678 AMERICAN JOURNAL OF OPHTHALMOLOGY MAY, 1981

superficial lesions in the cornea of the left eye at the 10:30 and 2 o'clock positions in the midperiphery. The epithelium surrounding these lesions and in the area between the nodules demonstrated a fine sur­face irregularity that did not stain with fluorescein. Slit-lamp examination disclosed a light-brown pig-mented line like that found in the right eye. A vertical extension of the line ran nasally to the nodule at the 2 o'clock position (Figure, right). There was a filamentous plaque at the 11 o'clock position periph­erally in the left eye, but there was no corneal neovascularization. The remainder of the ocular examination gave normal findings.

D I S C U S S I O N

Salzmann's nodular degeneration is a relatively uncommon, noninflammatory corneal degeneration characterized by raised blue-white nodular corneal lesions that are often arranged in a circular distribution around the pupil. To the best of our knowledge, an associated pigment-ed corneal line in Salzmann's nodular degeneration has not been described previously.6"12

The pigmented line in our patient most closely resembled the Hudson-Stähli line in its coloration, horizontal course, and superficial location. Among the variations in the Hudson-Stähli line that we found in our case were branching, oblique orientation, and deviations around corne­al macular scars.13 However, its location in the superior one half of the cornea and its relationship to the raised nodular corneal lesion differentiated this line from the classic Hudson-Stähli line.

R E F E R E N C E S

1. Hudson, A. C : A note on certain peculiar pigmentary markings in the cornea. R. London Ophthalmic Hosp. Rep. 18:198, 1911.

2. Stähli, J. : Über den Fleischeraschen Ring beim Keratoconus und eine neue typische Epithelpigmen-tation der normalen Kornea. Klin. Monatsbl. Augen-heilkd. 60:721, 1918,

3. Fleischer, B.: Über Keratoconus and eigenar­tige Figurenbildung in der Cornea. M.M.W. 53:625, 1906.

4. Stocker, F. W.: Demonstrationen. Eine pig­mentierte Hornhautlinie bei Pterygium. Schweiz. Med. Wochenschr. 20:19, 1939.

5. Ferry, A. P. : A new iron line of the superficial

cornea. Occurrence in patients with filtering blebs. Arch. Ophthalmol. 79:142, 1968.

6. Katz, D.: Salzmann's nodular corneal dystro­phy. Report of a case. Arch. Ophthalmol. 4:16, 1930.

7. Brown, E. U. L., and Katz, D.: Salzmann's nodular comeal dystrophy. Its pathological process and a suggested therapy. Arch. Ophthalmol. 13:598, 1935.

8. Muir, E. B.: Salzmann's nodular corneal dys­trophy. Report of a case. Am. J. Ophthalmol. 23:138, 1940.

9. Wolff, P. G., cited by Gamble, R. C : Proceed­ings of the Chicago Ophthalmological Society, Feb. 16, 1948. Am. J. Ophthalmol. 32:709, 1949.

10. Katz, D. : Salzmann's nodular corneal dystro­phy. Acta Ophthalmol. 31:377, 1953.

11. Vannas, A., Hogan, M. J., and Wood, I.: Salzmann's nodular degeneration of the cornea. Am. J. Ophthalmol. 79:211, 1975.

12. Abbott, R. L., and Forster, R. K.: Superficial punctate keratitis of Thygeson associated with scar­ring and Salzmann's nodular degeneration. Am. J. Ophthalmol. 87:296, 1979.

13. Gass, J. D. M.: The iron lines of the superfi­cial cornea. Arch. Ophthalmol. 71:348, 1964.

A GONIOSCOPY LENS FOR PULSED-LASER

TRABECULOTOMY

C L I V E BERNARD W H E E L E R , D . S c , AND M A R T I N SAUNDERS BASS

London, England

We designed an indirect gonios-copy lens capable of handling the high powers generated by short-duration pulsed lasers. The lens is composed of an equilateral quartz prism within which the entire laser beam is internally

From the Department of Experimental Ophthal­mology, Institute of Ophthalmology, London, En­gland.

Reprint requests to Clive Bernard Wheeler, D.Sc, Department of Experimental Ophthalmology, Institute of Ophthalmology, Judd Street, London, WC1H 9QS, England.

VOL. 91, NO. 5 NOTES, CASES, INSTRUMENTS 679

reflected and connected to the cornea with saline solution. The reflected beam subsequently passes through the index-matched cornea to the trabecular region. Chromatic aberration is mini­mal because refraction is elimi­nated by arranging the laser beam so that it crosses the dielectric interfaces in a near-normal di­rection. The reflection losses amount to less than 5%, even with­out antireflection coatings. A prism of glass is sufficiently robust to handle the 100-kW pulses from a dye laser.

In recent years the continuous-wave argon laser has been successfully applied to the perforation of the trabeculum for the relief of open-angle glaucoma.1-e The laser beam is conducted to the target site with a conventional indirect gonioscopy lens designed for observation of the ante­rior chamber. Theoretical analysis7,8 indi­cates that the short-timescale pulsed laser should be more effective for perfora­tion since the target damage it produces is far more localized than that of the continuous-wave laser. Krasnov9'10 ver­ified this experimentally with a Q-switched ruby laser. However, the high power of the pulsed laser beam burns the reflective coatings of the conventional lens, and the optical pathways, formed from transparent plastic, tend to cavitate. Moreover, in our opinion, there is no satisfactory antireflection coating that has a long life when exposed to high-power pulsed radiation and to the clinical sterilization process required for such a lens. The lens described here* is pri­marily intended for use with the pulsed-dye laser system developed in this lab-

*A patent has been applied for.

oratory. This system, which incorpo­rates a modified slit-lamp, generates a 100-kW pulse and is currently used to perform iridotomies in a single applica­tion.11

MATERIAL AND METHODS

The necessary absence of plastic mate­rial and optical coatings implied that the reflection required within the indirect gonioscopy lens had to be at an optically dense-to-rare interface, such as that be­tween quartz and air. Because the lens was also likely to be used for diagnosis and color photography, it had to have minimal chromatic aberration. This con­sideration also influenced the precision of target location because our apparatus uses a colinear aiming beam, derived from a continuous-wave helium-neon laser, that is some 40 nm longer in wave­length than the operating beam of the dye laser. Refraction is minimal if all working light paths within the lens tra­verse the relevant dielectric interfaces in a near-normal direction. Finally, the design had to be such that the approach to the patient's eye was in the normal direction because our apparatus, used for routine clinical laser iridotomy, was adapted to this situation.

These three requirements were satis­fied by a simple arrangement of a single equilateral quartz prism connected to the eye by saline solution with the same refractive index as the cornea (Figure). The prism, which has 1.91-cm triangular sides and a height of 1.27 cm, is fitted into an acrylic plastic (Perspex) holder worked from a solid circular cylinder 2.90 cm in diameter. A recess for the prism is milled into the side of the cylinder with a 1.27-cm slot drill to a radial depth of 2.06 cm and to an axial length of 1.65 cm from the end face. The prism fits snugly into the recess with its

680 AMERICAN JOURNAL OF OPHTHALMOLOGY MAY, 1981

Figure (Wheeler and Bass). Schematic diagram of the gonioscopy lens.

rectangular face flush with the end face of the cylinder and with its apex on the bottom of the slot 0.36 cm from the axis of the cylinder. This is the optimum posi­tion of the reflecting plane that Becker12

recommended. Any excess acrylic plastic is removed by uniformly tapering the cylinder over an axial length of 2.06 cm into the frustum of a cone from a diame­ter of 2.90 cm at the end face to a diameter of 1.73 cm at the corneal face. The corneal cavity is formed by turning out the acrylic plastic over a diameter of 1.33 cm to a depth of 0.31 cm, leaving a ledge of acrylic plastic 0.10 cm thick on which the prism apex stands and a corne­al rim 0.20 cm thick. This rim is shaped to match the average corneoscleral limbus and highly polished so as not to scratch the cornea. The saline reservoir, which includes the corneal cavity, is completed by breaking through and removing part of the ledge with a Swiss file while retaining a ledge sufficient for the prism to act as a water-tight side to the reservoir. A hole to accommodate a hypodermic needle is drilled through the acrylic plas­tic from the front face to the reservoir in order to admit saline solution from a sy­ringe via a plastic pipe. Finally the prism

and needle are fixed in position with Araldite.

The energy losses by reflection are acceptable even in the absence of antire-flection coatings, amounting to 4% at the front face and 0.4% at the quartz-to-saline interface. This front-face reflection does not present a hazard to the surgeon because the associated laser equipment incorporates a safety shutter that oc­cludes his view when the laser is fired. The weaker reflection generates, by fur­ther reflection at the front face, a beam directed toward the eye with an intensity 2 X 10"4 times that of the primary beam. However, this reflected beam is colinear with the primary beam, even when the beam does not traverse the prism normal to its faces. In practice the lens is initially held horizontally and filled with saline solution. The patient's head is inclined horizontally and the lens applied to the corneoscleral limbus ; saline solution is admitted from the syringe until all air bubbles are vented around the rim. The head is then raised to the upright position with the lens held lightly against the eye to retain the saline solution. Clinical trials of this lens in conjunction with the als of this lens in conjunction with the dye laser generating a 100-kW pulse have shown that a prism of BK7 glass may be used instead of quartz without incurring radiation damage.

ACKNOWLEDGMENT

Mr. L. Yerlett assisted in the design of this lens.

REFERENCES 1. Hager, H.: Besondere mikrochirurgishe Ein­

griffe. Klin. Monatsbl. Augenheilkd. 162:437, 1973. 2. Worthen, D. M., and Wickham, M. G.: Laser

trabeculotomy in monkeys. Invest. Ophthalmol. 12:707, 1973.

3. : Argon laser trabeculotomy. Trans. Am. Acad. Ophthalmol. Otolaryngol. 78:371, 1974.

4. Teichmann, I., Teichmann, K. D., and Fech-ner, P. U. : Glaucoma operation with the argon laser. Eye Ear Nose Throat Mon. 55:58, 1976.

VOL. 91, NO. 5 NOTES, CASES, INSTRUMENTS 681

5. Ticho, U., and Zauberman, H.: Argon laser application to the angle structures in glaucoma. Arch. Ophthalmol. 94:61, 1976.

6. Wise, J. B., and Witter, S. L.: Argon laser therapy for open-angle glaucoma. Arch. Ophthalmol. 97:319, 1979.

7. Wheeler, C. B.: Laser iridectomy. Phys. Med. Biol. 22:1115, 1977.

8. Goldschmidt, C. R., and Ticho, U.: Theoretical approach to laser trabeculotomy. Med. Phys. 5:92, 1978.

9. Krasnov, M. M.: Laseropuncture of anterior chamber angle in glaucoma. Am. J. Ophthalmol. 75:674, 1973.

10. : Q-switched laser goniopuncture. Arch. Ophthalmol. 92:37, 1974.

11. Bass, M. S., Cleary, C. V., Perkins, E. S., and Wheeler, C. B.: Single treatment laser iridoto-my. Br. J. Ophthalmol. 63:29, 1979.

12. Becker, S. C : Unrecognized errors induced by present-day gonioprisms and a proposal for their elimination. Arch. Ophthalmol. 82:160, 1969.

OPHTHALMIC MINIATURE

Oh, this terrible gift of second-sight that comes to some of us when we begin to look through the silvered rings of the arcus senilis.

Oliver Wendell Holmes, The Autocrat of the Breakfast-Table Boston, Nov. 1, 1858