The relationship between cataracts and hypocalcemic tetany was established decades ago1 and clinical impressions were supported by experimental findings. Attention has also been drawn to characteristic cataractous changes occurring in the lenses of uremic patients with hypocalcemia.2 Even though there seems to be ample evidence that some sort of connection exists between hypocalcemic states and cataracts, the exact relationship has still not been established.
Our purpose is to describe the lenticular changes in a patient with several hypocalcemic episodes during his renal insufficiency and to present some thoughts concerning a possible mechanism.
Renal failure due to chronic nephritjs_was diagnosed in 1 969 inai 7-year-old male. The onset of his disease began three years before when he was hospitalized with deteriorated kidney function. The laboratory findings showed: creatinine 6 mg per 100 ml. uric acid 9 mg per 100 ml, serum calcium 7.8 mg per 100 ml, plasma inorganic phosphate 4.8 mg per 100 ml. His renal insufficiency became complicated with general hypertension. In spite of intensive treatment with oral calcium supplements, aluminium hydroxide gel, a low protein and salt free diet, the impairment of the renal function continued and the laboratory values worsened. Although no authentic osteodystrophy could be detected clinically and radiologically, the calcium balance became progressively negative- The volume of calcium in the serum dropped further from March 1 970 to November 1 971 between 6.8 mg per 100 ml to 4.8 mg per 100 ml. On the other hand, the plasma phosphorus showed a tendency to steadily rise to 10.8 mg per 100 ml. No overt signs of tetany were observed in spite of the severe hypocalcemia, probably because of the presence of the metabolic acidosis.
In November 1 971 hemodialysis was started. After two dialysis, the condition of the patient improved and 10 days later he was discharged, continuing with dialysis twice weekly. At this point he underwent an eye examination and presented normal visual acuity and clear lenses. In the right fundus, a small retinal exudate was caused by systemic hypertension. In March 1972 the patient started to complain of blurred vision and presented a visual acuity drop to RE 6/12; LE 6/9. The lenticular examination disclosed findings that were different in both eyes. In the right lens numerous discrete opacities were situated in the anterior and posterior cortex. Concomitantly scattered vacuoles were found in the same areas. These changes were more condense in the posterior pole around the pupillary a rea. containing a few iridescent crystals of blue, green, and red color. In the left lens, some fine vacuoles just beneath the anterior and posterior capsule, together with fine irregular linear subcapsular opacities, were found. Characteristic iridescent particles were situated in a narrow zone of the lens cortex. These particles seen in optical section were separated by a clear zone of discontinuity from the anterior and posterior capsules. The fetal nucleus was intact in both eyes, but a few flakes were present in the nuclear layer of the lens in the right eye.
In April 1 972, a successful renal transplant from a cadaver donor was performed and was followed by a drop to normal of creatinine (1.4 mg per 100 ml), inorganic phosphate (3.2 mg per 1 00 ml), and a rise of serum calcium (9.8 mg per 100 ml). The patient's lenticular status remained unchanged and he felt well till November 1 973 when he became febrile and presented signsof rejection. Swelling andtenderness over the allograft were followed by a reduction of urine volume, and in spite of repeated therapeutical efforts, there was worsening of hisgeneral condition. The graft was removed and the patient again started on hemodialysis. Even though careful attention was given to calcium intake and the levels of calcium in the dialyzing fluid, the serum calcium dropped to 6.2 mg per 100 ml. Further intermittent hypocalcemic periods with hyperphosphatemia occurred in the following months and the visual acuity worsened in both eyes (RE 6/18; LE 6/1 2). The lenses presented several new elongated homogenous opacities, both in the anterior and posterior cortex separated jrom the capsule by clear zones. Transparent fibers found between the old opacities and the new ones gave to the cataract a laminated appearance. The anteroposterior diameter of the lens was 4 mm. [n October 1 974t the cataract appeared as dense cortical opacities producing serious visual acuity impairment thatjed to cataract extraction by means of intracapsular techniques.
Our patient had cataracts that were indistinguishable fronvthose considered characteristic of calcium deficiency. There seems to be little doubt that the hypocalcemic instances in this case played a role in the cataract production. However, there is reason to believe that there were also other factors involved, The level of serum inorganic phosphorus might have also played role, in jhat the cataract appeared to develop in association with elevated phosphorous. As such, the possibility of an interplay between Ca and P should be born in mind in lenticular changes due to calcium deficieny.
The study of our patient was of interest not only on a purely clinical basis, but it alsogave us the opportunity to document the sequence of events. The earliest recognizable changes in the lens consisted of multiple fine vacuoles just beneath the anterior and posterior capsule. Within a few weeks, the vacuoles disappeared and were replaced by fine irregular linear subcapsular opacities. The evolution of the cataract was related to the level and duration of the hairnfuj_façtor - say hypocalcemia. It is important to note that once the calcium level was restored, the opacities gradually became separated from The capsule by the_intrusion_of new transparent lens fibers_and the cataract appeared to be laminated. Later, small punctate opacities appeared, scattered in the cortex together with iridescent crystals of various colors. The anterioposterior diameter of the lens shortened.
On the basis of earlier observations in middle-aged patients,2 such cataracts were shown to progress so rapidly that previously clear lenses underwent complete opacification within less than one year. Our patient presented lenticular changes that progressed more slowly. The patient's age seems to be an important factor for the speed of development of_this_ jsatiract. The lenses of people past middle age appear more prone to rapid clouding than the lenses of younger subjects. However, it is possible to conjecture~that the type of lens opacity is a function not only of the onset of age but also the specific metabolic make up of the individual.
Despite_a_great deal of speculaiton, many issues remain to be clarified about the pathogenesis of hypocalcemic cataract. Data have been provided concerning the metabolic defect producing the hypocalcemia and hyperphosphatemia in chronic renal failure.3 There is a suggestive evidence that hypocalcemia is mainly a result of decreased intestinal reabsorption. The parathyroid hormone and calcitonin play a central role in maintaining positive calcium balances.4 Vitamin D, through its biologically active metabolites, regulates the intestinal absorption of calcium and the responsiveness of bone to both parathyroid hormone and calcitonin. With extensive destruction of renal tissue, this biologic activity of the vitamin D is altered.5 The cataract appearance in uremia, in which a hypocalcemichyperphosphatemic state is present, cannot be attributed to a high level of parathormone or other uremic toxins. In congenital hypoparathyroidism with hypocalcemia-hyperphosphatemia, neither uremia nor the parathormone are present. But since a high calcitonin level can be found in both conditions, the secondary uremic hyperparathyroidism and congenital hypoparathyroidism, the possibility of an interplay between the calcitonin and the lenticular changes should be given primary consideration.
For those patients who have hypocalcemia during their dia lysis treatment, the possibility of cataract formation is. one additional factor that must be considered in the clinical balance of the individual patient involved. The risk of cataract appears to increase proportionally with the duration of hypocalcemia, its level, and the age of the patient involved. Awareness of this relationship will alert us to the diagnostic possibility and its future documentation.
A 19-year-old-male with advanced renal failure developed bilateral cataracts indistinguishable from those considered characteristic of calcium deficiency. The biochemical findings during the dialysis treatment showed severe hypocalcemic episodes. A hypothetical mechanism to explian this kind of cataract is mentioned.
1. Duke-Elder S: System of Ophthalmology, vol II. London, Henry Krimpton, 1969, p 177.
2. Berlyene GM, Danovitch GM, Ben-Ari J, et al: Cataracts of chronic renal failure. Lancet 1 :509, 1972.
3. Merrill JP, Hampers CL: Uremia: Progress in pathophysiology and treatment. New York, Grune & Stratton, 1971.
4. Parsons JA, Potts JT Jr. Physiology and chemistry of parathyroid hormone, in Maclntyre I (ed): Clinics in Endocrinology and Metabolism. London, Saunders, 1972, ? 33.
5. Kodicek E: Recent advances in vitamin D metabolism, in Maclntyre I (ed): Endocrinology and Metabolism. London, Saunders, 1972, p 305.