age 4 years. The first programme has found that children who were hyperopic in infancy were 13 times more likely to become strabismic, and 6 times more likely to show measurable acuity deficits by 4 years, compared with controls. Wearing a partial spectacle correction reduced these risk ratios to 4:1 and 2.5:1 respectively. The impaired acuity can be attributed, in part, to meridional amblyopia resulting from persisting astigmatism. Both hyperopic and myopic infants showed refractive changes in the direction of emmetropia between 9 months and 4 years. Wearing a partial spectacle correction did not affect this process of emmetropisation, but does provide the possibility of reducing the incidence of common pre-school vision problems.

Aging↗
PubMed1999

Per-operative retinoscopy as a predictor of final post-operative refraction.

PURPOSE: To assess the accuracy of streak retinoscopy performed at the end of cataract surgery as a predictor of final post-operative error. METHOD: Retinoscopy was performed on 68 patients as they lay on the operating table after routine cataract extraction and intraocular lens implantation. In each case the predicted post-operative refraction by biometry and the retinoscopy at the end of the operation were compared with the 6 week post-operative subjective refraction. RESULTS: The retinoscopy had a mean difference of 0.6 D (standard deviation of 0.5 D). The post-operative refraction predicted by biometric measurements had a mean difference of 1.6 D (standard deviation 0.6 D). When corrected for systematic error, 8% of patients were found to have an error of greater than 2 D as predicted by pre-operative biometry. Prediction by retinoscopy made no error greater than 2 D. The accuracy in the retinoscopic prediction of post-operative refraction was significantly better than the biometry using the F-test (p = 0.001). CONCLUSION: Retinoscopy at the end of cataract surgery may be a valuable tool to alert the surgeon to an unexpected refractive error. This would enable immediate intraocular lens exchange, if required.

Biometry↗
PubMed2001

[First results of implantation of a new, potentially accommodative posterior chamber intraocular lens].

PURPOSE: Conventional posterior chamber intraocular lenses (PCIOL) generally provide excellent visual acuity but do not restore accommodation. A new, potentially accommodative PCIOL has been designed after principles elaborated by K.D. Hanna using finite element models. However, before newly developed PCIOL may be implanted routinely in larger numbers of patients, careful and meticulous evaluation in clinical studies is necessary. Thus, it was the aim of this study to investigate intra- and early 3-month postoperative findings after implantation of the newly designed PCIOL. PATIENTS AND METHODS: In a prospective pilot and safety study that was approved by the ethics committee of our university, six eyes of six patients (2 males, 4 females, age range 54 to 87 years) with senile or presenile cataract underwent phacoemulsification and implantation of the new PCIOL by one surgeon between June and November 2000. The PCIOL (1 CU, HumanOptics AG, Erlangen, Germany) is a one-piece hydrophilic acrylic foldable lens with an optic diameter of 5.5 mm. Modified haptics are intended to allow anterior movement of the lens optic as a function of contraction of the ciliary muscle. Intra- and early postoperative findings obtained after one and two days, one, two and six weeks and 3 months postoperatively were documented prospectively. Postoperative examinations included recording of distance and near visual acuity both obtained with best distance correction, determination of subjective near point and measurement of distance and near refraction by streak retinoscopy. Follow-up was at least three months in all patients. RESULTS: Surgery was uncomplicated in all patients with successful in-the-bag implantation and good centration of the PCIOL. The postoperative course was uncomplicated without inflammation, hemorrhage, synechiae or decentration. Visual acuity improved in all patients according to the status of the macula with values between 20/200 (atrophic maculopathy) and 20/20. After three to six months we observed a difference between retinoscopic near and distance refraction of 0.625 to 1.875 D and subjective near points of 40 to 100 cm. Near visual acuity with distance correction ranged from 0.1 or J 16 (atrophic maculopathy) to 0.4 or J 7. CONCLUSIONS: These early and preliminary results of our small pilot study are encouraging. Our findings may indicate at least some degree of pseudophakic accommodation. However, further studies with additional methods of measurements, with longer follow-up, more patients and controlled studies with control groups are essential to further determine safety and potential accommodative power of this new PCIOL.

Accommodation, Ocular↗
PubMed2006

[How useful is the prescription of glasses in intermittent exotropia and decompensating exophoria?].

BACKGROUND: The aim of this study was to investigate the effect of full correction of the retinoscopic measurements done in cycloplegia in two groups of patients with intermittent exotropia (IE) and decompensating exophoria (DE), respectively. PATIENTS AND METHODS: 58 patients (n = 29 each of IE and DE) fulfilled the inclusion criteria: retinoscopy in cycloplegia, follow-up of at least 6 weeks, age more than 2.5 years and reliable visual acuity. Exclusion criteria were all forms of secondary and constant exotropia, A-V incomitance of high amount and eyes with amblyopia (visual acuity in far distance < 0.5). The age median of refractometry was not higher in patients with IE compared to those with DE: 7.4 (3.10; 47.8) vs. 7.3 (3.8; 40.11) years, p = 0.33. Glasses were prescribed in any case of myopia and astigmatism as well as in hyperopia of > + 0.5 dpt. RESULTS: Mean refraction of both eyes (mean value of spherical equivalent of both eyes) was higher for IE compared to DE: 0.7 +/- 1.8 (- 5.13; + 4.75) vs. 0.1 +/- 1.7 (- 5.25; + 2.5) dpt, p = 0.9. Visual acuity improved in both groups significantly: median of visual acuity in IE: 0.9 (0.3; 1.25) vs. 1.1 (0.5; 1.25), p = 0.02; in DE: 1.0 (0.4: 1.25) vs. 1.0 (0.6; 1.25), p = 0.03. Considering only patients aged over 7 years the difference stayed significant only in the group of DE: IE: median 1.0 (0.5; 1.25) to 1.0 (0.5; 1.25), p = 0.2; DE: median 1.0 (0.8; 1.25 to 1.0 (0.8; 1.25): visual acuity was nearly always 1.0 and better, p = 0.009. In hyperopic patients a significant improvement of visual acuity could be seen: in IE from median 0.9 (0.3; 1.25) to 1.1 (0.5; 1.25), p = 0.02 , in DE visual acuity: median 1.0 (0.4; 1.25) to 1.1 (0.6: 1.25), p = 0.02, as well as stereoacuity improved significantly: median 60 (30; 240)'' vs. 60 (15; 240)'', p = 0.03. In patients aged over 7 years the improvement was no longer significant in IE: p = 0.7, but stayed significant in DE: p = 0.03. There was no significant change of the angle deviation in both groups. CONCLUSIONS: According to the results of this study, full correction of refractive errors in IE and DE leads to an improvement of the visual acuity mainly due to correction of myopia and astigmatism, but not to a better compensation of the angle deviation.

Child, Preschool↗
PubMed1997

[Intraoperative skiascopy for determining the refractive value of an implantable intraocular lens].

BACKGROUND: Preoperative biometry for calculation of the refractive power of intraocular lenses is not sufficiently reliable in certain cases. Most frequently inaccuracies tend to occur in highly myopic eyes. Preceding refractive procedures can also impair IOL-calculation or even make it impossible. PATIENTS: In a highly myopic patient IOL-power calculation was not possible with conventional calculation formulas due to a preexisting refractive silicone lens located between the cataractuous natural lens and the iris. In another myopic patient ultrasound measurement of axial eye length produced variable and unreliable results. Therefore retinoscopy was performed intraoperatively in the aphakic eye. Refractive power of the IOL was calculated using a new formula. For validation of the method retinoscopy was performed intraoperatively in a second group of 11 patients with unproblematic ultrasound biometry. RESULTS: In 3 eyes IOL power was chosen according to intraoperative retinoscopy. A maximal deviation of 1.25 D from the aimed refraction resulted. In the second group, the retinoscopic method produced partially considerably inaccurate results as compared to the ultrasound biometry. Inaccuracies increased with the extent of hyperopia. CONCLUSIONS: In cases of difficult or inaccurate preoperative ultrasound biometry IOL power can be estimated after intraoperative retinoscopy in the aphacic highly myopic eye. IOL power can be calculated instantly using computer programs or tables. This method additionally enables the surgeon to control the refractive result of intraocular lens implantation prior to wound closure. However this method lacks reliability in higher hyperopic eyes, as in these cases small changes in corneal vertex distance of the lens used for retinoscopy highly alter the result.

Adult↗
PubMed1980

[Liindner's method of cylinder retinoscopy without theory].

Brief description of Lindner's cylinder retinoscopy for practical application: The main criteria of this accurate method for checking refraction are the direction, shape, speed and brightness of the retinoscopic phenomena moving in the pupil of the examined eye. To determine astigmatism the use of plus cylinders is recommended. Difficulties may be due to the optical aberration at the periphery of a wide pupil, to a scissors phenomenon, and to optical irregularities of the senile lens, corneal opacities etc. In many cases retinoscopy can be performed well without using mydriatics and cycloplegics, respectively. Children must not be overstrained. Generally, final subjective checking is crucial for the prescription of corrective glasses. Mastery of Lindner's cylinder retinoscopy enables the eye specialist to keep refractometry with simple aids, as an essential part of the ophthalmological diagnosis, in his own hands, against the increasing claim of optometrists and opticians.

Adult↗
PubMed1998

How accurate is the hand-held refractor Retinomax(R) in measuring cycloplegic refraction: a further evaluation.

AIMS To assess the agreement between the hand-held autorefractor Retinomax(R) and three different on-table autorefractors when measuring cycloplegic refraction in subjects with small and high ametropia. To assess the agreement between the cycloplegic refraction using the Retinomax(R) and by retinoscopy in children with small and high ametropia. METHODS Part A.276 subjects were refracted under cycloplegia using both the Retinomax(R) and an on-table infrared automated refractor (Topcon RM-A 6000, Nidek AR 800 or Nikon NR 5000). They were separated into subjects withsmall ametropia (mean sphere </= 3.5 D hyperopia, </= 3 D myopia) and high ametropia (mean sphere > 3.5 D hyperopia, > 3 D myopia). The agreement between both types of refractors regarding the different refractive components was assessed for the whole group and for the two subgroups of small and high ametropia. Part B. 48 infants were refracted under cycloplegia by retinoscopy and by the Retinomax(R). The agreement between both methods of refraction was analyzed in the same manner as in part A. RESULTS Part A. No significant bias was found between the two types of refractors with regard to the spherical equivalent. The 95% limits of agreement were +/- 1 D. Although no clinically significant bias was found with regard to the cylinder power in the 276 subjects, it was found that the 95% limits of agreement were much better (+/- 0.75 D) in small ametropia subjects than in high ametropia subjects (-2.1 to +1.3 D). No significant bias was found with regard to the axis determination. Part B. No significant bias was found between the Retinomax(R) and retinoscopic measurements with regard to the spherical equivalent. The 95% limits of agreement were -1.36 to +1.76 D. However, the mean difference for spheres and cylinders showed a positive bias and a negative bias, respectively, suggesting more positive spheres and larger cylinders when measured by the Retinomax(R) compared to retinoscopy. This was particularly obvious in cases of high ametropia. CONCLUSION Compared to retinoscopy and on-table autorefraction, the hand-held refractor Retinomax(R) is accurate in any ametropia with respect to the spherical equivalent. In small ametropia, there is a good accuracy when measuring the three refractive components (sphere, cylinder and axis). The accuracy decreases in high ametropia, especially with regard to the cylinder power.

Journal Article↗
PubMed1998

Detection system for ocular refractive error measurement.

An automatic and objective system for measuring ocular refractive errors (myopia, hyperopia and astigmatism) was developed. The system consists of projecting a light target (a ring), using a diode laser (lambda = 850 nm), at the fundus of the patient's eye. The light beams scattered from the retina are submitted to an optical system and are analysed with regard to their vergence by a CCD detector (matrix). This system uses the same basic principle for the projection of beams into the tested eye as some commercial refractors, but it is innovative regarding the ring-shaped measuring target for the projection system and the detection system where a matrix detector provides a wider range of measurement and a less complex system for the optical alignment. Also a dedicated electronic circuit was not necessary for treating the electronic signals from the detector (as the usual refractors do); instead a commercial frame grabber was used and software based on the heuristic search technique was developed. All the guiding equations that describe the system as well as the image processing procedure are presented in detail. Measurements in model eyes and in human eyes are in good agreement with retinoscopic measurements and they are also as precise as these kinds of measurements require (0.125D and 5 degrees).

Astigmatism↗
PubMed1992

Early plasmapheresis in patients with thrombotic thrombocytopenic purpura.

OBJECTIVES: To investigate the relationship of thrombotic thrombocytopenic purpura to adult respiratory distress syndrome (ARDS) and study the responses of thrombotic thrombocytopenic purpura patients to early plasmapheresis. DESIGN: Case series. SETTING: ICU of a university hospital. PATIENTS: Twenty-four consecutive patients with thrombotic thrombocytopenic purpura, with various periods of time (1 to 18 days) having elapsed since the onset of this condition. Patients ranged in age from 17 to 66 yrs. INTERVENTIONS: Plasmapheresis, using intermittent flow separators, was instituted soon after the patients' ICU admission. The retinoscopic findings on admission and the relationship of Pao2 to platelet counts before and after plasmapheresis therapy were recorded. Antiplatelet agents were given to the survivors to prevent relapses. MEASUREMENTS AND MAIN RESULTS: Eighteen patients survived and six died. Plasmapheresis was administered for a range of 1 to 5 days (mean 3) and 3 to 18 days (mean 9.8) in survivors and nonsurvivors, respectively (p less than .001). Four patients with confluent fundus hemorrhages died and seven without these fundoscopic findings had easily controlled disease. Increases in Pao2 paralleled increases in platelet counts after plasmapheresis (p less than .001) in this small series of patients. Three of 18 discharged survivors relapsed over a period of 3 to 56 months of follow-up. CONCLUSIONS: Early introduction of plasmapheresis in thrombotic thrombocytopenic purpura seems to increase the survival rate and to halt the development of ARDS. Fundus findings may be a prognostic factor in thrombotic thrombocytopenic purpura. The antiplatelet agents seem to be efficacious in the prevention of relapses.

Adolescent↗
PubMed1975

Luminance changes of the fundus reflex.

A recording retinoscope was developed to measure the luminance of the fundus reflex during problem-solving tasks. 10 students were used as subjects. The luminance of the reflex was recorded while the subjects read 5 passages of graded reading material and performed an addition task. A reversal design was used to determine the effects of pupil changes and accommodation on changes in the luminance of the reflex. Relatively large changes in the luminance of the reflex were recorded. These were due to accommodation. The subjects' comprehension of the reading material did not appear to affect the luminance of the reflex in the manner predicted by previous studies. However, a change in task from simple reading material to an addition task appeared to increase the luminance of the reflex.

Accommodation, Ocular↗