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Entoptic Phenomena and Reproducibility Ofcorneal Striae

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Entoptic Phenomena and Reproducibility Ofcorneal Striae Br J Ophthalmol: first published as 10.1136/bjo.71.10.737 on 1 October 1987. Downloaded from British Journal of Ophthalmology, 1987, 71, 737-741 Entoptic phenomena and reproducibility of corneal striae following contact lens wear MURRAY H JOHNSON, C MONTAGUE RUBEN, AND DAVID M PERRIGIN From the Institutefor Contact Lens Research, University of Houston- University Park, 4901 Calhoun Road, Houston, Texas 77004, USA SUMMARY Vertical corneal striae distributed across the posterior cornea are one of the objective signs ofclinically unacceptable corneal swelling (>6%) resulting from contact lens wear. This study reports that corneal striae are repeatable both in configuration and location with different levels of hypoxia. In most instances entoptic phenomena result from the presence of these lines. The results suggest that the healthy, avascular, transparent cornea has certain localised areas in its anatomical structure which may give rise to bundles of collagen fibres being made visible objectively and subjectively during conditions of corneal swelling. Corneal striae is a term used to describe lines seen in vidual was strikingly similar. Furthermore, there was the corneal stroma of varied appearance, aetiology, intrasubject repeatability of striae with large inter- and pathology. Deep striae have been seen as a result subject variability of corneal striate lines. of trauma (penetrating wounds),' after intraocular In this paper we describe the repeatability and operations (striate keratitis),' in degenerative entoptic phenomena of corneal striae following con- changes of collagen such as keratoconus,' in tact lens wear and provide additional clues to its diabetes,' and in idiopathic6 corneal conditions. It is a aetiology. well known clinical observation that vertical striate http://bjo.bmj.com/ lines distributed across the posterior cornea are Material and methods caused by corneal oedema accompanying hydrogel (soft) lens wear.7" The vertical or near-vertical striate SUBJECTS lines, indicating the presence of 4 to 6% or more of The study involved 11 volunteers with an age range of corneal oedema,' are reversible on removal of the 23 to 36 years, consisting of nine males and two lens.' Striate keratopathy accompanies stromal swell- females. A second group of subjects seen after an ing of about 7 to 10% or more, and appears as deep interval of one year comprised five females and two on October 5, 2021 by guest. Protected copyright. folds in the endothelial mosaic/Descemet's mem- males, with an age range of 21 to 30 years. All were brane area.7' The stromal lines can best be viewed free of any eye pathology and none had previously against the dark background of the pupil with high worn contact lenses. light intensity from the slit-lamp biomicroscope by To verify the first series of observations a second using direct focal illumination.""' group of subjects similar to the first were studied. The The reproducibility and entoptic phenomena of experiment was to ascertain a qualitative finding and corneal striae were first noted by Johnson (reported not measure in any degree the striae. by Johnson and Ruben") while investigating stromal The illustrations (Figs. 1 and 2) are selected from oedema induced by soft gel lens wear.'2 The striae those taken from one subject. were induced by thick hydrogel lenses in normal adult corneae following three hours of wear in both CONTACT LENSES the open and closed eye conditions. Photographic To induce corneal swelling greater than 6%, thick records were made of the appearance of the striae by hydrogel lenses were worn by each subject. The retroillumination, and the similarity to the entoptic lenses used in this study were 38*6% water content phenomena as recorded in a drawing by the indi- hydrogels (Metrosoft II- polymacon) manufactured by Metrosoft Incorporated (Austin, Texas). Two Correspondence to Dr Murray H Johnson. lenses were used, each having a base curve of8 3 mm, 737 Br J Ophthalmol: first published as 10.1136/bjo.71.10.737 on 1 October 1987. Downloaded from 738 Murray HJohnson, C Montague Ruben, and David M Perrigin http://bjo.bmj.com/ Fig. 1 Corneal oedemaproduced by having thesubject weara O05 mm thick HEMA lensforthreehours (open eye). Cornea! striae arepresent. The inferior round area that appears elevated is a large dimple caused by a trapped air bubble between the lens and cornea. power of -2-00 D, total diameter of 13-5 mm, and An adapter that allowed photography through the on October 5, 2021 by guest. Protected copyright. thickness of 0-2 mm and 05 mm. The 0-2 mm thick optical system of a Haag-Streit model 900 slit-lamp lens was worn in the closed eye and the 0-5 mm thick was used for the project. The camera body was a lens was worn in the open eye for three hours to show Nikon FE with an all ground glass focusing screen. whether the striae were repeatable with different The camera body was mounted to the slit-lamp eye levels of hypoxia. piece with the adapter so that alignment and focusing were possible through the camera viewfinder. The PHOTOGRAPHY camera was set on the automatic mode for the To achieve good slit-lamp photography of the striate photography, and exposure time was thus deter- lines the pupils were widely dilated, so that a wide mined by the camera's built-in meter. area of the cornea could be photographed. The two The film used-was Kodak Ektachrome (ISO 160) methods used were direct focal illumination"' and balanced for tungsten illumination. retroillumination from the fundus. The retro- The linear magnification produced by this system illumination method utilised an intense vertical of photography was either 2-2x or 3-4x for all shots. parallelepiped beam, placed just inside the widely dilated pupil margin, thus illuminating the cornea by EXPERIMENTAL DESIGN AND PROCEDURE retroillumination from the fundus. The corneal swelling responses to the physiological Br J Ophthalmol: first published as 10.1136/bjo.71.10.737 on 1 October 1987. Downloaded from Entopticphenomena and reproducibility ofcorneal striaefollowing contact lens wear 739 http://bjo.bmj.com/ Fig. 2 Corneal oedemaproduced by havingsamesubjectas in Fig. 1 weara 0-2 mm thick HEMA lensforthree hours (closed eye). Cornealstrike arepresent. Note that the location and configuration ofthese lines are the same as in Fig. 1. stress of hypoxia created by the thick hydrogel lenses atic for completion of the three-hour period. The on October 5, 2021 by guest. Protected copyright. were determined by having each subject wear low drug was instilled at this time to ensure mydriasis, water contact lenses (38-6%) for three hours. because an earlier pilot study had shown that instilla- Three separate sessions of photography were held. tion of the drug prior to lens wear did not ensure During one the undisturbed cornea was photo- effective mydriasis after three hours. graphed, and during the second and third the cornea To enable entoptic observation of the striae the was photographed after (a) three hours of 0-5 mm illuminating arm of the slit-lamp was placed at an thick lens wear (open eye) and (b) three hours of 0-2 angle of 450 to 500 to the microscope with the beam mm thick lens wear (closed eye) respectively. intensity increased to its maximum. The subjects For the closed eye condition each subject wore a were then asked to describe the appearance of the Coverlet adhesive eye occluder (Elastoplast- striae lines and to remember their configurations. A Beiersdorf, Inc., Conn) over the eye with the contact careful slit-lamp examination of the cornea was then lens; it was positioned to eliminate any undue performed to determine the plane of the striae. pressure on the globe while the eye was kept closed. No more than one lens was worn in any one day. Results After two and one-half hours of wear the lenses were removed for pupillary dilatation. The lenses were Our results are photographically summarised in Figs. reinserted five minutes after instillation of a mydri- 1 and 2. We noted that the location and configura- Br J Ophthalmol: first published as 10.1136/bjo.71.10.737 on 1 October 1987. Downloaded from 740 Murray HJohnson, C Montague Ruben, and David M Perrigin tions of these lines were the same within each subject different configurations and locations of these lines but different between subjects. In most instances, but when carefully examined. The phenomenon of only when the beam intensity of the slit-lamp was entoptic visualisation of striae in contact lens wearers increased to its maximum, did subjects report reported by the patient should alert the clinician to entoptic imagery of the striae. On examination, the the possible cause of them, namely, corneal oedema. configuration of the striae matched that of the The reproducibility and entoptic phenomena of subjects' description. To the subject they appeared as corneal striate lines lead one to suggest that the long or short, thin, greyish lines traversing the healthy, avascular, transparent cornea has certain cornea. One subject might report three wavy lines or localised areas in its anatomical structure which are another five straight lines, but, while they varied susceptible, and therefore, may give rise to bundles between subjects, their configurations were always of collagen fibres being visible objectively and sub- the same within a subject. jectively during conditions of corneal swelling. The entoptic phenomenon appears to result from a scat- Discussion tering of light from these striate lines when the light beam is increased to its maximum intensity. Examples of entoptic phenomena of corneal origin Since the striae appear by slit-lamp visualisation to have been reported.""'6 These observations were of a be deep, the mechanism is thought to be due to laking 'groove pattern' formed by the superficial cornea or of fluid separating the collagen fibres.
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