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Show Journal of Neuro- Ophthalmology 21( 3): 199- 204, 2001. © 2001 Lippincott Williams & Wilkins, Inc., Philadelphia Original Contribution Symptomatic Corneal Topographic Change Induced by Reading in Downgaze Karl C. Golnik, MD, and Eric Eggenberger, DO Objective: To elucidate the cause of monocular blur or diplopia after reading in downgaze. Methods: Corneal topography was obtained before and after a 15- to 30- minute reading effort in downgaze in three symptomatic patients and in nine asymptomatic control subjects. Results: Changes in corneal topographic color maps, corneal uniformity index, and predicted corneal acuity were found in the symptomatic patients but not in the control subjects before and after reading. Conclusion: Changes in corneal topography can occur after prolonged reading in downgaze and may produce symptoms of blur or monocular diplopia. Key Words: Monocular diplopia- Corneal topography. Monocular blurring or monocular diplopia after prolonged reading has been reported ( 1- 6). Changes in corneal regularity induced by eyelid position or a combination of eyelid position and corneal drying are thought to cause these symptoms. We report three patients who were referred for neuro- ophthalmologic evaluation of blurred vision that occurred only after prolonged reading in downgaze. Transient changes in corneal topography after reading were documented in each patient. PATIENTS AND METHODS Three patients were referred for neuro- ophthalmologic evaluation ( patients 1 and 2 to The Cincinnati Eye Insti- Manuscript received April 24, 2001; accepted June 25, 2001. Presented in part at the North American Neuro- ophthalmology Meeting, Mont Tremblant, Quebec, Canada, March 2000 and in total at the American Academy of Ophthalmology Annual Meeting, Dallas, TX, October 2000. From the Department of Ophthalmology, University of Cincinnati and The Cincinnati Eye Institute, Cincinnati, Ohio ( KCG); and the Department Neurology and Ophthalmology, Michigan State University, East Lansing, Michigan ( EE). Address correspondence to Karl C. Golnik, MD, 10494 Montgomery Rd., Cincinnati, OH 45242. E- mail: kgolnik. cwest@ worldnet. att. net ( no reprints are available). tute, patient 3 to Michigan State University) with unexplained monocular blurred vision after reading. Their case histories are detailed here. Nine asymptomatic employees with normal ophthalmologic examinations served as controls. The control group ranged in age from 23 to 55 years ( mean, 38); four were presbyopic. Patients and controls had complete eye examinations including corneal topography ( unmasked). The EyeSys Premier Version 4.2 ( EyeSys Technologies, Houston, TX) with the Holladay diagnostic summary was used for each participant except patient 3, who was evaluated with a Computed Anatomy Topographic Modeling System 1 ( Tomey). Topography was obtained before and after 30 minutes of reading in downgaze. Presbyopes read through their bifocals and nonpresbyopes were instructed to hold the reading material at a 45- degree downward angle. Measurements of central corneal regularity, corneal uniformity ( CU) index, and predicted corneal ( PC) acuity ( Holladay Diagnostic Summary, EyeSys Technologies) were compared for each subject before and after reading. The CU index is a measure ( expressed as a percentage) of the uniformity of distortion of the corneal surface within the 3- mm pupil. Thus, a CU index of 100% indicates that the cornea is perfectly uniform over the central 3 mm. The PC acuity provides a Snellen acuity of the optical quality of the central 3- mm corneal surface. Patient 3 also underwent corneal topography before and after reading in primary position. Institutional ( Cincinnati Eye Institute) Review Board Ethics Committee approval was obtained. Formal statistical analysis was not applied because of the small number of symptomatic eyes. CASE REPORTS Patient 1 A 47- year- old woman was referred for evaluation of visual distortion and monocular ghosting of images that occurred OD at distance and near after reading through her bifocals for 20 to 30 minutes. These symptoms would 199 200 K. C. GOLNIK AND E. EGGENBERGER FIG. 1. EyeSys topography of patient 1 before ( upper left) and after ( lower left) reading. The difference map between before and after reading is shown on the right. Note the different dioptric scale ( far right) for the difference map indicating diopters of change after compared with before reading. resolve 30 to 60 minutes after she stopped reading. She was otherwise asymptomatic and healthy except for a childhood seizure disorder. Visual acuity was 20/ 20 OU at distance and near with - 0.50 OU and + 1.50 add OU. Examination was normal; no corneal or eyelid abnormalities were noted, and eyelid position was symmetrical in primary position and downgaze. Corneal topography OD showed mild regular astigmatism before reading ( Fig. 1). CU index was 100% and predicted corneal acuity was 20/ 10. Thirty minutes after reading through her bifocals, symptoms occurred and topography had changed ( Fig. 1). CU index was 80% and PC acuity was 20/ 20. Symptoms resolved 60 minutes later, and topography returned to baseline. She obtained full- field reading glasses and read in a chin down position ( eyes in primary position). Symptoms have not recurred for 2 years. Patient 2 A 60- year- old woman noted blurred vision OS in viewing distant and near objects after reading for 20 47J » I "• I H i ^ r ™ , , * . , . « N 43 SO aoo minutes through her bifocals. She was healthy and taking no medications. Visual acuity was 20/ 20 OU at distance and near with - 2.25+ 0.50x90 OD and - 2.50+ 0.25x80 OS with + 1.75 add OU. Examination was otherwise normal; no corneal or eyelid abnormalities were noted. Corneal topography showed minimal regular astigmatism OS ( Fig. 2). CU index was 100% and PC acuity was 20/ 16. Thirty minutes after reading, topography had changed OS ( Fig. 2). CU index had decreased to 80% and PC acuity was 20/ 25. Symptoms ceased after she obtained full- field reading glasses and read in primary position. Patient 3 A 71- year- old man complained of blurred vision OS at distance and near after reading for 5 to 10 minutes. He had Cogan's corneal dystrophy OU and had undergone uneventful cataract extraction more than 1 year before presentation. Visual acuity was 20/ 40 OD and 20/ 25 OS at distance and near. Other than pseudophakia and Cogan's dystrophy, the examination was normal. Cor-m i m 0.90 0J00 4£ 0 • IjW IJW • 4M -:* • l : e : ; FIG. 2. EyeSys topography of patient 2 before ( upper left) and after ( lower left) reading. The difference map between before and after reading is shown on the right. Note the different dioptric scale ( far right) for the difference map indicating diopters of change after compared with before reading. / Neuro- Ophthalmol, Vol. 21, No. 3, 2001 CORNEAL TOPOGRAPHIC CHANGE FROM READING IN DOWNGAZE 201 - -- % 1& 3E « UUST « L£ t . r:_- '. 2. X. • K JC II. H - - I. a. DQ _ 0D : - CfiMfMHl frUlUj Inc. ] S ADJUSTABLE ti,: I- • ii= TTTI OP FIG. 3. Computed anatomy topography of patient 3 before ( A) and after ( B) reading in downgaze. Note the lack of change in the asymptomatic OD. " o*& r*^ zrjpam r- r " T ^ " neal topography OS showed regular astigmatism before reading which increased after reading for 15 minutes through his bifocals in downgaze ( Fig. 3). Topography did not change significantly after reading in primary position for 15 minutes ( Fig. 4). Symptoms did not recur after switching to single- vision reading glasses and adopting a chin- down position. RESULTS Table 1 summarizes the central corneal regularity data for patients and controls. Patients were more likely to develop a worsening CU index and PC acuity than controls after 30 minutes of reading in downgaze. Corneal topographic difference maps best illustrated the changes in topography occurring before and after reading. Topographic difference maps compare two topography measurements in time. A difference map was generated by subtracting the corneal curvature at corresponding corneal points obtained before and after reading. Identical topography before and after reading would result in a TABLE 1. Corneal Topographic Data Before and After Reading Patient # 1 2 3* Control group mean ( SD) range Cornea Before 100 100 97 ( 4.6) 90- 100 uniformity index After Change 80 20 80 20 95 2 ( 7.8) ( 5.5) 80- 100 - 10-+ 10 Before 20/ 10 20/ 16 20/ 14 20/ 10- 20/ 20 Predicted corneal After 20/ 20 20/ 25 20/ 16 20/ 10- 20/ 25 acuity Lines worse 3 2 0.4 ( 0.9) - 2-+ 1 SD- standard deviation * Patient 3 was tested on a different topography machine which did not have these data available. J Neuro- Ophthalmol, Vol. 21, No. 3, 2001 202 K. C. GOLNIK AND E. EGGENBERGER " OS" c- i'is-' ce- i A„ D_ JU_ S. T, A, B„ LE- IJ^ " Q* g Lj; s:- i 02/ LB/ OO 3.! ELO 58.5 r: r 15. Q P . ! • Si. 3 « , 5 - : < -, 3S. 5C " ' X 5.5C & a l^ « cf_-* d fl-- asa « y C^ c^ £. 3- 1= I: E= S- 3 :-: is :: ADJUSTABLE m : o= 54-+ FIG. 4. Computed anatomy topography of patient 3 before ( A) and after ( B) reading in primary position. The patient did not develop symptoms while reading in primary position. Note the lack of change in topography OS before and after reading. £ aapL3* c ^ pjluy Jnc -"•^^ 2- • ^ ^ r" ^ ^ ^ - = .. l^ a^ k' - 4B ^ ^ -- =: - - 3U » I 3.00 1 i . K f. 00 \= C 1.00 050 o. w - Q. 50 1 - 1.0* 1 ~ 1 J D § £. 00 I- : so P o. ool o s o | FIG. 5. Control group EyeSys topographic difference maps comparing before and after reading ( right eyes shown). Control group difference maps show a maximum of 1.50- diopter change centrally, whereas the symptomatic subjects had 2.50 diopters. / Neuro- Ophthalmol, Vol. 21, No. 3, 2001 CORNEAL TOPOGRAPHIC CHANGE FROM READING IN DOWNGAZE 203 difference map with a uniform color where each point was zero diopters. A large change over time would result in a multicolored map reflecting a variety of dioptric changes. Qualitatively, the corneal topography difference maps showed more changes after reading in the three patients than they did in the control subjects ( Fig. 5). DISCUSSION Our three patients presented with transiently blurred vision and/ or monocular diplopia with distance and near viewing that only occurred after reading. Each patient read through bifocals and therefore in downgaze. The symptoms resolved 30 to 60 minutes after cessation of reading. Corneal topography changed after the reading effort in downgaze in each patient. No change occurred after reading in primary position in patient 3. ( Patients 1 and 2 were not tested after reading in primary position.) Measurements of central corneal regularity ( CU index, PC acuity) worsened after reading in downgaze in each patient tested. Symptoms ceased after they switched to a separate pair of full- field reading glasses, which allowed reading in primary position. We concluded that the blurred vision and monocular diplopia were attributable to corneal surface changes induced by prolonged downgaze. Monocular diplopia usually results from optical irregularities. It is typically described as a ghosting or overlap of images rather than two separate images. The images are usually vertically or obliquely superimposed. Monocular diplopia from optical irregularities should improve with use of the pinhole. The retinoscopic reflex will usually be abnormal. Fincham ( 7) found that physiologic monocular diplopia could be demonstrated by 43% of his asymptomatic subjects under the right viewing conditions. He attributed this phenomenon to refractive index differences of the lens substance. Symptomatic monocular diplopia can occur from uncorrected refractive error ( 8), especially corneal or lenticular astigmatism, lenticular irregularities such as fluid clefts and mild cataract ( 9), extrapupillary aperture ( 10), as well as corneal irregularity induced by chalazion ( 11), eyelid position ( 12), or excimer laser surgery ( 13). Nonoptical causes of monocular diplopia are rare and include choroidal neovascularization ( 14), cystoid macular edema, epiretinal membrane, anomalous retinal correspondence ( 15), and occipitoparietal lesions ( 16). Monocular diplopia or blurred vision after reading in downgaze was previously described ( 1- 6). Mandell ( 1) reported a 20- year- old college student who developed monocular blur and double vision after reading for 1 hour. Distortion of keratometer mire image and changes in retinoscopy reflex were noted when symptoms occurred. Knoll ( 2) reported his own bilateral monocular diplopia that developed after reading. His symptoms could be prevented by supporting his upper eyelids with his thumbs while reading. He did not develop diplopia in the eye he had occluded while reading. Bowman et al. ( 3) found photokeratographic changes in a patient with monocular diplopia after reading. Kommerell ( 4) reported 20 patients with monocular diplopia that he believed was attributable to lid pressure. Details of the patient symptoms are only given for one patient who developed these symptoms after reading. The author suggested that eyelid pressure caused a corneal prismatic effect. Ford et al. ( 6) reported six patients with either monocular diplopia or fuzzy vision after reading and compared them with 20 asymptomatic controls. Based on videokeratoscopy, red reflex, and interpalpebral fissure width measurements, statistically significant differences in corneal flattening, steepening, surface regularity, and surface asymmetry were found between symptomatic subjects and controls after reading. These authors attributed the changes to lid position and drying of the cornea. Because we did not use the same topography machine or software as Ford et al. ( 6), our data are not directly comparable. However, measures of change in central corneal contour and regularity in symptomatic individuals were different from controls in both studies. Ford et al. ( 6) also measured interpalpebral fissures in primary position and downgaze. They found a narrower fissure in the subject group than in the control group. The position of the normal eyelid has been shown to affect corneal topography ( 17). Changes in topography have been reported before and after surgery for both congenital and acquired ptosis ( 18- 22). Carney et al. ( 5) studied nine asymptomatic subjects before and after a 15- minute forced eyelid closure. Five subjects developed monocular diplopia, and each had changes in corneal topography. Other forces acting on the eye might affect corneal shape. Refractive error and corneal topographic changes have been reported after strabismus surgery ( 23- 25). Nardi et al. ( 25) found that 6% of their patients had a more than 1- diopter change in astigmatism 30 days after surgery. Each of our patients had immediate and persistent resolution of symptoms after obtaining reading glasses that did not require near work in downgaze. Thus, the symptoms must be related to the position of the eye as opposed to the act of accommodation. Presumably forces produced by the eyelid or the extraocular muscles on the cornea resulted in these transient, symptomatic corneal topographic changes. REFERENCES 1. Mandell RB. Bilateral monocular diplopia following near work. Am J Optom Arch Am Acad Optom 1966; 43: 500- 4. 2. Knoll HA. Bilateral monocular diplopia after near work. Am J Optom Physiol Optics 1975; 52: 139^ 10. 3. Bowman KJ, Smith G, Carney LG. Corneal topography and monocular diplopia following near work. 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