Slit Lamp Beam Research Articles

Peripheral-to-central ratio of Guttae: validity and reliability of an objective method to characterize severity of Fuchs endothelial corneal dystrophy.

Common methods of measuring severity of Fuchs endothelial corneal dystrophy (FECD) are limited in objectivity, reliability, or start with a variable baseline that prevents distinguishing healthy from affected eyes. The aim of this study was to describe a method of grading FECD that overcomes these limitations. Fifteen patients with Fuchs endothelial corneal dystrophy were included in the study. Guttae were imaged with a slit lamp beam 8mm tall; the bottom 4mm half of each image was divided into two equally-sized sections. Guttae were counted by four independent graders blinded to disease severity scores. The peripheral:central guttae ratio was compared to modified Krachmer clinical severity scores. The peripheral:central guttae ratio was compared between mild (severity 0.5-3) versus moderate-to-severe (severity 4-5) disease. Receiver operating characteristics defined optimal ratio cutoffs for mild versus moderate-to-severe disease. Increased peripheral guttae and peripheral:central guttae ratio correlated with Krachmer severity (p = 0.021 and p = 0.009, respectively). The difference between mild and moderate-to-severe cases for the peripheral:central guttae ratio was significant (p < 0.001). Inter-rater reliability of total guttae count was high (coefficient = 0.82, p < 0.001). A peripheral:central guttae ratio of 0.16 was the ideal cut-off point (area under the curve = 0.79, sensitivity = 0.78, and specificity = 0.80). In this pilot study, the peripheral:central ratio of guttae correlates with subjective clinical severity of Fuchs dystrophy. It starts at a common baseline, has good inter-rater reliability, does not require dilation, and can be conducted with a smartphone and slit-lamp.

Correlation between ocular sun exposure and pterygium: A hospital-based study

Background: The term “pterygium” comes from the Greek word “Pterygos,” which means “wing.” The major predisposing factors are the hot and dry climate and long periods of ultraviolet light exposure. Epidemiological studies have revealed that the prevalence of pterygium is inversely related to latitude, and that it is greater among outdoor workers than indoor workers. Although sun exposure has been accepted as a risk factor for pterygium, there is no objective diagnostic tool to measure the total amount of sun exposure of an individual. Materials and Methods: This is a prospective study carried out for a period of 1 year on 100 eyes with pterygium. Demographic variables including age, sex, residence, education, income, smoking, alcohol drinking, exercise, and especially sun exposure were collected from interviewing the patients as per the pro forma. Their occupation was categorized according to the fields of profession. A detailed eye examination which included slit-lamp examination, visual acuity, refractive status, and size of the pterygium was recorded. The size of the pterygium was measured in millimeters from its apex to the limbus using the slit-lamp beam. Pterygium was graded, depending on the extent of the corneal involvement, and all the patients were divided into five grades (Grades I to V). Results: Out of 100 pterygia, 89' were located nasally, whereas only 11' were temporal. Nearly 84' of the total pterygia were found in unilateral eyes, whereas only 16' were seen in bilateral eyes. The male-to-female ratio was 1.8' (65 males: 35 females). Nearly 35' of the pterygia were seen in middle-aged males (41–60 years), followed by 20' in 21–40 years' age group. Grade III pterygium was seen in 15' of male patients in 41–60 years' age group, whereas only 8' were seen in the same age group in females. Maximum number of patients having pterygium 10' (Group B) and 15' (Group C) showed a maximum duration of daylight exposure of 8 and 10 h, respectively. Conclusion: This study shows that outdoor work and sunlight exposure are positively associated with the development of pterygium. Besides sun exposure, other factors which favor pterygium formation such as dusty environment, smoking, and genetics should also be taken into consideration, and further research should be done to ascertain their role in pterygium formation. Public education should focus on encouraging people to take appropriate protective measures, such as wearing sunglasses and brimmed hats when outdoors, and to avoid unnecessary sunlight exposure.

Scleral lens fitting and assessment strategies.

To describe prescriber reported scleral lens fitting and assessment strategies. The SCOPE (Scleral Lenses in Current Ophthalmic Practice Evaluation) study group designed and administered an IRB approved, electronic survey (REDCap) regarding current scleral lens fitting and assessment methods. The survey was distributed to attendees of the 2017 Global Specialty Lens Symposium. 95 practitioners responded to the survey. Over half of the respondents, 58% (55/95) reported fitting scleral lenses for less than five years (new prescribers), and 42% (40/95) reported fitting scleral lenses for more than five years (experienced prescribers). There was a statistically significant difference between their initial use of technology (χ2 = 21.117, p < 0.0005) in selection of a diagnostic lens. New prescribers consider base curve first (60%, 33/55), while experienced prescribers considered sagittal depth first (63%, 25/40) in their initial scleral lens selection. All of the experienced lens prescribers (100%, 39/39) reported estimating central clearance by comparing thickness of the post-lens tear reservoir to scleral lens thickness using a slit lamp beam at least some of the time, and 62% of new scleral lens prescribers (34/55; χ2 = 19.175, p < 0.0005) reported doing so. All (100%, 40/40) experienced prescribers schedule scleral lens follow-ups at a specific time and assess conjunctival compression (100%, 40/40), conjunctival staining (100%, 39/39), and corneal staining (100%,40/40) after lens removal. Practitioners with varying backgrounds and experience have added sclerals to their lens inventories. However, definite guidelines for fitting have not been developed. The results of a survey are provided; demonstrating that among practitioners with greater than 5 years of scleral lens experience, a consensus has emerged for best practices. Strategies for lens evaluation, which may inform future efforts at generating scleral fitting standards are described.

‘Van Herick Plus’: a modified grading scheme for the assessment of peripheral anterior chamber depth and angle

AimTo evaluate the accuracy of a new, modified grading scheme involving a short vertical slit beam, at the inferior angle for peripheral anterior chamber depth (PAC) and angle estimation and...

Long Anterior Lens Zonules and Intraocular Pressure.

PurposeTo investigate the relation between intraocular pressure (IOP) and the idiopathic long anterior zonule (LAZ) trait.MethodsPatients presenting for primary eye care were examined for LAZ, identified as radially oriented zonular fibers with central extension >1.0 mm beyond the normal anterior lens insertion zone (estimated via slit lamp beam length). Ocular, systemic health, and lifestyle data were collected via comprehensive exam and questionnaire. Multivariate regression was used to assess the relationship between IOP (Goldmann) and LAZ.ResultsThere were 2169 non-LAZ and 129 LAZ subjects (mean age: 49.8 ± 15.0 vs. 62.6 ± 10.2 years; 63.6% vs. 76.0% female; 83.2% vs. 91.5% African American). Right eyes with >trace LAZ (n = 59 of 110) had higher unadjusted mean IOP than control eyes (16.4 ± 3.3 vs. 15.0 ± 3.3 mm Hg, P = 0.005), and with control for numerous factors, LAZ eyes had an average IOP of approximately 1.3 ± 0.4 mm Hg higher (P = 0.003) than non-LAZ eyes. Final model covariates included sex (P = 0.001); spherical-equivalent refractive error (D; P < 0.0001); body mass index (kg/m2; P < 0.001); presence of diabetes (P < 0.001); having >high school education (P < 0.001); systolic blood pressure (mm Hg; P < 0.0001); being an ever smoker (P = 0.006); and having history of any site cancer (P = 0.01).ConclusionsThe LAZ trait, with potential prevalence near 2%, was associated with a higher IOP. This observation is consistent with the hypothesis that the trait is a marker for underlying mechanisms that elevate glaucoma risk.

Comparison of Different Measurement Tools and Dimensional Parameters of Pterygium to Investigate its Impact on Refractive Indices and Ocular Aberrations

The aim of this study was to compare different measurement tools and parameters, including a new computer-assisted image processing technique for the quantitative analysis of the percentage of pterygium on the corneal surface, horizontal/vertical lengths obtained using slitlamp beam and surgical compass. A total of 21 pterygia of 17 patients were included in the study. The pterygia were measured by three different methods: a slitlamp beam, a surgical compass, and a new computer-assisted image processing method. Refractive indices and higher-order aberrations were analyzed in all cases. The new computer-assisted image processing technique revealed excellent intraclass correlation coefficients for intraobserver and interobserver reliability (0.999 and 0.995, respectively). However, horizontal and vertical lengths revealed more deviation between the measurements obtained with slitlamp beam and surgical compass. Although uncorrected visual acuity did not show any significant correlation between horizontal and vertical lengths of pterygia measured by either slitlamp beam or surgical compass, it was correlated with the digital pterygium ratio (rho, 0.462; P=0.035). All ocular aberration (total, higher-order, coma, trefoil, quatrefoil, spherical, and higher-order astigmatism) Root-mean-square values more strongly correlated with higher percentage values of pterygium that covers the cornea, measured by the new computer-assisted image processing technique. The percentage of pterygium covering the corneal surface seems to be more associated with the pterygium-related visual disturbances than with horizontal and vertical lengths measured by conventional techniques. Moreover, the new computer-assisted image processing technique can accurately and reliably measure the percentage extension of pterygium on cornea.

Slit lamp assessment of relative afferent pupillary defect

PurposeTo demonstrate the accuracy of slit lamp assessment of relative afferent pupillary defect (RAPD) in patients with asymetric optic neuropathy.Methods40 eyes of 20 patients with asymetric optic neuropathy and no obvious RAPD in swinging flashlight test were evaluated on slit lamp. The asymetric optic neuropathy was confirmed by fundus examination, retinal nerve fiber layer thikness on OCT, visual field examination, visual potentials and/or brain and orbit MRI.The horizontal pupillary diameter in the affected (or more affeted) eye was measured and compared to the horizontal pupillary diameter of the fellow eye using the width of the slit lamp beam. Both diameters were measured in millimeters and compared.ResultsThere was a quantified anisocoria and RAPD each time when asymetric optic neuropathy was present. In other words, with the same slit lamp beam width (the same light intensity) the affected (or more affected eye) had a larger pupillary horizontal diameter.ConclusionsSlit lamp assessment of RAPD is simpler, quicker and more accurate than standard assessment using swinging flashlight test especially when anisocoria is not obvious.

The revised newest IC³D classification of corneal dystrophies

This report suggests how corneal dystrophies (CDs) should be diagnosed at the slit lamp and specifies the new IC(3)D classification of CDs in 2015 which incorporates new information. IC(3)D reviewed all peer-reviewed articles on CDs 2008 to 6/2014. Corneal dystrophy templates and anatomic classifications were updated. To detect landmarks for correct classification of CDs, opacity patterns and opacity units are determined at the slit lamp. Opacity patterns are described as (1) horizontal extension, (2) vertical extension ("depth") and clarity of the (3) cornea in between. Horizontal extension is assessed using a broad beam, vertical extension using a bright, thin slit lamp beam in high magnification. For assessment of opacity units, examination using retroillumination with dilated pupil is indispensable! This is especially true for epithelial and endothelial CDs. With a better review of the cellular origin of CDs, a new anatomic classification is proposed: 1. epithelial and subepithelial; 2. epithelial-stromal transforming growth factor beta-induced (TGFBI); 3. stromal; 4. endothelial dystrophies. Epithelial recurrent erosion dystrophies include three epithelial dystrophies (Franceschetti CD, dystrophia Smolandiensis, and dystrophia Helsinglandica) and are differentiated against TGFBI dystrophies, also associated with recurrent epithelial erosion. The chromosome locus of Thiel-Behnke CD is only located on 5q31. The entity previously called Thiel-Behnke on chromosome 10q24 may be a unique corneal dystrophy. Congenital hereditary endothelial dystrophy (CHED, formerly CHED2) is an autosomal recessive disorder. The autosomal dominant inherited CHED (formerly CHED1) is insufficiently distinct to be a unique entity and most cases appear to be similar to other reported dystrophies, particularly posterior polymorphous corneal dystrophy (PPCD). The 2015 revision of IC(3)D classification includes an updated anatomic classification more accurately describing TGFBI dystrophies to affect multiple layers. Some entities, e.g., Grayson Wilbrandt, Meretoja syndrome, and CHED2 are removed. All authors and reviewers should adhere to this classification of CDs!

The impact of pterygium excision on corneal astigmatism.

To compare the corneal astigmatism before and after the excision of pterygium and also to determine the correlation of pterygium size with the postoperative corneal astigmatism. Cross-sectional interventional study. Eye Department, Combined Military Hospital, Abbottabad, from May 2011 to March 2012. Thirty patients underwent pterygium excision. Pre-operatively Snellen visual acuity, manifest refraction and slit lamp examination was done. The size of the pterygium was recorded in mm by projecting a horizontal slit lamp beam from the limbus to the apex. All the pterygium were equal to or greater than 2.5 mm. Keratometry was performed with an automated keratometer. Keratometric data was recorded pre-operatively and at 28 days postoperatively. Wilcoxon signed rank test was used for comparing the pre-operative and the postoperative corneal astigmatism. Spearman's rank order was calculated to observe correlation of pterygium size with the postoperative astigmatism. The median (mean rank) pre-operative astigmatism of 2.25 (15.50) reduced to a median (mean rank) postoperative astigmatism of 1.30 (14.96). This decrease in the postoperative astigmatism was statistically significant (p < 0.001). There was a statistically non-significant correlation between the postoperative astigmatism and the pterygium size (rs = -0.29, p = 0.12). Pterygium excision caused significant reduction in corneal astigmatism.

Clinical and experimental validation of a slit lamp modification to measure toric lens position

A simple novel slit lamp beam angular scale modification is described to allow more accurate measurement of toric contact and intraocular lens position. The modified slit lamp measuring technique was validated in both an experimental and a clinical setting, with two independent observers. The device was tested against a known reference source, and intraobserver variability in a clinical setting measuring toric intraocular lens (IOL) position was ascertained. In the experimental setting 80 paired observations were analysed. Mean variance was 0.19° (95% CI 0.01-0.37), with a typical measurement error of 0.49°. Intraobserver variation had variance of -0.03° (95% CI -0.2 to 0.15) with a typical error of 0.47°. Clinical assessment of toric IOL position was made in 21 eyes. For this group, intraobserver variation had variance of -0.1° (95% CI -0.281 to 0.62) with a typical error of 1.36°. Intraclass correlation coefficient for all measures was 1.0. This simple technique has sufficient precision to be valuable in the clinical setting where photographic techniques may not be available or practical.

Assessment of toric intraocular lens alignment by a refractive power/corneal analyzer system and slitlamp observation

To assess the validity of an internal optical path difference map of a refractive power/corneal analyzer system in determining the alignment of toric intraocular lenses (IOLs). Private practices, Spring Hill, Brisbane, and Chermside, Australia. This retrospective study comprised patients with more than 1.5 diopters of preexisting corneal astigmatism who had phacoemulsification and AcrySof toric IOL implantation. Preoperatively, the surgical eye was marked at the slitlamp microscope using a 4-point technique. The desired IOL orientation was marked with a Mendez marker based on the steep corneal axis. The toric IOL axis was measured 3 weeks postoperatively by rotating the slitlamp beam to align with the IOL axis indicator marks and using the Internal OPD Map on the Nidek OPD-Scan system. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, residual refractive sphere, and residual keratometric and refractive cylinders were also measured at 3 weeks. Postoperatively, the mean UDVA was 0.17 logMAR +/- 0.18 (SD) and the mean CDVA, -0.01 +/- 0.12 logMAR; 88.2% of eyes had a UDVA of 0.3 or better, and no eye lost lines of visual acuity. There was an 82.33% reduction in defocus equivalent and a 64.62% reduction in refractive cylinder. The mean IOL misalignment measured by slitlamp was 2.55 +/- 2.76 degrees and by the internal map, 2.65 +/- 1.98 degrees. The correlation between the 2 methods was highly significant (r = 0.99, P<.001). Both refractive power/corneal analyzer system and slitlamp observation were reliable and predictable methods of assessing IOL alignment. The 4-point preoperative marking technique yielded clinically acceptable, accurate toric IOL alignment.

External Lacrimal Punctum Grading: Reliability and Interobserver Variation

To test the reliability and interobserver variation of external lacrimal punctum (ELP) grading. In a population-based epidemiologic study, ELP was visually graded based on slit lamp examination (grade 0 to 5), as described previously. Grades 0, 1, and 2 are for closed or stenotic ELP and grade 3 is for normal ELP (subjective grades). Grades 4 and 5 are for larger than normal (slit) ELP measured in millimeters by slit lamp beam (objective grades). Upper and lower ELP were graded by an oculoplastic surgeon and a senior ophthalmology resident. Both observers were masked to the reading of the other. Both observers were familiar to the grading system for past few years, although the oculoplastic surgeon had more experience in this regard. Patients with previous periocular surgery, medial lid mass obscuring the ELP, anatomically distorted punctum, and subjects with grade 4 and 5 ELP (objective grades) were excluded. The intraclass correlation coefficient test was used for the statistical analysis. There were 632 eyes from 174 (55.10%) male and 142 (44.90%) female subjects. Subjects' ages ranged from 7 to 87 years (mean +/- SD = 54+/-17.56). The intraclass correlation coeficient test showed a positive and strong correlation between two observers for grading the upper (value=+0.87, 95% CI: 0.84 and 0.88, p=0.000) and lower (value=+0.91, 95% CI: 0.90 and 0.92, p=0.000) ELP. In general, the less experienced observer tended to overestimate both upper and lower ELP grading. Reliability of the new ELP grading makes it a recommendable option for use in the clinic and comparing reports on ELP pathologies.

Agreement Between Gonioscopy and Ultrasound Biomicroscopy in Detecting Iridotrabecular Apposition

To assess the agreement between findings obtained at dark-room gonioscopy and ultrasound biomicroscopy (UBM) in the diagnosis of iridotrabecular apposition in light and dark conditions. We enrolled patients with appositional angle closure at dark-room gonioscopy performed using a 1-mm slitlamp beam that did not cross the pupil. Ultrasound biomicroscopic images were acquired in normal room light and subsequently with all room lights off. Images were evaluated for the presence or absence of iris-cornea contact. The angle opening distance at 500 microm was calculated. Iridotrabecular apposition in at least 1 angle quadrant was demonstrated in all 18 eyes at dark-room gonioscopy, 17 eyes (94%) at dark-room UBM, and only 10 eyes (56%) at UBM in room light. Of 18 superior angles that were appositionally closed at dark-room gonioscopy, apposition was demonstrated on UBM images in 16 (89%) in a dark room but only 6 (33%) in room light. Angle opening distance was less during dark-room gonioscopy in all but the nasal quadrant. We found high agreement between gonioscopy and UBM when both are performed in a completely dark room. Our findings support the recommendation that, in routine clinical practice, gonioscopy be performed in a dark room to avoid misdiagnosis of treatable iridotrabecular apposition.

The measurement of pupil cycling time.

To assess the influence of pupil size on pupil cycling time (PCT), a measure which may be elongated in cases of neurological disease. Clinically, pupil "cycling" is produced by focusing a slit-lamp beam on the pupil margin. A rhythmic contraction and dilation of the pupil is produced, as changes in pupil size alternately prevent and allow the light beam to reach the retina. In this study, however, the light beam was controlled electronically so that cycling could be produced around different pupil sizes. Measurements of the variation of PCT with pupil size were taken from 22 young normal subjects. PCT was seen to depend upon pupil size, increasing monotonically but non-linearly as size increased. The wave-form of pupil cycling is typically sawtooth, contraction being much faster than dilation. There was considerable variation amongst subjects in the range of pupil sizes where pupil cycling could be elicited. The results point to the need for a standardised procedure for the measurement of cycling time, because differences in clinical conditions will themselves influence pupil size, as will other external variables such as ambient light level. The results also bring into question neurological explanations for increased PCT in those diseases where pupil size is affected, because normal subjects have PCTs well beyond the accepted limits of normality when their pupils are enlarged.

The society of thoracic surgeons database: A progress report

To assess the validity of an internal optical path difference map of a refractive power/corneal analyzer system in determining the alignment of toric intraocular lenses (IOLs).Private practices, Spring Hill, Brisbane, and Chermside, Australia.This retrospective study comprised patients with more than 1.5 diopters of preexisting corneal astigmatism who had phacoemulsification and AcrySof toric IOL implantation. Preoperatively, the surgical eye was marked at the slitlamp microscope using a 4-point technique. The desired IOL orientation was marked with a Mendez marker based on the steep corneal axis. The toric IOL axis was measured 3 weeks postoperatively by rotating the slitlamp beam to align with the IOL axis indicator marks and using the Internal OPD Map on the Nidek OPD-Scan system. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, residual refractive sphere, and residual keratometric and refractive cylinders were also measured at 3 weeks.Postoperatively, the mean UDVA was 0.17 logMAR ± 0.18 (SD) and the mean CDVA, −0.01 ± 0.12 logMAR; 88.2% of eyes had a UDVA of 0.3 or better, and no eye lost lines of visual acuity. There was an 82.33% reduction in defocus equivalent and a 64.62% reduction in refractive cylinder. The mean IOL misalignment measured by slitlamp was 2.55 ± 2.76 degrees and by the internal map, 2.65 ± 1.98 degrees. The correlation between the 2 methods was highly significant (r = 0.99, P<.001).Both refractive power/corneal analyzer system and slitlamp observation were reliable and predictable methods of assessing IOL alignment. The 4-point preoperative marking technique yielded clinically acceptable, accurate toric IOL alignment.No author has a financial or proprietary interest in any material or method mentioned.

Managing Anterior Chamber Cysticercosis by Viscoexpression: A New Surgical Technique

Cysticercosis in the anterior chamber is rarer than in other ocular sites and is usually associated with plastic iridocyclitis. 1,2 We report herein a case of a freefloating live cyst in the anterior chamber that we removed by viscoexpression, a technique not described previously to our knowledge for such situations. Report of a Case. A 26-year-old vegetarian presented with an opacity in his left eye of 4 months' duration. His visual acuity was 6/6 OU and his ocular motility was unrestricted. Biomicroscopy confirmed a translucent unblemished cyst that measured 3.5X2.5 mm ( Figure 1 ); the protruding scolex promptly retracted into the cyst, and the cyst itself undulated and moved away from the slit-lamp beam. There was no evidence of active or healed iridocyclitis. Results of the fundus examination (pupil not dilated) were unremarkable. Findings of neurological and systemic examinations were normal. Skull radiographs and a computed tomographic scan did not suggest

A comparison of three methods of measurement of toric soft lens orientation.

A group of five subjects were fitted with truncated toric soft lenses varying in minus cylinder power from 1 to 4 D in 1 D steps at axes of 90 and 180. After 15 min of lens wear, the location of the lens was measured by three techniques: the projected slitlamp photographic technique, measurement with a protractor graticule in the slitlamp eyepiece, and alignment of the slitlamp beam with markings on the lens. Analysis of the data by a four-level analysis of variance and a t-test showed no significant difference between the three methods of measuring the toric soft lens orientation.

Pupillary dysfunction in myasthenia gravis

The constriction-dilation cycles of pupils exposed to a stationary, discrete slit-lamp beam were significantly prolonged in 25 myasthenic patients (1,060.4 +/- 45.8 msec) undergoing therapy with steroids, anticholinesterases, or both, compared to normal controls (801.9 +/- 8.6 msec) or subjects receiving steroids for nonneurological disease (860.9 +/- 14.9 msec). The duration of myasthenia correlated with the slowing of the cycle time. Myasthenia gravis may affect ectodermally derived smooth muscle or the autonomic neuromuscular junction or both, and not be restricted to the well-demonstrated alterations of neuromuscular junction in striated muscle of mesodermal origin. Alternatively, prolonged pupillary cycles could be attributed to dysfunction of central pathways of the pupillary light reflex.

Edge-light pupil cycle time.

A thin slit-lamp beam illuminating the pupil margin produces clearly visible pupil oscillations. These oscillations can be timed with a stopwatch, thus producing a measurement of the "edge-light" pupil cycle time'. The pupil cycle time is remarkably stable in various testing situations and is repeatable within about +/- 3% over extended periods of time. Expected normal distribution and 95% confidence intervals are given in Table 3. When the iris muscles are normally innervated and responsive, the pupil cycle time is dependent on the speed of nerve conduction and the number and strength of optic nerve impulses. Only 5% of normal persons aged 12 to 50 years are expected to have a pupil cycle time in either eye longer than 954 ms or a difference in pupil cycle time between the two eyes longer than 70 ms.

Pupil Cycle Time in Optic Neuritis

A thin slit-lamp beam illuminating the pupil margin produced clearly visible pupil oscillations. These oscillations were timed with a stopwatch, thus producing a measurement of the "pupil cycle time". The pupil cycle time was remarkably stable in various testing situations and repeatable within +/- 3% over extended periods of time. When the iris muscles were normally innervated and responsive, the pupil cycle time was dependent on the speed of conduction and the number and strength of optic nerve impulses. Pupil cycle time can be measured in most persons with active or inactive optic neuritis. In the few patients whose light reflex is so poor that the pupil cycle time cannot be measured, the inability to induce cycling can itself be taken as a definite abnormality of the light reflex arc. Only 5% of normal persons 12 to 50 years of age are expected to have a pupil cycle time in either eye longer than 954 msec, or a difference in pupil cycle time between the two eyes longer than 70 msec. Pupil cycle time was significantly longer in patients with optic neuritis, with a P-value less than .001. The pupil cycle time is similar to visual evoked response latency time in that it can detect and quantitate subclinical defects in optic nerve conduction time. Pupil cycle time is objective and quantitative for each eye individually. It is a fast, simple, and reliable clinic test of optic nerve function.